Method and system for scanning light in additive manufacturing

Abstract

A method of scanning light in additive manufacturing comprises: receiving position data describing a layer (28) of a three-dimensional object, and scanning a liquid film (17) by a beam spot (62) of a light beam (38) according to the position data to form on the film a shape (60) defining the layer. The beam spot size of the beam spot (62) is varied by selecting the beam spot size from a set of beam spot sizes so as to ensure that the beam spot size within a periphery (56) of the layer is increasing inwardly with respect to an outer contour (55) of the layer.

Description

[0001] METHOD AND SYSTEM FOR SCANNING LIGHT IN ADDITIVE MANUFACTURING

[0002] FIELD OF THE INVENTION

[0003] The present invention relates to a method of scanning light in additive manufacturing for the layer by layer formation of three-dimensional objects from a curable liquid and a system therefor. The method and system may be particularly suitable when applied to photocurable vat polymerization employing a scanning light source.

[0004] BACKGROUND

[0005] Additive manufacturing (AM) is generally a process in which a three-dimensional (3D) object is manufactured from data derived from a three-dimensional computer model of the object. Such a process is used in various fields, such as rapid manufacturing (RM), and design related fields for purposes of visualization, demonstration and mechanical prototyping. The basic operation of any AM system consists of generating layerwise control data, for example by slicing the three-dimensional object model into sequential thin cross sections, each defining a cross section or layer of the object and which include position data relevant for the AM system that is to form the object. The layerwise control data is referred to as "slices" and is provided to control equipment of the AM system to manufacture the three-dimensional object in a layerwise manner.

[0006] In vat-based AM technologies, the manufacturing of an object is performed in a vat of a viscous and optically responsive liquid resin. One type of vat-based AM is stereolithography. In stereolithography, object layers are sequentially solidified from a vat of a viscous, optically responsive, liquid resin. A precision-controlled laser, directed by a computer, sequentially scans the shape of each cross section of the object over a liquid layer adjacent to the previously formed layer according to layerwise scanning control data. During the scan, the laser energy selectively cures and solidifies the optically responsive liquid, converting it to a solidified layer.

[0007] SUMMARY OF THE INVENTION

[0008] Aspects of the invention are set out in the appended independent claims, while details of particular embodiments are set out in the appended dependent claims.According to an aspect of some embodiments of the present invention there is provided a method of scanning light in additive manufacturing. The method comprises: receiving position data describing a layer of a three-dimensional object; scanning a liquid film by a beam spot of a light beam according to the position data to form on the film a shape defining the layer; and varying a beam spot size of the beam spot, by selecting the beam spot size from a set of beam spot sizes so as to ensure that the beam spot size within a periphery of the layer is increasing inwardly with respect to an outer contour of the layer.

[0009] According to an aspect of some embodiments of the present invention there is provided a method of fabricating an object in layers by additive manufacturing. The method comprises: forming a liquid film of a liquid curable by radiation; forming a layer of the object over the liquid film by executing the method as delineated above and optionally and preferably as further detailed below; and generating a new liquid film contacting the layer in preparation for forming a subsequent layer of the object.

[0010] According to an aspect of some embodiments of the present invention there is provided a system for scanning light in additive manufacturing. The system comprises: an irradiation system configured to generate a scannable light beam to form a beam spot on a liquid film, the irradiation system being also configured to control a beam spot size of the beam spot; and a computerized controller having a circuit configured to receive position data describing a layer of a three-dimensional object, to control the irradiation system to scan the liquid film by the beam spot according to the position data to form on the liquid film a shape defining the layer, and to control the irradiation system to vary the beam spot size by selecting the beam spot size from a set of beam spot sizes so as to ensure that the beam spot size is increased within a periphery of the layer inwardly with respect to an outer contour of the layer.

[0011] According to an aspect of some embodiments of the present invention there is provided an additive manufacturing system. The system comprises: the light scanning system as delineated above and optionally and preferably as further detailed below; a vat configured to be filled with a liquid curable by radiation of the irradiation system; and a vertically movable platform configured to be immersed in the liquid.

[0012] According to an aspect of some embodiments of the present invention there is provided a method of generating scanning control data for an irradiation system of an additive manufacturing system, the irradiation system being configured to form, using a light beam, beam spots on a liquid film in accordance with a shape defining a layer of a three-dimensional object. The method comprises: receiving position data describing an inner portion and a periphery of the layer; selecting from a set of beam spot sizes a beam spot size for each beam spot so as to ensure that beam spot sizes within the periphery are increasing inwardly toward the inner portion, wherein the scanning control data for the layer comprises a plurality of beam spot sizes selected from the set; and transmitting scanning control data to a computer readable medium.

[0013] According to an aspect of some embodiments of the present invention there is provided a computer software product. The computer software product comprises a computer-readable medium in which program instructions are stored, which instructions, when read by a data processor having a circuit, cause the circuit to execute the method as delineated above and optionally and preferably as further detailed below.

[0014] 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 invention pertains. Although methods and materials similar or equivalent to those described herein can be used in the practice or testing of embodiments of the invention, exemplary methods and / or materials are described below. In case of conflict, the patent specification, including definitions, will control. In addition, the materials, methods, and examples are illustrative only and are not intended to be necessarily limiting.

[0015] Implementation of the method and / or system of embodiments of the invention can involve performing or completing selected tasks manually, automatically, or a combination thereof. Moreover, according to actual instrumentation and equipment of embodiments of the method and / or system of the invention, several selected tasks could be implemented by hardware, by software or by firmware or by a combination thereof using an operating system.

[0016] For example, hardware for performing selected tasks according to embodiments of the invention could be implemented as a chip or a circuit. As software, selected tasks according to embodiments of the invention could be implemented as a plurality of software instructions being executed by a computer using any suitable operating system. In an exemplary embodiment of the invention, one or more tasks according to exemplary embodiments of method and / or system as described herein are performed by a data processor, such as a computing platform for executing a plurality of instructions. Optionally, the data processor includes a volatile memory for storing instructions and / or data and / or a nonvolatile storage, for example, a magnetic hard-disk and / or removable media, for storinginstructions 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.

[0017] Any feature in one aspect of the disclosure may be applied to other aspects of the disclosure, in any appropriate combination. In particular, method aspects may be applied to apparatus or system aspects, and vice versa. Furthermore, features implemented in hardware may be implemented in software, and vice versa. Any system or apparatus feature as described herein may also be provided as a method feature, and vice versa. System and / or apparatus aspects described functionally (including means plus function features) may be expressed alternatively in terms of their corresponding structure, such as a suitably programmed processor and associated memory. It should also be appreciated that particular combinations of the various features described and defined in any aspects of the disclosure can be implemented and / or supplied and / or used independently. The disclosure also provides computer programs and computer program products comprising software code adapted, when executed on a data processing apparatus, to perform any of the methods and / or for embodying any of the apparatus and system features described herein, including any or all of the component steps of any method. The disclosure also provides a computer or computing system (including networked or distributed systems) having an operating system which supports a computer program for carrying out any of the methods described herein and / or for embodying any of the apparatus or system features described herein. The disclosure also provides a signal carrying any one or more of the computer programs aforesaid.

[0018] BRIEF DESCRIPTION OF THE VARIOUS VIEWS OF THE DRAWINGS

[0019] Embodiments of the invention 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 invention. In this regard, the description taken with the drawings makes apparent to those skilled in the art how embodiments of the invention may be practiced.

[0020] FIG. 1 is a schematic cross section illustration of a scanning light additive manufacturing system according to embodiments of the present invention;

[0021] FIG. 2 is a schematic illustration showing atop view of an example layer of an object, according to embodiments of the present invention;FIG. 3A is a magnified view of border paths within a periphery of the layer of FIG.

[0022] 2;

[0023] FIG. 3B is a variant of Fig. 3 A;

[0024] FIG. 4 is a schematic illustration of a portion of a periphery formed of the borders of FIG. 3B, illustrating a gradually increasing light spot size along the inward direction according to embodiments of the present invention;

[0025] FIG. 5 is a schematic illustration of a magnified view of beam spot sizes across a layer formed using the variant of FIG. 3B according to embodiments of the present invention;

[0026] FIG. 6 is a graph illustrating energy density (in mJ / cm2) delivered by a series of light spots to the liquid surface and the resulting cure depth (in mm) as a function of a position along an inward direction from the periphery to the inner portion according to embodiments of the invention;

[0027] FIG. 7 is a schematic illustration of a graphical user interface (GUI), according to embodiments of the present invention;

[0028] FIG. 8A is a flowchart diagram of a method suitable for scanning light in additive manufacturing, according to embodiments of the present invention;

[0029] FIG. 8B is a flowchart diagram of a variant method suitable for scanning light in additive manufacturing, according to embodiments of the present invention;

[0030] FIGs. 9A-C are images of formed objects obtained in an experiment performed according to embodiments of the present invention;

[0031] FIGs. 9D-E are images of comparative formed objects obtained in another experiment performed according to embodiments of the present invention; and

[0032] FIG. 10 is a graph comparative to FIG. 6, illustrating energy density and cure depth calculated according to embodiments of the invention.

[0033] In the Figures, like elements are indicated by like reference numerals throughout.

[0034] DESCRIPTION OF SPECIFIC EMBODIMENTS OF THE INVENTION

[0035] The present invention relates to a method of scanning light in additive manufacturing for the layer by layer formation of three-dimensional objects from a curable liquid and a system therefor. The method and system may be particularly suitable when applied to photocurable vat polymerization employing a scanning light source.

[0036] Even though light scanning additive manufacturing is widely practiced and has become a routine technique throughout the world, it is not without certain operativelimitations that would best be avoided. For example, the Inventor found that conventional light scanning additive manufacturing suffers from unsatisfactory surface finish, especially when high quality objects are to be formed. The Inventor therefore realized that improvements in this technology are needed, and devised a method and system for scanning light additive manufacturing devoid of many limitations possessed by conventional light scanning additive manufacturing technologies.

[0037] Referring now to the drawings, FIG. 1 is a schematic illustration of Additive Manufacturing (AM) system 10 according to embodiments of the present invention. System 10 is capable of forming a layered object 12. System 10 comprises a vat 14 filled with a liquid material 16. As shown, a liquid film 17 is formed close to the upper surface of liquid material 16.

