Method and apparatus for manufacturing an object by stereolithography 3D printing

Abstract

A method for manufacturing an object by stereolithography 3D printing, wherein the object is built layer by layer on a build platform (2) to obtain a structured stack, wherein each structured layer is obtained by curing a photosensitive resin (4) according to a desired pattern, wherein a removable material film, different from the photosensitive resin, is arranged between two adjacent layers, wherein, in a post-processing step, the removable material film is subjected to physical and / or chemical processes that cause the first removable material film to crack or lose its stability and the removable material is removed from the object.

Description

Technical Field

[0001] This invention relates to a method for manufacturing objects using stereolithography 3D printing, wherein the object is built layer by layer on a build platform to obtain a structured layer stack, wherein each structured layer is obtained through the following steps:

[0002] - Provides an unstructured photosensitive resin layer, and

[0003] - Light is selectively projected onto an unstructured layer according to a desired pattern, thereby curing a photosensitive resin to obtain a structured layer structured according to the pattern. Background Technology

[0004] Additionally, the present invention relates to an apparatus for manufacturing objects by stereolithography 3D printing, the apparatus comprising:

[0005] Build a platform

[0006] Material carrier,

[0007] Device for applying an unstructured photosensitive resin layer to a build platform or to a partially constructed object.

[0008] A light engine designed to pattern light onto an unstructured photosensitive resin layer, the light engine being adapted to cure the photosensitive resin to obtain a structured layer structured according to the pattern.

[0009] As used herein, “light” can include any electromagnetic radiation capable of inducing polymerization of the photosensitive resin. The term “light” is not limited to visible light, such as portions of the spectrum perceptible to the human eye. The radiation can have wavelengths in the range of 10 nm to 10,000 nm, preferably 100 to 500 nm.

[0010] The term "photosensitive resin" can refer to a material that conforms to a hardened polymer through a curing process. Photosensitive resins can include, but are not limited to, mixtures of oligomers, photoinitiators, and monomers. Photosensitive resins can also be referred to as uncured photopolymers.

[0011] The process of “curing” photosensitive resin is as follows, in which the photosensitive resin polymerizes or cross-links due to light irradiation.

[0012] As used herein, a “light engine” is a device capable of generating dynamic light information based on a predetermined pattern. As examples, LCD displays, digital light processing (DLP), other active mask projection systems, and / or laser scanner-based systems can be used to selectively project light information onto the surface of a photosensitive resin.

[0013] Compared to other additive manufacturing technologies, commercially available stereolithography (SLA) printers offer high resolution and surface quality. Furthermore, by employing certain process modifications such as heating or thin-film coating (see, for example, EP 3284583 A1 and EP 3418033 A1), it is possible to print highly viscous materials (such as resins) that cannot be handled using any other additive manufacturing technology. These highly viscous materials can result in advanced mechanical properties in parts printed using stereolithography.

[0014] However, current stereolithography processes can only process one material at a time. Another drawback of stereolithography is the necessity of support structures. For both top-down and bottom-up systems, support structures are used to support overhanging portions, undercut sections, or other segments not supported by the main build-up. In stereolithography, the support structures are inherently composed of the same material as the build-up material. Therefore, the support structures cannot be easily removed by cleaning or melting; they must be removed mechanically, and in many cases manually, such as by breaking or cutting, leaving a mark on the surface of that section. Besides the potential damage to the surface, this involves additional time and labor requirements. Especially for sections that require debonding and / or sintering after the printing process, such as ceramic or metal-filled photopolymers, manual removal of the support structures is time-consuming, labor-intensive, and tool-intensive, and increases the risk of further damage to that section during the process chain.

[0015] Other additive manufacturing technologies, such as inkjet printing or fusion filament fabrication (FFF), can process multiple materials at once. These systems can typically provide a support material for printing the support structure, which is inherently different from the building material. Several methods exist for removing this support material, including melting it or using a solvent to wash it away. This allows the support material to be removed without damaging the surface of the printed portion. However, printing systems for fusion filament fabrication currently lack the accuracy, layer tack, and surface quality necessary for most industrial applications. On the other hand, inkjet printing technology has significant limitations regarding the viscosity parameters of the photosensitive resin, due to the fluid limitations of the available printhead; the viscosity parameter is typically limited to approximately 20 mPa·s. This has a significant impact on the achievable mechanical properties, as low-viscosity monomers are generally characterized by short polymer chains and form dense polymer networks, resulting in fragile polymer portions.

[0016] To overcome certain limitations of the printing process, different printing strategies can be combined. There are approaches that combine thermoplastic (FFF) with photopolymers from inkjet printheads (e.g., US 10486364 B2) and SLA systems and inkjet printheads (e.g., US 10486364 B2, US 10449715 B2, US 2015 / 131074 A1) for coloring purposes. Multi-material approaches for SLA typically involve multiple barrels, each with a different resin (e.g., US2017 / 100899 A1). However, these approaches often suffer from cross-contamination issues between different materials. Summary of the Invention

[0017] The objective of this invention is to improve stereolithography-based printing methods and apparatus to allow for the placement of support structures that can be easily and controllably removed in post-processing steps without damaging the surface of the printed object.

