Wire electrode discharge machining device and wire electrode discharge machining method

Abstract

The present invention provides a wire-electrode discharge machining device and a wire-electrode discharge machining method that can minimize the reduction in machining speed and improve machining accuracy. The present invention provides a wire-electrode discharge machining device comprising a wire electrode, an upper guide assembly, and a lower guide assembly. The upper guide assembly comprises an upper wire-electrode guide, an upper current-carrying element, and a current-carrying element moving device. The lower guide assembly comprises a lower wire-electrode guide and a lower current-carrying element. The upper current-carrying element and the lower current-carrying element are configured to contact the wire electrode and supply power to the wire by moving from an initial position in a horizontal uniaxial direction, where the upper current-carrying element is not in contact with the wire electrode. The current-carrying element moving device is configured to move the upper current-carrying element from the initial position in the horizontal uniaxial direction by a predetermined offset amount, the offset amount being set based on machining conditions, the machining conditions including at least one of a condition of the wire electrode, a surface roughness required for a machining surface of a workpiece, and a condition of the workpiece.

Description

Technical Field

[0001] The present invention relates to a wire discharge machining device for performing discharge machining on a workpiece using a wire electrode, and a wire discharge machining method. Background Art

[0002] In wire EDM, discharges are generated in the gap between the wire electrode and the workpiece, machining the workpiece. In a typical wire EDM device, the wire moves along a predetermined path during machining, guided by a pair of wire guides positioned vertically across the workpiece. The wire is fed downward relative to the workpiece while moving vertically. Within the guide assembly in which each wire guide is assembled, a current-carrying element connected to a power source is located. This current-carrying element contacts the wire electrode, supplying power to the wire.

[0003] The material and outer diameter of the wire electrode are selected based on the conditions of the workpiece, the required machining accuracy, and the machining efficiency. The wire's travel speed and the tension applied to the wire during machining are also set. Patent Document 1 (Japanese Patent No. 5088975) discloses a wire discharge machining device designed to prevent wire breakage while improving machining accuracy and efficiency.

[0004] As mentioned above, the wire electrode is powered by a pair of current-carrying bodies positioned above and below the workpiece, which contact the wire. When the current-carrying bodies contact the wire, friction can cause cracks on the wire surface or scratches, resulting in wire debris. Since the wire is fed vertically downward relative to the workpiece, if friction from the upper current-carrying body causes cracks or wire debris on the wire surface, electrical discharge occurs between the wire surface and the workpiece, creating unevenness or streaks on the machined surface, reducing machining accuracy.

[0005] On the other hand, if the contact between the wire electrode and the upper current-carrying element is weakened or eliminated to reduce friction, the power supply will decrease, leading to a reduction in machining speed. Furthermore, even if the degree of contact remains the same, adjusting the wire electrode material and other conditions can sometimes reduce the occurrence of cracks or wire debris. Furthermore, even if cracks or wire debris cause unevenness or streaks on the machined surface, these problems can sometimes be avoided by adjusting the required surface roughness. Therefore, the degree of contact with the current-carrying element must be appropriately adjusted according to the machining conditions. Summary of the Invention

[0006] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a wire electric discharge machining device and a wire electric discharge machining method that can minimize a decrease in machining speed while improving machining accuracy.

[0007] According to the present invention, there is provided a wire electrode discharge machining device comprising an electrode wire, an upper guide assembly, and a lower guide assembly, characterized in that the upper guide assembly and the lower guide assembly are respectively arranged on the upper side and the lower side of the workpiece with the workpiece interposed therebetween in the vertical direction, the upper guide assembly comprising an upper wire electrode guide portion, an upper current-carrying body, and a current-carrying body moving device, the lower guide assembly comprising a lower wire electrode guide portion and a lower current-carrying body, the electrode wire being guided by the upper wire electrode guide portion and the lower wire electrode guide portion to perform electrical discharge machining on the workpiece, the upper current-carrying body and the lower current-carrying body being configured to contact the wire electrode and supply power to the wire electrode by moving from an initial position not in contact with the wire electrode in a horizontal uniaxial direction, the current-carrying body moving device being configured to move the upper current-carrying body from the initial position in the horizontal uniaxial direction by a predetermined offset amount, the offset amount being set based on machining conditions, the machining conditions including at least one of a condition of the wire electrode, a surface roughness required for a machining surface of the workpiece, and a condition of the workpiece.

[0008] In the wire discharge machining device according to the present invention, an offset amount, which is the amount of movement in the horizontal uniaxial direction from the initial position of the upper current-carrying element, is set based on processing conditions including at least one of the conditions of the wire electrode, the required surface roughness of the workpiece's machined surface, and the conditions of the workpiece. With this configuration, for example, the offset amount can be set based on factors such as the likelihood of cracks or wire chips due to the wire electrode's material, the tolerance for unevenness or streaks on the machined surface, and the likelihood of unevenness or streaks due to the workpiece's material. By adjusting the degree of contact with the upper current-carrying element, the offset amount can minimize reductions in machining speed and improve machining accuracy.

[0009] Various embodiments of the present invention are described below. The embodiments described below can be combined with each other.

[0010] Preferably, the wire discharge machining device includes a processing condition setting device and an offset setting device, the processing condition setting device sets the processing condition, the offset setting device sets the offset based on data representing the relationship between the processing condition and the offset, and according to the processing condition set by the processing condition setting device, and the current-carrying body moving device is configured to move the upper current-carrying body by the offset set by the offset setting device.

[0011] Preferably, the condition of the wire electrode includes at least one of a material and an outer diameter of the wire electrode.

[0012] It is preferable that the conditions of the workpiece include at least one of the material and thickness of the workpiece.

[0013] The offset amount is preferably set so that the offset amount when the surface roughness is equal to or less than a predetermined threshold value is smaller than the offset amount when the surface roughness is greater than the threshold value.

