WO2022003661A1

WO2022003661A1 - A system and method for three-dimensional (3d) printing

Info

Publication number: WO2022003661A1
Application number: PCT/IL2021/050436
Authority: WO
Inventors: Eyal Shelef; Jon DONNER; Hotam LEYZEROVICH; Gal MILSHTEIN; Tal SELA; Tovit NIZER; Assaf GREEN; Yaniv GERSHONI
Original assignee: Nanofabrica Ltd.
Priority date: 2020-06-30
Filing date: 2021-04-18
Publication date: 2022-01-06

Abstract

A method for a three-dimensional (3D) printing includes obtaining a 3D model for printing, the 3D model comprised of a plurality of horizontal layers each horizontal layer being comprised of pixels; analyzing, a given layer, to identify one or more reinforcement areas comprised of reinforcement pixels of the pixels, wherein each given reinforcement area of the reinforcement areas is: (a) associated with a full projection pattern so that the reinforcement pixels are projection pixels, (b) corresponds to an area, within a preceding layer preceding the given layer, that includes projection pixels only, and (c) located at a distance higher than a threshold from the no-projection pixels, within the layer and within the preceding layer; causing, a projector to project the projection pixels of the given layer; after completion of a given layer, moving a movable stage, to enable printing of a subsequent layer of the horizontal layers.

Description

A SYSTEM AND METHOD FOR THREE-DIMENSIONAL (3D)

PRINTING

TECHNICAL FIELD

The invention relates to a system and method for three-dimensional (3D) printing.

BACKGROUND

3D printing techniques (otherwise known as additive manufacturing, rapid prototyping, or layered manufacturing) enable fabrication of customized/complex objects without the need for molds or machining. The strategy behind the 3D printing techniques (also known as 3D photopolymerization) is based on using monomers/oligomers in a liquid state that can be cured/photopolymerized upon exposure to light source of specific wavelength and form thermosets.

Stereolithography, is one of several technologies used to create 3D-printed objects. These technologies differ mainly by the light source they use. Digital Light Processing (DLP) is one descendant of SLA (Stereolithographic Apparatus) known in the art. The DLP technique utilizes a digital micromirror device (DMD) or a panel of micrometer-sized LED lights.

Typically, DLP printers have four main parts: a liquid receptacle fillable with photosensitive materials (e.g. photopolymers, radiation-curable resins, and liquid), a building platform, a light source and a computer controlling the latter two. DLP printers can either have a bottom-up or top-down orientation.

There are many ways to print a 3D object, most of them utilize digitalized representations thereof such as computer aided design (CAD) files. Since additive manufacturing works by adding one layer of material on top of the other, CAD models are typically sliced into layers before being printed in 3D, in order to provide the 3D- printer with the required information for each layer to be printed. Once the 3D printer is loaded with the required information, a light source is focused on a photosensitive material which causes a photopolymerization thereof (that is, a light-induced polymerization (i.e. the photosensitive material solidifies)) thereby forming the first layer of the 3D-printed object. Next, the building platform is lowered or elevated, depend on printer's orientation, exposing a new surface layer of liquid polymer. The light source traces the new surface layer which instantly solidifies therefrom. This process is repeated until the desired object has been formed.

One of the challenges in the 3D printing techniques is to provide a mechanical strength in Z axis direction, e.g. due to lower adhesion between the printed layers (which may result for example in layer curls up and/or down, delamination, etc.). The remedy for such imperfections can be attaining better adhesion between material layers that are being printed. Making accurate prediction of required cure depth associated with a specific wavelength that is used is essential for achieving a required cross-linking between successive layers while maintaining desired Z axis resolution that is defined by layer thicknesses a 3D printer can produce.

Therefore, there is a growing need to provide a new system and method for three-dimensional (3D) printing.

References considered to be relevant as background to the presently disclosed subject matter are listed below. Acknowledgement of the references herein is not to be inferred as meaning that these are in any way relevant to the patentability of the presently disclosed subject matter.

US Patent No. US5182056 published on January 26, 1993 discloses an improved stereolithographic apparatus (SLA) and an improved method for generating a part from curable material. The invention utilizes control and/or knowledge of depths of penetration of actinic radiation into a vat of photopolymer to determine and/or control and/or produce desirable characteristics associated with the creation of parts. From a predictive point of view, these desirable characteristics may include determination of cure depth from a given exposure, determination cure width, determination of required minimum surface angle (MSA), determination of optimum skin fill spacing, the strength of cross sections of partially polymerized material, amount of curl type distortion, and necessary overcure to attain adhesion between layers, etc. These determinations can lead to the use of particular building techniques to insure adequate part formation. From the controlling and producing point of view, the penetration depths can be controlled to obtain optimized characteristics for a given layer thickness, maximized speed of drawing, minimized print through, maximized strength, minimum curl and other distortions, and maximum resolution, etc. An important aspect of the present invention is the integration of resin characteristics, with the depth of penetration associated with the particular resin being used and the wavelength(s) of actinic radiation being used to solidify it, and with the intensity profile of the beam of actinic radiation as it strikes the resin surface.

US Patent application No. US2015/0314039 published on November 5, 2015 discloses a light-polymerizable composition for additive manufacturing of resorbable scaffolds and implants comprising a biocompatible resin. The biocompatible resin includes a combination of photo-initiators or a dye-initiator package tailored to manufacture implants with the desired physical and chemical properties. A dye or other constituent controls between layer (z) resolution of the manufactured part built in an additive manufacturing device. A light absorber or other constituent controls within layer (x-y) resolution of the manufactured part.

