Immersive wire electric discharge machine and wire electric discharge machining method

Abstract

To provide an immersive wire electric discharge machine capable of improving workpiece machining accuracy.SOLUTION: An immersive wire electric discharge machine M comprises: a machining tank 3 configured to be swingable in lateral and longitudinal directions through a swing mechanism 2; a support base 4 including a pedestal 40 and a leg 41 which support a workpiece W at a prescribed height and provided in an inner bottom surface in the machining tank 3; and an electric discharge machining mechanism 5 having upper and lower wire heads 53 and 54 having a wire electrode E stretched therebetween and provided to vertically face each other in the machining tank 3. A plurality of fixtures 43 for supporting the peripheral edge of the workpiece W are installed in the support base 4. The fixtures 43 are configured to be independently liftable, and includes measurement means 56 for detecting the position coordinates of the upper surface of the workpiece W supported by the fixtures 43, and control means CM for enabling movement of the wire head 53 positioned above the workpiece W relative to the wire head 54 positioned below the workpiece W in accordance with the position coordinates measured by the measurement means 56.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a submerged wire electric discharge machine and a wire electric discharge machining method for electric discharge machining of a workpiece contained in a machining tank in a machining fluid. [Background technology]

[0002] Generally, immersion-type wire electric discharge machines (hereinafter referred to as "wire electric discharge machines") are known as electric discharge machines that use a wire electrode to shape a workpiece (hereinafter referred to as "work") immersed in machining fluid into a predetermined shape. In wire electric discharge machines, the workpiece is machined by an electric discharge action generated between the workpiece and the wire electrode. The workpiece is fixed to a work support table installed in the machining tank by a work mounting bracket, and is configured to be movable relative to the wire electrode together with the machining tank. A wire electric discharge machine configured in this way can perform extremely precise machining by moving the workpiece together with the machining tank relative to the wire electrode fixed in the machining tank.

[0003] However, when a workpiece is attached to the workpiece support table, if the workpiece support surface of the workpiece support table is contaminated with sludge or fine dust adheres to the bottom surface of the workpiece, the bottom surface of the workpiece may rise unevenly from the support surface of the workpiece support table, and the workpiece may become tilted relative to the horizontal plane. Such tilting of the workpiece relative to the horizontal plane may also occur due to deterioration of the workpiece support table over time.

[0004] In this way, when a thick workpiece is fixed in an inclined position relative to the support surface of the workpiece support table, the wire electrode is not perpendicular to the top surface of the workpiece, which could result in misalignment of the cutting positions of the top and bottom surfaces of the workpiece, resulting in a decrease in the machining accuracy of the workpiece.

[0005] Patent Document 1 discloses a wire electric discharge machine equipped with a "horizontal correction function" that adjusts the inclination of the wire electrode relative to the horizontal plane so that the wire electrode is perpendicular to the top surface of a workpiece placed on a workpiece table in an inclined position. This wire electric discharge machine is configured to calculate a normal vector to the top surface of a workpiece placed on the workpiece table, and adjust the relative positions of the upper and lower wire guides so that the wire electrode stretched between the upper and lower wire guides is aligned with the normal vector, thereby making it possible to make the wire electrode perpendicular to the top surface of the workpiece. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2006-159396 A Summary of the Invention [Problem to be solved by the invention]

[0007] According to the configuration disclosed in Patent Document 1, the coordinates of any three points on the top surface of the workpiece are measured, one of the measured coordinates is set as the origin, a vector is formed connecting the origin and the other two points, and the cross product of the two vectors is obtained to calculate the normal direction to the top surface of the workpiece. Then, a technology is disclosed in which the relative positions of the upper and lower wire guides are adjusted to tilt the wire electrode stretched between the upper and lower wire guides along the normal direction to the top surface of the workpiece, thereby making the top surface of the workpiece and the wire electrode perpendicular to each other, thereby improving the machining accuracy of the workpiece. However, this configuration is based on the premise that the top surface of the workpiece is uniformly tilted, and if the top surface of the workpiece is tilted in various directions due to its own weight, etc., there is a risk of reducing the machining accuracy of the workpiece.

