System for additive manufacturing and method related thereto

Abstract

Build arms and build platforms of systems for additive manufacturing. A build arm armature mounts to a vertically translating linear actuation system; a plurality of adjustable contact pads are attached to the armature. The adjustable contact pads are adjustable at least in their protrusion distance from the armature. In some embodiments, build arms include a holding bracket, sized to receive a connector of the build platform, and operable to move the received build platform between (1) a loose position allowing the build platform to be removed from the holding bracket, and (2) an engaged position. The engaged position brings surfaces of the contact pads of the armature into contact with contact surfaces located on the build platform within a predetermined range of forces. Contact surfaces on build platforms are arranged in complementary positions on an upper side, within tolerance-defined distances relative to the build surface on the lower side.

Description

[0001] PATENT APPLICATION

[0002] Title: SYSTEM FOR ADDITIVE MANUFACTURING AND METHOD

[0003] RELATED THERETO

[0004] RELATED APPLICATIONS

[0005] This application claims the benefit of priority of U.S. Provisional Patent Application No. 63 / 689,963 filed on September 3, 2024; the contents of which are incorporated herein by reference in their entirety.

[0006] FIELD AND BACKGROUND OF THE INVENTION

[0007] The present invention, in some embodiments thereof, relates to the field of additive manufacturing and more particularly, but not exclusively, to additive manufacturing by liquid photopolymerization.

[0008] Additive manufacturing (sometimes referred to as “three-dimensional printing” or “3D printing”) manufactures articles by incremental (typically layer-by-layer) accumulation of hardening materials of various types. Vat photopolymerization, also known as stereolithography, uses controlled exposure to light to harden layers from a liquid resin substrate. In some systems, digital light processing (DLP) is used as part of the optical system which directs light exposure to harden materials.

[0009] SUMMARY OF THE INVENTION

[0010] According to an aspect of some embodiments of the presently described subject matter, there is provided a build arm suitable for detachably mounting a build platform of a system for additive manufacturing, wherein the build arm comprises: an armature mountable onto a linear actuation system configured to controllably move the build arm along a vertical axis relative to a build window of the additive manufacturing system; a plurality of adjustable contact pads attached to the armature, the adjustable contact pads being adjustable in protrusion distance from the armature along the vertical axis; and a holding bracket, sized to receive a connector of the build platform, and operable to move the connected build platform between: a loose position allowing the build platform to be removed from the holding bracket, and an engaged position; wherein the engaged position brings surfaces of the contact pads of the armature into contact with contact surfaces located on the build platform within a predetermined range of forces. According to some embodiments of the presently described subject matter, the engaged position orients a build surface of the build platform at a contact pads relative to the build window within a parallel tolerance adjustable by adjustment of the protrusion distances of the plurality of adjustable contact pads.

[0011] According to some embodiments of the presently described subject matter, the build window is on a lower side of the armature; the build surface is positioned on the lower side of the armature when the build platform is mounted to the build arm; and at least one of the surfaces of the contact pads receives contact from a contact surface of the build platform positioned below the surfaces of the contact pads.

[0012] According to some embodiments of the presently described subject matter, the contact pads are adjusted to position at least portions of their surfaces contacting the build platform in a substantially co-planar configuration.

[0013] According to some embodiments of the presently described subject matter, the surfaces of the contact pads receive contact force from the contact surfaces located on the build platform from a direction substantially perpendicular to orientations of the surfaces of the contact pads where contacted.

[0014] According to some embodiments of the presently described subject matter, the surfaces of the contact pads comprise substantially flat regions.

[0015] According to some embodiments of the presently described subject matter, the plurality of contact pads comprise four or more contact pads.

[0016] According to some embodiments of the presently described subject matter, when the build platform is mounted to the build arm, the contact pads are each separated from each other by regions out of contact with the build platform.

[0017] According to some embodiments of the presently described subject matter, the holding bracket is operated by a rotating handle.

[0018] According to some embodiments of the presently described subject matter, the holding bracket transitions from the loose position to the engaged position upon rotation of the handle from a first position to a second position, indicated by a positive stop.

[0019] According to some embodiments of the presently described subject matter, the positive stop is reached after continuing movement of the handle beyond a position at which initial contacts occur between the surfaces of the contact pads and the contact surfaces located on the build platform when the build platform is mounted to the build arm. According to some embodiments of the presently described subject matter, the rotating handle operates a screw which moves the build platform relative to the contact pads when the build platform is mounted to the build arm.

[0020] According to some embodiments of the presently described subject matter, the holding bracket is sized and shaped to receive a connector of the build platform for mounting to the build arm.

[0021] According to some embodiments of the presently described subject matter, the holding bracket includes a side opening sized to allow a stem of the connector to protrude from the holding bracket while the connector head is held by the holding bracket.

[0022] According to some embodiments of the presently described subject matter, the holding bracket moves relative to the armature to move the build platform relative to the contact pads when the build platform is mounted to the build arm.

[0023] According to some embodiments of the presently described subject matter, the build arm is attached to the movable platform in a cantilevered configuration defining connected and reach sides of the build arm, and wherein the build platform attaches to the reach side of the build arm.

[0024] According to some embodiments of the presently described subject matter, the contact pads comprise inserts received within respective sockets of the armature.

[0025] According to some embodiments of the presently described subject matter, the build arm comprises an arrangement of one or more shims positioned within the sockets which displace the contact pads to different distances proud of the socket.

[0026] According to some embodiments of the presently described subject matter, the build arm comprises an elastic element configured to flex and absorb a portion of contact force generated in the engaged position, and maintain the contact force within the predetermined range of forces.

[0027] According to some embodiments of the presently described subject matter, the elastic element begins flexing upon contact between the contact pads of the armature and the contact surfaces located on the build platform.

[0028] According to an aspect of some embodiments of the presently described subject matter, there is provided a build platform for detachable mounting to a build arm of a system for additive manufacturing, wherein articles being built by the system for additive manufacturing are attached to a build surface of the build platform, and positioned relative to a building zone of the system for additive manufacturing by movement of the build arm, and wherein the build platform comprises: a connector configured to releasably attach the build platform to the build arm; and a body connected to the connector, the body having a lower side defining the build surface and an upper side; wherein the upper side includes a plurality of upward-facing contact surfaces elevated from the upper side and positioned to discretely contact corresponding lower- facing surfaces of contact pads of the build arm when the build platform is mounted to the build arm.

[0029] According to some embodiments of the presently described subject matter, the build surface has a width and a breadth, and the contact surfaces are distributed in positions collectively subtending at least 33% of the width and breadth.

[0030] According to some embodiments of the presently described subject matter, the contact surfaces are distributed in positions collectively subtending less than 80% of the width and breadth.

[0031] According to some embodiments of the presently described subject matter, the body comprises material extending continuously between the build surface and the contact surfaces.

[0032] According to some embodiments of the presently described subject matter, the body is formed from a single billet of the material.

[0033] According to some embodiments of the presently described subject matter, the connector is positioned on an upper side of the build platform, and extends upward to connect to the build arm when mounted to the build arm.

[0034] According to some embodiments of the presently described subject matter, the connector comprises a stem attached to the build platform leading upward to a head broader than the stem in at least one direction.

[0035] According to some embodiments of the presently described subject matter, the head includes a hole sized to receive an inserted transfer tool, and a detent within the hole which grips the transfer tool upon insertion, allowing the transfer tool to remove the build platform from the build arm upon withdrawal from the system for additive manufacturing.

[0036] According to some embodiments of the presently described subject matter, the build platform comprises a carrying handle extending from the body at one or more positions between a most upper portion of the connector and the build surface.

[0037] According to some embodiments of the presently described subject matter, an outer wall of the body includes a region which slopes inwardly between the lower and upper sides, from a first cross-section to a second cross-section at least 25% reduced in area compared to the first cross-section.

[0038] According to some embodiments of the presently described subject matter, the region slopes inwardly with a slope at least 10° oblique to horizontal on average. According to some embodiments of the presently described subject matter, the region slopes inwardly with an increasing slope above horizontal.

[0039] According to an aspect of some embodiments of the presently described subject matter, there is provided a build platform for detachable mounting to a build arm of a system for additive manufacturing, wherein articles being built by the system for additive manufacturing are attached to a build surface of the build platform, and positioned relative to a building zone of the system for additive manufacturing by movement of the build arm, and wherein the build platform comprises: a body having a lower side and an upper side, wherein the lower side defines the build surface; an outer wall of the body includes a region which slopes inwardly between the lower and upper sides along a slope at least 10° oblique to horizontal on average, for a distance of at least 25 mm.

[0040] According to an aspect of some embodiments of the presently described subject matter, there is provided a build platform for detachable mounting to a build arm of a system for additive manufacturing, wherein articles being built by the system for additive manufacturing are attached to a build surface of the build platform, and positioned relative to a building zone of the system for additive manufacturing by movement of the build arm, and wherein the build platform comprises: a body having a lower side and an upper side, wherein the lower side defines the build surface; a connector, extending upward from the upper side; and one or more carrying handles, above the build surface, and extending laterally.

[0041] According to some embodiments of the presently described subject matter, the body, connector, and carrying handle comprise separately formed components attached to each other.

[0042] According to an aspect of some embodiments of the presently described subject matter, there is provided a system for additive manufacturing comprising: an illuminating assembly comprising a digital light processing projector, positioned at least 300 mm below a building zone into which the digital light processing projector focuses light; a build window assembly comprising a build window through which the digital light processing projector focuses light within the building zone; and a plurality of suspension brackets, each comprising material formed from a single billet extending continuously between an upper side and a lower side; wherein the suspension brackets suspend the illuminating assembly below the build window assembly through attachment of their respective upper sides to the build window assembly, and of their respective lower sides to the illuminating assembly.

[0043] According to some embodiments of the presently described subject matter, the digital light processing projector is suspended on a base plate assembly, the base plate assembly comprising a plurality of alignment pins adjustable into a locked and calibrated position by adjustment of the base plate assembly, and the digital light processing projector including alignment holes sized and positioned to mate with the alignment pins.

[0044] According to an aspect of some embodiments of the presently described subject matter, there is provided a method of calibrating a system for additive manufacturing, comprising: measuring relative distances of each of a plurality of contact surfaces of adjustable contact pads of a build arm to a build window, wherein the plurality of contact surfaces are each separated from each other by surfaces of the build arm more distant from the build window; and separately adjusting the contact pads to reduce the relative distances to within a predetermined tolerance; wherein the contact surfaces are positioned to receive contacts from a detachable build platform, when the build platform is attached to the build arm.

[0045] According to some embodiments of the presently described subject matter, the method comprises attaching the detachable build platform to the build arm, tightening them into contact, and then attaching a handle to the build arm at a predetermined angle.

[0046] According to an aspect of some embodiments of the presently described subject matter, there is provided a method of attaching a build platform to a build arm of a system for additive manufacturing, the method comprising: inserting a connector head of the build platform within a holding bracket of the build arm, the connector head being interconnected with a body of the build platform defining a lower build surface of the build platform through a stem of the connector; raising the holding bracket, thereby bringing contact surfaces of a lower side of the build arm into contact with corresponding contact surfaces of an upper side of the body of the build platform; and exerting additional upward force on the holding bracket, thereby bringing mounting forces applied between the contact surfaces of the lower side of the build arm and the corresponding contact surfaces of the upper side of the body of the build platform to within a predetermined range of contact forces; wherein the exerting additional upward force also places the build surface of the build platform in a parallel relationship with a build window and building zone of the system for additive manufacturing, within a predetermined tolerance.

[0047] According to some embodiments of the presently described subject matter, the raising the holding bracket comprises turning a handle coupled to the holding bracket through a screw, and the exerting additional upward force on the holding bracket comprises turning the handle further, limited by a predetermined throw range of the handle.