US Patent No. US4752498 published on June 21, 1988 discloses an improved method of forming three-dimensional objects comprises irradiating an uncured photopolymer by transmitting an effective amount of photopolymer solidifying radiation through a radiation transmittent material which is in contact with the uncured photopolymer. The transmittent material is a material which leaves the irradiated surface capable of further cross-linking so that when a subsequent layer is formed it will adhere thereto. Using this method multilayer objects can be made.

US Patent No. US9694544 granted on July 4, 2017 discloses a three- dimensional geometry is received, and sliced into layers. A first anisotropic fill tool path for controlling a three dimensional printer to deposit a substantially anisotropic fill material is generated defining at least part of an interior of a first layer. A second anisotropic fill tool path for controlling a three dimensional printer to deposit the substantially anisotropic fill material defines at least part of an interior of a second layer. A generated isotropic fill material tool path defines at least part of a perimeter and at least part of an interior of a third layer intervening between the first and second layers.

GENERAL DESCRIPTION

In accordance with a first aspect of the presently disclosed subject matter, there is provided a three-dimensional (3D) printing system, comprising: a projector capable of generating a pattern of radiation on a two-dimensional (2D) plane; a liquid receptacle fillable with photosensitive material designed to solidify under the influence of radiation generated by the projector; a movable stage capable of moving perpendicularly to the 2D plane within the liquid receptacle; and a controller configured to: obtain a 3D model for printing, the 3D model comprised of a plurality of horizontal layers each horizontal layer being comprised of pixels, and each horizontal layer defining (a) projection pixels of the pixels, being pixels to solidify by the projector within the corresponding horizontal layer, and (b) no-projection pixels of the pixels, being pixels not to solidify by the projector within the corresponding horizontal layer; for at least one given layer of the horizontal layers, perform the following: analyze the given layer, to identify one or more reinforcement areas comprised of reinforcement pixels of the pixels, wherein each given reinforcement area of the reinforcement areas is: (a) associated with a full projection pattern so that the reinforcement pixels are projection pixels, (b) corresponds to an area, within a preceding layer preceding the given layer, that includes projection pixels only, and (c) located at a distance higher than a threshold from the no-projection pixels, within the layer and within the preceding layer; cause the projector to project the projection pixels of the given layer, wherein a first projection intensity of the pixels within the reinforcement areas is higher than a second projection intensity of projection pixels not within the reinforcement areas, thereby causing the photosensitive material associated with the projection pixels to solidify; and after completion of the given layer of the horizontal layers, move the movable stage to enable printing of a subsequent layer of the horizontal layers, subsequent to the given layer, if any.

In some cases, the first projection intensity causes the photosensitive material associated with the pixels of the reinforcement areas to cross-link with the photosensitive material associated with the corresponding pixels of the preceding layer.

In some cases, the first projection intensity causes a higher-level cross-linking than the second projection intensity.

In some cases, the at least one of the reinforcement areas of a given horizontal layer does not overlap with any of the reinforcement areas of the preceding layer preceding the given layer.

In some cases, the at least one of the reinforcement areas of a given horizontal layer at least partially overlaps with at least one of the reinforcement areas of the preceding layer preceding the given layer.

In some cases, the projector is a Digital Light Processing (DLP) projector.

In some cases, the projector is a laser.

In some cases, the thickness of each of the horizontal layers is up to 30 microns.

In some cases, the projector is a movable projector. In some cases, the movable projector is capable of moving on the two- dimensional (2D) plane.

In accordance with a second aspect of the presently disclosed subject matter, there is provided a method for a three-dimensional (3D) printing, the method comprising: obtaining, by a controller, a 3D model for printing, the 3D model comprised of a plurality of horizontal layers each horizontal layer being comprised of pixels, and each horizontal layer defining (a) projection pixels of the pixels, being pixels to solidify by a projector within the corresponding horizontal layer, and (b) no projection pixels of the pixels, being pixels not to solidify by the projector within the corresponding horizontal layer; for at least one given layer of the horizontal layers, the method further comprises: analyzing, by the controller, the given layer, to identify one or more reinforcement areas comprised of reinforcement pixels of the pixels, wherein each given reinforcement area of the reinforcement areas is: (a) associated with a full projection pattern so that the reinforcement pixels are projection pixels, (b) corresponds to an area, within a preceding layer preceding the given layer, that includes projection pixels only, and (c) located at a distance higher than a threshold from the no-projection pixels, within the layer and within the preceding layer; causing, by the controller, the projector to project the projection pixels of the given layer, wherein a first projection intensity of the pixels within the reinforcement areas is higher than a second projection intensity of projection pixels not within the reinforcement areas, thereby causing a photosensitive material associated with the projection pixels to solidify; and after completion of the given layer of the horizontal layers, moving, by the controller, a movable stage, capable of moving perpendicularly to a 2D plane within a liquid receptacle, to enable printing of a subsequent layer of the horizontal layers, subsequent to the given layer, if any, wherein the liquid receptacle is tillable with photosensitive material designed to solidify under the influence of radiation generated by the projector.

In some cases, the at least one of the reinforcement areas of a given horizontal layer does not overlap with any of the reinforcement areas of the preceding layer preceding the given layer. In some cases, the at least one of the reinforcement areas of a given horizontal layer at least partially overlaps with at least one of the reinforcement areas of the preceding layer preceding the given layer.

In some cases, the projector is a Digital Light Processing (DLP) projector.

In some cases, the projector is a laser.

In some cases, the projector is a movable projector.

In some cases, the movable projector is capable of moving on the two- dimensional (2D) plane.

