Electric discharge machining method
By using the conductive member as the discharge electrode, the method accelerates the die sinking electric discharge machining process, reducing costs and ensuring precise shape matching in mold production.
Patent Information
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- SUMIDA CORP
- Filing Date
- 2024-12-25
- Publication Date
- 2026-07-02
AI Technical Summary
Conventional die sinking electric discharge machining methods for molds take a long time to design and process the discharge electrode shape, leading to increased manufacturing costs.
The method involves using the conductive member itself as the discharge electrode for die-sinking electric discharge machining, reducing processing time and costs by directly machining the mold to match the shape of the conductive member.
This approach reduces processing time and manufacturing costs while ensuring precise shape matching between the conductive member and the mold, minimizing gaps and burrs in the integrally molded product.
Smart Images
Figure JP2024045916_02072026_PF_FP_ABST
Abstract
Description
Electric Discharge Machining Method
[0001] The present invention relates to an electric discharge machining method for performing die sinking electric discharge machining on a mold for integrally molding a conductive member and a resin molding material using a die sinking electric discharge machine, for example.
[0002] Conventionally, for example, a mold is used for molding an insert molded product formed by integrating a metal member and a resin molding material. Die sinking electric discharge machining (EDM) is often used for machining the internal shape of such a mold (see Patent Document 1 as an example of EDM). It is known that the die sinking electric discharge machining of an insert molded product is performed in the following steps, for example.
[0003] That is, first, an electrode material for electric discharge machining is selected. Generally, a material with good conductivity such as copper or graphite is selected as the electrode material (Step 1). Next, according to the shape of the metal member of the molded product or the shape of the intermediate product, the shape of the discharge electrode for electric discharge machining is designed using a design tool such as CAD (Step 2). Further, based on the design drawing, the electrode material is processed using a CNC machine or the like to form a discharge electrode. Also, if necessary, the surface of the discharge electrode is finished using polishing means or the like (Step 3). Next, the discharge electrode formed as described above is attached as the discharge electrode of the electric discharge machine, and an electric discharge is generated between the discharge electrode and the workpiece, which is the material of the mold, to remove excess material from the workpiece and form the desired shape of the mold (Step 4).
[0004] The mold formed as described above is combined with the metal member at a predetermined position, the lid is closed, the molten resin material is filled into the mold, and then, after a predetermined cooling period, the lid of the mold is opened, and the integrally molded product of the solidified resin material and the metal member is taken out as a product (Step 5). Here, the region of the metal material incorporated and coated in the mold is formed as a region exposed from the resin molding material when it is made into an integrally molded product. In addition, for the mold body called the master mold, the steps 1 to 4 are often performed using an insert mold in which an insert for fitting parts that require precision and ease of replacement as separate parts is incorporated at a predetermined position.
[0005] Japanese Patent Application Publication No. 5-261621
[0006] However, with conventional technology, the process of forming the shape of the mold, particularly step 2, which involves designing the shape of the discharge electrode for electrical discharge machining, and step 3, which involves processing the electrode material into the electrode shape, takes a long time, which leads to increased manufacturing costs.
[0007] The present invention has been made in view of the above circumstances, and aims to provide an electrical discharge machining method that can reduce processing time and manufacturing costs in the process up to forming the shape of the mold, and that can achieve good shape matching between the conductive member and the mold when forming an integrally molded product.
[0008] The present invention relates to an electrical discharge machining method for machining a mold used for molding an integrally molded product of a conductive member and a molding material containing resin, and is characterized by comprising: a first step of selecting at least a part of a conductive member having the same shape as the conductive member as an electrical discharge machining electrode for a die-sinking electrical discharge machining machine; and a second step of performing die-sinking electrical discharge machining on a predetermined area of the mold using the electrical discharge machining machine so as to conform to the shape of the electrical discharge machining electrode.
[0009] Furthermore, it is preferable that the predetermined region of the mold is the region in the integrally molded product where the conductive member and the molding material are combined. It is also preferable that the predetermined region of the mold covers the region of the conductive member that is exposed from the molding material when the integrally molded product is being formed, so that the exposed region of the conductive member is not in contact with the molding material.
[0010] Furthermore, it is preferable that the conductive member selected as the electrode for electrical discharge machining is made of the same material as the conductive member. It is also preferable that the conductive member contains at least one material from among copper, graphite, tungsten, copper-tungsten alloy, silver-tungsten alloy, tungsten carbide, and molybdenum.
[0011] Furthermore, it is preferable that the molding material containing the resin is made of resin. It is also preferable that the molding material containing the resin is a mixture containing, in addition to the resin, at least one of ceramics, metal powders, and other additive materials. Furthermore, the mold can be an insert mold that is loaded into a master mold.
[0012] According to the electrical discharge machining method of the present invention, a mold used for integral molding of a conductive member and a molding material containing resin is selected as the electrical discharge machining electrode of a die-sinking electrical discharge machining machine, using the conductive member itself as the discharge electrode. Subsequently, a predetermined area of the mold is machined using the electrical discharge machining machine to conform to the shape of the electrical discharge machining electrode. In other words, by performing die-sinking electrical discharge machining using the conductive member itself as the discharge electrode, processing time and manufacturing costs can be reduced in the process up to the formation of the mold shape, and a good match between the shape of the conductive member and the mold can be achieved.