[0008] The present invention has been made in consideration of the above-mentioned problems, and has an object to provide an immersion type wire electric discharge machining machine and an immersion type wire electric discharge machining method that can improve the machining accuracy of a workpiece in a simple manner. [Means for solving the problem]

[0009] The immersion type wire electric discharge machine of the present invention comprises a machining tank configured to be swingable vertically and horizontally via a swing mechanism connected below for aligning the electric discharge machining, a support table including a base and legs provided on the inner bottom surface of the machining tank and supporting the workpiece at a predetermined height, and an electric discharge machining mechanism having upper and lower wire heads arranged opposite each other above and below in the machining tank and with a wire electrode stretched between them, wherein the support table is provided with a plurality of mounting fixtures for supporting the peripheral portion of the workpiece, each of the mounting fixtures being configured to be independently movable up and down, a measuring means for detecting position coordinates of the top surface of the workpiece supported by the plurality of mounting fixtures, and a control means for enabling the wire head located above the workpiece to be moved relatively to the wire head located below the workpiece in accordance with the position coordinates measured by the measuring means.

[0010] According to another aspect of the present invention, there is provided an immersion type wire electric discharge machining method comprising: a reference measurement step of measuring position coordinates of an upper surface of a workpiece placed on a surface plate provided outside the electric discharge machine; an adjustment step of adjusting a relative positional relationship of a corner of the workpiece supported by a fixture in the electric discharge machine so that the position coordinates of the corner of the workpiece among the position coordinates measured in the reference measurement step match the position coordinates measured in the reference measurement step; a measurement step of measuring position coordinates of each portion of the upper surface of the workpiece in a manner such that the relative positional relationship of the corner of the workpiece matches the relative positional relationship measured in the reference measurement step; a normal calculation step of comparing the position coordinates measured in the measurement step with the position coordinates measured in the reference measurement step to calculate a difference therebetween and calculating a normal direction at each position coordinate in accordance with the difference; and an intermediate portion calculation step of calculating a normal direction between each position coordinate from the normal direction calculated in the normal calculation step, wherein the workpiece is machined by tilting a wire electrode along the normal direction calculated in the normal calculation step and the intermediate portion calculation step. Effect of the Invention

[0011] According to the present invention, the machining accuracy of a workpiece can be improved by a simple method. [Brief description of the drawings]

[0012] [Figure 1] 1 is a perspective view of a wire electric discharge machine according to an embodiment of the present invention; [Diagram 2] 1 is a side view, partially in section, of a wire electric discharge machine according to an embodiment of the present invention; [Diagram 3] 1 is a front view, partially in section, of a wire electric discharge machine according to an embodiment of the present invention; [Figure 4] FIG. 1 is a front view showing a mounting fixture for a wire electric discharge machine according to an embodiment of the present invention. [Diagram 5] 1 is a perspective view showing a state in which a workpiece is gripped by a fixture of a wire electric discharge machine according to an embodiment of the present invention. FIG. [Figure 6] 1 is a plan view showing a state in which a workpiece is gripped by a fixture of a wire electric discharge machine according to an embodiment of the present invention. FIG. [Figure 7] FIG. 2 is a flowchart showing a wire electric discharge machining procedure of the wire electric discharge machine according to the embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] The present invention is a wire electric discharge machine M that performs electric discharge machining on a workpiece W, which is a workpiece contained in a machining tank 3, in machining fluid, and improves the machining accuracy of the workpiece W by devising a method for supporting the workpiece W in the machining tank 3 and adjusting the relative positions of upper and lower wire heads 53, 54 that suspend a wire electrode E in accordance with the amount of deflection due to the weight of the workpiece W fixed via a plurality of mounting fixtures 43 provided on a support stand 4 in the machining tank 3. Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0014] The overall configuration of the wire electric discharge machine M according to this embodiment will be described with reference to FIGS. 1 to 6. FIG. 1 is a perspective view showing an overall image of the wire electric discharge machine M. FIG. 2 is a side view of the wire electric discharge machine M, in which some parts, such as the machining tank 3, the support table 4, and the shielding plate 34, are shown in cross-section, and FIG. 2 shows the attachment tool 43 in a simplified manner. FIG. 3 is a front view of the wire electric discharge machine M, in which some parts, such as the machining tank 3 and the support table 4, are shown in cross-section. FIG. 4 is a schematic diagram showing an enlarged view of the vicinity of the base 40 of the support table 4 in FIG. 2. FIG. 5 is a perspective view showing a state in which the workpiece W is attached to the base 40 of the support table 4 in FIG. 2 via the attachment tool 43. FIG. 6 is a plan view showing a state in which the workpiece W is attached to the base 40 via the attachment tool 43. In the description of this embodiment, the direction indicated by the double arrow in FIG. 2 is the Y-axis direction, and the direction indicated by the double arrow in FIG. 3 is the X-axis direction. That is, the X-axis direction refers to the left-right direction when viewing the wire electric discharge machine M from the front, and the Y-axis direction refers to the front-rear direction of the wire electric discharge machine M.