In accordance with a third aspect of the presently disclosed subject matter, there is provided a non-transitory computer readable storage medium having computer readable program code embodied therewith, the computer readable program code, executable by a controller to perform a method for three-dimensional (3D) printing, the method comprising: obtaining, by the controller, a 3D model for printing, the 3D model comprised of a plurality of horizontal layers each horizontal layer being comprised of pixels, and each horizontal layer defining (a) projection pixels of the pixels, being pixels to solidify by a projector within the corresponding horizontal layer, and (b) no projection pixels of the pixels, being pixels not to solidify by the projector within the corresponding horizontal layer; for at least one given layer of the horizontal layers, the method further comprises: analyzing, by the controller, the given layer, to identify one or more reinforcement areas comprised of reinforcement pixels of the pixels, wherein each given reinforcement area of the reinforcement areas is: (a) associated with a full projection pattern so that the reinforcement pixels are projection pixels, (b) corresponds to an area, within a preceding layer preceding the given layer, that includes projection pixels only, and (c) located at a distance higher than a threshold from the no-projection pixels, within the layer and within the preceding layer; causing, by the controller, the projector to project the projection pixels of the given layer, wherein a first projection intensity of the pixels within the reinforcement areas is higher than a second projection intensity of projection pixels not within the reinforcement areas, thereby causing a photosensitive material associated with the projection pixels to solidify; and after completion of the given layer of the horizontal layers, moving, by the controller, a movable stage, capable of moving perpendicularly to a 2D plane within a liquid receptacle, to enable printing of a subsequent layer of the horizontal layers, subsequent to the given layer, if any, wherein the liquid receptacle is tillable with photosensitive material designed to solidify under the influence of radiation generated by the projector.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to understand the presently disclosed subject matter and to see how it may be carried out in practice, the subject matter will now be described, by way of non limiting examples only, with reference to the accompanying drawings, in which:

Fig. l is a block diagram schematically illustrating one example of a system for three-dimensional (3D) printing, in accordance with the presently disclosed subject matter;

Fig. 2 is a flowchart illustrating one example of a sequence of operations carried out for three-dimensional (3D) printing, in accordance with the presently disclosed subject matter;

Fig. 3 is an illustration of one example of reinforcement areas, in accordance with the presently disclosed subject matter; and

Figs 4A-4B illustrate exemplary material layup, in accordance with the presently disclosed subject matter.

DETAILED DESCRIPTION

In the following detailed description, numerous specific details are set forth in order to provide a thorough understanding of the presently disclosed subject matter. However, it will be understood by those skilled in the art that the presently disclosed subject matter may be practiced without these specific details. In other instances, well- known methods, procedures, and components have not been described in detail so as not to obscure the presently disclosed subject matter.

In the drawings and descriptions set forth, identical reference numerals indicate those components that are common to different embodiments or configurations.

Unless specifically stated otherwise, as apparent from the following discussions, it is appreciated that throughout the specification discussions utilizing terms such as “analyzing”, “providing”, “obtaining”, "moving", "stabilizing", "determining", "causing", "projecting" or the like, include action and/or processes of a computer that manipulate and/or transform data into other data, said data represented as physical quantities, e.g. such as electronic quantities, and/or said data representing the physical objects. The terms “computer”, “processor”, “processing resource”, “processing circuitry” and “controller” should be expansively construed to cover any kind of electronic device with data processing capabilities, including, by way of non limiting example, a personal desktop/laptop computer, a server, a computing system, a communication device, a smartphone, a tablet computer, a smart television, a processor (e.g. digital signal processor (DSP), a microcontroller, a field programmable gate array (FPGA), an application specific integrated circuit (ASIC), etc.), a group of multiple physical machines sharing performance of various tasks, virtual servers co-residing on a single physical machine, any other electronic computing device, and/or any combination thereof.

The operations in accordance with the teachings herein may be performed by a computer specially constructed for the desired purposes or by a general-purpose computer specially configured for the desired purpose by a computer program stored in a non-transitory computer readable storage medium. The term "non-transitory" is used herein to exclude transitory, propagating signals, but to otherwise include any volatile or non-volatile computer memory technology suitable to the application.

As used herein, the phrase "for example," "such as", "for instance" and variants thereof describe non-limiting embodiments of the presently disclosed subject matter. Reference in the specification to "one case", "some cases", "other cases" or variants thereof means that a particular feature, structure or characteristic described in connection with the embodiment(s) is included in at least one embodiment of the presently disclosed subject matter. Thus, the appearance of the phrase "one case", "some cases", "other cases" or variants thereof does not necessarily refer to the same embodiment(s).

It is appreciated that, unless specifically stated otherwise, certain features of the presently disclosed subject matter, 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 presently disclosed subject matter, which are, for brevity, described in the context of a single embodiment, may also be provided separately or in any suitable sub-combination.

In embodiments of the presently disclosed subject matter, fewer, more and/or different stages than those shown in Fig. 2 may be executed. In embodiments of the presently disclosed subject matter one or more stages illustrated in Fig. 2 may be executed in a different order and/or one or more groups of stages may be executed simultaneously. Figs. 1 illustrate a general schematic of the system architecture in accordance with an embodiment of the presently disclosed subject matter. Each module in Figs. 1 can be made up of any combination of software, hardware and/or firmware that performs the functions as defined and explained herein. The modules in Figs. 1 may be centralized in one location or dispersed over more than one location. In other embodiments of the presently disclosed subject matter, the system may comprise fewer, more, and/or different modules than those shown in Figs. 1.

Any reference in the specification to a method should be applied mutatis mutandis to a system capable of executing the method and should be applied mutatis mutandis to a non-transitory computer readable medium that stores instructions that once executed by a computer result in the execution of the method.

