Methods and systems for reducing heat generation in the photocuring of liquid resins

Abstract

In a photopolymerization and curing printer (100), a beam scanner (26) scans a beam (28) that passes through a mask (30) and enters a groove (10) containing photocurable resin (18). The mask has pixels that can be configured to be partially transparent or opaque to the beam, the diameter of which is larger than the cross-sectional size of the mask pixels. During the exposure duration, a first subset of the pixels is controlled to be transparent at locations corresponding to the cross-section of the three-dimensional object to be printed, and a second subset of the pixels is controlled to be opaque at locations not corresponding to the cross-section of the three-dimensional object. The beam scanner (26) is controlled to scan the beam passing through the mask (30) such that the beam (28) always incident on at least one of the pixels of the mask that are controlled to be transparent.

Description

[0001] Related applications

[0002] This application claims priority to U.S. Provisional Application No. 63 / 200,258, filed on February 24, 2021. Technical Field

[0003] The present invention relates to printing three-dimensional objects by photocuring liquid resin, and more specifically, to reducing the heat transferred from the light source to the liquid resin. Background Technology

[0004] In the 3D printing of objects involving the curing of photocurable liquid resins, heating the liquid resin is an obstacle. Not only is the curing of photocurable liquid resins an exothermic reaction (which locally heats the area where curing occurs within the resin), but the irradiation of the mask by a light source (typically an ultraviolet (UV) light source) also causes the mask to heat up. Since the mask is located near the liquid resin, any heating of the mask will lead to further heating of the photocurable liquid resin.

[0005] If the liquid resin temperature exceeds a critical temperature, some resin may begin to solidify even without UV irradiation, leading to defects in the printed object. To prevent the liquid resin temperature from exceeding this critical temperature, existing methods may periodically stop the printing process to allow the photocurable liquid resin to cool, but this reduces print yield. Additionally, existing methods may use a resin circulation system to cool the heated resin. While heat dissipation via a resin circulation system can effectively achieve the desired effect of controlling the liquid resin temperature, the methods described herein control the liquid resin temperature through other or additional means. Summary of the Invention

[0006] In one embodiment of the invention, a vat polymerization printer includes a tank configured to contain a photocurable liquid resin, a light source configured to emit a light beam, and a mask positioned between the light source and the tank, the mask having pixels configured to be transparent or opaque to a portion of the light beam, respectively. Preferably, the diameter of the cross-section of the light beam is larger than the cross-sectional size of each corresponding pixel. A beam scanner is configured to scan the light beam passing through the mask, and a processor, operating under stored processor-executable instructions, controls the vat polymerization printer to print a cross-section of a three-dimensional object by: controlling a first subset of pixels to be transparent at locations corresponding to the cross-section of the three-dimensional object during an exposure duration, and controlling a second subset of pixels to be opaque at locations not corresponding to the cross-section of the three-dimensional object; and controlling the beam scanner to scan the light beam passing through the mask during an exposure duration such that the light beam always incident on at least one of the pixels of the mask that are controlled to be transparent.

[0007] In various embodiments, the diameter of the cross-section of the light beam can be at least ten times or at least one hundred times the size of the cross-section of each corresponding pixel of the mask. Furthermore, the light source can include a laser source configured to emit a laser beam; and a beam expander configured to generate a beam from the laser beam, wherein the diameter of the cross-section of the beam is larger than the diameter of the cross-section of the laser beam.

[0008] In various embodiments, processor-executable instructions further enable the processor to determine the scanning path of the light beam based on the corresponding positions of the pixels controlled to be transparent during the exposure duration. Furthermore, during the exposure duration, processor-executable instructions further enable the processor to shut off the light source, while the beam scanner repositions the light beam from a first region of the mask comprising at least some pixels controlled to be transparent to a third region of the mask comprising at least some pixels controlled to be transparent, the third region of the mask being separated from the first region by a second region of the mask comprising only pixels controlled to be opaque. In another embodiment, processor-executable instructions further enable the processor to control blocking elements to block the light beam, while the beam scanner repositions the light beam from the first region of the mask comprising at least some pixels controlled to be transparent to the third region of the mask. In various embodiments, the pixels may be electromodulated liquid crystal pixel elements.

[0009] In various embodiments, the photopolymerization and curing printer may further include a transparent backing member disposed between the mask and the flexible film. Additionally, a lifter plate may be disposed within a groove, and during printing, a three-dimensional object formed by the cured portion of the photopolymerized liquid resin is fixed to the lifter plate. A height adjuster may be configured to control the vertical position of the lifter plate above the mask.

[0010] In another embodiment of the invention, a photopolymerization and curing printer is provided, comprising a tank configured to contain photocurable liquid resin, a light source configured to emit a light beam, and a mask having pixels configurable to be partially transparent or opaque to the light beam. The diameter of the cross-section of the light beam is larger than the size of the cross-section of each corresponding pixel, and a beam scanner is configured to scan the light beam through the mask. A processor of a controller executes instructions to control the photopolymerization and curing printer to print a cross-section of a three-dimensional object by: controlling a first subset of pixels to be transparent at locations corresponding to the cross-section of the three-dimensional object and a second subset of pixels to be opaque at locations not corresponding to the cross-section of the three-dimensional object during the exposure duration; and controlling the beam scanner to scan the light beam through at least one region of the mask, the at least one region having pixels controlled to be transparent, wherein during the printing of the cross-section of the three-dimensional object, the light beam scans at most 10% of the pixels controlled to be opaque.