[0048] According to some embodiments of the presently described subject matter, the exerting additional upward force comprises compressing a compression spring which regulates the mounting forces. Unless otherwise defined, all technical and / or scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the present disclosure pertains. Although methods and materials similar or equivalent to those described herein can be used in the practice or testing of embodiments of the present disclosure, exemplary methods and / or materials are described below. In case of conflict, the patent specification, including definitions, controls. In addition, the materials, methods, and examples are illustrative only and are not intended to be necessarily limiting.

[0049] As will be appreciated by one skilled in the art, aspects of the present disclosure may be embodied as a system, method, or computer program product. Accordingly, aspects of the present disclosure may take the form of an entirely hardware embodiment, an entirely software embodiment (including firmware, resident software, microcode, etc.) or an embodiment combining software and hardware aspects that may all generally be referred to herein as a “circuit,” “module” or “system” (e.g., a method may be implemented using “computer circuitry”). Furthermore, some embodiments of the present disclosure may take the form of a computer program product embodied in one or more computer readable medium(s) having computer readable program code embodied thereon. Implementation of the method and / or system of some embodiments of the present disclosure can involve performing and / or completing selected tasks manually, automatically, or a combination thereof. Moreover, according to actual instrumentation and equipment of some embodiments of the method and / or system of the present disclosure, several selected tasks could be implemented by hardware, by software or by firmware and / or by a combination thereof, e.g., using an operating system.

[0050] For example, hardware for performing selected tasks according to some embodiments of the present disclosure could be implemented as a chip or a circuit. As software, selected tasks according to some embodiments of the present disclosure could be implemented as a plurality of software instructions being executed by a computer using any suitable operating system. In some embodiments of the present disclosure, one or more tasks performed in method and / or by system are performed by a data processor (also referred to herein as a “digital processor”, in reference to data processors which operate using groups of digital bits), such as a computing platform for executing a plurality of instructions. Instruction executing elements of the processor may comprise, for example, one or more microprocessor chips, ASICs, and / or FPGAs. Optionally, the data processor includes a volatile memory for storing instructions and / or data and / or a non-volatile storage, for example, a magnetic hard-disk and / or removable media, for storing instructions and / or data. Optionally, a network connection is provided as well. A display and / or a user input device such as a keyboard or mouse are optionally provided as well. Any of these implementations are referred to herein more generally as instances of computer circuitry.

[0051] Any combination of one or more computer readable medium(s) may be utilized for some embodiments of the present disclosure. The computer readable medium may be a computer readable signal medium or a computer readable storage medium. A computer readable storage medium may be, for example, but not limited to, an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, or device, or any suitable combination of the foregoing. More specific examples (a non-exhaustive list) of the computer readable storage medium would include the following: an electrical connection having one or more wires, a portable computer diskette, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or Flash memory), an optical fiber, a portable compact disc read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination of the foregoing. In the context of this document, a computer readable storage medium may be any tangible medium that can contain or store a program for use by or in connection with an instruction execution system, apparatus, or device. A computer readable storage medium may also contain or store information for use by such a program, for example, data structured in the way it is recorded by the computer readable storage medium so that a computer program can access it as, for example, one or more tables, lists, arrays, data trees, and / or another data structure. Herein a computer readable storage medium which records data in a form retrievable as groups of digital bits is also referred to as a digital memory. It should be understood that a computer readable storage medium, in some embodiments, is optionally also used as a computer writable storage medium, in the case of a computer readable storage medium which is not read-only in nature, and / or in a read-only state.

[0052] Herein, a data processor is said to be “configured” to perform data processing actions insofar as it is coupled to a computer readable medium to receive instructions and / or data therefrom, process them, and / or store processing results in the same or another computer readable medium. The processing performed (optionally on the data) is specified by the instructions, with the effect that the processor operates according to the instructions. The act of processing may be referred to additionally or alternatively by one or more other terms; for example: comparing, estimating, determining, calculating, identifying, associating, storing, analyzing, selecting, and / or transforming. For example, in some embodiments, a digital processor receives instructions and data from a digital memory, processes the data according to the instructions, and / or stores processing results in the digital memory. In some embodiments, “providing” processing results comprises one or more of transmitting, storing and / or presenting processing results. Presenting optionally comprises showing on a display, indicating by sound, printing on a printout, or otherwise giving results in a form accessible to human sensory capabilities.

[0053] A computer readable signal medium may include a propagated data signal with computer readable program code embodied therein, for example, in baseband or as part of a carrier wave. Such a propagated signal may take any of a variety of forms, including, but not limited to, electro-magnetic, optical, or any suitable combination thereof. A computer readable signal medium may be any computer readable medium that is not a computer readable storage medium and that can communicate, propagate, or transport a program for use by or in connection with an instruction execution system, apparatus, or device.

[0054] Program code embodied on a computer readable medium and / or data used thereby may be transmitted using any appropriate medium, including but not limited to wireless, wireline, optical fiber cable, RF, etc., or any suitable combination of the foregoing.

[0055] Computer program code for carrying out operations for some embodiments of the present disclosure may be written in any combination of one or more programming languages, including an object-oriented programming language such as Java, Smalltalk, C++ or the like and conventional procedural programming languages, such as the “C” programming language or similar programming languages. Additionally or alternatively, sequences of logical operations (optionally logical operations corresponding to computer instructions) may be embedded in the design of an ASIC and / or in the configuration of an FPGA device. The program code may execute entirely on the user’s computer, partly on the user’s computer (e.g., as a stand-alone software package), partly on the user’s computer and partly on a remote computer or entirely on the remote computer or server. In the latter scenario, the remote computer may be connected to the user’s computer through any type of network, including a local area network (LAN) or a wide area network (WAN), or the connection may be made to an external computer (for example, through the Internet using an Internet Service Provider).

[0056] Some embodiments of the present disclosure may be described below with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems) and computer program products according to embodiments of the present disclosure. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions / acts specified in the flowchart and / or block diagram block or blocks.

[0057] These computer program instructions may also be stored in a computer readable medium that can direct a computer, other programmable data processing apparatus, or other devices to function in a particular manner, such that the instructions stored in the computer readable medium produce an article of manufacture including instructions which implement the function / act specified in the flowchart and / or block diagram block or blocks.

[0058] The computer program instructions may also be loaded onto a computer, other programmable data processing apparatus, or other devices to cause a series of operational steps to be performed on the computer, other programmable apparatus or other devices to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide processes for implementing the functions / acts specified in the flowchart and / or block diagram block or blocks.

[0059] Some of the methods described herein are generally designed only for use by a computer; and may not be feasible or practical for performing purely manually, by a human expert. A human expert who wanted to manually perform similar tasks, such inspecting obj ects, might be expected to use completely different methods, e.g., making use of expert knowledge and / or the pattern recognition capabilities of the human brain, which would be vastly more efficient than manually going through the steps of the methods described herein.

[0060] BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

[0061] Some embodiments of the present disclosure are herein described, by way of example only, with reference to the accompanying drawings. With specific reference now to the drawings in detail, it is stressed that the particulars shown are by way of example, and for purposes of illustrative discussion of embodiments of the present disclosure. In this regard, the description taken with the drawings makes apparent to those skilled in the art how embodiments of the present disclosure may be practiced.

[0062] In the drawings:

[0063] FIG. 1 schematically illustrates an additive manufacturing system, according to some embodiments of the present invention;

[0064] FIG. 2 schematically illustrates a portion of an additive manufacturing system set up for building, according to some embodiments of the present invention; FIG. 3 schematically illustrates parameters related to alignment tolerance, according to some embodiments of the present invention;

[0065] FIGs. 4A-4B schematically illustrate, respectively, front and side views of a build platform, according to some embodiments of the present invention;

[0066] FIGs. 5A-5B schematically illustrate, respectively, assembled and exploded perspective views of a build platform, according to some embodiments of the present invention;

[0067] FIG. 6 schematically illustrates a build platform as it slides into place to be connected with a build arm, according to some embodiments of the present invention;

[0068] FIG. 7A schematically illustrates an example of a calibration configuration of a build arm using a micrometer, according to some embodiments of the present invention;

[0069] FIG. 7B is a schematic flowchart of a method of calibrating parallelism of a build arm, according to some embodiments of the present invention;

[0070] FIG. 8A is a schematic flowchart of a method of calibrating mounting force of a build platform to a build arm, according to some embodiments of the present invention;

[0071] FIGs. 8B-8D schematically illustrate front horizontal views of a build platform and a build arm during their connection, according to some embodiments of the present invention;

[0072] FIGs. 8E-8G schematically illustrate views of a build arm from underneath, according to some embodiments of the present invention;

[0073] FIG. 9A schematically illustrates a partial underside view of an alternative implementation of a contact surface portion of a build arm, according to some embodiments of the present invention;

[0074] FIG. 9B schematically illustrates a cutaway view of adjustable contact pads, according to some embodiments of the present invention;

[0075] FIG. 9C schematically illustrates a partial underside view of an alternative implementation of a contact surface portion of a build arm, according to some embodiments of the present invention;

[0076] FIG. 9D schematically illustrates a cutaway view of adjustable contact pads, according to some embodiments of the present invention;

[0077] FIG. 10 schematically illustrates effects of sloping lower portions of a build platform, according to some embodiments of the present invention;

[0078] FIGs. 11A-11B schematically illustrate suspended connection of a projection system to a build window assembly, according to some embodiments of the present invention; and

[0079] FIG. 11C illustrates calibration arrangements for the suspended connection of Figs. 11A-11B, according to some embodiments of the present invention. DESCRIPTION OF SPECIFIC EMBODIMENTS OF THE INVENTION

[0080] The present invention, in some embodiments thereof, relates to the field of additive manufacturing and more particularly, but not exclusively, to additive manufacturing by liquid photopolymerization.

[0081] Overview

[0082] An aspect of some embodiments of the present invention relates to additive manufacturing systems comprising a build arm suitable for detachably mounting a build platform. In some embodiments, the build arm comprises an armature mountable onto a linear actuation system configured to vertically vary the Z-position (height) of the build arm relative to a build window of the additive manufacturing system (resulting in Z-motion).

[0083] In some embodiments, a plurality of adjustable contact pads are attached to the armature. The adjustable contact pads are adjustable at least in their protrusion distance from the armature.

[0084] In some embodiments, build arms include a holding bracket, sized to receive a connector of the build platform, and operable to move the received build platform between (1) a loose position allowing the build platform to be removed from the holding bracket, and (2) an engaged position. The engaged position brings surfaces of the contact pads of the armature into contact with contact surfaces located on the build platform within a predetermined range of forces.

[0085] The predetermined range of forces, in some embodiments, is determined by a range of motion through which the holding bracket moves between the lose position and the engaged position, and a size tolerance specification related to the connector of the build platform.

[0086] Additionally or alternatively, in some embodiments, the predetermined range of forces is limited to a maximum force set by the throw range of a lever (e.g., a lever comprising a handle). In some embodiments, transitioning from the loose position to the engaged position comprises an intermediate position in which the surfaces of the contact pads of the armature initially contact the contact surfaces located on the build platform, while the lever is partially through its total throw range.

[0087] An aspect of some embodiments of the present invention relates to build platforms for detachable mounting to a build arm of systems for additive manufacturing. In some embodiments, the articles being built by the system for additive manufacturing are attached to a build surface of the build platform, and positioned relative to a building zone of the system for additive manufacturing by movement of the build arm. In some embodiments, the build platform comprises a connector configured to releasably attach the build platform to the build arm.

[0088] In some embodiments, the body of the build platform is connected to the connector, and has a lower side defining the build surface and an upper side including a plurality of upward- facing contact surfaces. The contact surfaces are elevated from the upper side and positioned to discretely contact corresponding lower-facing surfaces of the contact pads of the build arm when the build platform is mounted to the build arm.

[0089] In some embodiments, the build platform includes one or more carrying handles, positioned above the build surface, and extending laterally.