Any reference in the specification to a system should be applied mutatis mutandis to a method that may be executed by the system and should be applied mutatis mutandis to a non-transitory computer readable medium that stores instructions that may be executed by the system.

Any reference in the specification to a non-transitory computer readable medium should be applied mutatis mutandis to a system capable of executing the instructions stored in the non-transitory computer readable medium and should be applied mutatis mutandis to method that may be executed by a computer that reads the instructions stored in the non-transitory computer readable medium.

Bearing this in mind, attention is drawn to Fig. 1, showing a block diagram schematically illustrating one example of a system 100 for three-dimensional (3D) printing, according to one example of the presently disclosed subject matter.

The system for or three-dimensional (3D) printing 100 (also referred to herein as “system”) includes a projector 102, a liquid receptacle 104, a photosensitive material 106, a movable stage 108, a linear motor 110 and at least one controller 112.

Controller 112 can be one or more processing units (e.g. central processing units), microprocessors, microcontrollers or any other computing devices or modules, including multiple and/or parallel and/or distributed processing units, which are adapted to independently or cooperatively process data for controlling relevant resources of the system for three-dimensional (3D) printing 100 and for enabling operations related to resources thereof.

In order to perform a 3D-printing of a desired object, a digital representation thereof should be loaded/provided to the controller 112. The digital representation may be created using a Computer-aided design (CAD) or Computer-aided manufacturing (CAM) software or the like.

The controller 112 comprises a printing control module 114 configured to perform a process for three-dimensional (3D) printing, as further detailed herein with respect to Fig 2. The printing control module 114 is configured to control, inter alia, vertical movement of the linear motor 110 along a Z-axis control horizontal movement of the projector 102 in X-Y plane (in cases where the projector is a movable projector as further described hereinbelow). The linear motor 110 is configured for sequential and/or controlled shift of the movable stage 108 along Z-axis. According to certain examples of the presently disclosed subject matter, 3D- printing of a 3D model can be performed by movement of the projector 102 in the X-Y plane. Said movement of the projector 102 can be controlled, via wired or wireless communication, by the controller 112 in accordance with projection and no-projection pixels in the horizontal layer that is being projected, as further detailed herein. In other cases, the projector 102 can be stationary in the X-Y plane.

As depicted in Fig. 1, the system for three-dimensional (3D) printing 100 has a bottom-up orientation (while noting that this is non-limiting and it can also have any other orientation, mutatis mutandis). Hence, when the printing process starts, the movable stage 108 is immersed within the photosensitive material 106 from above, accommodated by the liquid receptacle 104, leaving a gap therebetween (i.e. between the movable stage 108 and the bottom surface of the liquid receptacle 104). This way a layer of a desired thickness of the photosensitive material 106 is exposed to the projector 102 located underneath the liquid receptacle 104. The projector 102 is configured to project (i.e. irradiate) a beam of electromagnetic radiation (e.g. in visible or ultraviolet spectrum) on the exposed layer of the photosensitive material 106 thereby causing photopolymerization thereof (i.e. the layer solidifies). After the first layer, the linear motor 110 is configured to elevate the movable stage 108 according to the layer thickness (as layer thickness may vary throughout printing, e.g. in a range of about 1- 30 micron or more) thereby allowing additional photosensitive material 106 to flow underneath the solidified layer adhered thereto. This process is repeated until the desired object is complete.

According to certain examples of the presently disclosed subject matter, the projector 102 may be a Digital Light Processing (DLP) projector. According to other examples of the presently disclosed subject matter, other controlled wavelength light sources can be utilized (e.g. laser), as further detailed hereinbelow with respect to Fig. 2

It is to be noted that in other cases, the system for three-dimensional (3D) printing 100 may have a top-down orientation or any other orientation capable of performing sequence of operations of the presently disclosed subject matter, mutatis mutandis.

It is to be noted that in some cases, system 100 may further include a network interface device (NID). System 100 may also include a video display unit (e.g. flat panel display, such as OLED, or liquid crystal display (LCD) or a cathode ray tube (CRT)), an alphanumeric input device (e.g. a keyboard), a cursor control device (e.g. a mouse), and a signal generation device (e.g. a speaker). System 100 may further include a memory. The memory may include a machine-accessible storage medium (or more specifically a computer-readable storage medium) on which stored one or more sets of instructions (e.g. software) embodying any one or more of the methodologies or functions described herein. The software may also reside, completely or at least partially, within the memory and/or within the controller 112 during execution thereof by the system 100, the memory and the controller 112 also constituting machine- readable storage media. The software may further be transmitted or received over a network via the network interface device.

It is to be further noted that the term “machine -readable storage medium” should be taken to include a single medium or multiple media (e.g. centralized or distributed database, and/or associated caches and servers) that store the one or more sets of instructions. The term “machine-readable storage medium” shall also be taken to include any medium that is capable of storing or encoding a set of instructions for execution by the machine and that cause the machine to perform any one or more of the methodologies of the present presently disclosed subject matter the term “machine- readable storage medium” shall accordingly be taken to include, but not limited to, solid-state memories, and optical and magnetic media.

Turning to Fig. 2, there is shown a flowchart illustrating one example of a sequence of operations carried out for three-dimensional (3D) printing, in accordance with the presently disclosed subject matter.

