Electrode for sculpting electrical discharge machining

Abstract

To provide an electrode for die sinking by which electrical discharge machining can be carried out at a high machining speed by maintaining a flow channel that permits passage of a working fluid in the interior of the electrode even when a hole opened in a workpiece has a non-circular shape or two or more holes are opened.SOLUTION: An electrode for die sinking is made by disposing, in the interior of a cylindrical outer cylinder part, an electrode part provided with a plurality of protrusions that are not uniform in a length direction of a cylinder. In the electrode for die sinking, because a working fluid can be passed in a length direction of the electrode, discharge is stable and machining speed is high, and it is possible to carry out machining that leaves no core of a workpiece without rotating the electrode.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to an electrode for profile electric discharge machining for performing machining on a conductive workpiece by electric discharge machining.

Background Art

[0002] Profile electric discharge machining has long been used to machine workpieces made of metal or other conductive materials. Recently, electrodes for profile electric discharge machining have also been manufactured by three-dimensional layered manufacturing (so-called 3D printers). (For example, cited reference 1). Also, in profile electric discharge machining, when it is desired to form a particularly circular through-hole, a pipe-shaped electrode 5 is used. The pipe-shaped electrode 5 can flow a machining fluid (oil or ionic water) from inside the pipe, and since it is easy to discharge machining debris, it is possible to increase the machining speed. Further, a method of machining while rotating the electrode using an electrode called a "coreless" having a non-concentric "wall" in the longitudinal direction inside the pipe is also generally used (for example, Patent Document 2).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] The pipe-shaped electrode 5 is used when forming a circular through-hole. The problem with the pipe-shaped electrode is that, as shown in FIGS. 6(a) to (c), as electric discharge machining progresses, unprocessed remnants of the workpiece called "cores" occur inside the pipe, and if these cores break, it causes blockage of the pipe and abnormal electric discharge (c). In contrast, by using a pipe electrode with a "wall" on the inner diameter side of the pipe, as described in Prior Art Document 2, and performing electrical discharge machining while rotating the electrode, the portion that contacts the core can be simultaneously machined by the "wall" inside the electrode, thus avoiding problems caused by the core remaining. However, when the shape of the hole to be machined is not circular, such as a square or ellipse, or when machining two or more holes simultaneously, it is not possible to perform the machining while rotating the coreless electrode, and electrical discharge machining (EDM) cannot be performed while actively removing machining chips. For this reason, in these cases, it is only possible to manufacture a full-shape electrode and perform slow, unstable EDM with the machining fluid flowing only to the outside of the electrode. The objective of this invention is to provide an electrode for die-sinking electrical discharge machining that can perform electrical discharge machining at a high machining speed by ensuring a flow path for the machining fluid inside the electrode, even when the hole drilled in the workpiece is non-circular or there are two or more holes. [Means for solving the problem]

[0005] In this invention, for die-sinking electrical discharge machining, An electrode for die-sinking electrical discharge machining, having an electrode section with multiple protrusions inside a cylindrical outer section that are not uniform in the longitudinal direction of the cylinder. This solved the aforementioned problem. This electrode for die-sinking electrical discharge machining may be configured such that the multiple protrusions are located on any straight line connecting the two ends of the cylinder in parallel. Furthermore, in this electrode for die-sinking electrical discharge machining, the multiple protrusions have through-confirmation sections with a width less than or equal to the discharge gap, which allow light to pass linearly from one end of the cylinder to the other, and may also be provided on any other straight line connecting the two ends of the cylinder in parallel. Furthermore, the device may have multiple electrode sections as described above. [Effects of the Invention]

[0006] By using the electrode for die-sinking electrical discharge machining of the present invention, high-speed electrical discharge machining can be performed when drilling non-circular shapes or two or more holes simultaneously. [Brief explanation of the drawing]

