A wire-cut electric discharge machining device and a machining method for constant-speed feeding of the last cut using the device

Abstract

The application discloses a kind of wire cut electrical discharge machining device, comprising: discharge module, discharge module carries out discharge according to a discharge parameter;Discharge gap processing module, discharge gap processing module carries out sampling to discharge gap voltage;Physical condition module, physical condition module generates physical digital code;FPGA processing module, FPGA processing module receives discharge gap voltage parameter and physical digital code;Host computer, host computer instructs FPGA processing module to discharge gap voltage parameter and physical digital code are operated, and generate constant feed signal, feed signal is fed back to host computer, host computer is according to feed signal instruction servo amplifier, servo amplifier drives workbench feed.Through detecting discharge state and preset physical condition, feedback to FPGA control system, produce constant speed feed, overcome the random disturbance of multiple uncertain factors in outside, to process the product with excellent performance.

Description

Technical Field

[0001] The present invention relates to an electric spark machining device, more specifically, to an electric spark wire cutting discharge machining device. Background Art

[0002] As we all know, wire-cut EDM is a type of electrical machining that utilizes the principle of electrical discharge to erode conductive metals. Typically, a reciprocating molybdenum wire electrode serves as the cathode, and the metal material serves as the anode, forming two poles. A dielectric is used to apply voltage across the two poles. As the distance between the two poles decreases, a breakdown discharge is triggered, eroding the conductive anode metal material. The distance between the two poles is maintained, and the electrodes or metal material are moved at a certain tracking feed rate, preventing both short circuits and open circuits. This ensures that requirements for position, size, shape, surface quality, machining speed, and molybdenum wire loss are met. During EDM, the distance between the two poles is generally expressed as the voltage between them, commonly referred to as the gap voltage.

[0003] To improve the quality of a workpiece, such as its position, shape, and surface roughness, multiple cuts are necessary. This is explained below using the example of a one-cut, two-trim process. The first cut is primarily for roughing, producing the general shape and general roughness at high speed. The first trimming process achieves dimensional accuracy and improves the finish appropriately. The second trimming process primarily improves the finish and further enhances dimensional accuracy.

[0004] like Figure 1 As shown, the first cutting is a closed processing, and the facing size of the molybdenum wire discharge is approximately equal to the molybdenum wire diameter plus the discharge gap of 0.2mm.

[0005] like Figure 2 As shown in the figure, the first trimming is open machining, and the facing size of the molybdenum wire discharge is approximately equal to 0.05mm. Due to the difference in facing size, the gap voltage is different.

[0006] like Figure 3 As shown, the second trimming is open machining, and the facing dimensions of the molybdenum wire discharge are approximately equal to 0.01 mm.

[0007] It should be noted that, for the first and second knife trimming, the gap voltage is different due to the difference in the facing sizes.

[0008] The following introduces the discharge state of electric spark wire cutting.

[0009] like Figure 4 As shown in the figure, the discharge state of wire EDM can be roughly divided into three types: open circuit, spark discharge (unstable discharge is also classified here) and short circuit. The ideal state is that there is no open circuit, no load and short circuit, only normal spark discharge. Figure 4As can be seen in the figure, the voltage amplitudes in these three states differ. A discharge gap voltage is applied across the gap formed by the electrode wire (i.e., molybdenum wire) and the workpiece. After a breakdown delay, the gap breaks down, and the discharge gap voltage drops from the no-load open circuit voltage to the spark discharge maintenance voltage. However, in actual machining, external factors such as poor chip removal, incomplete deionization of the interelectrode dielectric, electrode wire jitter, and inconsistencies between the tracking curve and the servo curve can cause a partial short circuit. Similarly, a tracking feed rate that is slower than the material removal rate can cause a partial open circuit.

[0010] Currently, there are two methods for detecting the discharge gap voltage of a wire-cut electric discharge machine tool, namely, a discharge gap voltage average detection circuit and a discharge gap voltage peak detection circuit.