According to certain examples of the presently disclosed subject matter, system for three-dimensional (3D) printing 100 can be configured to perform a three- dimensional (3D) printing process 200, e.g. utilizing the printing control module 114. For this purpose, the system 100 can be configured to a obtain a 3D model for printing, the 3D model comprised of a plurality of horizontal layers, each horizontal layer being comprised of pixels, and each horizontal layer defining (a) projection pixels of the pixels, being pixels to solidify by the projector 102 within the corresponding horizontal layer, and (b) no-projection pixels of the pixels, being pixels not to solidify by the projector 102 within the corresponding horizontal layer (block 210).

The plurality of horizontal layers represents cross-sections of the 3D model to be printed, i.e. each horizontal layer represents a cross-section (e.g. surface geometry), of the 3D model, to be printed by system 100. Further, each horizontal layer is comprised of pixels which constitute discrete projection elements of a dynamic mask, which can be generated for example by digital mirror device (DMD). Each pixel is configured to solidify (i.e. a portion of the photosensitive material 106 associated with the pixel is configured to go through a photopolymerization process) under exposure to electromagnetic radiation (e.g. a light beam from UV radiation generator goes through DMD chip, which can control each pixel in its matrix) wherein each pixel is practically a volume pixel (voxel) having a height that represents a depth of radiation penetration (i.e. depth of photopolymerization in a given pixel).

In other cases, the pixels can constitute discrete projection elements of a laser wherein a laser source is utilized to generate a light beam of electromagnetic radiation configured to solidify portion of the photosensitive material 106 associated with a given pixel. Optionally, in such cases, the laser can be focused by utilizing one or more lenses and reflected by at least one motorized scanning mirror (i.e. galvanometer) - not shown in the figures, or alternatively, the laser can be moved directly, e.g. by utilizing an XY stepper motor arrangement.

According to the presently disclosed subject matter, each horizontal layer defines (a) projection pixels (i.e. illuminated pixels), which are pixels configured to solidify under the projection of electromagnetic radiation thereon, within the corresponding horizontal layer, and (b) no-projection pixels (i.e. non-illuminated pixels), which are pixels configured not to solidify by the projector, within the corresponding horizontal layer.

In some cases, the system 100 can be further configured to perform the following blocks 230, 240 and 250 for at least one given layer of the horizontal layers of the 3D model (block 220): In block 230, the system 100 is configured to analyze the given layer, to identify one or more reinforcement areas comprised of reinforcement pixels of the pixels. Each given reinforcement area is:

(a) associated with a full projection pattern (so that the reinforcement pixels are projection pixels);

(b) corresponds to an area within a preceding layer preceding the given layer, that includes projection pixels only, and

(c) located at a distance higher than a threshold from the no-projection pixels, within the layer and within the preceding layer.

Reinforcement pixels represent portions of the photosensitive material 106 in a given horizontal layer that are configured to perform a higher-level photochemical cross-linking reaction with corresponding pixels in the preceding layer, of the 3D model that is being printed, compared to a cross-linking level of other pixels comprised in the given horizontal layer. As known in the art, higher-level cross-linking between neighboring pixels can be achieved for example by a longer exposure time to electromagnetic radiation but in order cause a higher-level cross-linking between a given layer and its preceding layer, a higher projection intensity should be utilized in order to achieve higher penetration depth of the electromagnetic radiation into the photosensitive material 106 (e.g. to penetrate a layer of 10 micron intensity of 5 milliwatts (mW) can be applied on the photosensitive material 106). Higher-level cross- linking between layers can attain a stronger bond therebetween and thereby contribute to a strong and stable 3D model with reduced mechanical weakness in Z axis, if any.

Higher projection intensity can be applied to reinforcement pixels that represent areas in the 3D model that do not require high accuracy because under application of high intensities the photosensitive material 106 can solidify in neighboring pixels as well. At high projection intensities (e.g. application of 5mW to penetrate 10-micron layer) the electromagnetic radiation penetrates the photosensitive material 106 of the given layer reaching the preceding layer, preceding the given layer, and thereby causing higher-level cross-linking between said layers. In some cases, at high projection intensities the electromagnetic radiation can penetrate more than one layer, thereby causing higher-level cross-linking between the penetrated layers.

A given layer may include one or more reinforcement areas wherein each reinforcement area can be comprised of reinforcement pixels or combination of reinforcement pixels and projection pixels, thereby each reinforcement area is associated with a full projection pattern (i.e. all pixels comprised therein are to be projected on). Additionally, each reinforcement area of a given layer of the horizontal layers corresponds to a given reinforcement area, within a preceding layer preceding the given layer, which includes projection pixels only. Also, each given reinforcement area can be located at a distance higher than a predetermined threshold (e.g. a predetermined number of pixels or microns) from the no-projection pixels, within the layer and within the preceding layer, or from pixels associated with a projection area that requires higher accuracy (with respect to the reinforcement areas), in order to avoid solidification of undesired pixels. In other cases, the distance of each given reinforcement area from the no-projection pixels, within the layer and within the preceding layer, or from pixels associated with a projection area that requires higher accuracy (with respect to the reinforcement areas) can be calculated by the controller 112 for each reinforcement area based on, inter alia, the 3D model to be printed, the characteristics of the photosensitive material 106, thickness of each horizontal layer, desired exposure time, projection intensity, reinforcement area size and structure (e.g. the distance for a given reinforcement area may be proportional to its size and/or projection intensity applied thereon), etc.

Before continuing the description of the 3D printing process 200, attention is drawn to Figs. 3 and 4. Fig. 3 is an illustration of one example of reinforcement areas, in accordance with the presently disclosed subject matter.