[0007] [Figure 1] One embodiment of the electrode portion of the electrode for die-sinking electrical discharge machining according to the present invention [Figure 2] Schematic diagram of a coreless electrode [Figure 3] One embodiment of the electrode portion of the electrode for die-sinking electrical discharge machining according to the present invention [Figure 4] One embodiment of the electrode for die-sinking electrical discharge machining according to the present invention [Figure 5] One embodiment of the electrode for die-sinking electrical discharge machining according to the present invention [Figure 6] Die-sinking electrical discharge machining using pipe-shaped electrodes [Modes for carrying out the invention]

[0008] The present invention describes an electrode for die-sinking electrical discharge machining. The electrode for die-sinking electrical discharge machining of the present invention is An electrode for die-sinking electrical discharge machining, having an electrode section with multiple protrusions inside a cylindrical outer section that are not uniform in the longitudinal direction of the cylinder. That is the case. The term "tubular" can refer to various shapes, such as cylindrical or rectangular tubes. The significance of a tubular shape lies in the fact that the electrode shaft of the processing machine can spray (or suck) processing fluid from inside the tube, actively removing processing debris. Therefore, the shape should allow processing fluid to flow through both the tip and the base of the tube. "Not uniform in the longitudinal direction of the cylinder" means that when the position is shifted parallel to the longitudinal direction of the electrode from a specific position on the electrode cross-section, there is an electrode at some points and no electrode at other points (for example, as shown in Figure 2, commercially available coreless electrodes 6 are uniform in the longitudinal direction). With this configuration, as electrical discharge machining progresses and the electrode penetrates to a certain depth, the part of the workpiece that would remain as a core if there were no protrusions will also be subjected to electrical discharge machining, making it less likely for the core to remain even while the machining fluid is passing through (Figure 2). The protrusion 2 may have a step, as shown in Figures 1(a) and (b), or it may be a stepless bulge toward the center of the electrode, as shown in (c). To obtain the above electrodes, for example, multiple rod-shaped electrode materials can be inserted and fixed into a pipe electrode, or a pipe-shaped electrode with protruding portions can be formed using a 3D printer. In this case, for example, it is preferable to provide alternating protrusions 3 toward the center of the electrode, as shown in Figure 3. The projection does not necessarily have to extend along the entire length of the tube; it may be limited to a certain range from the tip. The shape of the projection is not particularly limited. For example, as shown in Figures 1(a) to (c), it may be a sector shape, a part of a sphere, a triangular pyramidal shape, or a rectangular prism, or a combination of multiple shapes. In addition to the above configuration, the electrode for die-sinking electrical discharge machining of the present invention may be configured such that the plurality of protrusions are located on any straight line connecting the two ends of the cylinder in parallel. With this configuration, as the electrical discharge machining progresses and the electrode penetrates to a certain depth, the workpiece at all positions within the electrode contour is subjected to electrical discharge machining, so that no core remains even while the machining fluid is passing through. Furthermore, the electrode for die-sinking electrical discharge machining of the present invention has an electrode section in which a plurality of protrusions are provided inside the cylindrical outer section, which are not uniform in the longitudinal direction of the cylinder. The plurality of protrusions may have a through-confirmation section 8 with a width less than or equal to the discharge gap, through which light passes linearly from one end of the cylinder to the other, and may also be provided on any straight line connecting the other two ends of the cylinder in parallel. By having this through-confirmation section 8, it is possible to check visually whether there is a gap for the processing fluid to pass through without destructive testing or testing by flowing liquids, gases, etc. through the electrode section. This configuration allows for easy and time-saving confirmation when there are multiple holes or when the shape makes it difficult for liquids or gases to pass through, by shining light from the opposite end of the electrode. In particular, when manufacturing the electrode section by additive manufacturing, it is effective in checking whether any remaining powder from the manufacturing process is present inside the cylinder. An example of the shape is shown in Figure 4. In this example, there is a notch 4 at the center of the circle of the semi-disc-shaped protrusion 3, through which a thin beam of light passes from the top to the bottom of the drawing. The part through which this light passes is the penetration confirmation section 8. The penetration confirmation part 8 may be provided parallel to the length direction of the electrode part, or it may not be. When provided in parallel, electrical discharge machining cannot be performed on the workpiece corresponding to that part. However, by making the penetration confirmation part 8 equal to or less than the width of the discharge gap, visual confirmation can be performed before use, and electrical discharge machining can be performed so that no core remains. When the penetration confirmation part 8 is not provided parallel to the length direction, machining can be performed without leaving a core regardless of the width of the discharge gap. The width of the discharge gap varies depending on the electrode, workpiece, and machining conditions, but generally it is 0.01 - 0.2 mm. Therefore, it is preferable that the size of the penetration confirmation part 8 in the cross-sectional direction of the electrode part is also equal to or less than this width.

