US-20260124808-A1 - METHOD OF VOLUMETRIC ADDITIVE MAUFACTURING

Abstract

A method of volumetric additive manufacturing, comprising rotating a vial of photocurable resin; creating patterns of structured light images of an object to be manufactured so that the shape of the light dose distribution matches a desired shape of the object; correcting for diffusion within the vial; projecting the patterns of structured light images via a projector onto the rotating vial of photocurable resin thereby printing the object corrected for diffusion; and removing the printed object from the vial.

Inventors

• Antony Orth
• Daniel Webber
• Yujie Zhang
• Guy Godin
• Jonathan BOISVERT
• Chantal Paquet

Assignees

• NATIONAL RESEARCH COUNCIL OF CANADA

Dates

Publication Date

20260507

Application Date

20230822

Claims (20)

1. 1 . A method of volumetric additive manufacturing, comprising: rotating a vial of photocurable resin; creating patterns of structured light images of an object to be manufactured so that the shape of the light dose distribution matches a desired shape of the object, the interior of which is infilled with a lattice structure; projecting the patterns of structured light images via a projector onto the rotating vial of photocurable resin thereby printing the object such that only the lattice structure and exterior surface of the object are cured within the photocurable resin as the vial rotates; removing the printed object from the vial; and curing the printed object to solidify any uncured photocurable resin trapped within the lattice structure.
2. 2 . The method of claim 1 , wherein the interior is infilled by converting a 3D reference image into printing instructions for printing multiple horizontal 2D layers of the object according to parameters for infill density and infill pattern 3 . The method of claim 1 , wherein the uncured photocurable resin is flood cured using ultraviolet (UV).
3. 4 . The method of claim 1 , wherein the printed object is removed after at least one complete revolution of the vial.
4. 5 . The method of claim 1 , wherein the thickness of the lattice structure and exterior surface of the object is ˜0.16 mm.
5. 6 . The method of claim 1 , wherein the photocurable resin is a low viscosity resin.
6. 7 . The method of claim 6 , wherein the low viscosity resin has a viscosity of ˜100 cp-50 k cp.
7. 8 . A method of volumetric additive manufacturing, comprising: rotating a vial of photocurable resin; creating patterns of structured light images of an object to be manufactured at a target dose intensity so that the shape of the light dose distribution matches a desired shape of the object; correcting the patterns of structured light images to a corrected target dose intensity, thereby increasing light intensity near the surface of the object to be manufactured; projecting the corrected patterns of structured light images via a projector onto the rotating vial of photocurable resin thereby printing the object as the vial rotates, such that all features of the object cure at the same time; and removing the printed object from the vial.
8. 9 . The method of claim 8 , wherein correcting the patterns of structured light images further comprises performing an iterative deconvolution to account for diffusion of light within the vial by increasing the target dose intensity to the corrected target dose intensity near the surface of the object to be manufactured, wherein the iterative deconvolution uses a diffusion coefficient of the photocurable resin to account for light within the photocurable resin and a point-spread-function to account for pixel blurring by the projector.
9. 10 . The method of claim 9 , wherein the point-spread-function is a time independent blurring point spread function.
10. 11 . The method of claim 8 , wherein the iterative deconvolution is a modified Richardson-Lucy deconvolution.
11. 12 . The method of claim 11 , wherein the iterative deconvolution is performed as follows: where u 0 is the target dose intensity, D k is a coefficient combining the diffusion coefficient and the point-spread-function, u n is an n th iteration of the corrected target dose intensity, and N is number of iterations: set u n =u 0 and for n=1 to N; u n =u n *convolve(u 0 /convolve(u n , D k ), D k ) #Richardson-Lucy deconvolution iteration; u n =u n *u 0 /convolve(U n , D k ) #Modified Richardson-Lucy deconvolution iteration that rebalances corrected object intensity; return u n .
12. 13 . The method of claim 9 , wherein the diffusion coefficient is measured using optical scattering tomography.
13. 14 . The method of claim 9 , wherein the point-spread-function is imaged using fluorescence imaging.
14. 15 . The method of claim 8 , wherein the printed object is removed after at least one complete revolution of the vial.
15. 16 . The method of claim 8 , wherein the photocurable resin is a low viscosity resin.
16. 17 . The method of claim 16 , wherein the low viscosity resin has a viscosity of ˜100 cp-50 k cp.
17. 18 . A method of volumetric additive manufacturing, comprising: rotating a vial of photocurable resin; creating patterns of structured light images of an object to be manufactured so that the shape of the light dose distribution matches a desired shape of the object; correcting for diffusion within the vial; projecting the patterns of structured light images via a projector onto the rotating vial of photocurable resin thereby printing the object corrected for diffusion; and removing the printed object from the vial.