[0011] In various embodiments, the controller's processor may further execute instructions to control a beam scanner to repeatedly scan a beam passing through a first region of the mask, comprising at least some pixels controlled to be transparent; then control the beam scanner to scan a beam along a beam path within a second region; and subsequently control the beam scanner to repeatedly scan a beam passing through a third region of the mask, wherein the second region separates the first and third regions, the second region comprising only pixels controlled to be opaque, the third region comprising at least some pixels controlled to be transparent, and the beam path within the second region is the shortest path connecting the beam paths within the first and third regions. Repeated scanning of the beam passing through the first region of the mask includes at least one of raster scanning or back-and-forth scanning of the first region of the mask, and repeated scanning of the beam passing through the third region of the mask includes at least one of raster scanning or back-and-forth scanning of the third region of the mask.

[0012] In another embodiment of the invention, a photopolymerization and curing printer is provided for printing a cross-section of a three-dimensional object in its photopolymerization and curing region. The photopolymerization and curing printer includes: (i) a tank configured to contain a photopolymerizable liquid resin; (ii) a flexible film defining a bottom boundary of the photopolymerization and curing region; (iii) a light source configured to emit a light beam; (iv) a beam scanner configured to scan the light beam; and (v) a mask disposed between the beam scanner and the flexible film, the mask having pixels that can be configured to be transparent or opaque to a portion of the light beam, wherein the diameter of the cross-section of the light beam is larger than the size of the cross-section of each corresponding pixel. According to the printing process, during the exposure duration, a first subset of pixels is controlled to be transparent at locations corresponding to the cross-section of the three-dimensional object, a second subset of pixels is controlled to be opaque at locations not corresponding to the cross-section of the three-dimensional object, and the light beam is scanned through at least one region of the mask having at least some pixels controlled to be transparent and into the photopolymerization and curing region, wherein during the printing of the cross-section of the three-dimensional object, the light beam scans at most 10% of the pixels controlled to be opaque.

[0013] During this printing process, within the exposure time, by controlling a first subset and a second subset of pixels, a first region of the mask includes at least some pixels controlled to be transparent, a second region of the mask includes only pixels controlled to be opaque, and a third region of the mask includes at least some pixels controlled to be transparent. The scanning of the light beam includes repeatedly scanning the light beam passing through the first region of the mask and through the pixels controlled to be transparent in the first region into the photocuring region, then scanning the light beam in the second region along the shortest path connecting the light beam paths in the first and third regions, and subsequently repeatedly scanning the light beam passing through the third region of the mask and through the pixels controlled to be transparent in the third region into the photocuring region. Repeated scanning of the light beam passing through the first region of the mask includes at least one of raster scanning or back-and-forth scanning of the first region of the mask, and repeated scanning of the light beam passing through the third region of the mask includes at least one of raster scanning or back-and-forth scanning of the third region of the mask.

[0014] Alternatively or additionally, during the exposure duration, by controlling a first subset and a second subset of pixels, a first region of the mask includes at least some pixels controlled to be transparent, a second region of the mask includes only pixels controlled to be opaque, and a third region of the mask includes at least some pixels controlled to be transparent, and scanning of the beam includes: repeatedly scanning the beam that passes through the first region of the mask and enters the photocuring region through pixels controlled to be transparent in the first region; repositioning the beam from the first region of the mask to the third region of the mask without scanning the second region of the mask; and repeatedly scanning the beam that passes through the third region of the mask and enters the photocuring region through pixels controlled to be transparent in the third region. Repeated scanning of the beam that passes through the first region of the mask includes at least one of raster scanning or back-and-forth scanning of the first region of the mask, and wherein repeated scanning of the beam that passes through the third region of the mask includes at least one of raster scanning or back-and-forth scanning of the third region of the mask.

[0015] During the exposure duration of the printing process, the total number of pixels in the first subset of pixels may be less than the total number of pixels in the second subset of pixels.

[0016] In another embodiment of the invention, a photopolymerization and curing printer is provided for printing cross-sections of a three-dimensional object in its photopolymerization and curing region, the photopolymerization and curing printer comprising: (i) a tank configured to contain a photopolymerization liquid resin; (ii) a flexible film defining a bottom boundary of the photopolymerization and curing region; (iii) a light source configured to emit a light beam; (iv) a beam scanner configured to scan the light beam; and (v) a mask disposed between the beam scanner and the flexible film, the mask having pixels that can be configured to be transparent or opaque to a portion of the light beam, wherein the diameter of the cross-section of the light beam is larger than the size of the cross-section of each respective pixel. This process includes: during the exposure duration, controlling a first subset of pixels to be transparent at locations corresponding to the cross-section of a three-dimensional object, and controlling a second subset of pixels to be opaque at locations not corresponding to the cross-section of the three-dimensional object; and during the exposure duration, scanning a light beam passing through a mask and having at least some pixels controlled to be transparent and entering a photocurable region, wherein the scanning compensates for non-uniformity of light transmission of individual pixels in at least one region of the mask by at least one of the following: (i) changing the light intensity of the light beam as the light beam scans over at least one region, (ii) changing the scanning speed of the light beam as the light beam scans over at least one region, or (iii) changing the number of times the light beam is repeatedly scanned over at least one region.

[0017] These and other embodiments of the present invention will be described more fully below. Attached Figure Description

[0018] Now, without limiting the scope of the invention, embodiments of the invention will be described by way of example with reference to the accompanying drawings, wherein:

[0019] Figure 1 A cross-section of a three-dimensional (3D) printing system according to an embodiment of the present invention is described.

[0020] Figure 2 The components of a light source according to an embodiment of the present invention are described.

[0021] Figure 3A The transparent and opaque areas of a mask according to an embodiment of the present invention are described.

