Method of removing support structure material

Abstract

To provide a method of removing a support structure material which can simply remove a support structure material from a workpiece and easily performs automation.SOLUTION: A method of removing support structure material includes a process of suspending grinding material (2) into processing liquid (1), a process of installing an additively manufactured workpiece (3) which contains a support surface (3a) having a support structure material (3b1) for fixing the workpiece (3) onto a molding platform (3c) in an area in which the grinding material (2) in the processing liquid (1) is suspended, a process of causing a nozzle (15) sunk in the processing liquid (1) to jet a cavitation jet (6) in the processing liquid (1) to the workpiece (3) and a process of removing the support structure material (3b1) attached to the workpiece (3).SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a method for removing a support structure. [Background technology]

[0002] Metallic materials produced by additive manufacturing include the support structures required for the additive manufacturing process to support the part on the build platform, which are primarily removed by hand or by machining. Summary of the Invention [Problem to be solved by the invention]

[0003] Removing the supporting structure from the metal material requires skilled techniques. The process of removing the supporting structure poses challenges in terms of quality safety and production automation. An object of the present invention is to simplify and automate the removal of a support structure from a workpiece. [Means for solving the problem]

[0004] The first aspect of the present invention is An abrasive is suspended in the treatment liquid, placing an additively manufactured workpiece in a region of the processing liquid where the abrasive material is suspended, the region including a support surface having a support structure for securing the workpiece to the build platform; A nozzle submerged in the processing liquid sprays a cavitation jet of the processing liquid onto the workpiece to remove the support structure material adhering to the workpiece. A method for removing a support structure.

[0005] The structure of the support structure material is, for example, a block support, an adaptive cell support, a rod support, a line support, and a tree support.

[0006] During additive manufacturing, the workpiece is supported by the support structure from the build platform and is built. The workpiece is separated from the build platform by cutting the support structure. The support surface is, for example, the portion of the workpiece surface that was attached to the support structure. The tip of the support structure adheres to the support surface. The tip of the support structure remains on the support surface. For example, the support structure remains slightly from the support surface of the workpiece. Here, "slightly" refers to, for example, a height of about 0.3 to 1 mm (including both ends).

[0007] The angle between the nozzle and the support surface may be between 10 degrees and 20 degrees. The treatment liquid is, for example, water, and may contain a rust inhibitor. The abrasive is abrasive particles. The abrasive is, for example, ceramic. The abrasive is, for example, alumina, garnet, or zirconia. Simultaneously with removal of the support structure, the support surface is smoothed. Effect of the Invention

[0008] According to the present invention, removal of the support structure from the workpiece can be performed simply and easily automated. [Brief description of the drawings]

[0009] [Figure 1] 1 is a flowchart showing a method for removing a support structure of a workpiece according to an embodiment of the present invention. [Diagram 2] FIG. 1 is a schematic diagram of a workpiece formed on a modeling platform according to the present embodiment; [Diagram 3] FIG. 1 is a schematic diagram of a workpiece separated from the build platform of the present embodiment; [Figure 4] Apparatus for removing support structure material from a workpiece according to the present embodiment [Diagram 5] Photographs of the workpiece before and after removal of the support structure in Example 1 [Figure 6] Photographs of the workpiece before and after removal of the support structure in Example 2 DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] As shown in FIG. 1, the method for removing a support structure of a workpiece in this embodiment includes additively manufacturing the workpiece 3 (step S1), cutting the support structure 3b of the workpiece 3 (step S2), immersing the workpiece 3 and the nozzle 15 in a processing liquid 1 containing an abrasive 2 (step S3), and performing cavitation jet processing (step S4).

[0011] In step S1, additive manufacturing is performed, for example, by 3D printing. The 3D printing is, for example, Powder Bed Fusion (PBF). The additively manufactured workpiece 3 has tensile residual stress. As shown in FIG. 2, the additively manufactured workpiece 3 is supported by a number of support structures 3b on a build platform 3c.