[0090] An aspect of some embodiments of the present invention relates to systems for additive manufacturing comprising an illuminating assembly having a digital light processing projector, positioned at least 300 mm below a building zone into which the digital light processing projector focuses light. The digital light processing projector radiates light into the building zone through a build window assembly comprising a build window. Interconnecting these, in some embodiments, are a plurality of brackets, each bracket comprising material extending continuously (e.g., as formed from a continuous billet of material) between an upper side and a lower side. The brackets, in some embodiments, suspend (hang) the illuminating assembly below the build window assembly through attachment of their respective upper sides to the build window assembly, and of their respective lower sides to the illuminating assembly.

[0091] In some embodiments, the digital light processing projector is suspended on a base plate assembly. The base plate assembly, in some embodiments, comprises a plurality of alignment pins adjustable into a locked and calibrated position by adjustment of the base plate assembly. The digital light processing projector includes corresponding alignment holes sized and positioned to mate with the alignment pins. Optionally, the component assignments of the alignment holes and alignment pins are swapped; optionally, each mating component comprises at least one alignment hole and one alignment pin (each with a corresponding pin / hole on the mating component).

[0092] Before explaining at least one embodiment of the present disclosure in detail, it is to be understood that the present disclosure is not necessarily limited in its application to the details of construction and the arrangement of the components and / or methods set forth in the following description and / or illustrated in the drawings and / or given in the Examples, drawings. Features described in the current disclosure, including features of the invention, are capable of other embodiments or of being practiced or carried out in various ways. Additive Manufacturing Systems

[0093] Component Overview

[0094] Reference is now made to Fig. 7, which schematically illustrates an additive manufacturing system 10, according to some embodiments of the present invention.

[0095] Cabinet 15 houses additive manufacturing system 10, which manufactures article 5 in a sequence of layers.

[0096] In some embodiments, for example as shown in Fig. 7, build compartment 10A houses components involved in the physical handling of article 5 manufactured by additive manufacturing systems 10. Each layer is added by solidifying a fluid substrate (e.g., a liquid polymer resin), placed during article manufacture at the lower side of the article 5 (optionally a plurality of articles) currently being manufactured. In some embodiments, the fluid substrate (contained by build tray assembly 11, acting as a vat) comprises a photopolymerizing material which polymerizes in response to light (e.g., light of suitable photonic energy levels and / or intensity).

[0097] In some embodiments, at the beginning of manufacturing, the first layer of an article 5 to be built (e.g., the upper side of article 5, and / or support structures for article 5), is attached by in-contact polymerization to the build surface 412 of build platform 80. Manufacture of build article 5 then continues by adding new layers in sequence on this attachment layer. In some embodiments, for example as shown in Fig. 7, each new layer is created within the same build zone 11A, which comprises a thin volume immersed within the fluid substrate contained by build tray assembly 11. In some embodiments, build zone 11 A is substantially planar; e.g., having a height the size of a build voxel, and extending in both horizontal directions such that substantially all build voxels can be intersected by a single geometrical plane. In some embodiments, for example as shown in Fig. 7, optics compartment 10B houses an optic arrangement which creates patterns of light in build zone 11A suitable to induce polymerization in at least part of the fluid substrate contained by build tray assembly 11; for example as described in relation to Fig. 2.

[0098] During the additive manufacturing process, build platform 80 is vertically translated (undergoes Z-motion) relative to build zone 11A so that article 5 is appropriately positioned to receive each new layer. In some embodiments, this vertical translation comprises a repeated cycle of forward and backward (e.g., up and down) motions of build platform 80; for example as described in relation to Fig. 2. In some embodiments, each layer comprises portions of more than one article 5. Optionally, one or more articles 5 are built from an attachment with scaffolding (itself additively manufactured) which attaches to build surface 412 directly and / or indirectly, e.g., via one or more additional articles 5 manufactured in earlier-created layers.

[0099] In some embodiments, for example as shown in Fig. 7, components housed in build compartment 10A include Z-rail 20, build platform 80, and build arm 70. Build arm 70 is attached to Z-rail 20, and is moved up or down by a subsystem comprising one or more linear actuators.

[0100] In some embodiments, build platform 80 is removably attached to build arm 70. In some embodiments, for example as shown in Fig. 7, build platform 80 is locked to and unlocked from build arm 70 by operation of securing handle 90. Between builds, build platform 80 may be removed from build arm 70, e.g., for post-processing article 5. Optionally, build platform 80 is cleaned before being returned to position. Upon replacement of build platform 80 within additive manufacturing system 10, and / or upon installation of a different build platform 80 within additive manufacturing system 10, it is a potential advantage for build surface 412 to be dependably positioned as a result of replacement itself so that it is substantially parallel to the planar orientation of build zone 11 A; e.g., parallel through the extent of build zone 11 A with a tolerance of the size of a build voxel or less. For example, build voxels (also corresponding to the height of an individual layer) may be about 200 pm, about 100 pm, or 50 pm in height. The corresponding parallel tolerance is optionally selected to be 50 pm, 40 pm, 30 pm, 20pm, 10 pm, or another value. When the parallel tolerance is larger than the height of a build voxel, issues for initial attachment and / or manufacturing accuracy of article 5 may arise; for example, as described in relation to Fig. 3. Optionally, tolerances are similarly maintained for absolute axial positioning of build surface 412 along the axis of travel of build platform 80. However, gross displacements up or down are readily compensated by adjusting translation along Z-rail 20. The adjustments are optionally based on position measurements which are automatically determined.

[0101] The non-height dimensions of build voxels are optionally about the same as the height dimension, larger, or smaller; depending, e.g., on properties of the optics used to generate light that polymerizes fluid substrate, and / or on properties of the fluid substrate itself.

[0102] Optional display screen 12 (comprising, e.g, an LED or LCD display panel) displays status information, e.g, related to build progress, build parameters, and / or maintenance status. In some embodiments, display screen 12 is a touch screen operable as a user input device for controlling operation of additive manufacturing system 10 (e.g., to make selections from user interface displayed on display screen 12), and / or additive manufacturing system 10 is provided with one or more other user input devices operable to select information to display and / or to control operations of additive manufacturing system 10.

[0103] In some embodiments, levelling feet 17 are provided, and allow adjustment of the levelling of additive manufacturing system 10 (and, more particularly, levelling of build tray assembly 11) so that the fluid substrate is distributed evenly within build tray assembly 11.

[0104] Layer Build Cycle Example

[0105] Reference is now made to Fig. 2, which schematically illustrates a portion of additive manufacturing system 10 set up for building, according to some embodiments of the present invention.

[0106] Elements including Z-rail 20, build arm 70 and its securing handle 90, and build platform 80 are again shown, now lowered so that build surface 412 is immersed within a vat of fluid substrate 151 contained within build tray assembly 11.

[0107] In some embodiments, build tray assembly 11 comprises upper member 155, which forms a sidewall for a reservoir of fluid substrate 151 (e.g., a liquid polymer resin). In some embodiments, for example as shown in Fig. 2, upper member 155 seals against a flexible membrane 160, e.g., seals via gasket 164. As illustrated, gasket pressure is maintained by clamping flexible membrane 160 from the opposite side with lower member 156, e.g., via posts

[0108] 159, tensioning gaskets 162, and / or interstitial gasket 170. Build window 110 comprises an aperture within build window assembly 137 through which light is projected by projection system 120 into the fluid substrate 151. In some embodiments, build window 110 comprises a glass and / or quartz material which is transparent to the wavelength(s) of light used to induce solidification (e.g., photopolymerization) of fluid substrate 151.

[0109] Optics of projection system 120 bring the projected light into focus within build zone 11A, just above flexible membrane 160.

[0110] During the build cycle of a first layer of article 5 (and / or before any support layers are attached to build surface 412), build platform 80 is lowered until build surface 412 is in contact with or nearly in contact with (e.g., within) build zone 11 A, leaving a vertical gap to the upper surface of flexible membrane 160 within which build voxels can be solidified out of the resin of fluid substrate 151. After photopolymerization, the first solidified (hardened) layer created is adhered not only to build surface 412, but also to the upper surface of flexible membrane

[0111] 160. Accordingly, retracting build platform 80 tends to bring flexible membrane 160 with it. In some embodiments, for example as shown in Fig. 2, an interstitial region between flexible membrane 160 and build window 110 is pressurized before and / or during a withdrawal of build platform 80 by, for example 10-20 mm. Fluid for pressurization (optionally liquid or gas) is provided, e.g., through fluid distribution ports 140, and pressurized, e.g., by pressure regulation system 190. The layer build cycle continues with depressurization of the interstitial region and return of flexible membrane 160 to lie flat on build window 110.

[0112] The inflation / deflation cycle which accompanies withdrawal of build platform 80 assists in producing controlled detachment of the newly manufactured layer from flexible membrane 160; e.g, due to resulting deformations of flexible membrane 160, and / or controlled “peeling” of flexible membrane 160 from the newly manufactured layer. For example tension on flexible membrane 160 is potentially reduced by its inflation during withdrawal of build platform 80 so that peeling forces are relatively reduced and / or focused around the perimeter of the adhered region; then deflation allows peeling away of flexible membrane 160 to complete.

[0113] To begin the next layer build cycle, build platform 80 is lowered again. It is now lowered only until build surface 412 is positioned the height of a build voxel away from build zone 11A, so that the next build layer is added in contact with and below the first build layer. The cycle repeats until the build is complete, with build platform 80 lowering by a voxel height less on each layer build cycle in the sequence. The overall build height is optionally several hundred mm; e.g, up to 400 mm or more, depending on the dimensions of additive manufacturing system 10 overall.

[0114] Optics base plate assembly 132 is interconnected with build window assembly 137 via suspension brackets 131, for example as described in relation to Figs. 11A 11B. In some embodiments optics alignment plate 133 includes apertures sized to fittingly admit alignment pins 134, which are attached to optics base plate assembly 132. Adjustment of the positions of admit alignment pins 134 is described, for example, in relation to Fig. 12.

[0115] Also depicted in Fig. 2 are optical shrouding 122 and optical enclosure 123, which respectively enclose the region between projection system 120 and build window assembly 137, and the components of projection system 120.

[0116] Parallel Alignment Tolerances in Additive Manufacturing

[0117] Reference is now made to Fig. 3, which schematically illustrates parameters related to alignment tolerance, according to some embodiments of the present invention. The situation in Fig. 3 depicts a relatively small parallel misalignment of an upper build surface 305 (e.g., corresponding to build surface 412) and a lower build surface 307 (e.g., corresponding to an upper surface of flexible membrane 160).

[0118] The misalignment is about 0.1°; e.g, less than 1 unit of elevation per 1000 units of horizontal distance. However, this is potentially sufficient to result in a condition wherein build voxel 301 is in full contact with both of upper build surface 305 and lower build surface 307, but build voxel 302 is out of contact with upper build surface 305. For example, a vertical misalignment of about half a 50 pm build voxel height results from 25 pm of parallel misalignment over a distance of several centimeters (tens of thousands of micrometers). As a result, build voxel 302 may not come away with upper build surface 305 when it is lifted. Potentially, solidified material remains behind to interfere with subsequent layer build cycles, which may require manual intervention to clean the device.

[0119] Accordingly, it may be understood that parallel alignment of lower build surface 307 to upper build surface 305 is a significant factor is accomplishing reliable build performance of additive manufacturing system 10.

[0120] Reasons to Disturb Parallel Alignment

[0121] However — and potentially interfering with the above-described parallel alignment — serial manufacturing operations of additive manufacturing system 10 typically involve repeated mounting and dismounting of build platform 80 onto build arm 70 as each article 5 (and / or plurality of articles manufactured during a single build) are completed.

[0122] Dismounting of build platform 80 from build arm 70 may be beneficial, for example, if post-processing of article 5 is preferably performed while remaining adhered to build surface 412 (e.g., due to delicacy, and / or as a convenient pre-existing mounting). It may be easier, safer, better for manufacturing throughput, and / or otherwise preferred to remove article 5 from build surface 412 only after they are taken out from build compartment 10A. Additionally or alternatively, in some embodiments, build platform 80 requires cleaning in preparation for its next use, and / or in order to avoid cross-contamination when used with a different type of resin.