[0014] Preferably, the offset amount when the surface roughness is equal to or less than the threshold value is set so that the upper current-carrying body comes into contact with the wire electrode.

[0015] Preferably, the offset amount when the surface roughness is equal to or less than the threshold value is set so that the upper current-carrying body and the wire electrode do not come into contact with each other.

[0016] Preferably, the condition of the wire electrode includes the outer diameter of the wire electrode, and the offset amount when the outer diameter is equal to or greater than a predetermined threshold value is set to be smaller than the offset amount when the outer diameter is less than the threshold value.

[0017] It is preferable that the offset amount when the outer diameter is equal to or greater than the threshold value be set so that the upper current-carrying body comes into contact with the wire electrode.

[0018] In addition, according to another aspect of the present invention, there is provided an electrode wire discharge machining method, characterized in that it comprises an offset setting process and a current-carrying body moving process, the electrode wire is guided by an upper electrode wire guide part and a lower electrode wire guide part respectively assembled in an upper guide assembly and a lower guide assembly respectively arranged on the upper side and the lower side across the workpiece in the vertical direction, and discharge-machines the workpiece, the upper guide assembly and the lower guide assembly respectively comprising an upper current-carrying body and a lower current-carrying body, the upper current-carrying body and the lower current-carrying body being configured to move from an initial position not in contact with the electrode wire to a position where the electrode wire is moved. The upper side current-carrying body is moved in the horizontal one-axis direction to contact the electrode wire and power is supplied to the electrode wire. In the offset setting, the offset of the upper side current-carrying body is set based on the processing conditions. The offset of the upper side current-carrying body is the movement amount of the upper side current-carrying body from the initial position to the horizontal one-axis direction. In the current-carrying body moving process, the upper side current-carrying body is moved from the initial position to the horizontal one-axis direction by the offset. The processing conditions include the conditions of the electrode wire, the surface roughness required for the processing surface of the workpiece, and at least one of the conditions of the workpiece. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a conceptual diagram showing a wire electric discharge machining device 100 according to an embodiment of the present invention.

[0020] Figure 21 and 2 are diagrams for explaining the wire electrode guide mechanism 4 , showing a state where the upper current-carrying body 44 a and the lower current-carrying body 44 b are in their initial positions.

[0021] Figure 3 4 is a diagram for explaining the wire electrode guide mechanism 4 , and shows a state in which the upper current-carrying body 44 a and the lower current-carrying body 44 b are in contact with the wire electrode 2 .

[0022] Figure 4 4 is a diagram for explaining the wire electrode guide mechanism 4 , and shows a state in which the upper current-carrying body 44 a is not in contact with the wire electrode 2 , while the lower current-carrying body 44 b is in contact with the wire electrode 2 .

[0023] Figure 5 It is a block diagram showing the structure of the control device 7.

[0024] Figure 6 This is a flowchart showing a wire discharge machining method according to an embodiment of the present invention.

[0025] exist Figure 7 7A to 7D show images of the processed surfaces of Examples 1 to 3 and Comparative Example 1.

[0026] Explanation of symbols

[0027] 1: Wire feeding mechanism, 2: Wire, 3: Automatic wiring device, 4: Wire guide mechanism, 5: Wire recovery mechanism, 6: Power supply unit, 7: Control unit, 8: Compressed air supply unit, 9: Machining fluid supply unit, 10: Machining gap, 11: Reel, 12: Wire bobbin, 13: Braking device, 14: Servo pulley, 15: Tension applying device, 15a: Feed roller, 15b: Feed motor, 15c: Tension detector, 15d: Pinch roller, 16: Wire breakage detector, 21: Bed, 22: Worktable, 31: Conduit, 32: Lifting device, 35c: Current-carrying body support member, 40 mm: Thickness, 41a: Upper guide assembly, 41b: Lower guide assembly, 42a: Housing, 42b: Housing, 43a: Upper wire guide , 43b: lower side wire guide, 44a: upper side current-carrying body, 44b: lower side current-carrying body, 45: current-carrying body moving device, 45a: ball screw shaft, 45b: nut, 45c: current-carrying body supporting component, 45d: motor, 46: current-carrying body moving device, 46a: ball screw shaft, 46b: nut, 46d: motor, 51: steering roller, 52: conveying pipe, 53: suction device, 54: winding device, 54a: winding roller, 54b: clamping roller, 54c: winding motor, 55: wire cutting machine, 56: bucket, 71: input device, 72: numerical control device, 73: processing condition setting device, 74: offset setting device, 75: storage device, 76: movement control device, 100: wire discharge machining device, W: workpiece. DETAILED DESCRIPTION

[0028] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. Various features shown in the embodiments described below can be combined with each other, and each feature independently constitutes the present invention.

[0029] 1. Wire EDM device

[0030] 1.1. Overall structure

[0031] Figure 1 FIG is a conceptual diagram showing a wire discharge machining device 100 according to an embodiment of the present invention. Figure 1As shown, a wire EDM device 100 in this embodiment includes a wire electrode 2. The wire electrode 2 is tensioned and spanned between an upper wire guide 43a and a lower wire guide 43b, which are arranged vertically across a workpiece W. The wire EDM device 100 includes a bed 21 mounted on a surface on which the device is installed, and a horizontally movable table 22 mounted on the bed 21. The workpiece W is placed on the table 22. The wire electrode 2 is inserted through a lower hole formed in the workpiece W, and discharge is generated in a machining gap 10 formed between the wire electrode 2 and the workpiece W, thereby machining the workpiece W.

[0032] The wire EDM device 100 includes a wire feeding mechanism 1, an automatic wiring device 3, a wire guiding mechanism 4, and a wire collecting mechanism 5, sequentially arranged along the travel path of the wire electrode 2. Furthermore, the wire EDM device 100 includes a power supply 6, a compressed air supply 8, and a machining fluid supply 9. In the following description, the side relatively close to the wire feeding mechanism 1 along the travel path of the wire electrode 2 is considered upstream, and the side relatively close to the wire collecting mechanism 5 is considered downstream. The rotational direction of the rotating body constituting the wire EDM device 100 is defined as the forward rotational direction when the wire electrode 2 moves from upstream to downstream, and the reverse rotational direction is defined as the reverse rotational direction.

