3D PRINTING APPARATUS OF THE BOTTOM-UP PHOTO-CURING TYPE WITH VARIABLE REFRACTION INDEX ROTARY GLASS AND RELATIVE METHOD OF USE

Abstract

A 3D printing apparatus of the bottom-up photo-curing type, including a tank containing a liquid photo-curing material and at least one source of a radiation designed to obtain the photo-curing of the liquid photo-curing material, the bottom of the tank including an elastic membrane of non-stick material and transparent to the radiation of the light source, the tank supported on a support plate, the support plate includes, in the portion below the bottom of the tank, a mobile support element, which is able to move by translating and/or rotating in the plane where it is positioned with one or more perforated or lowered portions. The embodiments also relate to a method of using the apparatus for 3D printing.

Claims

1-7. (canceled)

8. A 3D printing apparatus of the bottom-up photo-curing type, comprising: at least one source of a radiation capable of obtaining the photo-curing of a photo-curing liquid material, above which a tank is arranged containing the photo-curing liquid material and inside which at least one extraction plate is immersed, which is provided with moving means with alternating rectilinear motion, along a direction perpendicular to the bottom of the tank from a position at a distance from the bottom of the tank equal to the thickness of a layer obtainable by photo-curing of the photo-curing liquid material, the bottom of the tank constituted by an elastic membrane of an anti-adherent material which is transparent to the radiation of the light source, the tank placed on a support plate, wherein the support plate comprises, in the portion below the bottom of the tank, a mobile support element, configured to move by translating and/or rotating in the plane in which it is positioned, which, alternately is made entirely of the same material transparent to the radiation utilized for the photo-curing, with one or more perforated or lowered portions with respect to its upper surface, of a size equal to the printing area size, and between the at least one source of a radiation suitable for obtaining photo-curing of the liquid photo-curing material and the mobile support element a system of lenses with different refractive index is interposed, or alternates, at regular intervals, a portion of a material transparent to the radiation used for the photo-curing, of a size equal to the size of the print area, and a perforated portion or lowered with respect to its upper surface, of a size equal to the size of the printing area, the support element able to comprise more than one portion of the material transparent to the radiation used for photo-curing and the same number of perforated or lowered portions, and each portion of material transparent to the radiation used for photo-curing has a different refractive index, the difference between the refractive indexes being equal to the shift of the incident ray equal to the pixel size divided by the number of portions of radiation transparent material.

9. The 3D printing apparatus according to claim 8, wherein the material transparent to the radiation used for photo-curing is borosilicate glass or quartz.

10. The 3D printing apparatus according to claim 8, wherein the mobile support element is a support disk, having the possibility of rotating around its centre.

11. The 3D printing apparatus according to claim 8, wherein, when the mobile support element alternates more than one portion of material transparent to the radiation used for photo-curing and the same number of perforated or lowered portions, each portion of material transparent to the radiation used for photo-curing is formed by an opening, covered by a plate of a material transparent to the radiation used for photo-curing.

12. The 3D printing apparatus according to claim 8, wherein, when between the at least one source of a radiation suitable for obtaining photo-curing of the liquid photo-curing material and the mobile support element a system of lenses with different refractive index is interposed, the system of lenses is provided with means of movement of rotary or linear type of the lenses with different index of refraction.

13. The 3D printing apparatus according to claim 8, wherein the apparatus comprises a plurality of extraction plates and an equal number of sources of a radiation capable of obtaining photo-curing of the liquid photo-curing material.

14. A 3D printing method of the bottom-up photo-curing type, implemented by the apparatus of the claim 8, comprising the following steps: a) moving the support element to arrange below the extraction plate a portion of the support element which is transparent to the radiation used for photo-curing; b) lowering the extraction plate to a position where the last cured layer, or in its absence the lower surface of the extraction plate, is at a distance of one layer to be formed with respect to the bottom of the tank; c) proceeding with the irradiation and the generation of one cured layer of the object to be printed; d) moving the support member to arrange below the extraction plate a portion of the perforated or lowered support; the bottom of the tank remaining attached to the cured layer; e) lifting the extraction plate, with a progressive detachment of the bottom of the tank from the hardened layer; f) moving the support element to arrange below the extraction plate the same or a different portion of the support transparent to the radiation used for photo-curing; and iteratively repeating steps b)-f) until the completion of the object to be formed.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0073] The invention is now described, by way of example and without limiting the scope of the invention, according to a preferred embodiment, with reference to the accompanying drawings, in which:

[0074] FIG. 1 shows a perspective view from above of a 3D printing apparatus of the bottom-up photo-curing type, with rotary glass with variable refractive index according to a first embodiment of the invention, with the tank raised with respect to the rest of the structure;

[0075] FIG. 2 shows a perspective view from above of the apparatus of FIG. 1, with the tank resting on the supporting plate;

[0076] FIG. 3 shows a perspective view from below of the apparatus of FIG. 1,

[0077] FIG. 4 shows an exploded view of the support disc of the apparatus of FIG. 1, and

[0078] FIG. 5 shows a perspective view from above of a 3D printing apparatus of the bottom-up photo-curing type, with rotary glass with variable refractive index according to a second embodiment of the invention.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0079] Referring preliminarily to FIGS. 1-4, the characterising elements of an apparatus for 3D printing of the bottom-up photo-curing type, with rotary glass having a variable refractive index according to the invention essentially comprise a tank 10 (which can be considered as a consumable element), with a bottom 11, transparent to the radiation of a light source 12 (or, more generally, of a source of a radiation designed to obtain the photo-curing of the photo-curing material), arranged under said tank 10. The tank 10 is arranged above a support plate 13, which has a support disc 14 in the part below the bottom 11 of the tank 10.

[0080] In particular, the bottom 11 of the tank 10 consists of an elastic membrane of non-stick material.

[0081] The support disc 14 is mounted on a motor 15 which allows the rotation of the support disc 14 around its centre 16 and alternates, at regular angular intervals around said centre 16, three openings 17 covered by as many glass sheet, respectively a first glass sheet 18′, a second glass sheet 18″ and a third glass sheet 18′″, said openings 17 having dimensions equal to the size of the printing area, and three perforated portions 19 (or three portions lowered with respect to the upper surface of the support disc 14), again having dimensions equal to the size of the printing area.

[0082] In particular, the glass of said glass sheets 18′, 18″, 18″ is a glass transparent to the radiation of said light source 12 used for the photo-curing and preferably is borosilicate glass or quartz.

[0083] Finally, the apparatus comprises an extraction plate 20 with a respective handling and support system 21, the extraction plate 20 being suitable for housing on its lower surface the first layer of the object to be printed, and for progressively extracting said object from the tank 10, with the alternative lifting and partial lowering movement typical of 3D printing systems of the bottom-up photo-curing type.

[0084] In the printing step, the support disc 14 is initially rotated in such a way that a first opening 17 is arranged under the extraction plate 20 with the respective first glass sheet 18′, which is thus interposed between the elastic membrane of non-stick material forming the bottom 11 of the tank 10 and the light source 12 used for the photo-curing. Once in position, the irradiation and generation of the first layer of the object to be printed is performed. Having formed the first layer, the support disc 14 is rotated to a second position, in which a perforated portion 19 is arranged under the extraction plate 20 and the extraction movement of the extraction plate 20 is then carried out, in a condition wherein the elastic membrane of non-stick material forming the bottom 11 of the tank 10 behaves like a free-field membrane. At this point, the support disc 14 is rotated again, until a second opening 17 with the respective second glass sheet 18″ is located under the extraction plate 20 for the formation of a second layer of the object to be printed. The process continues as described above, alternating, in the position below the extraction plate 20, an opening 17 covered by the respective sheet of glass and a perforated portion 19, until the printing of the object is completed.

[0085] It is clear that by using this method, the suction cup effect is not only contained, but definitively eliminated, like a suction cup attached to a glass, which instead of being deformed on one side to allow air to enter (peeling phenomenon), is actually moved to the edge of the glass. On this occasion, the perpendicular component, which opposes the detachment of the object from the elastic membrane, generating the suction cup effect, is effectively cancelled out.

[0086] In addition, the configuration of the 3D printing apparatus according to the invention is also particularly effective for a further technical effect. In fact, by rotating the support disc 14 and keeping the bottom 11 of the tank 10, made of flexible non-stick material, stationary, no type of mechanical stress is generated on the lower surface of the last formed layer of the object being made, since during the rotation step of the support disc 14 the newly cured layer and the membrane of non-stick material forming the bottom 11 of the tank 10 remain stationary. If, on the other hand, instead of the support disc 14, the tank 10 is rotated, and with it the bottom 11 consisting of the flexible membrane of non-stick material, a mechanical stress is generated on the lower surface of the last formed layer due to sliding with respect to the membrane.