[0018] To address this and other objectives, the present invention, in its first aspect, provides a method for manufacturing an object by stereolithography 3D printing, wherein the object is built layer by layer on a build platform to obtain a structured layer stack, wherein each structured layer is obtained through the following steps:

[0019] - Provides an unstructured photosensitive resin layer, and

[0020] - Light is selectively projected onto the unstructured layer according to the desired pattern, thereby curing the photosensitive resin to obtain a structured layer structured according to the pattern.

[0021] The structured layer stack includes a first pair of adjacent structured layers.

[0022] In this process, unlike photosensitive resin, a first removable material film is placed onto the first structured layer of the first pair of adjacent structured layers by spraying a drop of removable material from an ejector. Subsequently, a second structured layer of the first pair of adjacent structured layers is constructed on the first removable material film, thereby distributing the first removable material film between the first and second structured layers of the first pair of adjacent structured layers.

[0023] In the post-processing step, the first removable material film undergoes physical and / or chemical processes that cause the first removable material film to crack or lose its stability, and the removable material is removed from the object.

[0024] This invention utilizes a stereolithography-based printing process that allows for the processing of mechanically advantageous photopolymers, and is based on the concept of selectively adding removable materials during the printing process. Specifically, the invention is based on the concept of arranging removable material films between structured, cured photosensitive resin layers, thereby providing temporary interfaces between different parts of the 3D-printed object that can be easily separated and removed in post-processing steps. Such removable interfaces can be used to separate the 3D-printed object into two or more parts, or to remove support structures from the object without negatively affecting its surface.

[0025] Since the removable material is not the same material as the photosensitive resin, the post-processing steps for removing the removable material can be designed to be processes that only react with the removable material, thereby leaving the cured photosensitive resin unaffected. In particular, the post-processing steps are designed to subject the removable material film to physical and / or chemical processes that cause the first removable material film to crack or lose its stability.

[0026] According to a preferred embodiment, the physical and / or chemical processes are selected from the group consisting of melting, evaporation, sublimation, expansion, and dissolution in a solvent. Thus, the post-processing step utilizes the different physical and / or chemical properties of the cured photosensitive resin and the removable material, and applies physical and / or chemical processes that produce splitting reactions (such as melting, evaporation, sublimation, expansion, and dissolution in a solvent) only in the removable material and not in the cured photosensitive resin.

[0027] As mentioned in the introduction, the use of multiple materials in stereolithography typically requires the use of multiple material reservoirs, such as barrels, with one reservoir for each material. The build platform, or at least the object built upon it, is alternately immersed in these reservoirs. However, this leads to cross-contamination between different materials because when an object is immersed in a second material, an uncured amount of the first material still adheres to the object after the structured layer of the first material has been transferred to the second material, and vice versa.

[0028] To avoid cross-contamination between two different materials, the removable material is applied to the structured layer made of photosensitive resin by an ejector that sprays droplets of the removable material. Specifically, the droplets are selectively placed at one or more locations on the structured layer, where a removable interface is required to achieve the desired function. Preferably, the ejector is designed as an inkjet printhead or as a nozzle or microdroplet dispenser.

[0029] An interface made of removable material can be used to separate selected portions of the cured photosensitive resin from the 3D-printed object. The removable interface is advantageous on both sides if the selected portions to be removed are defined by structured layers on both the upper and lower sides. Therefore, a preferred embodiment of the invention provides that the structured layer stack includes a second pair of adjacent structured layers.

[0030] In this process, a second removable material film, unlike photosensitive resin, is placed onto the first structured layer of the second pair of adjacent structured layers by spraying droplets of removable material from an ejector. Subsequently, the second structured layer of the second pair of adjacent structured layers is constructed on the second removable material film, thereby distributing the second removable material film between the first and second structured layers of the second pair of adjacent structured layers.

[0031] In the post-processing step, the second removable material film undergoes physical and / or chemical processes that cause the second removable material film to crack or lose its stability, and the removable material is removed from the object.

[0032] An important application of this invention is the removal of support structures printed during the manufacture of an object to support overhanging portions or undercuts. This removal is achieved by defining the support structure on its upper and lower sides using removable material films. Therefore, a preferred embodiment of the process of this invention provides that a support structure composed of photosensitive resin is generated between a first removable material film and a second removable material film, wherein, in a post-processing step, the support structure is removed from the object.

[0033] Alternatively, in addition to a support structure defined by a structured layer on both its upper and lower sides (each side having a removable material film), the support structure can also be arranged between the structured layer of the object and the construction platform. Here, a preferred embodiment of the process of the present invention is provided as follows: a support structure composed of photosensitive resin is generated between a first removable material film and the construction platform, wherein, in a post-processing step, the support structure is removed from the object.