In the figure, an exemplary dynamic mask structure 30 of a build platform 108, comprised of discrete pixels 31, is shown. The dynamic mask structure 30 having a projection pattern 32 to be printed on a given layer of the 3D model. As shown in Fig. 3, the projection pattern 32 includes projection pixels (i.e. illuminated pixels) only and two reinforcement areas, 34 and 38. Each reinforcement area, 34 and 38, has a predetermined location, size, structure and distance from no-projection pixels (i.e. non- illuminated pixels), 36 and 40 respectively. Alternatively, and/or additionally, the predetermined distance can be a minimum required distance from the reinforcement area to a projection area wherein higher accuracy (with respect to the reinforcement areas) is required (e.g. fine features, extremely small details, parts to be integrated precisely with other parts, etc.) in order to avoid over curing (i.e. solidification of undesired pixels) therein. It is to be noted that in some cases all reinforcement areas comprised within a given layer are associated with the same projection intensity and thus having the same penetration depth into the preceding layer, preceding the given layer. In other cases, each reinforcement area comprised within a given layer can be associated with a different projection intensity and thereby can have a different penetration depth into one or more preceding layers, preceding the given layer. In such cases wherein each reinforcement area comprised within a given layer is associated with a different projection intensity, the distance of each given reinforcement area from the no-projection pixels, within the layer and optionally within the preceding layer, or from pixels associated with a projection area that requires higher accuracy (with respect to the reinforcement areas) can be calculated by the controller 112 for each reinforcement area based on, inter alia, the 3D model to be printed, the characteristics of the photosensitive material 106, thickness of each horizontal layer, desired exposure time, projection intensity, reinforcement area size and structure (e.g. the distance for a given reinforcement area may be proportional to its size and/or projection intensity applied thereon), etc.

Reference is currently made to Figs 4A-4B, that illustrate exemplary material layup, in accordance with the presently disclosed subject matter.

Fig. 4A illustrates exemplary layup of horizontal layers 41-45 of solidified photosensitive material (e.g. green state polymerization) wherein at least one of the reinforcement areas of a given horizontal layer does not overlap with any of the reinforcement areas of the preceding layer preceding the given layer. As shown in Fig. 4A, reinforcement area 54 in horizontal layer 44 does not overlap with reinforcement area 53 in horizontal layer 43 and reinforcement area 56 in horizontal layer 43 does not overlap with reinforcement area 52 in horizontal layer 42. Such dispersion of reinforcement areas, where applicable, within the 3D model that is being printed enables mechanical strength in Z axis direction (e.g. tensile strength along the Z axis) due to strong adhesion between the printed layers at varying contact areas along the 3D model. In such cases, the reinforcement areas in fact serve as Z axis anchors distributed throughout the 3D model thereby contributing to its stiffness or resistance to elastic deformation (i.e. isotropic 3D model).

Fig. 4B illustrates exemplary layup of horizontal layers according to another example of the presently disclosed subject matter. As shown in fig. 4B, horizontal layers 46-50 of solidified photosensitive material (e.g. green state polymerization) wherein at least one of the reinforcement areas of a given horizontal layer at least partially overlaps (and in some cases, fully overlaps) with at least one of the reinforcement areas of the preceding layer preceding the given layer. As shown in Fig. 4B, reinforcement area 60 in horizontal layer 50 overlaps with reinforcement area 69 in horizontal layer 49, which in turn overlaps with reinforcement area 68 in horizontal layer 48 and reinforcement area 68 in horizontal layer 48 overlaps with reinforcement area 67 in horizontal layer 47. Such configuration of reinforcement areas along Z axis of the 3D model yields continuous mechanical strength in Z axis direction (e.g. tensile strength along the Z axis) due to strong adhesion between the printed layers having the same X-Y contact areas along Z axis of the 3D model.

It is to be noted that in order to provide readily understanding of the presently disclosed subject matter, Figs 4A-4B illustrate adjacent reinforcement areas having the same proportions while other configurations may be applied (e.g. adjacent reinforcement areas having varying X-Y size, alternating reinforcement areas, etc.)

In some cases, a given layer may not include one or more reinforcement areas. For example, the first printed layer cannot serve as a layer having reinforcement areas due to lack of a preceding layer whereto the electromagnetic radiation can penetrate. Additionally, in cases where high accuracy is required throughout a given layer it may not include reinforcement areas therein.

Attention is now drawn back to the description of the 3D printing process 200. In block 240, the system 100 is configured to cause the projector to project the projection pixels of the given layer, wherein a first projection intensity of the pixels within the reinforcement areas is higher than a second projection intensity of projection pixels not within the reinforcement areas, thereby causing the photosensitive material associated with the projection pixels to solidify.

In general, each projection pixel (i.e. illuminated pixel) can be associated with a given projection intensity configured to solidify the photosensitive material 106 associated with said pixel. Pixels within the reinforcement areas can be associated with projection intensity that is higher than the projection intensity of projection pixels that are not within the reinforcement areas. The projection intensity of pixels within the reinforcement areas causes a higher-level cross-linking then the cross-linking level achieved by projection intensity of projection pixels that are not within the reinforcement areas.

The particular wavelengths of stimulating radiation with associated penetration depths (i.e. projection intensity) can be determined by the controller 112 based on the 3D model to be printed, the characteristics of the photosensitive material 106, thickness of each layer, desired exposure time, etc. After completion of a given layer of the horizontal layers, the system 100 moves the movable stage 108 to enable printing of a subsequent layer of the horizontal layers, subsequent to the given layer, if any (block 250).

As detailed hereinabove, with respect to Fig.1, the movable stage 108 is configured to be elevated according to the horizontal layer thickness to allow additional photosensitive material 106 to flow underneath the solidified layer adhered thereto. Said movement of the movable stage 108 can be controlled, via wired or wireless communication, by the controller 112 in accordance with the presently disclosed subject matter.