[0011] like Figure 5 The figure shows the average detection circuit of the discharge gap voltage. Specifically, the discharge gap voltage is charged to the capacitor C through the resistor R1 and filtered to become the average value, which is then divided by R2 to output a voltage signal representing the average value.

[0012] like Figure 6 Figure 2 shows the discharge gap voltage peak detection circuit. Specifically, voltage regulator W1 blocks and filters spark-maintaining voltages and short-circuit voltages below its regulated value. Only no-load peak-to-peak voltages greater than the sustaining voltage can pass through diode D1 to charge and filter capacitor C1. Voltage regulator W2 eliminates no-load voltages above its regulated value. The filtered voltage is then divided by RW1 to output a peak-to-peak voltage signal.

[0013] However, due to the different sizes of molybdenum wire discharge, the change of discharge gap voltage is different. The above two detection methods cannot fully reflect the change of gap, which is especially serious for the last cut. During the last cut, the running speed of the molybdenum wire is reduced, and the impact force of water has a great influence on the spatial position of the molybdenum wire. Coupled with the influence of the rigidity of the mechanical part, the discharge gap voltage at this time changes unpredictably and often cannot truly guide the feed, but can only indicate a state. Summary of the Invention

[0014] Based on this, it is necessary to provide an electric spark wire cutting discharge machining device to address the above technical problems.

[0015] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0016] A wire-cut electric discharge machining device, characterized in that the wire-cut electric discharge machining device comprises:

[0017] a discharge module, wherein the discharge module performs discharge according to a discharge parameter;

[0018] a discharge gap processing module, wherein the discharge gap processing module samples the discharge gap voltage during wire-cut electric discharge machining and performs proportional processing on the sampled discharge gap voltage to generate a discharge gap voltage parameter;

[0019] a physical condition module, which generates a physical digital code from the physical parameters of the workpiece, the physical parameters of the cutting fluid, the physical parameters of the molybdenum wire, and the physical parameters of the machine tool;

[0020] an FPGA processing module, wherein the FPGA processing module receives the discharge gap voltage parameter and the physical digital code;

[0021] A host computer instructs the FPGA processing module to calculate the discharge gap voltage parameter and the physical digital code and generate a constant feed signal. The feed signal is fed back to the host computer. The host computer instructs a servo amplifier according to the feed signal, and the servo amplifier drives a workbench to feed.

[0022] As a preferred embodiment of the present invention, the host computer feeds the workbench through a servo amplifier according to the feed signal.

[0023] As a preferred embodiment of the present invention, the workpiece is characterized by the material of the workpiece and the height of the workpiece, the cutting fluid is characterized by the type of cutting fluid and the contamination degree of the cutting fluid, the molybdenum wire is characterized by the diameter of the molybdenum wire, and the machine tool is characterized by the rigidity value of the machine tool during movement.

[0024] As a preferred embodiment of the present invention, the FPGA processing module outputs the discharge parameters and controls the discharge module.

[0025] As a preferred embodiment of the present invention, the discharge module is a complementary transistor push-pull circuit.

[0026] As a preferred embodiment of the present invention, the discharge gap processing module includes an electronic switching circuit and a comparator. The electronic switching circuit generates different comparison reference voltages. The comparator compares the comparison reference voltage with the sampled discharge gap voltage and outputs it to the FPGA processing module through an optocoupler.

[0027] As a preferred embodiment of the present invention, the electronic switch circuit is CD4051, the 9th pin, the 10th pin and the 11th pin of the electronic switch circuit serve as the first condition input terminal, the second condition input terminal and the third condition input terminal respectively, and the 3rd pin of the electronic switch circuit serves as the output terminal of the comparison reference voltage.

[0028] As a preferred embodiment of the present application, the comparator is LM311.