18. 19 . The method of claim 18 , wherein the photocurable resin is a low viscosity resin.
19. 20 . The method of claim 19 , wherein the low viscosity resin has a viscosity of ˜100 cp-50 k cp.
20. 21 . The method of claim 1 , wherein the lattice structure has the same thickness as an exterior surface of the object.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is directed to light-based additive manufacturing, and more particularly to methods of volumetric additive manufacturing that correct for the effects of diffusion. Most 3D printing techniques involve adding material layer by layer. This sets some limitations on the types of applications for which 3D printing is suitable, such as printing around a preexisting object. In light-based additive manufacturing, photocurable resin is exposed to spatially structured (i.e. 3D) light that causes the resin to cure. The 3D light dose applied to the resin dictates the shape of the object that is printed, which permits printing entire complex objects through one complete revolution, circumventing the need for layering. However, the object does not cure instantaneously, but rather it takes on the order of seconds to a minute for the curing process to complete. During this time, the light dose effectively diffuses away from the intended object region and into regions where no light dose was intended. Moreover, light dose is also deposited in regions outside the desired object boundary due to unavoidable optical blurring of the projection beam (e.g. a square pixel when projected in resin becomes blurred) . As a result, small features of dimensions comparable to the dose diffusion length and projector point spread function (PSF) require more dose to cure. In addition, diffusion of the light dose into regions outside of the intended volume can result in over-exposure so that the object grows beyond the intended boundary. This problem described above is especially prominent in volumetric additive manufacturing (VAM), including tomographic additive manufacturing (TAM), where all layers are exposed simultaneously. In this case, diffusion occurs throughout the entire print over a time scale of ˜60s, which corresponds to a diffusion length on the order of ˜0.25mm (however diffusion effects are noticeable beyond this length scale). In VAM, the major drawback of this diffusive effect is that small features do not cure under normal conditions, except when the large features are over exposed. In most cases, the small features are simply missing from the 3D print. 2. Description of the Related Art At present, the best way to mitigate the diffusion effect is to use a viscous resin where diffusion effects are less prominent, but this severely restricts the available materials for printing. This also does not address the part of the effect imposed by the optical blurring of the projection image. SUMMARY OF THE INVENTION It is an aspect of the present invention to provide methods to correct for the effect of diffusion in VAM. In one aspect, infilling is used so that projected light cures only the shell and interior scaffolding of the object, instead of the entire solid object. In another aspect, deconvolution is used to-correct the projections for diffusion. The above aspects can be attained by a method of volumetric additive manufacturing, comprising: rotating a vial of photocurable resin; creating patterns of structured light images of an object to be manufactured so that the shape of the light dose distribution matches a desired shape of the object, the interior of which is infilled with a lattice structure; projecting the patterns of structured light images via a projector onto the rotating vial of photocurable resin thereby printing the object such that only the lattice structure and exterior surface of the object are cured within the photocurable resin as the vial rotates; removing the printed object from the vial; and curing the printed object to solidify any uncured photocurable resin trapped within the lattice structure. Additional aspects can be attained by a method of volumetric additive manufacturing, comprising: rotating a vial of photocurable resin; creating patterns of structured light images of an object to be manufactured so that the shape of the light dose distribution matches a desired shape of the object; correcting for diffusion within the vial; projecting the patterns of structured light images via a projector onto the rotating vial of photocurable resin thereby printing the object corrected for diffusion; and removing the printed object from the vial. These together with other aspects and advantages which will be subsequently apparent, reside in the details of construction and operation as more fully hereinafter described and claimed, reference being had to the accompanying drawings forming a part hereof, wherein like numerals refer to like parts throughout. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 shows a typical VAM system for printing a 3D object. FIG. 2 is a graph showing measured time to cure for a series of disks of varying thickness using the VAM system of FIG. 1. FIGS. 3a, 3b and 3c present a comparison between a reference image of an object (FIG. 3a), an image of the resulting object with no correction (FIG. 3b), and an image of the r