System and method for additive manufacture of three-dimensional (3D) printed objects with uv-curable material using porous substrate

Abstract

To provide a three-dimensional (3D) object printer that reduces the amount of resin to be discarded, reduces an extent to which oxygen treatment of a resin material must be controlled, and exposes resin to radiation to form a product layer, and an operation method of the same.SOLUTION: The three-dimensional (3D) object printer operates a radiation source to direct radiation emitted by the radiation source through a porous substrate 104 at a first intensity insufficient to cure a material contained in the porous substrate and at a second intensity sufficient to cure the material after the emitted radiation has passed through the porous substrate. The material is applied to the porous substrate by one or more wipers 112.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to a three-dimensional (3D) object printer that forms a three-dimensional (3D) object by exposing a liquid material to radiation, and more particularly, to a 3D object printer that oxygen-treats a UV-curable material during object formation.

Background Art

[0002] Three-dimensional printing, also known as additive manufacturing, is a process of creating a three-dimensional solid object from a digital model of the object. Many three-dimensional printing techniques use an additive process in which an additive manufacturing device forms successive layers of a part on top of a previously formed layer. Some of these techniques use an ejection device that ejects droplets of a molten material such as a photopolymer, an elastomer, and a metal. Other additive manufacturing devices form object layers by curing a photocurable resin using visible light or UV light irradiation. One such known technique can provide a new layer formed on the upper surface of the object being manufactured. Another technique can provide a new layer on the bottom surface of the object being manufactured. All of these additive manufacturing methods are distinguishable from conventional object formation techniques that mostly rely on the removal of materials from workpieces by subtractive processes such as cutting or drilling.

[0003] Known additive manufacturing processes that expose a resin to radiation to form a product layer are very complex. They typically rely on controlling oxygen diffusion through a window in a reservoir of the resin to inhibit UV curing of the resin material for replacing a partially cured material and to regulate the flow of the resin material. More importantly, the resin material is very expensive and is a major determinant of the price of the manufactured part. The amount of material that is required for printing a part and that may be discarded after the formation of the object can be a significant amount. A printer and a method of operating the same that avoid these drawbacks would be beneficial.

Summary of the Invention

[0004] A novel method for operating an additive manufacturing system that exposes resin materials to radiation to form a material layer reduces the amount of resin waste and lessens the need to control the oxygen treatment of the resin materials. The method includes providing a first material to a first surface of a porous substrate having multiple passages extending from a first surface of the porous substrate to a second surface of the porous substrate, and operating a radiation source to direct the emitted radiation toward a support platform positioned to receive the first material from the second surface of the porous substrate through the porous substrate.

[0005] Additive manufacturing systems that expose resin materials to radiation to form material layers reduce the amount of waste resin and lessen the need to control the oxygen treatment of resin materials. The system comprises a support platform, a porous substrate having multiple passages from a first surface to a second surface of the porous substrate, and a radiation source configured to emit radiation and direct the emitted radiation through the porous substrate toward the support platform. [Brief explanation of the drawing]

[0006] The aforementioned aspects and other features of additive manufacturing systems and new additive manufacturing systems and methods for operating additive manufacturing systems that expose resin materials to radiation to form object layers, while reducing the amount of waste resin and the degree to which the oxygen treatment of resin materials must be controlled, are described in the following description made in reference to the attached drawings. The methods and systems described below use a porous substrate to oxygenate resin material up to the object / resin interface, and then concentrate the radiation intensity to a level that overcomes the oxygenated resin, partially curing it and forming an object layer before the heat treatment completes the curing of the object.

[0007] [Figure 1] This invention presents one embodiment of a 3D object manufacturing system that exposes resin material to irradiation to form an object layer while reducing the amount of waste resin and minimizing the need to control the oxygen treatment of the resin material.

[0008] [Figure 2] This is a flowchart of the process implemented by a controller that operates the system in Figure 1 to expose the resin material to radiation in order to form a material layer, while reducing the amount of waste resin and minimizing the need to control the oxygen treatment of the resin material. [Modes for carrying out the invention]

[0009] Refer to the drawings for a general understanding of 3D object printers and their operation, which expose resin materials to radiation to form object layers while reducing the amount of waste resin and minimizing the need to control the oxygenation of the resin material. In the drawings, similar reference numbers represent similar elements.