[0038] While the embodiments herein are described with a particular emphasis to stereolithographic technology, it is to be understood that the present embodiments contemplate also other vat-based AM technologies. System 10 can employ any type of vat-based AM technology in which a layer is formed from photocurable material using light scanning, such as tracing the top surface 18 of upper film 17 from above (referred to herein as “top down” additive manufacturing). System 10 can also employ a so-called “bottom up” additive manufacturing, in which the liquid film 17 is formed near the vaf s floor, so that at the start a layer of the object is formed near the vafs floor, and then new liquid film 17 is formed beneath the previously formed layer in preparation for the forming of the next layer, so that the layers of the object are formed one beneath the other. Herein, the system and method according to embodiments of the invention will be illustrated in a non-limiting manner and for simplicity primarily with reference to “top down” additive manufacturing. The skilled person, provided with the information described herein, would readily know how to adapt it to practice bottom up additive manufacturing.

[0039] Liquid material 16 is typically of relatively high viscosity (e.g, hundreds or thousands of mPa s). Liquid material 16 is curable by radiation applied by a scanning light source 34, where any reference to “light” herein is intended to mean radiation of a wavelength suitable to photopolymerize or cure the liquid material 16. Typically, liquid material 16 is a formulation comprising one or more polymerizable components. Such a formulation optionally and preferably comprises an initiator that initiates or catalyzes a chemical reaction upon exposure to radiation. The formulation can also comprise additivessuch as, but not limited to, a photoinitiator, a thermal initiator, a polymerization catalyst, a surfactant, a dispersant, a viscosity modifier, a pigment, a dye, a surface-active compound, a filler, particles, binders, or any combination thereof. The viscosity of liquid material 16 at room temperature (e.g, 25 °C) is typically from about 100 mPa-s to about 3500 mPa-s, e.g, about 800 mPa-s. The temperature of liquid material 16 during the operation of system 10 can be from about 20 °C to about 60 °C, e.g, about 25 °C or about 35 °C or about 45 °C.

[0040] Liquid material 16 may comprise one or more photopolymerizable components, and a photoinitiator that initiates or catalyzes a photochemical reaction upon exposure to light. For example, liquid material 16 can be a UV-curable material curable by ultraviolet light. Other types of photocurable materials are also contemplated as being suitable for use in system 10.

[0041] Representative examples of polymerizable components suitable for the present embodiments include, without limitation, a methacrylate monomer, an acrylate monomer, a thiol monomer, an allyl ether monomer, a vinyl acetate derivative monomer, a styrene monomer, a vinyl ether monomer, a vinyl chloride monomer, an acrylonitrile monomer, a vinyl silane monomer, a butadiene monomer, a norbomene, a maleate monomer, a fumarate monomer, an epoxide monomer, an anhydride monomer, a hydroxyl monomer, and any combinations thereof.

[0042] System 10 also comprises a support platform 20 having a platform surface 21 on which object 12 is formed. Surface 21 is preferably horizontal with respect to the direction of gravity (the z direction, in FIG. 1). The bottommost layer of object 12 can be formed on the surface 21 of platform 20, and each further layer is formed on top of the preceding layer, as illustrated in FIG. 1, which shows a formation state at which a plurality of layers 26 of object 12 has been formed, of which the uppermost layer 28 is the most newly formed layer.

[0043] Platform 20 is immersed in liquid 16. To form each new layer, the vertical distance between the surface 21 of platform 20 and the surface 18 of curable liquid 16 is increased by lowering platform 20 deeper into the vat while keeping vat 14 at a fixed height above ground. In alternative embodiments, the vat 14 may be raised relative to the platform 20 while keeping platform 20 at a fixed height above ground, and / or by increasing the amount of liquid 16 in vat 14 to raise the liquid level within the vat. In the representative illustration of FIG.

[0044] 1, which is not to be considered as limiting, platform 20 is movable in the vertical direction z by means of a vertical motion mechanism 22, as shown by arrow 24. The vertical distancebetween the surface 18 of liquid 16 and the top surface of layer 28 may be at least the thickness of a single layer of object 12 (e.g, the thickness of layer 28). In embodiments of the present invention the platform 20 is lowered further, so that the vertical distance between surface 18 of liquid 16 and the top surface of layer 28 is more than the thickness of a single layer (e.g, more than the thickness of layer 28, as will be explained below).

[0045] System 10 also comprises a scanning control system 54, including light source 34.

[0046] Light source 34 is configured to generate a light beam 38, such as a laser beam, and is positioned above vat 14 in a manner that allows it to apply light beam 38 to surface 18 of liquid 16. The scanning control system 54 is equipped with a light handling mechanism 40 which controls the properties and position of the light beam 38 before it interacts with liquid 16. The light handling mechanism 40 comprises a scanning mechanism configured to vary the direction of the beam, as illustrated by arrow 42, and therefore the position at which it falls onto the liquid surface.

[0047] The intersection of the beam with the liquid surface will herein be referred to as a “beam spot,” and is defined as a locus of all points within the intersection of the beam with the liquid surface at which the optical intensity delivered to the liquid surface by the light beam is no less than 1 / e2of the maximum optical intensity delivered to the liquid surface by the light beam, e being Euler’s constant.

[0048] The scanning mechanism may comprise for example a mechanism such as a robotic arm that moves the light source 34 to scan the beam spot position over the liquid surface, and / or one or more rotatable mirrors and a galvanometer configured to change the angle and / or rotation of one of the mirrors, as is known in the art, and is capable of scanning surface 18 with light beam 38 along a defined path.

[0049] The wavelength of the light generated by light source 34 is chosen such that it causes the liquid to cure, and preferably matches the wavelength that induces curing of liquid 16.

[0050] For example, when liquid 16 is a UV-curable liquid, the wavelength of the light is in the ultraviolet or visible range (e.g, from about 100 nm to about 450 nm). In an example embodiment, light source 34 produces a coherent beam of light. For example, light source 34 may be a laser in which case light beam 38 is a laser beam.

[0051] Scanning control system 54 further comprises a controller 36 which has a circuit 37 configured to control light source 34 and light handling system 40, and may optionally and preferably also control various other elements of system 10 to execute various operations as described herein in order to fabricate object 12. For example, circuit 37 can be configured tocontrol the vertical distance between platform surface 21 and liquid surface 18 as described herein.

[0052] Controller 36 can communicate with a host computer 50 which can transmit to controller 36 digital data pertaining to fabrication instructions based on computer object data, e.g, in a form of a Standard Tessellation Language (STL) or a StereoLithography Contour (SLC) format, an OBJ File format (OBJ), a 3D Manufacturing Format (3MF), Virtual Reality Modeling Language (VRML), Additive Manufacturing File (AMF) format, Drawing Exchange Format (DXF), Polygon File Format (PLY), or any other format suitable for Computer-Aided Design (CAD).

[0053] The computer object data is typically in the form of graphic elements (e.g., a mesh of polygons, non-uniform rational basis splines, etc.) defining a surface of the object. The graphic elements can be processed by computer 50 which employs software known as "a slicer" that transforms the graphic elements to a grid of voxels that define the internal shape of the object, and that are arranged as a plurality of slices, each comprising a plurality of voxels describing a layer of the 3D object. Computer 50 can transmit each slice to controller 36 as two-dimensional position data. Computer 50 can be configured to transfer all the data to the controller before the additive manufacturing process begins, or to initially transfer only a portion of the data, and continue transferring during the additive manufacturing process, e.g., upon a request from the controller 36. For example, computer 50 can be configured to transmit the data on a slice-by-slice basis, or in batches of two or more slices at a time.

[0054] For clarity of presentation, communication lines between controller 36 and elements of system 10 other than host computer 50 and light handling mechanism 40 are not shown in FIG. 1.

[0055] Based on the received position data that describe a particular layer of object 12, circuit 37 of controller 36 controls light source 34 and light handling system 40 to convert a portion of liquid film 17 of curable liquid 16 above surface 21 of platform 20 into a solid shape defining the particular object layer. Circuit 37 of controller 36 controls irradiation system 34 to scan surface 18 along patterns 60 (not shown in FIG. 1, see FIG. 2 described below) which collectively form the shape.

[0056] Various characteristics of light beam 38 may be controlled by controller 36, such as the size of the beam spot on the liquid surface, and the energy density applied by the beam spot to surface 18. Controller 36 also controls the motion characteristics of the beam spot from light source 34 including the paths traced thereby and the speed at which the beam spottraces along a specified path. In preferred embodiments of the invention, at least the size of the beam spot on the liquid surface, and optionally and preferably one or more other characteristics of the beam, is / are varied during scanning.

[0057] Herein, the "size" of the beam spot is defined as the average diameter of the shape of the beam spot. Given a shape of the beam spot, as defined above, the ordinarily skilled person would know how to determine its average diameter. For example, when the beam spot is circular, the size of the beam spot is the diameter of the circle, when the beam spot is an ellipse, the size of the beam spot is half the sum of the major axis and minor axis of the ellipse, etc.

[0058] The beam spot size may be varied by controlling the handling system 40 to focus and defocus light beam 38 according to a desired spot size. When light beam 38 is focused by handling system 40, it converges toward a focal point at a focal plane of the handling system 40. The position of the focal plane relative to the surface 18 of liquid 16 determines the spot size of the beam on surface 18, in a manner that the spot size is increased with the distance between the focal plane and liquid surface 18. Thus, the smallest spot size is achieved when the focal plane of handling system 40 is incident with liquid surface 18, and larger spot sizes are achieved when the focal plane of handling system 40 is away from the liquid surface.

[0059] Any one or more lenses may be employed by light handling system 40 to direct and / or control characteristics of the beam, such as but not limited to, one or more aspheric lenses, spherical lenses, concave lenses, convex lenses, F theta lenses, telecentric lenses, flat field lenses, curved field lenses, a Gradient Index Lens (GRIN Lens), or combinations thereof. It will be appreciated that, in practice, any “lens” referred to herein may be implemented as multiple discrete components and as such any disclosure relating to a “lens” should not be construed as being limited to a single optical component. Other light control elements such as, but not limited to, a shutter, a spatial modulator, or a reflector, can also be used, if desired.

[0060] FIG. 2 is a schematic representation of a top view of layer 28, the shape of which being formed by patterns 60, along which irradiation system 34 scans the surface 18 of liquid 16. The present embodiments contemplate more than one type of pattern.

[0061] One type of pattern is a non-straight pattern generally shown at 64. This pattern includes a collection of non-straight border paths 64-1, 64-2, 64-3, etc., which can be polyline or curvilinear paths, and which are optionally and preferably closed border paths. For clarity of presentation, FIG. 2 illustrates paths 64-1, 64-2, 64-3 as polylines, but it is to be understood that this type of pattern may instead or in addition include curvilinear borderpaths. A representative example of an embodiment in which border paths 64-1, 64-2, 64-3, etc. are curvilinear is illustrated in FIG. 4 described below.

