A combined electrode for electric discharge machining of internal and external splines, its manufacturing method and application

Abstract

The present invention provides a combined electrode for electric discharge machining of internal and external splines, which includes an electrode mounting rod, an electrode positioning mandrel, a cylindrical electrode and a locking electrode setscrew. The electrode positioning mandrel is detachably fixed in the central hole of the electrode mounting rod. The cylindrical electrode is inserted into the radial electrode mounting hole on the electrode mounting rod, and its machining end forms an envelope circle for machining the spline outside or inside the central hole. The cylindrical electrode is fixed through an axial screw hole on the end face of the electrode mounting rod. Its manufacturing method includes manufacturing its various parts, assembling and in-machine finishing steps. The present invention also provides the application of this combined electrode, that is, a method for machining internal and external splines. The manufacturing method in the present invention can manufacture the combined electrode with high precision. The structure of this combined electrode is simple, but when used to machine internal and external splines, high precision can be obtained. For the worn cylindrical electrode, it can be conveniently replaced and reused, effectively reducing costs, and is suitable for machining internal and external splines of various shapes.

Description

Technical Field

[0001] The present invention belongs to the technical field of electric machining, and relates to a manufacturing method of a combined electrode for electric discharge machining of internal and external splines; the present invention also provides a combined electrode manufactured by this manufacturing method, and also relates to the application of machining internal and external splines using the combined electrode manufactured by the present invention. The present invention is applicable to the electric discharge machining of internal and external splines with different dimensional requirements for shaft-type and hole-type parts. Background Art

[0002] Shafts and holes are indispensable components in machinery. Usually, when mechanical transmission is involved, spline structures need to be designed and machined on shafts and holes. Spline structures are divided into types such as rectangular splines, triangular splines, and involute splines, etc. Rectangular splines are the most widely used, such as in aircraft, automobiles, machine tool manufacturing, agricultural machinery, and general mechanical transmission devices, etc. For the general manufacturing method of external splines, milling or broaching is mainly used for single-piece or small-batch production, and broaching is mainly used for mass production. Machining internal splines is not as easy as machining external splines. Especially, machining blind-hole internal splines is more difficult. Due to the size limitation inside the blind hole, the radial dimension of the broach is limited, and the axial dimension is relatively long. The slender broach has poor rigidity. During broaching, the broach is prone to elastic deformation, and only by repeatedly making small radial feeds with a small broaching amount can the forming cutting be completed. Due to the limitation of the tool structure in broaching manufacturing, problems such as low machining efficiency, difficulty in achieving technical requirements for machining accuracy and surface roughness of spline tooth surfaces occur. With the development of industrial technology, the working conditions requirements for mechanical transmission components are becoming more and more complex. New changes such as various structural forms and dimensional changes, and increasing material hardness, etc., make good machining accuracy, fast delivery, high machining cost performance, and good reparability become the common focus goals.

[0003] A rectangular spline generally has multiple rectangular key grooves machined on the surface of a shaft and a hole and key grooves with corresponding shapes. A rectangular spline is a spline in which the two side surfaces of the key teeth are two planes parallel to the radial plane passing through the axis. Figure 1 and Figure 2 as well as Figure 3 and Figure 4 respectively give part examples of the rectangular spline structures on the inner surface and the outer surface. The characteristics of rectangular splines are: multiple teeth work, high load-bearing capacity, good centering property, good guiding property, relatively shallow tooth roots, small stress concentration, and small weakening of the strength of the shaft and the hub; in addition, in order to reduce wear and improve service life, materials with relatively high hardness or materials with increased hardness through heat treatment are mostly used.

[0004] The electric discharge machining method does not use ordinary tools to cut the workpiece material, nor does it require obvious mechanical force to be applied during the machining process. Instead, electrical energy, thermal energy, and other energies are directly applied to the machined part, so as to achieve a machining method of material removal and meet the required shape, size, and surface quality requirements. Therefore, the electric discharge machining technology has the following characteristics:

[0005] ⑴ "Overcoming the hard with the soft". During machining, the tool electrode does not contact the workpiece material, and there is basically no macroscopic mechanical force between the two electrodes. Therefore, a "soft" tool electrode can be used to machine a "hard" workpiece.

[0006] ⑵ "Precise and micro-fine". Since the energy density of pulsed discharge can be precisely controlled and there is no macroscopic mechanical force between the two electrodes, precise machining with a low surface roughness value and high dimensional accuracy can be achieved.

[0007] ⑶ "True contour replication". The forming tool electrode is directly used for machining, and its shape is replicated on the workpiece. At the same time, complex multi-dimensional curved surface workpieces can be machined with a simple feeding motion. The application of modern computer technology makes the contour replication of machined workpieces more realistic.

[0008] In summary, among numerous machining process technologies, the use of electrical discharge machining technology can not only conveniently machine rectangular splines with diverse structural forms, wide dimensional ranges, and high material hardness, but also meet the requirements of high dimensional accuracy, geometric tolerance, and surface roughness.

[0009] However, in the existing technology of electrical discharge machining, especially in the machining of internal splines, there are still problems with the tool electrodes and machining methods used. One existing technology solution is to first manufacture an external spline-shaped electrode corresponding to the shape of the internal spline hole to be machined, and use this electrode to machine the internal spline by feeding along the axial direction of the blank. The problem with this solution is that for splines of different specifications and dimensions, different specifications and dimensions of tool electrodes need to be manufactured. Another existing technology solution is to use a wire electrode for machining. During machining, first, the spline shape is drawn on the end face of the blank, then an axial through-hole is drilled on the trajectory of the spline shape, the wire electrode is passed through this through-hole, and then under the programmed wire cutting process, the wire electrode cuts along the trajectory of the spline shape. This solution requires programming the wire cutting process, which is complex. During the entire machining process, a single wire electrode cuts the entire material that matches the shape of the internal spline along the axial direction. The machining process of this method is slow, with low efficiency and high cost.

[0010] How to ensure both the machining accuracy and efficiency and be able to adapt to machining splines of various specifications and dimensions is an urgent problem to be solved in the existing technology. Summary of the Invention

[0011] The purpose of the present invention is to solve the problems of the existing technology, provide a method for manufacturing a combined electrode for electrical discharge machining of internal and external splines, and another purpose is to provide a combined electrode manufactured by the said manufacturing method. The combined electrode manufactured by the said method can machine internal and external splines of various specifications and dimensions with high precision and high efficiency.

[0012] Another object of the present invention is to provide a method for machining internal and external splines using the combination electrode.

[0013] The object of the present invention is achieved as follows:

[0014] A method for manufacturing a combination electrode for EDM machining of internal and external splines is as follows:

[0015] Step 1: Manufacture each component of the combination electrode

[0016] A. Machine the electrode mounting rod: Machine the electrode mounting rod from a cylindrical bar stock. One end thereof is made into a connection end for connecting to the machine tool spindle, and the other end is made into an electrode connection end. That is, an axial central hole is made on the end face of the electrode connection end, a connection structure is machined on the bottom surface of the central hole, and a plurality of radial through holes are circumferentially distributed on the hole wall near the hole mouth of the central hole to form electrode mounting holes. The lower part of the electrode mounting hole is a cylindrical wall surface, and the upper part includes two inclined surfaces symmetric with respect to the diameter of the vertical hole perpendicular to the axial direction. A plurality of screw holes are also machined on the end face of the electrode connection end, and each of the screw holes axially communicates with each of the electrode mounting holes respectively;

[0017] B. Machine the cylindrical electrodes: Machine a plurality of cylinders with the same length and diameter, and machine corresponding end heads on one end of each cylinder according to the type and specifications of the internal or external splines to be machined to form electrode machining ends;

[0018] C. Machine the electrode positioning mandrel so that it has such a structure: it has a detachable connection structure matching the connection structure of the electrode mounting rod, so that the electrode positioning mandrel is fixed in the central hole of the electrode mounting rod;

[0019] Step 2: Assemble the combination electrode

[0020] Fix the electrode positioning mandrel in the central hole of the electrode mounting rod through the detachable connection structure on it and the connection structure on the electrode mounting rod;