[0034] To facilitate separation between the support structure and the construction platform, a third removable material film can be placed on the construction platform by spraying droplets of removable material from an ejector before the first structured photosensitive resin layer is constructed onto the platform. In this way, an additional interface made of removable material is created between the construction platform and the support structure.

[0035] The support structure can fill the entire space below the overhang or undercut. However, to minimize the amount of photosensitive resin required to construct the support structure, it may include multiple support elements, such as multiple columns.

[0036] As is commonly practiced in stereolithography 3D printing, the support structure is constructed simultaneously with the actual object, such that the preferred embodiment provides the following: the support structure is constructed from multiple cured photosensitive resin layers. Therefore, segments of the pattern can each be used to construct the support structure layer by layer.

[0037] According to a particularly preferred embodiment, removable material films are each disposed between the cured photosensitive resin layer and the support structure. In this manner, the support structure consists of alternating segments made of cured photosensitive resin and segments made of removable material. In other words, the support structure is divided into at least two segments by at least one removable material film. During post-processing steps, when the removable material splits or loses its stability, the support structure separates or collapses into at least two segments, i.e., smaller portions that can be more easily removed. This allows the support structure to be removed from hard-to-reach areas of the object or from cavities of the object. Furthermore, this method allows the removal of the support structure to be integrated into automated post-processing and cleaning steps, as the removal is highly independent of the geometry of the printed portion.

[0038] In addition, this enables the creation of movable joints, gears, or other types of bearings or moving solutions within a single print job, or even within a group of components that cannot be disassembled after printing, between parts, sub-parts, or groups of components.

[0039] As for the properties of the removable material, any material that can be applied by a sprayer as a droplet and that differs from the cured photosensitive resin in at least one physical and / or chemical property (such as melting point, solubility, boiling point, etc.) can be used.

[0040] Preferably, the removable material is a polymerizable material that is soluble or swellable in a solvent in its polymerized and prepolymerized states. Therefore, such a material may consist of at least polymerizable groups (such as acrylates, methacrylates, acrylamides, vinyl ethers or vinyl esters, maleimides, cyclic ethers, isocyanates, amines) or other polymerizable unsaturated or saturated groups, and may optionally further include at least one hydrophilic or lipophilic group. The polymerizable material may be soluble or swellable in solvents such as water, alcohol, oil, or other organic solvents. Such materials include, for example, hydroxyl groups, carbonyl groups, and carboxyl groups, as well as derivatives having other electronegative heteroatoms, amines, ionic liquids, and salts, such as ethyl hydroxymethyl acrylate (HEMA), 2-(2-ethoxyethoxy)ethyl acrylate (EOEOEA), acrylmorpholine (ACMO), polyethylene glycol derivatives, polyethers, hydroxyethyl acrylate, or lauryl acrylate.

[0041] According to an alternative preferred embodiment, the removable material is solidified and fusible after the printing process, and is therefore a material with a melting point (such as a melting point of <200°C) below the decomposition temperature of the cured photosensitive resin, such as a long-chain alcohol or wax.

[0042] To improve the adhesion of removable materials to cured photosensitive resin, the structured layer can be pretreated by means of surface conditioning (e.g., plasma treatment or corona treatment) before the droplets of removable material are sprayed from the ejector onto the structured layer.

[0043] Since the removable material is applied to the cured photosensitive resin layer in liquid form, a preferred embodiment provides that the removable material film is solidified before the structured layer is formed on it. Preferably, the removable material film undergoes a drying step, a solidification step, or a photocuring step before the structured layer is formed on it. Alternatively, the removable material film undergoes hardening or curing via a chemical reaction process triggered by an ambient gas such as ambient air or a special process gas or process atmosphere, or by contact with a second removable material compound that can be sprayed by an additional injector device. In another approach, the removable material film remains liquid on top of the surface of the cured photosensitive resin layer and can subsequently be cured at least partially by forming an electromagnetic radiation pattern for the next layer of cured photosensitive resin. In an alternative approach, the removable material film continues to remain liquid on top of the surface of the cured photosensitive resin layer and even between multiple cured photosensitive resin layers. However, in such a configuration, the viscosity of the removable material film can vary or remain the same throughout the printing process, and may be affected by its physical (e.g., process temperature) or chemical (e.g., the surrounding gaseous atmosphere) process environment in terms of its viscosity.

[0044] Additionally, the structured layer can be structured to have cavities into which droplets of removable material are ejected from the ejector. This improves the positioning of the removable material at the desired location.

[0045] According to another aspect of the present invention, an apparatus for manufacturing an object by stereolithography 3D printing is provided, comprising:

[0046] Build a platform

[0047] Material carrier,

[0048] Device for applying an unstructured photosensitive resin layer to a build platform or to a partially constructed object.

[0049] A light engine, designed to pattern light onto an unstructured photosensitive resin layer, is adapted to cure the photosensitive resin to obtain a structured layer structured according to the pattern.