[0033] 1.2. Wire electrode supply mechanism 1

[0034] The wire feeding mechanism 1 is configured to continuously feed new wire electrode 2 along a predetermined path and primarily comprises a reel 11, a brake device 13, a servo pulley 14, a tensioning device 15, and a wire breakage detector 16. A wire spool 12, which stores the wire electrode 2, is mounted on the reel 11. As the wire spool 12 rotates in the forward direction, new wire electrode 2 is continuously drawn from the spool 12. The brake device 13 is, for example, a brake motor such as a hysteresis motor or an electromagnetic brake such as an electromagnetic clutch. The brake device 13 applies torque in the reverse direction to the reel 11, preventing the wire spool 12 from idling and thus preventing the wire electrode 2 from slacking.

[0035] The servo pulley 14 is positioned between the reel 11 and the tensioning device 15 along the path of travel of the wire electrode 2. Its own weight applies a constant load vertically downward to the wire electrode 2. The servo pulley 14 is configured to be movable in the vertical direction. As a result, the servo pulley 14 moves vertically in response to slight fluctuations in the tension of the wire electrode 2, absorbing the slight vibrations that occur in the wire electrode 2 unwound from the wire spool 12. A wire breakage detector 16 is positioned along the path of travel of the wire electrode 2 after passing through the servo pulley 14. The wire breakage detector 16 is configured to detect wire breakage in the wire electrode 2 and may be comprised of, for example, a limit switch.

[0036] The tension applying device 15 is configured to cooperate with the electrode wire recovery mechanism 5 to apply a predetermined tension to the electrode wire 2, and comprises a feed roller 15a, a feed motor 15b, a tension detector 15c, and a pinch roller 15d. The feed roller 15a is driven to rotate by the feed motor 15b. The electrode wire 2 is pressed against the outer peripheral surface of the feed roller 15a by the pinch roller 15d to obtain a driving force for movement. The electrode wire 2 moves along the outer peripheral surface of the feed roller 15a using a plurality of rollers including the pinch roller 15d, thereby preventing slack and breakage while allowing the electrode wire 2 to move smoothly. The tension detector 15c is configured to detect the tension of the electrode wire 2 and is, for example, composed of a strain gauge.

[0037] The feed motor 15b is a servo motor. It is servo-controlled based on the tension detection result from the tension detector 15c. This ensures that the tension of the wire electrode 2 remains stable even at low set tension values, more reliably preventing the wire electrode 2 from slacking or breaking. Furthermore, the feed motor 15b can be controlled based on the torque of the winding device 54 of the wire electrode recovery mechanism 5.

[0038] With the wire electrode 2 stretched between the upper wire guide 43a and the lower wire guide 43b, a predetermined tension can be applied to the wire electrode 2 by adjusting the rotational speed difference between the feed roller 15a and the take-up roller 54a of the take-up device 54. When wiring the wire electrode 2, the feed roller 15a is set to rotate in the forward direction at a constant speed, the tip of the wire electrode 2 is inserted into the lower hole, and the retrieving mechanism 5 retracts the wire electrode 2. To rewire the wire electrode 2, the feed roller 15a is rotated in the reverse direction at a constant speed, and the wire electrode 2 is lifted to a predetermined position.

[0039] 1.3. Automatic wiring device 3

[0040] The automatic wiring device 3 allows the front end of the electrode wire 2 fed by the electrode wire feeding mechanism 1 to pass through the lower hole formed on the workpiece W, and automatically sets the electrode wire 2 between the upper electrode wire guide 43a and the lower electrode wire guide 43b. The automatic wiring device 3 includes a guide tube 31 and a lifting device 32. The guide tube 31 guides the electrode wire 2 from the upstream side to the upper electrode wire guide 43a in a manner that does not deviate from the prescribed moving path. Here, the structure in which the guide tube 31 is arranged at the upper limit position is as shown in FIG. Figure 1 The guide tube 31 is configured to be movable in the vertical direction by the lifting device 32 between this upper limit position and a lower limit position where the lower end of the guide tube 31 is located directly above the upper surface of the upper wire electrode guide 43a. The lifting device 32 moves the guide tube 31 to the upper limit position when the wire electrode 2 is burned or cut, and moves the guide tube 31 to the lower limit position when the tip of the wire electrode 2 is inserted through the lower hole.

[0041] Furthermore, a wire vibrating device (not shown) is installed directly above the inlet of the conduit 31. The wire vibrating device uses compressed air supplied by the compressed air supply device 8 to directly or indirectly apply pressure to the wire electrode 2 along its travel path. This allows the wire electrode 2 to move slightly up and down, making it easier to pass through the lower hole.

[0042] 1.4. Wire guide mechanism 4

[0043] Figures 2 to 4 4 is a diagram illustrating the electrode wire guide mechanism 4. Figure 1 and Figure 2 As shown, the electrode wire guide mechanism 4 includes an upper guide component 41a and a lower guide component 41b, which are respectively arranged on the upper and lower sides of the workpiece W in the vertical direction. It is configured to position the electrode wire 2 near the workpiece W and guide it to a specified moving path.

[0044] The upper guide assembly 41a comprises a housing 42a, an upper wire guide 43a, an upper current-carrying element 44a, a current-carrying element moving device 45, and a nozzle (not shown). These components are assembled within the housing 42a. The lower guide assembly 41b comprises a housing 42b, a lower wire guide 43b, a lower current-carrying element 44b, a current-carrying element moving device 46, and a nozzle (not shown). These components are assembled within the housing 42b. The upper wire guide 43a and the lower wire guide 43b are die-shaped guides. Each die guide has a guide hole, into which the wire electrode 2 is inserted with a clearance of several microns from the inner surface of the guide hole, and is guided vertically.