[0021] Insert the cylindrical electrodes into the electrode mounting holes of the electrode mounting rod, with one end located in the central hole abutted against the electrode positioning mandrel, and then screw in the locking electrode set screws from the screw holes so that each cylindrical electrode abuts against and fits tightly against the upper top surface of the electrode mounting hole formed by the two symmetric inclined surfaces for axial positioning;

[0022] For machining internal splines, the electrode machining ends of each cylindrical electrode are placed outside the central hole, and the other end abuts against the electrode positioning mandrel; or,

[0023] For machining external splines, the electrode machining ends of each cylindrical electrode abut against the electrode positioning mandrel. After fixing the cylindrical electrodes, remove the electrode positioning mandrel from the electrode mounting rod;

[0024] Step 3: In-machine trimming of the combined electrode envelope circle

[0025] For the combined electrode for internal spline machining, make a cylindrical trimming block. Machine an inner hole in the axial direction of the trimming block. The diameter of the inner hole is the envelope circle diameter required for the combined electrode plus a margin. Or, the inner hole size on the trimming block is larger than the shaft diameter of the internal spline positioning mandrel plus twice the length of the cylindrical electrode plus a margin. The height of the inner hole should be greater than the diameter of the cylindrical electrode plus a 2-mm margin. Fix the trimming block on the machine table. Or,

[0026] For the combined electrode for external spline machining, the trimming block is a cylinder. The outer diameter of the cylinder is less than the envelope circle diameter required for the combined electrode plus a margin. Or, the outer diameter of the trimming block is the shaft diameter of the external spline positioning mandrel minus a margin;

[0027] Fix the trimming block on the working table of the machine,

[0028] Fix the combined electrode made in Steps 1 and 2 on the main shaft of the machine through the electrode mounting rod and connect it to the power supply. The combined electrode and the axis of the inner hole or cylinder of the trimming block are eccentrically arranged;

[0029] Insert the combined electrode into the inner hole of the trimming block, or insert the hole surrounded by the cylindrical electrodes of the combined electrode onto the cylinder of the trimming block;

[0030] Utilize the in-machine reverse copying function of the electric discharge machining machine to make the trimming block travel along the trajectory of the envelope circle of the combined electrode and perform in-machine trimming on each cylindrical electrode of the combined electrode.

[0031] Preferably, for machining internal splines, the envelope circle diameter of the external machining end of the cylindrical electrode is larger than the root circle diameter of the internal spline teeth, and the difference is 1 - 4 mm. Or, for machining external splines, the envelope circle diameter of the internal machining end of the cylindrical electrode is larger than the tip circle diameter of the external spline teeth, and the difference is 1 - 2 mm; the dimensions of the circumferential surface, cylindricity, and coaxiality meet the design requirements, and the combined electrode of the required dimensions is made.

[0032] Preferably, before Step 1, design a positioning mandrel according to the keyway dimensions of the rectangular spline part, including the depth and width of the keyway, set the shaft diameter of the electrode mounting rod, the size and number of electrode mounting holes, design the cylindrical electrode, and machine and fabricate it.

[0033] Specifically,

[0034] In Step 1,

[0035] Preferably, in the processing electrode mounting rod, the connecting structure on the bottom surface of the central hole can be a threaded hole. Correspondingly, a central hole is axially provided on the electrode positioning mandrel, and the electrode positioning mandrel is fixed in the central hole of the electrode mounting rod by a fixing mandrel screw. This structure is provided for the combined electrode for processing internal splines; or, it can also be a smooth hole, and the smooth hole and the connecting section of the electrode positioning mandrel connected to the electrode mounting rod form an interference fit. This structure is provided for the combined electrode for processing external splines.

[0036] In the processing electrode mounting rod, the electrode mounting holes are at the same horizontal height, and their diameters are larger than the diameter of the cylindrical electrode. The locking electrode setscrew jacks up the cylindrical electrode so that its upper surface presses against the top surface of the electrode mounting hole.

[0037] Preferably, the lower half of the electrode mounting hole is a semi-cylindrical wall surface, and the included angle between the two inclined surfaces in the upper half can be 90°; or, the included angle between the two inclined surfaces in the upper part is 60°, or 120°; after the cylindrical electrode is jacked up, its upper surface abuts against the two inclined surfaces.

[0038] A relief groove is designed between the two inclined surfaces.

[0039] Specifically, the shape of the processing end of the cylindrical electrode matches the corresponding shape of the spline to be processed. It can be a cylindrical shape, corresponding to machining the keyway of a rectangular internal spline; it can also be a frustum shape with a conical surface, corresponding to machining the keyway between two key teeth of a rectangular external spline; it can also be a triangular shape formed by two inclined surfaces symmetrically arranged with respect to the central axis plane of the cylindrical electrode, corresponding to machining a triangular spline, and it can also be an involute shape, corresponding to machining an involute spline.

[0040] Preferably, the aperture of the central hole of the electrode mounting rod and the shaft diameter of the electrode positioning mandrel are in a running fit. More preferably, the shaft tolerance is h6, and the hole tolerance is H7; the coaxiality of the two is controlled within the range of 0.01 - 0.02 mm.

[0041] Preferably, in the processing of the cylindrical electrode, the outer cylindrical surface of the cylindrical electrode is clamped and fixed on the workbench, and the side generatrix and the upper generatrix of the outer cylindrical surface are aligned; specifically, the linearity in two directions is controlled to be ≤0.01 mm / 80 mm; in addition, the surface roughness Ra is 0.8 μm. The perpendicularity between the cut circular section and the cylindrical surface should be ≤0.01 mm.

[0042] In step 3,

[0043] Preferably, the margin between the inner hole or outer diameter of the trimming block and the envelope circle of the combined electrode is 1 - 4 mm, more preferably 1 - 2 mm. More preferably, it is 2 mm.

[0044] Preferably, the trimming block is made of copper-tungsten alloy; and / or, the parallelism of the upper and lower bottom surfaces of the trimming block is ≤0.02 mm; and / or, the cylindricity of the inner hole or cylinder of the trimming block is ≤0.01 mm; and / or, the perpendicularity to the upper plane is ≤0.01 mm.

[0045] A combined electrode for EDM of internal and external splines manufactured by the above method, comprising an electrode mounting rod, an electrode positioning mandrel, cylindrical electrodes, and locking electrode set screws.

[0046] The electrode mounting rod is a rod body. One end of the rod body is provided with a connection end connected to the spindle, and the other end is an electrode connection end. An axial central hole is provided on the end face of the electrode connection end. A connection structure is provided on the bottom surface of the central hole. On the hole wall of the central hole near the hole mouth, several radial electrode mounting holes are circumferentially distributed. The lower part of the electrode mounting hole is a cylindrical wall surface, and the upper part includes two inclined surfaces symmetrically arranged with respect to the diameter of the vertical hole perpendicular to the axis to form an upper top surface. On the end face of the electrode connection end where the central hole is provided, several screw holes are also provided, and each of the screw holes is axially parallel to and respectively communicates with each of the electrode perforations.

[0047] The electrode positioning mandrel is a rod body, which at least includes a section, namely an electrode positioning section, whose diameter is smaller than the diameter of the central hole. The side wall of this section is for the end of the cylindrical electrode installed in the electrode mounting hole of the electrode mounting rod to abut against inside the central hole. A connection part connected to the connection structure of the electrode mounting rod is also provided thereon to form a detachable connection structure.

[0048] There are several cylindrical electrodes. According to the number and orientation of the splines of the machined part, the cylindrical electrodes are respectively inserted into the corresponding electrode mounting holes on the electrode mounting rod. Each cylindrical electrode has a machining end, and the machining end corresponds to the shape and specification of the spline to be machined. The machining end of each cylindrical electrode is outside the central hole of the electrode mounting rod or inside the central hole, and is on the same circumferential locus, i.e., the envelope circle. The end inside the central hole abuts against the side wall of the electrode positioning section of the electrode positioning mandrel, or abuts against the positioning of the electrode positioning mandrel before completing step 2.

[0049] The locking electrode set screw is inserted into the screw hole, so that the cylindrical electrode provided in the electrode perforation abuts against the upper top surface of the electrode mounting hole and is fixed.