[0050] An injector used to spray droplets of removable material onto a structured layer to obtain a removable material film.

[0051] The drive mechanism is used to change the relative positions of the construction platform, light engine, and jets.

[0052] A control unit, adapted to control actuation devices, such that in a first relative position, a construction platform and an object at least partially constructed thereon are assigned to a light engine to construct a structured layer, and in a second relative position, the construction platform and the object at least partially constructed thereon are assigned to an ejector to apply a removable material film onto the structured layer.

[0053] The control unit is configured and programmed to change between a first position and a second position according to a predetermined sequence, such that a first removable material film is placed on a first structured layer of a first pair of adjacent structured layers, and thereafter a second structured layer of the first pair of adjacent structured layers is constructed on the first removable material film, thereby arranging the first removable material film between the first structured layer and the second structured layer of the first pair of adjacent structured layers.

[0054] Preferably, the control unit is configured and programmed to change between a first position and a second position according to a predetermined sequence, such that a second removable material film is placed on a first structured layer of a second pair of adjacent structured layers, thereafter a second structured layer of the second pair of adjacent structured layers is constructed on the second removable material film, thereby arranging the second removable material film between the first and second structured layers of the second pair of adjacent structured layers.

[0055] Preferably, the control unit is configured and programmed to change between a first position and a second position according to a predetermined sequence, such that a support structure consisting of at least one structured photosensitive resin layer is generated between a first removable material film and a second removable material film.

[0056] Preferably, the control unit is configured and programmed to change between a first position and a second position according to a predetermined sequence, such that a support structure consisting of at least one structured photosensitive resin layer is generated between the first removable material film and the construction platform.

[0057] Preferably, the control unit is configured and programmed to change between a first position and a second position according to a predetermined sequence, such that a third removable material film is placed on the construction platform before the first structured photosensitive resin layer is constructed on the construction platform.

[0058] Preferably, the control unit is configured and programmed to change between a first position and a second position according to a predetermined sequence, such that the support structure consists of multiple structured photosensitive resin layers.

[0059] Preferably, the control unit is configured and programmed to change between a first position and a second position according to a predetermined sequence, such that each of the removable material films is arranged between the plurality of structured layers of the support structure. Attached Figure Description

[0060] The present invention will now be described in more detail with reference to specific preferred embodiments thereof.

[0061] Figure 1 An example of a material placement strategy for a bottom-up stereolithography process is shown.

[0062] Figure 2 An example of a material placement strategy for a top-down stereolithography process is shown.

[0063] Figure 3a A side view shows a material placement strategy for a stereolithography printing process utilizing a movable SLA printhead.

[0064] Figure 3b A top view showing a material placement strategy for a stereolithography printing process utilizing a movable SLA printhead.

[0065] Figure 4 The illustration shows the printed portion with a cantilever structure.

[0066] Figure 5a The illustration shows the printed portion of the support structure inside the cavity.

[0067] Figure 5b Show in more detail Figure 5a The contact area.

[0068] Figure 6 An exemplary portion with movable segments is shown.

[0069] Figure 7 The illustration shows an example of material placement inside the support structure.

[0070] Figure 8 An exemplary support structure geometry in the interface area between the illustrated portion and the support structure.

[0071] Figure 9 A flowchart of the printing process is shown. Detailed Implementation

[0072] This invention is a method for additively manufacturing portions to facilitate the removal of support structures by selectively exposing filled or unfilled photosensitive resin to light using an additional phase of selectively placed removable material. Stereolithography printing systems allow for the treatment and selective curing of photosensitive resins of various viscosities (preferably, dynamic viscosities between 0.1 Pa·s and 20 Pa·s) at predefined process temperatures, wherein fillers are present or absent, and the material used for the printed portion itself is the same as the material used for the necessary support structures. To overcome the limitation of conventionally available printers to only one material, multi-material stereolithography printing is achieved by integrating a droplet generation device (e.g., inkjet printhead, nozzle, or pipette) into the printing process, which can selectively place at least one additional material, including multiple additional materials. This invention, which introduces removable material as a second or additional phase into the printed object, can be applied to all types of stereolithography printing processes. Figure 1 and Figure 2 Schematic illustrations of two different stereolithographic printing processes are shown, illustrating the implementation of an ejector to add such a second or additional material phase. In addition to the ejector for ejecting droplets, the unit moving on the pre-cured layer can also include a light source, such as an LED or UV lamp, to cure or fix selectively placed droplets, droplet arrays, or surface-wetting droplet layers. Additionally, it can include a heat source to dry the placed material and / or to dry the substrate and / or to perform controlled or uncontrolled evaporation. It may be necessary to treat (or prepare, i.e., prepare) the substrate (pre-cured layer) using, for example, a wiping blade or a defined flow or gas stream of air at a defined temperature for drying / cleaning the surface. Further advantageously, surface conditioning treatments of the layer surface, such as plasma treatment or corona treatment, can be used to allow defined droplet placement (e.g., defining or influencing the wetting and bonding behavior of the droplet material on the printed layer substrate).

