Machining compensation method of electric discharge machine

Abstract

The invention discloses a machining compensation method for an electric discharge machine, and the method relates to a hardware foundation comprising an electrode which is clamped at the tail end of a servo driving mechanism and is provided with a machining surface and a reference surface; the standard ball assembly is fixed on the working platform and comprises a standard ball; the method comprises the following steps that before machining, a datum plane of an electrode makes contact with a standard ball, and a Z-axis mechanical coordinate value X1 is recorded; the numerical control system of the electric discharge machine executes a fixed program once to drive the electrode to move to the position of the standard ball under the influence of thermal deformation of the lead screw during any machining for a period of time, the reference surface of the electrode is contacted with the standard ball again, and a Z-axis numerical value X2 is recorded; the compensation amount of machining is determined according to the difference value of X2 and X1; and when machining is continued, the compensation amount in the step S3 is added into the actual machining depth. According to the scheme, a reasonable compensation mode can be selected according to length change caused by heating of the lead screw in the machining process.

Description

Technical Field

[0001] The invention relates to the technical field of electric spark machining, in particular to a machining compensation method of an electric spark machine. Background Art

[0002] The precision of EDM parts is not only related to the manufacturing accuracy of the EDM machine itself and the manufacturing accuracy of the electrode, but also closely related to the thermal deformation of the machine during use. It is expected that precision machine tools have smaller thermal deformation and shorter thermal equilibrium time.

[0003] A Chinese patent with authorization announcement number CN113681098B discloses a method for controlling thermal deformation in the electrospark machining of small holes in dense arrays of thin-walled parts. The method uses multi-physical field simulation to simulate the material removal process of a single-hole thin-walled part during high-speed electrospark machining of small holes and the resulting thermal deformation effect, and obtains the thermal stress distribution and local thermal plastic deformation, thereby obtaining the distance constraint between adjacent machining holes, that is, the minimum critical distance between adjacent holes for the mutual influence of thermal elastic-plastic deformation. Then, a non-productive time model of the electrospark machining process of small holes in dense arrays of thin-walled parts with thermal deformation constraints is established. The total non-productive time is minimized by optimizing the model, thereby improving the machining efficiency while ensuring that the thermal deformation does not exceed the tolerance.

[0004] However, the prior art only considers the thermal deformation effect generated during the EDM process of workpieces with special shapes, that is, the solution of the prior art focuses on the thermal deformation of the workpiece itself.

[0005] However, the drive screw of the EDM machine (the screw mechanism that drives the electrode to move, which is the existing structure of the EDM machine) is affected by temperature changes, and changes by about 0.01mm for every degree of change. The servo motor will generate two heat sources during operation. One is the heat generated by the servo motor itself during power-on operation, and the other is the heat generated by the friction between the active part and the guide rail during movement. Spark machining often causes temperature changes in the screw, which can reach up to 10 degrees Celsius, causing the screw to extend by 0.1mm, often leading to motion errors. The temperature affects the processing depth and causes inaccurate processing, which has a great impact on the mold processing quality and leads to a decline in processing quality. Summary of the invention

[0006] The purpose of the present invention is to provide a machining compensation method for an electric spark machine to solve the problems existing in the prior art.

[0007] The object of the present invention is achieved in this way: a processing compensation method for an electric spark machine, the hardware basis involved in the method comprises:

[0008] An electrode, the electrode is clamped at the end of the servo drive mechanism, the electrode has a processing surface in contact with the workpiece, and also has a reference surface offset from the processing surface;

[0009] A standard ball assembly fixed on the working platform, the standard ball assembly comprising a standard ball;

[0010] When this method is executed, it follows the following steps:

[0011] S1. Before processing, touch the reference surface of the electrode to the standard ball and record the Z-axis mechanical coordinate value X1;

[0012] S2. After a period of arbitrary processing, affected by the thermal deformation of the screw rod, the CNC system of the EDM machine executes a fixed program to drive the electrode to the position of the standard ball, touch the reference surface of the electrode with the standard ball again, and record the Z-axis value X2;

[0013] S3, determining the compensation amount of machining according to the difference between X2 and X1;

[0014] S4. When continuing processing, add the compensation amount in step S3 to the actual processing depth.