[0022] Figure 3B An embodiment of the present invention has been described. Figure 3A The image shows a magnified view of a portion of the mask, where the individual transparent and opaque pixels are visible.

[0023] Figure 4A The light spot of a light beam according to an embodiment of the present invention is described, the light beam being... Figure 3A A portion of the mask shown in the image is irradiated.

[0024] Figure 4B An embodiment of the present invention has been described. Figure 3A The image shows a portion of the mask and a magnified view of the light spot, where the individual transparent and opaque pixels are visible.

[0025] Figure 5 A restricted area (e.g.,) of a mask having transparent pixels is described according to an embodiment of the present invention. Figure 3A The beam path of the beam during grating scanning (as shown).

[0026] Figure 6 The transparent and opaque areas of a mask according to an embodiment of the present invention are described.

[0027] Figure 7 A restricted area (e.g.,) of a mask having transparent pixels is described according to an embodiment of the present invention. Figure 6 (As shown) Perform back-and-forth scanning.

[0028] Figure 8 The transparent and opaque areas of a mask according to an embodiment of the present invention are described.

[0029] Figure 9 A beam scanning method according to an embodiment of the present invention is described. Figure 8 The beam path of the mask, wherein the beam repeatedly scans a first region and a second region having transparent pixels.

[0030] Figure 10 A beam scanning method according to an embodiment of the present invention is described. Figure 8 The beam path of the mask, wherein the beam repeatedly scans a first region and a second region having transparent pixels, and further scans the shortest path connecting the beam paths in the first region and the beam paths in the second region.

[0031] Figure 11 A 3D printing system with two beams, each configured to scan a mask of a photopolymerization and curing printer, is described according to an embodiment of the invention.

[0032] Figure 12A A flowchart is described below, illustrating a method for printing a cross-section of a three-dimensional object while minimizing heat generation, according to an embodiment of the present invention.

[0033] Figure 12B A flowchart is provided describing another method for printing the cross-section of a three-dimensional object while reducing heat generation, according to an embodiment of the present invention.

[0034] Figure 13A A flowchart is provided describing a method for scanning a beam of light passing through the surface of a mask in a 3D printing system according to an embodiment of the present invention.

[0035] Figure 13B A flowchart is provided describing another method for scanning a beam of light passing through the surface of a mask in a 3D printing system, according to an embodiment of the present invention.

[0036] Figure 14 A flowchart is described for a method according to an embodiment of the present invention, which reduces heat generation when printing a cross-section of a three-dimensional object and further compensates for the non-uniformity of light transmittance of individual pixels of the mask passing through the 3D printing system during printing.

[0037] Figure 15 The components of a computer system are described, in which computer-readable instructions for implementing the methods of the present invention can be stored and executed. Detailed Implementation

[0038] In the following detailed description of embodiments of the invention, reference is made to the accompanying drawings, which form part of the invention, and specific embodiments in which the invention can be practiced are illustrated by way of example. It should be understood that other embodiments and structural changes may be made without departing from the scope of the invention. The description associated with any of the drawings can be applied to different drawings containing similar or analogous components / steps. Although the sequence diagrams show a series of steps in a certain order, the order of some of these steps may be changed.

[0039] In one embodiment of the invention, the need to cool the liquid resin is reduced by decreasing the degree to which the liquid resin is heated. While it is impossible to avoid the exothermic reaction that occurs during resin curing, which causes heating of the liquid resin, the heating of the mask can be reduced by selectively irradiating only the mask areas with transparent pixels and / or minimizing irradiation of the mask areas with opaque pixels. These and other embodiments of the invention will be described more fully below with reference to the accompanying drawings.

[0040] Figure 1 A cross-section of a three-dimensional (3D) printing system 100 (also known as a photopolymerization printer) is described, in which electromagnetic radiation (e.g., ultraviolet light) is used to cure a photopolymerizable liquid resin 18 to create an object 22 (e.g., a 3D object). The object 22 can be manufactured layer by layer; that is, a new layer of the object 22 can be formed by photopolymerizing a layer 34 of liquid resin 18 adjacent to the bottom surface of the object 22, and then the object is lifted by a lifting plate 20 so that a new layer of photopolymerizable liquid resin 18 is filled below the newly formed layer and pumped under the newly formed layer; this process is then repeated to form other layers.

[0041] The 3D printing system 100 includes a tank 10 for containing photocurable liquid resin 18. The bottom of the tank 10 includes a bottom opening 12 to allow electromagnetic radiation from a light source 24 (such as a filtered beam 32) to enter the tank 10. An optional radiation-transmitting backing member 16 (e.g., borosilicate glass or tempered glass, such as alkali aluminosilicate glass with a thickness of approximately 100 µm) may be used to seal the opening 12 of the tank (i.e., to prevent leakage of the photocurable liquid resin 18 from the tank 10) while allowing electromagnetic radiation to enter the tank 10 to cure the liquid polymer.

[0042] Currently, one challenge facing this 3D printing system is that, in addition to adhering to the object 22, the newly formed layer often adheres to the bottom of the groove. Therefore, when the lifting plate 20 attached to the object is raised via the height adjuster 39, the newly formed layer may tear and / or detach from the object 22. To address this issue, the flexible membrane 14 can be positioned adjacent to the backing member 16 (if present), or it can form the bottom of the groove (if no backing member is used). The flexible membrane 14 can be made of silicone or other materials and optionally coated with a non-stick material such as polytetrafluoroethylene (PTFE) to reduce the likelihood of the newly formed layer adhering to the bottom of the groove 10. The flexible membrane 14 is transparent (or nearly transparent) to the wavelength of radiation emitted by the light source 24, allowing radiation to enter the groove 10 and thereby cure the liquid resin 18.