[0010] Figure 1 shows one embodiment of a 3D object printer 100 that forms an object layer by irradiating a resin material. The following description will be made with reference to the 3D object printer of Figure 1, but other embodiments consistent with the operating and configuration principles disclosed herein may be envisioned.

[0011] The printer 100 in Figure 1 includes a porous substrate 104 and a radiation source 108 that generates radiation 110 to at least partially cure a resin 116 and form a layer of object 120. As used herein, the term “porous substrate” means a planar structure having a porosity of 60% to 95%. Porosity is the ratio of the volume of air in the substrate to the volume of solid in the substrate × 100%. Contact between the resin 116 and the upper surface of the porous substrate 104 is controlled by a controller 128 that operates one or more actuators 132 to move a wiper 112 over the upper surface of the substrate 104. The controller 128 also operates one or more actuators 132 to move the radiation source 108 in and out of the plane of Figure 1 in a raster pattern over the area of ​​the porous substrate 108. That is, the radiation source moves in an XY plane parallel to the plane of the substrate 104. As used herein, the axis moving in and out of the drawing plane is called the Y-axis, and the axis perpendicular to this axis is the X-axis, although this naming may be reversed. As used herein, the term “raster pattern” means moving in a first direction along the Y-axis, then along the X-axis, and then along the Y-axis in the opposite direction to the first direction along the Y-axis. Actuator 132 also moves the wiper bidirectionally across the porous substrate 104 along the X-axis. Since one or more actuators are also operably connected to the support platform 136, the controller 128 can operate the actuators to move the platform along the Z-axis perpendicular to the XY plane parallel to the porous substrate 104, thereby maintaining separation between the upper surface of object 120 and the lower surface of the porous substrate as the object layer is formed.

[0012] More specifically, the porous substrate 104 may be a microchannel plate. A microchannel plate typically has multiple glass tubes formed thereon, each having a diameter of approximately 10–15 μm, which are fused together in a parallel arrangement to form an array. Microchannel plates are often used in electron multipliers. The inside of the tubes is coated with an emitter material that generates electrons when it receives them. Therefore, when electrons enter one end of a tube, multiple electrons are emitted at the other end. However, in the printer 100, the glass tubes of the microchannel plate provide a path for the movement of resin from the upper surface of the substrate 104 to the lower surface of the substrate, which is adjacent to the upper surface of the object 120. The coating on the inside of the channels can be used to ensure wetting and flow of the material through the channels. The wiper action, described in more detail below, biases the resin into the pores on the upper surface of the substrate 104, and this entry of the resin pushes it to the lower surface of the substrate. Since the upper and lower surfaces of the substrate 104 are exposed to ambient air, the resin within the substrate 104 remains well oxygenated. This property is important for layer formation as described below. While known microchannel plates are an effective embodiment of porous substrates, other embodiments can be used as long as the flow of resin through the substrate can be adequately controlled. For example, porous substrates 104 can be implemented using metal-organic frameworks (MOFs), zeolites, porous silicon, macroporous polymers, etc. The thickness of the porous plate is in the range of approximately 400 microns to approximately 1000 microns, regardless of the implementation. Furthermore, the porous plate can be structured to act as a lens on radiation emitted by a radiation source 108 due to its shape, refractive index variation, pore arrangement, and combination of these features. For example, the porous substrate can be manufactured to act as a Fresnel lens for UV radiation emitted by a radiation source 108. The reflection or scattering of UV radiation is given by the formula R = ((n1-n2) / (n1+n2)). 2The calculation is performed using the formula, where n1 and n2 are the reflectance indices of the porous substrate and the resin. If these indices differ by about 10%, the reflectance value is about 0.25%, which is the acceptable upper limit for UV scattering. Furthermore, a cleaning procedure may be included to prevent permanent clogging of the porous plate. One embodiment of such a substrate cleaner 158 (shown in Figure 1) includes an inert gas source 154 and a pressure source 150 for forcing the inert gas through the pores of the porous substrate. The pressure source can be a negative or positive pressure source, such as a vacuum or a compressor, respectively.