Example

[0009] (Example 1) As the electrode part, a copper square pipe with a length of 30 mm, an outer dimension of 2 × 2 mm, and an inner dimension of 1.5 mm × 1.5 mm was prepared. Separately, a plurality of copper square bars with a length of 3 mm and a side length of 1 mm were prepared. After applying a surface coating type solder, a plurality of them were adhered to random positions on the inner diameter side of the copper square pipe, and soldering was performed as it was. A schematic diagram of the electrode part is shown in FIG. 5. When observed after soldering, light did not pass through any point at the end from the end of the square pipe to the opposite side. Also, when air was blown from the end, air flow was confirmed from the opposite side. Therefore, this electrode has a configuration in which a plurality of protruding parts 2 that are not uniform in the length direction of the cylinder are provided inside the cylindrical outer cylinder part. This electrode part was set as it was in an electrical discharge machining machine, and cemented carbide was machined while injecting machining fluid from the inner diameter side. As a result, the machining fluid flowed through the cylinder without problems, and machining could be performed at a speed about 2.5 times that when the same machining was performed using a square bar with a length of 30 mm and 2 × 2 mm. Also, no core of the workpiece occurred during and after machining.

[0010] (Example 2) As the electrode section, an electrode was 3D printed with a copper pipe measuring 30 mm in length, 2 mm in outer diameter, and 1 mm in inner diameter. Semicircular protrusions with a diameter of 1 mm were arranged alternately along the length of the pipe's inner diameter. Each semicircular protrusion had a 0.05 mm semicircular notch 4 at its center (Figure 4). This section served as a through-hole confirmation section 8, and it was easily confirmed that a thin beam of light could pass through the through-hole confirmation section 8 from the end of the electrode to the opposite end. A single-piece electrode 1 for die-sinking electrical discharge machining (EDM) with two of these electrode sections was fabricated. When this EDM electrode 1 was set in an EDM machine and cemented carbide was machined while suctioning the machining fluid from the inner diameter side, the machining fluid passed through the pipe without issue, and two holes could be machined simultaneously at a speed equivalent to that of a typical coreless electrode 6. Furthermore, no core formation occurred in the workpiece during or after machining. [Explanation of symbols]

[0011] 1 Electrode for die-sinker electrical discharge machining 2 Protrusion 3. Semi-circular projection 4 Notches 5. Pipe-shaped electrodes 6 Coreless electrodes 7 Joint surface 8 Penetration confirmation section

Claims

1. Inside the cylindrical outer section, The electrode portion has multiple protrusions that are not uniform along the length of the cylinder, The aforementioned multiple protrusions are located on any straight line that parallel to the ends of the cylinder. Electrode for die-sinker electrical discharge machining.

2. Inside the cylindrical outer part, The electrode portion has multiple protrusions that are not uniform along the length of the cylinder, The aforementioned multiple protrusions are, Light is passed in a straight line from one end of the tube to the other. It has a through-hole confirmation section whose width is less than or equal to the discharge gap, It is located on any straight line that runs parallel to the other ends of the cylinder. Electrode for die-sinker electrical discharge machining.

3. An electrode for die-sinking electrical discharge machining having a plurality of electrode portions as described in Claim 1 or Claim 2.

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