WO2018204938A2

WO2018204938A2 - Scanning vat-photopolymerization

Info

Publication number: WO2018204938A2
Application number: PCT/US2018/040481
Authority: WO
Inventors: Viswanath MEENAKSHISUNDARAM; Christopher B. WILLIAMS
Original assignee: Virginia Tech Intellectual Properties Inc.; Compagnie Générale Des Etablissements Michelin
Priority date: 2017-04-30
Filing date: 2018-06-29
Publication date: 2018-11-08
Also published as: WO2018203867A1; WO2018204938A3

Abstract

A scanning vat-photopolymerization system and method for producing a three- dimensional shape on a build layer in a single scan. The three-dimensional shape is created by variably applying energy during the exposure of one or more scanned sections or voxels of the build layer in a single scan.

Description

TITLE

SCANNING VAT-PHOTOPOLYMERIZATION

RELATED APPLICATIONS

[0001] This application is a continuation in part of PCT/US2017/030316, which is incorporated herein by reference.

BACKGROUND OF THE INVENTION

[0002] Vat-Photopolymerization (VP) is an Additive Manufacturing process where light of a particular wavelength is used to cure a liquid resin or photopolymer to a solid part. Mask Projection Vat-Photopolymerization is a modification to the traditional VP technique, where a digital masking device is used to generate and project patterns on the surface of a photocurable resin. Digital masks such as Digital Micro-Mirror Devices (DMD), Liquid Crystal Devices (LCD) and Liquid Crystal on Silicon (LCOS) can be used to generate and reflect patterns.

BRIEF SUMMARY OF THE INVENTION

[0003] In one embodiment, the present invention provides a VP system and method wherein the pattern mask is scanned at non-uniform speeds to create three- dimensional objects, patterns as well as shapes of varying or graded thickness profiles through an area of film.

[0004] In other embodiments, the present invention provides a VP system and method wherein the pattern mask is scanned with different light intensities to create three- dimensional objects, patterns as well as shapes of varying or graded thickness profiles through an area of film.

[0005] In one embodiment, the present invention provides a VP system and method wherein the pattern mask is scanned at non-uniform speeds and varying light intensities to create three-dimensional objects, patterns as well as shapes of varying or graded mechanical properties through an area of film.

[0006] In one embodiment, the present invention provides a VP system and method wherein the pattern mask is scanned at non-uniform speeds and varying light intensities to create three-dimensional objects, patterns as well as shapes of varying or graded thickness profiles and graded mechanical properties through an area of film..

[0007] In a preferred embodiment, the present invention provides a VP system and method that can produce smooth cavities in a single pass. In addition, the present invention can create curved, arcuate and other surface features that vary in height in a single pass.

[0008] In other embodiments, the present invention provides a VP system and method wherein the frame rate of the moving mask is matched with a velocity profile to achieve a predetermined profile on the film.

[0009] In yet other embodiments, the present invention provides a VP system and method that can make textures on the resin, without having to make multiple passes. Textures may be printed on existing parts such as shoes, gloves, and tires. Also, complex patterns can be generated for creating new and unique tread patterns. Moreover, monolayer patterns can be printed on test specimens for preliminary evaluation.

[00010] In still other embodiments, the present invention provides a VP system and method that can manufacture large area and high-resolution parts.

[00011] In other embodiments, the present invention provides a process to make parts and objects with varying thickness without having multiple layers and intermediate recoating steps used in the VP process. With the elimination of the recoating step, the manufacturing speed is increased significantly.

[00012] In still other embodiments, the present invention provides a VP system and method that overcomes the effects of stair-stepping by using appropriate velocity profiles and pixel blending.

[00013] In still other embodiments, the present invention provides a VP system and method for use in the automobile industry. Complex patterns can be created, with high- temperature polymers and ceramic printing technologies, for heat exchangers and catalytic converters at a fraction of the cost by eliminating the need to use

micromachining.

[00014] In still other embodiments, the present invention provides a VP system and method for use in making apparel. The embodiments of the present invention allow for the rapid manufacturing of custom shoe grips, glove grips, and other textured sports apparel. Due to the large manufacturing area, multiple custom components can be built at the same time.

