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KR-102961855-B1 - System and method for preventing oxygen inhibition of photoinitiated polymerization reaction in a 3D printing system using an inert gas

KR102961855B1KR 102961855 B1KR102961855 B1KR 102961855B1KR-102961855-B1

Abstract

A system and method for preventing oxygen inhibition of a photoinitiated polymerization reaction by purging oxygen from a reaction surface using an inert gas flow. In some embodiments, oxygen is purged using a gas diffusion system that introduces an inert gas into the workspace between a UV light source and a UV-curable layer of a workpiece through a diffuser. The diffuser may be made of a transparent or diffusing material to allow UV light to pass through and includes an array of micro-holes through which the gas can pass toward the workpiece. The inert gas flow may be heated to maintain a desired uniform reaction temperature.

Inventors

  • 제노우 마이클
  • 길란 지브
  • 립츠 다니엘
  • 샤이 유발

Assignees

  • 아이오 테크 그룹 엘티디.

Dates

Publication Date
20260507
Application Date
20191204
Priority Date
20181211

Claims (20)

  1. A system (20) for preventing oxygen inhibition of a light-initiated polymerization reaction in ambient conditions used by a 3D printing system, wherein the system comprises a UV curing space (40) for accommodating a workpiece (34) having a layer (36) of a UV-curable material and a UV curing space (40), and means for purging oxygen from the UV curing space to facilitate UV curing of the UV-curable material when the UV light source (26) emits light onto the layer (36) of the UV-curable material within the UV curing space (40), wherein the means for purging oxygen comprises a gas diffusion system (22) for introducing an inert gas into a workspace between the UV light source (26) and the layer (36) of the UV-curable material of the workpiece (34), and a transparent cover separating the UV light source (26) and the workspace A system comprising a cover (24), wherein the gas diffusion system (22) and the transparent cover (24) are arranged such that an inert gas introduced from one or more gas inlets (28) of the gas diffusion system (22) can be discharged toward the workspace through a diffuser (30), and the diffuser (30) has a plurality of micro-holes (38) having a bridge (42) of UV transparent material arranged over the micro-holes (38) so as to be positioned between each inlet of the micro-hole and the transparent cover (24).
  2. A system according to claim 1, further comprising a gas pressure homogenizer (32) for ensuring a constant pressure across the system.
  3. A system according to claim 1, wherein the diffuser (30) is made of a UV-transparent material to allow UV light from a UV light source (26) to pass through it.
  4. In claim 1, the microholes (38) are a system with a defined size and spacing relative to each other to optimize gas distribution and UV light distribution across the workspace.
  5. In paragraph 4, the microholes (38) are spaced apart from each other in an array so that the gas is distributed approximately evenly across the workspace and are of the same size so that UV light is distributed approximately evenly within the workspace.
  6. In claim 1, the microholes (38) are spaced apart from each other in an array so that the gas is distributed approximately evenly across the workspace and UV light is distributed approximately evenly within the workspace.
  7. A method for preventing oxygen inhibition of a photoinitiation polymerization reaction under ambient conditions used by a 3D printing system, the method comprises the step of periodically emitting ultraviolet (UV) light from a UV light source (26) into a UV curing space (40), wherein, within the UV curing space (40), a workpiece (34) having a layer (36) of a UV-curable photopolymer is placed under the ambient conditions to facilitate UV curing of the UV-curable photopolymer, and the step of purging oxygen from the UV curing space (40) when the UV light source (26) emits light over the layer (36) of the UV-curable photopolymer. The step of purging oxygen from the above UV curing space includes the step of introducing an inert gas into the working space between the UV light source (26) and the layer (36) of the UV-curable photopolymer of the workpiece (34) through a gas diffusion system (22). The above inert gas is introduced into the workspace through one or more gas inlets (28) of the gas diffusion system (22) and through a plurality of microholes (38) of a transparent diffuser (30) that separates the UV light source (26) from the workspace, and A method in which UV light from a UV light source (26) passes through a bridge (42) of UV transparent material arranged over the microhole (38) of the diffuser (30) toward a layer (36) of UV-curable photopolymer of a workpiece (34).
  8. In claim 7, the method of distributing the inert gas approximately evenly across the workspace through the microholes (38).
  9. In claim 7, the UV light is distributed approximately evenly within the workspace through the microhole (38).
  10. In claim 7, the step of purging oxygen from the UV curing space (40) is initiated by introducing an inert gas through a diffuser (30) into the UV curing space (40) where the workpiece (34) is located while a layer (36) of the UV-curable photopolymer is deposited over the workpiece (34), and the inert gas is introduced at a pressure sufficient to purge oxygen from an area adjacent to the diffuser (30).
  11. A method according to claim 7, further comprising the step of repositioning the workpiece (34) for the deposition of the next layer of UV-curable photopolymer after the curing of the layer (36) of the UV-curable material and reducing the inert gas pressure in an area adjacent to the diffuser (30).
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Description