[0050] When machining internal splines, the machining ends of the cylindrical electrodes outside the central hole of the electrode mounting rod are on the same circumferential locus, i.e., the envelope circle; or

[0051] When machining external splines, the machining ends of the cylindrical electrodes inside the central hole of the electrode mounting rod are on the same circumferential locus, i.e., the envelope circle.

[0052] Preferably, for machining internal splines, the electrode positioning mandrel is an internal spline positioning mandrel, whose diameter matches the central hole of the electrode mounting rod. The detachable connection structure is as follows: The internal spline positioning mandrel is provided with a central bolt hole along the axial direction to form the connection structure with the electrode mounting rod. Correspondingly, the connection structure provided on the bottom surface of the central hole of the electrode mounting rod is an axial central screw hole. The internal spline positioning mandrel is fixed in the central hole of the electrode mounting rod 1 by a fixing mandrel screw passing through the central bolt hole on the internal spline positioning mandrel and screwing into the central screw hole on the bottom surface of the central hole of the electrode mounting rod.

[0053] Preferably, for machining internal splines, there is a clearance fit between the electrode positioning section of the electrode positioning mandrel and the central hole of the electrode mounting rod. The shaft tolerance is h6, and the hole tolerance is H7; the coaxiality is controlled within the range of 0.01 - 0.02 mm.

[0054] For machining external splines, the electrode positioning mandrel is an external spline positioning mandrel, including an electrode positioning section and a connection section. The diameter of the electrode positioning section thereon is smaller than the aperture of the central hole of the electrode mounting rod, corresponding to the minor diameter d of the external spline. The connection section thereon is a clamping section with a diameter smaller than that of the positioning section. The connection structure on the electrode mounting rod is as follows: An axial light hole is provided at the bottom of the central hole of the electrode mounting rod, and the connection section of the electrode positioning mandrel is arranged in this light hole to form an interference fit.

[0055] Furthermore, the external spline positioning mandrel further includes a handling section connected to the electrode positioning section.

[0056] Preferably, the lower half of the electrode mounting hole is a semi-cylindrical wall surface, and the included angle between the two symmetric inclined planes of the electrode mounting hole is 90°; and / or, the included angle between the two symmetric inclined planes is 60°, or 120°. Furthermore, a rectangular groove is provided between the two inclined planes of the electrode mounting hole.

[0057] Preferably, the shaft diameter tolerance of the cylindrical electrode is h6.

[0058] Preferably, the shape of the machining end of the cylindrical electrode matches the corresponding shape of the spline to be machined. It is cylindrical, corresponding to machining the keyways of rectangular internal splines; or it is a frustum shape with a conical surface, corresponding to machining the keyways between two key teeth of rectangular external splines; or it is a triangular shape composed of two inclined planes symmetrically arranged with respect to the central axis plane of the cylindrical electrode, corresponding to machining triangular splines, or it is an involute shape, corresponding to machining involute splines.

[0059] The application of the combined electrode, that is, for machining the splines of parts, the machining method is as follows:

[0060] Step 1: Install the part blank in the fixture on the machine tool workbench;

[0061] Step 2: In the previous in-machine dressing, the relative position between the combined electrode and the machine tool is determined;

[0062] Step 3: Align the combined electrode fixed on the spindle with the part blank. Using the outer diameter of the electrode mounting rod in the combined electrode and the outer diameter of the part blank, use the center alignment function of the machine tool column to determine the center position of the electrode and the part. Then set the 0-point positions of the X coordinate and the Y coordinate. Next, use the lower end face of the cylindrical electrode on the combined electrode and the upper end face of the part, and use the end face alignment function of the machine tool to determine the 0-point position of the Z axis of the electrode and the part, and use this position as the starting position of the program machining;

[0063] Step 4: According to the keyway dimensions of the internal and external spline parts of the rectangular spline, determine the electrical parameters for machining steel with a copper electrode, including pulse width, pulse interval, peak current, and no-load voltage, and non-electrical parameters, including machining depth, polarity, servo speed, and movement direction, and compile a machining program accordingly;

[0064] Step 5: Call the machining program and execute it to complete the machining of the internal or external splines of the part.

[0065] The manufacturing method of the combined electrode for internal and external spline electrical discharge machining provided by the present invention can manufacture the combined electrode with high precision. The manufactured combined electrode has a simple structure, but when used to machine internal and external splines, high precision can be obtained. For the worn cylindrical electrode, it can be conveniently replaced and reused. Through an electrode mounting rod, a certain number of electrode mounting holes are set, and different numbers of cylindrical electrodes can be combined to machine different internal and external spline parts. Also, by machining different shapes and specifications of the cylindrical electrodes, different splines can be machined. The machining method for internal and external splines provided by the present invention further ensures the machining accuracy and convenience of the machined splines.

[0066] The following will describe the present invention in detail with reference to the drawings and embodiments. Brief Description of the Drawings

[0067] Figure 1 is a cross-sectional structure schematic diagram of an internal surface rectangular spline part;

[0068] Figure 2 is Figure 1 a side view structure schematic diagram of;

[0069] Figure 3 is a cross-sectional structure schematic diagram of an external surface rectangular spline part;

[0070] Figure 4 is Figure 3 a side view structure schematic diagram of;

[0071] Figure 5 Schematic structural diagram of the combined electrode for machining the internal surface rectangular spline and the machined part provided by the present invention;

[0072] Figure 6 is Figure 5 A - A sectional structural diagram of;

[0073] Figure 7 is Figure 5 Schematic three - dimensional structural diagram of the combined electrode and the machined part shown;

[0074] Figure 8 is Figure 5 Schematic structural diagram of the internal spline positioning mandrel in the combined electrode shown;

[0075] Figure 9 is Figure 5 Schematic structural diagram of the electrode mounting rod in the combined electrode shown;

[0076] Figure 10 is Figure 9 A - A sectional structural diagram of;

[0077] Figure 11 is Figure 9 Top - view structural diagram of;

[0078] Figure 12 is Figure 9 Detail I of, showing the structural diagram of the 90° electrode mounting hole on the electrode mounting rod;

[0079] Figure 13 Schematic structural diagram of the 60° electrode mounting hole on the electrode mounting rod;

[0080] Figure 13a Schematic structural diagram of the 120° electrode mounting hole on the electrode mounting rod;

[0081] Figure 14 is Figure 5 Schematic structural diagram of the cylindrical electrode in the combined electrode shown;

[0082] Figure 15 is Figure 14 Side - view structural diagram of;

[0083] Figure 16 Schematic structural diagram of the combined electrode for machining the internal surface rectangular spline;

[0084] Figure 17 is Figure 16 A - A sectional structural diagram of;

[0085] Figure 18Schematic diagram of the installation positions of the components of the combined electrode for machining the inner surface rectangular spline on the machine tool;

[0086] Figure 19 Schematic structural diagram of the combined electrode for machining the outer surface rectangular spline provided by the present invention;

[0087] Figure 20 For Figure 19 Schematic A-A sectional structure diagram of;

[0088] Figure 21 For Figure 19 Schematic bottom view structure diagram of;

[0089] Figure 22 For Figure 19 Schematic structural diagram of the electrode mounting rod in;

[0090] Figure 23 For Figure 22 Schematic A-A sectional structure diagram of;

[0091] Figure 24 For Figure 22 Part I diagram of, showing the structure of the electrode mounting holes on the electrode mounting rod;

[0092] Figure 25 For Figure 22 Schematic bottom view structure diagram of;

[0093] Figure 26 For Figure 19 Schematic structural diagram of the external spline positioning mandrel in;

[0094] Figure 27 For Figure 19 Schematic structural diagram of the cylindrical electrode in;

[0095] Figure 28 For Figure 27 Schematic right view structure diagram of;

[0096] Figure 29 Schematic structural diagram of the combined electrode for machining the outer rectangular spline;

[0097] Figure 30 For Figure 29 Schematic A-A sectional structure diagram of;

[0098] Figure 31 Schematic diagram of the installation positions of the components of the combined electrode for machining the outer surface rectangular spline on the machine tool during in-machine dressing;

