Software Technology for Hybrid 3-D printing using photo-curable material

Invented by Mehdi Mojdeh, Michael Christopher Cole, Peter DORFINGER, Shiva P. Sambu, Align Technology Inc

The Align Technology Inc invention works as follows

Background for Hybrid 3-D printing using photo-curable material

There are many different types of 3D printers which fabricate 3D items through an additive method. Different 3D printers are capable of performing different 3D printing methods, which can depend on the application. “Each type of 3D-printing technique has advantages and disadvantages when compared with others.

Stereolithography, also called optical fabrication solid image or stereolithography is a 3D-printing technique. SLA is the process of printing successively thin layers of photo-curable materials (e.g. polymeric resins) over one another. In right-side-up SLA (also called top-down SLA), a platform is placed in a bath containing a liquid photopolymer, such as resin, just beneath the surface of the bath. A light source, such as an ultraviolet laser, traces a pattern on the platform. The light source cures the photopolymer in the area where it is directed. This forms a layer. As the platform is lowered, the light source creates a new pattern on the platform. This will form a layer of an object with each successive increment. The process is repeated until the object has been fabricated. In inverted SLA, a section of a platform is placed within a shallow liquid bath of photopolymer resin or just below the surface of the bath. A light source, such as an ultraviolet laser, traces a pattern from the bottom of the platform through a transparent, non-stick bottom. The light source cures the photopolymer in the area where it is directed. As the platform is raised, the light source creates a new pattern on the platform. This will form another layer at each increment. The process is repeated until the object has been fabricated.

Digital light processing (DLP) is another 3D printing technology. DLP works in a similar way to SLA. The only difference is that the light source with DLP is a DLP Projector.

SLA and DLP are capable of producing objects with fine detail. SLA and DLP use photo-curable material that has a viscosity up to a specific limit. Photo-curables with viscosities higher than those allowed by SLA and DLP can’t be used on SLA or DLP printers. If the viscosity of the material is high, the uncured material may not be able to fill the space over the platform or it will fill too slowly for commercial viability. “For example, resins with low viscosity are used in SLA and DLP.

In addition, right-side up SLA, DLP, and inverted SLA, DLP, systems all require support structures, depending on the design of each part. These supports are used in right-side-up systems to hold the parts precisely at their desired location, allowing all details to be attached to them and to resist lateral force from the blade. Inverted stereolithography relies on supports to hold overhanging pieces to the build platform. They also prevent deflection caused by gravity and retain newly-created sections during the peeling process. The support structures must be removed after the object has been completed with SLA or DLP. Supports are needed for all orientations to begin printing and support overhanging features. It can be difficult to remove all support structures created during SLA or DLP for some objects. In some cases, this can make the object unusable.

Fused deposition modeling is another 3D printing technology. FDM printers use thermoplastic filament to melt and then lay it down on a printbed in layers. FDM is an inexpensive 3D printing method. FDM is low-accuracy and produces objects with little detail.

FDM can be fast but it is not always accurate and cannot produce fine detail (e.g. low clarity and feature-resolution). The thermoplastics used in FDM 3D Printing may also have mechanical properties which make them unsuitable to certain objects, such as orthodontic aligners and dental appliances. FDM has not yet been able to manufacture dental appliances such as orthodontic aligners that are clinically useful and have the necessary mechanical properties.

The embodiments described herein relate to three-dimensional (3D), printing methods, devices for forming objects by using 3D printing methods, and systems that incorporate the same. The techniques described here can be used to create a variety of objects. The implementations herein describe one or more hybrid 3D-printing techniques that can be used to 3D print a 3D object. In some implementations, a first material is used to create the walls of the vat. Then, one or two second materials are dispensed within the walls that the first material has created. A ?photo-curable material,? As used herein, a material can be defined as a material which changes its properties upon exposure to radiation such as light. These changes can be structural, such as hardening the material when exposed to light. A?vat? As used herein, a?vat’ can refer to a structure consisting of printed walls that define an reservoir configured to hold the one or two second materials.

The one- or two-second materials can be placed by extrusion, or through other dispensers. In a controlled spatial manner, the second materials can be selectively cured. Curing can involve the application of light or other curing radiation and/or a reactive mixture of resin with other materials. The spatial control of curing can be achieved by limiting the application of curing in order to create patterns, designs, or shapes. The second material or materials can be cured in portions only. Spatial control can be achieved by using patterns, designs, or shapes. The digital file is used to define the properties of the layers of an object that will be 3D-printed. “The operations of placing the first material, placing the one or two second materials and selective curing can be repeated in a controlled spatial manner until the object has been formed.

The hybrid 3D printing technologies described herein can provide similar accuracy or resolution (e.g. minimum line width) to SLA and DLP. The hybrid 3D print techniques described in embodiments can also provide printing speeds that are comparable to FDM. The hybrid 3D print techniques described herein are not limited to SLA, DLP, or FDM. They can be used for viscous photocurable materials that cannot be used in existing SLA and DLP system. These materials may be used to create various objects such as dental appliances (e.g. a directly manufactured (e.g. 3D printed), dental appliance, (e.g. removable aligners used to implement a plan of treatment, dental attachment templates, retainers and incremental and/or hybrid expanders The mold is used to create a dental appliance.