[0073] Figure 1This is a schematic illustration and example of a multi-material bottom-up stereolithography printing process 100. The printer consists of a build platform 2, which can rotate between positions 101, 102, and 103 according to arrow 7. In position 101, a transparent barrel 5 is filled with photosensitive resin 4. The height of this material can be within the range of a printed layer thickness of several millimeters. A coating machine 8 can be installed to coat the barrel with new photosensitive resin 4. The build platform 2 is lowered into the photosensitive resin until the desired layer height between the build platform 2 (or the portion 1 partially built on it) and the barrel 5 is reached. A curing system 6 cures the photosensitive resin 4 through the transparent barrel 5. This can be, for example, a dynamic mask system using one or more LEDs as a light source, a laser scanning system, or an LCD or other actively or passively exposed display. After curing, the build platform 2 is raised, and the barrel 5 can be coated again. By repeating these steps, the three-dimensional portion 1 is printed. For certain structures such as overhangs or cavities, a support structure 3 is necessary. The support structure can be divided into different sections, including section 31 printed from photosensitive resin, section 32 printed from removable material (such as soluble, expandable, fusible, vaporizable and / or sublimable material), and interface section 33 between part 1 and support structure 3 (see Figure 5b To print sections 32 and 33, a motor is capable of rotating the printed portion 1 to a desired position (arrow 7). In exemplary positions 102 or 103, a droplet generating device 9 (e.g., an inkjet printhead or pipette) or a heated nozzle moves across the surface of portion 1 and places removable material at the selected area. A UV or visible light source 10, matched to the photoinitiator in the removable material, is capable of curing the material to fix it in place. Alternatively, a heat source 11 (e.g., an infrared lamp or halogen lamp) is capable of drying the removable material or evaporating its components (e.g., solvents). If necessary, a wiper or blade 12 or a defined flow or airflow of air at a defined temperature can move across the surface of portion 1 to wipe / blow away excess removable material and treat the substrate to be injected onto it. To improve the wettability and adhesion of the cured photosensitive resin surface of portion 1 before placing the removable material, a surface treatment device 13, such as a corona treatment device or a plasma treatment device, can be installed. After the removable material is placed, the construction platform 2 is rotated back to position 101, where the next layer of part 1 is cured, the layer also forming one or more sections 31 of the support structure.

[0074] Figure 2The diagram illustrates a multi-material top-down printing process 200. A build platform 2 is immersed in a bucket 5 filled with photosensitive resin 4. At position 201, a curing system 6 cures the photosensitive resin 4 from above. This can be, for example, a dynamic mask system using LEDs as a light source, a laser scanning system, or an LCD or other actively or passively exposed display. After curing, the build platform 2 is immersed in liquid resin, and a coating machine 8 or blade can cover the printed portion with the next layer of uncured resin. By repeating these steps, a three-dimensional portion 1 is printed. For certain structures such as overhangs or cavities, a support structure 3 is necessary. The support structure can be divided into different sections, including a section 31 printed from the photosensitive resin 4, a section 32 printed from a removable material (such as a soluble, expandable, or fusible material), and an interface section 33 between portion 1 and the support structure 3. To print sections 32 and 33, after the layer has cured, a droplet generating device 9 (e.g., an inkjet printhead or pipette) or a heated nozzle moves to position 202 on the surface of section 1 and places removable material in the selected area. A UV or visible light source 10, matched to the photoinitiator in the removable material, can cure the material to fix it. A heat source 11 (e.g., an infrared lamp or halogen lamp) can dry the removable material. Before placing the removable material, a wiper or blade 12 or a defined flow of air or gas can remove any residue of uncured resin. To improve surface quality, a surface treatment device 13 (e.g., a corona treatment device or a plasma treatment device) can move on the surface of section 1.

[0075] Figure 3aThe illustration shows a side view of an exemplary stereolithography process utilizing a movable printhead 15. A portion 1 is printed onto a build platform 2 that is vertically movable along the z-direction. Photosensitive resin 4 is applied and cured by the printhead 15, which is capable of horizontal movement along the x-direction. The printhead 15 includes a circulating foil or rolling foil that acts as a transfer medium for transferring liquid photosensitive resin onto the build platform 2. A curing device 16 (e.g., a laser scanner, dynamic mask system, or LED module) selectively cures the resin transferred from inside the printhead 15 through the foil. Behind the printhead 15, a droplet ejection device 9 (e.g., an inkjet printhead or pipette) or a (heatable) nozzle is movable on the build platform 2 and selectively places removable materials that are soluble, expandable, fusible, sublimable, or evaporable. A UV or visible light source 10, matched to an optional photoinitiator in the removable material, can cure the removable material to fix it in place. A heat source 11 (e.g., an infrared lamp or halogen lamp) can dry the removable material. The surface of part 1 can be treated by a wiper or blade 12 or by a defined flow or airflow of air at a defined temperature and / or a surface treatment device 13 (e.g., a corona treatment device or a plasma treatment device). The droplet generating device 9, the visible light source 10, and the heat source 11 are attached to the printhead 15 or can be moved independently.