[0062] Another type of pattern is a hatching pattern generally shown at 57. This type of pattern is a collection of straight lines, optionally and preferably arranged in two or more sets of parallel straight lines where the lines of one set 57a of parallel lines intersect the lines of the other set 57b of parallel lines. Also contemplated are embodiments in which the hatching pattern includes only one set of parallel straight lines, and embodiments in which the hatching pattern includes a plurality of straight lines each along a random direction.

[0063] Typically, the non-straight pattern 64 forms a periphery 56 of layer 28 and the hatching pattern 57 forms an inner portion 58 of the object layer, where inner portion 58 is at least partially, and more preferably completely, enclosed by periphery 56. The polyline or curvilinear border paths 64-1, 64-2, 64-3, etc, of non-straight patterns 64 are interchangeably referred to herein as "border paths" or simply "borders" which form periphery 56.

[0064] In response to a control signal from controller 36, light handling system 40 handles light source 34 to trace periphery 56 of layer 28 along two or more border paths 64. The two or more border paths 64 are extending along and within the outer contour of the layer, wherein an outermost border 64-1 is formed with a smaller beam spot size compared to inner borders 64-2, 64-3. The two or more border paths 64-1, 64-2, and 64-3 defining the periphery 56 are formed as a set of consecutive, preferably non-intersecting, curvilinear and / or polyline paths that extend substantially side-by-side to one another. Inner portion 58 of layer 28, which is at least partially enclosed by the periphery 56 formed by the border paths 64 as delineated by dot-dashed line 53, is solidified by a beam spot size that is preferably the same or larger than the beam spot size forming the innermost border.

[0065] Inner portion 58 can be formed as a cross-hatch pattern where the beam spot 62 of beam 38 traces first set of parallel linear inner portion paths 57a, and also second set of parallel linear inner portion paths 57b. The linear inner portion paths 57a of the first set and the linear inner portion paths 57b of the second set are angled, optionally perpendicular, to each other. A hatching pattern formed by linear paths that are perpendicular, to each other is referred to herein as a cross-hatch pattern. Preferably, but not necessarily, the inner portion 58 is completed before the periphery. Alternatively, the border paths 64 may be completed before the inner portion paths of the inner portion 58. The spot size of the beam used to form inner portion 58 may be the largest beam size applied to the periphery 56, or it may be larger than the spot size of the largest beam spot applied to the periphery 56. Inner portion paths57a, 57b in the inner portion 58 may be spaced apart at a larger distance from one another compared to the distances between the borders 64.

[0066] The inventor experimentally demonstrated that including a plurality of borders 64 in periphery 56 achieves an improvement in the outer surface quality of the object. By way of example, FIG. 2 illustrates three border paths 64-1, 64-2, 64-3, but any suitable number of two or more may be applied to achieve such an improvement in the outer surface quality of the object. The three borders formed by beam spots are illustrated further in FIG. 3 A, which is a schematic illustration showing a view of a close up of three example beam spots: an outer beam spot 62-1 forming outer border 64-1 of periphery 56, an inner beam spot 62-3 forming inner border 64-3 of periphery 56, and an intermediate beam spot 62-2 forming intermediate border 64-2 between the outer border 64-1 and inner border 64-3. As shown the beam spot sizes increase from the outer border 64-1 to the inner border 64-3, inwardly with respect to an outer contour of said layer and towards the inner portion 58. The inner portion 58 as shown is formed along a set of inner portion paths 57 which optionally describe a cross-hatch pattern. Preferably, the beam spots overlap, such that the centers of adjacent beams spots are closer to one another than the sum of the radii of the (in this case, by way of example) circular spots. Preferred degrees of overlap and the resulting separations si, s2 will be discussed in more detail below. In general, the embodiments according to the invention result in a more uniform energy density across the periphery, and preferably also across the inner portion and with a generally smooth transition between periphery 56 and inner portion 58 on the outer surface (e.g., the topmost layer) of the object. Preferably, the transition is not visible to a naked eye.

[0067] While the schematic illustrations in FIGs. 2 and 3A show three borders 64 within the periphery 56, this need not necessarily be the case, since, for some applications, it may be desired to employ a different number of borders within periphery 56. FIG. 3B illustrates a variant of the embodiment illustrated in FIG. 3A in which the periphery 56 is formed by five borders, following the description above, and such that three intermediate borders formed by beams spots 62-2, 62-3, 62-3 he between the outer border formed by outer beam spot 62-1 and the inner border formed by inner beam spot 62-5. The beam spot size increases monotonically from the outer border to the inner border, wherein the additional intermediate borders provide an improved transition in beam spot sizes, resulting in a more uniform total energy density across the periphery.FIGs. 3 A and 3B illustrate the beam spots in the form of circular areas. However, this is not necessary. The area or size of the beam falling onto the layer may have a shape other than circular, depending on the profile of light beam 38, specifically the shape of the crosssection of the beam's waist, and the angle between the beam and the liquid surface.

[0068] As shown in FIG. 2, the center line of the outer border 64-1 does not coincide with the location of the outer contour 55 of the layer 28. The borders are illustrated in FIG. 2 as center lines, and do not illustrate the effective widths of the borders. The effective widths of the borders may be illustrated by the beam spots as shown in FIGs. 3A and 3B. The contour 55 is along the farthest points outwards of the object layer of all the beam spots that form the outermost border.

[0069] In embodiments of the present invention circuit 37 of controller 36 is configured to control light handling system 40 to vary the beam spot size of light beam 38 such that the sizes of the beam spots are increased from one border to the next, from the outermost border inwardly with respect to layer 28. The controller 36 may select a suitable spot size for each border, from a set of spot sizes, so that the larger spot size of the set is selected for areas that are closer to the inner portion 58 of layer 28. The selection of gradually increasing spot size from the outer border to the inner border generates a lay er in which the periphery 56 is formed of several adjacent borders, wherein the outermost border is formed using the smallest beam spot size and the innermost border is formed by the largest beam spot size in the periphery 56. The inventor found that such a construction provides the layer with an improved accuracy and visual quality

[0070] FIG. 4 illustrates a portion of periphery 56 being formed of such multiple, e.g. two or more, partially overlapping beam spots of borders 64-1, 64-2, etc., by a beam spot that is gradually increasing in size from border to border (by using a larger beam spot size from one border to the next) along the inward direction 66, from the periphery 56 towards the inner portion 58, whereby the outermost border 64-1 of periphery 56 is formed by applying the smallest illuminated spot size 62-1, the next-to-outermost border 64-2 of periphery 56 is formed of the next-to-smallest illuminated spot size 62-2, and so on.

[0071] In the schematic illustrations shown in FIGs. 3B and 4, which are not to be considered as limiting, adjacent beam spots 62-1, 62-2, 62-3, 62-4 and 62-5 of five corresponding border paths 64-1, 64-2, 64-3, 64-4 and 64-5 are shown. The five border paths define the periphery 56 and extend side-by-side alongside one another, as illustrated in FIG. 4. A gradual increment of the beam spot size of the beam spots 62 from border to border inwardly overthe layer periphery (e.g. defined by a gradual increase in beam spot size from the outer contour of the layer toward the inner portion 58) is achieved using five different spot sizes. It is to be understood that the present embodiments contemplate use of any number of different beam spot sizes, e.g., 2, 3, 4, 5, 6, 7, 8, 9, 10 or more different beam spot sizes, for the borders 64 of the periphery 56. The increment in the beam spot sizes within the periphery 56 can be according to any monotonic function. In embodiments of the present invention the increment is according to a monotonic linear function, but may additionally or instead be according to a monotonic non-linear function. In experiments performed by the Inventor, a monotonic linear function was employed, so that the difference in size between, e.g, beam spots 62-2 and beam spots 62-1, was the same as the difference between, e.g, beam spots 62-3 and beam spots 62-2. Typical values for the sizes of the beam spots in the periphery 56 of layer 28 include, without limitation, sizes ranging from about 100 pm to about 400 pm.

[0072] Referring now to the inner portion 58 of layer 28, computerized controller 36 also selects one or more additional sizes for the beam spots to form patterns (e.g., patterns 57) which are within inner portion 58. During the scanning of the beam spot of light beam 38 at locations that are within inner portion 58, the size of the beam spot may remain constant without variation, i.e. in these embodiments the entire inner portion 58 is formed using a beam spot of the same size. Preferably the size of the beam spot within inner portion 58 is larger than the largest size, of the beam spot forming the periphery, e.g., in FIG. 4. larger than the size of beam spot 62-5 for the inner border within periphery 56. Thus, in these embodiments, the size of the beam spots that form layer 28 are gradually increasing in size from border to border along the inward direction 66 within the periphery 56, but not within the inner portion 58 where they may be the same or a larger than the largest beam spot of the periphery 56. An illustration of these embodiments is shown in FIG. 5, which is a magnified view of an end-to-end section line 68 across layer 28 indicated in FIG. 2 and applying the five spot sizes to consecutive borders as shown in FIGs. 3B and 4. Typical values for the sizes of the beam spots of the illuminated areas in the inner portion 58 of layer 28 include, without limitation, sizes ranging from about 200 pm to about 500 pm.

[0073] The Inventor discovered that the formation of a layer by a gradual increment of the beam spot size inwardly within the periphery resulted in a significant accuracy and quality improvement at unexpectedly low expense of additional fabrication time. This was determined from three fabrication scenarios that will now be described.In a first fabrication scenario, an object was manufactured using a relatively large spot size (about 250 pm in spot size of a laser source) for the beam spots throughout the layers of the object. While the fabrication process was the fastest of the three, the resulting first object had poor feature resolution and poor surface finish.

[0074] In a second fabrication scenario, the same object was manufactured using a smaller, non-varying, beam spot size for the periphery compared to the first fabrication scenario (about 150 pm in spot size of the laser source) and for the inner portion of the layer the same beam spot size as for the first fabrication scenario. The periphery was formed by three borders applying the same spot size for all. While the surface quality and feature resolution of the resulting second object was slightly improved over that of the first object, the time penalty for fabrication according to the second fabrication scenario was 60% compared to the first fabrication scenario (i.e. the overall fabrication time was about 60% longer for the second scenario compared to the first scenario).

[0075] In a third fabrication scenario, the same object was manufactured according to embodiments of the present invention. The periphery was formed by applying five borders, each border using a gradually increasing spot size towards the inward direction, as illustrated in FIG. 4. The smallest spot size of the outermost border was smaller (about 120 pm in spot size) than the spot size of the borders of the second fabrication scenario. The inner portion was fabricated using a spot size of 400 pm in spot size. The resulting third object achieved significantly improved spatial resolution and superior surface quality compared to the second object. Surprisingly, despite applying more borders than in the second scenario, the time penalty for fabrication according to the third fabrication scenario was only 6.7% compared to the fabrication according to the first fabrication scenario.