[0087] The 3D printing apparatus of the bottom-up photo-curing type according to the invention and a method of use thereof are thus configured as a new 3D printing technology, which allows the formation of objects without the generation of the suction cup effect, without the introduction of mechanical stress and in the absence of restrictions regarding the non-stick material to be used.

[0088] In addition, the 3D printing apparatus according to the invention can be conveniently adapted to intervene directly on the aliasing problem. In this respect, according to the invention it is proposed to vary the refractive index of the glass sheets used in the active part, by alternating the glass sheets 18′, 18″, 18′″ having different refractive indexes, by a value equal to the shift of the incident ray equal to the pixel size divided by the number of glass sheets 18′, 18″, 18′″ (resolution/N). In this way, for each printed layer, instead of introducing compression errors, with inevitable loss of resolution and geometric accuracy, while always maintaining the highest quality of each individual image, a surface is obtained with a roughness equal to 1/N and geometric accuracy always equal to the pixel.

[0089] Moreover, referring to FIG. 5, a second embodiment of the 3D printing apparatus of the bottom-up photo-curing type with rotary glass with variable refractive index according to the invention is shown, wherein, taking advantage of the fact that several printing areas are simultaneously present, as many extraction plates are correspondingly arranged to print several objects simultaneously.

[0090] In particular, FIG. 5 shows a 3D printing apparatus of the bottom-up photo-curing type, with rotary glass with variable refractive index according to an embodiment of the invention wherein there are three extraction plates 20, each with a respective handling and support system 21, to take full advantage of the presence on the support disc 14 of three openings 17, covered by respective glass sheets 18′, 18″, 18″.

[0091] The technology according to the invention can be implemented according to different embodiments, not shown in the drawing but all falling within the same inventive concept.

[0092] In particular, according to a further embodiment, the rotating support disc is replaced by a support plate, which is able to translate along a horizontal axis, consequently positioning under the extraction plate alternatively an opening covered by a glass sheet and a perforated or lowered portion.

[0093] Moreover, according to a further embodiment, a lens system with a different refractive index is interposed between the light source and the glass sheet on which the layers of the object being printed are formed, the lens system being equipped with rotary or linear means of handling lenses with different refractive indexes.

[0094] The 3D printing apparatus of the bottom-up photo-curing type with variable refraction index rotary glass according to the invention achieves a number of advantages over prior art solutions.

[0095] Firstly, thanks to the 3D printing apparatus of the bottom-up photo-curing type with variable refraction index rotary glass according to the invention it is possible to achieve a total cancellation of the suction cup effect. In fact, by keeping the tank fixed with respect to the object being printed and moving the support system positioned underneath the bottom of the tank to alternate between areas of the support system that are transparent to the radiation used for photo-curing and areas that are perforated or lowered, the mechanical stress on the newly cured layer is completely eliminated.

[0096] Having eliminated the suction cup effect between the support system and the bottom of the tank made of non-stick material, the only effect that remains effective is the adhesion between the non-stick material and the last cured layer, which can be varied according to the type of non-stick material used, so as to obtain different behaviour during the detachment step.

[0097] Moreover, thanks to the 3D printing apparatus of the bottom-up photo-curing type with variable refraction index rotary glass according to the invention it is possible to achieve a substantial reduction in the aliasing effect. In fact, working with glass supports with different refractive indices, it is possible to introduce a shift of the incident light beam within the pixel size, which allows the geometric accuracy to be maintained within the pixel, with a simultaneous reduction in roughness, equal to a fraction of the number of indices introduced.

[0098] Finally, again as a result of using the technology underlying the 3D printing apparatus of the bottom-up photo-curing type, with variable refractive index rotary glass according to the invention, it is possible to simultaneously print a plurality of objects in the same tank, each object at a different printing area, at which a corresponding extraction plate is arranged, simply by adding a corresponding number of light sources.

[0099] The invention is described by way of example only, without limiting the scope of application, according to its preferred embodiments, but it shall be understood that the invention may be modified and/or adapted by experts in the field without thereby departing from the scope of the inventive concept, as defined in the claims herein.