[0013] This is a flowchart showing an electrical discharge machining method according to Embodiment 1 of the present invention. This is a schematic diagram showing a metal member used as a discharge electrode in the electrical discharge machining method according to Embodiment 1 of the present invention. This is a schematic diagram showing the state in which the metal member shown in Figure 2 is installed as a discharge electrode in the electrical discharge machining method according to Embodiment 1. This is a schematic diagram showing the base material of an insert die used in the electrical discharge machining method according to Embodiment 1. This is a schematic diagram showing the process of performing die-sinking electrical discharge machining on the base material of an insert die in the electrical discharge machining method according to Embodiment 1. This is a schematic diagram showing an insert die processed by the electrical discharge machining method according to Embodiment 1. This is a schematic diagram showing the state in which a metal member of the same shape and material as the metal member shown in Figure 2 is fitted into the insert die shown in Figure 6 as a metal member that is an element of an integrally molded product. This is a schematic diagram showing a method for forming an integrally molded product using a die according to Embodiment 1 (First step: state in which the die is about to be closed). This is a schematic diagram showing a method for forming an integrally molded product using a die according to Embodiment 1 (Second step: state in which the die is closed). This is a schematic diagram showing a method for forming an integrally molded product using a mold according to Embodiment 1 (third step: the state in which the mold is opened after molding). This is a schematic diagram showing an integrally molded product formed using a mold according to Embodiment 1. This is a schematic diagram showing a metal member used as a discharge electrode in the electrical discharge machining method according to Embodiment 2 of the present invention. This is a schematic diagram showing the state in which the metal member shown in Figure 12 is installed as a discharge electrode in the electrical discharge machining method according to Embodiment 2. This is a schematic diagram showing the base material of an insert die used in the electrical discharge machining method according to Embodiment 2. This is a schematic diagram showing the process of performing die-sinking electrical discharge machining on the base material of an insert die in the electrical discharge machining method according to Embodiment 2. This is a schematic diagram showing an insert die (lower insert die) processed by the electrical discharge machining method according to Embodiment 2. This is a schematic diagram showing a state in which a metal member of the same shape and material as the metal member shown in Figure 12 is fitted into the insert die (lower insert die) shown in Figure 16 as a metal member that is an element of an integrally molded product. This is a schematic diagram showing a state in which the upper insert die is combined on the lower insert die shown in Figure 17. Figure 18 is a schematic diagram showing how the insert mold is assembled into a predetermined position in the master mold. This is a schematic diagram showing a method for molding an integral molded product using the mold according to Embodiment 2 (First step: the state in which the mold is about to be closed).This is a schematic diagram showing a method for forming an integrally molded product using a mold according to Embodiment 2 (Step 2: Mold closed). This is a schematic diagram showing a method for forming an integrally molded product using a mold according to Embodiment 2 (Step 3: Mold open after molding). This is a schematic diagram showing an integrally molded product formed using the method according to Embodiment 2. This is a schematic diagram showing the process of performing die-sinking electrical discharge machining on the base material of the insert mold in an electrical discharge machining method according to a modified example of Embodiment 2 (Step 1: Insert mold being moved). This is a schematic diagram showing the process of performing die-sinking electrical discharge machining on the base material of the insert mold in an electrical discharge machining method according to a modified example of Embodiment 2 (Step 2: Insert mold after electrical discharge machining has been performed). This is a schematic diagram showing the insert mold (left and right insert molds) processed by the electrical discharge machining method according to a modified example of Embodiment 2. This is a schematic diagram showing a state in which a metal member of the same shape and material as the metal member shown in Figure 24 is fitted into the insert mold (left and right insert molds) shown in Figure 26 as a metal member that is an element of an integrally molded product and assembled. This is a schematic diagram showing how the insert mold shown in Figure 27 is assembled into a predetermined position in the master mold. This is a schematic diagram showing a method for forming an integrally molded product using a mold in an electrical discharge machining method according to a modification of Embodiment 2. This is a schematic diagram showing a metal member used as a discharge electrode in an electrical discharge machining method according to Embodiment 3 of the present invention. This is a schematic diagram showing the state in which the metal member shown in Figure 30 is installed as a discharge electrode (only the left side is shown) in an electrical discharge machining method according to Embodiment 3. This is a schematic diagram showing the base material of the mold used in an electrical discharge machining method according to Embodiment 3. This is a schematic diagram showing how die-sinking electrical discharge machining is performed on the base material of the mold in an electrical discharge machining method according to Embodiment 3. This is a schematic diagram showing a mold processed by an electrical discharge machining method according to Embodiment 3. This is a schematic diagram showing how a metal member of the same shape and material as the metal member shown in Figure 30 is fitted into the mold shown in Figure 34 as a metal member which is an element of an integrally molded product. This is a schematic diagram showing an integrally molded product formed using a mold according to Embodiment 3.
[0014] The following describes the electrical discharge machining methods according to each embodiment of the present invention. First, the concept of the present invention will be briefly explained using the flowchart shown in Figure 1, with Embodiment 1 as a representative example. Therefore, the drawings and reference numerals used in the explanation of each step will be those used in Embodiment 1 for convenience.
[0015] As shown in Figure 1, the electrical discharge machining method according to this embodiment involves selecting one metal material 10 (see Figure 2) from among a plurality of produced metal members 10A (see Figure 11) as the electrical discharge machining electrode, and installing at least a portion of it in the electrode mounting section 40 of the electrical discharge machining machine (not shown; the same applies hereinafter) (see Figure 3) (S1: Selection of electrical discharge electrode). Next, the electrical discharge machining machine is operated, and the electrical discharge machining electrode (metal material 10) is brought close to the base material (see Figure 4) of the insert die 30, and die-sinking electrical discharge machining is performed (see Figure 5) to form a recess 30A in the insert die 30 (see Figure 6) (S2: Die-sinking electrical discharge machining).
[0016] The electrical discharge machining method according to this embodiment is the method represented by step 1 (S1) and step 2 (S2) above. This method is often used as a prerequisite for a method of integrally molding a metal member 10 and a resin molded body material, such as an integrally molded product 90 (see Figure 11), using the insert die 30 formed in step 2 (S2). Therefore, in each of the following embodiments, the integral molding method will be explained as a series of steps, and in the explanation of the flowchart in Figure 1, this integral molding method will be represented as a step that follows the electrical discharge machining method according to this embodiment.
[0017] Specifically, following step 2 (S2) above, a metal member 10A, which is made of the same material and has the same shape as the metal member 10, is fitted into the recess 30A of the insert mold 30 (see Figure 7), and the insert mold 30 combined with the metal member 10A is set into one of the master molds 60 of the insert molding machine (see Figure 8) (S3: setting into the molding machine). Next, the molds of the insert molding machine are closed (the two master molds 60 and 70 are brought together), and the molten resin 81 is injected into the space 70A of the other master mold 70 (see Figure 9). This forms an integral molded product 90 of the resin molded body 81A and the metal member 10A (see Figures 10 and 11) (S4: molding of the integral molded product). The following describes each embodiment in detail.