[0029] A machining method for constant-speed feeding in the last cutting of wire cutting electrical discharge machining, using the wire cutting electrical discharge machining device as described above, comprising the steps of:

[0030] Step S1, according to the requirements of the physical condition module, the discharge gap voltage parameters and the physical digital code are received by the FPGA processing module to form a preset discharge condition, the host computer issues an instruction to generate discharge parameters, and outputs to the discharge module, and the discharge module discharges;

[0031] Step S2, a comparison reference voltage is set in the discharge gap processing module, the discharge gap voltage is sampled by the discharge gap processing module, and the comparison reference voltage and the sampled discharge gap voltage are compared to determine the current generated tool sequence information, which is output to the FPGA processing module;

[0032] Step S3, according to the physical digital code generated by the physical condition module and the tool sequence signal generated by the discharge gap processing module, if it is determined that the tool sequence signal at this time is the last time of tool correction, the constant-speed feeding value at the last time of tool correction is generated by the physical condition module, and the constant-speed feeding value is used as the feeding speed for tool correction machining;

[0033] Step S4, the host computer outputs the feeding signal to the workbench driving pulse according to the constant-speed feeding value sent by the FPGA processing module, and drives the workbench to feed.

[0034] Compared with the prior art, the present application has the following beneficial effects:

[0035] The method for constant-speed feeding in the last cutting in the multiple cutting of the wire cutting electrical discharge machining has the following advantages: by detecting the discharge state and the preset physical condition, the constant-speed feeding is generated by feedback to the FPGA control system, the random interference of multiple uncertain factors in the external environment is overcome, and excellent products are processed. BRIEF DESCRIPTION OF DRAWINGS

[0036] In order to more clearly illustrate the scheme in the present application, the following will briefly introduce the drawings needed to be used in the embodiment description. Obviously, the drawings in the following description are some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0037] Figure 1 It is a working schematic diagram of the first cutting in the existing wire cutting electrical discharge machining process, and the relative position of the molybdenum wire and the workpiece is shown at this time;

[0038] Figure 2This is a schematic diagram of the first trimming process in the existing wire EDM process, showing the relative positions of the molybdenum wire and the workpiece.

[0039] Figure 3 This is a schematic diagram of the second trimming process in the existing wire-cut EDM process, showing the relative positions of the molybdenum wire and the workpiece.

[0040] Figure 4 A schematic diagram of the state of the discharge gap voltage during the conventional wire-cut electric discharge machining process;

[0041] Figure 5 The present invention is a circuit diagram of a gap voltage average detection circuit in an existing wire-cut electric discharge machining process;

[0042] Figure 6 The present invention is a circuit diagram of a gap voltage peak detection circuit in an existing wire-cut electric discharge machining process;

[0043] Figure 7 This is a schematic diagram of module connections for a wire-cut electric discharge machining device according to the present invention;

[0044] Figure 8 for Figure 7 A circuit diagram of a discharge module of a wire-cut electric discharge machining device;

[0045] Figure 9 for Figure 7 Circuit diagram of the discharge gap processing module of the wire-cut electric discharge machining device. Implementation Method

[0046] In order to enable those skilled in the art to better understand the solutions of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the embodiments described 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 making creative efforts should fall within the scope of protection of the present invention.

[0047] like Figure 7 As shown, the wire-cut electric discharge machining device comprises:

[0048] a discharge module 1, wherein the discharge module 1 discharges according to a discharge parameter;

[0049] a discharge gap processing module 3, which samples the discharge gap voltage during wire-cut electric discharge machining and performs proportional processing on the sampled discharge gap voltage to generate a discharge gap voltage parameter;

[0050] a physical condition module 7, which generates a physical digital code from the physical parameters of the workpiece 8, the physical parameters of the cutting fluid, the physical parameters of the molybdenum wire 2, and the physical parameters of the machine tool;

[0051] an FPGA processing module 4, the FPGA processing module 4 receiving the discharge gap voltage parameter and the physical digital code;

[0052] A host computer 5 instructs the FPGA processing module 4 to operate on the discharge gap voltage parameter and the physical digital code, and generates a constant feed signal, which is fed back to the host computer 5. The host computer 5 instructs a servo amplifier according to the feed signal, and the servo amplifier drives a workbench 6 to feed.