In some embodiments the techniques described herein can also be used to create molds such as thermoforming moulds. U.S. Pat. No. No. U.S. Pat. No. No. 9,943,386, inventors Webber and others, entitled “Mold with weak areas” U.S. Pat. No. No. 8,776,391 awarded to Kaza and co-inventors, titled “System for postprocessing orthodontic appliance moulds” As well as any divisional or continuation application that claims priority, and any utility or preliminary application to which they claim priority. The patents/applications cited above are hereby incorporated as if fully set forth herein.

In some embodiments, these techniques can be used to create appliances that have mandibular positioning features. U.S. Pat. No. No. 9,844,424 was filed by Wu et. al. and entitled?Dental Appliance with Repositioning Jaw Elements;? U.S. Pat. Pub. No. No. U.S. Pat. No. No. 10,213,277, by Webber and others, entitled “Dental appliance binding structures;” As well as any divisional or continuation application that claims priority, and any utility or preliminary application to which they claim priority. The patents/applications referred to above are hereby incorporated as if fully set forth herein.

In some embodiments the techniques described herein can also be used to create palatal expanders. U.S. Pat. No. No. 9,610,141, by inventors Kopelman and others, entitled?Arch Expanding Appliance;? U.S. Pat. No. No. 7,192,273 by McSurdy entitled “System and method for the expansion of the palatal cavity;” U.S. Pat. No. No. 7,874,836 McSurdy, inventor McSurdy, entitled “System and method for palatal extension;” As well as any divisional or continuation application that claims priority, and any utility or preliminary application to which they claim priority. The patents/applications hereby are incorporated as if fully set forth herein by reference.

In some embodiments the techniques described herein can also be used to create attachment templates. U.S. Pat. Pub. No. Boronkay, inventor. 2017/0007368 entitled “Direct fabrication of attachment template with adhesive”; U.S. Pat. Pub. No. No. 2017/0165032, by Webber et. al. entitled “Dental Attachment Placement Structure;” U.S. Pat. Pub. No. No. The contents of U.S. Patent Application Ser. No. No. 16/366686, by Webber et. al., titled?Dental Attachment Placement Structure;? As well as any divisional or continuation application that claims priority, and any utility or preliminary application to which they claim priority. The patents/applications hereby are incorporated as if fully set forth herein.

In some embodiments the techniques described herein can be applied to directly fabricate aligners. U.S. Pat. App. Pub. No. No. 2016/0310236, by inventors Kopelman and others. Titled?Direct fabrication orthodontic appliances with elastics? U.S. Pat. App. Pub. No. No. 2017/0007365, to Kopelman and co-workers, entitled “Direct fabrication of alignments with interproximal forces coupling”; U.S. Pat. App. Pub. No. No. U.S. Pat. App. Pub. No. No. 2017/0007360, to Kopelman and others, entitled “Systems, Apparatus, and Methods for Dental Appliances with Integrally Forme Features;” U.S. Pat. No. Boronkay Patent No. 10,363,116 entitled “Direct fabrication of power weapons” U.S. Pat. App. Pub. No. No. 2017/0007366, to Kopeleman and others, titled?Direct fabrication for arch expansion? U.S. Pat. App. Pub. No. No. As well as any divisional or continuation application that claims priority, and any utility or preliminary application to which they claim priority. The patents/applications cited above are hereby incorporated as if fully set forth herein.

The subject matter of U.S. Pat. Pub. No. No. 2017/0007362 by Yan CHEN and others, entitled?Dental materials using Thermoset Polymers? International Patent Application PCT/US2019/030683, to ALIGN TECHNOLOGY INC. entitled?Curable composition for use in a high temperature Lithography-based Photopolymerization process and method of producing crosslinked polymers therefrom;? and International Patent Application PCT/US2019/030687, to ALIGN TECHNOLOGY INC. entitled?Polymerizable monomers and method of polymerizing the same.? The patents/applications cited above are hereby incorporated as if fully set forth herein. Hybrid 3D printing technologies combine the advantages of SLA and DLP into a single technique that can be used to 3D print objects (dental appliances or hearing aids) “for mass production.

In certain embodiments, examples of methods include one or more of these operations: (1) Placing the first material which comprises (e.g. forms the base of) the walls in the vat. If the first material is to be treated with photocuring or other treatments, the treatment will be performed. (3) In the walls of a vat, the dispensing of one or several materials (e.g. one or two second materials), for example, in the walls formed by first material. The second material or materials can be cured using light, and/or by other mechanisms depending on the material. In certain embodiments, light is at least one cure mechanism. In some embodiments, curing of one or more materials can be controlled spatially. In some embodiments, lasers or DLPs are used to control the spatial curing of the materials. (4) If there is more than one layer to be created, the wall of the vat can be raised and the volume inside the vat filled again. Then, the curing process for the material or materials within that layer may take place. In some embodiments the process can be repeated until a complete object with its geometry or other physical properties is printed. (6) The object can then be removed from vats and cleaned using post-printing cleaning procedures.

As stated herein, in certain embodiments the use of a vessel may be optional. In some embodiments the vat may not be needed because the viscosity is high enough that it prevents the resin from flowing at the speed of the printing process. The resin material can be extruded/dispensed using Fused Deposition Modeling, which includes the use of light curing or another curing mechanism.

In some embodiments, a vat may be provided before the print process starts. This is useful for printing objects that do not have a very high height or are of the same or similar shape.

In some embodiments the vat is used as one of the materials to create the printed object.