[0043] A mask 30 can be provided to spatially filter radiation incident on layer 34, thereby curing specific areas of liquid resin 18 corresponding to the cross-section of the printed object 22. The mask 30 can be a transmissive spatial light modulator, such as a liquid crystal display panel (LCD) with a two-dimensional addressable pixel array. As will be described more clearly below, some pixels of the mask can be controlled to be transparent, while others can be controlled to be opaque. Transparent pixels allow radiation to pass through the mask 30 at certain spatial locations and into the groove 10, thereby curing the corresponding portions (voxels) of the liquid resin 18, while opaque pixels prevent radiation from passing through certain spatial locations of the mask 30, thereby avoiding curing the corresponding portions (voxels) of the liquid resin 18.

[0044] The beam scanner 26 can scan the beam 28 passing through the mask 30. As will be described in detail below, the beam scanner 26 can be controlled by the controller 36 to selectively scan the beam 28 passing through areas of the mask 30 with transparent pixels, while substantially avoiding areas in the mask 30 that have only opaque pixels. The beam scanner 26 can be an xy scanner, such as a galvanometer scanner (also known as a galvanometer scanner). In a preferred embodiment (although...) Figure 1 (Not described in the text) The distance between the beam scanner 26 and the mask 30 is much greater than the lateral dimension of the mask 30, so that whether the beam 28 scans the peripheral area of ​​the mask 30 or the central area of ​​the mask 30, the beam 28 is incident on the mask 30 at approximately 90°. This relative position between the beam scanner 26 and the mask 30, as well as the minimum spacing between the mask 30 and the resin layer 34, reduces the diffraction effect generated when light passes through the mask 30, thereby improving the printing accuracy of the object 22.

[0045] Controller 36 can be communicatively coupled to mask 30, beam scanner 26, light source 24, and height adjuster 39 via control signal paths 38a, 38b, 38c, and 38d (e.g., electrical signal paths). Controller 36 can control the addressable pixels of mask 30 such that the transparent pixels of mask 30 correspond to a cross-section of the object to be printed (e.g., a layer of the object). Controller 36 can control beam scanner 26 to selectively scan the beam passing through areas of mask 30 with transparent pixels, while substantially avoiding areas of mask 30 with only opaque pixels. Typically, transparent pixels constitute only a portion of the total pixels (e.g., 30%, 50%, etc.). Assuming these transparent pixels are clustered in certain areas (which is often the case), only these areas of the mask are scanned, thereby greatly reducing the number of opaque pixels unnecessarily illuminated, and consequently reducing heating of mask 30 and resin 18. Specific examples of beam scanning 28 are provided below.

[0046] The controller 36 can also control the light source 24. For example, to further reduce heating of the mask 30, the controller 36 can turn off the light source 24 when the scanner 26 repositions the beam 28 from one area of ​​the mask 30 with transparent pixels to another area of ​​the mask 30 with transparent pixels. The controller 36 can also control the height adjuster 39 to control the vertical position of the lifting plate 20, and thus the vertical position of the object 22 fixed on the lifting plate 20.

[0047] like Figure 2 As shown, the light source 24 may include a laser source 40 that generates a laser beam 42, and a beam expander 44 that converts the collimated and focused laser beam 24 into a collimated and defocused beam 28. For simplicity, the collimated and defocused beam 28 will be referred to as "beam" 28 throughout this specification. Figure 2 As shown, the diameter d2 of the cross-section of the beam 28 can be larger than the diameter d1 of the cross-section of the laser beam 42.

[0048] Figure 3A The mask 30 is described during the exposure duration, during which certain pixels of the mask 30 are controlled to be transparent, while other pixels of the mask 30 are controlled to be opaque (although the mask 30 is not shown in detail with individual pixels visible). For illustration, areas 50 of the mask 30 with opaque pixels are depicted in gray shading, while areas 52 of the mask 30 with transparent pixels are depicted in white (i.e., without any shading). It should be understood that the beam of light scanning through the mask 30 will pass through areas 52 of the mask (and partially cure the layer 34 of the liquid resin 18), while the beam will not pass through areas 50 of the mask. A cross-section 53 approximately corresponding to the object to be printed (see...) is selected. Figure 3A The shape of the area 52 corresponding to the cross section 53 shown in the illustration, the typical size of the mask 30 (i.e., diagonally) can be measured as 13.3 inches, but the size of the mask 30 is expected to increase in the future, so that larger objects can be printed.

[0049] Figure 3B Described Figure 3A The figure shows an enlarged view of portion 54 of mask 30, in which individual pixels (e.g., electromodulated liquid crystal pixel elements) are visible in the enlarged view. Reference numeral 56 indicates one of the opaque pixels of mask 30, and reference numeral 58 indicates one of the transparent pixels of mask 30. For clarity, opaque pixels are represented by gray shading, and transparent pixels are represented by white (i.e., no shading). It should be understood that... Figure 3B The pixel visualizations in the image are for illustrative purposes only and may not represent the actual pixel representation. For example, Figure 3BPixels are depicted using square boundaries, but other boundary shapes are also possible, such as rectangular, elliptical, or circular boundaries. The physical structure of pixels (e.g., liquid crystal sandwiched between two electrodes) is well-known in the art and will not be discussed further here for the sake of brevity.

[0050] Figure 4A The cross-section 60 of the beam 28 on the surface of the mask 30 is described. For ease of discussion, the cross-section 60 may be referred to as the "spot", but if the "illuminated" area of ​​the mask 30 includes transparent pixels, it can be understood that the "spot" may actually be invisible, since the beam 28 can pass through the mask 30 without being reflected from the surface of the mask 30.