[0053] It should be noted that the workpiece 8 is characterized by its material and height, the cutting fluid is characterized by its type and degree of contamination, the molybdenum wire 2 is characterized by its diameter, and the machine tool is characterized by its rigidity value during movement.

[0054] The physical digital code is further explained below.

[0055] Regarding the physical parameters of workpiece 8 , the height of the workpiece is categorized numerically as follows: 0-20mm is 1, 20-40mm is 2, 40-80mm is 3, 80-150mm is 4, 150-250mm is 5, 250-500mm is 6, 500-800mm is 7, and 800mm and above is 8. These eight conditions can be represented using three digits. The material of the workpiece is categorized numerically as follows: mold steel is 1, brass is 2, copper is 3, aluminum is 4, stainless steel is 5, castings are 6, cemented carbide is 7, and low-conductivity materials are 8. Similarly, these eight conditions can be represented using three digits.

[0056] Regarding the physical parameters of the cutting fluid, the classification of cutting fluid (expressed by numbers) is as follows: water-based is 1, oil-based is 2, concentration greater than 10% is 3, and conductivity greater than 10us / cm is 4. Similarly, 4 digits are needed to represent the 4 states.

[0057] Regarding the physical parameters of molybdenum wire 2, the classification of the state of the molybdenum wire (expressed by numbers) is that if the diameter of the molybdenum wire is greater than 0.17mm, it is 1. Similarly, one digit can be used to represent two states.

[0058] As for the physical parameters of the machine tool, the physical parameters of the machine tool are classified as follows: the XY worktable is a V-flat guide rail, which is 1; the XY worktable is a linear guide rail, which is 2; the C-type wire rack is 3; and the tuning fork type is 4. 4 digits are required to represent the 4 states.

[0059] The above physical parameters are sent to the FPGA processing module 4 in the form of code for processing to generate a corresponding constant cutting speed.

[0060] In addition, the FPGA processing module 4 outputs the discharge parameter and controls the discharge module 1 .

[0061] In addition, the discharge gap processing module 3 generates a discharge gap voltage parameter, representing the discharge gap voltage as a voltage signal. The magnitude of this signal only indicates the size of the molybdenum wire's facing dimension and indirectly indicates the last trimming operation. It typically serves as a feed signal for roughing (the first cut), rough trimming (the first trimming operation), and fine trimming (the first trimming operation) during EDM. Furthermore, the size of the molybdenum wire's facing dimension determines the magnitude of the discharge gap voltage. During the first cut, the molybdenum wire's facing dimension is equal to the wire diameter of 0.18 mm. This indicates a normal discharge state, with low short-circuit rate and no-load rate, and a low normal discharge gap voltage. During the second cut, the molybdenum wire's facing dimension is approximately 0.05 mm, with a high no-load rate and a high normal discharge gap voltage. During the third cut, the molybdenum wire's facing dimension is approximately 0.01 mm, with the highest no-load rate and the highest normal discharge gap voltage. This allows the determination of the cut number.

[0062] like Figure 8 As shown, Figure 7 Circuit diagram of the discharge module 1 in FIG.

[0063] The discharge module 1 consists of a pair of complementary transistors, namely transistor T1-1 and transistor T1-2, which form a push-pull circuit, generating a strong driving current and a fast-wire discharge loop, completing the rapid opening and closing of the field-effect transistor QV1, thereby generating a discharge pulse (discharge through the dielectric) and a pause pulse (deionization, restoration of dielectric insulation, preparation for the next discharge) between the workpiece 8 and the molybdenum wire 2.

