Powder additive manufacturing

Abstract

To provide a method of three-dimensional lamination molding for laminating powder using a binder capable of neglecting powder fluidity which is problematic in a powder use additive manufacturing which is assumed to be sintering.SOLUTION: There is provided a method which is not affected by powder fluidity, the method is configured to: first, inject a binder for one layer, immediately after the injection of the binder, pressure-contact a mass of powder to a binder printing surface, then immerse the powder by a capillary phenomenon followed by wetting of powder and the binder for integrating the powder and the binder. Then, excess and isolated powder is separated, only the powder integrated to the binder is caused to remain, and then, the remaining binder is cured. These steps are repeated for performing three dimensional lamination molding. The acquired lamination molded article (Green) is subjected to defatting and sintering for acquiring a sintered body.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] A three-dimensional additive manufacturing method that uses a binder to layer powder [Background technology]

[0002] In additive manufacturing technology based on powder sintering, there are five types of 3D additive manufacturing methods that use a binder to layer powder: Material Extrusion, Vat Photo Polymerisation, Screen Printing Photo Polymerisation, Cold Metal Fusion / Powder Bed Fusion using binder-coated powder, and Binder Jetting. All of these additive manufacturing objects (Green) are debound and sintered to create a sintered body. Problems that the invention aims to solve

[0003] These five types of modeling methods all use powder, so they are affected by powder flow. In the fused deposition modeling and binder jetting methods, a single layer of powder is spread on a powder bed, but the finer the powder, the larger the specific surface area, which increases interparticle friction and significantly reduces powder flowability. As a result, it is not possible to ensure the necessary and sufficient bulk density. In practice, coarse powder with a diameter of several tens of micrometers or more is required, which limits fine modeling. To solve this problem, the material extrusion method, liquid vat photopolymerization method, and screen printing photopolymerization method use materials that have improved fluidity by mixing powder with a binder with high fluidity. However, the dimensions of the material extrusion method are governed by the nozzle diameter, which is large at several hundred micrometers, and there are limitations to fine modeling. In addition, the material of the liquid vat photopolymerization method is a muddy material with low viscosity, so settling and separation of the powder is an issue. Furthermore, the dimensions of the screen printing photopolymerization method are governed by the screen thickness, so the layer thickness of one layer is several hundred micrometers, which is a large issue.

[0004] The present invention aims to provide a method for three-dimensional additive manufacturing in which powder is layered using a binder that solves all five of the above problems.

[0005] In the present invention, a layer of binder is first sprayed, and immediately afterwards, a mass of powder is pressed into contact with the binder-printed surface, soaking and integrating the binder and powder through capillary action that involves wetting the binder. Next, the free excess powder is separated, leaving only the powder integrated with the binder, and the remaining binder is then hardened. This process is repeated to perform three-dimensional additive manufacturing. The resulting additive manufactured object (Green) is then degreased and sintered to obtain a sintered body. The powder used can be metal powder, ceramic powder, or a mixture of these. Effects of the Invention

[0006] The powder used in one lamination is treated as a lump, so there is no need to consider powder flow at all. Therefore, even fine powders with extremely poor powder flow, such as nanopowder, can be used. Also, since no sludgy material is used, there is no concept of separating the powder and the binder. Furthermore, since the thickness of one layer depends only on the amount of one drop sprayed from the binder jet, minute dimensions can be freely formed. Also, powder used once can be recovered and reused many times. [Brief description of the drawings]

[0007] [Figure 1] This is a schematic diagram of a 3D additive manufacturing device at the stage where the first layer has been formed after all the steps of the inkjet printing process, the process of soaking the powder into the inkjet area, the process of removing the loose powder, and the final process of curing by light irradiation have been completed in sequence (Figure 1). EXAMPLES

[0008] The rotating platform 1, which has four stages and is driven by a 90-degree rotation indexing drive, rotates 90 degrees for each step. At that time, the opening and closing shutter 3 opens and closes in synchronization with the rotation so that the rotating object does not interfere. In the first step, the shape of one layer is jet-printed with a light-curing binder on the stage of the platform by a print head 2 that CNC-controls the XYZ axes. In the second step, a lump of fine powder 7-1 is dropped and pressure and vibration are applied to soak the powder into the printed binder. In the third step, the loose powder 7-2 is dropped and sucked and collected by the powder suction and collection nozzle 4, leaving only the printed binder 6-3 integrated with the powder. In the fourth step, the printed binder integrated with the powder is solidified by photopolymerization by irradiating it with light, and then the minute loose powder remaining around the binder is removed by an air blower 8. By repeating this process, a three-dimensional additive manufacturing object is created.

[0009] The binder used may be not only a light-curing binder but also a heat-melting binder or a heat-curing binder. Instead of the light irradiation in the four steps, cooling heat transfer is used to harden the heat-melting binder, and heating heat transfer is used to harden the heat-curing binder. [Explanation of symbols] 1 Rotating Platform 2 Print head 3 Opening and closing shutter 4 Powder suction recovery nozzle 5. UV light 6-1 Printed binders 6-2 Printed binder soaked in powder 6-3 Printed binder with loose powder removed 6-4 Light-cured printed binder 7-1 Powder lump 7-2 Free powder 8 Air blow nozzle

Claims

1. This is a powder additive manufacturing method in which, immediately after printing a liquid binder on the stage surface of a platform and before the binder hardens, a block of powder to be used in one layer is pressed into contact with the entire stage surface on which the liquid binder is printed, the powder is immersed in the binder to integrate it, any other loose powder is completely removed, the binder integrated with the powder is hardened to form a single layer, and then, for the second layer and beyond, four steps are repeated to create a molded object: the binder printing step, the powder pressure contact step in which a block of powder to be used in one layer is supplied and pressed, the loose powder removal step, and the binder hardening step.

2. An additive manufacturing device having a platform, a binder printing means for printing a binder onto the platform, a powder pressure contact means for supplying and pressurizing a block of powder to be used in one lamination, and a loose powder removal means, and after forming one layer through a binder printing process, a powder pressure contact process for supplying and pressurizing a block of powder to be used in one lamination, a loose powder removal process, and a binder hardening process, for the second layer and thereafter, a three-dimensional additive manufacturing object is created by repeating four processes: a binder printing process, a powder pressure contact process for supplying and pressurizing a block of powder to be used in one lamination, a loose powder removal process, and a binder hardening process.

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