[0018] [Embodiment 1] This embodiment is an electrical discharge machining method for forming an insert mold for integrally molding an integrally molded product (e.g., a connector) consisting of a metal member 10A (e.g., made of copper) having a linear, elongated shape (rectangular parallelepiped shape) and a resin molded body. The shape of the metal member 10 which serves as the discharge electrode in the electrical discharge machining method according to this embodiment may be the same as the metal member 10A, or it may be the shape obtained when a part of it (the part embedded in the resin molded body 81A of the integrally molded product 90) is cut off as an excess part to be used as an electrical discharge machining electrode. In this embodiment, for the sake of explanation, the metal member 10 will be described as being made of the same material and having the same shape as the metal member 10A. Furthermore, (1) to (4) described below correspond to steps 1 (S1) to 4 (S4) in Figure 1, respectively (the same applies to each embodiment and modification described later).
[0019] The following describes in detail the electrical discharge machining method according to Embodiment 1 (specifically, the die-sinking electrical discharge machining method). (1) First, one of the metal members 10A that are elements of the integrally molded product 90 (see Figure 2) is selected as the discharge electrode of the electrical discharge machining machine.
[0020] (2) Next, the tip portion 10E of the metal member 10 is attached to the electrode mounting jig 50, and the electrode mounting jig 50 is attached to the electrode mounting portion 40 of the electrical discharge machining machine (not shown) (see Figure 3). Specifically, the tip portion 10E of the metal member 10 (the portion embedded in the resin molded body 81A (see Figure 11)) is provided with a fixing portion (not shown) for attaching the metal member 10 to the fixed portion (not shown) of the electrode mounting jig 50. These fixed portion and fixing portion can take various forms, such as screw holes and screws, recesses and protrusions that fit into each other, or rail grooves and protrusions that fit into these grooves. Alternatively, screw holes may be formed in both and the two can be fixed together with separate screws. Furthermore, it is preferable that the electrode mounting jig 50 is made of a material that has high conductivity, high hardness, and good workability, such as copper, tungsten, copper-tungsten alloy, silver-tungsten alloy, tungsten carbide, or molybdenum. Furthermore, it may be made of the same material as the metal member 10.
[0021] By using the electrode mounting jig 50, the inconvenience of physical interference between the electrode mounting portion 40 of the electrical discharge machining machine and the tip portion 10E of the metal member 10 can be avoided, and the electrode mounting portion 40 and the tip portion 10E can be smoothly joined.
[0022] Next, as shown in Figure 4, the insert die (base material) 30, which serves as the workpiece, is subjected to die-sinking electrical discharge machining using the metal member 10 as the discharge electrode, as shown in Figure 3, to process the insert die 30. This electrical discharge machining creates a recess 30A in the insert die 30 that is a transfer of the shape of the metal member 10 used as the discharge electrode. As shown in Figure 5, this processing involves placing the insert die 30 (base material) in an insulating processing fluid 55, such as oil or pure water, lowering the metal member 10 as the discharge electrode into the processing fluid 55, and generating an electrical discharge between the insert die 30 (base material) and the metal member 10, thereby forming a recess 30A in the insert die 30 (base material) that conforms to the shape of the discharge electrode (metal member 10). Performing electrical discharge machining in the processing fluid 55 in this way is to instantly cool the material that becomes hot due to the electrical discharge machining. This makes it possible to form the insert die 30 shown in Figure 6, which has been processed to the desired shape.
[0023] As described above, according to the electrical discharge machining method of this embodiment, the insert mold 30 used for integral molding of the metal member 10 and the molding material including the resin 81 is selected as the discharge electrode of the die-sinking electrical discharge machining machine using the metal member 10 itself as the discharge electrode, and thereafter, the electrical discharge machining machine is used to form a recess 30A in a predetermined area of the insert mold 30 that conforms to the shape of the discharge electrode. In other words, by performing die-sinking electrical discharge machining using a metal member 10 of the same material and shape as the metal member 10A as the discharge electrode, it is possible to reduce processing time and manufacturing costs in the process up to the formation of the shape of the insert mold 30, and it is also possible to achieve good shape matching between the metal member 10A and the insert mold 30.
[0024] (3) After this, as shown in Figure 7, a metal member 10A made of the same material and shape as the metal member 10 used as the discharge electrode is fitted into the recess 30A of the insert mold 30. Since the recess 30A is formed to conform to the outer shape of the metal member 10, when the metal member 10A is fitted in, the inner wall of the recess 30A comes into contact with the outer wall of the metal member 10A without any gaps. As a result, resin does not enter the gap between the two during molding, and there is no risk of unnecessary burrs being formed. After this, the exposed portion 10A1 side of the metal member 10A in the integrally molded product 90 is fitted into the recess 30A of the insert mold 30, and the insert mold 30 is set in a predetermined position in the master mold (movable part of the master mold) 60 for insert molding, and then precise position adjustment is performed (see Figure 8).
[0025] (4) Then, as shown in Figure 9, the insert molding die is closed (the movable part 60 of the master mold is brought into contact with the fixed part 70 of the master mold), and the molten epoxy resin 81 (see Figure 8) is injected from the cylinder 80 into the space 70A of the fixed part 70 of the master mold, and cooled to perform integral molding of the integral molded product 90 shown in Figure 11, which consists of the resin molded body 81A and the metal member 10A (see Figure 9). After this, as shown in Figure 10, the die is opened (the movable part 60 of the master mold is separated from the fixed part 70 of the master mold), and the molded integral molded product 90 is removed.
[0026] In this embodiment, injection molding is used as the resin molding method, but other methods such as blow molding, extrusion molding, vacuum molding, compression molding, and transfer molding can also be used instead.
[0027] The following provides supplementary information about each component used in the electrical discharge machining method according to Embodiment 1. As shown in Figure 2, the metal component 10 and metal component 10A have a rectangular parallelepiped shape and are preferably made of copper due to their high conductivity. However, other conductive materials such as graphite, tungsten, copper-tungsten alloy, silver-tungsten alloy, tungsten carbide, and molybdenum can also be used. Furthermore, the shape of the metal component 10 can be changed from a rectangular parallelepiped to other shapes such as a flat plate.