[0076] Figure 3b The illustration shows a top view of an exemplary stereolithography process having one or more movable printheads 15 for multi-pass printing. A droplet generating device 9 is mounted on the printhead 15, or is movable independently and additionally in the y-direction, to scan a larger build area on the build platform 2. A visible light source 10 and a heat source 11 are positioned correspondingly in front of and behind the droplet generating device 9. To treat the surface of the printed portion 1 before placing removable material, a wiper or blade, or a defined flow or gas stream of air at a specific temperature, can be used, and the surface can be treated using surface treatment devices 13 (e.g., corona treatment equipment or plasma treatment equipment) correspondingly positioned in front of and behind the droplet generating device.

[0077] Figure 4The diagram shows a printed portion 300 with overhanging sections attached to a build platform 2. These overhanging sections require a support structure 3 to be printed via stereolithography. The support structure 3 is printed from the same photosensitive resin material as portion 1. Removable material, which may be soluble, expandable, fusible, evaporable, and / or sublimable, is placed and solidified in the interface section 33 between the support structure 3 and portion 1 and / or in the interface section 34 between the build platform 2 and the support structure 3. Following the printing process, the portion undergoes post-processing. To remove the support structure 3 from the printed portion 1 and / or remove portion 1 from the build platform 2, portion 1 and / or the entire build platform 2 can be heated or cooled and / or immersed in a suitable solvent. This allows the removable material in sections 33 and / or 34 to be destabilized, thereby removing the support structure 3 from portion 1 without damaging the surface of the printed portion 1. Furthermore, it prevents the build platform 2 from scratching, which would otherwise occur due to the manual removal of portion 1. Furthermore, the removal of the support structure 3 or its disassembly from the build platform 2 can be integrated into automated post-processing (e.g., UV or thermal post-curing) or cleaning steps. This can save a significant amount of time, effort, and manual labor.

[0078] Figure 5a The illustration shows a portion 400 with a partially inaccessible cavity, which requires a support structure 3 to be printed via stereolithography. The support structure 3 consists of a cured photosensitive resin layer / segment 31 and a removable material layer / segment 32 (such as a soluble, expandable, fusible, evaporable, and / or sublimable material), and as shown in... Figure 5b As seen in the image, it is attached to part 1 via interface segment 33. Figure 5b Segment X is shown in more detail. Inaccessible cavities or overhangs of the support structure 3 to be printed can be supported by the support structure 3 consisting of alternating layers of cured photosensitive resin / segment 31 and removable material / segment 32. During post-processing after printing, the removable material in segment 32 is dissolved, expanded, melted, evaporated, or sublimated. In this way, the support structure 3 can be divided into smaller sections, which can then be washed or blown out from cavities or from hard-to-access or mechanically inaccessible areas.

[0079] Figure 6 The illustration shows a portion 500 intended to accommodate a movable insert (e.g., a shaft). A movable portion 502 is fitted inside a printed portion 501 and is detached from portion 501 by a removable material segment 503. Segment 503 can be removed from the printed portion 500 after the printing process, during a post-processing step, when the removable material in segment 503 is removed (e.g., dissolved, expanded, melted, evaporated, or sublimated).

[0080] Figure 7 The illustrations show different examples of placing removable material within a support structure 3. Part 1 is printed from photosensitive resin and attached to the support structure 3. During the layer-by-layer construction of part 1, the base section 31 of the support structure 3 can be constructed from the same photosensitive resin material as part 1. Using a dripping device, drips of removable material are introduced into the support structure 3 to create section 32 within the support structure 3. Depending on the size of the support structure 3, its material properties, the compatibility of the photosensitive resin with the removable material, surface tension, etc., different geometries of the interface section 33 may be necessary. The support structure 3 can be removed from part 1 by melting, dissolving, expanding, evaporating, or sublimating the removable material. Example 601 shows a cavity 17 in the base section 31 of the support structure 3 to place a larger amount of removable material in the interface section 33 and utilize the rheological properties of the removable material. In Example 602, several alternating layers of photosensitive resin material (segment 31) and a removable material layer (segment 32) are located in the interface region, for example, to increase the amount of removable material in the interface region. In Example 603, multiple layers of photosensitive resin material (segment 31) are separated by a removable material layer (segment 32). Those support structures 3 can be reduced in size by dissolving, expanding, melting, evaporating, or sublimating the removable material in segment 32.

[0081] Figure 8 Further examples of the geometry in the interface region between the building part 1 and the support structure 3 are shown. The base segment 31 of the support structure 3 is composed of the same photosensitive resin material as the building part 1. Segments 32 and / or 33 made of removable material are selectively placed onto or between segments 31(1) via a droplet generating device (e.g., an inkjet printhead or nozzle). The removable material can be cured by a light source or dried by an airflow or ambient atmosphere after application. Alternatively, the removable material can remain in its original liquid form or a slightly modified liquid form or solidify. Figure 8 The illustrations show various designs of sections 32 and / or 33 made of removable material.