[0051] Figure 4B Described Figure 3B An enlarged view of portion 54 of the mask 30 described herein. (See image for details.) Figure 4B As shown, the diameter d2 of the light spot can be an order of magnitude (or more) larger than the cross-sectional size w of each pixel. In one embodiment of the invention, the diameter d2 is at least ten times the cross-sectional size w of each pixel. In another embodiment of the invention, the diameter d2 is at least one hundred times the cross-sectional size w of each pixel. For example, w can be 25-150 μm, while d2 can be 10 mm. In another embodiment of the invention, the diameter d2 of the light spot can be dynamically adjusted according to the cross-sectional size of the object to be manufactured. If the cross-sectional size of the object to be manufactured is on the order of centimeters, then d2 can be measured as 1 cm. If the cross-sectional size of the object to be manufactured is on the order of millimeters, then d2 can be measured as 1 mm. This dynamic adjustment of the light spot diameter can further reduce the irradiation of opaque pixels (thereby reducing the heating of the liquid resin) while maintaining the yield of objects with larger cross-sectional sizes.

[0052] Figure 5 A beam path 62 is described for raster scanning of the transparent region 52 of mask 30. The beam spot moves continuously (i.e., scans) along the beam path 62 on the surface of mask 30. Controller 36 determines the beam path 62 based on the position of the transparent pixels in mask 30 (i.e., the beam path 62 is selected to illuminate the transparent pixels of mask 30 in a uniform manner). It should be understood that thin boundaries of opaque pixels surrounding the transparent region 52 may also be illuminated, thus allowing for some inaccuracies in the position control of the beam spot on mask 30, and also allowing for some inaccuracies in the control of the beam spot diameter. However, the number of illuminated opaque pixels (e.g., in thin boundaries) can be minimized to minimize the heating of mask 30 by beam 28. In the case where transparent pixels are concentrated in a single region (e.g.) Figure 5In some cases, the proportion of opaque pixels illuminated by beam 28 may not exceed 1% (during a single cross-section of the printed object 22). In cases where transparent pixels are concentrated in multiple areas (such as...), the proportion of opaque pixels illuminated by beam 28 may not exceed 1%. Figure 8 In the example shown), the proportion of opaque pixels illuminated may not exceed 10% (when printing a single cross-section of object 22). It should be understood that the spotlights of consecutive "rows" of raster scanning can overlap by several pixels, thus allowing the area 52 to be scanned with uniform light intensity (i.e., uniform intensity, averaged over time). Furthermore, it should be understood that... Figure 5 The beam path 62 described herein can be traced multiple times by beam 28 (once along...). Figure 5 The direction described in the text; the next time along the opposite path; the next time along... Figure 5 (The directions described in the text, and so on). Repeatedly performing a fast scan on a region (e.g., performing 10 fast traversals on beam path 62) may be more ideal than performing a single slow scan on a region (e.g., performing a single traversal on beam path 62) because the heating of resin 18 can be more evenly distributed across the entire layer 34.

[0053] Figure 6 The description covers the opaque region 50 and the transparent region 52 of mask 30 during another exposure duration. Figure 6 In this case, the transparent region 52 is positioned within a "thin band" whose width is smaller than the diameter d2 of the light spot. Therefore, as... Figure 7 As shown, beam 28 can repeatedly scan along beam path 62 in a "back and forth" manner to illuminate the transparent area 52 of mask 30. During this scanning, it should be understood that some opaque pixels in the opaque area 50 may also be scanned by beam 28 (i.e., when beam 28 scans from one transparent area to another), but the number of opaque pixels scanned is greatly reduced compared to the case where the entire mask is scanned by a raster.

[0054] Figure 8 The description covers the opaque region 50 and the transparent region 52 of mask 30 during another exposure duration. Figure 8 In the example, region 64a of mask 30 includes a large number of transparent pixels, as does region 64c, and region 64a and region 64c are separated by region 64b, which contains only opaque pixels. Figure 9The beam paths 62a and 62b that beam 28 may follow when scanning the transparent pixels of mask 30 are described. In one case, beam 28 can repeatedly scan the transparent pixels within region 64a along beam path 62a. Then, beam scanner 26 can reposition beam 28 to region 64c, while beam 28 will not scan region 64b, which contains only opaque pixels. During beam 28 repositioning, controller 36 can either shut off light source 24 or control a blocking element (not shown) to block beam 28. For example, the blocking element may include a baffle of light source 24, which can be controlled by controller 36 to block beam 28. After repositioning, beam 28 can repeatedly scan the transparent pixels within region 64c along beam path 62b. It should be noted that the scanning speed of laser beam 28 in region 64a may differ from the scanning speed of laser beam 28 in region 64c. For example, scanning a smaller region may be slower than scanning a larger region.

[0055] Figure 10 A scanning scheme is described that minimizes scanning of opaque pixels without turning off the light source 24 or blocking the beam 28. Figure 10 In the scanning scheme, beam 28 also scans the transparent pixels within region 64a repeatedly along beam path 62a. However, during the repositioning of beam 28 from region 64a to region 64c, beam 28 scans along beam path 62b. Beam path 62b can be the shortest path through region 64b, connecting beam path 62a within region 64a to beam path 62b within region 64c. After repositioning, beam 28 can scan the transparent pixels within region 64c repeatedly along beam path 62b.