[0015] As shown in FIG. 1, the wire electric discharge machine M is a so-called immersion type wire electric discharge machine that machines the workpiece W by applying an electrode voltage between the wire electrode E and the workpiece W while the workpiece W is immersed in the machining fluid. This wire electric discharge machine M comprises a machine body 1 having a base 10 such as a machine stand provided on an installation surface and a column 11, a oscillating mechanism 2 mounted on the base 10 of the machine body 1 so as to be movable in the X-axis and Y-axis directions, a machining tank 3 mounted and fixed to the oscillating mechanism 2, a support stand 4 fixed to the inner bottom surface of the machining tank 3 by a fastening means such as a bolt, an electric discharge machining mechanism 5 supported by the column 11 of the machine body 1 and supporting the wire electrode E at a predetermined position within the machining tank 3 so as to be inclined with respect to the horizontal plane while enabling current to be passed through the wire electrode E, a lower arm section 6 extending from the column 11 of the machine body 1 to the machining tank 3 and having its tip inserted into the machining tank 3, and a machining fluid supply pipe 7 connected to the lower arm section 6 for supplying machining fluid to the machining tank 3.

[0016] The processing machine body 1 is composed of a base 10 placed on a mounting surface and a column 11 erected on the rear upper surface of the base 10. The base 10 is formed in a box shape, and a pair of Y-axis guide rails 12 and a Y-axis moving means are arranged on the upper surface. The Y-axis guide rails 12 are approximately rectangular in cross section and are laid along the left and right sides of the base 10 from near the front end to near the rear end of the base 10. The Y-axis moving means is provided approximately in the center of the pair of left and right Y-axis guide rails 12, and has a driving motor and a screw shaft for transmitting the rotation of the motor. The screw shaft is composed of a ball screw that converts the rotational motion of the motor into linear motion.

[0017] The column 11 has a rectangular column-shaped column body 13 erected on the rear of the base 10. The column body 13 has an arm fixing hole 14 drilled in a circular shape in front view at the top and bottom central parts of the front side surface. The column body 13 has an upper arm section 50 connected to its top, and a lower arm section 6 connected to the arm fixing hole section 14. The lower arm section 6 is supported with its central axis direction in the pipe shape aligned along the front-rear direction, penetrating the front wall section of the column body 13 that forms the arm fixing hole section 14, and its rear end section positioned inside the column body 13. The lower arm section 6 is supported by the column body 13 in the form of a cantilever beam.

[0018] The rocking mechanism 2 has a Y-axis table 20 that is capable of moving horizontally in the Y-axis direction on the upper surface of the base 10, and an X-axis table 21 that is capable of moving horizontally in the X-axis direction on the upper surface of the Y-axis table 20.

[0019] The Y-axis table 20 has a Y-axis table main body 22 formed into a rectangular plate of a certain thickness with its longer side in the X-axis direction, Y-axis slide guides 23 provided on the underside of the Y-axis table main body 22 near each corner, a pair of X-axis guide rails 24 extending in the X-axis direction along the front and rear side edges of the Y-axis table main body 22 on the upper surface of the Y-axis table main body 22, and shielding plate support parts 29 connected to the left and right sides of the rear end part of the Y-axis table main body 22.

[0020] The Y-axis table body 22 has a Y-axis movement hole 25 formed in the center of the front and rear sides, penetrating front and rear along the Y-axis direction. The Y-axis table body 22 has the Y-axis movement hole 25 engaged with a screw shaft of a Y-axis movement means.

[0021] The Y-axis slide guide 23 has a recess extending from front to back in the center of its underside. The Y-axis guide rail 12 fits into the recess of the Y-axis slide guide 23. That is, the Y-axis table main body 22 fits into the Y-axis guide rail 12 via the recess of the Y-axis slide guide 23.