[0045] The wire EDM device 100 is equipped with a so-called taper mechanism (not shown) that allows either the upper wire guide 43a or the lower wire guide 43b to move horizontally relative to the other. This relative movement allows the wire 2 to be machined while tilted relative to the workpiece W. Furthermore, nozzles provided on the upper guide assembly 41a and the lower guide assembly 41b spray pressurized machining fluid supplied by the machining fluid supply device 9 into the machining gap 10.

[0046] The upper guide assembly 41a and the lower guide assembly 41b respectively house an upper current-carrying body 44a and a lower current-carrying body 44b for supplying power from the power supply device 6 to the electrode wire 2. The upper current-carrying body 44a and the lower current-carrying body 44b can be moved in a direction perpendicular to the direction in which the electrode wire 2 is stretched (e.g., Figure 1In this embodiment, the conductive body moving device 45 for moving the upper conductive body 44a in the A-axis direction is assembled in the upper guide assembly 41a, and the conductive body moving device 46 for moving the lower conductive body 44b in the A-axis direction is assembled in the lower guide assembly 41b.

[0047] like Figure 2 As shown, the current-carrying member moving device 45 includes a ball screw shaft 45a arranged parallel to the A-axis, a nut 45b threadedly engaged with the ball screw shaft 45a, a current-carrying member support member 45c fixed to the nut 45b, and a motor 45d. The upper current-carrying member 44a is disposed at the front end of the current-carrying member support member 45c. When the motor 45d is driven under the control of the movement control device 76 (described later), the ball screw shaft 45a rotates, and the nut 45b moves forward and backward with this rotation. As a result, the upper current-carrying member 44a reciprocates in the A-axis direction as the nut 45b moves forward and backward. It should be noted that the current-carrying member moving device 45 is not limited to the above structure; any other structure is acceptable as long as it can move the upper current-carrying member 44a in a horizontal, uniaxial direction. For example, the current-carrying member moving device 455 can be constructed using a fluid pressure cylinder such as a hydraulic cylinder or a pneumatic cylinder, an electric cylinder, a linear motor mechanism, or a rack and pinion mechanism. Furthermore, a locking mechanism may be provided for stopping the upper current-carrying body 44 a after movement at a predetermined position.

[0048] The current-carrying member moving device 46 for moving the lower current-carrying member 44b can be configured in the same manner as the current-carrying member moving device 45 for the upper current-carrying member 44a, or can be configured in a different manner. The current-carrying member moving device 46 according to this embodiment is configured in the same manner as the current-carrying member moving device 45, and includes a ball screw shaft 46a, a nut 46b, a current-carrying member support member 35c, and a motor 46d.

[0049] The power supply device 6 is used to supply power to the electrode wire 2 and the workpiece W. It has an electric discharge machining circuit (not shown) including a DC power supply, a switching element, and a diode to prevent current backflow. The upper side current-carrying body 44a and the lower side current-carrying body 44b are connected to the positive pole of the DC power supply of the power supply device 6. The negative pole of the DC power supply is connected to the workpiece W. The upper side current-carrying body 44a and the lower side current-carrying body 44b are connected to the workpiece W through the upper side current-carrying body 44a and the lower side current-carrying body 44b. Figure 1 and Figure 2 The initial positions A1 and A2 shown as not in contact with the wire electrode 2 are moved in the A-axis direction by a predetermined distance, thereby contacting the wire electrode 2 in a direction substantially perpendicular to the wire electrode 2 (e.g., Figure 3 In the present invention, the distance moved from the initial positions A1 and A2 of the current-carrying bodies 44a and 44b in the horizontal uniaxial direction (the A-axis direction) is referred to as the offset. Figure 3As shown, the movement distance from the initial position A1 of the upper side current-carrying body 44a in the A-axis direction is defined as the offset d1, and the movement distance from the initial position A2 of the lower side current-carrying body 44b in the A-axis direction is defined as the offset d2.

[0050] With one or both of the upper current-carrying element 44a and the lower current-carrying element 44b in contact with the wire electrode 2, the power supply device 6 can repeatedly apply voltage pulses to the machining gap 10 between the wire electrode 2 and the workpiece W through the upper current-carrying element 44a, the lower current-carrying element 44b, and the workpiece W, thereby generating discharge. The greater the offset amounts d1 and d2 of the upper current-carrying element 44a and the lower current-carrying element 44b, the greater the degree of contact with the wire electrode 2, and the smaller the contact resistance at the contact point, the greater the power supply.

[0051] 1.5. Electrode wire recovery mechanism 5

[0052] The wire electrode recovery mechanism 5 recovers the wire electrode 2 consumed during machining from the machining gap 10. The wire electrode recovery mechanism 5 includes a deflection roller 51, a conveying pipe 52, a suction device 53, a winding device 54, a wire cutter 55, and a bucket 56. The wire electrode 2 that has passed through the lower wire guide 43b is redirected horizontally by the deflection roller 51 and inserted into the conveying pipe 52. The wire electrode 2 in the conveying pipe 52 is sucked by the suction device 53, generating a propulsive force.

[0053] The winding device 54 includes a winding roller 54a, a pinch roller 54b, and a winding motor 54c. The wire electrode 2, which has passed through the conveying tube 52, is clamped between the winding roller 54a and the pinch roller 54b of the winding device 54. The winding roller 54a is rotated in the forward direction at a predetermined speed by the winding motor 54c, which is a constant speed motor. This rotates the wire electrode 2 while moving it and pulling it directly above the bucket 56. The pulled wire electrode 2 is appropriately chopped by the wire cutter 55 and stored in the bucket 56.