[00015] In still other embodiments, the present invention provides a VP system and method that may be used to produce complex shapes in a single layer using a single pass. The embodiments of the present invention may be used to produce structures having little to no interlayer interfaces which reduces cracks propagation sites in a build layer.

[00016] In other embodiments, the present invention provides a VP system and method for use in making implants and planar cell scaffolds. The embodiments of the present invention may be used to manufacture planar scaffolds for cell growth and for making implants like partial dental crowns. The embodiments of the present invention may also be used to manufacture intricate single layer stents and sheaths for nerve repair. Apart from structural members, the thin films can also be used for controlled drug delivery through differential-dissolution.

[00017] In further embodiments, the present invention provides a VP system and method for use in making films that may be used to manufacture purification membranes for water treatment apparatus. Also, gas separation membranes may be made by controlling the feature sizes in the nanometer scale.

[00018] In further embodiments, the present invention provides a VP system and method for producing a three-dimensional shape on a build layer in a single scan by variably exposing one or more scanned units and/or voxels of the build layer in a single scan. The scanning is a continuous movement which may have a variable scanning speed, a variable intensity, or both.

[00019] In further embodiments, the present invention provides a scanning vat- photopolymerization system and method for producing a three-dimensional shape on a build layer in a single scan by varying the thickness in one or more scanned units by varying the energy applied to each scanned unit.

[00020] In further embodiments, the present invention provides a system and method wherein the thickness is varied by changing the exposure depth of the scanned units and/or voxels. Also, the scan may be a continuous movement having a variable scanning speed, a variable intensity, or both.

[00021] In other aspects, the present invention provides a system and method wherein further including the steps of determining the active-pixel density from the bitmap image of the geometry; determining the required number of pixel translations to create a mask for the required geometry; and determining the frame rate for each pixel transition to achieve the energy for creating a predetermined thickness on a specific region of the build layer. [00022] It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention, as claimed.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

[00023] In the drawings, which are not necessarily drawn to scale, like numerals may describe substantially similar components throughout the several views. Like numerals having different letter suffixes may represent different instances of substantially similar components. The drawings illustrate generally, by way of example, but not by way of limitation, a detailed description of certain embodiments discussed in the present document.

[00024] Figure 1 is a schematic of a mask projection vat-photopolymerization.

[00025] Figure 2 is a schematic of a Scanning Mask Projection Vat-Photopolymerization machine.

[00026] Figure 3 provides a working schematic for scanning vat-photopolymerization.

[00027] Figure 4A is a schematic of a variable exposure scanning vat- photopolymerization machine for one embodiment of the present invention.

[00028] Figure 4B provides an example velocity profile used in connection with the embodiment shown in Figure 4A.

[00029] Figure 5 illustrates a generated pixel pattern (left) and an effective pixel pattern (right).

[00030] Figure 6A provides a general process flow for one embodiment of the present invention.

[00031] Figure 6B provides a slice generation algorithm.

[00032] Figure 6 is a flowchart showing gray-scaling to obtain patterns with varying thickness.

[00033] Figure 7 illustrates an example pattern to be printed (left) and a velocity profile required for printing the pattern (right).

[00034] Figure 9 illustrates the different thicknesses observed in a single layer for an embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

[00035] Detailed embodiments of the present invention are disclosed herein; however, it is to be understood that the disclosed embodiments are merely exemplary of the invention, which may be embodied in various forms. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a representative basis for teaching one skilled in the art to variously employ the present invention in virtually any appropriately detailed method, structure or system. Further, the terms and phrases used herein are not intended to be limiting, but rather to provide an understandable description of the invention.

[00036] Scanning Vat-Photopolymerization represents an improvement for Mask Projection Vat-Photopolymerization machines to facilitate the manufacturing of large area parts with very high resolution. A mask projection unit, such as a DLP® projector, is directly mounted on an XY linear stage instead of a fixed pillar, as in the case of a traditional mask projection Vat-Photopolymerization machines.