[0076] The above set of experiments demonstrates the advantage of the present embodiments whereby the spatial resolution in the third scenario was increased by more than 50% compared to the first fabrication scenario (120 pm compared to 250 pm) without substantially increasing the fabrication time.

[0077] The lateral separations between the centers of the beam spots, as illustrated in FIG.

[0078] 3B by si between the centerlines of the outermost and intermediate borders 64-1 and 64-2, and s2 between the centerlines of the intermediate and innermost borders 64-2 and 64-3, may be controlled by controller 36. Typically, there is a certain overlap between adjacent beamspots, so that the lateral separation between the centers of adjacent beam spots is less than for example the sum of their radii, as illustrated in FIGs. 3A-5.

[0079] Preferably, controller 36 adjusts these lateral separations based on the set of spot sizes from which it selects the spot sizes for the periphery. In embodiments of the invention, the lateral separation between at least one pair of adjacent beam spots, more preferably between any pair of adjacent beam spots, is p times the average beam spot size of the beam spots in the pair, where p is a dimensionless parameter referred to herein as an overlap parameter. The overlap parameter p can be predetermined or, if desired, received as a user input. Typical values of the overlap parameter p include, without limitation, any value from about 0.3 to about 0.5.

[0080] Mathematically, the lateral separation between two adjacent beam spots denoted beam spot i and beam spot j can be defined according to the following equation:

[0081] Sij = 0.5 01 + Dj) (EQ. 1) where, in EQ. 1, sij is the lateral separation between the beam spots i and j, and Di and Dj are the respective spot sizes of beam spots i and j. The overlap parameter p relates to the degree of overlap between beam spots i and j along a line connecting the centers of the respective beam spots. The relation can be approximated as 1-p. Thus, for example, an overlap parameter of / ?=().4 defines an overlap of about 60% between the respective beam spots along a line connecting their centers.

[0082] Preferably, controller 36 can select the lateral separations (e.g., by selecting a value for the overlap parameter p) so as to ensure a generally uniform energy density imparted by the beam spots over the periphery, and preferably also over the entire object layer. This ensures a uniform degree of solidification across the periphery 56, and preferably also over the entire object layer. This will now be explained in greater detail with reference to FIG. 6 and comparative FIG. 10.

[0083] FIGs. 6 and 10 are graphs showing energy densities (in mJ / cm2) delivered by beam spots of different sizes as a function of a position from the outer contour of the periphery 56 along the inward direction. Shown are individual energy density curves delivered by each beam spot, based on their beam spot size, in the periphery and over part of the inner portion adjacent the periphery. Also shown is a resultant curve of total energy density against position along the inward direction based on the combination of the individual beam spot energy densities, and a resulting curve representing the effective penetration depth of curing (cure depth) due to the beam spots against position along the inward direction. Without lossof generality and without wishing to be bound to a particular calculation model, the energy density values herein were calculated assuming a Gaussian falloff of the energy density away from the center of the beam spot, and the effective cure depth was calculated as a logarithmic function of the total energy density. As shown, the peak energy density for each beam spot is generally constant. This was achieved by adjusting the input power to the light source for each beam spot size to achieve the same peak energy density.

[0084] To achieve the resulting total energy density and curing profile of FIG. 6, the overlap conditions of the energy density profiles between adjacent beam spots were selected, to provide a total energy density which is generally uniform (e.g., with deviation from uniformity of less than 10% or less than 5% or less than 2% or less than 1% from linearity) across the periphery of the layer, and preferably also across the delineation or transition from periphery to inner portion. Optionally, as shown, uniformity is also maintained across the inner portion although this may not be necessary. Achieving a uniform energy density across the periphery and optionally also the transition area is advantageous since it provides a generally uniform curing depth and improves the quality of the layer. For one or more of the topmost or lowest layers, the same principle may be applied across the inner portion so as to achieve a high quality surface finish, for example on planar, horizontal portions of the object surface.

[0085] In experiments performed by the Inventor it was found that a generally uniform total energy density as provided by different beam spot sizes, but generally the same peak energy density at a center of the beam spot, can be achieved by selecting an overlap parameter of from about 0.3 to about 0.5, e.g., about 0.4. For the beam spots forming the inner portion, a predefined overlap parameter such as 0.4, may also be chosen. The peak energy density of the beam spots forming the inner portion, at their specified beam spot size, may be chosen to be the same as that of the beam spots in the periphery.

[0086] To further illustrate the effect of the embodiments of the invention described with reference to FIG. 6, FIG. 10 corresponds to calculations based on beam spots for which considerations for the degree of overlap were not made as for those in FIG. 6. The resulting total energy density is significantly nonuniform, namely the energy density varies significantly with position across the object layer. The effect of such significantly varying energy density leads to undesirable variations in cure depth, e.g. overcured and / or undercured regions resulting in an uncontrolled layer thickness, that significantly reduces the quality of the formed object.In embodiments of the present invention, computerized controller 36 may be configured to vary the input power to the light source 34 of light beam 38. For at least two different beam spot sizes within periphery 56 for example, and more preferably for each beam spot size within periphery 56, and optionally also for the or each beam spot size within the inner portion 58, different input power levels may be defined and / or may be selected by controller 36 for the respective beam spots. Preferably, the variation in input power is executed automatically based on the set of beam spot sizes from which the controller 36 selects the sizes of the beam spots 62-1, 62-2, etc. Thus, for example, to control the peak energy density of each beam spot size, the controller 36 can select a first power level for first beam spot 62-1 to form first border 64-1, a second power level (different from the first power level) for the second beam spot 62-2 to form second border 64-2 inwards of the first border, a third power level (different from the first and the second power levels) for the third beam spot 62-3 to form third border 64-3 inwards of the second border, and so on. Typically, lower power levels are selected for smaller spot sizes to achieve the same peak energy density compared to a larger beam spot size. The power levels are optionally and preferably selected to ensure a generally uniform total energy density across at least the periphery 56, as described above. The power level employed for inner portion 58 of layer 28 may be constant without variation, and may be lower, the same or higher than any of the power levels employed for beam spots within the periphery 56.

[0087] In embodiments of the present invention, computerized controller 36 varies the scanning speed of beam spots 62, wherein for at least two different sizes of beam spots within periphery 56, a different scanning speed is selected with these spot sizes. Preferably, the variation is executed automatically based on the set of sizes from which the controller 36 selects the spot size of beam spots 62-1, 62-2, etc. for each border 64-1, 64-2 etc. of the periphery 56. Thus, for example, controller 36 can select one scanning speed for beam spot 62-1 for the outermost border 64-1, and a faster scanning speed for the beam spots 62-2, 62-3, 62-4 and 62-5, e.g., to form the other borders 64-2, 64-3, 64-4, and 64-5 inwards of the outermost border 64-1 of periphery 56. A typical scanning speed for the borders is from about 2 m / s to about 6 m / s, e.g., or from about 3m / s to about 5 m / s. The scanning speed for beam spots within the inner portion 58 of layer 28 may remain constant without variation. The scanning speed employed for inner portion 58 is optionally and preferably faster than the scanning speed employed for any border within the periphery 56. A typical scanning speed for beams spots forming the inner portion 58 is from about 12 m / s to about 24 m / s,e.g, from about 15 m / s to about 18m / s. Preferably, the input power provided for each beam spot is further adjusted based on the scanning speed selected for that beam spot so as to achieve the same effective peak energy density as for the other beam spots. This provides for a most simple approach to generate the overlap between the beam spots.

[0088] The set of possible beam spot sizes to illuminate each border is preferably selected before commencing the fabrication of the object. In embodiments in which the controller varies the input power and / or scanning speeds, a lookup table associating each spot size value of the set to an input power value and / or a scanning speed value can be employed. The set of beam spot sizes can be a default set which can be the same default set for all objects fabricated by system 10, or it can be prepared specifically for a particular object to be fabricated. When the set is a default set, it can be stored in a memory medium of computerized controller 36 or in a memory medium of computer 50 and be transmitted to controller 36, e.g. via a remote link.

[0089] When a set is prepared specifically for a particular object, it can be calculated by circuit 37 of controller 36 or by computer 50 and be transmitted to controller 36. The calculation is optionally and preferably based on an input parameter pertaining to one beam spot size of the set. Such a parameter can be the size itself or a proxy thereof (e.g., a corresponding radius, namely half the size, or a corresponding area value, etc.). For example, the smallest size of the set (the size of beam spot 62-1, applied for outermost border 64-1, in the exemplified illustration of FIG. 4), can be received as input and be used for calculating all other beam spot sizes in periphery 56, according to a pre-programmed set of criteria, e.g, the aforementioned monotonic function. Once the set is calculated, computerized controller 36 (or computer 50) optionally and preferably also calculates other fabrication parameters based on the calculated set. Such other fabrication parameters may include, but are not limited to, power levels for the light source 34 for each beam spot size, and scanning speed and separation between centers (i.e. degree of overlap) of beam spots of adjacent border paths.

[0090] Compared to the calculated set, the default set of beam spot sizes may be restricted to a smaller number of beam spot sizes to form the borders within the periphery 56. The default set of beam spot sizes may include four different beam spot sizes, of which the three smaller beam spot sizes can be selected to form the borders of the periphery 56 as described above, and of which the fourth, largest, beam spot size of the default set was selected to form the inner portion 58.The input parameter can be received via user interface 52 of computer 50. Preferably the input parameter is received by means of a graphical user interface (GUI) which is displayed by computer 50 on a display device 51 of computer 50. The GUI provides an easy to use interface between the end-user of the AM system 10 and the computer. The GUI includes a plurality of graphic objects, which are referred to as "GUI controls", or in a more abbreviated term "controls." Representative examples of GUI controls suitable for the present embodiments include, without limitation, a slider, a dropdown menu, a combo box, a text box and the like.

[0091] The GUI can optionally and preferably display additional information, such as non-interactive text and graphics.

[0092] During operation, the end-user can select and activate the controls in order to initiate operations to be executed by the processor of computer 50. The GUI transmits activation signals to the processor, for example, by means of an I / O circuit configured to communicate signals between the GUI and the processor. The activation signals can be transmitted to the processor either upon activation of the respective control, or at a later time (e.g, upon activation of another control). The controls are represented on the GUI as graphical elements that are optionally and preferably labeled in a manner that is indicative of the operation that the processor executes responsively to the activation of these controls. The controls may be arranged in predefined layouts, or may be created and / or removed dynamically responsively to specific actions being taken by the end-user by means of other GUI controls. By way of example, a user may select a button that opens or closes another control, expands a control, displays an image, and / or switches between GUI layouts (oftentimes referred to as GUI screens).