[0028] Furthermore, in this metal member 10, it is possible to cut off a portion of the tip portion (electrode mounting jig connection side) 10E, taking into consideration the size of the area required for die-sinking electrical discharge machining. Also, if the length or width of the tip portion 10E of the metal member 10 is smaller than the required dimensions, it is possible to join it with other conductive members using methods such as welding to secure the required size.
[0029] Furthermore, the base material of the insert die 30 is subjected to electrical discharge machining. The material used to form the insert die (base material) 30 is preferably one that has sufficient strength to withstand the pressure during molding, excellent durability, and high thermal conductivity. For example, stainless steel or alloy tool steel formed by adding metallic elements such as chromium (Cr), tungsten (W), molybdenum (Mo), and vanadium (V) is preferable, but various other materials can also be used.
[0030] Furthermore, as described above, insert molding resin molding technology is used as a manufacturing method for integrally molded products using insert molds formed by the electrical discharge machining method according to this embodiment. When performing insert molding, as shown in Figure 8, an insert mold 30 shown in Figure 6 is installed at a predetermined position within the master mold 60 for insert molding. This insert mold 30 has a recess 30A formed therein that conforms to the outer shape of the exposed portion 10A1 (see Figure 11) of the metal member 10A in the integrally molded product, and the exposed portion 10A1 side of the metal member 10A is fitted into this recess 30A.
[0031] Furthermore, the resin molded body 81A (see Figure 11), which is integrally molded with the metal member 10A, is formed from a molding material containing resin, and in this embodiment in particular, it is formed solely from epoxy resin, which is a thermosetting resin with high moldability. However, in addition to epoxy resin, it is also possible to use thermosetting resins such as phenolic resin and polyester resin, or a mixture of at least one of thermoplastic resins such as polypropylene (PP), polycarbonate (PC), acrylonitrile butadiene styrene (ABS), polyethylene (PE), and polymethyl methacrylate (PMMA), or elastomer resins such as silicone resin and natural rubber.
[0032] In this embodiment, in the integrally molded product 90 shown in Figure 11, a portion of the metal member 10A is embedded in the resin molded body 81A. Therefore, the portion of the metal member 10A is referred to as the exposed portion 10A1, and the other portion is referred to as the embedded portion 10A2.
[0033] [Embodiment 2] In the electrical discharge machining method according to Embodiment 1, the shape of the metal member 10 is designed to represent a state in which a part of the original metal member has been cut off. However, in the electrical discharge machining method according to Embodiment 2, the shape of the metal member 10 is designed to represent the entire original metal member 10 as an electrical discharge machining electrode. Since this embodiment has parts similar to Embodiment 1, corresponding parts are indicated by adding 100 to the reference numeral of the part used in Embodiment 1, and a detailed explanation of those parts is omitted.
[0034] The following describes in detail the electrical discharge machining method (specifically, the die-sinking electrical discharge machining method) according to this embodiment. (1) First, one metal member 110 (see Figure 12) from among the metal members 110A, which are elements of the integrally molded product 190, is selected as the discharge electrode of the electrical discharge machining machine. Next, the tip portion 110E of the metal member 110 (the portion embedded in the resin molded body 181A (see Figure 23)) is attached to the electrode mounting jig 150, and the electrode mounting jig 150 is attached to the electrode mounting section 140 of the electrical discharge machining machine (see Figure 13). Specifically, the tip portion 110E of the metal member 110 is provided with a fixing portion (not shown) for attaching the metal member 110 to the fixed portion (not shown) of the electrode mounting jig 150. The configuration of these fixed portion and fixing portion is the same as in Embodiment 1. The material used to form the electrode mounting jig 150 is also the same as in Embodiment 1. Furthermore, similar to Embodiment 1, the electrode mounting jig 150 allows for smooth connection between the electrode mounting section 140 of the electrical discharge machining machine and the tip section 110E of the metal member 110.
[0035] (2) Next, prepare the insert mold (base material) 130 (collectively referred to as 130a and 130b) as a workpiece, as shown in Figure 14. This insert mold (base material) 130 consists of an upper insert mold 130a and a lower insert mold 130b, and the die-sinking electrical discharge machining is performed on the lower insert mold 130b.
[0036] Next, using the metal member 110 as the discharge electrode, die-sinking electrical discharge machining is performed using an electrical discharge machining machine to process the lower insert die 130b. This electrical discharge machining creates a stepped recess 130bA in the lower insert die 130b, which is a transfer of the outer shape of the metal member 110 used as the discharge electrode. As shown in Figure 15, in order to enhance the cooling effect, the lower insert die 130b (base material) is placed in an insulating machining fluid 155, such as oil or pure water, and the metal member 110, which serves as the discharge electrode, is lowered into the machining fluid. By generating an electrical discharge between the lower insert die 130b (base material) and the metal member 110, a recess 130bA is formed in the lower insert die 130b (base material) that conforms to the outer shape of the metal member 110, which is the discharge electrode.
[0037] This makes it possible to form the lower insert die 130b, as shown in Figure 16, which has been processed to the desired shape. Thus, according to the electrical discharge machining method of this embodiment, by using a metal member 110 of the same material and shape as the metal member 110 as the discharge electrode and performing die-sinking electrical discharge machining, it is possible to reduce processing time and manufacturing costs in the process up to forming the shapes of the insert dies 130a and 130b, and to achieve good shape matching between the metal member 110A and the insert dies 130a and 130b (especially the lower insert die 130b).
[0038] (3) Next, as shown in Figure 17, a metal member 110A made of the same material and shape as the metal member 110 used for the discharge electrode is fitted into the recess 130bA of the lower insert mold 130b which has been subjected to die-sinking electrical discharge machining, and the upper insert mold 130a is then placed on top of it to combine them. Since the recess 130bA is formed to conform to the outer shape of the metal member 110, when the metal member 110A is fitted, the inner wall of the recess 130bA comes into contact with the outer wall of the metal member 110A without any gaps. As a result, resin does not get into the gap between the two during molding, and there is no risk of unwanted burrs being formed.