[0099] Figures 32 to 34 Schematic diagram showing the process of the combined electrode machining the outer surface rectangular spline. Detailed implementation manner

[0100] Rectangular splines generally involve machining multiple rectangular keyways of the same size on the outer surface of the shaft or the inner surface of the hole, as Figures 1 to 4 shown. The main parts of such parts that need to be machined include several main dimensions such as the major diameter (also known as the outside diameter) D of the keyway, the minor diameter (also known as the root diameter) d, the width w of the keyway, the depth h of the keyway, the length l of the keyway, and the number n of keyways. The following are the main dimensions and accuracy requirements of the internal and external rectangular splines to be machined in a specific embodiment of the present invention:

[0101] a. Minor diameter d of rectangular spline: φ28mm; internal H5 (0~+0.009), external g5 (-0.007~-0.016);

[0102] b. Major diameter D of rectangular spline: φ32mm; internal H10 (0~+0.1), external a11 (-0.31~-0.47);

[0103] c. Width w of rectangular spline keyway: 6mm; internal H7 (0~+0.012), external f7 (-0.022~-0.010);

[0104] d. Depth h of rectangular spline keyway: 2mm;

[0105] e. Length L of keyway: 20mm;

[0106] f. Number n of keyways: 6;

[0107] g. Surface roughness Ra: ≤1.6μm.

[0108] The tool electrode for machining the above parts is one of the essential tools in electrical discharge machining. A convenient and accurate manufacturing method is very important. Due to the differences in the material, type, geometric shape complexity, and accuracy requirements of the tool electrode, the machining methods of the tool electrode are also different. The most commonly used manufacturing methods of the tool electrode are mechanical machining and wire electrical discharge machining. The structural form of the tool electrode should be determined according to the size, complexity of the spline, and the machining processability of the tool electrode. The tool electrode structure adopted in the present invention is a combined electrode form.

[0109] The structure of a combined electrode for internal spline electrical discharge machining is shown in Figures 5 to 7 , which includes: electrode mounting rod 1, internal spline positioning mandrel 2, cylindrical electrode 3 (φ5.8mm), fixed mandrel screw 4 (hexagon socket head screw M4 with a length of 12mm), and locking electrode setscrew 5 (flat head setscrew M3 with a length of 6mm).

[0110] As Figures 9 to 11 shown, the electrode mounting rod 1 is a rod body, and one end of the rod body is fixed to the electrode fixture 11 on the machine tool spindle 6 (see Figure 18The connecting end of the connection, the other end of which is the electrode connecting end, has an axial central hole on the end face of the electrode connecting end. On the hole wall of the central hole near the hole opening, a number of radial electrode mounting holes are circumferentially distributed. On the end face of the electrode connecting end where the central hole is provided, there are also a number of screw holes, and each of the screw holes is axially communicated with each of the electrode mounting holes respectively.

[0111] As Figure 6 and Figure 8 shown, the electrode positioning mandrel 2 of the internal spline is a cylinder, which is the electrode positioning section. Its diameter forms a clearance fit with the aperture of the central hole on the electrode mounting rod 1. The shaft tolerance is h6, the hole tolerance is H7, and the coaxiality is controlled within the range of 0.01 - 0.02 mm. The internal spline positioning mandrel 2 is provided with a central bolt hole along the axial direction. Correspondingly, an axial central screw hole is provided on the bottom surface of the central hole of the electrode mounting rod 1. The internal spline positioning mandrel 2 is fixed in the central hole of the electrode mounting rod 1 by a fixing mandrel screw 4 passing through the central bolt hole and screwing into the central screw hole.

[0112] As Figure 14 and Figure 15 shown, there are several cylindrical electrodes 3. According to the number and orientation of the splines of the machined part, the cylindrical electrodes 3 are respectively inserted into the corresponding electrode mounting holes on the electrode mounting rod 1, so that the end of each cylindrical electrode 3 outside the central hole of the electrode mounting rod 1, that is, the machining end, is on the same circumferential locus, namely the envelope circle (see Figure 16 and Figure 17 ).

[0113] In this embodiment, there are 6 electrode mounting holes circumferentially distributed on the electrode mounting rod. 2 cylindrical electrodes can be installed in two electrode mounting holes on the same diameter to machine the internal spline with 2 key grooves. Similarly, 3 cylindrical electrodes can be installed at an intersection angle of 120° to machine the internal spline with 3 key grooves, or 6 cylindrical electrodes can be installed in 6 electrode mounting holes to machine the internal spline with 6 key grooves. If there are 8 electrode mounting holes evenly distributed on the electrode mounting rod, the splines with 2 key grooves, 4 key grooves or 8 key grooves can be machined. Therefore, the combined electrode provided by the present invention can be adapted to the machining of splines with various key groove structures. In the prior art, if there are so many types of splines, so many electrodes need to be manufactured, which is far less simple and convenient than the combined electrode of the present invention.

[0114] The locking electrode setscrew 5 is inserted into the screw hole, so that the upper surface of the cylindrical electrode 3 arranged in the electrode mounting hole abuts against the upper top surface of the electrode mounting hole for fixation.

[0115] As Figure 12As shown, the shape of the electrode mounting hole is as follows: the lower half of the electrode mounting hole is a semi-cylindrical wall surface, and the upper part includes two inclined surfaces that are symmetric with respect to the diameter of the vertical hole perpendicular to the axis to form the upper top surface. The two inclined surfaces are perpendicular to each other, forming a 90° mounting hole. The cylindrical electrode 3 is lifted by the locking electrode setscrew 5 and abuts against the upper top surface of the electrode mounting hole for fixation. Such a special-shaped mounting hole makes the cylindrical electrode firmly fixed in the mounting hole and has good centering. In addition, such a mounting hole can also accommodate cylindrical electrodes of various diameter specifications for machining splines with different keyway widths, such as Figure 12 as described, the electrode mounting hole can fix a cylindrical electrode with a diameter of 3 - 6.5 mm. The included angle between the two inclined surfaces in the upper part of the electrode mounting hole can also be 60° (as Figure 13 shown), or it can be an included angle of 120 degrees (as Figure 13a shown).

[0116] Such as Figures 19 to 21 shown is a combined electrode for EDM machining of external splines, which includes an electrode mounting rod 14, an external spline positioning mandrel 15, a cylindrical electrode 16, and a locking electrode setscrew 5. The difference from the combined electrode for machining internal splines lies in the connection structure between the external spline positioning mandrel 15 and the electrode mounting rod 14.

[0117] Such as Figure 20 , Figure 21 and Figure 26 shown, the external spline positioning mandrel 15 includes three sections. The upper section is the connection section with the electrode mounting rod, which is a cylindrical optical axis. In contrast, a light hole is provided on the bottom surface of the central hole of the electrode mounting rod 14, and the light hole and the connection section form an interference fit, which can clamp the external spline positioning mandrel 15 in the central hole of the electrode mounting rod. The middle section is the positioning section, which is a cylindrical shaft section, and each cylindrical electrode 16 installed in the electrode mounting hole abuts against the positioning section. The lower section is the handling section, and the positioning mandrel 15 is clamped and disassembled from the electrode mounting rod by holding this handling section.

[0118] When machining the internal spline, the end of each cylindrical electrode 3 located outside the central hole of the electrode mounting rod 1 on the circumferential locus (enveloping circle) corresponds to the bottom surface of the keyway of the internal spline in the workpiece 9 to be machined, that is, the major diameter D of the internal spline; it also includes an internal spline positioning mandrel 2, which is inserted into the central hole of the electrode mounting rod 1 to form a detachable fixing structure, so that one end of each cylindrical electrode 3 facing the inside of the central hole abuts against the internal spline positioning mandrel 2 for positioning. The diameter of the internal spline positioning mandrel 2 matches the central hole of the electrode mounting rod 1, and the detachable fixing structure is: the internal spline positioning mandrel 2 is provided with a central bolt hole along the axial direction. Correspondingly, an axial central screw hole is provided on the bottom surface of the central hole of the electrode mounting rod 1. The internal spline positioning mandrel is fixed in the central hole of the electrode mounting rod 1 by a fixing mandrel screw 4 passing through the central bolt hole and screwing into the central screw hole. The fit between the internal spline positioning mandrel 2 and the central hole of the electrode mounting rod 1 is a clearance fit. The shaft tolerance is h6, and the hole tolerance is H7; the coaxiality is controlled within the range of 0.01 - 0.02 mm.