[0123] In addition, high-throughput serial production of article 5 may involve parallel stages of manufacturing and post-processing. In such a case, a first build platform 80 is dismounted from build arm 70 with a first article 5. During the time first article 5 is being transferred to a post-processing station and / or post-processed (e.g. cleaned and post-cured), a second build platform 80 is mounted onto build arm 70 to start production of a second article 5. It was found by the inventors that the present invention substantially improves accurate and high-throughput serial production of 3D printed (additively manufactured) articles, by considerably reducing or fully avoiding calibration steps when replacing build platforms.

[0124] Easing the Restoration of Parallel Alignment

[0125] Upon reattachment of build platform 80 to build arm 70, it is a potential advantage if the process of reattachment itself (that is, as distinct from optional subsequent calibration checks and / or adjustments) ordinarily ensures restoration of sufficiently parallel alignment of lower build surface 307 to upper build surface 305.

[0126] In some embodiments, this reliability applies to reattachment of any one of a plurality of different build platforms 80. Optionally, these are build platforms 80 manufactured to matching tolerances which do not depend on calibration for use with a specific additive manufacturing system 10. Optionally, these build platforms 80 are usable interchangeably among a plurality of additive manufacturing systems 10 within a manufacturing facility.

[0127] Furthermore, it is a potential advantage if the process of reattachment is suitable for both manual performance (by human operators), and automatic performance (by robotic equipment). In general, it is a potential advantage to avoid requirements to make adjustments and / or detailed inspections as part of and / or after attachment of a build platform 80 to a build arm 70. For example: insofar as there is a requirement for these elements to be precisely repositioned relative to each other, it is a potential advantage if suitable precision is ensured by the design of their connector(s). Furthermore, insofar as these elements need to be tightened against each other, it is a potential advantage if the connection mechanism(s) themselves ensure a consistent degree of tightening force is applied. It is a potential advantage if the criterion of “ensuring” should be ordinarily met when an easily assessed and / or unlikely to be mistaken operation is performed, for example, sliding two parts to a limit of relative travel, and / or moving (e.g., rotating or pushing) a control to a limit of its travel.

[0128] In particular, it is a potential advantage if no calibration measurements are ordinarily performed. However, insofar as calibration measurements are performed (and at whatever frequency), it is a potential advantage that the measurements should be equivalently performable by and / or accessible to either a human operator or a robotic operator.

[0129] It should be understood that certain conditions may produce deviations from the ordinarily expected performance of a manufacturing process. It is not excluded, for example, that some portion of an additive manufacturing systems 10 may eventually go out of calibration and / or wear to the point of needing replacement. However, it is a potential advantage if such deviations are sufficiently rare and / or exceptional that they can be avoided by occasional preventative maintenance; and / or it is at least a net savings on manufacturing costs to assume that there will usually not be such deviations, even if occasional deviations might in fact occur.

[0130] Mitigations, Causes, Conditions, and Costs of Reduced Parallel Alignment

[0131] In some embodiments, for example as shown in Fig. 3, a build failure could potentially be averted by bringing upper build surface 305 and lower build surface 307 closer together, thus reducing the height of build voxel 301. However, the resulting “squashing” of one surface may not be acceptable to the specifications of article 5 itself. This could result in a need to apply a postprocessing step of, e.g. , grinding away an initial layer (e.g. , one or more scaffolding layers) in order to bring an additively manufactured part into specification, resulting in potentially increased cost per article 5.

[0132] This “squashed pixel” approach itself reaches a limit (due to collision) once the maximum parallel alignment error exceeds the intended target voxel height, unless, for example, there is a further capability to even the misalignment out gradually through a plurality of layers (e.g., scaffolding layers). This again potentially requires post-processing to remove scaffolding and / or uneven layers.

[0133] Even before the point of potential collision, there may be problems introduced by nonparallelism due to the pressures involved in squeezing fluid resin (which tends to be highly viscous) out from between two closely approaching surfaces. For example, even under well- aligned working conditions, forces needed to bring upper build surface 305 and lower build surface 307 into a voxel-height distance may be about 700 Newtons (roughly equivalent to the standard Earth weight of 70 kg), as build platform 80 penetrates the potentially quite viscous material fluid substrate 151. High forces may recur during building of at least a portion of the subsequent layers as well. The aperture available for the escape of resin beyond the smaller surface (e.g., build surface 412) shrinks with increasingly close approximation of two surface. This can result in a need to use elevated forces to produce the same incremental closure distance.

[0134] Manufacturing may itself limit the degree of parallel tolerance which can be practically (e.g., economically) achieved. A parallel tolerance 25 pm (particularly over distances of several centimeters) is itself near to the typical limit of some less expensive high-tolerance manufacturing processes. Better tolerances (e.g., 10 pm and potentially better) can be achieved with due care and / or special techniques. This is expected to involve increased cost, however. Factors influencing tolerances that can be achieved even on well-maintained manufacturing equipment include material expansion due to heating, concurrent tool wear, cutting speeds, and / or cutting depths. Polishing may be used as part of high-tolerance manufacturing, but it may be relatively slow and / or expensive compared, e.g., to the use of cutting tooling.

[0135] It may, furthermore, be difficult to bring an additive manufacturing system 10 into tolerance by initial part assembly alone, since build arm 70 itself is a moving part relative to additive manufacturing system 10. To allow free movement, there should generally be a deliberate gap somewhere left between mechanical components which move past each other — but such a gap potentially allows play that interferes with parallel alignment.

[0136] This may be particularly present in sliding cantilever mountings (e.g., as shown in Fig. 6), wherein a build platform 80 is held by a build arm 70 supported on one side (where the sliding mount is) but free on the other; e.g., a build arm 70 that protrudes from its mounting to overhang the build area. This is also referred to herein as a “jib-mounting”. Compared, e.g., to supporting an arm at either end, cantilevered mountings have potential advantages, e.g., for reducing component count, reducing bulk / weight and / or reducing a need to coordinate actuation from either side.

[0137] Sufficient control of parallel tolerance in initial assembly of an additive manufacturing system 10 may be particularly difficult when the cantilever mounting is not largely counterweighted, and / or when it lacks stays (z.e., members that attach at one or more points along the overall overhang of build arm 70 to reduce the moment arm at the region of sliding attachment. It is a potential advantage, however, not to need counterweighting or stays.

[0138] Furthermore, there may be an interval of one or more additional components through which two components required to be parallel are attached, with each component potentially making its own contribution to parallel error.

[0139] The large ratio between overall overhang and / or travel dimensions and the tolerance requirement for parallelism should also be noted. In some embodiments, an overhang of about 200 mm or more is required to be within a 25 pm parallel tolerance or less over a distance of at least 100 mm in both horizontal directions. In some embodiments, this tolerance is to be maintained over a vertical range of travel (e.g., of build platform 80) comprising at least 100 mm. It may be noted, however, that larger overall tolerance errors which creep in gradually with increasing vertical travel are potentially more acceptable, insofar as they do not prevent a new (tilted) layer from connecting to (only slightly less tilted) the one immediately preceding it.

[0140] Again, as described above, it may be understood that a potential problem arises for maintaining specified tolerances in cases where one of the components in a parallel relationship is altematingly removed and returned to the system, and / or optionally replaced by a different component subject to the same high parallel tolerance requirements.

[0141] As also described above, it is a potential advantage to avoid having to manually recalibrate alignment under such conditions, e.g., insofar as re-calibration of manufacturing equipment results in direct or indirect costs such as reduction of production capacity, and / or a requirement for the involvement of a trained calibration technician to ensure that a system is in condition to be operated. Where an additive manufacturing system 10 is operated so that it is subject to flaws due to calibration errors, there may be costs involved in recovering an additive manufacturing system 10 to operation-ready condition after an operation fault, e.g., an operation fault resulting in a failed build.

[0142] Calibration and Calibration Stability

[0143] In some embodiments of the present invention, solutions to controlling calibration costs include any suitable combination of one or more of the following aspects.

[0144] Adjustable contact surfaces

[0145] In some embodiments of the present invention, need to achieve parallel tolerance requirements in the initially assembled state of an assembled additive manufacturing system 10 is reduced by providing that the lower contact surfaces of a build arm 70 that affect parallelism of a build surface 412 of a build platform 80 mounted to build arm 70 are adjustable in position along the axis orthogonal to the requirement-defined plane of parallelism. This allows bringing the additive manufacturing system 10 into specification by a post-assembly calibration procedure. In some embodiments, the post-assembly calibration procedure is carried out in the factory, and considered to remain generally stable thereafter, optionally excepting, e.g., scheduled maintenance or exceptional cases. It is noted that calibrating build arm 70 itself promotes interchangeability of different build platforms 80; subject, for example, to conditions such as that the build platforms 80 themselves are stable in their dimensions, and also manufactured to sufficiently high tolerance.

[0146] Protruding contact surfaces

[0147] In some embodiments of the present invention, the adjustable contact surfaces of build arm 70 comprise a contiguously constructed tilt-adjustable planar surface. However, for small tolerances (e.g., 25 pm or less) and a large planar surface (e.g., a 100 x 100 mm continuous surface or larger), it is not necessarily known without fairly comprehensive measurement where the lowest contact points of the planar surface are. Furthermore, it is a potential advantage to stability for support points to be widely spaced, e.g., to the edges of a mounting face, and / or to the corners of a generally polygonal mounting face. Accordingly, in some embodiments, designated contact surfaces of build arm 70 are explicitly raised proud of (protruding from) the rest of the side of build arm 70 which faces build platform 80 (its contact side). Protruding yields a potential advantage by reducing the surface area across which heights need to be determined; for example, according to the procedure described in relation to Figs. 7A-7B. Optionally, the protruding is by at least a distance which is assured by manufacturing tolerances, e.g., 2x manufacturing tolerances or greater. In some embodiments, the protruding distance is significantly larger, e.g., at least 1 mm, 2 mm, 3 mm, 5 mm, or another distance.

[0148] Separate adjustability

[0149] In some embodiments of the present invention, the contact surface regions are optionally provided as elements which are fully or partially separate from each other, such that adjustment of one either does not affect the other(s), or affects it slightly enough that the interaction can optionally be considered negligible. Joined-together (but still separately adjustable) contact surface regions are not excluded, however; e.g., as described in relation to Figs. 9C -9D.

[0150] Controlled contact forces

[0151] In some embodiments of the present invention, sufficiently precise and consistent parallelism of build surface 412 of a build platform 80 is established by providing a closure mechanism that ensures that contact forces developed by attachment are within some predefined range of values. For example, a securing handle 90 is provided in some embodiments with a predefined maximum throw range. It should be noted that requirements on the precision of this force (e.g., fractionally, and / or relative to what can be readily achieved as a function of distance-defined tolerances) are not necessarily as demanding as requirements of parallelism itself. Additionally or alternatively, in some embodiments, an elastic element (e.g., a compression spring) is used to absorb a portion of securing forces. As a result, there may be a relatively large accepted variance in the point of initial contact between contact pads of build arm 70 and the corresponding contact surfaces of build platform 80 (e.g., a difference of up to 100 pm in vertical travel, optionally more, compared to an attached Z-axis tolerance of, e.g., 25 pm or less).

[0152] One-piece body of the build platform

[0153] In some embodiments of the present invention, build platform 80 is constructed using a single continuous piece of material (e.g, billet aluminum) to define the critical dimensions extending between (1) contact surfaces 415 which contact build arm 70, and (2) build surface 412, including the geometrical arrangements which result in placing build surface 412 parallel to flexible membrane 160 and / or build zone 11A within specified tolerances (e.g. , 20-50 pm throughout the usable build surface; optionally smaller or larger). Regarding suitability for single-piece construction, it noted that the build platform 80 optionally has no internal moving parts, and moreover is compact compared to the overall dimensions of build window assembly 137, Z-rail 20, and build arm 70, As explained, e.g, in relation to Figs. 4A-5B, other components may be added to this one-piece body 410, optionally without the dimensions of these other components being critical to parallelism, or with their dimensions having relatively relaxed tolerance requirements compared to required parallelism tolerances.