In some cases, the controller 112 can be further configured to wait a stabilization time-period after moving the movable stage 108 for the movable stage 108 to stabilize, before starting to print the subsequent layer. Movement of the movable stage 108 may cause vibrations thereof and optionally of system 100. Therefore, in order to avoid distortions in the horizontal layer(s) while printing the 3D model, the controller 112 can be configured to wait a stabilization time-period after moving the movable stage 108 in order to allow the movable stage 108 to stabilize.

The stabilization time-period may be milliseconds, microseconds or less, while noting that in case the stabilization time-period is larger than zero, during such stabilization time-period, movable stage 108 is not actively moved by the linear motor 110

It is to be noted that, with reference to Fig. 2, some of the blocks can be integrated into a consolidated block or can be broken down to a few blocks and/or other blocks may be added. It is to be further noted that some of the blocks are optional. It should be also noted that whilst the flow diagram is described also with reference to the system elements that realizes them, this is by no means binding, and the blocks can be performed by elements other than those described herein.

It is to be understood that the presently disclosed subject matter is not limited in its application to the details set forth in the description contained herein or illustrated in the drawings. The presently disclosed subject matter is capable of other embodiments and of being practiced and carried out in various ways. Hence, it is to be understood that the phraseology and terminology employed herein are for the purpose of description and should not be regarded as limiting. As such, those skilled in the art will appreciate that the conception upon which this disclosure is based may readily be utilized as a basis for designing other structures, methods, and systems for carrying out the several purposes of the present presently disclosed subject matter.

It will also be understood that the system according to the presently disclosed subject matter can be implemented, at least partly, as a suitably programmed computer. Likewise, the presently disclosed subject matter contemplates a computer program being readable by a computer for executing the disclosed method. The presently disclosed subject matter further contemplates a machine-readable memory tangibly embodying a program of instructions executable by the machine for executing the disclosed method. Examples of the presently disclosed subject matter may be provided as a computer program product, or software, that may include a machine-readable medium having stored thereon instructions, which may be used to program a computer system (or other electronic devices) to perform a process according to the presently disclosed subject matter. A machine-readable medium includes any mechanism for storing or transmitting information in a form readable by a machine (e.g. a computer). For example, a machine-readable (e.g. computer readable) medium includes a machine (e.g. a computer) readable storage medium (e.g. read only memory (“ROM”), random access memory (“RAM”), magnetic disk storage media, optical storage media, flash memory devices, etc.), a machine (e.g. computer) readable transmission medium (electrical, optical, acoustical or other form of propagated signals (e.g., infrared signals, digital signals, etc.)), etc.

Fig. 1 illustrates a diagrammatic representation of a system in the exemplary form of a machine including hardware and software such as e.g. set of instructions, causing the system to perform any one or more of the above techniques. In alternative examples, the machine may be connected (e.g. networked) to other machines in a Local Area Network (LAN), an intranet, an extranet, or the Internet. Further, while only a single machine is illustrated, the term “machine” shall also be taken to include any collection of machines (e.g. computers) that individually or jointly execute a set (or multiple sets) of instructions to perform any one or more of the methodologies discussed herein.

In the foregoing specification, the presently disclosed subject matter has been described with reference to specific examples of embodiments of the presently disclosed subject matter. It will, however, be evident that various modifications and changes may be made therein without departing from the broader spirit and scope of the presently disclosed subject matter as set forth in the appended claims.

Also, the presently disclosed subject matter is not limited to physical devices or units implemented in nonprogrammable hardware but can also be applied in programmable devices or units able to perform the desired device functions by operating in accordance with suitable program code, such as mainframes, minicomputers, servers, workstations, personal computers, notepads, personal digital assistants, electronic games, and other embedded systems, cell phones and various other wireless devices, commonly denoted in this application as ‘computer systems’.

However, other modifications, variations and alternatives are also possible. The specifications and drawings are, accordingly, to be regarded in an illustrative rather than in a restrictive sense.

While certain features of the presently disclosed subject matter have been illustrated and described herein, many modifications, substitutions, changes, and equivalents will now occur to those of ordinary skill in the art. It is, therefore, to be understood that the appended claims are intended to cover all such modifications and changes as fall within the true spirit of the presently disclosed subject matter.

Claims

CLAIMS:

1. A three-dimensional (3D) printing system, comprising: a projector capable of generating a pattern of radiation on a two-dimensional (2D) plane; a liquid receptacle fillable with photosensitive material designed to solidify under the influence of radiation generated by the projector; a movable stage capable of moving perpendicularly to the 2D plane within the liquid receptacle; and a controller configured to: obtain a 3D model for printing, the 3D model comprised of a plurality of horizontal layers each horizontal layer being comprised of pixels, and each horizontal layer defining (a) projection pixels of the pixels, being pixels to solidify by the projector within the corresponding horizontal layer, and (b) no-projection pixels of the pixels, being pixels not to solidify by the projector within the corresponding horizontal layer; for at least one given layer of the horizontal layers, perform the following: analyze the given layer, to identify one or more reinforcement areas comprised of reinforcement pixels of the pixels, wherein each given reinforcement area of the reinforcement areas is: (a) associated with a full projection pattern so that the reinforcement pixels are projection pixels, (b) corresponds to an area within a preceding layer preceding the given layer, that includes projection pixels only, and (c) located at a distance higher than a threshold from the no-projection pixels, within the layer and within the preceding layer; cause the projector to project the projection pixels of the given layer, wherein a first projection intensity of the pixels within the reinforcement areas is higher than a second projection intensity of projection pixels not within the reinforcement areas, thereby causing the photosensitive material associated with the projection pixels to solidify; and after completion of the given layer of the horizontal layers, move the movable stage to enable printing of a subsequent layer of the horizontal layers, subsequent to the given layer, if any.