[0054] 2. Control device 7

[0055] Next, the control device 7 for controlling the operation of the wire electrode discharge machining device 100 will be described. The control device 7 is used to control the overall operation of the wire electrode discharge machining device 100 and the operation of each component device. In the following, only the control related to the present invention in the control operation of the control device 7 will be described. Figure 5 As shown, the control device 7 includes an input device 71 , a numerical control device 72 , and a movement control device 76 .

[0056] It should be noted that the main components of the control device 7 can be implemented by software or by hardware. When implemented by software, various functions can be implemented by the CPU executing a computer program. The program can be stored in a built-in storage unit or in a non-temporary recording medium that can be read by a computer. In addition, it can also be implemented by reading a program stored in an external storage unit, that is, by using a cloud computer. When implemented by hardware, it can be implemented by using various circuits such as ASIC, FPGA or DRP. In this embodiment, various information and concepts including various information are involved, which can be represented by the high and low signal values ​​of a binary bit set consisting of 0 or 1, and obtained by performing communication or calculation in the above-mentioned software or hardware.

[0057] The input device 71 allows the operator to input information required for various processes in the numerical controller 72. It can be configured as a touch panel, keyboard, or mouse. This input information can be used as part of the machining conditions, such as the material and outer diameter of the wire electrode 2, the material and thickness of the workpiece W, and the surface roughness required for the machined surface. This input information is then output to the numerical controller 72.

[0058] The numerical controller 72 generates operation commands for the wire discharge machining device 100 using an NC program storing input information and data related to machining conditions. The numerical controller 72 includes a machining condition setting device 73 , an offset setting device 74 , and a storage device 75 .

[0059] The processing condition setting device 73 sets processing conditions suitable for the required electrical discharge machining. Processing conditions generally include various types of conditions, such as conditions for the wire electrode 2, conditions for the machining surface of the workpiece W, conditions for the workpiece W, electrical machining conditions, and other conditions categorized by first or second cutting. The processing condition setting device 73 sets these processing conditions by reading the processing conditions when they are stored in the NC program stored in the storage device 75, or based on input information input to the input device 71. The set processing conditions can be output to the control unit of each device and mechanism constituting the wire electrode electrical discharge machining device 100 in the form of an action instruction signal or action instruction value data. In addition, at least a portion of the set processing conditions is also output to the offset setting device 74.

[0060] The offset setting device 74 sets the offsets d1 and d2 of the upper and lower current-carrying members 44a and 44b based on the processing conditions sent from the processing condition setting device 73. The offset setting device 74 sets the offsets d1 and d2 based on data indicating the relationship between the processing conditions and the offsets d1 and d2, and in accordance with the processing conditions sent from the processing condition setting device 73. For example, a data table indicating a one-to-one correspondence between processing conditions and offsets d1 and d2 may be stored in the storage device 75. The offsets d1 and d2 corresponding to the processing conditions sent from the processing condition setting device 73 may be read from the data table to set the offsets d1 and d2. In another configuration, the offsets d1 and d2 may be set by storing a function in the storage device 75 that calculates the offsets d1 and d2 from the processing conditions as variables and using this function to calculate the offsets d1 and d2. The set offsets d1 and d2 are output to the movement control device 76 as motion command values. It should be noted that the details of setting the offsets d1 and d2 will be described later.

[0061] The storage device 75 stores input information sent from the input device 71 , NC programs, and data tables and functions for setting the offset amounts d1 and d2 .

[0062] The movement control device 76 controls the motors 45d and 46d of the conductive body moving devices 45 and 46 according to the action instructions set and sent by the offset setting device 74, and moves the upper conductive body 44a and the lower conductive body 44b from the initial positions A1 and A2 by the set offsets d1 and d2 respectively.

[0063] The control device 7 outputs operation commands to the control units of the various devices and mechanisms constituting the wire electrical discharge machining apparatus 100 , and receives feedback of actual operation information of the various devices and mechanisms from the control units.

[0064] 3. Offset setting

[0065] Next, the setting of the offset amounts d1 and d2 of the upper current-carrying body 44 a and the lower current-carrying body 44 b will be described in detail.

[0066] In this embodiment, the offset amounts d1 and d2 of the upper and lower current-carrying members 44a and 44b are set based on various machining conditions. Specifically, the offset amount setting device 74 sets the offset amounts d1 and d2 based on the machining conditions transmitted from the machining condition setting device 73. Here, the offset amount d1 of the upper current-carrying member 44a is set based on at least one of the machining conditions, including the conditions of the wire electrode 2, the surface roughness required for the machined surface of the workpiece W, and the conditions of the workpiece W.

[0067] Regarding the conditions of the wire electrode 2, the material and outer diameter of the wire electrode 2 are examples of conditions that have a particularly significant impact on machining accuracy. The ease with which the surface condition of the wire electrode 2 changes varies depending on the material. For example, a wire electrode 2 made primarily of brass is more susceptible to surface cracks and wire debris than a wire electrode made of other materials, such as tungsten or zinc-plated electrodes. When setting the offset d1 of the upper current-carrying element 44a based on the material of the wire electrode 2, in this embodiment, the offset d1 is set smaller when using a material with a more easily changeable surface condition than when using a material with a less easily changeable surface condition. This weakens or eliminates contact between the wire electrode 2 and the upper current-carrying element 44a when using a material with a more easily changeable surface condition, thereby suppressing the occurrence of cracks and wire debris on the wire electrode 2 surface caused by contact and, consequently, preventing a reduction in machining accuracy. The offset d2 of the lower current-carrying element 44b is set so that the wire electrode 2 is in sufficient contact with the lower current-carrying element 44b.