[0013] The thin layer of resin between the upper surface of object 120 and the lower surface of the porous substrate 104 is advantageous for several reasons. Firstly, the small amount of material at this interface limits resin waste during the process. Secondly, by providing small amounts of resin on the surface of the porous substrate, within the pores of the substrate, and on the surface of the object, less resin is exposed to ambient curing than the amount of resin exposed in other stereolithography processes that use a resin reservoir. Exposing the resin reservoir to ambient curing conditions limits the time the resin is in an optimal state for manufacturing, thus reducing the amount of resin wasted by the process disclosed in this document. Thirdly, changes from one material to another can occur quickly because only a small amount must be discharged through the porous substrate to place the next material on the upper surface of the object. Changes in material are useful for generating different properties in 3D objects. The thin material interface between the part and the lower surface of the porous substrate also helps ensure that the material within the substrate and the material on the upper surface of the object are adequately oxygenated.

[0014] The controller 128 can be configured to operate one or more actuators 132 to move the wipers independently or simultaneously in the same direction. Although the wiper 112 is shown as a blade in Figure 1, other implementations of wipers such as rollers and air knives can be used as well. In one embodiment, when the radiation source 108 reaches the end of its movement along the Y axis, at least one wiper follows the radiation source along the X axis in the direction in which the radiation source is moved before the radiation source is moved along the Y axis in the opposite direction to the previous Y-axis movement for the next raster pattern scan. The raster pattern movement of the radiation source may occur in this reciprocating movement of the radiation source along the Y axis separated by the movement along the X axis, but the radiation source can remain stationary, and by directing the radiation to a rotating mirror or the like within the radiation source, the emitted radiation moves across the porous plate 104 in a raster pattern in the XY plane. The movement of the wiper following the radiation beam along the X axis moves the resin into the opening on the upper surface of the porous substrate, and the movement of the wiper preceding the radiation beam wipes the upper surface clean. If the wiper's movement is temporarily stopped, a bulge of resin will form on the substrate; therefore, the controller 128 operates one or more actuators 132 to move the wiper continuously. When both the radiation source and the wiper reach the edge of the X-axis, the wiper's movement is reversed to precede and follow the reversed movement of the radiation source along the X-axis. This wiping of the material helps ensure that the material flows through the substrate and fills the space between the substrate and the upper surface of the part. Wiping can also force the material to pass through all the pores in the substrate, reducing the possibility of the material remaining in the system for too long. As previously mentioned, the wiper can also change the material used in the system. Once one material is wiped away, another material can be introduced into the system by the opposite wiper to change the properties of the object at various heights of its production. In some embodiments, a single wiper is used. In this embodiment, a single wiper follows a radiation beam to supply resin to the upper surface of a porous substrate, and on the return path, meters the resin into a uniform thin layer on the upper surface of the porous substrate before the radiation beam is guided through the porous substrate.

[0015] The controller 128 operates the radiation source 108 to focus the radiation so that its intensity is sufficient to overcome oxygen inhibition in the resin and cure only near the surface of the object 120. As used herein, the term “radiation source” means a laser or LED having an electronically controlled interface for rapidly activating and deactivating the laser or LED and directing the emitted radiation to an optical component to focus the radiation. The activation time of the radiation source must be long enough to cure the resin between the object and the porous substrate in the area of ​​focused radiation, but short enough so that the average intensity of the UV radiation in the pores does not cure the resin in the pores of the porous substrate. The presence of oxygen in the UV material inhibits the curing of the material. By adjusting the focus of the radiation, the radiation has insufficient energy to cure the resin in the porous substrate 104. Only on or near the top surface of the object 120 is there sufficient radiation energy to cure a thin portion of the resin, at least partially, to form the next layer of the object. This operation of the radiation source 108 maintains the amount of uncured resin between the object and the underside of the porous substrate until it is biased toward the object by the entry of additional resin into the porous plate. This uncured material then enters a zone where the focused energy of the radiation can at least partially cure and form the next layer of the object. The controller 128 also selectively turns the radiation source 108 on and off to shape the forming layers. Thus, this method of system operation uses less resin than conventionally known systems that require precise control of oxygen diffusion in the resin between the surface of the object and the window through which the radiation passes for the continuous formation of the object layers. Furthermore, focusing the exposure radiation is simpler than controlling the oxygen in the resin through which the radiation passes.

