3D PRINTING PROCESS

Description

[0001] The invention relates to a volumetric 3D printing method for producing a three-dimensional object starting from a three-dimensional template object which is formed from a virtual object material, the method comprising the following steps: a) Providing at least one memory, wherein projection images of the template object are stored in the at least one memory, wherein the projection images are two-dimensional light distributions of pixels, for example in rows and columns, which projection images correspond to projections of the template object in respective different projection directions around a specified object axis, wherein the projection directions of the projection images are orthogonal to the specified object axis, wherein the brightness of a pixel of a projection image corresponds to the summed virtual object material of the template object, starting from the pixel, along the projection direction of the corresponding projection image in such a way that the brightness of a pixel is proportional to its summed virtual object material, of at least one projection device which is configured tob) projecting the projection images of the template object in the direction of a radiation direction of the at least one projection device in front of the at least one projection device in a defined depth of field around a focal plane, and of a container containing a photosensitive substance, wherein the photosensitive substance is configured to harden in areas in which a light intensity threshold is exceeded, b) projecting the projection images by means of the at least one projection device into the photosensitive substance located in the container, so that the light intensity threshold of the light-sensitive substance is exceeded in the areas corresponding to the three-dimensional object to be produced, wherein the individual projection images are each projected into the photosensitive substance in different angular positions around a defined container axis,wherein the radiation direction of the projection device in an angular position corresponds to the projection direction of the projection image of the template object depicted in the angular position, c) removing the cured three-dimensional object to be produced from the container.

[0002] Such a method is known from WO2020 / 232083 A1. In prior art volumetric 3D printing processes, the size or

[0003] The size of the three-dimensional object to be produced is limited by the depth of field of the projection devices, since the light intensity with which the projection images are displayed must be sufficiently high, which can only be achieved with a rather large aperture - and the resulting narrow depth of field.

[0004] In the prior art, the aperture of at least one projection device is therefore usually fixed and is due to an interaction between the light intensity of the light source of the projection device and the desired depth of field.

[0005] Due to the fixed aperture, the depth of field is also fixed and naturally limited.

[0006] The depth of field depends quadratically on the size of the pixels, with orders of magnitude of 100 mm for 100 µm pixel size, 1 mm for 10 µm pixel size and 10 µm for 1 µm pixel size being typical, i.e. the more precise you want to print (i.e. you want to have smaller pixels), the more the limiting depth of field has an impact and prevents the production of a larger object.

[0007] This means that with conventional state-of-the-art methods, the object to be produced can necessarily have a maximum size or extent of usually a few 10 mm, depending on the implementation up to a single or double depth of field.

[0008] It is therefore an object of the present invention to provide a method which eliminates the disadvantages of the prior art and enables the production of larger objects.

[0009] This object is achieved in that in step b) if in an angular position the extent of the three-dimensional object to be produced along the radiation direction of the at least one projection device in this angular position is at least twice as large as the defined depth of field, the focal plane is displaced relative to the container in such a way that at least half of the extent of the three-dimensional object to be produced along the respective radiation direction in the respective angular position is covered by the depth of field.

[0010] It should be noted that when displaying the projection images, the light intensity is also proportional to the accumulated virtual object material, so that those locations which have a larger sum of virtual object material compared to others have a higher light intensity when displayed.

[0011] The projection images can preferably be obtained by a Radon transformation.

[0012] It should be noted that if not enough energy in the form of light intensity has entered the light-sensitive substance to sufficiently cure the three-dimensional object to be produced, then step b) can optionally be repeated until the object to be produced has cured in the light-sensitive substance.