[0056] Figure 11 A 3D printing system 101 is described that employs multiple beams (e.g., two beams) to scan a mask 30. A beam scanner 26a selectively scans a beam 28a originating from a light source 24a that passes through certain areas of the mask 30, and a filtered beam 32a can penetrate through the mask 30 and cure a portion of the resin in layer 34, depending on whether the scanned pixels are transparent or opaque. Similarly, a beam scanner 26b selectively scans a beam 28b originating from a light source 24b that passes through other areas of the mask 30, and a filtered beam 32b can penetrate through the mask 30 and cure a portion of the resin in layer 34, depending on whether the scanned pixels are transparent or opaque. For example, beam 28a can travel along... Figure 10 The beam path 62a moves, while the beam 28b can move along... Figure 10The beam path 62b moves. While this increases the cost of the 3D printing system 101, multi-beam systems offer faster output (i.e., printing speed) compared to single-beam 3D printing systems. For ease of description, Figure 11 Controller 36 is not shown, but it is evident that controller 36 can be used to control beam scanners 26a and 26b, as well as control... Figure 11 Other components previously described.

[0057] Figure 12A A flowchart 102 describes a method for reducing heat generation during the printing of a cross-section of a three-dimensional object. In step 104, controller 36 can, during the exposure time duration, control a first subset of pixels to be transparent at locations corresponding to the cross-section of the (to be printed) three-dimensional object, and control a second subset of pixels to be opaque at locations not corresponding to the cross-section of the three-dimensional object. In step 106, controller 36 can, during the same exposure duration as in step 104, control beam scanner 26 to scan a beam 28 through at least one region of a mask, said at least one region having at least some pixels controlled to be transparent. The scanning can be performed such that during the printing of the cross-section of the three-dimensional object, beam 28 is always incident on at least one pixel in the mask 30 that is controlled to be transparent. This scanning scheme is as follows: Figure 5 , Figure 7 and Figure 9 As shown. Of course, the reduction in heat is most noticeable when transparent pixels account for only a small fraction (or less) of the total number of pixels (e.g., less than 30%-50% of the total number of pixels).

[0058] Figure 12B A flowchart 108 describes another method for reducing heat generation when printing a cross-section of a three-dimensional object. In step 110, the controller 36 can, during the exposure time duration, control a first subset of pixels to be transparent at locations corresponding to the cross-section of the (to be printed) three-dimensional object, and control a second subset of pixels to be opaque at locations not corresponding to the cross-section of the three-dimensional object. In step 112, the controller 36 can, during the same exposure duration as in step 110, control the beam scanner 26 to scan a beam 28 passing through at least one region of the mask, said at least one region having at least some pixels controlled to be transparent. The scanning can be performed such that, when printing the cross-section of the three-dimensional object, the beam 28 scans at most 10% of the pixels controlled to be opaque. This scanning scheme is as follows: Figure 5 , Figure 7 , Figure 9 and Figure 10 As shown. Similarly, the reduction in heat is most noticeable when transparent pixels constitute only a small fraction (or less) of the total number of pixels (e.g., less than 30%-50% of the total number of pixels).

[0059] Figure 13A A flowchart 200 describes a method for scanning a light beam 28 passing through the surface of a mask in a 3D printing system. In step 202, the light beam 28 passing through a first region of the mask 30, including at least some transparent pixels, can be repeatedly scanned. Step 202 is as described above. Figure 9 The transparent pixels within region 64a are scanned in the same manner as described above. In step 204, beam 28 can be repositioned from the first region of the mask to a third region that includes at least some transparent pixels, without scanning the second region of the mask that separates the first and third regions, the second region of the mask comprising only opaque pixels. Figure 9 The beam 28 is repositioned from region 64a to region 64c in the same manner as described above. In step 206, the beam 28, which passes through the mask and includes at least some transparent pixels, can be repeatedly scanned. Step 206 is as described above. Figure 9 The description is the same as that of scanning transparent pixels within region 64c.

[0060] Figure 13B A flowchart 208 describes a method for scanning a light beam 28 passing through the surface of a mask in a 3D printing system. In step 210, the light beam 28 passing through a first region of the mask 30, including at least some transparent pixels, can be repeatedly scanned. Step 210 is as described above. Figure 10 The transparent pixels within region 64a are scanned in the same manner as described above. In step 212, beam 28 may scan along a path within a second region that separates the first and third regions. The second region comprises only opaque pixels, while the third region comprises at least some transparent pixels. This path is the shortest path connecting the beam path in the first region and the beam path in the third region. Step 212 is as described above. Figure 10 The beam 28 is scanned along beam path 62c in the same manner as described above. In step 214, the beam 28, which passes through the mask and includes a third region comprising at least some transparent pixels, can be scanned repeatedly. Step 214 is as described above. Figure 10 The description is the same as that of scanning transparent pixels within region 64c.

[0061] In reality, the light transmittance of individual pixels passing through a mask may exhibit some non-uniformity (e.g., differences exceeding 10% between pixels). For instance, even if a pixel is controlled to be (completely) transparent, it may only be 95% transparent to light due to pixel defects, aging, or other reasons. Therefore, for clarity, the term "transparent pixel" above can refer to pixels that are 100% transparent to light, 99% transparent to light, 95% transparent to light, etc. Similarly, the term "opaque pixel" above can refer to pixels that are 100% opaque to light, 99% opaque to light, 95% opaque to light, etc.