[0082] a. Support structure 3 ends on a flat surface. Removable material is placed on this surface.

[0083] b. The support structure 3 has a circular cavity 17 and / or a flat cavity 17 to place a larger amount of removable material in the interface section 33.

[0084] c. The support structure 3 has an angled cavity 17 and / or a deep cavity 17 to place a larger amount of removable material in the interface section 33.

[0085] d. In addition to the interface area, (one or more) segments 32 are also placed between several layers (segments 31) of the supporting structure.

[0086] e. Detailed view of illustration (b).

[0087] f. The support structure 3 has a tapered cavity 17 to place a larger amount of removable material in the interface section 33. In this way, the amount of photosensitive resin is reduced relative to the amount of removable material in the interface region.

[0088] g. Selectively placed drips of removable material were not connected.

[0089] h. Section 31 of the support structure 3 is separated by section 32 made of removable material.

[0090] i. Section 31 of the support structure 3 is separated by section 32 made of removable material, wherein the sections 32 are interconnected along the construction direction by removable material.

[0091] Figure 9 A flowchart of the printing process is shown. First, a CAD file must be generated and sliced ​​(or cut) into defined layer thicknesses. If a hybrid support structure is advantageous, two options exist. Option 1 is to generate a second CAD file for the support structure, which will be sliced ​​accordingly and printed using a second material. Option 2 is to define certain layers of an existing stack of layers, which will be used a second time by a second printing system. Layer information needs to be provided in a file format suitable for the stereolithography section and the droplet generation apparatus (e.g., BMP and PNG, respectively). If the base layer is preferred, image information must be provided in a suitable file format. After the stereolithography layer has cured, the surface may need to be treated for injection. This includes wiping, drying, or certain surface activation processes, such as plasma treatment or corona treatment. After the droplets are selectively placed by one or more droplet generation devices (e.g., inkjet printheads or (heatable) nozzles), the droplets may need to be cured or fixed. For this purpose, a light source or heat source of suitable wavelength (e.g., an IR lamp) or a device for generating airflow can be mounted behind the injection device. Then, a layer of liquid photosensitive resin is placed and cured (stereolithography).

Claims

1. A method of manufacturing an object by stereolithography 3D printing, wherein, The objects are built layer by layer on the construction platform to obtain a structured layer heap, wherein each structured layer is obtained through the following steps: - Provides an unstructured photosensitive resin layer, and - Light is selectively projected onto the unstructured layer according to a desired pattern, thereby curing the photosensitive resin to obtain the structured layer structured according to the pattern. The structured layer stack includes a first pair of adjacent structured layers. In this process, at least a first removable material film, different from the photosensitive resin, is placed onto the first structured layer of the first pair of adjacent structured layers by spraying droplets of the removable material from an ejector. Subsequently, a second structured layer of the first pair of adjacent structured layers is constructed on the first removable material film, thereby distributing the first removable material film between the first structured layer and the second structured layer of the first pair of adjacent structured layers. In the post-processing step, the first removable material film undergoes physical and / or chemical processes that cause the first removable material film to crack or lose its stability, and the removable material is removed from the object.

2. The method of claim 1, wherein, The physical and / or chemical processes are selected from the group consisting of melting, evaporation, sublimation, expansion, and dissolution in a solvent.

3. The method of claim 1, wherein, The structured layer stack includes a second pair of adjacent structured layers. In this process, a second removable material film, unlike the photosensitive resin, is placed onto the first structured layer of the second pair of adjacent structured layers by spraying droplets of the removable material from an ejector. Subsequently, the second structured layer of the second pair of adjacent structured layers is constructed on the second removable material film, thereby distributing the second removable material film between the first and second structured layers of the second pair of adjacent structured layers. In the post-processing step, the second removable material film undergoes physical and / or chemical processes that cause the second removable material film to crack or lose its stability, and the removable material is removed from the object.

4. The method of claim 3, wherein, A support structure composed of the photosensitive resin is formed between the first removable material film and the second removable material film, wherein, in the post-processing step, the support structure is removed from the object.

5. The method according to claim 1, wherein, A support structure composed of the photosensitive resin is generated between the first removable material film and the construction platform, wherein, in the post-processing step, the support structure is removed from the object.

6. The method according to claim 5, wherein, Before the first structured photosensitive resin layer is constructed on the construction platform, a third removable material film is placed on the construction platform by spraying droplets of the removable material from an ejector.

7. The method according to claim 4 or 5, wherein, The support structure includes multiple columns.

8. The method according to claim 4 or 5, wherein, The support structure is constructed from multiple layers of cured photosensitive resin.

9. The method according to claim 8, wherein, Each removable material film is arranged between the cured photosensitive resin layers.