[0093] The GUI of the present embodiments receives from the end-user, by means of the GUI controls, input pertaining to a scanning mode and / or a beam spot size of the set of beam spot sizes from which controller 36 selects the beam spot size for each border within periphery 56 and optionally also for inner portion 58. Responsively to activation of one or more of the GUI controls, the I / O circuit of computer 50 communicates signals pertaining to this input from the GUI to the processor. The processor calculates all other beam spot sizes in periphery 56, according to the pre-programmed set of criteria, and optionally and preferably also other fabrication parameters as described above.

[0094] A representative example of a GUI 70 suitable for the present embodiments is illustrated in FIG. 7. GUI 70 can comprise a scanning mode selection control 72 and / or abeam spot size selection control 74. Typically, GUI 70 comprises a control 76 for allowing the end-user to secure the selection or selections made by saving them into a memory medium of the computer. In an embodiment of the invention, scanning mode selection control 72 allows the user to select between a predefined scanning mode. In the illustration shown in FIG. 7, which is not to be considered as limiting, scanning mode selection control 72 allows the user to select between a scanning mode referred to as "Standard Definition (SD)" and a scanning mode referred to as "High Definition (SD)," but more than two modes can be displayed according to embodiments of the present invention. The difference between the scanning modes is at least the beam spot size of the smallest beam spot that may be created by the optics for the light beam 38. The beam spot size selection control 74 allows the user to select a beam spot size from the set of beam spot sizes, and from which controller 36 selects the beam spot sizes for all borders within periphery 56 and optionally also for the inner portion 58. Preferably, beam spot size selection control 74 allows entering the beam spot size as a continuous parameter, but embodiments in which the user can only select a beam spot size from a predefined list are also contemplated.

[0095] In embodiments of the present invention, the user is allowed to select a beam spot size by means of beam spot size selection control 74 conditionally to the scanning mode selected at scanning mode selection control 72. In these embodiments, based on the input from control 72, the processor of computer 50 either selects the default set of beam spot sizes, or calculates the beam spot sizes of the set according to input from beam spot size selection control 74. For example, when the user selects the HD mode, control 74 can allow selecting a beam spot size for this scanning mode. For example, the smallest available beam spot size in HD mode may be smaller than the smallest available beam spot size in the SD mode. Additionally, or instead, the numbers of borders over which the periphery is to be formed may be higher in HD mode than in SD mode. In this case, the processor calculates the beam spot sizes of the set according to the beam spot size selected by the user by means of beam spot size selection control 74, and according to the number of borders over which the periphery is to be formed. When the user selects the SD mode, the user operation on spot size selection control 74 can be inhibited (e.g, the control cannot be chosen by the user), in which case the processor selects the default set of diameters.

[0096] In embodiments of the present invention GUI 70 comprises an information control 78. The processor of computer 50 can use this control to convey various types of information to the user. For example, information control 78 can display the expected fabrication time ofthe object, given the computer object data that describe the object and the other fabrication parameters. In embodiments of the present invention the processor uses the computer object data to analyze the geometry of the object, in particular the characteristic radii of curved segments over the outer surfaces of the object, and display at information control 78 indication describing the compatibility between the analyzed geometry and the current selection of the smallest beam spot size of the calculated of default set, as the case may be. For example, when the geometry includes features of very small radii and the current selection in scanning mode selection control 72 and beam spot size selection control 74 corresponds to a smallest beam spot size that is too large for these radii, information control 78 can recommend selecting another scanning mode and / or beam spot size. Conversely, when the geometry includes only features with very small curvature (namely relatively flat features) and the current selection in scanning mode selection control 72 and beam spot size selection control 74 corresponds to a smallest beam spot size that is very small, information control 78 can recommend selecting the SD scanning mode and / or a larger beam spot size, so as to reduce the fabrication time. In a less automated system, any or any combination of the above control options may alternatively be user selected or input by the user. The analysis can optionally and preferably be applied to slice data rather than to the graphic elements of the computer object data. In these embodiments, the processor of computer 50 or the circuit 37 of computerize controller 36 as the case may be, can analyze the outer contour 55 of each of the layers of the object, in particular the characteristic radii of curved segments over the outer contour 55, and display at information control 78 indication describing the compatibility between the analyzed outer contours and the current selection of the smallest beam spot size of the calculated of default set as further detailed hereinabove.

[0097] The computerized controller may be comprised within the AM system, or it may be remote from, and configured to provide the generated scanning control data to, the AM system.

[0098] Turning back to FIG. 1, once object layer 28 is completed, controller 36 may deactivate the light source 34. Controller 36 then causes the distance between surface 21 of platform 20 and surface 18 of liquid 16 to be increased as described herein. The extent of the increment equals at least the thickness of a single layer of object 12. Optionally, the extent of the increment or vertical distance may be increased by more than the thickness of a single layer for the following reasons. The relatively high viscosity liquid material 16 may make it difficult to create a uniform liquid film 17 over the upper surface of layer 28 by natural flowfollowing immersion. Consider the state shown in FIG. 1, namely after a plurality of layers 26 of object 12 has already been formed, where the topmost object layer of layers 26 is layer 28. Due to the high viscosity of liquid 16, when the distance between platform surface 21 and liquid surface 18 is increased, liquid surface 18 becomes non-planar, wherein the thickness of liquid film 17 above the topmost layer 28 is nonuniform, and may potentially include imperfections such as bulges, depressions, and holes, which, if not reduced or eliminated, may create inaccuracies in the next layer.

[0099] In embodiments of the present invention therefore, system 10 comprises a recoater 30, which may be a blade or a roller. Controller 36 optionally and preferably operates recoater 30 to level the upper surface 18 of film 17. The levelling is performed by moving the recoater 30 horizontally (along x) so as to evenly spread the liquid 16 over the uppermost layer. To further facilitate the recoating of layer 28 by liquid, a liquid delivery duct 32 may transfer an amount of liquid from the vat 14, e.g. from a location at a periphery of the vat, to the recoater 30 such that the recoater supplies liquid to upper surface 18 while also levelling upper surface 18.

[0100] Controller 36 can then reactivate the light source 34 to form a subsequent layer on uppermost layer 28 which is now immersed in its entirety under surface 18 and coated by uniform film 17 of liquid 16.

[0101] While the system 10 is described in some detail as a “top down” system, in which light source 34 is located above the vat and the object is built on the upward-facing surface of a platform immersed in the vat, the technique according to embodiments of the invention can employ a “bottom-up” manufacturing, in which the light source 34 is located below the vat and the object is built on the downward facing surface of a platform suspended above the vat. System 10 may thus be configured to manufacture the layers to build the object from the “bottom up”. In these embodiments, the light source 34 and light handling mechanism 40 are located below the vat 14, which has a floor 15 that is transmissive to the light beam of the light source 34, for example by being equipped with a dedicated window 13 that is transmissive to the light beam and that is covered by a thin transparent membrane. The platform in these embodiments is initially immersed within the vat, and the first layer is formed on the downward facing side of the platform. The liquid film in this configuration is formed between the transmissive membrane and the downward facing side of the platform. After each layer is formed, the platform is lifted, the formed object layer is separated from the membrane by the upward pulling force, e.g., and a new film is formed between the last-formed object layer and the membrane. The light beam is directed through the vat floor 15 or window 13 upwards to illuminate the bottom surface 19 of liquid film 17 so as to solidify each new layer on the downfacing side of the previous layer. The platform moves upwards in a step wise manner to gradually draw the formed layers out of the vat 14.

[0102] In any of the above embodiments for system 10, the light scanning control system 54 may further comprise a second light source (not shown) in the form of an array of individually addressable light emitting diodes, or a digital light processing (DLP) projector, that is configured to direct multiple beamlets simultaneously to the liquid surface 18. The DLP passes light from the second light source through a mask with multiple individually addressable apertures (e.g. a liquid crystal mask). Such a second light source may be operated to project multiple beamlets onto the surface 18 to cure large portions of the layer, or the entire layer, simultaneously. Typically, projection is faster but with lower resolution than scanning. Therefore, the second light source may be used to cure the inner portion 58 of the layer 28 fast since these are not visible and accuracy is not required. In embodiments in which light handling mechanism 40 comprises a second light source in the form of an array of photodiodes or a DLP projector, circuit 37 of controller 36 controls the second light source, for example as part of the light handling system 40, to project patterns which form the inner portion 58 of a layer 28 of object 12.

[0103] A method according to embodiments of the invention suitable for scanning light in additive manufacturing will now be described with reference to FIG. 8A, which is a flowchart outlining the steps of the method. The method can also be used for fabricating a three-dimensional object by additive manufacturing. At least a portion of the operations of the method can be executed by system 10 described above.

[0104] It is to be understood that, unless otherwise defined, the operations described hereinbelow can be executed either contemporaneously or sequentially in many combinations or orders of execution. Specifically, the ordering of the flowchart diagrams is not to be considered as limiting. For example, two or more operations, appearing in the following description or in the flowchart diagrams in a particular order, can be executed in a different order (e.g., a reverse order) or substantially contemporaneously. Additionally, several operations described below are optional and may not be executed.

[0105] The method comprises:At 91, receiving object data defining the shape of each layer, for example in slice format that defines in each slice the shape of a corresponding object cross section, or layer, to be formed.

[0106] At 92, defining, or calculating, beam spot paths that include two or more borders and an inner portion pattern based on the object data for each slice to generate the beam path control data, for example vector data that directs the path of the light beam.

[0107] At 93, defining or selecting different beam spot sizes for each border and optionally for the inner portion, such that for the outer border the smallest beam spot size is chosen and for the innermost border the largest beam spot size, where the borders follow the inner contour shape of the object cross section and are arranged in a curvilinear, parallel relation to one another. The beam spot sizes may be chosen for example at a user interface or are predefined as a default set of parameters.

[0108] The operations at 91 to 93 may be carried out by circuit 37 of the computerized controller 36 configured to generate scanning control data for the vat photopolymerization apparatus, where the computerized controller 36 is remote from the vat photopolymerization apparatus. In this case the computerized controller 36 may be comprised within the host computer, or may be connected or connectable to the host computer 50 by a direct or remote link, via a network connection, or via a removable memory. Said control data may be provided by the circuit 37 to the computerized controller 36 to control the AM system.