[0064] Specifically, in the discharge module 1, BSV1 is a pre-amplification shaping circuit that performs impedance matching, shaping, and amplification on the signal from the host computer; a push-pull circuit is formed by a pair of complementary transistors, namely transistor T1-1 and transistor T1-2; in the positive level stage of the signal, transistor T1-1 is turned on, and the D12V power supply quickly charges the field effect transistor QV1 through the diode DV11 and the resistor RV12; in the negative level (0 level) stage of the signal, transistor T1-1 is turned off, transistor TV1-2 is turned on, and the field effect transistor QV1 quickly discharges the field effect transistor QV1 through the resistor RV12; the resistor RV1 is a current limiting resistor, and the diode DV12 is a reverse peak elimination diode.

[0065] like Figure 9 As shown, Figure 7 Circuit diagram of the discharge gap processing module 3 in FIG.

[0066] When performing the first, second, and third knife trimming operations with different numbers of cuts, the discharge gap voltage is often different. Generally, the discharge gap voltage is higher when the number of cuts is later.

[0067] The discharge gap processing module 3 includes an electronic switch circuit U7 and a comparator U3. The electronic switch circuit U7 generates different comparison reference voltages. The comparator U3 compares the comparison reference voltage with the sampled discharge gap voltage and outputs the result to the FPGA processing module 4 through a photocoupler.

[0068] Specifically, depending on different physical conditions, such as workpiece material, workpiece height, and cooling medium, pins 9, 10, and 11 of the electronic switch circuit U7 serve as the first condition input terminal A1, the second condition input terminal A2, and the third condition input terminal A3. Consequently, a comparison reference voltage under different conditions is obtained at pin 3 of the electronic switch circuit U7. This comparison reference voltage is fed to the non-inverting input of the comparator U3, while the inverting input of the comparator U3 is derived from the sampled discharge gap voltage VIN1.

[0069] The comparator U3 compares the reference voltage with the discharge gap voltage VIN1 sampled from the outside to determine which cut is being processed, and then outputs it to the FPGA processing module 4 after optical coupling isolation.

[0070] The following describes the working process of the wire-cut EDM device, which includes the following steps:

[0071] Step S1: According to the requirements of the physical condition module 7, the FPGA processing module 4 receives the discharge gap voltage parameter and the physical digital code to form a preset discharge condition. The host computer 5 issues an instruction to generate the discharge parameter and outputs it to the discharge module 1, which then performs discharge.

[0072] Step S2: Setting a comparison reference voltage in the discharge gap processing module 3, the discharge gap processing module 3 samples the discharge gap voltage, and compares the comparison reference voltage with the sampled discharge gap voltage, thereby determining the current number of knife repairs, i.e., knife sequence information, and outputting it to the FPGA processing module 4;

[0073] Step S3: The FPGA processing module 4 generates a constant feed rate value for the last trimming operation, for example, the third trimming operation, based on the external conditions (i.e., the physical digital code) generated by the physical condition module 7 and the cutter sequence signal generated by the discharge gap processing module 3. If the cutter sequence signal is determined to be the last trimming operation, for example, the third trimming operation, the physical condition module 7 generates a constant feed rate value for the last trimming operation and uses this constant feed rate value as the feed rate for trimming operation.

[0074] Step S4, the host computer 5 outputs the feeding signal to the worktable 6 according to the constant feeding value sent by the FPGA processing module 4 to drive the pulse of the worktable 6, and drives the worktable 6 to feed.

[0075] The method for constant-speed feeding in the last time of multiple cutting in the wire-cut electrical discharge machining has the following advantages: through detecting the discharge state and preset physical conditions, feedback to the FPGA control system, constant-speed feeding is generated, random interference of multiple uncertain factors in the outside world is overcome, and excellent products are processed.

[0076] Obviously, the above-described embodiments are only some of the embodiments of the present application, rather than all the embodiments, and the preferred embodiments of the present application are given in the drawings, but do not limit the patent scope of the present application. The present application can be implemented in many different forms, and conversely, the purpose of providing these embodiments is to make the disclosure of the present application more thorough and comprehensive. Although the present application is described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions recorded in the foregoing specific embodiments, or equivalently replace some of the technical features. Any equivalent structure made by using the content of the present application specification and drawings, directly or indirectly used in other related technical fields, is also within the patent protection scope of the present application.