[0012] In step S2, the support structure 3b is cut at the cutting surface 9, and the workpiece 3 is separated from the build platform 3c. Preferably, the cutting surface 9 is in the vicinity of the workpiece 3. The surface to which the tip of the support structure 3b is connected is the support surface 3a. The support surface 3a may be a curved surface. As shown in Fig. 3, a portion 3b1 of the support structure 3b is attached to the support surface 3a. The length of the support structure 3b varies depending on the shape of the workpiece 3 and the posture of the workpiece 3 when it is molded on the molding platform during manufacturing. The length 3b2 of the support structure 3b1 attached to the workpiece 3 is, for example, 0.3 mm to 100 mm. The length 3b2 of the support structure 3b1 is preferably 0.3 mm to 20 mm, and more preferably 0.3 mm to 0.5 mm. The support structure 3b may be in the shape of a rectangular column, or may be a block support, an adaptive cell support, a line support, or a tree support.

[0013] Next, the support structure removal device 10 for the workpiece 3 will be described. As shown in Fig. 4, the support structure removal device 10 includes a treatment tank 11, a high-pressure treatment liquid source 13, a nozzle 15, a moving device 16, a pressure gauge 17, an agitation liquid source 18, an agitation block 19, and an agitation nozzle 20.

[0014] The processing tank 11 is open upward. The processing tank 11 stores a processing liquid 1 and an abrasive 2. The high-pressure processing liquid source 13 is, for example, a piston pump. The high-pressure processing liquid source 13 pressurizes the processing liquid 1 and supplies it to the nozzle 15.

[0015] The moving device 16 is, for example, a robot such as a vertical articulated robot, a horizontal articulated robot, an orthogonal axis robot, a parallel link robot, etc. The moving device 16 may be a spindle head moving device of a column traverse type machining center.

[0016] The nozzle 15 is disposed on a moving device 16 and is moved by the moving device 16. The nozzle 15 is immersed in the processing liquid 1 stored in the processing tank 11. The nozzle 15 sprays the processing liquid 1 along a spray axis 15a. For example, the spray axis 15a extends from the horizontal to a vertically downward direction (vertically downward direction in FIG. 4). Preferably, the nozzle 15 has a structure that generates a vortex between the processing liquid 1 and the jet 6, promoting the generation of a cavity. The pressure gauge 17 detects the discharge pressure from the high-pressure processing liquid source 13 .

[0017] The agitating liquid source 18 is, for example, a centrifugal pump or a diaphragm pump. The agitating block 19 is disposed at the bottom of the treatment tank 11. The agitating block 19 is connected to the agitating liquid source 18. The agitating block 19 has an agitating nozzle 20.

[0018] In step S3, the workpiece 3 is immersed in the processing liquid 1 stored in the processing tank 11. The support surface 3a is disposed facing the nozzle 15 (slightly upward from the vertical in FIG. 4). The support surface 3a may be disposed vertically, for example. The support surface 3a may be inclined from the vertical. The angle 4 between the injection axis 15a and the support surface 3a is, for example, 0 degrees to 90 degrees, and particularly preferably 10 degrees to 20 degrees. The inclination or perpendicularity of the support surface 3a to the injection axis 15a promotes the removal of the support material 3b1. Even if the support material is a high-strength support material such as a block support or an adaptive cell support, the support material can be effectively removed by setting the angle 4 to 10 degrees to 20 degrees.