[0109] The circuit 37 may be comprised within the computerized controller, and the computerized controller 36 may be comprised within the vat photopolymerization apparatus, in which case computerized controller 36 may further be configured to control the following operations of the AM system 10:

[0110] At 94, generating a liquid layer in a vat adjacent a platform or previous layer, for example a liquid layer over the newly completed layer or over the support platform according to any of the variants described herein.

[0111] At 95, scanning the light beam according to the defined pattern to solidify the inner portion

[0112] At 96, scanning the light beam along the two or more borders at different beam spot sizes to cure the periphery and thus complete the layer.

[0113] At 87, adjusting the vertical distance of the platform to generate a new liquid layer according to any of the variants described herein.One or more of the above operations can be repeated steps until the object is complete. The method ends at 98.

[0114] In a variant of the method, described with reference to Fig. 8B, the method begins at 80 to initiate the object formation process and continues to 81 at which computer object data that collectively pertain to a shape of the object in the form of one or more input parameters are received. For example, the computer (e.g, host computer 50) can access a computer-readable storage medium and retrieve the input data from the medium. The computer can also generate the input data, or a portion thereof, instead of, or in addition to, retrieving data from the storage medium, for example, by means of computer aided design (CAD) software or computer aided manufacturing (CAM) software. The computer object data can include a plurality of graphic elements defining the outer surface of the object model, which in embodiments of the present invention are transformed to a grid of voxels, or 2D pixels which together with a defined layer thickness define the voxels of each layer of the object, e.g, using slicer software as further detailed hereinabove. Alternatively, the method may comprise receiving sliced computer object data (“data slices”) from an external source, e.g, a computer-readable medium, in which case it is not necessary to execute the slicing operation. The data can be in any data format known in the art, including any of the aforementioned computer object data formats.

[0115] The computer communicates with the controller of the system (e.g, controller 36 of system 10), to allow the computer to transfer the data to the controller. The computer can be configured to transfer all the data to the controller before the additive manufacturing process begins, or to initially transfer only a portion of the data, and continue transferring during the additive manufacturing process, e.g, upon a request from the controller. For example, the computer can be configured to transmit the data on a slice-by-slice basis, or in batches of two or more slices at a time.

[0116] The method optionally and preferably proceeds to 82 at which one or more input parameters are received. The input parameter or parameters can be received by means of a user interface, such as, but not limited to, user interface 52 and / or GUI 70. The method optionally and preferably proceeds to block 83 at which a set of beam spot sizes is obtained, based on the input parameters. For example, when the input parameter(s) include a scanning mode, the method may comprise determining whether to use a default set of beam spot sizes or to calculate beam spot sizes for the set using an input parameter pertaining to one beamspot size of the set as further detailed hereinabove. Alternatively, the operation at 82 can be skipped in which case the default set of diameters is obtained at 83.

[0117] As for the method described with reference to Fig. 8A, the slice data is converted into scan path control data defining at least two borders to form the periphery, according to any of the embodiments described herein, and a fill pattern to form the inner portion of the layer. Furthermore, each border is associated with a different beam spot size according to any of the embodiments described herein, and such that the beam spot size of the outermost border is the smallest and the beam spot size of the innermost border is the largest over the periphery. The beam spot size for the fill pattern to solidify the inner portion may be the same as the spot size for the innermost border or larger.

[0118] The method can then proceed to 84 at which a topmost liquid layer is created in the vat, for example by immersing a platform (e.g, platform 20) in a liquid that is curable by light (e.g, liquid 16). Preferably, the platform is immersed in a manner that the vertical distance between the liquid surface and the top surface of the platform (when no layer was yet to be formed on the platform) or the uppermost, newly formed layer (when at least one layer was formed on the platform) is at least the thickness of a single layer of object (e.g, the thickness of the most newly formed layer). In embodiments of the present invention, the operation at block 84 is executed to ensure that the vertical distance between the surface of the liquid and the top surface of the platform, or the top surface of the most newly formed layer, is more than the thickness of a single layer (e.g, more than the thickness of the most newly formed layer). In this case, a recoater may be operated to level the liquid over the topmost layer to create a new liquid surface.

[0119] At 85 the inner portion of the layer to be formed is solidified according to any of the embodiments described herein. The beam spot size applied to the inner portion may be larger, the same or smaller than the largest beam spot size applied to the borders of the periphery.

[0120] At 86, a light beam scans the liquid surface along two or more border paths, applying a different beam spot size for each border, to complete the solidified layer. As described herein, the beam spot size for the outermost border is smaller than the beam spot size of the inner border. The beam spot size of the beam spot within the periphery of the layer is increasing in size / diameter inwardly from one border to the next for the determined or selected number of borders that define the periphery.

[0121] Optionally, the method proceeds to block 87 at which the vertical distance of the platform is adjusted to generate a new topmost liquid layer. The topmost liquid layer is theliquid layer in direct contact with the newly formed layer. As described herein, where the platform is immersed in the vat, the vertical distance may be more than the thickness of a single layer, and block 87 may include reducing or optimizing the distance to ensure that the vertical distance between the liquid surface and the surface of the uppermost layer is approximately (e.g., within a tolerance of about 10% or less or about 5% or less or about 1% or less) the thickness of a single layer (e.g, the vertical distance may be approximately the same as the thickness of the uppermost layer). This may include operating the recoater as described herein. The method can then loop back to 81 for receiving computer object data of the next layer of the object. Where the data of the next layer of the object are already loaded, the method can loop to 85 for forming the next layer.

[0122] The method ends at 88 once all layers of the object are complete.

[0123] The method of scanning light in additive manufacturing may thus comprise: receiving position data describing a layer of a three-dimensional object; scanning a surface of a photocurable liquid by a photocuring light beam according to said position data to form on said surface a shape defining said layer, the layer comprising a periphery portion and an inner portion, wherein the periphery portion surrounds the inner portion; and

[0124] varying a spot size of said light beam on the photocurable liquid surface between two or more curvilinear parallel border paths traced by the light beam, such that the spot size of said light beam is increased inwardly from one border, e.g. the outer border, to the next (e.g. an intermediate, or innermost border) across the periphery towards the inner portion of said layer.

[0125] As used herein the terms “about” and approximately refer to ± 10 %.

[0126] Implementation of the method and / or system of embodiments of the invention may involve performing or completing selected tasks manually, automatically, or a combination thereof. Moreover, according to actual instrumentation and equipment of embodiments of the method and / or system of the invention, several selected tasks may be implemented by hardware, by software or by firmware or by a combination thereof using an operating system. For example, hardware for performing selected tasks according to embodiments of the invention may be controlled by instructions provided on a chip or a circuit. Selected tasks according to embodiments of the invention may be implemented by a plurality of software instructions being executed by a computer using any suitable operating system. In anexemplary embodiment of the invention, one or more tasks according to exemplary embodiments of method and / or system as described herein are performed by a data processor, such as a computing platform for executing a plurality of instructions. Optionally, the data processor includes a volatile memory for storing instructions and / or data and / or a nonvolatile storage, for example, a magnetic hard-disk and / or removable media, for storing instructions and / or data. The data processor may be connected to the hardware by direct or remote link, via a network connection.

[0127] Disclosed herein is a method of scanning light in additive manufacturing, comprising: receiving position data describing a layer of a three-dimensional object; scanning a liquid film by a beam spot of a light beam according to said position data to form on said film a shape defining said layer; and

[0128] varying a beam spot size of said beam spot, by selecting said beam spot size from a set of beam spot sizes so as to ensure that the beam spot size within a periphery of said layer is increasing inwardly with respect to an outer contour of said layer.

[0129] Said scanning may comprise, for each beam spot size, scanning by said beam spot along a path within and following an outer contour of said layer, such that the periphery is formed from two paths or more; optionally, said paths forming the periphery are closed paths and / or said paths forming the periphery are extending side by side to one another.

[0130] Said varying may comprise selecting from said set of beam spot sizes an additional beam spot size for an inner portion of said layer, optionally wherein said inner portion is formed by scanning the beam spot at the additional size along a set of inner portion paths and optionally wherein said set of inner portion paths of said inner portion forms a crosshatch pattern. Optionally, said additional beam spot size is larger than a largest beam spot size within said periphery.

[0131] The method of scanning light may further comprise selecting lateral separations between centers of adjacent beam spots based on said set of beam spot sizes. Optionally said selecting said lateral separations is to ensure a generally uniform exposure to light along a pattern formed by said beam spots, and / or for at least two adjacent beam spots, said selecting said lateral separations is so as to ensure that a lateral separation between said adjacent beam spots is from about 0.3 times an average beam spot size of said adjacent beam spots to about 0.5 said average beam spot size of said adjacent beam spots.

[0132] The method of scanning light may further comprise: varying a power of said light beam, based on said set of beam spot sizes, wherein for at least two different beam spot sizeswithin said periphery, different power levels are selected for beam spots having said beam spot sizes; and / or varying a speed of said scanning, based on said set, wherein different scanning speeds are selected for at least two different beam spot sizes within said periphery. Alternatively, the method may comprise, based on said set of beam spot sizes, varying a power of said light beam and varying a speed of said scanning, wherein, for at least two different beam spot sizes within said periphery, different scanning speeds are selected, and wherein different power levels are selected based on said beam spot sizes and said scanning speeds.

[0133] The method may further comprise receiving parameter pertaining to one beam spot size of said set, and calculating other beam spot sizes of said set based on said parameter. Optionally, said parameter pertains to a smallest beam spot size of said set of beam spot sizes.

[0134] The method of scanning light may further comprise displaying a graphical user interface (GUI) having a beam spot size selection control, wherein said receiving said parameter is according to input received from said beam spot size selection control.

[0135] Instead of receiving a parameter, the method may comprise displaying a graphical user interface (GUI) having a scanning mode selection control, and selecting a default set for said set of beam spot sizes according to input received from said scanning mode selection control.

[0136] Further disclosed is a method of fabricating an object in layers by additive manufacturing, the method comprising:

[0137] forming a liquid film of a liquid curable by radiation;

[0138] forming a layer of the object over said liquid film by executing the method according to any of the methods of scanning light disclosed herein; and

[0139] generating a new liquid film contacting said layer in preparation for forming a subsequent layer of the object.

[0140] Further disclosed is a system for scanning light in additive manufacturing, comprising: an irradiation system configured to generate a scannable light beam to form a beam spot on a liquid film, the irradiation system being also configured to control a beam spot size of said beam spot; and a computerized controller having a circuit configured to receive position data describing a layer of a three-dimensional object, to control said irradiation system to scan said liquid film by said beam spot according to said position data to form on said liquid film a shape defining said layer, and to control said irradiation systemto vary said beam spot size by selecting said beam spot size from a set of beam spot sizes so as to ensure that said beam spot size is increased within a periphery of said layer inwardly with respect to an outer contour of said layer.