[0039] As described above, when the upper insert mold 130a is placed over the lower insert mold 130b to combine the upper and lower insert molds 130a and 130b, the protrusion 130aA that extends downward from the upper insert mold 130a is fitted into the recess 130bA of the lower insert mold 130b. As shown in Figure 17, etc., this metal member 110A has a roughly crank shape and is equipped with a roughly parallel upward extension portion 110Au and a downward extension portion 110Ad, and a connecting portion 110Ac that connects these two and is almost perpendicular to them. When the upper and lower insert molds 130a and 130b are combined with each other, the side surface of the protrusion 130aA is positioned to abut against the connecting portion 110Ac of the metal member 110A, and the bottom surface of the protrusion 130aA is positioned to abut against the upper surface of the downward extension portion 110Ad of the metal member 110A. As a result, when the upper and lower insert molds 130a and 130b are combined, the metal member 110A has a portion of its upper extension 110Au exposed to the outside, while the other portion is fixed and housed within the recess 130bA of the lower insert mold 130b (see Figure 18).
[0040] Next, as shown in Figure 19, the upper and lower insert molds 130a and 130b are inserted into a predetermined position in the master mold 160 while combined with each other. After setting them in the master mold 160 for insert molding, precise position adjustment is performed (see Figure 18). The master mold 160 consists of an upper mold 160a and a lower mold 160b, and the upper mold 160a and lower mold 160b are separable to facilitate the removal of the formed integral molded product 190 (see Figure 23). However, if it is easy to remove the upper and lower insert molds 130a and 130b from the master mold 160 while combined with each other, the master mold 160 does not need to be separable into an upper mold 160a and a lower mold 160b.
[0041] (4) After this, as shown in Figure 20, the movable part 160 of the master mold to which the insert molds 130 (130a, 130b) are attached is moved toward the fixed part 170 of the master mold to close the insert molding mold (the movable part 160 of the master mold to butt with the fixed part 170 of the master mold). Then, the molten epoxy resin or the like 181 is injected from the cylinder 180 into the space 170A of the fixed part 170 of the master mold, and cooled to perform integral molding of the integral molded product 190 shown in Figure 23, which consists of the resin molded body 181A and the metal member 110A (see Figure 21). After this, as shown in Figure 22, the mold is opened (the movable part 160 of the master mold to separate from the fixed part 170 of the master mold), and the molded integral molded product (connector product) 190 is removed. In this embodiment, injection molding is used as the resin molding method, but as with Embodiment 1, other methods such as blow molding, extrusion molding, vacuum molding, compression molding, and transfer molding can also be used instead.
[0042] The following provides supplementary information about each component used in the electrical discharge machining method according to Embodiment 2. As shown in Figure 12, the metal member 110 has a substantially crank shape and includes a substantially parallel upward extension portion 110u and a downward extension portion 110d, and a connecting portion 110c that connects these two portions and is substantially perpendicular to them. The material of the metal member 110 is the same as that of Embodiment 1. As with Embodiment 1, the shape of the metal member 110 can be various other shapes.
[0043] In addition, die sinking electrical discharge machining is performed on the base material of the nested mold 130 (a general term for the upper nested mold 130a and the lower nested mold 130b). As the material for forming this nested mold (base material) 130, various materials similar to those in Embodiment 1 can be used. Thus, also in this embodiment, by performing die sinking electrical discharge machining using the metal member 110 having the same material and the same shape as the metal member 110A, which is an element of the integrally molded product 190 shown in FIG. 23, in the process until the shape of the nested mold 130 (particularly, the lower nested mold 130b) is formed, the processing time and manufacturing cost can be reduced, and the shape matching between the metal member 110A and the nested mold 130 (particularly, the lower nested mold 130b) can be made good.
[0044] Also, similar to Embodiment 1, the resin molded body 181A (see FIG. 23) integrally formed with the metal member 110A is formed from a molding material containing resin. The type of the molding material is the same as that in Embodiment 1. In the integrally molded product 190 shown in FIG. 23 formed according to this embodiment, since a part of the metal member 110A is embedded in the resin molded body 181A, a part of the metal member 110A is referred to as an exposed portion 110A1, and the other part is referred to as an embedded portion 110A2.
[0045] Also, as a manufacturing method of the integrally molded product 190 using the nested mold 130 formed by the electrical discharge machining method according to this embodiment, as described in Embodiment 1, the resin molding technique of insert molding is used. Also, when performing insert molding, it is the same as in Embodiment 1 in that the nested mold 130 (130a, 130b) is installed at a predetermined position in the master mold 160 for insert molding as shown in FIG. 19. However, the metal member 110A used in this embodiment has a crank shape, and after insert molding, similar to the metal member 10A in Embodiment 1, it cannot be removed from the nested mold 130. Therefore, the nested mold 130 is composed of two upper and lower nested molds 130a and 130b so that the integrally molded product 190 can be removed after insert molding.
[0046] That is, as shown in FIG. 15, with the metal member 110 as the discharge electrode, the object of performing die sinking electrical discharge machining is the lower insert die 130b. A concave portion 130bA conforming to the outer shape of the metal member 110 is formed by die sinking electrical discharge machining at a predetermined position of the lower insert die 130b. Then, when performing insert molding, with the metal member 110A fitted into the concave portion 130bA of the lower insert die 130b, the upper insert die 130a is placed thereon and combined. The combined upper and lower insert dies 130a and 130b are installed at a predetermined position of the master die 160 as shown in FIG. 19. In this Embodiment 2, similar to the insert dies 130a and 130b, the master die 160 also consists of an upper master die 160a and a lower master die 160b, and when ejecting the integrally molded product 190, the upper and lower master dies 160a are configured to be separated. However, if the insert dies 130a and 130b can be easily removed from the master die 160 after insert molding, the master die 160 does not necessarily have to be configured to be separated vertically (or horizontally, etc.).
[0047] In particular, in the case of mold products, for example, parts such as motors and actuators, when the shape is complex and there is a need for waterproofing, it is effective to use insert dies.