[00037] Figure 1 shows a schematic of a Mask Projection VP system 100. Light emitted from source 102 is collimated, clipped and transmitted by optics 104-105 and mirror 106 to and from DMD 108. A computer 110 is used to generate and relay a bitmap representation of a single layer of the desired 3D part on DMD 108.

[00038] White pixels, representing the desired pattern, are created by tilting the corresponding micro-mirrors to the ON' state. Black pixels, representing the voids or uncured areas, are created by tilting the corresponding micro-mirrors to the OFF' state. When the collimated light impinges on the DMD, the ON' pixels reflect the light perpendicular to the surface of the resin, projecting a pattern, and the OFF' pixels reflect the light away from the projection optics. The irradiated part of the resin surface undergoes photopolymerization and cures in the shape of the projected pattern. Once a layer of desired thickness is cured, the build platform is lowered into the resin by a depth of one-layer thickness. The process is repeated until the entire 3D part is built layer-by-layer in a time-consuming manner.

[00039] Figure 2 shows a typical setup of a Scanning Mask Projection Vat- Photopolymerization machine 200. A common light source 202 such as a laser, Light Emitting Diode (LED) or a broad-spectrum Ultra Violet (UV) light source is focused into projector 204, which may be a DLP® projector, with the help of imaging optics 206, which may be a collimator or a light guide respectively. Appropriate imaging and projection optics are attached to the projector depending on the requirements such as projected pixel size, projection area, projected pixel intensity and manufacturing time. A computer 210 is used for the generation of the dynamic moving mask and the synchronous control commands for the projector, and the X, Y and Z linear stages. [00040] Figure 3 shows the working schematic of the scanning Mask Projection Vat- Photopolymerization machine 200. The build platform is lowered to one-layer thickness below the resin surface. At position 1, only the first pixel is 'Switched On' to cure a square on the resin surface. When the projector moves to position 2, the first pixel is maintained in the ON' position, curing another square. As the projector scans the surface of the resin at a predetermined speed from position 1 through 5, a line of uniform layer thickness is cured on the resin surface.

[00041] A layer of required thickness is obtained by moving the projector at a scan speed that exposes every pixel with a predetermined constant irradiance. For example, if curing square 300 shown in Figure 3, required 2 seconds, then the moving mask and the scan speed are synchronized such that every pixel is consecutively exposed for 2 seconds over the entire scanning time.

[00042] A single pixel model is illustrated in Figure 3 to reduce the complexity of the concept. However, any complex 2D pattern (i.e., multiple pixels) can be sent to the projector in the form of moving mask, and the same can be cured onto the surface of the resin. The achievable part size is determined by the length of the linear stages and not the optics, as in traditional VP machines. A complete 3D part can be obtained by lowering the build platform and repeating the steps discussed above.

[00043] Accordingly, 3D parts are created by a continuous scanning process wherein the scan speed is maintained constant throughout the scan. This results in cured layers having uniform thicknesses because they are exposed to equal UV radiation throughout the scan. These methods require multiple layers to generate textured films.

[00044] In a preferred embodiment of the present invention, the scan speed during the printing of a single layer is varied depending on the thickness desired for a

predetermined area of a layer. This enables the embodiments of the present invention to facilitate the manufacturing of large area, high resolution textured films at high speeds. For this embodiment, the pattern mask is scanned at non-uniform or variable speeds to create a graded thickness profile through the area of the film.

[00045] Figure 4A and 4B provide an exemplary velocity profile that may be used to generate the pattern shown. As the scan speed increases, the effective UV irradiation on the resin reduces and thus lowers the layer thickness of the cure part. The reverse happens when the scan speed is lowered. For complex patterns, the frame rate of the moving mask is matched with the velocity profile to achieve the required profile on the film at a predetermined location.