[0062] Figure 14 A flowchart 250 describes a method for printing a cross-section of a three-dimensional object, the method comprising scanning a light beam 28 through the surface of a mask of a 3D printing system such that the scan compensates for non-uniformity in the light transmittance of individual pixels of the mask. In step 252, the uniformity of the light transmittance through the individual pixels of the mask can be evaluated. This evaluation may include controlling all pixels to be (fully) transparent, illuminating the entire mask (e.g., scanning the light beam through the entire mask), and measuring the light intensity transmitted through each pixel. During this initial evaluation, it is assumed that the light intensity of the beam itself is fairly uniform, regardless of whether the beam illuminates the central region or the vicinity of the periphery of the mask. The corresponding locations of any pixels with lower expected light intensity (e.g., reduced light intensity relative to other pixel elements) can be identified.

[0063] In step 254, the controller 36 may, during the exposure duration, control a first subset of pixels to be transparent at locations corresponding to the cross-section of the (to be printed) three-dimensional object, and control a second subset of pixels to be opaque at locations not corresponding to the cross-section of the three-dimensional object. In step 256, the controller 36 may, during the same exposure duration as in step 104, control the beam scanner 26 to scan a beam 28 through at least one region of the mask, said at least one region having at least some pixels controlled to be transparent. The scanning may be performed by compensating for non-uniformity in light transmission across individual pixels in the at least one region of the mask. Compensation may include: (i) changing the light intensity of the beam as the beam scans through the at least one region, (ii) changing the scanning speed of the beam as the beam scans through the at least one region, or (iii) changing the number of times the beam scans through the at least one region. More specifically, for regions where the light output of known pixels (as determined by the evaluation in step 252) is attenuating, the light intensity of the beam may be increased, the scanning speed of the beam decreased, and / or the number of scans through these regions may be increased to compensate for the attenuated light output.

[0064] It is evident from the foregoing discussion that various aspects of the present invention relate to the use of various computer systems and computer-readable storage media thereon storing computer-readable instructions. Figure 15 An example of system 300 is provided, which may represent any computing system discussed herein (e.g., controller 36). Note that not all different computer systems possess all the functionality of system 300. For example, some computer systems discussed above may not include a display screen, because display functionality may be provided by a client computer communicatively coupled to the computer system, or display functionality may be unnecessary. These details are not important to the present invention.

[0065] System 300 includes a bus 302 or other communication mechanism for communicating information, and a processor 304 coupled to the bus 302 for processing information. Computer system 300 also includes a main memory 306 (such as random access memory (RAM) or other dynamic storage device) coupled to the bus 302, which stores information and instructions to be executed by the processor 304. Main memory 306 can also be used to store temporary variables or other intermediate information during instruction execution by the processor 304. Computer system 300 also includes a read-only memory (ROM) 308 or other static storage device coupled to the bus 302 for storing static information and instructions for the processor 304. A storage device 310 (e.g., a hard disk, flash-based storage medium, or other storage medium readable by the processor 304) coupled to the bus 302 is provided for storing information and instructions (e.g., operating system, applications, etc.).

[0066] Computer system 300 can be coupled to display 312 (e.g., a flat panel display) via bus 302 for displaying information to the computer user. Input device 314 (e.g., a keyboard including letter, number, and other keys) can be coupled to bus 302 and used to transmit information and command selections to processor 304. Another type of user input device is cursor control device 316 (e.g., a mouse, touchpad, or similar input device) used to transmit directional information and command selections to processor 304 and control cursor movement on display 312. Other user interface devices, such as microphones and speakers, are not shown in detail, but these devices may also be involved in receiving and / or outputting user input.

[0067] The processes described herein can be implemented by processor 304 executing appropriate sequences of computer-readable instructions contained in main memory 306. Such instructions may be read into main memory 306 from another computer-readable medium (e.g., storage device 310), and executing the sequence of instructions contained in main memory 306 causes processor 304 to perform the relevant operations. In other embodiments, a hardwired or firmware-controlled processing unit may be used instead of processor 304 and its associated computer software instructions, or a hardwired or firmware-controlled processing unit may be used in conjunction with processor 304 and its associated computer software instructions to implement the invention. The computer-readable instructions may be presented in any computer language.

[0068] Generally, all the above descriptions of processes are intended to cover any series of logical steps executed sequentially to achieve a given purpose, which is also the hallmark of any computer-executable application. Unless otherwise specified, it should be understood that throughout this specification, terms such as “processing,” “operation,” “calculation,” “determining,” “displaying,” “receiving,” “transmitting,” or similar terms refer to the operation and processes of a suitably programmed computer system (e.g., computer system 300 or similar electronic computing device) that manipulates and converts data represented as physical (electronic) quantities in its registers and memories into other data also represented as physical quantities in its memory or registers or other such information storage, transmission, or display devices.

[0069] Computer system 300 also includes a communication interface 318 coupled to bus 302. Communication interface 318 provides a bidirectional data communication channel to a computer network, thereby providing connectivity with and between the various computer systems described above. For example, communication interface 318 may be a local area network (LAN) card for providing data communication connectivity with a compatible LAN, which itself is communicatively coupled to the Internet via one or more Internet service provider networks. However, these detailed aspects of the communication path are not important to this invention. What is important is that computer system 300 can send and receive information and data through communication interface 318 and communicate with hosts accessible via the Internet in this manner.

[0070] Therefore, methods and systems for photocuring liquid resins and reducing heat generation have been described. It should be understood that the above description is illustrative and not limiting. Many other embodiments will be apparent to those skilled in the art upon reading the above specification. Therefore, the scope of the invention should be determined by reference to the appended claims and the full scope of their equivalents.