[0048] [Modification Example of Embodiment 2] In the method according to the above-described Embodiment 2, as described above, the metal member 110A used in this embodiment has a crank shape, and after insert molding, the insert die is configured by two separable upper and lower members 130a and 130b so that the integrally molded product 190 can be ejected. In contrast, this modification example shows an aspect in which the insert die is configured by two left and right members 130a1 and 130b1. Hereinafter, mainly, the differences from the above-described Embodiment 2 will be described.
[0049] That is, the insert dies (base materials) 130a1 and 130b1 as workpieces shown in FIG. 24 consist of a right insert die 130a1 and a left insert die 130b1, and die sinking electrical discharge machining is performed on both the left and right insert dies (base materials) 130a1 and 130b1.
[0050] As both the right-side insert die 130a1 and the left-side insert die 130b1 move closer to the metal member 110 which serves as the discharge electrode, die-sinking electrical discharge machining is performed using an electrical discharge machining machine, and die-sinking electrical discharge machining is applied to the inner walls of both insert die dies 130a1 and 130b1 (see Figures 24 and 25). As a result, each half of the stepped recess 130aA1 and 130bA1, which are a transfer of the outer shape of the metal member 110 which serves as the discharge electrode, is formed on the inner walls of both insert die dies 130a1 and 130b1, respectively (see Figure 26). When these two recesses 130aA1 and 130bA1 are combined, they form a recess 130A1 that is a transfer of the outer shape of the metal member 110. This machining process is performed in an insulating machining fluid, as in Embodiments 1 and 2, in order to enhance the cooling effect.
[0051] Next, metal members 110A, made of the same material and shape as the metal member 110 used as the discharge electrode, are fitted into the recesses 130aA1 and 130bA1 of both insert molds 130a1 and 130b1, respectively, and assembled by sandwiching them between the insert molds 130a1 and 130b1. Since each recess 130aA1 and 130bA1 is formed to conform to the outer shape of the metal member 110, when the metal member 110A is fitted, the inner walls of the recesses 130aA1 and 130bA1 come into contact with the outer wall of the metal member 110A without any gaps. As a result, as in the case of Embodiment 2, resin does not enter the gap between the two during molding, and there is no risk of unwanted burrs being formed.
[0052] Next, as shown in Figure 28, the left and right insert molds 130a1 and 130b1 are combined with the metal member 110A and set in a predetermined position on the master mold 160' for insert molding, after which precise position adjustment is performed. The master mold 160' consists of a right mold 160a1 and a left mold 160b1, and the right mold 160a1 and the left mold 160b1 are separable to facilitate the removal of the formed integral molded product 190 (see Figure 23). However, if it is easy to remove the combined insert molds 130a1 and 130b1 from the master mold 160', the master mold 160' does not need to be separable into the right mold 160a1 and the left mold 160b1.
[0053] After this, similar to Embodiment 2, the movable part 160' of the master mold to which the insert molds 130a and 130b are attached is moved toward the fixed part 170 of the master mold to close the insert molding mold (the movable part 160' of the master mold to butt with the fixed part 170 of the master mold). Then, the molten epoxy resin or the like 181 is injected into the space 170A of the fixed part 170 of the master mold to cool and integrally mold an integral molded product 190 (see Figure 23) similar to Embodiment 2, consisting of the resin molded body resin 181A and the metal member 110A. After this, as shown in Figure 29, the mold is opened (the movable part 160' of the master mold to separate from the fixed part 170 of the master mold) and the molded integral molded product (connector product) 190 is removed.
[0054] [Embodiment 3] In the electrical discharge machining methods according to Embodiments 1 and 2 described above, injection molding is used as the resin molding method, but in this embodiment, transfer molding is used as the resin molding method. Since this embodiment has parts in common with Embodiment 1 described above, corresponding members are indicated by adding 200 to the reference numeral of the member used in Embodiment 1, and a detailed explanation of those parts is omitted.
[0055] The following describes in detail the electrical discharge machining method according to this embodiment. (1) First, one pair of metal members 210a and 210b (see Figure 30) from the metal members 210Aa and 210Ab, which are elements of the integrally molded product 290 (see Figure 36), is selected as the discharge electrodes of the electrical discharge machining machine. Next, the upper ends of the vertically extended portions 210a2 and 210b2 of the metal members 210a and 210b are joined to flat conductive members 220a and 220b using a method such as welding, and these conductive members 220a and 220b are attached to electrode mounting jigs 250a and 250b, and these electrode mounting jigs 250a and 250b are attached to the electrode mounting portions 240a and 240b of the electrical discharge machining machine (not shown) (see Figure 31: only one side of the metal members 210a and 210b is shown).
[0056] Specifically, the conductive members 220a and 220b are provided with fixing parts (not shown) for attaching the metal members 210a and 210b to the fixed parts (not shown) of the electrode mounting jigs 250a and 250b. The configuration of these fixed parts and fixing parts is substantially the same as in embodiments 1 and 2. A chuck or the like may also be used. The material used to form the electrode mounting jigs 250a and 250b is also the same as in embodiments 1 and 2. Furthermore, the use of the electrode mounting jigs 250a and 250b allows for smooth connection between the electrode mounting parts 240a and 240b of the electrical discharge machining machine and the vertically extended parts 210a2 and 210b2 of the metal members 210a and 210b, which is also the same as in embodiments 1 and 2.
[0057] (2) Next, a mold 230 (base material) as a workpiece is prepared as shown in Figure 32. This mold 230 (base material) is subjected to die-sinking electrical discharge machining. The material of the mold 230 (base material) is the same as in Embodiments 1 and 2. That is, using metal members 210a and 210b as discharge electrodes, die-sinking electrical discharge machining is performed using an electrical discharge machining machine to process the mold 230 (base material). Through this electrical discharge machining, recesses 230Aa and 230Ab are formed in the mold 230 (base material) by transferring the outer shapes of the horizontally extended portions 210a1 and 210b1 of the metal members 210a and 210b that were used as discharge electrodes (see Figure 34).
[0058] As shown in Figure 33, this processing is the same as in Embodiments 1 and 2, in that the mold 230 (base material) is placed in an insulating processing fluid 255, such as oil or pure water, to enhance the cooling effect, and electrical discharge machining is performed between it and the metal members 210a and 210b. By generating an electrical discharge between the mold 230 (base material) and the horizontally extended portions 210a1 and 210b1 of the metal members 210a and 210b, recesses 230Aa and 230Ab are formed in the mold 230 (base material) that conform to the outer shapes of the horizontally extended portions 210a1 and 210b1 of the metal members 210a and 210b, which are the discharge electrodes.