[00046] Figure 5 shows an exemplary layer 500 having a surface 502 that may be obtained in a single pass using the embodiments of the present invention. As shown, layer 500 has a non-uniform thickness and is comprised of sections, printed units, scanned units and/or voxels 510-514 each of which has discrete exposure values and corresponding depths of exposure. Section 512 was made by applying the least amount of energy as compared to the other sections shown. This may be accomplished by using the highest value velocity profile, the lowest intensity, or a combination of both. As shown, 512 has a depth of exposure (x) in this instance as compared with sections, scanned units and/or voxels 510, 511, 513 and 514. Scanned sections 510 and 514 were made using the highest applied energy levels, such as the lowest velocity profile or highest intensity level. Sections 510 and 514 have a depth of exposure in this instance of twice (2x) that of 512. Sections 511 and 513 were made using applied energy levels in between the other profiles and have a depth of exposure of in this instance of one point five (1.5x) that of 512. By changing the energy applied to a predetermined section, a wide variety of surface profiles may be obtained. These surface features include curved, arcuate, concave, convex, ramped, peaked, valley-like as well as other three-dimensional shapes.

[00047] However, since the velocity profile is linear, the staircase effect may be eliminated from the cured part - which is typical in a layer-by-layer manufacturing approach. The embodiments of the present invention can produce parts/features with improved surface finish compared to current printed parts. The improvements include smooth transitions in layer thickness.

[00048] To print the same feature with continuous velocity VP techniques, it would require multiple passes, whereas the proposed technique could print the patterned film in one pass.

[00049] The general process flow for the proposed process is shown in Figure 6A. The .STL file of the part is sliced into a bitmap image - that represents the required pattern. The bitmap image is formatted such that the resolution matches that of the projector

(1024x768 pixels as in the above case). The corrected image is sliced one-pixel row at a time using a slicing algorithm. The generated slices are stitched together as a movie using the movie generation algorithm. During this process, a velocity profile is created depending on the required pattern. The generated movie is projected, and the required velocity profile is applied to the stages. This cures a pattern on the surface of the resin with varying thicknesses.

[00050] The slice generation algorithm is shown in Figure 6B. Depending on the thickness required at specific regions in the pattern, the algorithm translates the required number of pixels and creates a static mask. Once the entire image is processed, the algorithm combines the static masks and creates a movie with a varying framerate. Further, machine learning algorithms can be used to tune the frame-rate of the movie, depending on the location and density of active-pixels on the DMD, to achieve the desired exposure profile.

[00051] The required velocity profile is provided as a waveform to the actuator such that the framerate of the movie and the velocity profile of the actuator are synchronous.

[00052] Table 1 shows the various subsystems that may be used to generate the high- resolution patterns described above for the various embodiments of the present invention.

[00053] Combinations that may be used with the various embodiments of the present invention include a 365 nm LED source with an LCD mask can be used to project patterns on pre-existing substrates using rotary actuators. The material could be a photopolymer+ solvent system placed in an inert atmosphere of nitrogen.

[00054] Depending on the resin properties, the thickness of the desired patterned film can be varied by altering the layer thickness - when a platform is used, or can be directly lifted off the surface of the resin.

[00055] The high resolution three and two-dimensional patterns may also be manufactured by varying the intensity of the light used. As the intensity increases, the effective UV irradiation on the resin increases and thus increases the layer thickness of the cure part. The reverse happens when intensity is lowered. For complex patterns, the intensity is matched with the velocity profile to achieve the required profile on the film at a predetermined location as the film is scanned.

[00056] In yet other embodiments, both the intensity and velocity may be varied. In other aspects, the intensity and velocity may be alternately varied as desired as the film is scanned.

Table 1 : Table showing the various combinations for the scanning vat photopolymerization machine

[00057] In addition to changing the intensity of the light applied at the light source, intensity may also be varied by selective gray-scaling of the input image. The pixel grayscale can be set such that the overall intensity reflected by the pixel is just enough to cure the photocuring resin to the required thickness. This process can again be used with any of the elements shown in Error! Reference source not found..

[00058] Figure 8 shows an example pattern with varying thickness and pattern along its area. Initially, the moving mask containing the pixel pattern throughout the area is generated. Next, the scan speed and/or intensity as well as the frame rate of the mask movie are adjusted and synchronized as shown in the velocity profile in Figure 8.