[0141] Optionally, said circuit of said computerized controller is further configured to control said irradiation system of the system for scanning light to scan each beam spot within the periphery and along a border path following an outer contour of said layer, such that the periphery is formed from the border paths within the periphery. Optionally, said border paths within the periphery are closed paths and / or said border paths are defined to extend side by side.

[0142] Said computerized controller of said system for scanning light may further be configured to select from said set of beam spot sizes an additional beam spot size for patterns within an inner portion of said layer; additionally, or instead, said computerized controller may be configured to control said irradiation system to scan an inner portion of said layer at the additional beam spot size, and along at least two border paths within said periphery at respective selected beam spot sizes. Said additional beam spot size may be larger than a largest beam spot size within said periphery.

[0143] The computerized controller may be configured to select lateral separations between centers of beam spots illuminated by said light beam based on said set of beam spot sizes. Said computerized controller, when selecting said lateral separations, may further be configured to ensure a generally uniform exposure to light along a pattern formed by said beam spot; and / or to select said lateral separations to ensure that a lateral separation between said adjacent beam spots is from about 0.3 times an average beam spot size of said adjacent beam spots to about 0.5 said average beam spot size.

[0144] The computerized controller of the system for scanning light may be configured to vary a power of said light beam, based on said set of beam spot sizes, wherein different power levels are selected by said computerized controller for at least two different beam spot sizes within said periphery, and / or to vary a speed of said scanning, based on said set, wherein different scanning speeds are selected by said computerized controller for at least two different beam spot sizes within said periphery.

[0145] The computerized controller of the system for scanning light may be configured to receive a parameter pertaining to one beam spot size of said set, and to calculate other beam spot sizes of said set based on said parameter. Said parameter may pertain to a smallest beam spot size of said set.Any of the systems for scanning light may comprise a display device, and a computer having a processor configured to display on said display device a graphical user interface (GUI) having one of: a beam spot selection control, wherein the processor is configured to receive from said GUI user responses and to calculate beam spot sizes of said set according to input received from said beam spot selection control; a scanning mode selection control, wherein the processor is configured to receive from said GUI user responses, and to select said set of beam spot sizes according to input received from said scanning mode selection control; or, a scanning mode selection control and a beam spot selection control, wherein the processor is configured to receive from said GUI user responses, and, based on an input from said scanning mode selection control, to either: select a default set for said set of beam spot sizes; or calculate beam spot sizes of said set of beam spot sizes according to said input from said beam spot selection control.

[0146] Said GUI may comprise an information control, wherein said processor is configured to analyze a geometry of an external surface of said three-dimensional object, and to display at said information control an indication describing a compatibility between said geometry and a smallest beam spot size of said set of beam spot sizes.

[0147] Further disclosed is an additive manufacturing system, comprising: the system for scanning light as described herein; a vat configured to be filled with a liquid curable by radiation of said irradiation system; and a vertically movable platform configured to be immersed in said liquid. Also disclosed is a method of generating scanning control data for an irradiation system of an additive manufacturing system, the irradiation system being configured to form, using a light beam, beam spots on a liquid film in accordance with a shape defining a layer of a three-dimensional object, the method comprising: receiving position data describing an inner portion and a periphery of the layer;

[0148] selecting from a set of beam spot sizes a beam spot size for each beam spot so as to ensure that beam spot sizes within said periphery are increasing inwardly toward said inner portion, wherein the scanning control data for the layer comprises a plurality of beam spot sizes selected from said set; and

[0149] transmitting scanning control data to a computer readable medium.

[0150] Optionally, the method comprises providing the generated scanning control data to the additive manufacturing system.

[0151] The method may further comprise selecting two or more border paths lying side-by-side within, and following, an outer contour of the layer, wherein selecting from a set ofbeam spot sizes comprises selecting a beam spot size for each border path within the periphery, optionally wherein each border path within the periphery is a closed path.

[0152] Additionally, or instead, the method of generating scanning control data may comprise selecting from said set an additional beam spot size for said inner portion of the layer; optionally further comprising associating said additional beam spot size with each beam spot along a set of inner portion paths within said inner portion. Said set of inner portion paths of said inner portion may form a cross-hatch pattern, and / or said additional beam spot size may be larger than a largest beam spot size within said periphery. The method of generating scanning control data may comprise selecting lateral separations between centers of adjacent beam spots based on said set of beam spot sizes. Said selecting said lateral separations may comprise selecting lateral separations between adjacent beam spots within said periphery and said inner portion, and optionally selecting lateral separations between adjacent beam spots within said inner portion. Additionally, or instead, for at least two adjacent beam spots, said selecting said lateral separations may be so as to ensure that a lateral separation between said adjacent beam spots is from about 0.3 times an average beam spot size of said adjacent beam spots to about 0.5 said average beam spot size. Said selecting said lateral separations may be such as to ensure a generally uniform exposure to light along a pattern formed by said beam spots. Optionally, said selecting said lateral separations comprises selecting lateral separations between adjacent beam spots within said periphery and / or said inner portion, and optionally selecting lateral separations between the adjacent beam spots of the inner-most border path and of the inner portion paths within said inner portion.

[0153] The scanning control data for the layer may comprise a plurality of power levels for the light beam, in which case the method of generating scanning control data may comprise selecting, based on said set of beam spot sizes, said plurality of power levels, to associate different power levels with at least two different beam spot sizes within said periphery. Additionally, or instead, wherein the scanning control data for the layer comprises a plurality of scan speeds for each beam spot size, the method may comprise selecting, based on said set, said plurality of scan speeds, to associate different scanning speeds with at least two different beam spot sizes within said periphery.

[0154] Alternatively, wherein the scanning control data for the layer comprises a plurality of power levels for the light beam and a plurality of scan speeds for each beam spot size, the method may comprise selecting, based on said set of beam spot sizes, said plurality of scanspeeds, and selecting, based on said set and said scan speeds, the plurality of power levels, to associate different power levels with at least two different beam spot sizes within said periphery. The method of generating scanning control data may comprise receiving parameter pertaining to one beam spot size of said set, and calculating other beam spot sizes of said set based on said parameter. Optionally, said parameter pertains to a smallest beam spot size of said set of beam spot sizes. The method of generating scanning control data may comprise displaying a graphical user interface (GUI) having one of: a beam spot size selection control, and wherein said receiving said parameter is according to input received from said beam spot size selection control; or, a scanning mode selection control, wherein the method comprises selecting a default set for said set of beam spot sizes according to input received from said scanning mode selection control. Alternatively, The method of generating scanning control data may comprise displaying a graphical user interface (GUI) having a scanning mode selection control and a beam spot selection control, wherein the method comprises receiving user responses, and, based on an input from said scanning mode selection control, either: select a default set for said set of beam spot sizes; or, calculate beam spot sizes of said set of beam spot sizes according to said input from said beam spot selection control. Optionally, the method of generating scanning control data may comprise analyzing a geometry of the or an outer contour of said layer, displaying the or a graphical user interface (GUI) having an information control, and displaying at the information control an indication describing a compatibility between said geometry and a smallest beam spot size of said set of beam spot sizes.

[0155] A computer software product comprising a computer-readable medium in which program instructions are stored is disclosed, which instructions, when read by a data processor having a circuit, cause the circuit to execute any of the methods of generating scanning control data.

[0156] The terms "comprises", "comprising", "includes", "including", “having” and their conjugates mean "including but not limited to".

[0157] The term “consisting of’ means “including and limited to”.

[0158] 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.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.

[0159] Throughout this application, various embodiments of this invention may be presented in 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 the invention. 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.

[0160] Whenever a numerical range is indicated herein, it is meant to include any cited numeral (fractional or integral) within the indicated range. The phrases “ranging / ranges between” a first indicate number and a second indicate number and “ranging / ranges from” a first indicate number “to” 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 numerals therebetween.

[0161] It is appreciated that certain features of the invention, which are, for clarity, described in the context of separate embodiments, may also be provided in combination in a single embodiment. Conversely, various features of the invention, which are, for brevity, described in the context of a single embodiment, may also be provided separately or in any suitable sub-combination or as suitable in any other described embodiment of the invention. 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.

[0162] Various embodiments and aspects of the present invention as delineated hereinabove and as claimed in the claims section below find experimental support in the following examples.

[0163] Examples

[0164] Reference is now made to the following examples, which together with the above descriptions illustrate embodiments of the invention in a non-limiting fashion.Experiments were performed according to embodiments of the present invention to compare the quality of a fabricated object when employing different parameters. An image of one of the fabricated objects is shown in FIG. 9A, which highlights by a black outlined box an area of interest featuring an area transitioning between hatching and periphery.

[0165] In experiment 1, the object's layers included a periphery having three side-by-side polyline borders formed by the same spot size, of about 150 pm, and an inner portion in which the spot size was about 250 pm.

[0166] In experiment 2, the object's layers included a periphery having five side-by-side polyline borders with a spot size gradually decreasing from outer border to inner border, along the inward direction, as illustrated in FIG. 4. The smallest spot size of the five borders (the width of the outermost border) was about 120 pm. The spot size forming the inner portion was about 250 pm as in experiment 1.

[0167] Images of the area of interest (top surface) and equivalent area of interest (bottom surface opposite the top surface) were taken of object for both experiments:

[0168] Images of the object surface from experiment 2, employing the method according to an embodiment of the invention, are shown in FIG. 9B, which is a magnified image of the top surface of the area of interest indicated in FIG. 9A, and in FIG. 9C, which is a magnified image of the bottom surface of an area opposite that of the area of interest indicated in FIG.

[0169] 9A (i.e. facing downwards in FIG. 9A).

[0170] Similarly, magnified images of the object from experiment 1 (i.e. not applying the method of the invention) are shown in FIG. 9D (top surface) and FIG. 9E (bottom surface).

[0171] In these images, circles in black outline indicate specific artefacts seen clearly in the images of experiment 1 but not in of experiment 2. For the object from experiment 1, a visible transition is seen due to a significant variation in the surface profile from the edge of the object across the periphery and to the inner portion in both bottom surface (FIG. 9E) and top surface (FIG. 9D). This is due to significant variation in energy density profile from the object edge inward, leading to partial overcuring and thicker ridges across a surface that should be flat. Meanwhile, applying the method according to an embodiment of the invention, both top surface (FIG. 9B) and bottom surface (FIG. 9C) of the resulting object appear visually flat.

[0172] Although the invention herein has been described in conjunction with specific embodiments thereof, it is evident that many alternatives, modifications and variations willbe 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.