[0154] Dimensional stability and predictability

[0155] In some embodiments of the present invention, contact surface regions of a build arm 70 are manufactured as surfaces of a material having a relatively high dimensional stability (low strain / stress ratio) and high wear resistance. Anon-limiting example of such a material is stainless steel. The higher dimensional stability may be assessed in relation, e.g, to the material of mating surfaces of build platform 80. Optionally, other structural components of build arm 70 are made using materials with greater manufacturability (softer material), e.g., aluminum. In some embodiments, stable and predictable effects of calibration adjustments are enabled by providing shim plates of well-known thickness (e.g., shim plates cut from a dimensionally stable material in sheet form having well -characterized thickness; e.g., 10 pm, 15 pm, and / or 20 pm).

[0156] Number and distribution of contact regions and / or adjustability

[0157] Embodiments of the current invention with different numbers and / or distributions of contact regions are described, e.g., in relation to Figs. 9A-9D. It may be generally noted that three points define a plane. Accordingly it may be sufficient to adjust two contact regions relative to a third, or three relative to a fourth; e.g., the most protruding contact region can be left alone (and potentially even left non-adjustable), so long as the other contact regions can be brought into appropriate alignment. Accordingly, one of the contact regions is optionally fixed. However, given protruding surface pads, there will generally be some configuration that brings three points of two opposing faces into contact, even if one or both of those faces is actually somewhat warped. With four or more planar contact points, however, minor warping is potentially flattened out, given sufficient contact force, and this offers a potential advantage for establishing and maintaining parallelism overall. Contact surface geometry

[0158] In some embodiments of the present invention, contact surfaces of build arm 70 are manufactured as substantially flat (flat within a tolerance). This provides a potential advantage insofar as it may increase the amount of surface area available for contact, with correspondingly reduced focusing of pressure on protruding areas. Flat surfaces are also relatively easy to manufacture, compared to surfaces with narrowly-specified (low- tolerance) curvatures. While there may be slight tilting of individual flat contact surfaces (e.g., when there is parallel droop in the connection of build arm 70 to Z-rail 20), any gaps introduced thereby are potentially within the manufacturing tolerances of the surfaces themselves (at least, when the surfaces are kept relatively small, e.g., within limits of about 10-20 mm in diameter). Correspondingly, seating adjustments (slight surface deformations as a result of pressure) may remain generally small compared to tolerance requirements. Potentially, surfaces stabilize quickly (are less liable to continue deforming) as total surface area in contact approaches that of the whole area available, and focal pressure is reduced.

[0159] Softer build platform contact surfaces

[0160] In some embodiments of the present invention, build platform 80 is made of aluminum or another material softer than that of the contact pads of build arm 70. Accordingly, the contact surfaces of build platform 80 are potentially more liable to undergo such modest deformations as may be induced by forces which bring the two components into contact. This helps to ensure that calibrated components on build arm 70 itself retain dimensional stability over time, and are relatively uninfluenced by different build platforms 80 which may be used with a single build arm 70.

[0161] It should be understood that contact surfaces are not necessarily placed in a coplanar arrangement; e.g., there can be deliberate offsetting (e.g., stepping) of one or more contact surfaces of build arm 70 relative to others along the vertical axis and / or differences in orientation. In such cases, build platforms 80 are manufactured to match these differences, with the result that build surface 412 itself is maintained in its appropriate parallel orientation to the build zone. However, it is a potential advantage, e.g., for ease of manufacturing and / or calibration calculations, for all contact surfaces to be nominally co-planar (within tolerances).

[0162] It should be understood that contact surfaces are not necessarily flat. For example, a spherically milled contact pad provides a potential advantage by focusing the lowest point of the surface toward the center of the contact pad, making it easy to locate. A spherical surface (or portion thereof) is also “untiltable” within practical limits. However, spherical surface manufacturing costs are potentially higher than for flat surfaces. Another example of a non-flat receiving surface is a conical surface. Where two surfaces are matched in their conical, spherical, or other non-flat geometry, force may be well-distributed; however, it may be more difficult to determine what constitutes the “low point” which should be used as a reference for calibration purposes.

[0163] It should be understood that other features of build arm 70 and / or build platform 80 described hereinbelow are also potentially related to establishing and / or maintaining sufficient parallel alignment of build surface 412 to a plane intersecting the voxels defined by build zone 11A. Features of build arm 70 and / or build platform 80 described herein below, e.g., in relation to Figs. 4A- 10B are optionally provided together with the aspects listed above in any suitable combination.

[0164] Build Platform

[0165] Reference is now made to Figs. 4A- 4B, which schematically illustrate, respectively, front and side views of a build platform 80, according to some embodiments of the present invention. Further reference is made to Figs. 5A-5B, which schematically illustrate, respectively, assembled and exploded perspective views of a build platform 80, according to some embodiments of the present invention. Except as otherwise noted, here and elsewhere in the descriptions, references to height direction (e.g., upper, lower, rising, etc.) are made with respect to the drawing orientations shown. Allowing for perspective distortions, depicted orientations generally also correspond with orientations of components in use, with fluid substrate 151 forming a reservoir of resin into which build platform 80 is dipped during a build process.

[0166] In the depicted example, build surface 412 extends along the underside of a body 410 of build platform 80. For a relatively short distance (e.g., 2-10 mm), body 410 rises from build surface 412 with an outer edge 411A substantially perpendicular to build surface 412. Optionally it is slightly raked, e.g., raked inward by 30° or less.

[0167] Above this height, body 410 insets (e.g., along curvatures 411); rapidly at first, and then more slowly as curvatures 411 orient more toward vertical. It should be noted that curvature 411 are not necessarily the same on all sides; e.g, there may be differences in depth and / or rise angle when comparing the horizontal widths and depths of body 410.

[0168] The ratio of inset to rise is discussed further, e.g., in relation to Fig. 10. Briefly: there is a potential advantage in having an inset of body 410 from the maximum horizontal extent of build surface 412, insofar as such an inset reduces changes in displacement volume as build platform 80 rises and falls within a reservoir of fluid substrate 151 such as a liquid resin. Lowered displacement volume potentially results in lowered requirements on motive force, enables greater speed, and / or reduces disturbances in the fluid substrate 151 during the build process.

[0169] The slope also helps body 410 to shed resin as it lifts out of the reservoir of fluid substrate 151, potentially making it easier to clean post-build.

[0170] Rather than narrowing directly horizontally, the slope of the inset is at least slightly vertical. A minimum verticality of this slope is determined, in some embodiments, according to a combination of the stress / strain characteristics of the material of which body 410 is constructed, and the expected forces experienced against build surface 412 as it is moved. Accordingly, near its edges, body 410 reaches its thinnest. Moving inward, a greater lever moment is exerted from the edges. Going inward, the rate at which the thickness of body 410 increases is optionally selected to counteract this effect and maintain a dimensional stability within specified tolerances. The height of outer edge 411A (and its optional rake) are optionally selected also with attention to preventing expected forces against build surface 412 from creating out-of-specification deflections of build surface 412.

[0171] In some embodiments, displacement volume is further reduced by removing material from within the region delimited by curvatures 411 (e.g., boring holes in this region). If and as appropriate, reduced strength due to removal of material may be compensated for, e.g., by adjusting the slopes of curvatures 411. It is, however, a potential advantage for ease of cleaning to maintain the integrity of the sides of body 410 without perforations.

[0172] Above the expected surface level of fluid substrate 151 during building, further minimizing the cross section of body 410 does not further affect displacement volume.

[0173] A wider top surface does, however, provide a potential advantage by increasing the surface area available for stabilization. Accordingly, contact surfaces 415 are provided as raised elements near corners at the top of body 410 (e.g., within 1-5 mm of the corner edges).

[0174] By design, and according to the precision of calibration and manufacturing methods used, specified parallelism of build surface 412 with build zone 11A results once a suitable (e.g., predetermined within a range) contact force is established between contact surfaces 415 of build platform 80 and respectively corresponding contact surfaces 615 of build arm 70 (e.g., as these are described in relation to Figs. 8E-8G). For example, the height distances between build surface 412 and contact surface 415 are specified to tolerances of about 5 pm-25 pm; e.g., a tolerance of about 10 pm. Optionally, the range of predetermined contact forces includes upper and lower bounds both within a range of about 10-100 N; or within another range, e.g., 10-200 N, 20-200 N, or 50-100 N. In some embodiments, for example as shown in Figs. 4A-5B, contact surfaces 415 are coplanar (within tolerance limits). In examples where they are optionally not coplanar (e.g., tilted and / or relatively offset in height), matching contact surfaces of build arm 70 are adjusted accordingly.

[0175] In some embodiments, the manufacture of body 410 comprises defining both build surface 412 and contact surfaces 415 by size reduction (e.g., cutting and / or polishing) from single billet of material, e.g., aluminum. For example there are no joins or breaks traversed in proceeding through body 410 from contact surface 415 at the top to build surface 412 at the bottom. Nevertheless, body 410 may be hollowed out in places, e.g., as described in relation to Fig. 5B.

[0176] Use of a single billet in manufacturing helps ensure that at least the parallelism between build surface 412 and contact surface 415 is fixed, allowing contacts (e.g., parallel contacts) established at the level of contact surface 415 to be depended on to confer (transfer) specified parallelism to build surface 412. Persons of ordinary skill in the art will understand, however, that other methods of manufacture suitable to produce the indicated relationships of parallelism and tolerances are optionally used in some embodiments of the present invention.

[0177] In some embodiments, for example as shown in Figs. 4A- 5B, build platform 80 further comprises connector 430, which serves as the primary connector of build platform 80 to build arm 70. For example, forces pressing contact surfaces 415 of build platform 80 against contact surfaces 615 of build arm 70 are exerted through connector 430; e.g., as described in relation to Figs. 8B- -8D. Optionally, connector 430 comprises a separately manufactured component attached (e.g, bolted) to body 410. Connecting hardware and connecting apertures such as threaded and / or through holes are not shown in Figs. 4A- -5B persons of ordinary skill in the art should understand how to provide them appropriately, e.g, without impairing the rigidity of build surface 412.

[0178] In some embodiments, for example as shown in Figs. 4A 5B. connector 430 comprises a stem 433, connector head 431, and an optional hollow 432 within connector head 431. Connector head 431 is wider than stem 433 across at least one horizontal direction, allowing it to be gripped from underneath and pulled upward, again as described in relation to Figs. 8B- 8D. In some embodiments, for example as shown in Figs. 4A 5B. the wider connector head 431 gives connector 430 the shape of a T-connector. It should be understood that stem 433 is strong enough to withstand the forces transmitted through it.

[0179] In some embodiments, hollow 432 provides an anchoring point into which a transfer tool can be releasably inserted and connected (e.g., via a side opening seen in Fig. 4A). The transfer tool is optionally manipulated by a human operator and / or a robotic operator. Attachment to a transfer tool provides potential advantages for moving build platform 80 in and out of connection with build arm 70 without contacting lower surfaces that are potentially coated with residue of fluid substrate 151. Optionally connector 430 also comprises an elongated aperture 433A extending along a top surface of 433, and optionally also leading into hollow 432. This can be used as a recess which accepts detents from build arm 70, and / or as access from hollow 432 to one or more internal features of build arm 70 such as a release catch.

[0180] In some embodiments, build platform 80 comprises handle plate 420, attached across the top of body 410. Handle plate 420 comprises one or more side handles 402, which optionally slope slightly downward and / or are otherwise shaped to accommodate gripping by fingers curled in underneath. Side handles 402 are also available for use by a robotic system. Optionally, handle plate 420 is exchangeable in the field for another attachment which is suited to local requirements, e.g., to accommodate connections from a custom-built robotic system which tends to operations of additive manufacturing systems 10.