Claims

1. A photopolymerization and curing printer (100) comprising a tank (10) configured to contain a photopolymerizable liquid resin (18), a light source (24) configured to emit a light beam (28), a mask (30) having pixels (56, 58) configured to be transparent or opaque to portions of the light beam (28), wherein the diameter (d2) of the cross-section (60) of the light beam (28) is greater than the dimension (w) of the cross-section of each respective pixel (56, 58), a beam scanner (26) configured to scan the light beam (28) passing through the mask (30), and a controller (36) having a memory (306) and a processor (304), the memory (306) storing instructions which, when executed, cause the processor (304) to control the photopolymerization and curing printing. A photopolymerization printer (100) is used to print a cross-section (53) of a three-dimensional object (22), wherein the processor (304) controls the photopolymerization printer (100) to print the cross-section (53) of the three-dimensional object (22) by means of the following steps: during the exposure duration, controlling a first subset of pixels of a mask (30) to be transparent at positions corresponding to the cross-section (53) of the three-dimensional object (22), and controlling a second subset of pixels of the mask (30) to be opaque at positions not corresponding to the cross-section (53) of the three-dimensional object (22); and during the exposure duration, controlling a beam scanner (26) to scan a beam (28) passing through one or more regions of the mask (30) such that the beam (28) always incident on at least one of the pixels (58) of the mask (30) that are controlled to be transparent, characterized in that, During the exposure duration, the instruction further causes the processor (304) to turn off the light source (24), while the beam scanner (26) repositions the beam (28) from a first region (64a) of the mask (30) comprising at least some pixels (58) controlled to be transparent to a third region (64c) of the mask (30) comprising at least some pixels (58) controlled to be transparent, the third region (64c) of the mask (30) being separated from the first region (64a) of the mask (30) by a second region (64b) of the mask (30) comprising only pixels (56) controlled to be opaque.

2. The photopolymerization and curing printer (100) according to claim 1, wherein the diameter (d2) of the cross section (60) of the light beam (28) is at least ten times the size (w) of the cross section of each corresponding pixel (56, 58).

3. The photopolymerization and curing printer (100) according to claim 1, wherein the diameter (d2) of the cross section (60) of the light beam (28) is at least one hundred times the size (w) of the cross section of each corresponding pixel (56, 58).

4. The photopolymerization and curing printer (100) according to claim 1, wherein during the printing of the cross section (53) of the three-dimensional object (22), the light beam (28) scans at most 10% of the pixels (56) that are controlled to be opaque.

5. The photopolymerization and curing printer (100) according to claim 1, wherein the light source (24) comprises: A laser source (40) configured to emit a laser beam (42); as well as A beam expander (44) is configured to generate a beam (28) from a laser beam (42), wherein the diameter (d2) of the cross section (60) of the beam (28) is greater than the diameter (d1) of the cross section of the laser beam (42).

6. The photopolymerization and curing printer (100) according to claim 1, wherein the instructions further cause the processor (304) to determine the scanning path (62, 62a, 62c) of the light beam (28) based on the corresponding position of the pixels (58) controlled to be transparent during the exposure duration.

7. A method for printing a cross-section (53) of a three-dimensional object (22) in a photocurable region (34) of a photopolymerization and curing printer (100), the photopolymerization and curing printer comprising: (i) a tank (10) configured to contain photocurable liquid resin (18); (ii) a flexible film (14) defining the bottom boundary of a photocurable region (34); (iii) a light source (24) configured to emit a light beam (28); (iv) a beam scanner (26) configured to scan the light beam (28); and (v) a mask (30) disposed between the beam scanner (26) and the flexible film (14), wherein the mask (30) has pixels that can be configured to be transparent or opaque to portions of the light beam (28), wherein the diameter (d2) of the cross section (60) of the light beam (28) is greater than the dimension (w) of the cross section of each corresponding pixel (56, 58), the method comprising: In control step (110), during the exposure duration, a first subset of control pixels (58) are transparent at positions corresponding to the cross section (53) of the three-dimensional object (22), and a second subset of control pixels (56) are opaque at positions not corresponding to the cross section (53) of the three-dimensional object (22); and In the scanning step (112), during the exposure duration, a beam (28) passing through at least one region (64a, 64c) of the mask (30) and entering the photocuring region (34), the at least one region having at least some pixels (58) controlled to be transparent, wherein during the printing of the cross section (53) of the three-dimensional object (22), the beam (28) scans at most 10% of the pixels (56) controlled to be opaque. Among them, by controlling the first subset and the second subset of pixels, the first region (64a) of the mask (30) includes at least some pixels (58) controlled to be transparent, the second region (64b) of the mask (30) includes only pixels (56) controlled to be opaque, and the third region (64c) of the mask (30) includes at least some pixels (58) controlled to be transparent. The feature is that the scanning of the beam (28) includes repeatedly scanning the beam (28) that passes through the first region (64a) of the mask (30) and enters the photocurable region (34) through the pixels (58) controlled to be transparent in the first region (64a), repositioning the beam (28) from the first region (64a) of the mask (30) to the third region (64c) of the mask (30) without scanning the second region (64b) of the mask (30), and repeatedly scanning the beam (28) that passes through the third region (64c) of the mask (30) and enters the photocurable region (34) through the pixels (58) controlled to be transparent in the third region (64c).

8. The method according to claim 7, wherein repeated scanning of the beam (28) passing through the first region (64a) of the mask (30) includes at least one of raster scanning or back-and-forth scanning of the first region (64a) of the mask (30), and wherein repeated scanning of the beam (28) passing through the third region (64c) of the mask includes at least one of raster scanning or back-and-forth scanning of the third region (64c) of the mask (30).

9. The method of claim 7, wherein during the exposure duration, the total number of pixels in the first subset of pixels is less than the total number of pixels in the second subset of pixels.

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