[0173] 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, 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 invention. 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

38CLAIMS1. A method of scanning light in additive manufacturing, the method comprising: receiving position data describing a layer of a three-dimensional object; scanning a liquid film by a beam spot of a light beam according to said position data to form on said film a shape defining said layer; wherein said scanning comprises forming a periphery of said layer by scanning said beam spot along two or more border paths extending within and following an outer contour of said layer; andvarying a beam spot size of said beam spot, by selecting said beam spot size from a set of beam spot sizes such that the beam spot size is increasing inwardly over the two or more paths with respect to the outer contour of said layer.

2. The method according to claim 1, wherein said border paths are closed border paths.

3. The method according to claim 1 or claim 2, wherein the border paths within the periphery extend side by side.

4. The method according to any preceding claim, wherein said varying comprises selecting from said set of beam spot sizes an additional beam spot size for an inner portion of said layer, wherein the inner portion is adjacent to an inward of the periphery.

5. The method according to claim 4, wherein scanning comprises forming said inner portion by scanning the beam spot at the additional beam spot size along a set of inner portion paths.

6. The method according to claim 5, wherein said set of inner portion paths of said inner portion forms a cross-hatch pattern.

7. The method according to any one of claims 3 to 5, wherein said additional beam spot size is larger than a largest beam spot size within said periphery.

8. The method according to any preceding claim, comprising selecting lateral separations between centers of adjacent beam spots based on said set of beam spot sizes.

399. The method according to claim 8, comprising selecting said lateral separations so as to ensure a generally uniform energy density between adjacent beam spots along a pattern formed by said beam spots.

10. The method according to claim 8 or claim 9, wherein for at least two adjacent beam spots, said selecting said lateral separations is so as to ensure that a lateral separation between said adjacent beam spots is from about 0.3 times an average beam spot size to about 0.5 said average beam spot size of said adjacent beam spots.

11. The method according to any preceding claim, comprising varying a power of said light beam, based on said set, wherein for at least two different beam spot sizes within said periphery, different power levels are selected for beam spots having said two different beam spot sizes.

12. The method according to claim 11, wherein the method comprises varying a speed of said scanning, based on said set, wherein different scanning speeds are selected for at least two different beam spot sizes within said periphery.

13. The method according to any preceding claim, comprising receiving a parameter pertaining to one beam spot size of said set of beam spot sizes, and calculating one or more further beam spot sizes of said set based on said parameter.

14. The method according to claim 13, wherein said parameter pertains to a smallest beam spot size of said set of beam spot sizes.

15. The method according to claim 13 or claim 14, comprising displaying a graphical user interface (GUI) having a beam spot size selection control, and wherein said receiving said parameter is according to input received from said beam spot size selection control.

16. The method according to any preceding claim, comprising displaying a graphical user interface (GUI) having a scanning mode selection control, and selecting a default set for said set of beam spot sizes according to input received from said scanning mode selection control.4017. A method of fabricating an object in layers by additive manufacturing, the method comprising:forming a liquid film of a liquid curable by radiation;forming a layer of the object over said liquid film by executing the method according to any of claims 1 to 16; andgenerating a new liquid film contacting said layer in preparation for forming a subsequent layer of the object.

18. A system for scanning light in additive manufacturing, the system comprising: an irradiation system configured to generate a scannable light beam to form a beam spot on a liquid film, the irradiation system being also configured to control a beam spot size of said beam spot; anda computerized controller having a circuit configured to receive position data describing a layer of a three-dimensional object, to control said irradiation system to scan said liquid film by said beam spot according to said position data to form on said liquid film a shape defining said layer, and to control said irradiation system to scan said beam spot along two or more border paths extending within and following an outer contour of said layer, so as to form a periphery of said layer; and to vary said beam spot size by selecting said beam spot size from a set of beam spot sizes so as to ensure that said beam spot size is increased from one border path to the next inwardly with respect to an outer contour of said layer.

19. The system according to claim 18, wherein said border paths within the periphery are closed border paths.

20. The system according to claim 18 or claim 19, wherein the border paths within the periphery extend side by side.

21. The system according to any one of claims 18 to 20, wherein said computerized controller is configured to select from said set of beam spot sizes an additional beam spot size for inner border paths defining an inner portion of said layer, wherein the inner portion is adjacent to and surrounded by the periphery of the layer.

22. The system according to claim 21, wherein said computerized controller is configured to control said irradiation system to scan along the inner border paths at the additional beam spot size so as to form the inner portion of said layer.

23. The system according to claim 21 or claim 22, wherein said additional beam spot size is larger than a largest beam spot size within said periphery.

24. The system according to any of claims 18 to 23, wherein said computerized controller is configured to select lateral separations between centers of adjacent beam spots illuminated by said light beam based on said set of beam spot sizes.

25. The system according to claim 24, wherein said computerized controller is configured to ensure a substantially uniform energy density between adjacent beam spots along a pattern formed by said beam spots.

26. The system according to claim 24 or claim 25, wherein said computerized controller is configured to select said lateral separations to ensure that a lateral separation between said adjacent beam spots is from about 0.3 times an average beam spot size to about 0.5 said average beam spot size of said adjacent beam spots.

27. The system according to any one of claims 18 to 26, wherein said computerized controller is configured to vary a power of said light beam, based on said set of beam spot sizes, wherein different power levels are selected by said computerized controller for at least two different beam spot sizes within said periphery.

28. The system according to any of claims 18 to 27, wherein said computerized controller is configured to vary a speed of said scanning, based on said set of beam spot sizes, wherein different scanning speeds are selected by said computerized controller for at least two different beam spot sizes within said periphery.

29. The system according to any of claims 18 to 28, wherein said computerized controller is configured to receive a parameter pertaining to one beam spot size of said set of beam spot sizes, and to calculate one or more further beam spot sizes of said set based on said parameter.

30. The system according to claim 29, wherein said parameter pertains to a smallest beam spot size of said set of beam spot sizes.

31. The system according to any of claims 18 to 30, comprising a display device, and a computer having a processor configured to display on said display device a graphical user interface (GUI) having a beam spot selection control, to receive from said GUI user responses, and to calculate beam spot sizes of said set according to input received from said beam spot selection control.

32. The system according to any of claims 18 to 30, comprising a display device, and a computer having a processor configured to display on said display device a graphical user interface (GUI) having a scanning mode selection control, to receive from said GUI user responses, and to select said set of beam spot sizes according to input received from said scanning mode selection control.

33. The system according to any of claims 18 to 30, comprising a display device, and a computer having a processor configured to display on said display device a graphical user interface (GUI) having a scanning mode selection control and a beam spot selection control, to receive from said GUI user responses, and, based on an input from said scanning mode selection control, to either: select a default set for said set of beam spot sizes; or calculate beam spot sizes of said set of beam spot sizes according to said input from said beam spot selection control.

34. The system according to any of claims 31 to 33, wherein said GUI comprises an information control, and wherein said processor is configured to analyze a geometry of an external surface of said three-dimensional object, and to display at said information control an indication describing a compatibility between said geometry and a smallest beam spot size of said set of beam spot sizes.

35. A method of generating scanning control data for an irradiation system of an additive manufacturing system, the irradiation system being configured to form, using a light beam,43beam spots on a liquid film in accordance with a shape defining a layer of a three-dimensional object, the method comprising:receiving position data describing an inner portion and a periphery of the layer, wherein said periphery surrounds said inner portion;selecting from a set of beam spot sizes a beam spot size for each of two or more border paths, said border paths extending within and following an outer contour of the layer; wherein the two or more border paths define beam spot scanning locations to form said periphery;such that the selected beam spot sizes within said periphery are increasing inwardly from the outer contour toward said inner portion; andtransmitting scanning control data to a computer readable medium, wherein the scanning control data comprises the selected beam spot sizes.

36. The method according to claim 35, wherein the two or more border paths extend side-by-side.

37. The method according to claim 35 or 36, wherein each border path within the periphery is a closed border path.

38. The method according to any one of claims 35 to 37, comprising selecting from said set of beam spots an additional beam spot size for said inner portion of the layer.

39. The method according to claim 38, comprising associating said additional beam spot size with each beam spot along a set of inner portion paths defining said inner portion.

40. The method according to claim 39, wherein said set of inner portion paths of said inner portion forms a cross-hatch pattern.

41. The method according to any of claims 35 to 40, comprising selecting lateral separations between centers of adjacent beam spots based on said set of beam spots.4442. The method according to claim 41, wherein said selecting said lateral separations is to ensure a substantially uniform energy density between adjacent beam spots along a pattern formed by said beam spots.

43. The method according to claim 41 or claim 42, wherein said selecting said lateral separations is to ensure a substantially uniform energy density between adjacent beam spots along the or a pattern formed by said beam spots, wherein the pattern comprises the inner portion paths.

44. The method according to any one of claims 41 to 43, wherein for at least two adjacent beam spots, said selecting said lateral separations is such that a lateral separation between said adjacent beam spots is from about 0.3 times an average beam spot size to about 0.5 said average beam spot size of said adjacent beam spots.

45. The method according to any one of claims 41 to 44, wherein said selecting said lateral separations comprises selecting lateral separations between adjacent beam spots of the innermost one of the two or more border paths and of the set of inner portion paths.

46. The method according to any one of claims 35 to 45, wherein the scanning control data for the layer comprises a plurality of power levels for the light beam and a plurality of scan speeds for each beam spot size, wherein the method comprises selecting, based on said set of beam spot sizes, said plurality of scan speeds, and selecting, based on said set of beam spot sizes and said scan speeds, the plurality of power levels, to associate different power levels with at least two different beam spot sizes within said periphery.

47. The method according to any one of claims 35 to 46, comprising receiving a parameter pertaining to one beam spot size of said set of beam spot sizes, and calculating other beam spot sizes of said set based on said parameter.

48. The method according to claim 47, wherein said parameter pertains to a smallest beam spot size of said set.4549. The method according to claim 47 or claim 48, comprising displaying a graphical user interface (GUI) having a beam spot size selection control, and wherein said receiving said parameter is according to input received from said beam spot size selection control.

50. The method according to any of claims 35 to 49, comprising displaying a graphical user interface (GUI) having a scanning mode selection control, and selecting a default set for said set of beam spot sizes according to input received from said scanning mode selection control.

51. The method according to any of claims 35 to 50, comprising analyzing a geometry or an outer contour of said layer, displaying a graphical user interface (GUI) having an information control, and displaying at the information control an indication describing a compatibility between said geometry or outer contour and a smallest beam spot size of said set of beam spot sizes.

Images