[0181] It is a potential advantage to provide side handles 402 in addition to connector 430, since they allow removal of build platform 80 both without use of an additional tool and without contacting body 410 while build platform 80 is attached to build arm 70. Also, more handles 402 may be more convenient for balanced carrying once build platform 80 has been removed from build arm 70. Since handles 402 are not critically involved in the dimensions which affect connection between build arm 70 and build platform 80, they also provide a potential advantage by reducing contact wear on other components.

[0182] It should be noted that contact surfaces 415 protrude sufficiently upward from other upper surfaces of body 410 that the upper surface of handle plate 420 is relatively recessed from contact surface 415.

[0183] Calibrated Attachment to a Build Arm

[0184] Reference is now made to Fig. 6, which schematically illustrates a build platform 80 as it slides into place to be connected with build arm 70, according to some embodiments of the present invention.

[0185] Arrow 616 represents a direction of sliding attachment, in which connector 430 slides into a receiving volume 78 of holding bracket 74 (Figs. 7A and 8B- -8G illustrate these features of build arm 70 from various perspectives). Use of holding bracket 74 (e.g., instead of a direct screw-in attachment) has a potential advantage by reducing initial alignment requirements. Moreover, it provides for loosened holding configuration which does not allow build platform 80 to simply drop.

[0186] Build arm 70 is connected to Z-rail 20 at mounting plate 71 via translation bracket 21. Armature 72 is sized to provide adequate horizontal spacing from Z-rail 20 of adjustable contact pads 614 and contact surfaces 615 which they define. In particular, this spacing allows build surface 412 to dip into about the horizontal center of build tray assembly 11 above build zone 11A

[0187] It may be noted that contact surfaces 415 are slightly spaced away from contact surface 615 in the loose configuration of build arm 70 to which build platform 80 is inserted. Securing handle 90, depicted with its foreshortened free end pointing out of the plane of the drawing, is also in the loose configuration.

[0188] Additional details of attachment are described in relation to Figs. 8A-8G.

[0189] Reference is now made to Fig. 7A, which schematically illustrates an example of a calibration configuration of a build arm 70 using micrometer 701, according to some embodiments of the present invention. Further reference is made to Fig. 7B, which is a schematic flowchart of a method of calibrating parallelism of build arm 70, according to some embodiments of the present invention.

[0190] In Fig. 7A, build arm 70 has been lowered along Z-rail 20 until it is near to reference surface 703. Reference surface 703 optionally comprises the upper surface of flexible membrane 160, or another surface, e.g., a metrology plate placed upon build window 110, build window assembly 137, and / or flexible membrane 160. Optional mounting arm 702 is used to steady micrometer 701 in a vertical orientation while calibration measurements are made.

[0191] At block 710, in some embodiments, contact surface distances are measured. For example, in contact with both reference surface 703 and contact surfaces 615 of each contact pad 614 in turn, micrometer 701 is used to measure vertical distances between them. Optionally, distance measurements are relative; i.e., the distances measured are relative distances of each of contact surfaces 615 compared to the others.

[0192] At block 712, in some embodiments, the measurements from block 710 are compared to determine if the contact pads 614 currently define contact surfaces 615 in a sufficiently parallel relationship to reference surface 703. Optionally, lowest measurements for each contact pad 614 are used, on the principle that the lowest contact points are determinative of the spatial relationships in which contact surfaces 415 of build platform 80 will be held. Typically, being “in tolerance” means that all contact pad height measurements are within a tolerance distance, e.g., all of them are vertically within 25 pm of each other. If this condition is met, the flowchart is already complete. Otherwise, the flowchart continues with block 714, in which contact pads 614 are adjusted to even the distances of their lowest-measured points from reference surface 703. Optionally, this comprises lowering higher-measured contact pads 614 (particularly, but not necessarily only those which are out of specification) nearer to the vertical position of the lower-measured contact pad.

[0193] In some embodiments, this comprises the insertion of shim plates 905 (e.g., as described in relation to Fig. 8G). Where shims are used in height adjustment, adjustment resolution may be limited to steps in accordance with the shim thickness. Optionally, shims are provided in one or more thicknesses; e.g., 10 pm, 15 pm, and 20 pm. Optionally, another adjustment mechanism is used (e.g., as described in relation to Figs. 9A-9D). Depending on the vertical direction(s) in which contact pads 614 are free to move, the lowest contact pads 614 are optionally raised, and / or contact pads 614 are raised / lowered toward a more central point.

[0194] Adjustable Contact Pads

[0195] Reference is now made to Fig. 8A, which is a schematic flowchart of a method of calibrating mounting force of a build platform 80 to build arm 70, according to some embodiments of the present invention. Further reference is now made to Figs. 8B-8D, which schematically illustrate front horizontal views of build platform 80 and build arm 70 during their connection, according to some embodiments of the present invention. Reference is also made to Figs. 8E- -8G, which schematically illustrate views of build arm 70 from underneath, according to some embodiments of the present invention. In Fig. 8E, increasing height is in a direction leading into the plane of the drawing. In the isometric perspective views of Figs 8F- 8G, increasing height (e.g., in terms of the orientation of build arm 70 shown, e.g., in Fig. 7) is generally in the downward direction.

[0196] At block 810, in some embodiments, build platform 80 is inserted to holding bracket 74; for example slid into place by fitting connector head 431 into aperture 77 (Fig. 8E) and then into receiving volume 78, e.g., as described in relation to Fig. 6. In some embodiments, connector 430 is simply advanced into holding bracket 74 as far as it can go. Optionally, or alternatively, one or more detents click into place when build platform 80 is sufficiently inserted.

[0197] Fig. 8B shows features of the configuration which results, in which holding bracket 74 surrounds connector head 431 of connector 430 (within its receiving volume 78), and stem 433 protrudes downward through jaws of holding bracket 74 to connect to the rest of build platform 80. In Fig. 8C, a partial cutaway view is shown, in which holding bracket 74 can be seen supporting connector 430. Also shown in Fig. 8C are optional spring detent 76 (which helps, e.g., centering alignment of build platform 80 relative to build arm 70), and tightening screw 75. Tightening screw 75 is received by holding bracket 74, such that when tightening screw 75 turns, holding bracket 74 moves up and down. The pitch of tightening screw 75 sets the range of motion of holding bracket 74 as a function of the angle through which tightening screw 75 is rotated.

[0198] In both of these figures, build platform 80 is held loosely, with contact surfaces 415, 615 slightly separated. During the calibration procedure of Fig. 8A, securing handle 90 is optionally left unattached to build arm 70 at this point. This leaves tightening screw 75 accessible at the top of build arm 70.

[0199] At block 812, in some embodiments, tightening screw 75 is turned until contact surfaces 415, 615 come into contact. This can simply be hand turning, without the use of leverage force at this stage.

[0200] At block 814, in some embodiments, securing handle 90 is aligned to a position partially through its eventual angle of throw (e.g., position 90A of Fig. 8E), and secured into place so that it now causes tightening screw 75 to rotate when rotated itself. In some embodiments, the securing angle is about at the 7 o’clock position of a total angle of throw extending between about 3 o’clock (protruding straight out to the right), and about 9 o’clock (protruding straight out to the left; e.g., position 90B of Fig. 8E). The exact total angle of throw and exact securing position are generally not critical; the emphasis is on producing reproducibility within tolerances.

[0201] At block 816, in some embodiments, securing handle 90 is turned the rest of the way through its angle of throw, resulting, e.g., in the configuration of Fig. 8D. Now contact surfaces 415, 615 are not only in contact with each other, but also forced against each other, due to leverage exerted by securing handle 90 through tightening screw 75 (e.g., using bolt 841 of Fig. 8G, which is optionally knurled to assist non-slipping attachment of handle 90), resulting in vertically upward force being exerted through holding bracket 74, connector 430, and body 410 on contact surfaces 415.

[0202] Moreover, in some embodiments, relief is provided, for example, in the form of compression spring 842 of Fig. 8G, which prevents over-application of force. More generally, it may be understood that there are opportunities for introducing components which are elastic within a short flexing range in this system, with the result being that the height of connector 430 (e.g., height above contact surfaces 415) can optionally be manufactured to less exacting standards than those required for parallel tolerance, e.g., about 100 pm. The force exerted after securing handle 90 is locked is potentially greater or smaller depending on what exactly this height is, e.g., according to the spring constant selected for compression spring 842. However, there is in general a force within a predetermined range of forces which is applied, e.g., so long as the maximum force can be limited by additional compression of compression spring 842 as a function of shorting distance between the head of bolt 841 and holding bracket 74. Additionally or alternatively, force relief is built into build platform 80, for example, in the form of an extension spring which elongates slightly in response to force pulling connector head 431 upward. For example, an extension spring is used in the coupling of connector head 431 to body 410. There is no particular restriction on the elastic element used (whether in compression or in extension) being a dedicated spring. For example, connector head 431 itself is optionally constructed of a material which stretches through a sufficient strain distance in response to locking forces to prevent over-tightening.

[0203] In some embodiments, contact forces are regulated to tighter tolerance by calibration adjustments to connector head 431 and / or its attachment to build platform 80, e.g., by the insertion of one or more shims where connector head 431 connects with body 410, and / or by the attachment of one or more shims along under-surfaces through which holding bracket 74 exerts lifting forces.

[0204] The range of movement of securing handle 90 is optionally set by stops which it contacts at either side of its throw, or by another method, e.g., by placing pins on tightening screw 75 which limit its range of motion.

[0205] It should be noted that having a well-defined maximum throw angle for securing handle 90 means both human and robotic operators will optionally be able to secure build platform 80 to a contact pressure within the predetermined range of contact pressure forces, without having to check contact pressure itself: so long as the motion of securing handle 90 occurs while the build platform 80 is mounted to holding bracket 74, build platform 80 should be held with correct force. Optionally, a robotic operator monitors force used to operate securing handle 90 (e.g., by monitoring actuator motor current), and uses monitored force values to validate that build platform 80 is locked in place.

[0206] In the inverted view of Figs. 8E-8G, some additional details can be seen. In some embodiments, pins 801 are placed alongside the contact pads 614, and act as keys to prevent contact pads 614 from rotating. Correspondingly, contact pads 614 are partially cut away so that they each fittingly receive a portion of a pin 801.

[0207] In the exploded view of Fig. 8G, three shim plates 905 (shaped like round washers in this example) are shown as inserted underneath one of the contact pads 614. Optionally, each contact pad 614 is secured against the blind end of its respective receiving socket 843 by a fastener 842 (for example, a screw bolt). The vertical offset at which this position places contact surface 615 is optionally adjusted in shim-thickness increments by adding one or more shims between the blind end of the receiving socket 843, and the upper (proximal) end of the contact pad 614.

[0208] While shim plates 905 are optionally made to a uniform thickness, optionally, one or more shim plates is provided which is thicker on one side than the other (e.g., wedge shaped). For example, an even thickness shim plate can be ground down at a slightly oblique angle to form a taper. Optionally, such a shim plate is used to correct slight tilts in contact pads 614, potentially resulting in a more even distribution of pressure in contact with contact surfaces 415 of build platform 80.

[0209] Reference is now made to Fig. 9A, which schematically illustrates a partial underside view of an alternative implementation of a contact surface portion of a build arm 70B, according to some embodiments of the present invention. Reference is also made to Fig. 9B, which schematically illustrates a cutaway view of adjustable contact pads 914, according to some embodiments of the present invention.

[0210] The partial underside view of Fig. 9A shows an arrangement of three adjustable contact pads, distributed in a triangle across the underside surface of build arm. Build arm 70B also comprises two slots through which two stems 911 of a suitably constructed build platform is optionally admitted. The rest of the build platform is optionally constructed, e.g., as described for build arm 70. The split stem 911 illustrates how a full-width stem may be provided with a contact pad 914 positioned centrally along an edge. Additionally or alternatively, a single connector stem may be used which is not attached along the full width of a build platform 80 which attaches to build arm 70B.