[0059] This makes it possible to form a mold 230 as shown in Figure 34, which has been processed to the desired shape. Thus, according to the electrical discharge machining method of this embodiment, by using metal members 210a and 210b of the same material and shape as the metal members 210Aa and 210Ab as discharge electrodes to perform mold-sinking electrical discharge machining, it is possible to reduce processing time and manufacturing costs in the process up to forming the shape of the mold 230, and to achieve good shape matching between the metal members 210Aa and 210Ab and the mold 230.
[0060] (3) Next, as shown in Figure 35, metal members 210Aa and 210Ab, which are made of the same material and have the same shape as the metal members 210a and 210b used as discharge electrodes, are fitted into the recesses 230Aa and 230Ab of the mold 230 which has been subjected to die-sinking electrical discharge machining. Since the recesses 230Aa and 230Ab are formed to conform to the outer shape of the metal members 210a and 210b, when the metal members 210Aa and 210Ab are fitted, the inner walls of the recesses 230Aa and 230Ab come into contact with the outer walls of the metal members 210Aa and 210Ab without any gaps. As a result, resin does not enter the gap between the two during molding, and there is no risk of unwanted burrs being formed.
[0061] (4) Next, the mold 230 is closed (the lid mold, not shown, is opened relative to the mold 230, and the molded integral product (connector product, etc.) 290 (see Figure 36) is removed. In this embodiment, transfer molding is used as the resin molding method, but other methods such as blow molding, extrusion molding, vacuum molding, compression molding, and injection molding can also be used instead.
[0062] The following provides supplementary information about each component used in the electrical discharge machining method according to Embodiment 3. As shown in Figure 30, both metal members 210a and 210b are substantially L-shaped and have substantially orthogonal horizontal extensions 210a1, 210b1 and vertical extensions 210a2, 210b2. In this embodiment, a pair of metal members 210a and 210b are used arranged in a plane-symmetrical manner. However, in modifications of this embodiment, the shapes of the metal members 210a and 210b can be various other shapes. The material of the metal members 210a and 210b is the same as that of Embodiments 1 and 2.
[0063] When installing these metal members 210a and 210b as discharge electrodes in the electrode mounting sections 240a and 240b of the electrical discharge machining machine, the vertical extensions 210a2 and 210b2 of the metal members 210a and 210b are attached to the electrode mounting sections 240a and 240b of the electrical discharge machining machine via electrode mounting jigs 250a and 250b, as shown in Figure 31 (since the installation method for the electrode mounting sections 240a and 240b is the same, only one electrode mounting section 240a is shown in Figure 31). This point is the same as in Embodiments 1 and 2, but in this embodiment, in accordance with the mounting limitations due to the shape of the electrode mounting jig 250a, 250b side portion (vertically extended portion 210a2, 210b2) of the metal members 210a, 210b, it is desirable to join that portion to other conductive members 220a, 220b using a method such as welding, and to connect to the electrode mounting jig 250a, 250b via these other conductive members 220a, 220b.
[0064] After this, the base material of the mold 230, schematically shown in Figure 32, is subjected to electrical discharge machining. However, as with embodiments 1 and 2, various materials can be used to form this mold (base material) 230. In this embodiment, unlike embodiments 1 and 2, the mold 230 is used as a regular mold (master mold) rather than an insert mold, but this does not preclude its use as an insert mold, as with embodiments 1 and 2.
[0065] Furthermore, similar to embodiments 1 and 2, the resin molded body 281A (see Figure 36), which is integrally molded with the metal members 210Aa and 210Ab, is formed from a molding material containing resin. The type of molding material is the same as in embodiments 1 and 2. In the integrally molded product 290 shown in Figure 36, which is formed according to this embodiment, a portion of the metal members 210Aa and 210Ab, which are made of the same material and have the same shape as the metal members 210a and 210b, is embedded in the resin molded body 281A. Therefore, a portion of the horizontally extended portions 210Aa1 and 210Ab1 of the metal members 210Aa and 210Ab is exposed, while the other portions of the horizontally extended portions 210Aa1 and 210Ab1 and the vertically extended portions 210Aa2 and 210Ab2 are embedded. Thus, while exposing a portion of the horizontally extended sections 210Aa1 and 210Ab1 has the advantage of reducing the height of the integrally molded product 290, it is of course also possible to expose all of the horizontally extended sections 210Aa1 and 210Ab1.
[0066] Furthermore, as a manufacturing method for the integrally molded product 290 using the mold 230 formed by the electrical discharge machining method according to this embodiment, insert molding resin molding technology is used, as described in Embodiments 1 and 2. That is, as shown in Figure 35, metal members 210Aa and 210Ab, which are of the same material and shape as the metal members 210a and 210b, are fitted into recesses 230Aa and 230Ab (see Figure 34) formed by the above-described die-sinking electrical discharge machining. Since these recesses 230Aa and 230Ab are formed to conform to the outer shape of the horizontally extended portions 210a1 and 210b1 of the metal members 210a and 210b, which are of the same material and shape as the metal members 210Aa and 210Ab, the horizontally extended portions 210Aa1 and 210Ab1 of the metal members 210Aa and 210Ab can be fitted into these recesses 230Aa and 230Ab without any gaps.