[0119] The manufacturing method of the above combined electrode is as follows:

[0120] For machining such as Figure 1 and Figure 2 The combined electrode for the internal spline as described above can be manufactured by the following method:

[0121] Step 1: Manufacture each component of the combined electrode

[0122] A. Machine the electrode mounting rod 1:

[0123] Select 45# round steel as the material, and perform quenching and tempering treatment T235. The size of the round steel is Φ30 with a length of 110 mm. One end is made into an electrode connection end, that is, an axial center hole is made on the end face of the electrode connection end, and a screw hole is machined on the bottom surface of the center hole. The specific method is as follows: Turn the end face and the outer circle Φ26 mm with a length of 62 mm, then bore a counterbore with a diameter of Φ15 mm (0~+0.02) mm and a depth of 17 mm to ensure the center hole of the Φ15 mm inner circle is coaxial with the Φ26 mm outer cylindrical surface with a coaxiality of 0.01 mm. Then drill the bottom hole of the M4 threaded hole with a size of Φ3.3 mm and a depth of 7 mm, and then use an M4 thread tap to make a threaded hole at the bottom of the center hole with a depth of M4 and a depth of 6 mm. Turn the Φ15 mm outer cylindrical surface and the stepped surface so that the length of the Φ26 mm outer cylinder is 60 mm, and then continue to turn the end face so that the length of the Φ15 mm outer cylinder is 40 mm. The other end is made into a connection end connected to the machine tool spindle. On the hole wall near the hole mouth of the center hole, 6 radial through holes are circumferentially distributed to form electrode mounting holes. The lower part of the electrode mounting hole is a cylindrical wall surface, and the upper part includes two inclined surfaces. 6 screw holes are also machined on the end face of the electrode connection end, and each of the screw holes axially communicates with each of the electrode mounting holes. Specifically, during machining center processing: Clamp and fix it on the turntable using the Φ15 outer cylindrical surface, align the Φ26 outer cylindrical surface, and control its runout ≤0.01 mm and straightness ≤0.01 / 50 mm. Machine 6 90° V-shaped grooves and 6 M3 threaded through holes at the corresponding positions according to the design drawing, and the bottom hole of the thread is Φ2.5 mm.

[0124] B. Machine the cylindrical electrode: Machine a number of cylinders with the same length and diameter. Select T2 copper standard cylinders as the material, and the size of the cylinder is Φ5.8 mm (0~-0.008) mm with a length of 100 mm. At one end of each cylinder, corresponding ends are machined according to the type of internal or external spline to be machined to form an electrode processing end, that is, wire cutting processing: Clamp and fix it on the workbench using the Φ5.8 mm outer cylindrical surface, align the side busbar and the upper busbar of the Φ5.8 outer cylindrical surface, and control the straightness of the two-direction busbars ≤0.01 / 80 mm. Select electrical parameters that meet the surface roughness Ra0.8 μm, and cut 6 pieces according to the design drawing length of 8.4 mm (+0.2~+0.3) mm. The perpendicularity between the cut circular section and the cylindrical surface should be ≤0.01 mm.

[0125] C. Machine the electrode positioning mandrel. Select 45# round steel as the material and perform quenching and tempering treatment T235, as Figure 8As shown, the round steel has a size of Φ16mm and a length of 25mm; it has such a structure that it has a detachable connection structure matching the connection structure of the electrode mounting rod, so that the electrode positioning mandrel is fixed in the central hole of the electrode mounting rod. Specifically, the A reference plane, Φ15mm (0 to -0.01)mm and C1 chamfer are machined, ensuring that the perpendicularity between the A reference plane and the Φ15mm outer cylindrical surface is 0.01mm. Then, a Φ4.5mm through hole is drilled, and the end face is machined to ensure a length of 15mm. Then, continue to machine a Φ8mm counterbore with a depth of 4.6mm and a C1 chamfer to form the bolt hole on the electrode mounting rod; the side of the machined electrode positioning mandrel forms a cylindrical surface that abuts against the cylindrical electrode.

[0126] Step 2: Assemble the combined electrode

[0127] A. The internal spline positioning mandrel 2 (see Figure 8 ) is inserted into the central hole of the electrode mounting rod 1 (see Figures 9 to 11 ). The mandrel 2 is fixed with an M4 internal hexagon screw 4 with a length of 12mm, and the electrode mounting rod 1 and the internal spline positioning mandrel 2 are assembled into one body. The hole diameter of the electrode mounting rod 1 and the shaft diameter of the internal spline positioning mandrel 2 have a clearance fit to meet the requirements of positioning accuracy and contact stability. The shaft tolerance is h6, and the hole tolerance is H7; the function is to ensure that the outer diameter of the internal spline positioning mandrel 2 is coaxial with the outer diameter of the electrode mounting rod 1, and the coaxiality is controlled within the range of 0.01 - 0.02mm, so as to ensure the consistency of the length of each cylindrical electrode 3 exposed outside the outer cylindrical surface of the electrode mounting rod 1 after installation.

[0128] B. Six cylindrical electrodes 3 (see Figure 14 and Figure 15 ) are inserted into the 90° V-shaped groove of the electrode mounting rod 1, that is, the electrode mounting hole (see Figure 12 ). After the end face of the cylindrical electrode 3 located in the central hole is in close contact with the outer cylindrical surface of the internal spline positioning mandrel 2, it is locked with an M3 locking electrode set screw 5 to complete the assembly of the combined electrode (see Figures 5 to 7 ). The shaft diameter tolerance of the cylindrical electrode 3 is h6.

[0129] Step 3: In-machine trimming of the outer diameter of the combined electrode envelope

[0130] As Figure 18 shown, in-machine trim the outer diameter of the tool electrode envelope, Figure 18Schematic diagram of the installation positions of the components of the in-machine dressing electrode. The specific process of in-machine dressing the electrode is as follows: The installed cylindrical electrode 3 and the electrode mounting rod 1 are installed together on the electrode fixture 11 under the main shaft 6 of the electric discharge forming machine tool; the dressing block 8 made of copper-tungsten alloy is fixed on the workbench 7. An inner hole is machined in the axial direction of the dressing block, and the diameter of the inner hole is the envelope circle diameter required for the combined electrode plus a margin. Or, the inner hole size on the dressing block 8 is larger than the shaft diameter of the internal spline positioning mandrel plus twice the length of the cylindrical electrode plus a 2-mm margin, and the height of the inner hole should be greater than the diameter of the cylindrical electrode plus a 2-mm margin.

[0131] Specifically, the dressing block is processed as follows: By machining, the length, width, and height dimensions are 60*60*20 mm, and it is ensured that the upper and lower planes of the dressing block after 20 mm are parallel, with a parallelism ≤0.02 mm; then, an inner hole with a diameter ≥Φ35 mm is machined at the middle position of the upper end face of the dressing block, with a cylindricity ≤0.01 mm and a parallelism with the upper plane ≤0.01 mm; then, the dressing block is fixed in the dressing block clamping device 13 on the machine tool workbench 7, and the upper end face of the dressing block is aligned with the XY plane of the machine tool, with a parallelism ≤0.01 mm; according to the keyway dimensions of the rectangular spline part 9, the unilateral dressing amount of the combined electrode, the electrical parameters, the motion trajectory, the motion speed, etc. of the copper-tungsten alloy for dressing the copper electrode are determined, and the electrode dressing program is compiled accordingly; the cylindrical electrode 3 is moved to the Φ35-mm inner hole of the dressing block, 8 mm from the upper end face, and the central position is determined in the hole of the dressing block using the shaft diameter of the electrode mounting rod 1, and this position is used as the starting position for program processing; the machining program is called and executed, and using the in-machine reverse copying function of the electric discharge forming machine tool, the made combined electrode is fixed on the main shaft through the electrode mounting rod and connected to the power supply, and the axis of the inner hole of the combined electrode and the dressing block is eccentrically arranged; starting from the position where the inner hole of the dressing block is closest to the machining end of the cylindrical electrode at one place, the dressing block moves around the combined electrode, and the trajectory followed is an envelope circle with a diameter of φ31.8 mm, and the outer diameter of the electrode is dressed in the machine. After the above example dressing, the cylindrical electrode forms an envelope circle diameter size of φ31.8 mm, and the production of the rectangular spline combined electrode is completed (see Figure 16 and Figure 17 ).