Claims

1. A wire-cut electric discharge machining device, characterized in that: The wire-cut electric discharge machining device comprises: a discharge module (1), wherein the discharge module (1) performs discharge according to a discharge parameter; a discharge gap processing module (3), wherein the discharge gap processing module (3) samples the discharge gap voltage during wire-cut electric discharge machining, and performs proportional processing on the sampled discharge gap voltage to generate a discharge gap voltage parameter; a physical condition module (7), wherein the physical condition module (7) generates a physical digital code from the physical parameters of the workpiece (8), the physical parameters of the cutting fluid, the physical parameters of the molybdenum wire (2), and the physical parameters of the machine tool; an FPGA processing module (4), the FPGA processing module (4) receiving the discharge gap voltage parameter and the physical digital code; A host computer (5), the host computer (5) instructs the FPGA processing module (4) to calculate the discharge gap voltage parameter and the physical digital code, and generates a constant feed signal, the feed signal is fed back to the host computer (5), the host computer (5) instructs a servo amplifier according to the feed signal, the servo amplifier drives a workbench (6) to feed, the host computer (5) feeds the workbench (6) through a servo amplifier according to the feed signal, the representation of the workpiece (8) is the material of the workpiece (8) and the height of the workpiece (8), the representation of the cutting fluid is the type of cutting fluid and the cutting The contamination degree of the cutting fluid, the diameter of the molybdenum wire (2), the rigidity value of the machine tool during movement, the FPGA processing module (4) outputs the discharge parameters and controls the discharge module (1), the discharge module (1) is a complementary transistor push-pull circuit, the discharge gap processing module (3) includes an electronic switch circuit (U7) and a comparator (U3), the electronic switch circuit (U7) generates different comparison reference voltages, the comparator (U3) compares the comparison reference voltage with the sampled discharge gap voltage, and outputs the comparison reference voltage to the FPGA processing module (4) through a photoelectric coupler.

2. The wire-cut electric discharge machining device according to claim 1, wherein: The electronic switch circuit (U7) is a CD4051, the 9th pin, the 10th pin and the 11th pin of the electronic switch circuit (U7) serve as a first condition input terminal (A1), a second condition input terminal (A2) and a third condition input terminal (A3), respectively, and the 3rd pin of the electronic switch circuit (U7) serves as an output terminal for a comparison reference voltage.

3. The wire-cut electric discharge machining device according to claim 1, wherein: The comparator (U3) is LM311.

4. A method for performing a final cut of a cutting process using the wire-cut electric discharge machining apparatus as claimed in claim 1 with a constant feed rate, comprising the steps of: Step S1: According to the requirements of the physical condition module (7), the FPGA processing module (4) receives the discharge gap voltage parameter and the physical digital code to form a preset discharge condition. The host computer (5) issues an instruction to generate a discharge parameter, which is output to the discharge module (1). The discharge module (1) performs discharge. Step S2: setting a comparison reference voltage in the discharge gap processing module (3); the discharge gap processing module (3) samples the discharge gap voltage and compares the comparison reference voltage with the sampled discharge gap voltage, thereby determining the currently generated blade sequence information and outputting it to the FPGA processing module (4); Step S3, the FPGA processing module (4) generates the physical digital code generated by the physical condition module (7) and the knife sequence signal generated by the discharge gap processing module (3). If it is determined that the knife sequence signal at this time is the last knife repair, the physical condition module (7) generates a constant speed feed value for the last knife repair, and uses this constant speed feed value as the feed speed for knife repair processing; Step S4: The host computer (5) outputs a feed signal to the workbench (6) driving pulse according to the constant speed feed value sent by the FPGA processing module (4), thereby driving the workbench (6) to feed.

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