[0013] The light-sensitive substance can be a light-sensitive resin, for example made of a photopolymer and a photoinitiator. The photopolymer can be, for example, gelatin methacrylate (gelMA), dissolved in phosphate-buffered saline (PBS); bisphenol A glycerol diacrylate (BPAGDA); poly(ethylene glycol) diacrylate (PEGDA) or pentaerythritol tetraacrylate (PETA). The photoinitiator can be, for example, lithium phenyl 2,4,6-trimethylbenzoylphosphinate (LAP); camphorquinone (CQ), with co-initiator ethyl 4-dimethylaminobenzoate (EDAB); tris(2,2-bipyridyl)dichlororuthenium(II) hexahydrate (Ru) and sodium persulfate (SPS); 3,4-epoxycyclohexylmethyl 3,4-epoxycyclohexanecarboxylate (EEC); Phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide or bis(η5-2,4-cyclopentadien-1-yl)-bis(2,6-difluoro-3-(1H-pyrrol-1-yl)-phenyl)titanium (brand name: Irgacure 784, BASF) can be used.

[0014] It can be provided that exactly one projection device is provided in step a).

[0015] It can be provided that in order to display the projection images by the at least one projection device in the respective angular positions, the container is rotated about the container axis.

[0016] It can be provided that in order to display the projection images by the at least one projection device in the respective angular positions, the at least one projection device is rotated about the container axis.

[0017] It can be provided that the displacement of the focal plane in the respective angular positions takes place by moving the container relative to the at least one projection device, in particular by moving it linearly along the radiation direction of the at least one projection device.

[0018] It can be provided that the displacement of the focal plane in the respective angular positions takes place by moving the at least one projection device relative to the container, in particular by moving it linearly along the radiation direction of the at least one projection device.

[0019] It can be provided that the displacement of the focal plane in the respective angular positions takes place by adjusting a focus or a focal length of the at least one projection device.

[0020] It can be provided that the displacement of the focal plane is carried out by a spiral movement of the container and / or the projection device.

[0021] It can be provided that the different angular positions in which the projection images are displayed are spaced from each other by 0.5° to 5°.

[0022] It can be provided that the projection directions of the projection images run around the defined object axis at defined equal distances from one another, preferably at distances of 0.5° to 5°, in particular 0.5°.

[0023] It can be provided that in step b) the imaging of the projection images in the different projection directions into the container takes place continuously or step by step. Character description

[0024] The invention is explained in more detail below with reference to exemplary drawings. Fig. 1 a perspective view of an example of a three-dimensional template object which is formed from a virtual object material, wherein starting from this template object a three-dimensional object is to be produced by means of a volumetric 3D printing process, Fig. 2A the template object from Fig. 1in a view from above, wherein two-dimensional projection images are depicted around an object axis in different projection directions, and represent projection images of the template object in the respective projection direction, Fig. 2B an exemplary projection image with exemplary pixels, wherein starting from the respective pixels in the direction of the projection direction of the projection image, the virtual object material of the template object is summed up, Fig. 3A-3H schematic representations of a sequence of a volumetric 3D printing process, wherein the individual projection images of the template object are Fig. 2in different angular positions by means of a projection device into a container, wherein the angular positions correspond to the corresponding projection direction of the projection images, and wherein in the example shown the container is rotated relative to the projection device, Fig. 4A-4C a schematic representation of a sequence of a relative linear displacement of the projection device to the container, wherein by the displacement a focal plane and its depth of field of the projection device in the container is moved linearly, wherein the linear displacement in the example shown during the imaging of the projection image in Fig. 3A expires.

[0025] The figures show a schematic sequence of a volumetric 3D printing process for producing a three-dimensional object 50 starting from a three-dimensional template object 100, which is formed from a virtual object material and in Fig. 1 shown in a perspective view.

[0026] The method comprises in a first step a) the provision of at least one memory, wherein projection images 200 of the template object 100 are stored.

[0027] The projection images 200 are two-dimensional light distributions of pixels in rows and columns, which project images 200 Projections of the template object 100 in different projection directions PR1 - PR8 around a specified object axis OA correspond, whereby the projection directions PR1 - PR8 the projection images 200 orthogonal to the specified object axis OA get lost.