[0015] Furthermore, the standard ball assembly consists of a standard ball, a support rod and a support base, the support base is detachably fixed to the work platform, the support rod extends vertically, and the upper and lower ends of the support rod are respectively fixedly connected to the standard ball and the support base.

[0016] Furthermore, in step S1, the Z-axis mechanical coordinate value X1 is temporarily stored in register H100.

[0017] Furthermore, in step S3, the difference X2-X1 is temporarily stored in a register H101.

[0018] Furthermore, when machining continues, the value of H101 is added to the actual machining depth.

[0019] Furthermore, steps S2 to S4 are executed once or multiple times.

[0020] The beneficial effects of the present invention are:

[0021] A reasonable compensation mode can be selected according to the length change caused by the heating of the screw during the processing. This compensation method does not require too much investment cost, and only requires a clamping tool with a standard point that can be tested, thereby solving the problem of "inaccurate processing depth due to temperature influence" in the prior art and significantly improving the processing quality. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a schematic diagram of the process flow of the present invention.

[0023] Explanation of the reference numerals: 1-electrode; 1a-reference surface; 1b-machining surface; 2-standard ball; 3-support rod; 4-support base; 5-working platform; 6-workpiece. DETAILED DESCRIPTION

[0024] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0025] like Figure 1 As shown in the figure, a machining compensation method for an EDM machine is proposed. The hardware basis involved in this method includes:

[0026] Electrode 1, which is clamped at the end of the servo drive mechanism and can move in space. The electrode 1 has a processing surface 1b in contact with the workpiece 6, and also has a reference surface 1a offset from the processing surface 1b;

[0027] A standard ball assembly is fixed on a working platform 5 (the upper surface of the working platform 5 is a horizontal plane), and the standard ball assembly is offset from the workpiece 6 in position. The standard ball assembly consists of a standard ball 2, a support rod 3 and a support base 4. The support base 4 is detachably fixed to the working platform 5, and the support rod 3 extends vertically. The upper and lower ends of the support rod 3 are respectively fixedly connected to the standard ball 2 and the support base 4. The support base 4 is a rectangular block structure, which is in plane contact with the working platform 5, so that the standard ball 2 can stably play its position reference role. In the CNC system, the position of the standard ball 2 is an important reference coordinate point; the fixing method of the support base 4 is not limited here.

[0028] Therefore, through the above hardware setting scheme, it can be known that in this embodiment, in order to solve the problems arising in the prior art, a standard ball assembly is mainly set up in this embodiment, and the reference surface 1a of the electrode 1 is used to contact the standard ball 2 in a fixed position to know and detect the deviation caused by the thermal deformation of the screw rod; the thermal deformation of the screw rod of the servo drive unit will inevitably lead to errors in the real-time position of the electrode 1. By detecting the real-time position of the electrode 1, the degree of thermal deformation of the screw rod of the servo drive unit can be known.

[0029] According to the above hardware settings, a machining compensation method is provided, which is controlled by a numerical control system of an EDM machine and comprises the following steps in sequence:

[0030] S1: Before processing, the reference surface 1a of the electrode 1 touches the standard ball 2, and the CNC system records the Z-axis mechanical coordinate value X1 and temporarily stores it in the register H100;

[0031] S2: After a period of arbitrary processing (the specific time interval can be determined based on process experience or specific conditions), the thermal deformation of the screw rod causes an error in the position of the electrode 1. The numerical control system needs to determine the error amount of the real-time position of the electrode 1 (which can be displayed on the display interface of the numerical control system). The numerical control system of the EDM machine executes a fixed program G138 to drive the electrode 1 to the position of the standard ball 2, and touches the reference surface 1a of the electrode 1 with the standard ball 2 again. The numerical control system records the Z-axis value X2;