[00059] Figure 9 shows a part printed using the concept proposed in the document. A thin film was printed using a commercial resin and a linearly increasing velocity profile. The printed film thickness was varied from 137 μιη to 76 μιη.

[00060] Examples

[00061] The present invention is further illustrated by the following examples. It is to be understood that the present invention is not limited to the examples, and various changes and modifications may be made in the invention without departing from the spirit and scope thereof.

[00062] Example 1

[00063] Ring-opening of pyromellitic dianhydride (PMDA) with 2 -hydroxyethyl acrylate, subsequent acyl chloride formation, and step-growth polymerization using 4,4- oxydianiline (ODA) afforded a photocurable, soluble PMDA-ODA polyamic diacrylate ester (PADE) with a molecular weight of Mn= 49100 'gmol-1. The polymer was precipitated in an ice-cold 1:1 mixture of water and methanol, filtered and dried under vacuum. For 3D printing, the polymer was redissolved in N -methyl -2 -pyrrolidone (NMP) to yield a solution of 15 wt% solids. 2.5 wt% phenylbis(2,4,6

trimethylbenzoyl)phosphine oxide (PPO) served as photoinitiator. The solution was filled into the vat of the printer which may be for a preferred embodiment a Mask- Projection Scanning Stereolithography printer. A working curve was obtained by shining broad-spectrum UV-Vis light at 20 mW/cm2 and measuring the cured film thickness at various exposure times. A dynamic moving mask was generated for the tensile specimens to cure layers with a thickness of 150 μιη. The tensile specimens were printed at a scan speed of 2.6 mm/s. A recoating step was performed between layers to ensure uniform layer thickness and homogeneity throughout the build volume. The final printed part was carefully removed from the glass slide and cleaned with 50:50 butyrolactone/acetone mixtures. A careful drying and heating procedure yielded PMDA- ODA polyimide parts.

[00064] Example 2

[00065] Various molar ratios of poly(dimethylsiloxane) thiol terminated (PDMS-SH) and acrylamide terminated (PDMS-AA), or neat PDMS-AA at various MWs, totaling 2.00 g, were weighed into a 2 -dram scintillation vial, and all samples for a single study were prepared at once. Separately, TPO (1.00 g) and chloroform (5.00 g) were weighed into a 6 -dram scintillation vial and mixed with a vortexer for 10 s; this solution was designated the photoinitiator stock solution. Finally, a 10-, 25-, or 100 -microliter syringe ensured the proper amount of photoinitiator stock solution to control TPO loadings at 0.5 wt %. Finally, photoinitiated mixtures were mixed with a vortexer for 60 s until homogeneous and subsequently allowed to stand for 2 h to ensure the absence of bubbles. Due to high oxygen solubility in PDMS relative to other polymers, printing in an inert environment helped to prevent oxygen diradical from terminating growing polyacrylamide chains. VPP proceeded under nitrogen sparge in an attempt to exclude oxygen from the printing process. Preliminary printed objects, unfortunately, contained bubbles as an artifact of the nitrogen sparge, but careful examination of tensile specimens enabled selection of dog bones with bubble- and otherwise defect-free gauge lengths. VPP AM of tensile specimens demonstrated well-defined geometries and optically clear printed objects. The STL file of the required part was sliced into 150 μιη layers and pre-processed to form a moving mask with a frame rate of 256

frames/second for every layer. A photopolymer-filled glass vat was placed in the projection area with the photopolymer surface in level with the printer focus. To ensure removal of dissolved oxygen, nitrogen was bubbled through the photopolymer for 10 min. A glass slide was fixed to the build platform and lowered into photopolymer to flush the slide surface with the photopolymer surface. The flow rate of nitrogen was adjusted to continuously flood the build chamber and the photopolymer vat with fresh nitrogen. A preliminary recoating step ensured the deposition of a 150 μιη

photopolymer layer on the build platform. The moving mask, corresponding to the first layer, was projected on the surface of the photopolymer with a scan speed of 2.764 mm/s. The build platform was lowered into the photopolymer and an inter-layer recoating step was performed to deposit 150 μιη layer of photopolymer on the cured part. The projection and recoating steps continued until all the slices of the required part were printed. Extracted parts were rinsed with IPA and dried with clean wipes.