[0028] Fig. 2A shows the template object 100 in a top view, with the specified object axis OAat equal angular intervals of 45° around projection images 200 The angular distance between the projection directions PR1 - PR8 is 45° in the example shown for the sake of simplicity and can preferably also be 0.5° to 5°, in particular 0.5°.

[0029] It should be noted that the projection images shown 200 in Fig. 2A are actually perpendicular to the plane of the drawing. However, for better clarity and comprehensibility, the present representation was chosen.

[0030] The brightness of a pixel of a projection image 200 corresponds to the summed virtual object material of the template object 100, starting from the pixel, along the projection direction PR1 - PR8 of the corresponding projection image 200 such that the brightness of a pixel is proportional to its summed virtual object material.

[0031] Fig. 2B shows an example projection image 200, where two pixels 211, 212 The corresponding projection image and projection direction are also shown in Fig. 2A Based on the respective pixels 211, 212 in the direction of projection PR1 of the projection image, the virtual object material is summed up, as already described. In the example shown in Fig. 2B is the sum of the virtual object material starting from the pixel with reference symbol 211 greater than the sum starting from the pixel with reference symbol 212. The pixel with reference symbol 211 is therefore shown darker in the projection image in the examples shown than the pixel with reference symbol 212.It should be noted that the representation can also be reversed, ie those pixels with a higher sum of the summed virtual object material are brighter than those whose sum is comparatively smaller.

[0032] As the preferred method for creating the individual projection images 200 the so-called Radon transformation can also be used.

[0033] Furthermore, in the example shown, a projection device 300 which is set up to display the projection images 200 of the template object 100 in the direction of a radiation direction X the at least one projection device 300 in front of at least one projection device 300 in a defined depth of field ST around a focal plane F sharply. When displaying the projection images 200The light intensity is also proportional to the accumulated virtual object material, so that those spots or pixels that have a larger sum of virtual object material compared to others have a higher light intensity when imaging. With regard to the example shown in Fig. 2B knows that pixel with the reference symbol 211 a higher light intensity than the pixel with the reference symbol 212.

[0034] Furthermore, a container 400 which contains a photosensitive substance 410 contains, whereby the photosensitive substance 410 is designed to cure in areas where a light intensity threshold is exceeded. This light intensity threshold is reached or exceeded due to the irradiation of light over a certain period of time - depending on the choice of photosensitive substance.

[0035] Fig. 3A to 3Hshow a step b) of the volumetric 3D printing process, where the Figures 3A to 3H as a sequence starting with Fig. 3A can be seen. In step b) the projection images 200 using the projection device 300 into the container 400 photosensitive substance 410 imaged so that the light intensity threshold of the light-sensitive substance is exceeded in the areas corresponding to the three-dimensional object to be produced 50 are equivalent to.

[0036] The individual projection images 200 are each in different angular positions WP1 - WP8 around a fixed container axis BA into the photosensitive substance 410 be imaged, whereby the radiation direction X the at least one projection device 300 in an angular position WP1 - WP8 the projection direction PR1- PR8 of the angle position WP1 - WP8 projection image shown 200 of the template object 100 corresponds.

[0037] Fig. 3A to 3H as well as Fig. 4A to 4C show a simplified schematic sequence of the volumetric 3D printing method according to the invention for producing an object 50 starting from the virtual template object 100 using an example.

[0038] In the Figures 3A to 3H is the container 400, in which the light-sensitive substance, for example a resin, is arranged, wherein the container 400 around a container axis BA Furthermore, in each of the figures a projection device 300 shown, which is directed in the direction of a radiation direction X the different projection images from the previous Fig. 2A depicts. In Fig. 3A that projection image 200which corresponds to the projection direction PR1 corresponds, whereby the container 400 with the light-sensitive substance contained therein in a first angular position WP1 relative to the projection device 300 is located.

[0039] In a next step - visible in Fig. 3B - is the container 400 together with the resin around the container axis BA relative to the projection device 300 by an angle W rotated and is in a second angular position WP2 relative to the projection device 300.