[0016] In another embodiment, an inert gas such as nitrogen or argon is introduced into the volume in which the object 120 is formed to reduce the amount of oxygen in the resin after it has passed through the porous substrate. This reduction in oxygen in the resin helps to reduce the intensity of radiation required for curing on the upper surface of the object. Similarly, since the oxygen level in the resin inhibits undesirable polymerization on the upper surface and inside the porous substrate, the oxygen level on the upper surface of the porous substrate can be increased to ensure this effect in the porous substrate. Using any of these methods, it is possible to ensure that the curing of the resin occurs only on the upper surface of the object and to more easily control the intensity of the radiation source at the resin / object interface.

[0017] Figure 2 shows a process for operating a 3D object printer using less resin material and requiring less control over the overall oxygen level of the resin material. In the description of the process, when the process performs several tasks or functions, it means that the controller or general-purpose processor executes program instructions stored in a non-temporary computer-readable storage medium operably connected to the controller or processor in order to perform a task or function by manipulating data or by operating one or more components in the printer. The controller 128 described above may be such a controller or processor. Alternatively, the controller may be implemented with two or more processors and associated circuits and components, each configured to form one or more tasks or functions described herein. In addition, the steps of the method may be performed in any executable chronological order, regardless of the order shown in the figure or the order in which the processes are described.

[0018] Figure 2 is a flowchart of the process for operating a 3D object printer, such as printer 100, using less resin and requiring less control of the overall oxygen level of the resin material. Process 200 begins with positioning a support platform to form a gap for holding resin between the bottom surface of the porous substrate and the top surface of the object to be formed (block 204). A wiper moves across the top surface of the porous substrate to load the resin into the pores of the porous substrate, resulting in the resin entering the gap between the porous substrate and the support platform, providing a uniformly thin layer on top of the substrate before radiation exposure (block 208). The radiation source focal length is set to focus the radiation in the gap with an intensity that at least partially cures the resin and forms the object layer (block 212). The process continues with the wiper moving continuously in sync with the movement of the radiation as the radiation source is operated and moves across the porous substrate in a raster pattern (or the radiation moves in a raster pattern) to form the object layer, wiping the surface of the porous substrate for radiation exposure and replacing the resin on the surface of the porous substrate after radiation (block 220). In other words, a wiper that moves before the radiation beam wipes the top surface of the porous substrate, and another wiper that moves in conjunction with the radiation beam, refresh the resin on the top surface and allow the resin to penetrate the porous substrate. The operation of the radiation source refers to the selective operation of the source by a digital model of the object to form layers of the object. When another layer of object is formed (block 224), the Z-axis position of the platform is adjusted so that the next layer of object is formed (block 220). Once all layers of object are formed, the process stops, and as a result the object can be heat-treated to fix the epoxy elements in the resin (block 224).

[0019] It will be understood that variations or substitutions of the features and functions disclosed above and other features and functions may, preferably, be combined into many other different systems, applications, or methods. Various currently unforeseen or unexpected substitutions, modifications, variations, or improvements, which are also intended to be covered by the following claims, may subsequently be made by those skilled in the art.

Claims

1. 1. A 3D object printer, comprising: a support platform configured to support an object made of the cured liquid photocurable resin; a porous substrate having a plurality of passages extending from a first surface of the porous substrate to a second surface of the porous substrate, the passages configured to allow flow of a liquid photocurable resin from the first surface of the porous substrate through the passages of the porous substrate to the second surface of the porous substrate; a radiation source configured to emit radiation and direct the emitted radiation through passages in the plurality of passages in the porous substrate prior to curing a portion of the liquid photocurable resin between a second surface of the porous substrate and the support platform to form a layer of the object supported by the support platform; A 3D object printer comprising:

2. a plurality of actuators, a first actuator of the plurality of actuators operably connected to the support platform and configured to move the support platform along a Z-axis relative to the porous substrate, and a second actuator of the plurality of actuators operably connected to the radiation source and configured to move the emitted radiation in an X-Y plane parallel to the first surface of the porous substrate; a controller operatively connected to the radiation source and the plurality of actuators, the controller comprising: operating the radiation source such that the emitted radiation has an intensity sufficient to cure the liquid photocurable resin only at locations between the second surface of the porous substrate and the support platform; a controller configured to operate the first actuator of the plurality of actuators to move the support platform away from the porous substrate and to operate the second actuator of the plurality of actuators to move the emitted radiation in the XY plane; The 3D object printer of claim 1 further comprising:

3. The controller:

3. The 3D object printer of claim 2, further configured to operate the second actuator of the plurality of actuators to move the radiation source in the XY plane to move the emitted radiation in the XY plane.

4. The controller:

4. The 3D object printer of claim 3, further configured to operate the second actuator of the plurality of actuators to move the radiation source in a raster pattern in the XY plane.

5. A first wiper; a third actuator of the plurality of actuators, the third actuator of the plurality of actuators being operatively connected to the first wiper; The controller, the controller is further configured to operate the third actuator of the plurality of actuators to move the first wiper across the first surface of the porous substrate and force the liquid photocurable resin into the plurality of passages in the porous substrate; The 3D object printer of claim 2 , further comprising:

6. The controller: The three-dimensional printer of claim 5, further configured to synchronize movement of the first wiper with movement of the emitted radiation in the XY plane.

7. a second wiper spaced a distance from the first wiper that is greater than a width of the emitted radiation such that the emitted radiation passes between the first wiper and the second wiper as the emitted radiation moves in the XY plane; and a fourth actuator of the plurality of actuators, the fourth actuator of the plurality of actuators being operatively connected to the second wiper; The controller, the controller is further configured to operate the fourth actuator of the plurality of actuators to move the second wiper across the first surface of the porous substrate and maintain a distance between the first wiper and the second wiper; The three-dimensional printer of claim 5 , further comprising:

8. a source of inert gas; a pressure source configured to force an inert gas from the inert gas source through the plurality of passages in the porous substrate; The three-dimensional printer of claim 2 , further comprising:

9. The three-dimensional printer of claim 8 , wherein the pressure source is a positive pressure source.

10. 10. The three-dimensional printer of claim 9, wherein the pressure source is a compressor operably connected to the inert gas source to force the inert gas through the plurality of passages in the porous substrate.

11. The three-dimensional printer of claim 8 , wherein the pressure source is a negative pressure source.

12. 12. The three-dimensional printer of claim 11, wherein the pressure source is a vacuum operatively connected to the porous substrate and pulls the inert gas released from the inert gas source through the plurality of passages in the porous substrate.

13. The controller:

3. The three-dimensional printer of claim 2, further configured to operate the radiation source for a time sufficient to cure the liquid photocurable resin at the location between the support platform and the second surface of the porous substrate without generating an average intensity of the radiation within any of the plurality of passages in the porous substrate sufficient to cure the liquid photocurable resin within any of the plurality of passages in the porous substrate.

14. The porous substrate further comprises:

2. The three-dimensional printer of claim 1, comprising a plurality of glass tubes, each glass tube of the plurality of glass tubes having a first end and a second end, the glass tubes of the plurality of glass tubes being arranged parallel to one another such that the first ends of the glass tubes of the plurality of glass tubes are located on the first surface of the porous substrate and the second ends of the glass tubes of the plurality of glass tubes are located on the second surface of the porous substrate.

15. A 3D printer as described in claim 14, wherein each glass tube of the plurality of glass tubes has a diameter in the range of 10 to 15 μm.

16. A 3D printer as described in claim 14, wherein the length of each of the plurality of glass tubes is 400 to 1000 μm.

17. A 3D printer as described in claim 16, wherein each glass tube of the plurality of glass tubes has a diameter in the range of 10 to 15 μm.

18. The 3D printer of claim 1, wherein the porous substrate is one of a metal-organic framework, a zeolite, a porous silicon substrate, and a macroporous polymer substrate.

19. A 3D printer as described in claim 1, wherein the reflectance of the photocurable resin passing through the porous substrate and the reflectance of the porous substrate differ from each other by 10%.

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