[0068] The larger the outer diameter of the wire electrode 2, the more likely it is that surface cracks or wire scraps will cause unevenness or streaks on the machined surface of the workpiece W. When the offset d1 of the upper current-carrying element 44a is set based on the outer diameter of the wire electrode 2, in this embodiment, the offset d1 is set to be smaller when the outer diameter of the wire electrode 2 is above a predetermined threshold than when the outer diameter is below the threshold. This reduces or eliminates contact between the wire electrode 2 and the upper current-carrying element 44a when the outer diameter of the wire electrode 2 is large, thereby suppressing the occurrence of surface cracks or wire scraps on the wire electrode 2 due to contact and preventing a decrease in machining accuracy. The offset d2 of the lower current-carrying element 44b is set to ensure sufficient contact between the wire electrode 2 and the lower current-carrying element 44b.

[0069] The threshold value for the outer diameter of the wire electrode 2 used when setting the offset d1 of the upper current-carrying element 44a is preferably set to a range of 0.05 to 0.2 mm, more preferably 0.07 to 0.17 mm. By setting the outer diameter threshold within this range, the effect of the surface condition of the wire electrode 2 on machining accuracy can be minimized.

[0070] Surface roughness is expressed, for example, by indicators such as the maximum height Rz and the arithmetic mean roughness Ra of the processed surface. Maximum height Rz is a surface roughness indicator specified in JIS B 0601-2001. It is calculated by extracting a reference length from the roughness curve in the direction of its mean line and expressing the sum of the peak height of the highest peak and the valley depth of the deepest peak in the extracted portion in micrometers (μm). Arithmetic mean roughness Ra is a surface roughness indicator specified in JIS B 0601-2001. It is calculated by extracting a reference length from the roughness curve in the direction of its mean line and summing the absolute values ​​of the deviations from the mean line of the extracted portion to the measurement curve. The average value is then expressed in micrometers (μm).

[0071] The lower the required surface roughness of the workpiece W, the more pronounced the unevenness or streaks produced on the workpiece W's surface. When the offset amount d1 of the upper current-carrying element 44a is set based on the required surface roughness, in this embodiment, the offset amount d1 is set smaller when the required surface roughness is below a predetermined threshold than when it is above the threshold. This reduces or eliminates contact between the wire electrode 2 and the upper current-carrying element 44a when the required surface roughness is low. This prevents cracks or wire scraps on the wire electrode 2 surface caused by contact, thereby minimizing degradation in machining accuracy. The offset amount d2 of the lower current-carrying element 44b is set to ensure sufficient contact between the wire electrode 2 and the lower current-carrying element 44b.

[0072] The surface roughness threshold used to set the offset d1 of the upper current-carrying element 44a is preferably set to 1 to 3 μm when the maximum height Rz is used as the surface roughness indicator, and preferably to 0.1 to 0.5 μm when the arithmetic mean roughness Ra is used as the surface roughness indicator. More preferably, it is set to 1 to 1.5 μm for the maximum height Rz and 0.1 to 0.3 μm for the arithmetic mean roughness Ra. By setting the surface roughness threshold within this range, the effect of the surface condition of the wire electrode 2 on machining accuracy can be minimized.

[0073] Regarding the conditions of the workpiece W, the material and thickness of the workpiece W are examples of conditions that significantly influence machining accuracy. The ease with which unevenness or streaks are generated on the machined surface due to the surface condition of the wire electrode 2 varies depending on the material of the workpiece W. When setting the offset d1 of the upper current-carrying element 44a based on the material of the workpiece W, in this embodiment, the offset d1 is set smaller when using a material that easily generates unevenness or streaks than when using a material that is less likely to generate unevenness or streaks. This allows the wire electrode 2 to have less contact with the upper current-carrying element 44a, or even eliminate contact, when using a material that easily generates unevenness or streaks on the machined surface. This prevents cracks or wire scraps from forming on the surface of the wire electrode 2 due to contact, thereby minimizing a decrease in machining accuracy. The offset d2 of the lower current-carrying element 44b is set so that the wire electrode 2 is in sufficient contact with the lower current-carrying element 44b.

[0074] Furthermore, the greater the thickness of the workpiece W, the greater the effect of the surface condition of the wire electrode 2 on the machined surface. When the offset amount d1 of the upper current-carrying element 44a is set based on the thickness of the workpiece W, in this embodiment, the offset amount d1 is set to be smaller when the thickness of the workpiece W is above a predetermined threshold than when the thickness is below the threshold. Consequently, when the workpiece W is thick, contact between the wire electrode 2 and the upper current-carrying element 44a becomes weaker or nonexistent, thereby suppressing the formation of cracks or wire scraps on the surface of the wire electrode 2 caused by contact and thus preventing a decrease in machining accuracy. The offset amount d2 of the lower current-carrying element 44b is set to ensure sufficient contact between the wire electrode 2 and the lower current-carrying element 44b.

[0075] As described above, by setting the offset d1 of the upper current-carrying element 44a to a small value under specified machining conditions, the upper current-carrying element 44a can be set to contact the wire electrode 2. In other words, the contact with the wire electrode 2 can be weakened compared to when the machining conditions are not met. For example, when the outer diameter of the wire electrode 2 is above a threshold, the offset d1 can be set so that the upper current-carrying element 44a contacts the wire 2 but is weaker than when the outer diameter is below the threshold. Furthermore, when the required surface roughness of the machined surface is below a threshold, the offset d1 can be set so that the upper current-carrying element 44a contacts the wire 2 but is weaker than when the required surface roughness is greater than the threshold. This weakens the contact with the upper current-carrying element 44a, thereby suppressing cracks and wire scraps on the surface of the wire electrode 2. Furthermore, power can be supplied through the upper current-carrying element 44a, minimizing the reduction in machining speed associated with a reduced power supply.

[0076] On the other hand, if the offset amount d1 of the upper current-carrying body 44a is set to be small under predetermined machining conditions, the upper current-carrying body 44a can be set to be out of contact with the wire electrode 2. Figure 4 In the example, the offset d1 is set to 0, preventing the upper current-carrying element 44a from moving from its initial position A1 and allowing power to flow only from the lower current-carrying element 44b. For example, when the outer diameter of the wire electrode 2 is greater than a threshold, the offset d1 can be set so that the upper current-carrying element 44a and the wire electrode 2 do not contact each other. Alternatively, when the required surface roughness of the machined surface is below a threshold, the offset d1 can be set so that the upper current-carrying element 44a and the wire electrode 2 do not contact each other. This maximizes the effect of suppressing cracks and wire scraps on the surface of the wire electrode 2 as the upper current-carrying element 44a contacts the wire electrode 2.