[0211] As illustrated in Fig. 9B, adjustment of the vertical position of one or more of the adjustable contact pads 914 is optionally made by turning a lead screw 912. The lead screw 912 in turn adjusts the position of a sliding plate 919, which includes one or more small ramps 917 on a side facing an underside of a contact pad 914. The underside of contact pad 914 is formed so that it is gradually elevated or lowered depending on the position of sliding plate 919. Optionally, spring 918 provides restorative force (e.g., by pressing against flange 916 of contact pad 914) to ensure that contact pad 914 is held against ramps 917.

[0212] It should be understood that sliding-plate adjustment is not particularly tied to the use of three contact pads 914 (e.g., four or more are optionally provided), and it should be conversely understood that the use of three contact pad 914 is not particularly tied to the use of the ramp adjustment mechanism of Fig. 9B.

[0213] Reference is now made to Fig. 9C, which schematically illustrates a partial underside view of an alternative implementation of a contact surface portion of a build arm 70C, according to some embodiments of the present invention. Reference is also made to Fig. 9D, which schematically illustrates a cutaway view of adjustable contact pads 934, according to some embodiments of the present invention. The examples of Figs. 9A-9D provide nonlimiting alternatives, to, e.g. , the contact pad arrangements of Fig. 8G.

[0214] The partial underside view of Fig. 9C shows an arrangement of four adjustable contact pads, distributed in two pairs across the underside surface of build arm 70C, as further described in relation to Fig. 9D. Build arm 70C also comprises a single closed-ended slot which accepts stem 941 by insertion from below. Optionally, stem 941 is screwed in directly. Optionally, stem 941 comprises a T crossbar which can be locked in place by rotation to a new angle after insertion into to the oblong slot on the underside of build arm 70C.

[0215] In Fig. 9D, it may be seen that although the adjustable contact pads 934 of a pad unit 930 are linked by a connecting region 931, contact surfaces 935 are enough raised relative to connecting region 931 that each contact pad 934 is defines a substantially separate contact surface 935. Optionally, screws 937 are rotatingly captured within the body of pad unit 930, and can be operated though the underside aperture of threaded holes 938 in arm body 902 to adjust their height. For example, a wrench and / or screwdriver-receiving recess is optionally provided on the exposed side of the screws 937.

[0216] It may be understood that although changing the screw height of one side of a pad unit 930 induces a slight tilt change to both contact pads 934, the change in height will be much larger on the adjusted side, potentially leaving them independent enough to avoid iterative calibration adjustments. Nevertheless, iterative calibration adjustments are optionally performed, in some embodiments.

[0217] In some embodiments, for example as shown in Fig. 9D, contact surfaces 935 are slightly rounded. This may partially mitigate tilt changes, potentially helping to keep the region of initial contact made between build arm 70C and a build platform 80 in roughly the same horizontal location.

[0218] It should be understood that the linked-pad concept of Figs. 9C-9D is not particularly tied to the use of four contact pads 934. Optionally use of linked contact pads is mixed with the use of individual contact pads. Optionally, three or more pads are linked into a single pad unit. For example, three or four pads are provided on a linked unit. Optionally, the connecting region 931 is somewhat flexible, which potentially allows greater independence of adjustment to interconnected contact pad 934. Optionally, one of the contact pads 934 of a pad unit 930 is non-adjustable, and the other pad(s) are adjusted to accommodate it.

[0219] Similarly, a rounded contact surface 935 (e.g., as shown in Fig. 9D) is not limited to use only with the design of contact pads 934.

[0220] It is noted that in the examples described, e.g., in relation to Fig. 8G and Figs. 9A-9D, contact is made with surfaces of the build platform 80 below the surfaces of build arm 70. This has a potential advantage, since it results in forces exerted during building working in compression, in the same direction in which stability to resist contact interface movement is strongest.

[0221] It should be understood, however, that this relationship is optionally reversed. In this case other structural changes would be involved. For example, downward facing surfaces of a portion of build platform 80 inserted into build arm 70 could be pressed down upon corresponding (interior) upward-facing surfaces of build arm 70. Additionally or alternatively build platform 80 is optionally structured so that a portion of it passes from below build arm 70 upward and through it (e.g., through an open-topped mounting slot or aperture), and undersurfaces of this upper portion of build platform 80 then brought into upward-facing contact surfaces of build arm 70. It is noted, moreover, that since the major forces which the combination of build arm 70 and build platform 80 need to withstand are exerted from below, such an inverted configuration would potentially need additional contact force designed in which resists what would then act as contact-separating forces.

[0222] Inward Sloping Sides of a Build Platform

[0223] Reference is now made to FIG. 10, which schematically illustrates effects of sloping lower portions of build platform 80, according to some embodiments of the present invention.

[0224] Even if originally constructed flat and within tolerances, build surface 412 could bend during use due to the forces used to bring it into a close physical proximity to the upper surface of flexible membrane 160 and / or build window 110 (which can approach, e.g., 700 Newtons overall). To avoid this, build platform 80 is given a thickness sufficient to resist bending beyond specified tolerances. The thickness needed is different at different horizontal locations; gradual thickening toward the center helps ensure that the outer edges of build platform 80 are well- supported for longer moment arms, but not over- supported for shorter moment arms.

[0225] In particular, it is a potential advantage to avoid a material thickness much in excess of the thickness need to meet rigidity specifications (at least in the lower portions of build platform 80), since that material would contribute to a greater changing displacement volume of build platform 80 as it rises and falls (e.g., as indicated by arrow 1005) within a reservoir of fluid substrate 151. By creating an inward slope, the rise / fall distance of fluid substrate 151 (e.g., as indicated by arrow 1010) during a layer build cycle is potentially reduced. In turn, this potentially leads to decreased mechanical disturbances during building, which can potentially improve build characteristics such as geometrical uniformity and / or build speed. In some embodiments, at least 50% of the volume which would displace fluid substrate 151 if the walls of build platform 80 extended vertically upward from the edges of build surface 412 to above the surface of the reservoir of fluid substrate 151 is avoided by narrowing build platform 80 along slopes leading to a center support region (e.g., the slopes curvatures 411; optionally the slopes comprise one or more sloping diagonal surfaces).

[0226] The slope also contributes to the shedding of fluid substrate 151 as the build proceeds and build platform 80 is eventually lifted clear of the reservoir of fluid substrate 151. Fluid initially washes back and forth along slope 1016 as build platform 80 is alternately lifted and lowered. Once this region is lifted finally clear of the reservoir of fluid substrate 151, it is a potential advantage for it to shed fluid substrate 151 for the rest of the build, so that this does not have to be handled as part of the eventually removal of article 5 for post-processing.

[0227] Suspended Mounting of a Projection System

[0228] Reference is now made to FIGs. 11A-11B, which schematically illustrate suspended connection of projection system 120 to build window assembly 137, according to some embodiments of the present invention. Reference is also made to Fig. 11C, which illustrates calibration arrangements for the suspended connection of Figs. HA- 11B, according to some embodiments of the present invention.

[0229] Fig. HA illustrates a side view of one of a pair of suspension brackets 131, with schematic representations of projection system 120, optical shrouding 122, and light projection cone 1120 indicated. Fig. 11B shows the suspension assembly including suspension brackets 131 from a front-angle view, together with other major components of additive manufacturing systems 10; e.g., as described in relation to Figs. 1-2.

[0230] Suspension brackets 131 are manufactured such that the parallelism of lower bracket face 1107 and upper bracket face 1106 are within required tolerances for perpendicularity of alignment of an optical axis 1121 of projection system 120 with build window assembly 137, as well as a height (axial) distance of projection system 120 from build window assembly 137. In some embodiments, this comprises manufacture of suspension brackets 131 each from a respective single billet of material, e.g., aluminum. Accordingly, tolerance-specified distancing and parallelism of build window assembly 137 and projection system 120 are accomplished when these components are mounted directly on to suspension brackets 131. Suspension brackets 131 in effect create a calibrated ruler that transfers correct alignment to components by the act of mounting them thereto. Furthermore, suspension brackets 131 are manufactured with sturdy members (e.g., with cross-sections at least 2.5 cm in each direction), such that their dimensional stability is reliably maintained within the shipping and operating conditions specified for additive manufacturing systems 10.

[0231] The perpendicularity and axial distances are specified such that they place build zone 11 A (defined by projection system 120) where it lies parallel to and a correct distance beyond build window assembly 137 (e.g., just beyond flexible membrane 160, when assembled together with build window assembly 137). In some embodiments, suspension bracket 131 defines upper and lower apertures 1103, 1104, separated by mid-brace 1108. Separation by mid-brace 1108 is optionally used to absorb offsets and / or asymmetries between positioning constraints affecting build window assembly 137 (above) and projection system 120 (below). Optionally, spur 1109 is attachable to cabinet 15 to restrict side-to-side movements, e.g., during shipping. Optionally, the parallel faces are interrupted, which potentially reduces transfer of heat, through suspension brackets 131. For example, it may reduce heat transfer into the optics from a heated reservoir of fluid substrate 151.

[0232] In some embodiments, additional degrees of freedom are calibrated by implementing optics base plate assembly 132 as a plate assembly; for example as shown in Fig. 11C. In some embodiments, for example as shown in Figs. 11A-11B, carrier plate 132C mounts to suspension brackets 131 directly. Along one direction, X-axis plate 132A is fittingly constrained within an aperture of carrier plate 132C. Along the orthogonal direction, it can slide, until locked in place by tightening bolts 1110, which fit within slots 1101 to allow a limited range of sliding (and optionally constrain motion in the other direction). In turn, Y-axis plate 132B slides in an orthogonal direction constrained by an aperture of 132A and / or bolts 1110 within slots 1102, until those bolts 1110 are tightened. Finally, the assembly comprising projection system 120 (e.g., plate 122A and a portion of optical shrouding 122 are shown in the drawing) is attached to Y-axis plate 132B by fitting it over pins 1123, and secured into place (e.g., with bolt fasteners).

[0233] After assembly, and once projection system 120 is determined to be in its properly calibrated position, bolts 1110 can optionally be tightened permanently; e.g., glued and / or welded into place. It should be emphasized that the light projection distances involved are hundreds of millimeters (e.g., at least 300 mm; for example, 300-400 mm), to a final tolerance optionally in the range of a few dozen pm (e.g., 50-100 pm). Furthermore, the overall projection system 120 has significant mass, e.g., in the range of 5-10 kilograms (e.g., 6 kilograms). Focal length adjustments may be performed with the optics to reduce to still smaller tolerances as needed. Nevertheless, once mounting calibrations are settled, there is potentially no further need for their adjustment, even when swapping projection system 120 for a replacement: the suspension system overall including suspension brackets 131 and optics base plate assembly 132 establishes a frame of reference which is fixed, and to which replacement components can be attached without re-adjustment.

[0234] General

[0235] As used herein with reference to quantity or value, the term “about” means “within ±10% of’.

[0236] The terms “comprises”, “comprising”, “includes”, “including”, “having” and their conjugates mean: “including but not limited to”.

[0237] The term “consisting of’ means: “including and limited to”.

[0238] The term “consisting essentially of’ means that the composition, method or structure may include additional ingredients, steps and / or parts, but only if the additional ingredients, steps and / or parts do not materially alter the basic and novel characteristics of the claimed composition, method or structure.

[0239] As used herein, the singular form “a”, “an” and “the” include plural references unless the context clearly dictates otherwise. For example, the term “a compound” or “at least one compound” may include a plurality of compounds, including mixtures thereof.

[0240] The words “example” and “exemplary” are used herein to mean “serving as an example, instance or illustration”. Any embodiment described as an “example” or “exemplary” is not necessarily to be construed as preferred or advantageous over other embodiments and / or to exclude the incorporation of features from other embodiments.