2. The 3D printing system of claim 1, wherein the first projection intensity causes the photosensitive material associated with the pixels of the reinforcement areas to cross-link with the photosensitive material associated with the corresponding pixels of the preceding layer.

3. The 3D printing system of claim 2, wherein the first projection intensity causes a higher-level cross-linking than the second projection intensity.

4. The 3D printing system of claim 1, wherein at least one of the reinforcement areas of a given horizontal layer does not overlap with any of the reinforcement areas of the preceding layer preceding the given layer.

5. The 3D printing system of claim 1, wherein at least one of the reinforcement areas of a given horizontal layer at least partially overlaps with at least one of the reinforcement areas of the preceding layer preceding the given layer.

6. The 3D printing system of claim 1, wherein the projector is a Digital Light Processing (DLP) projector.

7. The 3D printing system of claim 1, wherein the projector is a laser.

8. The 3D printing system of claim 1, wherein the thickness of each of the horizontal layers is up to 30 microns.

9. The 3D printing system of claim 1, wherein the projector is a movable projector.

10. The 3D printing system of claim 9, wherein the movable projector is capable of moving on the two-dimensional (2D) plane.

11. A method for a three-dimensional (3D) printing, the method comprising: obtaining, by a controller, a 3D model for printing, the 3D model comprised of a plurality of horizontal layers each horizontal layer being comprised of pixels, and each horizontal layer defining (a) projection pixels of the pixels, being pixels to solidify by a projector within the corresponding horizontal layer, and (b) no-projection pixels of the pixels, being pixels not to solidify by the projector within the corresponding horizontal layer; for at least one given layer of the horizontal layers, the method further comprises: analyzing, by the controller, the given layer, to identify one or more reinforcement areas comprised of reinforcement pixels of the pixels, wherein each given reinforcement area of the reinforcement areas is: (a) associated with a full projection pattern so that the reinforcement pixels are projection pixels, (b) corresponds to an area, within a preceding layer preceding the given layer, that includes projection pixels only, and (c) located at a distance higher than a threshold from the no-projection pixels, within the layer and within the preceding layer; causing, by the controller, the projector to project the projection pixels of the given layer, wherein a first projection intensity of the pixels within the reinforcement areas is higher than a second projection intensity of projection pixels not within the reinforcement areas, thereby causing a photosensitive material associated with the projection pixels to solidify; and after completion of the given layer of the horizontal layers, moving, by the controller, a movable stage, capable of moving perpendicularly to a 2D plane within a liquid receptacle, to enable printing of a subsequent layer of the horizontal layers, subsequent to the given layer, if any, wherein the liquid receptacle is tillable with photosensitive material designed to solidify under the influence of radiation generated by the projector.

12. The method of claim 11, wherein the first projection intensity causes the photosensitive material associated with the pixels of the reinforcement areas to cross-link with the photosensitive material associated with the corresponding pixels of the preceding layer.

13. The method of claim 12, wherein the first projection intensity causes a higher-level cross-linking than the second projection intensity.

14. The method of claim 11, wherein at least one of the reinforcement areas of a given horizontal layer does not overlap with any of the reinforcement areas of the preceding layer preceding the given layer.

15. The method of claim 11, wherein at least one of the reinforcement areas of a given horizontal layer at least partially overlaps with at least one of the reinforcement areas of the preceding layer preceding the given layer.

16. The method of claim 11, wherein the projector is a Digital Light Processing (DLP) projector.

17. The method of claim 11, wherein the projector is a laser.

18. The method of claim 11, wherein the thickness of each of the horizontal layers is up to 30 microns.

19. The method of claim 11, wherein the projector is a movable projector.

20. The method of claim 11, wherein the movable projector is capable of moving on the two-dimensional (2D) plane.

21. A non-transitory computer readable storage medium having computer readable program code embodied therewith, the computer readable program code, executable by a controller to perform a method for three-dimensional (3D) printing, the method comprising: obtaining, by the controller, a 3D model for printing, the 3D model comprised of a plurality of horizontal layers each horizontal layer being comprised of pixels, and each horizontal layer defining (a) projection pixels of the pixels, being pixels to solidify by a projector within the corresponding horizontal layer, and (b) no-projection pixels of the pixels, being pixels not to solidify by the projector within the corresponding horizontal layer; for at least one given layer of the horizontal layers, the method further comprises: analyzing, by the controller, the given layer, to identify one or more reinforcement areas comprised of reinforcement pixels of the pixels, wherein each given reinforcement area of the reinforcement areas is: (a) associated with a full projection pattern so that the reinforcement pixels are projection pixels, (b) corresponds to an area, within a preceding layer preceding the given layer, that includes projection pixels only, and (c) located at a distance higher than a threshold from the no-projection pixels, within the layer and within the preceding layer; causing, by the controller, the projector to project the projection pixels of the given layer, wherein a first projection intensity of the pixels within the reinforcement areas is higher than a second projection intensity of projection pixels not within the reinforcement areas, thereby causing a photosensitive material associated with the projection pixels to solidify; and after completion of the given layer of the horizontal layers, moving, by the controller, a movable stage, capable of moving perpendicularly to a 2D plane within a liquid receptacle, to enable printing of a subsequent layer of the horizontal layers, subsequent to the given layer, if any, wherein the liquid receptacle is tillable with photosensitive material designed to solidify under the influence of radiation generated by the projector.