[0019] In step S4, the stirring nozzle 20 injects the processing liquid 1 into the processing tank 11 and stirs the abrasive 2. The abrasive 2 floats in the processing tank 11 and becomes a turbid liquid 5. The workpiece 3 is in the turbid liquid 5. The nozzle 15 is immersed in the processing liquid 1 and injects the processing liquid 1. The jet 6 of the nozzle 15 engulfs the abrasive 2 and collides with the support surface 3a. Then, as shown by the arrow 7, the jet 6 flows along the support surface 3a. At this time, the abrasive 2 also flows in the direction of the arrow 7. Then, the support structure 3b1 is removed. In addition, the support surface 3a is smoothed. Since the abrasive 2 flows near the support structure 3b1, the removal of the support structure 3b is promoted. When the height 3b2 of the support structure 3b1 is high, the jet 6 collides with the base of the support structure 3b1 (the boundary between the support structure 3b1 and the workpiece 3). At this time, the jet 6 accompanied by the abrasive 2 breaks the support structure 3b1 from the base. Furthermore, the jet 6 accompanied by the abrasive 2 scrapes off the support structure 3b1 remaining on the support surface 3a. The jet 6 ejected from the nozzle 15 promotes the generation of cavities. Cavities are microscopic bubbles that appear and disappear in a short time due to pressure differences in the flow of fluid. The cavities are carried by the jet 6 and introduced to the periphery of the support surface 3a. When the cavities disappear, a localized forceful flow of fluid collides with the surface of the support surface 3a, resulting in a peening process. When a peening process is performed by colliding a cavitation jet with the support surface 3a (hereinafter referred to as cavitation peening), residual compressive stress is imparted to the surface of the support surface 3a.

[0020] It is necessary to remove the support structure 3b1 associated with the workpiece 3. According to the present invention, the support structure 3b1 associated with the workpiece 3 can be effectively removed. Furthermore, there may be cases where an incompletely melted region exists on the surface of the additively manufactured workpiece 3. According to the present invention, the surface of the workpiece 3 can be ground to remove the incompletely melted region remaining on the support surface 3a. According to the method for removing a supporting structure of this embodiment, even if the workpiece 3 has a mesh-like shape, the supporting structure can be effectively removed. Also, the supporting structure disposed inside the workpiece 3 can be effectively removed.

[0021] Additively manufactured workpieces have tensile and compressive stresses. It may be desirable to improve the fatigue strength of the additively manufactured workpiece. According to the present invention, compressive residual stress is imparted to the surface of the additively manufactured workpiece, thereby improving the fatigue strength. EXAMPLES

[0022] Referring to FIG. 5, a workpiece 103 made of Ti-6Al-4V alloy was manufactured by additive manufacturing using the powder bed method. The workpiece 103 has a flat support surface 103a. The support structure 103b1 is a block support. The workpiece 103 was prepared by cutting the support structure 3b at a height of 2 mm from the support surface 103a. The support structure 103b1 attached to the workpiece 103 is uniformly arranged on one side of the support surface 103a. Injection conditions: Processing liquid: Water Abrasive: Alumina #150 (average particle size 70-100μm) Amount of abrasive: 30% by weight of processing liquid Workpiece immersion depth D2: 300 mm (see Figure 4) Angle 4: 20 degrees Nozzle diameter: 0.5mm Injection pressure: 130MPa Feed speed: 0.3mm / s Nozzle offset amount D1: 50mm (see Figure 4) Nozzle movement path: A path 25 that scans by turning back and forth along multiple parallel lines spaced at intervals 27 (see the upper diagram in Figure 5) Spacing 27:4mm Number of passes: 7

[0023] The surface of the workpiece 3 before and after submerged spraying was photographed with an optical microscope. A Keyence VXH-6000 was used as the optical microscope. Additionally, the surface residual stress of the workpiece 3 before and after submerged spraying was measured using X-ray stress measurement (cos α method). The X-ray stress measurement device used was a Pulstec Industrial μ-X360s portable X-ray residual stress measurement device. Residual stress was measured at several specific locations on the workpiece 3.