[0132] The specific operation process of in-machine dressing can be to fix the combined electrode on the main shaft of the electric discharge forming machine tool, call the compiled correction program, and perform correction through the dressing block made of copper-tungsten alloy arranged on the workbench.

[0133] This method of in-machine dressing the electrode not only ensures the dimensions, cylindricity, and coaxiality of the inner and outer circles of the electrode, but also ensures the relatively accurate position of the electrode on the machine tool, thus ensuring the position accuracy of electric discharge machining of internal and external splines.

[0134] Such as Figure 18As shown in the figure, the process of machining an internal spline using the above-mentioned combined electrode is as follows:

[0135] Step 1: Install and align the internal spline part 9. Fix the clamping device 12 on the machine tool workbench 7, then install and fix the rectangular internal spline part 9, and align the upper end face of the part with the XY plane of the machine tool. The parallelism is ≤0.01 mm. After completion, check whether the part is firmly fixed.

[0136] Step 2: The combined electrode has been installed and trimmed by the aforementioned method, and its relative position on the machine tool has been determined.

[0137] Step 3: Determine the relative position between the electrode and the workpiece. First, use the Φ26 of the combined electrode mounting rod 1 and the outer diameter of the part, and use the center alignment function of the machine tool column to determine the center position of the electrode and the part. Then set the X coordinate to 0 and the Y coordinate to 0. Second, use the lower end face of the cylindrical electrode 3 on the combined electrode and the upper end face of the part, and use the end face alignment function of the machine tool to determine the Z-axis 0 point position of the electrode and the part. Then move the combined electrode to Z coordinate 10.0, X coordinate 0, and Y coordinate 0, and use this position as the starting position of the program machining.

[0138] Step 4: According to the keyway dimensions of the rectangular spline part 9, determine the electrical parameters (such as pulse width, pulse interval, peak current, no-load voltage, etc.) and non-electrical parameters (such as machining depth, polarity, servo speed, movement direction, etc.) of the copper electrode machining steel, and compile the machining program accordingly.

[0139] Step 5: Call the machining program and execute it to complete the machining of the internal spline of the part.

[0140] For machining an external spline, the combined electrode provided by the present invention is as Figures 19 to 21 shown, including an electrode mounting rod 14, an electrode positioning mandrel, a cylindrical electrode 16, and a locking electrode top screw 5. The cylindrical electrode 16 is inserted into the electrode mounting hole of the electrode mounting rod 14 in the same manner as described above and fixed by the locking electrode top screw 5. The difference between the combined electrode for machining an external spline and the combined electrode for machining an internal spline lies in:

[0141] (1) The connection structure between the external spline positioning mandrel 15 and the electrode mounting rod 14

[0142] As Figure 20 , Figure 21 and Figure 26As shown, the external spline positioning mandrel 15 includes three sections. The upper section is the connection section with the electrode mounting rod, which is a cylindrical optical axis. Correspondingly, a light hole is provided on the bottom surface of the central hole of the electrode mounting rod 14, and the light hole and the connection section form an interference fit, so that the external spline positioning mandrel 15 can be clamped in the central hole of the electrode mounting rod 14; the middle section is the positioning section, which is a cylindrical shaft section, and each cylindrical electrode 16 installed in the electrode mounting hole abuts against the positioning section. The lower section is the holding section, and the positioning mandrel 15 is clamped and removed from the electrode mounting rod by holding this holding section by hand.

[0143] (2) The shape of the machining end of the cylindrical electrode 15 is as Figure 27 and Figure 28 shown. A 60° chamfer is provided at the machining end, and the diameter of the end face is 8.25 mm.

[0144] The external spline positioning mandrel 15 is fixedly connected to the light hole in the central hole of the electrode mounting rod 14 through its connection section, and the cylindrical electrode 16 is inserted into the electrode mounting hole of the electrode mounting rod 14 and fixed by the locking electrode setscrew 5.

[0145] (3) The envelope circle of the machining ends of the cylindrical electrodes of the combined electrode is within the central hole (as Figure 30 ).

[0146] (4) After the cylindrical electrode 16 is fixed, the external spline positioning mandrel 15 is removed, as Figure 29 and Figure 30 shown.

[0147] The manufacturing method of the combined electrode for machining external splines is basically the same as that of the combined electrode for machining internal splines, but there are also some differences.

[0148] The electrode positioning mandrel therein is the external spline positioning mandrel 15 (see Figure 26 ), where

[0149] the manufacturing method of the combined electrode is:

[0150] Similarly, the electrode mounting rod 14 and the external spline positioning mandrel 15 are machined by turning, and then the cylindrical electrode 16 is machined by wire cutting (see Figure 27 and Figure 28 ). Then assemble. Insert the external spline positioning mandrel 15 into the inner hole of the electrode mounting rod 14, and finally ensure the consistency of the length of each cylindrical electrode 16 exposed from the inner hole surface of the electrode mounting rod 14 after installation. Similarly, insert 6 cylindrical electrodes 16 into the 90° V-shaped groove of the electrode mounting rod 14. After the end face of the cylindrical electrode 16 in the central hole of the electrode mounting rod is in close contact with the outer cylindrical surface of the external spline positioning mandrel 15, lock it with the M3 locking electrode setscrew 5, and after locking, pull out the external spline positioning mandrel 15 to complete the assembly of the combined electrode (see Figures 32 to 34)。Inner diameter of the envelope circle of the in-machine dressing tool electrode, see Figure 31 , that is, the schematic diagram of the installation positions of the components of the in-machine dressing electrode. The difference between the specific process of in-machine dressing and that of internal splines is that the cylindrical dimension on the dressing block 18 should be less than the diameter of the external spline positioning mandrel minus 2 mm allowance. According to the above example, the diameter of the envelope circle formed by the combined electrode after dressing is φ28.2 mm, and the others are the same as the manufacturing method of the internal spline combined electrode; complete the manufacture of the rectangular spline combined electrode according to the prepared dressing electrode program (see Figure 30 ).

[0151] The method of using the combined electrode for machining external splines manufactured by the foregoing method to machine external splines, as Figure 31 shown, the part 9 is fixed on the part clamping device 12. After the same steps as steps 1 to 4 of internal spline machining, machining is carried out, and the combined electrode on the electrode fixture 11 on the main shaft 6 is used to machine its external splines.

[0152] The present invention provides a combined electrode for EDM of internal and external splines, including an electrode mounting rod, an electrode positioning mandrel, a cylindrical electrode and a locking electrode setscrew. The electrode positioning mandrel is detachably fixed in the central hole of the electrode mounting rod. The cylindrical electrode is inserted into the electrode mounting hole radially on the electrode mounting rod, and its machining end forms an envelope circle for machining splines outside or inside the central hole. The cylindrical electrode is fixed by an axial screw hole from the end face of the electrode mounting rod. Its manufacturing method includes manufacturing its various parts, assembling and in-machine dressing steps. The present invention also provides the application of this combined electrode, that is, the method for machining internal and external splines. The manufacturing method in the present invention can manufacture the combined electrode with high precision. The structure of this combined electrode is simple, but when using it to machine internal and external splines, high precision can be obtained. For the worn cylindrical electrode, it can be conveniently replaced and reused, effectively reducing costs, and is suitable for machining internal and external splines of various shapes. More specifically, this combined electrode for EDM of internal and external splines provided by the present invention has the following characteristics compared with the traditional mechanical machining spline hobs or broaches and the traditional integral electrodes:

[0153] ⑴ The cylindrical electrode can be selected as a standard part, is easy to manufacture and obtain, uses less copper material, and saves the production cycle and cost. Generally, spline hobs or broaches need to be customized;

[0154] ⑵ This electrode has the characteristic of simple structure compared with the traditional integral electrode. The electrode mounting rod and the positioning mandrel can be reused, and only the cylindrical electrode needs to be replaced;

[0155] ⑶ This electrode has the characteristic of being easy to ensure dimensional accuracy. The spline width only needs to be ensured by the shaft diameter of the cylindrical electrode, and because there is no macroscopic mechanical force in EDM, the spline width can be made very small; while the hob or broach cannot be made too thin or slender due to rigidity, and the spline width cannot be made too small;

[0156] ⑷ It has the characteristics of being easy to adjust and combine into different keyway widths, depths, and the number of keyways to form a series of standards. For example, the electrode mounting rod in the above example can achieve 2, 3, and 6 keyways, and the keyway width can range from 4 mm to 6 mm.