[0067] As shown in Figure 35, the metal members 210Aa and 210Ab are fitted into predetermined positions in a mold 230 into which the aforementioned transfer molding is performed, and finally, the integrally molded product (e.g., a connector product) 290 shown in Figure 36 is obtained. That is, this integrally molded product 290 is exemplified as a large inductor component in which a core 291 and a coil 292 are embedded in a resin molded body 281A, in addition to embedded portions including the vertically extended portions 210Aa2 and 210Ab2 of the metal members 210Aa and 210Ab, and both ends 293 of the coil 292 are connected to terminal portions 294 of the vertically extended portions 210Aa2 and 210Ab2 of the metal members 210Aa and 210Ab, respectively. In the above embodiment 3, a portion of the horizontally extended portions 210a1 and 210b1 of the metal members 210a and 210b are exposed from the resin molded body 281A, while the other portions are embedded in the resin molded body 281A. However, in the electrical discharge machining method of the present invention, the shape of the metal members, and the portions embedded and exposed in the resin molded body 281A, can be appropriately selected according to the application. For example, the vertically extended portions 210a2 and 210b2 of the metal members 210a and 210b (for example, other portions connected to the vertically extended portions 210a2 and 210b2) may be exposed from the resin molded body, while the horizontally extended portions 210a1 and 210b1 may be embedded in the resin molded body 281A.
[0068] Furthermore, the integrally molded product 290 to be formed can be a case or cover for components such as large inductor parts, reactors, transformers, and capacitors, as well as electronic components equipped with discharge electrodes. In order to reduce the height of the final product, as mentioned above, it is essential to make the depth of the recesses 230Aa and 230Ab smaller than the thickness of the horizontally extended portions 210Aa1 and 210Ab1 of the metal members 210Aa and 210Ab.
[0069] (Modified Embodiments) The electrical discharge machining method of the present invention is not limited to the embodiments described above, and various other modifications are possible. For example, in each of the embodiments described above, a metal material is used as the conductive member, but the conductive member according to the present invention is not limited to a metal material, and it is also possible to use a substance other than metal with high conductivity, such as graphite or a compound of metal and carbon. Furthermore, the shape of the conductive member and the shape of the mold are not limited to those used in each of the embodiments described above, and various shapes can be used depending on the purpose of the integrally molded product. In addition, in the embodiments described above, a conductive member of the same shape and material as the conductive member that is an element of the integrally molded product is used as the electrode for electrical discharge machining, but as long as they have the same shape, the material of the conductive member does not necessarily have to be the same.
[0070] Furthermore, the molding in Embodiments 1 and 2 described above is performed using an insert mold and a master mold, while the molding in Embodiment 3 is performed using a conventional mold without an insert mold; however, these can be reversed. Also, the molding in Embodiments 1 and 2 described above is performed using injection molding, while the molding in Embodiment 3 is performed using transfer molding; however, the molding methods are not limited to these embodiments, and other molding methods can also be used.
[0071] (Scope of Application) In the embodiments described above, the electrical discharge machining method of the present invention is stated to be applicable to the manufacture of connectors, motors, actuators, or inductor components, but it can also be applied to the manufacture of automotive parts such as engine covers and bumpers, casings for electronic devices such as laptops and smartphones, components used inside home appliances, and medical devices such as surgical instruments, endoscopes, and artificial joints.
[0072] 10, 110, 210a, 210b Metal components (for discharge electrodes) 10A, 110A, 210Aa, 210Ab Metal components (for integrally molded parts) 10A1, 110A1, 110A2, 210Aa1, 210Ab1 Exposed parts 10A2, 110A2, 210Aa2, 210Ab2 Embedded parts 10E, 110E Tip parts 30, 130 Insert molds 30A, 130bA, 130A1, 130aA1, 130bA1, 230Aa, 230Ab Recessed parts 40, 140, 240a, 240b Electrode mounting parts 50, 150, 250a, 250b Electrode mounting jigs 55, 155, 255 Processing fluid 60, 160: Movable part of the master mold; 70, 170: Fixed part of the master mold; 70A, 170A: Space; 81, 181: Resin; 81A, 181A, 281A: Resin molded body; 90, 190, 290: One-piece molded product; 110u: Upper extension part (for discharge electrode); 110d: Lower extension part (for discharge electrode); 110c: Connecting part (for discharge electrode); 110Au: Upper extension part (for one-piece molded product part); 110Ad: Lower extension part (for one-piece molded product part); 110Ac: Connecting part (for one-piece molded product part); 130a: Upper insert mold (base material); 130b: Lower insert mold (base material); 130aA: Convex part; 130a1: Right insert mold; 130b1: Left insert mold; 160a Master mold (upper mold) 160b Master mold (lower mold) 160a1 Master mold (right mold) 160b1 Master mold (left mold) 210a1, 210b1 Horizontal extension section (for discharge electrode) 210a2, 210b2 Vertical extension section (for discharge electrode) 210Aa1, 210Ab1 Horizontal extension section (for integral molded part) 210Aa2, 210Ab2 Vertical extension section (for integral molded part) 220a, 220b Other conductive members 230 Mold 291 Core 292 Coil 293 Both ends 294 Terminal section
Claims
1. An electrical discharge machining method for processing a mold used for molding an integrally molded product of a conductive member and a molding material containing resin, comprising: a first step of selecting at least a portion of a conductive member having the same shape as the conductive member as an electrical discharge machining electrode for a die-sinking electrical discharge machining machine; and a second step of performing die-sinking electrical discharge machining on a predetermined area of the mold using the electrical discharge machining machine so as to conform to the shape of the electrical discharge machining electrode.
2. The electrical discharge machining method according to claim 1, characterized in that the predetermined region of the mold is a region in the integrally molded product in which the conductive member and the molding material are combined.
3. The electrical discharge machining method according to claim 2, characterized in that the predetermined region of the mold covers the region of the conductive member that is exposed from the molding material when the integral molding of the integrally molded product is performed, thereby keeping the exposed region of the conductive member in a non-contact state with the molding material.
4. The electrical discharge machining method according to claim 1, characterized in that the conductive member selected as the electrode for electrical discharge machining is made of the same material as the conductive member.
5. The electrical discharge machining method according to claim 1, characterized in that the conductive member includes at least one material selected from copper, graphite, tungsten, copper-tungsten alloy, silver-tungsten alloy, tungsten carbide, and molybdenum.
6. The electrical discharge machining method according to claim 1, characterized in that the molding material containing the resin is made of resin.
7. The electrical discharge machining method according to claim 1, characterized in that the molding material containing the resin is a mixture containing, in addition to the resin, at least one material from among ceramics, metal powders, and other additive materials.
8. The electrical discharge machining method according to any one of claims 1 to 7, characterized in that the mold is an insert mold loaded into a master mold.