[0040] In this position of the container 400 forms the projection device 300 the projection image 200 into the light-sensitive substance, which is in line with the projection direction PR2 corresponds.

[0041] It should be noted that in the Figures 3A to 3Hthe three-dimensional object to be produced 50 is shown, whereby this only serves as an indication of how the respective projection image 200 to the three-dimensional object to be produced 50 refers to.

[0042] This should also clarify that the radiation direction of the projection device 300 in a certain angular position WP1 - WP8 the respective projection direction PR1 - PR8 of the projection image shown in the angular position 200 of the template object 100 corresponds.

[0043] It should also be noted that to display the projection images 200 through the projection device 300 in the respective angular positions WP1 - WP8 also the projection device 300 relative to the container 400 around the container axis BA can be rotated.

[0044] Furthermore, in step b) if in an angular position WP1 - WP8 the dimension of the three-dimensional object to be produced 50 along the radiation direction X the projection device 300 in this angular position WP1 - WP8 is at least twice as large as the specified depth of field ST, the focal plane F relative to the container 400 shifted so that at least half of the dimension of the three-dimensional object to be produced 50 along the respective radiation direction X in the respective angular position WP1 - WP8 through the depth of field ST is covered.

[0045] Half of the expansion in one angular position is sufficient because when the angular position is rotated by 180° the "other" half can be made to harden.

[0046] An example is Fig. 4A to 4Cstarting from the first angular position WP1 in Fig. 3A shown that the extent of the three-dimensional object to be produced 50 along the radiation direction X the projection device 300 is larger than the depth of field ST the focal plane F. In the sequence starting from Fig. 4A up to Fig. 4C the depth of field ST by means of a linear relative displacement of the projection device 300 along the radiation direction X to the container 400 shifted so that the depth of field ST the dimension of the three-dimensional object to be produced 50 in this first angular position WP1 completely covers while the corresponding projection image 200, which corresponds to the projection direction PR1 corresponds to the light-sensitive substance 410 is depicted.

[0047] It should be noted that shifting the focal plane F in the respective angular positions WP1 - WP8 also by moving the container 400 relative to the projection device 300 can be done, in particular is moved linearly along the radiation direction X the projection device 300.

[0048] It is also conceivable that shifting the focal plane F in the respective angular positions WP1 - WP8 by adjusting the focus or focal length of the projection device 300 can be done.

[0049] The same process of shifting the depth of field ST is used in the other angular positions WP2 - WP3, which in Fig. 3B to 3H shown, were also carried out.

[0050] After displaying the projection image 200 in Fig. 3H and the associated shifting of the depth of field ST- i.e. a complete pass - the three-dimensional object should 50 If this is not the case, the passage, which is in Fig. 3A to 3H (including the respective shifting of the depth of field ST) shown, can be repeated as often as desired.

[0051] As soon as the three-dimensional object 50 has hardened, it can be removed from the container in a final step c) 400 be taken. LIST OF REFERENCE SYMBOLS

[0052] Three-dimensional object 50 Template object 100 Projection images 200 pixel 211, 212 Projection device 300 container 400 Light-sensitive substance 410 Object axis OA Container axis BA Focal plane F Depth of field ST angle W Angular position WP1-WP8 Projection direction PR1-PR8 Beam direction X