[0077] It should be noted that the method for setting the offset d1 of the upper current-carrying member 44a is not limited to the above-described embodiment and can be modified in various ways. For example, in the above-described embodiment, the offset d1 is adjusted for each machining condition. However, when multiple machining conditions are considered, that is, when these machining conditions form a specific combination (for example, the wire electrode 2 is made of brass, the outer diameter of the wire electrode 2 is above a predetermined threshold, and the required surface roughness is below a predetermined threshold), the offset d1 of the upper current-carrying member 44a can be set to a smaller value. In this case, data on the optimal offset d1 for the multiple machining condition combinations can be stored in the storage device 75 of the control device 7 in the form of a data table, and the offset setting device 74 can read this data to set the offset d1.

[0078] In addition, the adjustment of the offset d1 of each processing condition as described above can be performed not during the first cutting, but only after the second cutting. In the first cutting as rough processing, processing is performed while retaining the margin required for fine processing after the second cutting. Compared with fine processing, the precision required for the processed surface is low. After the second cutting, high processing precision is required, especially in PIKA processing (mirror processing). Therefore, during the first cutting, the upper side current-carrying body 44a and the lower side current-carrying body 44b are fully in contact with the electrode wire 2. In this way, by weakening the contact between the electrode wire 2 and the upper side current-carrying body 44a after the second cutting or making it non-contact, the reduction in processing precision is suppressed, so that the reduction in processing speed can be limited to a minimum.

[0079] 4. Wire EDM method for workpiece W

[0080] Next, a wire electric discharge machining method of a workpiece W using the wire electric discharge machining device 100 according to the present embodiment will be described. Figure 6 This is a flowchart showing a wire discharge machining method according to an embodiment of the present invention.

[0081] First, the operator inputs information required for various processes into the numerical controller 72, and the input device 71 of the control device 7 receives the input information (step S1-1). The input information is output to the numerical controller 72, and various machining conditions are set by the machining condition setting device 73 (step S1-2). The set machining conditions are output as operation commands to the control units of the various devices and mechanisms that constitute the wire discharge machining apparatus 100. In addition, at least some of the machining conditions are also output to the offset setting device 74.

[0082] The offset setting device 74 sets the offsets d1 and d2 of the upper side current-carrying body 44a and the lower side current-carrying body 44b based on the processing conditions sent from the processing condition setting device 73. In this embodiment, in the first cutting, in order to ensure a sufficient processing speed, the offsets d1 and d2 are set so that the upper side current-carrying body 44a and the lower side current-carrying body 44b are in full contact with the electrode wire 2 (step S1-3). In the second cutting, the offset d1 of the upper side current-carrying body 44a is set based on the processing conditions including the conditions of the electrode wire 2, the surface roughness required for the processing surface of the workpiece W, and at least one of the conditions of the workpiece W. Figure 6 The figure shows an example of adjusting the offset d1 based on the outer diameter of the wire electrode 2. The outer diameter of the wire electrode 2 is compared with a predetermined threshold value (step S2-1). If the threshold value is exceeded, the offset d1 is adjusted to weaken or eliminate contact between the wire electrode 2 and the upper current-carrying member 44a. Next, the offset d2 is set to ensure sufficient contact between the wire electrode 2 and the lower current-carrying member 44b (step S2-2). The set offsets d1 and d2 are output to the movement control device 76 as motion command values.

[0083] The automatic wire-connecting device 3 inserts the wire electrode 2 into a lower hole formed in the workpiece W and automatically stretches the wire electrode 2 between the upper wire electrode guide 43a and the lower wire electrode guide 43b. This allows the wire electrode 2 to be fed while moving downward in a substantially vertical direction relative to the workpiece W (step S1-4).

[0084] In response to the motion command, the movement control device 76 moves the upper and lower current-carrying members 44a and 44b from their initial positions A1 and A2 by the set offsets d1 and d2, respectively, via the current-carrying member moving devices 45 and 46 (step S1-5). Furthermore, the power supply device 6 operates in response to the motion command, repeatedly applying voltage pulses to the machining gap 10 between the wire electrode 2 and the workpiece W via the upper and lower current-carrying members 44a and 44b (step S1-6). This generates an electrical discharge in the machining gap 10, achieving the desired shape.

[0085] [Example]

[0086] Hereinafter, the details will be described using examples, but the present invention is not limited to the following examples.

[0087] Using the wire electrode electrical discharge machining device 100, electrical discharge machining was performed on a workpiece W, and the state of the machined surface was observed. In all examples and comparative examples, a 40 mm thick steel metal plate was used as the workpiece W. Furthermore, a brass wire electrode 2 with an outer diameter of 0.2 mm was used.

[0088] Table 1 shows the conditions for the offset amounts d1 and d2 of the upper and lower current-carrying members 44a, 44b in Examples 1 to 3 and Comparative Example 1. In all Examples and Comparative Examples, the upper current-carrying member 44a was first moved from its initial position A1 in the A-axis direction by an offset amount d1 = 0.8 mm, and the lower current-carrying member 44b was first moved from its initial position A2 in the A-axis direction by an offset amount d2 = 0.8 mm, and the first cut was performed while the upper current-carrying member 44a was in full contact with the wire electrode 2.