[0241] The word “optionally” is used herein to mean “is provided in some embodiments and not provided in other embodiments”. Any particular embodiment of the present disclosure may include a plurality of “optional” features except insofar as such features conflict.

[0242] Throughout this application, embodiments may be presented with reference to a range format. It should be understood that the description in range format is merely for convenience and brevity and should not be construed as an inflexible limitation on the scope of descriptions of the present disclosure. Accordingly, the description of a range should be considered to have specifically disclosed all the possible subranges as well as individual numerical values within that range. For example, description of a range such as “from 1 to 6” should be considered to have specifically disclosed subranges such as “from 1 to 3”, “from 1 to 4”, “from 1 to 5”, “from 2 to 4”, “from 2 to 6”, “from 3 to 6”, etc. as well as individual numbers within that range, for example, 1, 2, 3, 4, 5, and 6. This applies regardless of the breadth of the range.

[0243] Whenever a numerical range is indicated herein (for example “10-15”, “10 to 15”, or any pair of numbers linked by these another such range indication), it is meant to include any number (fractional or integral) within the indicated range limits, including the range limits, unless the context clearly dictates otherwise. The phrases “range / ranging / ranges between” a first indicate number and a second indicate number and “range / ranging / ranges from” a first indicate number “to”, “up to”, “until” or “through” (or another such range-indicating term) a second indicate number are used herein interchangeably and are meant to include the first and second indicated numbers and all the fractional and integral numbers therebetween.

[0244] Although descriptions of the present disclosure are provided in conjunction with specific embodiments, it is evident that many alternatives, modifications and variations will be apparent to those skilled in the art. Accordingly, it is intended to embrace all such alternatives, modifications and variations that fall within the spirit and broad scope of the appended claims.

[0245] It is appreciated that certain features which are, for clarity, described in the present disclosure in the context of separate embodiments, may also be provided in combination in a single embodiment. Conversely, various features, which are, for brevity, described in the context of a single embodiment, may also be provided separately or in any suitable subcombination or as suitable in any other described embodiment of the present disclosure. Certain features described in the context of various embodiments are not to be considered essential features of those embodiments, unless the embodiment is inoperative without those elements.

[0246] It is the intent of the applicant(s) that all publications, patents and patent applications referred to in this specification are to be incorporated in their entirety by reference into the specification, to the same extent as if each individual publication, patent or patent application was specifically and individually noted when referenced that it is to be incorporated herein by reference. In addition, citation or identification of any reference in this application shall not be construed as an admission that such reference is available as prior art to the present disclosure. To the extent that section headings are used, they should not be construed as necessarily limiting. In addition, any priority document(s) of this application is / are hereby incorporated herein by reference in its / their entirety.

Claims

WHAT IS CLAIMED IS :

1. A build arm suitable for detachably mounting a build platform of a system for additive manufacturing, wherein the build arm comprises: an armature mountable onto a linear actuation system configured to controllably move the build arm along a vertical axis relative to a build window of the additive manufacturing system; a plurality of adjustable contact pads attached to the armature, the adjustable contact pads being adjustable in protrusion distance from the armature along the vertical axis; and a holding bracket, sized to receive a connector of the build platform, and operable to move the connected build platform between: a loose position allowing the build platform to be removed from the holding bracket, and an engaged position; wherein the engaged position brings surfaces of the contact pads of the armature into contact with contact surfaces located on the build platform within a predetermined range of forces.

2. The build arm of claim 1, wherein the engaged position orients a build surface of the build platform at a contact pads relative to the build window within a parallel tolerance adjustable by adjustment of the protrusion distances of the plurality of adjustable contact pads.

3. The build arm of any one of claims 1-2, wherein: the build window is on a lower side of the armature; the build surface is positioned on the lower side of the armature when the build platform is mounted to the build arm; and at least one of the surfaces of the contact pads receives contact from a contact surface of the build platform positioned below said surfaces of the contact pads.

4. The build arm of any one of claims 1-3, wherein the contact pads are adjusted to position at least portions of their surfaces contacting the build platform in a substantially co-planar configuration.

5. The build arm of any one of claims 1-4, wherein the surfaces of the contact pads receive contact force from the contact surfaces located on the build platform from a direction substantially perpendicular to orientations of the surfaces of the contact pads where contacted.

6. The build arm of any one of claims 1-5, wherein the surfaces of the contact pads comprise substantially flat regions.

7. The build arm of any one of claims 1-6, wherein the plurality of contact pads comprise four or more contact pads.

8. The build arm of any one of claims 1-7, wherein, when the build platform is mounted to the build arm, the contact pads are each separated from each other by regions out of contact with the build platform.

9. The build arm of any one of claims 1-8, wherein the holding bracket is operated by a rotating handle.

10. The build arm of claim 9, wherein the holding bracket transitions from the loose position to the engaged position upon rotation of the handle from a first position to a second position, indicated by a positive stop.

11. The build arm of claim 10, wherein the positive stop is reached after continuing movement of the handle beyond a position at which initial contacts occur between the surfaces of the contact pads and the contact surfaces located on the build platform when the build platform is mounted to the build arm.

12. The build arm of any one of claims 9-11, wherein the rotating handle operates a screw which moves the build platform relative to the contact pads when the build platform is mounted to the build arm.

13. The build arm of any one of claims 1-12, wherein the holding bracket is sized and shaped to receive a connector of the build platform for mounting to the build arm.

14. The build arm of claim 13, wherein the holding bracket includes a side opening sized to allow a stem of the connector to protrude from the holding bracket while the connector head is held by the holding bracket.

15. The build arm of claim 13, wherein the holding bracket moves relative to the armature to move the build platform relative to the contact pads when the build platform is mounted to the build arm.

16. The build arm of any one of claims 1-15, wherein the build arm is attached to the movable platform in a cantilevered configuration defining connected and reach sides of the build arm, and wherein the build platform attaches to the reach side of the build arm.

17. The build arm of any one of claims 1-16, wherein the contact pads comprise inserts received within respective sockets of the armature.

18. The build arm of claim 17, comprising an arrangement of one or more shims positioned within the sockets which displace the contact pads to different distances proud of the socket.

19. The build arm of any one of claims 1-18, comprising an elastic element configured to flex and absorb a portion of contact force generated in the engaged position, and maintain the contact force within the predetermined range of forces.

20. The build arm of claim 19, wherein the elastic element begins flexing upon contact between the contact pads of the armature and the contact surfaces located on the build platform.

21. A build platform for detachable mounting to a build arm of a system for additive manufacturing, wherein articles being built by the system for additive manufacturing are attached to a build surface of the build platform, and positioned relative to a building zone of the system for additive manufacturing by movement of the build arm, and wherein the build platform comprises: a connector configured to releasably attach the build platform to the build arm; anda body connected to the connector, the body having a lower side defining the build surface and an upper side; wherein the upper side includes a plurality of upward-facing contact surfaces elevated from the upper side and positioned to discretely contact corresponding lower-facing surfaces of contact pads of the build arm when the build platform is mounted to the build arm.

22. The build platform of claim 21, wherein the build surface has a width and a breadth, and the contact surfaces are distributed in positions collectively subtending at least 33% of the width and breadth.

23. The build platform of claim 22, wherein the contact surfaces are distributed in positions collectively subtending less than 80% of the width and breadth.

24. The build platform of any one of claims 21-23, wherein the body comprises material extending continuously between the build surface and the contact surfaces.

25. The build platform of claim 24, wherein the body is formed from a single billet of the material.

26. The build platform of any one of claims 21-25, wherein the connector is positioned on an upper side of the build platform, and extends upward to connect to the build arm when mounted to the build arm.

27. The build platform of claim 26, wherein the connector comprises a stem attached to the build platform leading upward to a head broader than the stem in at least one direction.

28. The build platform of claim 27, wherein the head includes a hole sized to receive an inserted transfer tool, and a detent within the hole which grips the transfer tool upon insertion, allowing the transfer tool to remove the build platform from the build arm upon withdrawal from the system for additive manufacturing.

29. The build platform of claim 26, comprising a carrying handle extending from the body at one or more positions between a most upper portion of the connector and the build surface.

30. The build platform of any one of claims 21-29, wherein an outer wall of the body includes a region which slopes inwardly between the lower and upper sides, from a first cross-section to a second cross-section at least 25% reduced in area compared to the first cross-section.

31. The build platform of claim 30, wherein the region slopes inwardly with a slope at least 10° oblique to horizontal on average.

32. The build platform of any one of claims 30-31, wherein the region slopes inwardly with an increasing slope above horizontal.

33. A build platform for detachable mounting to a build arm of a system for additive manufacturing, wherein articles being built by the system for additive manufacturing are attached to a build surface of the build platform, and positioned relative to a building zone of the system for additive manufacturing by movement of the build arm, and wherein the build platform comprises: a body having a lower side and an upper side, wherein the lower side defines the build surface; an outer wall of the body includes a region which slopes inwardly between the lower and upper sides along a slope at least 10° oblique to horizontal on average, for a distance of at least 25 mm.

34. A build platform for detachable mounting to a build arm of a system for additive manufacturing, wherein articles being built by the system for additive manufacturing are attached to a build surface of the build platform, and positioned relative to a building zone of the system for additive manufacturing by movement of the build arm, and wherein the build platform comprises: a body having a lower side and an upper side, wherein the lower side defines the build surface; a connector, extending upward from the upper side; andone or more carrying handles, above the build surface, and extending laterally.

35. The build platform of claim 34, wherein the body, connector, and carrying handle comprise separately formed components attached to each other.

36. A system for additive manufacturing comprising: an illuminating assembly comprising a digital light processing projector, positioned at least 300 mm below a building zone into which the digital light processing projector focuses light; a build window assembly comprising a build window through which the digital light processing projector focuses light within the building zone; and a plurality of suspension brackets, each comprising material formed from a single billet extending continuously between an upper side and a lower side; wherein the suspension brackets suspend the illuminating assembly below the build window assembly through attachment of their respective upper sides to the build window assembly, and of their respective lower sides to the illuminating assembly.

37. The system of claim 36, wherein the digital light processing projector is suspended on a base plate assembly, the base plate assembly comprising a plurality of alignment pins adjustable into a locked and calibrated position by adjustment of the base plate assembly, and the digital light processing projector including alignment holes sized and positioned to mate with the alignment pins.

38. A method of calibrating a system for additive manufacturing, comprising: measuring relative distances of each of a plurality of contact surfaces of adjustable contact pads of a build arm to a build window, wherein the plurality of contact surfaces are each separated from each other by surfaces of the build arm more distant from the build window; and separately adjusting the contact pads to reduce the relative distances to within a predetermined tolerance; wherein the contact surfaces are positioned to receive contacts from a detachable build platform, when the build platform is attached to the build arm.

39. The method of claim 38, comprising attaching the detachable build platform to the build arm, tightening them into contact, and then attaching a handle to the build arm at a predetermined angle.

40. A method of attaching a build platform to a build arm of a system for additive manufacturing, the method comprising: inserting a connector head of the build platform within a holding bracket of the build arm, the connector head being interconnected with a body of the build platform defining a lower build surface of the build platform through a stem of the connector; raising the holding bracket, thereby bringing contact surfaces of a lower side of the build arm into contact with corresponding contact surfaces of an upper side of the body of the build platform; and exerting additional upward force on the holding bracket, thereby bringing mounting forces applied between the contact surfaces of the lower side of the build arm and the corresponding contact surfaces of the upper side of the body of the build platform to within a predetermined range of contact forces; wherein the exerting additional upward force also places the build surface of the build platform in a parallel relationship with a build window and building zone of the system for additive manufacturing, within a predetermined tolerance.

41. The method of claim 40, wherein the raising the holding bracket comprises turning a handle coupled to the holding bracket through a screw, and the exerting additional upward force on the holding bracket comprises turning the handle further, limited by a predetermined throw range of the handle.

42. The method of any one of claims 40-41, wherein the exerting additional upward force comprises compressing a compression spring which regulates the mounting forces.

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