Claims

1. Volumetric 3D printing method for producing a three-dimensional object (50) based on a three-dimensional template object (100) that is formed from a virtual object material, the process comprising the following steps: a) providing at least one memory, wherein at least one projection image (200) of the template object (100) is stored in the at least one memory, wherein the projection images (200) are two-dimensional light distributions consisting of pixels, for example in rows and columns, said projection images (200) being projections of the template object (100) in different projection directions (PR1 - PR8) around a fixed object axis (OA), wherein the projection directions (PR1 - PR8) of the projection images (200) extend orthogonally to the fixed object axis (OA), wherein the brightness of a pixel of a projection image (200) corresponds to the summed virtual object material of the template object (100) starting from the pixel, along the projection direction (PR1-PR8) of the corresponding projection image (200) in such a way that the brightness of a pixel is proportional to its summed virtual object material, at least one projection device (300) that is set up to project the projection images (200) of the template object (100) in the direction of a radiation direction (X) of the at least one projection device (300) in front of the at least one projection device (300) in a defined depth of field range (ST) around a focal plane (F) and - a container (400) which contains a photosensitive substance (410), wherein the photosensitive substance (410) is arranged to harden in areas in which a light intensity threshold value is exceeded, b) imaging the projection images (200) by means of the at least one projection device (300) into the photosensitive substance (410) located in the container (400), so that the light intensity threshold of the photosensitive substance is exceeded in the areas corresponding to the three-dimensional object to be produced, wherein the individual projection images (200) ) are each imaged in the photosensitive substance (410) in different angular positions (WP1 - WP8) about a fixed container axis (BA), wherein the radiation direction (X) of the at least one projection device (300) in an angular position (WP1 - WP8) corresponds to the projection direction (PR1 - PR8) of the projection image (200) of the template object (100) imaged in the angular position (WP1 - WP8) projection image (200) of the template object (100) imaged in the angular position (WP1 - WP8), c) removal of the cured three-dimensional object (50) to be produced from the container (400), characterised in that in step b), if, in an angular position (WP1 - WP8), the extent of the three-dimensional object (50) to be produced along the direction of radiation (X) of the at least one projection device (300) in this angular position (WP1 - WP8) is at least twice as great as the defined depth of field range (ST), the focal plane (F) is displaced relative to the container (400) so that at least half of the extent of the three-dimensional object (50) to be produced along the respective radiation direction (X) in the respective angular position (WP1 - WP8) is covered by the depth of field range (ST).

2. Method according to claim 1, characterised in that the photosensitive substance (410) is a light-sensitive resin, for example of a photopolymer and a photoinitiator.

3. Method according to claim 1 or 2, characterised in that exactly one projection device (300) is provided in step a).

4. Method according to one of claims 1 to 3, characterised in that the container (400) is rotated about the container axis (BA) in order to image the projection images (200) by means of the at least one projection device (300) in the respective angular positions (WP1 - WP8).

5. Method according to one of claims 1 to 4, characterised in that, to form the projection images (200) by means of the at least one projection device (300) in the respective angular positions (WP1 - WP8), the at least one projection device (300) is rotated about the container axis (BA).

6. Method according to one of claims 1 to 5, characterised in that the displacement of the focal plane (F) in the respective angular positions (WP1 - WP8) is effected by moving the container (400) relative to the at least one projection device (300), in particular by moving it linearly along the radiation direction (X) of the at least one projection device (300).

7. Method according to one of claims 1 to 6, characterised in that the displacement of the focal plane (F) in the respective angular positions (WP1 - WP8) is effected by moving the at least one projection device (300) relative to the container (400), in particular by moving it linearly along the radiation direction (X) of the at least one projection device (300).

8. Method according to one of the claims 1 to 7, characterised in that the displacement of the focal plane (F) in the respective angular positions (WP1 - WP8) is effected by adjusting a focus or a focal length of the at least one projection device (300).

9. Method according to one of the claims 1 to 8, characterised in that the different angular positions (WP1 - WP8) in which the projection images (200) are formed are spaced apart from one another by 0.5° to 5°.

10. Method according to one of the claims 1 to 9, characterised in that the projection directions (PR1 - PR8) of the projection images (200) extend around the fixed object axis (OA) at defined equal distances from one another, preferably at distances of 0.5° to 5°, in particular 0.5°.

11. Method according to one of the claims 1 to 10, characterised in that in step b) the imaging of the projection images (200) in the different projection directions (PR1 - PR8) into the container (400) proceeds continuously or stepwise.