[0157] ⑸ It can conveniently achieve the processing of through slots, blind slots, internal and external splines, and internal splines in blind holes.

[0158] ⑹ It can conveniently expand the processing of internal and external splines with different cross-sectional shapes, such as rectangular, involute, triangular, cycloidal, trapezoidal, etc.

[0159] The existing integral electrodes are generally made by milling or wire electrical discharge machining. Their shape and size accuracy are limited by the machining accuracy, and the keyway size and the number of keyways are fixed, non-adjustable, and non-reusable, and relatively more materials are used. However, these problems can be easily solved in the combined electrode provided by the present invention. The production of cylindrical electrodes can easily ensure their shape and size accuracy. Also, by screening, a group of cylindrical electrodes with outer diameter sizes meeting the requirements and very good consistency can be selected. Therefore, high accuracy can also be obtained by making them into combined electrodes. When using the combined electrode provided by the present invention to process a rectangular spline structure, its processing accuracy can be guaranteed. In addition, the combined electrode provided by the present invention also has the advantage that the worn cylindrical electrodes can be conveniently replaced and reused to reduce costs compared with integral electrodes.

Claims

1. A manufacturing method of a combined electrode for EDM of internal and external splines, comprising the following steps: Step 1: Manufacture each component of the combined electrode A. Machine the electrode mounting rod: Machine the electrode mounting rod from a columnar bar stock. One end thereof is made into a connection end connected to the machine tool spindle, and the other end is made into an electrode connection end. That is, an axial central hole is made on the end face of the electrode connection end, a connection structure is machined on the bottom surface of the central hole, and several radial through holes are circumferentially distributed on the hole wall near the hole mouth of the central hole to form electrode mounting holes. The lower part of the electrode mounting hole is a cylindrical wall surface, and the upper part includes two inclined surfaces symmetric with respect to the diameter of a vertical hole perpendicular to the axial direction. Several screw holes are also machined on the end face of the electrode connection end, and each of the screw holes axially communicates with each of the electrode mounting holes respectively; B. Machine the cylindrical electrodes: Machine several cylinders with the same length and diameter, and machine corresponding ends at one end of each cylinder according to the types and specifications of the internal or external splines to be machined to form electrode machining ends; C. Machine the electrode positioning mandrel so that it has such a structure: It has a detachable connection structure matching the connection structure of the electrode mounting rod, so that the electrode positioning mandrel is fixed in the central hole of the electrode mounting rod; Step 2: Assemble the combined electrode Fix the electrode positioning mandrel in the central hole of the electrode mounting rod through the detachable connection structure on it and the connection structure on the electrode mounting rod; Insert the cylindrical electrodes into the electrode mounting holes of the electrode mounting rod. One end located in the central hole abuts against the electrode positioning mandrel, and then lock the electrode set screws into the screw holes so that each cylindrical electrode abuts against and fits tightly against the upper top surface of the electrode mounting hole formed by the two symmetric inclined surfaces for axial positioning; For machining internal splines, the electrode machining ends of each cylindrical electrode are placed outside the central hole, and the other ends abut against the electrode positioning mandrel; or, For machining external splines, the electrode machining ends of each cylindrical electrode abut against the electrode positioning mandrel. After the cylindrical electrodes are fixed, remove the electrode positioning mandrel from the electrode mounting rod; Step 3: Machine the envelope circle of the combined electrode on the machine For the combined electrode for internal spline machining, Machine a columnar trimming block. An inner hole is machined axially on the trimming block. The diameter of the inner hole is the envelope circle diameter required for the combined electrode plus a margin. Or, the inner hole size on the trimming block is larger than the shaft diameter of the internal spline positioning mandrel plus twice the length of the cylindrical electrode plus a margin, and the height of the inner hole should be greater than the diameter of the cylindrical electrode plus a 2-mm margin; Fix the trimming block on the machine tool table; or, For the combined electrode for external spline machining, the trimming block is a cylinder, and the outer diameter of the cylinder is smaller than the envelope circle diameter required for the combined electrode plus a margin. Or, the outer diameter of the trimming block is the shaft diameter of the external spline positioning mandrel minus a margin; Fix the trimming block on the working table of the machine tool, Fix the combined electrode made in Step 1 and Step 2 on the spindle through the electrode mounting rod for power connection. The combined electrode and the axis of the inner hole or cylinder of the trimming block are eccentrically arranged; Insert the combined electrode into the inner hole of the trimming block, or insert the hole surrounded by each cylindrical electrode of the combined electrode onto the cylinder of the trimming block; By using the in-machine reverse copying function of the electro-discharge forming machine tool, the dressing block is made to travel along the locus of the envelope circle of the combined electrode, and in-machine dressing is performed on each cylindrical electrode of the combined electrode.

2. The method for manufacturing the combined electrode according to claim 1, wherein: For machining internal splines, the diameter of the envelope circle at the external machining end of the cylindrical electrode is greater than the root circle diameter of the internal spline, and the difference, i.e., the allowance, is 1 - 4 mm. Or, For machining external splines, the diameter of the envelope circle at the internal machining end of the cylindrical electrode is greater than the tip circle diameter of the external spline, and the difference, i.e., the said allowance, is 1 - 2 mm; the dimensions, cylindricity, and coaxiality of the circumferential surface meet the design requirements, and the combined electrode with the required dimensions is manufactured; and / or, Before step 1, according to the keyway dimensions of the rectangular spline part, including the depth and width of the keyway, a positioning mandrel is designed, the shaft diameter of the electrode mounting rod, the dimensions and number of the electrode mounting holes are set, the cylindrical electrode is designed, and processed and manufactured.

3. The method for manufacturing the combined electrode according to claim 1 or 2, wherein: In step 1, In machining the electrode mounting rod, the connection structure on the bottom surface of the central hole is a threaded hole. Correspondingly, an axial central hole is provided on the electrode positioning mandrel, and the electrode positioning mandrel is fixed in the central hole of the electrode mounting rod by a fixing mandrel screw. This structure is provided for the combined electrode for machining internal splines; or, it is a clearance hole, and this clearance hole forms a transitional fit with the connecting section of the electrode positioning mandrel connected to the electrode mounting rod. This structure is provided for the combined electrode for machining external splines; and / or, In machining the electrode mounting rod, the electrode mounting holes are at the same horizontal height, and their diameter is greater than the diameter of the cylindrical electrode. The locking electrode set screw jacks up the cylindrical electrode so that its upper surface presses against the top surface of the electrode mounting hole; and / or, The lower half of the electrode mounting hole is a semi-cylindrical wall surface, and the included angle between the two inclined surfaces in the upper half is 90°; or, the included angle between the two inclined surfaces in the upper part is 60°, or 120°; after the cylindrical electrode is jacked up, its upper surface abuts against the two inclined surfaces; and / or A relief groove is designed between the two inclined surfaces; and / or, The shape of the machining end of the cylindrical electrode matches the corresponding shape of the spline to be machined. It is a cylindrical shape, corresponding to machining the keyway of the rectangular internal spline; or it is a frustum shape with a conical surface, corresponding to machining the keyway between two key teeth of the rectangular external spline; or it is a triangular shape formed by two inclined surfaces symmetrically arranged with respect to the central axis plane of the cylindrical electrode, corresponding to machining the triangular spline, or it is an involute shape, corresponding to machining the involute spline; and / or, The aperture of the central hole of the electrode mounting rod and the shaft diameter of the electrode positioning mandrel are in a loose fit; and / or, In machining the cylindrical electrode, the outer cylindrical surface of the cylindrical electrode is clamped and fixed on the workbench, and the lateral generatrix of the outer cylindrical surface is aligned horizontally and vertically; and / or, In step 3, The allowance between the inner hole or outer diameter of the dressing block and the envelope circle of the combined electrode is 1 - 4 mm; and / or, The material of the dressing block is copper-tungsten alloy; and / or, The parallelism of the upper and lower bottom surfaces of the dressing block ≤ 0.02 mm; and / or, The cylindricity of the inner hole or cylinder of the dressing block ≤ 0.01 mm; and / or, The perpendicularity of the inner hole of the dressing block to the upper plane ≤ 0.01 mm.