[0024] (result) Photographs of the support surface 103a of the workpiece 3 in the embodiment before and after the cavitation jet treatment are shown in Fig. 5. The upper photograph in Fig. 5 shows the surface before treatment. The lower photograph in Fig. 5 shows the surface after treatment. In the embodiment, the support structure material 103b attached to the workpiece 103 was effectively removed. The surface residual stress after treatment in the embodiment was -205 MPa. EXAMPLES

[0025] Referring to FIG. 6, a workpiece 203 made of Ti-6Al-4V alloy was manufactured by additive manufacturing using the powder bed method. The workpiece 203 is a surgical implant. The workpiece 203 has a mesh structure. The workpiece 203 also has a support structure 203b1 inside the workpiece 203. The support structure 203b1 is a rod support. The workpiece 203 is rounded overall, and the height, width, and thickness of the support structure 203 differ for each support structure 203b1. The dimensions of the support structure 203b1 attached to the workpiece 3 are, for example, as follows: Width (left and right in Fig. 6): 6 to 10 mm (varies by area) Thickness (perpendicular to the paper surface of Figure 6): 1 mm Height 3d2: 25-30mm (varies by part) The workpiece 3 was placed in the treatment tank 11 so that the support structure 203b1 extended horizontally. The nozzle 15 was placed facing downward. In other words, the support surface 203a was approximately parallel to the injection axis 15a. The workpiece 203 was subjected to submerged injection treatment under the following conditions. Injection conditions: Angle 4: 0 degrees to 20 degrees (varies by area) Feed speed: 1mm / s Nozzle movement path: Path 29 passing near the boundary between the support structure 203b1 and the workpiece 203 (upper diagram in FIG. 6) Number of passes: 1 The other conditions were the same as in Example 1.

[0026] (result) Photographs of the workpiece 203 in this example before and after the cavitation jet treatment are shown in Figure 6. The upper image in Figure 6 is before treatment, and the lower image in Figure 6 is after treatment. In this example, the support structure material 203b1 adhering to the workpiece 203 was effectively removed. Inside the tank, the support structure material 203b1 had fallen in large chunks. The surface residual stress after treatment in this example was -205 MPa.

[0027] The removal of the support structure is believed to proceed as follows: First, the support structure 203b1 is broken near the support surface 203a by the kinetic energy of the abrasive and the processing liquid, and is separated from the workpiece 203. Next, the support structure remaining on the support surface 203a is removed by the flow of the abrasive, the dynamic pressure of the processing liquid, and the impact force caused by the bursting of the cavity.

[0028] The present invention is not limited to the above-described embodiment, and various modifications are possible without departing from the gist of the present invention, and all technical matters included in the technical ideas described in the claims are the subject of the present invention. The above-described embodiment shows a preferred example, but a person skilled in the art can realize various alternatives, modifications, variations, or improvements from the contents disclosed in this specification, and these are included in the technical scope described in the attached claims. [Explanation of symbols]

[0029] 1 Processing solution 2 Abrasive material 3 Work 3a Support surface 3b, 3b1 Support structure material 6. Jet 15 Nozzles

Claims

1. The abrasive is suspended in the treatment liquid. placing an additively manufactured workpiece in a region of the processing liquid where the abrasive material is suspended, the region including a support surface having a support structure for securing the workpiece to the build platform; A nozzle submerged in the processing liquid sprays a cavitation jet of the processing liquid onto the workpiece to remove the support structure material adhering to the workpiece. How to remove support structures.

2. The nozzle sprays the treatment liquid in a direction ranging from vertically downward to horizontally sideways. The method of claim 1 .

3. A compressive residual stress is imparted to the surface of the workpiece.

3. A method for removing a support structure according to claim 1 or 2.

4. The support structure includes only a tip portion of the support structure that is attached to the support surface after being cut. A method for removing a supporting structure material according to any one of claims 1 to 3.

5. The workpiece has a mesh structure. A method for removing a support structure according to any one of claims 1 to 4.

6. The angle between the nozzle and the support surface is between 0 degrees and 20 degrees. A method for removing a supporting structure according to any one of claims 1 to 5.

Images