[00066] Example 3

[00067] Hydrogenated polybutadiene diol oligomer (2,000 g/mol) was reacted with excess acryloyl chloride and potassium carbonate which afforded a liquid, reactive diacrylate precursor. The product was stirred with basic aluminum oxide 12 h and dried in vacuo overnight to yield a clear liquid. In a typical example, 100 g of hydrogenated polybutadiene diacrylate (HPBDA) was mixed with 2 wt% diphenyl(2,4,6- trimethylbenzoyl)phosphine oxide (TPO) photoinitiator and various stoichiometric ratios of 1,6-hexanedithiol, ranging from 0 to 100 mol%. The STL files were sliced into bitmaps of 200μιη layer thickness using Netfabb. A custom MATLAB program generated a moving mask for each layer and the corresponding scan speed based on the exposure time estimated from the working curves. A glass vat filled with resin was loaded into the build area. Glass slides were attached to the build platform to enhance the adhesion between the printed parts and the substrate. The projector traversed over the resin surface while projecting the moving mask over the resin. Recoating was performed by lowering the build stage into the resin vat. After a brief pause for resin settling, a recoating blade smoothened meniscus over the build platform, ensuring a smooth and level resin surface for fabrication of the consequent layers. This process continued until the entire part was fabricated. During fabrication, the linear stages, the projector, and the recoating mechanism are actively monitored and controlled using a custom

LabVIEW program. The printed parts, extracted from the build platform, were rinsed with 1-Propanol and wiped with Kimwipes™ to remove uncured photopolymer. Glass Petri dishes, containing 20 ml of the synthesized resin, were irradiated with UV light for a duration of 3, 5, 7 and 10 seconds. The intensity of the incident light was estimated to be 600 mW/cm2 over the 300-500 nm spectrum. A working curve was generated by plotting the mean thickness of the extracted films, derived from four repetitions, against their corresponding incident energies. The exposure time and the scan speed for curing a 200μιη layer were extrapolated from the working curves. 0.15 wt.% of a commercial UV blocker, BBOT, was added to the system to improve the resolution. From the working curves, the exposure time was determined to be 3 seconds which

corresponded to a scan speed of 2.76 mm/s. [00068] While the foregoing written description enables one of ordinary skill to make and use what is considered presently to be the best mode thereof, those of ordinary skill will understand and appreciate the existence of variations, combinations, and equivalents of the specific embodiment, method, and examples herein. The disclosure should therefore not be limited by the above-described embodiments, methods, and examples, but by all embodiments and methods within the scope and spirit of the disclosure.

Claims

WHAT IS CLAIMED IS:

1. A scanning vat-photopolymerization method for producing a three-dimensional shape on a build layer in a single scan, comprising the steps of;

generating a non-uniform velocity profile for the three-dimensional shape to be produced on the build layer; and

utilizing said non-uniform velocity profile to cause the build layer to be scanned with a dynamically changing pattern mask at a non-uniform speed to create the three- dimensional shape on the build layer.

2. The method of claim 1 wherein the three-dimensional shape has a graded thickness profile through a predetermined area of the build layer.

3. The method of claim 1 wherein by changing the velocity profile for a

predetermined section, curved, arcuate, concave, convex, ramped, peaked, and valleylike shapes are produced on said predetermined section in a single scan on the build layer.

4. The method of claim 1 further including the steps of translating the required number of pixels to create a mask where individual pixels provide enough energy to create a predetermined thickness on a specific region of the build layer.

5. The method of claim 4 further including the step of creating a movie with a varying frame rate corresponding to the shape to be created on the build layer.

6. The method of claim 5 wherein said velocity profile is provided as a waveform to an actuator such that the framerate of the movie and the velocity profile of the actuator are synchronous.

7. The method of claim 1 wherein the three-dimensional shape has a smooth surface made by a single scanning pass, said scanning pass having a linear velocity profile.

