US-12623405-B2 - Additive manufacturing apparatus with optical means for diffusing/ scattering projected UV light towards photocurable resin

US12623405B2US 12623405 B2US12623405 B2US 12623405B2US-12623405-B2

Abstract

The present invention relates to an additive manufacturing apparatus for additively manufacturing a component, including: a resin vat unit which includes: a reservoir for storing UV light photocurable resin; and a UV-transparent window at the bottom of the reservoir, the UV-transparent window includes a UV-transparent plate and a UV-transparent anti-adhesive flexible foil; a projection unit for projecting UV light through the UV-transparent window into the reservoir; a movable building platform having a surface onto which the component can be formed through layerwise curing of said resin. The UV-transparent window further includes: an optical means which is adapted to diffuse the projected UV light towards the building platform into a region (R) where the UV light photocurable resin is to be layerwise cured, the optical means is arranged in the light path of the projected UV light.

Inventors

Sebastian SAUL
CHRISTOPH BRANDES

Assignees

DENTSPLY SIRONA INC.
SIRONA DENTAL SYSTEMS GMBH

Dates

Publication Date: 20260512
Application Date: 20230124
Priority Date: 20220216

Claims (6)

1 . An additive manufacturing apparatus for additively manufacturing a component, comprising: a resin vat unit which comprises: a reservoir for storing UV light photocurable resin; and a UV-transparent window at the bottom of the reservoir, wherein said UV-transparent window includes a UV-transparent plate and a UV-transparent anti-adhesive flexible foil; a projection unit for projecting UV light through the UV-transparent window into the reservoir; a movable building platform having a surface onto which said component can be formed through layerwise curing of said resin; wherein the UV-transparent window further comprises: an optical means which is adapted to diffuse the projected UV light towards the building platform into a region where the UV light photocurable resin is to be layerwise cured, wherein the optical means is arranged in the light path of the projected UV light, wherein the UV-transparent anti-adhesive flexible foil includes light diffusing particles, and the optical means is realized through said light diffusing particles inside the UV-transparent anti-adhesive flexible foil.
2 . The additive manufacturing apparatus according to claim 1 , wherein the optical means further comprises a matrix of light diffusing microlenses.
3 . The additive manufacturing apparatus according to claim 1 , wherein the reservoir and the UV-transparent window are configured to define a detachable resin vat unit which is detachable through a user from the additive manufacturing apparatus.
4 . The additive manufacturing apparatus according to claim 3 , further comprising an RFID reader/writer, and wherein the detachable resin vat unit comprises an RFID tag that includes information on the presence/absence of the optical means in the UV-transparent window.
5 . The additive manufacturing apparatus according to claim 1 , wherein said UV-transparent anti-adhesive flexible foil is removably mounted to the resin vat unit.
6 . A UV-transparent anti-adhesive flexible foil configured for use in an additive manufacturing apparatus, the UV-transparent anti-adhesive flexible foil comprising an upper surface and a lower surface, wherein at least one of the upper surface and the lower surface of the UV-transparent anti-adhesive flexible foil includes light diffusing particles.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS This is a National Phase application of International Application No. PCT/EP2023/051633 filed on Jan. 24, 2023, which claims the benefit of and priority to European Application Ser. No. 22156974.2, filed on Feb. 16, 2022, which are herein incorporated by reference for all purposes. TECHNICAL FIELD OF THE INVENTION The present invention relates to an additive manufacturing apparatus for additively manufacturing 3D components such as dental restorations and dental appliances. BACKGROUND OF THE INVENTION In additive manufacturing techniques, such as stereolithography (SLA) or digital light processing (DLP), a 3D (three-dimensional) component is printed layer-by-layer through light-based curing of a liquid printing medium i.e., a photocurable resin, which is selectively cured under the influence of UV radiation. The photocurable resin can become finally transparent or non-transparent/colored after the curing/polymerization process depending on the type of the photocurable resin material used. In a commonly known variation of additive manufacturing, the 3D components are preferably pulled by means of a building platform, upside-down out of the photocurable resin in a resin vat. Other variations of additive manufacturing are also known to those skilled in the art. FIG. 2 illustrates a comparative example in which the right-hand side shows a vertical cross-sectional partial view of an additive manufacturing apparatus according to the prior art. The prior art additive manufacturing apparatus comprises: a resin vat unit (3) which comprises a reservoir (4′) for storing UV light photocurable resin (5′), and a UV-transparent window (6-4′) at the bottom of the reservoir (4′), wherein said UV-transparent window (6-4′) includes a UV-transparent plate (6-4a′) and a UV-transparent anti-adhesive flexible foil (6-4b); a projection unit (7′) for projecting UV light (8′) through the UV-transparent window (6-4′) into the reservoir (4′); and a movable building platform (9′) having a surface (9a′) onto which a 3D component can be produced through layerwise curing of the said resin (5″). A problem with the prior art additive manufacturing apparatus in FIG. 2 is that the printed 3D components subsequently require mechanical surface treatment such as polishing, grinding for obtaining a smooth surface. In general, dental restorations and appliances can't be used directly after 3D printing without such mechanical surface treatment being applied as it would cause an unpleasant sensation to the user. Therefore, the prior art has the disadvantages that additional staff, working hours, and consumables are required for the mechanical surface treatment of the printed 3D components, and thus all these incur respective costs. Furthermore, when the 3D component is printed from a transparent photocurable resin, this results in a translucent 3D component because of the rough surface which affects the light transmission and causes a certain degree of opacity. However, 3D components such as dental aligners need to be clear to give a natural impression. Therefore, also some mechanical surface treatment is usually required to remove the opacity. FIG. 10B illustrates a comparative example in which a 3D component (2′) has been printed using a transparent photocurable resin through an additive manufacturing apparatus according to the prior art. In this comparative example, the 3D component (2′) has not been subjected to any mechanical surface treatment. The eagle in the background illustrates that the 3D component (2′) has a certain opacity because of the rough surface. FIG. 11C illustrates another comparative example in which a dental aligner (2a′) has been printed using a transparent photocurable resin through an additive manufacturing apparatus according to the prior art. Also, in this comparative example the aligner (2a′) has not been subjected to any mechanical surface treatment and has been directly placed on a denture model (D). It can be seen that the aligner (2a′) has a certain opacity because of the rough surface, and the teeth cannot be clearly seen. In the prior art, anti-aliasing software is commonly used to improve edge-smoothness so that any mechanical surface treatment can be omitted. In principle, such anti-aliasing software is based on the use of 2D/3D digital filters which are commonly known in the art. However, the prior art has the disadvantages that anti-aliasing software increases the computational costs and is also limited by the geometry and magnification of the light source such as laser point diameter or pixel size. These physical limitations reduce the practical effects that can be achieved with it. SUMMARY OF THE INVENTION The inventors are not aware of any additive manufacturing apparatus technology in which an optical means for diffusing/scattering the projected UV light towards the UV light photocurable resin (5), for example, a milky foil and/or a milky plate is used to manufacture