System and method for preventing oxygen inhibition of photoinitiated polymerization reaction in a 3D printing system using an inert gas The applicant claims priority to U.S. provisional application number 62/777,902 filed on December 11, 2018. The present invention relates to a system for preventing oxygen inhibition in a light-initiated polymerization reaction used by a 3D printing system by purging oxygen from a reaction surface using an inert gas flow. Many additive manufacturing or so-called three-dimensional ("3D") printing applications use ultraviolet ("UV") photocurable polymers. The UV curing process consists of three stages: photoinitiation, propagation, and termination. During photoinitiation, the photoinitiator generates free radicals when exposed to ultraviolet light. These free radicals react with nearby monomers and convert them into free radicals. Next, in the propagation stage, the free radical monomers combine with other monomers and convert those monomers into free radicals. In this way, the monomers form polymer chains. This process continues until termination. Termination can occur in several ways, including when two chains combine, when free radicals move to the monomers, or when the chains react with molecules in the environment that are not monomers. There are two interactions between oxygen and photopolymers that inhibit curing: quenching and scavenging. When a photoinitiator is excited by exposure to ultraviolet light, free radicals are generated. Molecular oxygen readily reacts with these free radicals, preventing them from reacting with monomers during chain propagation. This is the quenching reaction. This reaction also generates oxygen free radicals. In the scavenging reaction, these oxygen free radicals react with free radicals that are part of the propagating polymer chain. This reaction generates less reactive free radicals, thereby terminating the polymerization process prematurely. These two processes can be described as follows. ??ching reaction: PI * + O 2 → PI + O 2 * Scavenging reaction: R · + O 2 * → ROO · FIGS. 1a-1c illustrates points of a conventional 3D printing process in which a layer of UV-curable material is deposited on an object to be printed (Fig. 1a) (Fig. 1b), which is then exposed to UV light to cure (Fig. 1c). FIG. 2 illustrates a UV curing system configured according to one embodiment of the present invention in which an inert gas flow is arranged to prevent oxygen inhibition of the polymerization process during the UV curing process. Figures 3a and 3b illustrate the operation of the UV curing system shown in Figure 2. Figures 4a and 4b illustrate examples of a UV light source and gas diffuser arrangement for a UV curing system as shown in Figure 2. Figures 5a and 5b illustrate aspects of the gas diffuser array shown in Figures 4a and 4b. FIGS. 6a and 6b illustrate the operation of the UV curing system shown in FIG. 2, specifically a series of printing, inert gas flow and UV curing processes (Fig. 6a), and the expansion of the oxygen-free layer (Fig. 6b). It is helpful to provide an overview before describing the invention in detail. Referring to the series of images illustrated in FIGS. 1a, 1b and 1c, in many 3D printing processes in which an object (10) is being manufactured, a material printing system (12) is used to deposit a UV-curable material (14) on a surface (16). This deposited material is then cured with a UV light source (18) to create a new layer of the desired part (10'). This process continues until the part being manufactured is completed. Embodiments of the present invention provide a system and method for preventing oxygen inhibition of a photoinitiated polymerization reaction under ambient conditions. Referring now to FIG. 2, in one embodiment of the present invention, a UV curing system (20) is equipped with a gas diffusion system (22). A transparent cover (24) is placed between a UV light source (26) and the gas diffusion system (22). Gas is introduced from a gas inlet (28) and exits through a diffuser (30) located at the bottom of the system. A gas pressure homogenizer (32) is used to ensure a constant pressure throughout the system. The diffuser (30) is made of a transparent or diffusing material so that UV light can pass through the workpiece (34), specifically the layer (36) of UV-curable material placed over it. The diffuser (30) is composed of an array of microholes (38). The small diameter of the microholes enables a dense array, allowing the gas to be evenly distributed over the entire curing area (40). The small diameter of the microholes (38) also means that there are no holes over a wider area of the diffuser (30) surface, resulting in more uniform optical properties. This ensures more even light distribution. Of course, other arrangements and sizes of the microholes may be used to optimize gas distribution and light distribution over the entire curing area. The microholes (38) are covered with a "bridge" (42) of the mate