8. The method of claim 7 wherein said surface does not have a stair-stepping effect.

9. An article of manufacture having an outer surface, such as a tire, made in accordance with the method of claim 8.

10. The method of claim 8 wherein said surface is made by using a non-uniform velocity profile and pixel blending.

11. The method of claim 1 wherein the light intensity is varied during scanning.

12. The method of claim 11 wherein the scanning is a continuous movement having a changing scanning speed, changing intensity, or both.

13. A scanning vat-photopolymerization system for producing a three-dimensional shape on a build layer in a single scan,, comprising:

a light source, a projector, and a processor, said processor adapted to generate a moving mask and control commands for the projector, said control commands include a non-uniform velocity profile configured to cause the build layer to be scanned with a pattern mask at a non-uniform speed to create a three-dimensional shape on the build layer.

14. The system of claim 13 wherein the three-dimensional shape has a graded thickness profile through a predetermined area of the build layer.

15. The system of claim 13 wherein by changing the velocity profile for a predetermined section, surface features including curved, arcuate, concave, convex, ramped, peaked, and valley-like shapes are produced.

16. The system of claim 13 wherein said processor is configured to determine the active-pixel density from the bitmap image of the geometry; the required number of pixel translations to create a mask for the required geometry; and

the frame rate for each pixel transition to achieve the energy for creating a

predetermined thickness on a specific region of the build layer.

17. The system of claim 16 wherein said processor creates a movie with a varying frame rate corresponding to the shape to be created on the build layer.

18. The system of claim 17 wherein said velocity profile is provided as a waveform to an actuator such that the framerate of the movie and the velocity profile of the actuator are synchronous.

19. The system of claim 13 wherein the three-dimensional shape has a smooth surface made by a single scan having a linear velocity profile.

20. The system of claim 13 wherein intensity of said light is varied during scanning.

21. A scanning vat-photopolymerization method for producing a three-dimensional shape on a build layer in a single scan, comprising the steps of:

varying the thickness in one or more scanned units by varying the energy applied to each scanned unit.

22. The method of claim 21 wherein the thickness is varied by changing the exposure depth of said scanned units.

23. The method of claim 21 wherein the scan is a continuous movement having a variable scanning speed, a variable intensity, or both.

24. The method of claim 21 wherein the scanned unit is a voxel.

25. The method of claim 21 wherein further including the steps of determining the active-pixel density from the bitmap image of the geometry; determining the required number of pixel translations to create a mask for the required geometry; and determining the frame rate for each pixel transition to achieve the energy for creating a predetermined thickness on a specific region of the build layer.

26. A scanning vat-photopolymerization method for producing a three-dimensional shape on a tire in a single scan, comprising the steps of:

generating a non-uniform velocity profile for the three-dimensional shape to be produced on the tire; and

utilizing said non-uniform velocity profile to cause the tire to be scanned with a dynamically changing pattern mask at a non-uniform speed to create the three- dimensional shape on the tire.

27. The method of claim 26 wherein the three-dimensional shape has a graded thickness profile through a predetermined area of the tire.

28. The method of claim 26 wherein by changing the velocity profile for a predetermined section, curved, arcuate, concave, convex, ramped, peaked, and valley- like shapes are produced on said predetermined section in a single scan on the tire.

29. The method of claim 26 further including the steps of translating the required number of pixels to create a mask where individual pixels provide enough energy to create a predetermined thickness on a specific region of the tire.

30. The method of claim 29 further including the step of creating a movie with a varying frame rate corresponding to the shape to be created on the tire.

31. The method of claim 26 wherein said velocity profile is provided as a waveform to an actuator such that the framerate of the movie and the velocity profile of the actuator are synchronous.

32. The method of claim 26 wherein the three-dimensional shape has a smooth surface made by a single scanning pass.

33. The method of claim 26 wherein the three-dimensional shape has a smooth surface made by a single scanning pass, said scanning pass having a linear velocity profile.