4. The manufacturing method of the combined electrode according to claim 3, wherein: The aperture of the central hole of the electrode mounting rod and the shaft diameter of the electrode positioning mandrel, wherein the shaft tolerance is h6 and the hole tolerance is H7; the coaxiality between the two is controlled within the range of 0.01 - 0.02 mm; and / or, During the machining of the cylindrical electrode, the outer cylindrical surface of the cylindrical electrode is clamped and fixed on the workbench, and the lateral generatrix and upper generatrix of the outer cylindrical surface are aligned to control the straightness in two directions ≤ 0.01 mm / 80 mm; meeting the surface roughness Ra 0.8 μm; and / or, The perpendicularity between the circular section obtained by cutting and the cylindrical surface should ≤ 0.01 mm; and / or, The allowance between the inner hole or outer diameter of the dressing block and the envelope circle of the combined electrode is 1 - 4 mm.

5. The manufacturing method of the combined electrode according to claim 4, wherein: The allowance is 2 mm.

6. A combined electrode for EDM of internal and external splines manufactured by the method as claimed in claims 1 to 5, characterized in that: Comprising an electrode mounting rod, an electrode positioning mandrel, a cylindrical electrode and a locking electrode setscrew, The electrode mounting rod is a rod body. One end of the rod body is provided with a connection end connected to the main shaft, and the other end is an electrode connection end. An axial central hole is provided on the end face of the electrode connection end. A connection structure is provided on the bottom surface in the central hole. Along the circumferential direction of the hole wall near the hole mouth of the central hole, a plurality of radial electrode mounting holes are provided. The lower part of the electrode mounting hole is a cylindrical wall surface, and the upper part includes two inclined surfaces symmetrically arranged with respect to the diameter of the vertical hole perpendicular to the axial direction to form an upper top surface. On the end face of the electrode connection end where the central hole is provided, a plurality of screw holes are also provided, and each of the screw holes axially communicates with each of the electrode mounting holes respectively; The electrode positioning mandrel is a rod body, which at least includes a section, namely an electrode positioning section, whose diameter is smaller than the diameter of the central hole. The side wall of this section is for the end of the cylindrical electrode installed in the electrode mounting hole of the electrode mounting rod to abut against when located in the central hole. A connection part connected to the electrode mounting rod is also provided thereon to form a detachable connection structure; There are a plurality of the cylindrical electrodes. According to the number and orientation of the splines of the machined part, the cylindrical electrodes are respectively inserted into the corresponding electrode mounting holes on the electrode mounting rod. Each cylindrical electrode has a machining end, and the machining end corresponds to the shape and specification of the spline to be machined. The machining end of each cylindrical electrode is located outside the electrode mounting rod or in the central hole, on the same circumferential locus, i.e., the envelope circle. The end located in the central hole abuts against the side wall of the electrode positioning section of the electrode positioning mandrel, or abuts against the electrode positioning mandrel for positioning before completing step 2; There are 6 electrode mounting holes evenly distributed circumferentially on the electrode mounting rod, or 8 electrode mounting holes are evenly distributed; The locking electrode setscrew is inserted into the screw hole, so that the cylindrical electrode arranged in the electrode mounting hole abuts against the upper top surface of the electrode mounting hole for fixation; When machining internal splines, the machining ends of the cylindrical electrodes located outside the central hole of the electrode mounting rod are on the same circular locus, i.e., the envelope circle; or, When machining external splines, the ends of the cylindrical electrodes located inside the central hole of the electrode mounting rod are on the same circular locus, i.e., the envelope circle.

7. The combined electrode according to claim 6, characterized in that: For machining internal splines, the electrode positioning mandrel is an internal spline positioning mandrel, the diameter of which matches the central hole of the electrode mounting rod. The detachable connection structure is as follows: the internal spline positioning mandrel is axially provided with a central bolt hole to form the connection structure with the electrode mounting rod. Correspondingly, the connection structure provided on the bottom surface of the central hole of the electrode mounting rod is an axial central screw hole. The internal spline positioning mandrel is fixed in the central hole of the electrode mounting rod by a fixing mandrel screw passing through the central bolt hole on the internal spline positioning mandrel and screwing into the central screw hole on the bottom surface of the central hole of the electrode mounting rod; and / or, For machining internal splines, there is a clearance fit between the electrode positioning section of the electrode positioning mandrel and the central hole of the electrode mounting rod. The shaft tolerance is h6, and the hole tolerance is H7; the coaxiality is controlled within the range of 0.01 - 0.02 mm; and / or, For machining external splines, the electrode positioning mandrel is an external spline positioning mandrel, including an electrode positioning section and a connection section. The diameter of the electrode positioning section thereon is smaller than the inner diameter of the central hole of the electrode mounting rod, corresponding to the minor diameter d of the external spline. The connection section thereon is a clamping section with a diameter smaller than that of the positioning section. The connection structure on the electrode mounting rod is as follows: an axial optical hole is provided at the bottom of the central hole of the electrode mounting rod, and the connection section of the electrode positioning mandrel is arranged in this optical hole to form an interference fit; and / or, The shape of the machining end of the cylindrical electrode matches the corresponding shape of the spline to be machined. It is cylindrical in shape, corresponding to machining the keyways of rectangular internal splines; or it is a frustum shape with a conical surface, corresponding to machining the keyways between two key teeth of rectangular external splines; or it is a triangular shape composed of two inclined planes symmetrically arranged with respect to the central axis plane of the cylindrical electrode, corresponding to machining triangular splines, or it is an involute shape, corresponding to machining involute splines.

8. The combined electrode according to claim 7, characterized in that: The lower half of the electrode mounting hole is a semi-cylindrical wall surface, and the included angle between the two symmetric inclined planes of the electrode mounting hole is 90°; and / or, the included angle between the two symmetric inclined planes is 60° or 120°; and / or, A rectangular relief groove is further provided between the two inclined planes of the electrode mounting hole; and / or, The external spline positioning mandrel further includes a gripping section connected to the electrode positioning section; and / or, The shaft diameter tolerance of the cylindrical electrode is h6.

9. The application of the combined electrode according to claims 6 to 8, characterized in that, Applied to machining part splines, its machining method is: Step 1: Install the part blank in the fixture on the machine tool workbench; Step 2: Determine the relative position between the combined electrode and the machine tool during the dressing of the above-mentioned combined electrode. Step 3: Center the combined electrode fixed on the main shaft with the part blank. Using the outer diameter of the electrode mounting rod in the combined electrode and the outer diameter of the part blank, determine the center position of the electrode and the part by using the center alignment function of the machine tool column. Then set the zero positions of the X coordinate and the Y coordinate. Next, use the lower end face of the cylindrical electrode on the combined electrode and the upper end face of the part to determine the zero position of the Z axis of the electrode and the part by using the end face alignment function of the machine tool, and use this position as the starting position for program processing; Step 4: Determine the electrical parameters for machining steel with the cylindrical electrode according to the keyway dimensions of the spline part, including pulse width, pulse interval, peak current, and no-load voltage, and non-electrical parameters, including machining depth, polarity, servo speed, and movement direction, and compile the machining program accordingly; Step 5: Call the machining program and execute it to complete the machining of the internal spline or external spline of the part.

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