[0089]

Table 1

[0090]

[0091] Subsequently, processing was performed five times after the second cut. In Examples 1 and 2, the upper current-carrying element 44a was moved from its initial position A1 in the A-axis direction by an offset of d1 = 0.5 mm and 0.2 mm, respectively, to ensure contact with the wire electrode 2, albeit weaker than during the first cut. In Example 3, the upper current-carrying element 44a did not move from its initial position A1 and did not come into contact with the wire electrode 2. Furthermore, in Examples 1 to 3, the lower current-carrying element 44b was moved from its initial position A2 in the A-axis direction by an offset of d2 = 0.8 mm to ensure full contact with the wire electrode 2.

[0092] In Comparative Example 1, as in the case of the first cutting, the upper side current-carrying body 44a is moved from the initial position A1 to the A-axis direction by an offset amount d1 = 0.8 mm, and the lower side current-carrying body 44b is moved from the initial position A2 to the A-axis direction by an offset amount d2 = 0.8 mm, and the processing after the second cutting is performed 5 times while being in full contact with the electrode wire 2.

[0093] Figure 7 A~ Figure 7 D represents the images of the processed surface after the second cutting was performed five times in Examples 1 to 3 and Comparative Example 1. Table 1 shows the results of observing the processed surface and evaluating the processing accuracy. In Comparative Example 1, the offset d1 of the upper current-carrying body 44a was not adjusted after the second cutting. Figure 7 Multiple stripes are generated in the vertical direction shown in D. In Example 1, although Figure 7In the example shown in A, streaks also occurred in the vertical direction, but the streaks were shallower than those in Comparative Example 1. In Examples 2 and 3, the streaks were significantly reduced compared to Comparative Example 1.

[0094] As mentioned above, although the preferred embodiment of the present invention was described, the present invention is not limited to the above embodiment, and various design changes can be made within the scope described in the claims.

Claims

1. A wire discharge machining device comprising a wire electrode, an upper guide assembly, and a lower guide assembly, wherein: The upper guide assembly and the lower guide assembly are respectively arranged on the upper side and the lower side of the workpiece in the vertical direction across the workpiece. The upper guide assembly includes an upper wire electrode guide, an upper current-carrying body, and a current-carrying body moving device. The lower guide assembly includes a lower wire electrode guide and a lower current-carrying body. The wire electrode is guided by the upper wire electrode guide and the lower wire electrode guide to perform electrical discharge machining on the workpiece. The upper and lower current-carrying bodies are configured to contact the wire electrode and supply power to the wire electrode by moving in a horizontal uniaxial direction from an initial position not in contact with the wire electrode. The current-carrying member moving device is configured to move the upper current-carrying member by a predetermined offset, wherein the offset is a distance that the upper current-carrying member moves from the initial position in the horizontal uniaxial direction in a direction that causes the upper current-carrying member to contact the wire electrode. The offset is set based on the processing conditions. The machining conditions include at least one of a condition of the wire electrode, a surface roughness required for a machined surface of the workpiece, and a condition of the workpiece.

2. The wire discharge machining device according to claim 1, wherein: Equipped with processing condition setting device and offset setting device, The processing condition setting device sets the processing conditions, The offset amount setting device sets the offset amount based on the data indicating the relationship between the processing condition and the offset amount and in accordance with the processing condition set by the processing condition setting device. The current-carrying member moving device is configured to move the upper current-carrying member by the offset amount set by the offset amount setting device.

3. The wire electrode discharge machining device according to claim 1 or 2, characterized in that: The condition of the wire electrode includes at least one of a material and an outer diameter of the wire electrode.

4. The wire discharge machining device according to claim 1 or 2, characterized in that: The condition of the workpiece includes at least one of the material and thickness of the workpiece.

5. The wire discharge machining device according to claim 1 or 2, characterized in that: The offset amount is set so that the offset amount when the surface roughness is equal to or less than a predetermined threshold value is smaller than the offset amount when the surface roughness is greater than the threshold value.

6. The wire discharge machining device according to claim 5, wherein: The offset amount when the surface roughness is equal to or less than the threshold value is set so that the upper current-carrying body comes into contact with the wire electrode.

7. The wire discharge machining device according to claim 5, wherein: The offset amount when the surface roughness is equal to or less than the threshold value is set so that the upper current-carrying body and the wire electrode do not come into contact with each other.

8. The wire discharge machining device according to claim 3, wherein: The conditions of the wire electrode include the outer diameter of the wire electrode, The offset amount is set so that the offset amount when the outer diameter is equal to or greater than a predetermined threshold value is smaller than the offset amount when the outer diameter is less than the threshold value.

9. The wire discharge machining device according to claim 8, wherein: The offset amount when the outer diameter is equal to or greater than the threshold value is set so that the upper current-carrying body comes into contact with the wire electrode.

10. The wire discharge machining device according to claim 8, wherein: The offset amount when the outer diameter is equal to or greater than the threshold value is set so that the upper current-carrying body and the wire electrode do not come into contact with each other.

11. A wire discharge machining method for a workpiece using a wire electrode, characterized in that: It has an offset setting process and a current-carrying body moving process. The electrode wire is guided by an upper wire guide and a lower wire guide respectively assembled in an upper guide assembly and a lower guide assembly respectively arranged on the upper side and the lower side of the workpiece in the vertical direction, and discharge-machines the workpiece. The upper guide assembly and the lower guide assembly are respectively provided with an upper power-carrying body and a lower power-carrying body. The upper and lower current-carrying bodies are configured to contact the wire electrode and supply power to the wire electrode by moving in a horizontal uniaxial direction from an initial position not in contact with the wire electrode. In the offset setting, the offset of the upper side current-carrying body is set based on the processing conditions. The offset of the upper side current-carrying body is the distance that the upper side current-carrying body moves from the initial position in the direction in which the upper side current-carrying body contacts the electrode wire toward the horizontal uniaxial direction. In the current-carrying member moving step, the upper current-carrying member is moved from the initial position to the horizontal uniaxial direction by the offset amount. The machining conditions include at least one of a condition of the wire electrode, a surface roughness required for a machined surface of the workpiece, and a condition of the workpiece.

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