34. The methods of claims 32 and 33 wherein said surface does not have a stairstepping effect.

35. The method of claim 33 wherein said surface is made by using a non-uniform velocity profile and pixel blending.

36. The method of claim 26 wherein the light intensity is varied during scanning.

37. The method of claim 36 wherein the scanning is a continuous movement having a changing scanning speed, changing intensity, or both.

38. A scanning vat-photopolymerization system for producing a three-dimensional shape on a tire in a single scan, comprising:

a light source, a projector, and a processor, said processor adapted to generate a moving mask and control commands for the projector, said control commands include a non-uniform velocity profile configured to cause the tire to be scanned with a pattern mask at a non-uniform speed to create a three-dimensional shape on the tire.

39. The system of claim 38 wherein the three-dimensional shape has a graded thickness profile through a predetermined area of the tire.

40. The system of claim 38 wherein by changing the velocity profile for a predetermined section, surface features including curved, arcuate, concave, convex, ramped, peaked, and valley-like shapes are produced.

41. The system of claim 38 wherein said processor is configured to determine the active-pixel density from the bitmap image of the geometry; the required number of pixel translations to create a mask for the required geometry; and

the frame rate for each pixel transition to achieve the energy for creating a

predetermined thickness on a specific region of the tire.

42. The system of claim 41 wherein said processor creates a movie with a varying frame rate corresponding to the shape to be created on the tire.

43. The system of claim 17 wherein said velocity profile is provided as a waveform to an actuator such that the framerate of the movie and the velocity profile of the actuator are synchronous.

44. The system of claim 38 wherein the three-dimensional shape has a smooth surface made by a single scan having a linear velocity profile.

45. The system of claim 38 wherein intensity of said light is varied during scanning.

46. A scanning vat-photopolymerization method for producing a three-dimensional shape on a tire in a single scan, comprising the steps of: varying the thickness in one or more scanned units by varying the energy applied to each scanned unit.

47. The method of claim 46 wherein the thickness is varied by changing the exposure depth of said scanned units.

48. The method of claim 46 wherein the scan is a continuous movement having a variable scanning speed, a variable intensity, or both.

49. The method of claim 46 wherein the scanned unit is a voxel.

50. The method of claim 46 wherein further including the steps of determining the active-pixel density from the bitmap image of the geometry; determining the required number of pixel translations to create a mask for the required geometry; and determining the frame rate for each pixel transition to achieve the energy for creating a predetermined thickness on a specific region of the tire.

51. The methods of claims 1, 21, 26 and 46 wherein photopolymerization is performed in an inert environment.

52. The methods of claims 1, 21, 26 and 46 wherein photopolymerization is performed in an inert environment to reduce oxygen diradicals from terminating growing polyacrylamide chains.

53. The methods of claims 1, 21, 26 and 46 further including the step of bubbling nitrogen through the photopolymer.

54. The methods of claims 1, 21, 26 and 46 further including the step of performing a nitrogen sparge to reduce the presence of oxygen during photopolymerization.

55. The method of claim 1 wherein the three-dimensional shape has graded mechanical properties through a predetermined area of the build layer.

56. The method of claim 1 wherein the three-dimensional shape has a graded thickness profile and graded mechanical properties through a predetermined area of the build layer.

57. The method of claim 13 wherein the three-dimensional shape has graded mechanical properties through a predetermined area of the build layer.

58. The method of claim 13 wherein the three-dimensional shape has a graded thickness profile and graded mechanical properties through a predetermined area of the build layer.

59. The method of claim 26 wherein the three-dimensional shape has graded mechanical properties through a predetermined area of the build layer.

60. The method of claim 26 wherein the three-dimensional shape has a graded thickness profile and graded mechanical properties through a predetermined area of the build layer.

61. The method of claim 38 wherein the three-dimensional shape has graded mechanical properties through a predetermined area of the build layer.

62. The method of claim 1 wherein the three-dimensional shape has a graded thickness profile and graded mechanical properties through a predetermined area of the build layer.

63. The system of claim 38 wherein the three-dimensional shape has a graded thickness profile through a predetermined area of the build layer.