10. The method according to claim 4 or 5, wherein, Each segment of the pattern is used to construct the support structure layer by layer.

11. The method according to claim 1 or 2, wherein, The post-processing steps are performed after the layer-by-layer construction of the object is completed.

12. The method according to claim 1 or 2, wherein, The removable material comprises at least polymerizable groups, wherein the removable material in its polymerized or prepolymerized state is soluble and / or expands in a solvent.

13. The method according to claim 1 or 2, wherein, The removable material is a material having a melting point lower than the decomposition temperature of the cured photosensitive resin.

14. The method according to claim 13, wherein, The removable material is a long-chain alcohol or wax.

15. The method according to claim 12, wherein, The removable material comprises at least polymerizable groups and at least one hydrophilic or lipophilic group, wherein the removable material in its polymerized or prepolymerized state is soluble and / or swells in a solvent.

16. The method according to claim 12, wherein, The polymerizable group is selected from acrylates, methacrylates, acrylamides, vinyl ethers, vinyl esters, maleimides, cyclic ethers, isocyanates, amines, or other polymerizable unsaturated or saturated groups.

17. The method of claim 12, wherein the removable material comprises hydroxyl groups, carbonyl groups, and carboxyl groups, as well as derivatives having other electronegative heteroatoms, amines, ionic liquids, and salts.

18. The method of claim 17, wherein the removable material comprises ethyl hydroxymethacrylate (HEMA), 2-(2-ethoxyethoxy)ethyl acrylate (EOEOEA), acrylmorpholine (ACMO), polyethylene glycol derivatives, polyethers, hydroxyethylene, or lauryl acrylate.

19. The method according to claim 1 or 2, wherein, Before the droplets of the removable material are sprayed from the injector onto the structured layer, the structured layer is pretreated by means of a surface conditioning process.

20. The method according to claim 19, wherein, Before the droplets of the removable material are sprayed from the ejector onto the structured layer, the structured layer is pretreated by a surface conditioning process involving plasma treatment or corona treatment.

21. The method according to claim 1 or 2, wherein, Before the structured layer is constructed on the removable material membrane, the removable material membrane undergoes a drying step, a solidification step, or a photocuring step.

22. The method according to claim 1 or 2, wherein, The structured layer is structured to have cavities into which the droplets of the removable material are ejected from the ejector.

23. An apparatus for manufacturing an object by stereolithography 3D printing, comprising: Build a platform Material carrier, Device for applying an unstructured photosensitive resin layer to the build platform or to a partially built object. A light engine, designed to pattern light onto the unstructured photosensitive resin layer, is adapted to cure the photosensitive resin to obtain a structured layer structured according to the pattern. An injector is used to spray droplets of removable material onto the structured layer to obtain a removable material film. A driving mechanism for changing the relative positions of the building platform, the light engine, and the ejector. A control unit, adapted to control the driving device such that, in a first relative position, the building platform and the object at least partially built thereon are assigned to the light engine to build the structured layer, and in a second relative position, the building platform and the object at least partially built thereon are assigned to the ejector to apply a removable material film onto the structured layer. The control unit is configured and programmed to change between a first position and a second position according to a predetermined sequence, such that a first removable material film is placed on a first structured layer of a first pair of adjacent structured layers, and thereafter a second structured layer of the first pair of adjacent structured layers is constructed on the first removable material film, thereby arranging the first removable material film between the first structured layer and the second structured layer of the first pair of adjacent structured layers.

24. The apparatus according to claim 23, wherein, The control unit is configured and programmed to change between the first position and the second position according to a predetermined sequence, such that the second removable material film is placed on the first structured layer of the second pair of adjacent structured layers, thereafter the second structured layer of the second pair of adjacent structured layers is constructed on the second removable material film, thereby arranging the second removable material film between the first structured layer and the second structured layer of the second pair of adjacent structured layers.

25. The apparatus according to claim 24, wherein, The control unit is configured and programmed to change between the first position and the second position according to a predetermined sequence, such that a support structure consisting of at least one photosensitive resin structured layer is generated between the first removable material film and the second removable material film.

26. The apparatus according to claim 23, wherein, The control unit is configured and programmed to change between the first position and the second position according to a predetermined sequence, such that a support structure consisting of at least one photosensitive resin structured layer is generated between the first removable material film and the construction platform.

27. The apparatus according to claim 26, wherein, The control unit is configured and programmed to change between the first position and the second position according to a predetermined sequence, such that a third removable material film is placed on the construction platform before the first structured photosensitive resin layer is constructed on the construction platform.

28. The apparatus according to claim 25 or 26, wherein, The control unit is configured and programmed to change between the first position and the second position according to a predetermined sequence, such that the support structure consists of a plurality of the photosensitive resin structured layers.

29. The apparatus according to claim 25 or 26, wherein, The control unit is configured and programmed to change between the first position and the second position according to a predetermined sequence, such that each of the removable material films is arranged between the plurality of structured layers of the support structure.

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