[0032] S3: temporarily store the difference between X2 and X1 in a register H101, so as to know the error of the real-time position of the electrode 1 caused by the thermal deformation of the screw rod. The numerical control system can determine the compensation amount of the machining according to the difference between X2 and X1, so as to know the specific compensation amount in the current state, so as to better ensure the accuracy of the EDM machining;

[0033] S4: When continuing the processing, the value of H101 (compensation amount of processing) is added to the actual processing depth to form processing compensation, so as to achieve the purpose of selecting a reasonable compensation value according to the length change caused by the heating of the screw rod during the processing, thereby accurately fine-tuning the position of electrode 1 and improving the processing accuracy of electrode 1.

[0034] In actual processing, the number of times the G138 instruction is executed is determined according to the processing time of one electrode 1, and the number of times steps S2 to S4 are executed is one or more times.

[0035] By executing the above steps, the error caused by the thermal deformation of the screw rod is overcome and the processing accuracy of the mold (workpiece 6) is improved.

[0036] In the description of the present invention, it should be noted that the terms "center", "up", "down", "left", "right", "vertical", "horizontal", "front", "back" and the like indicate directions or positional relationships based on the directions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore cannot be understood as a limitation on the present invention; in the present invention, it should also be noted that the terms "installation" and "connection" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, an integrally formed connection, a mechanical connection, or an indirect connection through an intermediate connecting component, and the specific meaning of the terms in this utility model can be understood according to the specific circumstances.

[0037] It is obvious to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the present invention can be implemented in other specific forms without departing from the spirit or essential features of the present invention. Therefore, the embodiments should be regarded as exemplary and non-limiting from any point of view, and the scope of the present invention is defined by the appended claims rather than the above description, and it is intended that all changes falling within the meaning and scope of the equivalent elements of the claims are included in the present invention, and any reference numerals in the claims should not be regarded as limiting the claims involved.

[0038] In addition, it should be understood that although the present specification is described according to implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment may also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

Claims

1. A machining compensation method for an electric spark machine, characterized in that: The hardware foundation involved in this method includes: An electrode (1), the electrode (1) being clamped at the end of a servo drive mechanism, the electrode (1) having a processing surface (1b) in contact with a workpiece (6), and also having a reference surface (1a) offset from the processing surface (1b); A standard ball assembly fixed on the working platform (5), the standard ball assembly comprising a standard ball (2); When this method is executed, it follows the following steps: S1. Before processing, the reference surface (1a) of the electrode (1) is brought into contact with the standard ball (2), and the Z-axis mechanical coordinate value X1 is recorded; S2, after a certain period of processing, the CNC system of the EDM machine executes a fixed program under the influence of the thermal deformation of the screw rod, drives the electrode (1) to move to the position where the standard ball (2) is located, makes the reference surface (1a) of the electrode (1) touch the standard ball (2) again, and records the Z-axis value X2; S3, determining the compensation amount of machining according to the difference between X2 and X1; S4. When continuing processing, add the compensation amount in step S3 to the actual processing depth.

2. The machining compensation method of an electric spark machine according to claim 1, characterized in that: The standard ball assembly is composed of a standard ball (2), a support rod (3) and a support base (4); the support base (4) is detachably fixed on a working platform (5); the support rod (3) extends vertically; the upper and lower ends of the support rod (3) are respectively fixedly connected to the standard ball (2) and the support base (4).

3. The machining compensation method of an electric spark machine according to claim 1, characterized in that: In step S1, the Z-axis mechanical coordinate value X1 is temporarily stored in register H100.

4. The machining compensation method of an electric spark machine according to claim 3, characterized in that: In step S3, the difference value X2-X1 is temporarily stored in a register H101.

5. The machining compensation method of an electric spark machine according to claim 4, characterized in that: When continuing machining, add the value of H101 to the actual machining depth.

6. A machining compensation method for an electric spark machine according to any one of claims 1 to 5, characterized in that: Steps S2 to S4 are executed once or multiple times.

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