[0022] The X-axis guide rail 24 is formed in a substantially rectangular shape in cross section, and is laid from near the left end to near the right end of the Y-axis table main body 22. In addition, the X-axis moving means is disposed in the vicinity of either the left or right end in the X-axis direction of the Y-axis table main body 22, approximately in the center between the pair of X-axis guide rails 24.

[0023] The X-axis moving means is composed of a motor for rotation and a screw shaft for transmitting the rotational force of the motor. The screw shaft extends in the left-right direction substantially parallel to the X-axis guide rail 24. The screw shaft is composed of a ball screw that converts the rotational motion of the motor into linear motion.

[0024] The shielding plate support part 29 is formed in a plate shape having a certain thickness and a rectangular shape when viewed from the front, and extends upward from the Y-axis table main body 22. The shielding plate support part 29 has a shielding plate 34 fixed to it near its upper end by a fastening means such as a screw. In other words, the shielding plate support part 29 fixes the shielding plate 34 to the Y-axis table main body 22, and moves integrally with the Y-axis table main body 22.

[0025] The X-axis table 21 has a plate-like X-axis table main body 26 having a certain thickness and formed in a square shape in a plan view, and X-axis slide guides 27 provided on the underside near each corner of the X-axis table main body 26. The X-axis table main body 26 has an X-axis movement hole 28 formed in the center of the X-axis side surface along the X-axis direction, penetrating the X-axis direction. The X-axis table main body 26 is moved along the X-axis direction in conjunction with the rotation of the screw shaft by engaging the X-axis movement hole 28 with the screw shaft of the X-axis moving means. At this time, the X-axis slide guide 27 slides on the pair of X-axis guide rails 24.

[0026] As described above, the wire electric discharge machine M in this embodiment is equipped with the Y-axis table 20 and the X-axis table 21 as the oscillation mechanism 2, and the machining tank 3 mounted and fixed on the X-axis table 21 can be moved arbitrarily in the X-axis direction or the Y-axis direction while maintaining a horizontal state by the Y-axis moving means mounted and fixed on the base 10 of the machine body 1 and the X-axis moving means mounted and fixed on the Y-axis table 20. The movement direction and amount of movement of the oscillation mechanism 2 are controlled by a control unit (not shown) by specifying numerical values, etc.

[0027] The processing tank 3 is formed in a rectangular box shape with a bottom and an open top, and has a horizontal bottom surface portion 31 and four vertical side wall surface portions 32. The bottom surface portion 31 of the processing tank 3 is placed on the X-axis table 21, and is configured to be movable integrally with the X-axis table 21. The side wall surface portion 32 constituting the rear surface of the processing tank 3 has a long hole 33 drilled in an elliptical shape with the X-axis direction as the longitudinal direction near the lower end portion in the center of the left-right direction, and a seal portion that supports a shielding plate 34 provided to cover the long hole 33 from the outside of the side wall surface portion 32 so as to be in sliding contact with the outer surface of the side wall surface portion 32. Note that in the description of this embodiment, the seal portion is not shown.

[0028] The elongated hole 33 is formed to have a vertical width slightly larger than the vertical width of the lower arm portion 6. In other words, the lower arm portion 6 is inserted into the processing tank 3 without contacting the opening edge of the elongated hole 33.

[0029] A support table 4 for supporting and fixing the workpiece W within the machining tank 3 is fixed to the bottom surface 31 of the machining tank 3 by fixing means such as bolts. The support table 4 comprises a base 40 for fixing the workpiece W and legs 41 for supporting the base 40 at a predetermined height within the machining tank 3. The base 40 is formed in a rectangular plate shape having a constant thickness, and has a rectangular opening 42 drilled approximately in the center when viewed from above, and a fastening hole 40a for fixing a mounting fixture 43 that directly supports the workpiece W.

[0030] The base 40 has a fixture 43 fixed near the opening 42. The workpiece W is fixed at a predetermined height from the base 40 via the fixture 43. In this case, the workpiece W is fixed to the fixture 43 so as to close the opening 42 in a plan view. The base 40 has one end connected to a power source that generates a predetermined voltage during electric discharge machining, and the other end connected to a lead. In this embodiment, the base 40 is connected to the negative side of the power source by a lead wire.

[0031] 5 and 6, the fixtures 43 are fixed to fastening holes 40a provided along the edge of the opening 42. The fixtures 43 are provided on each side of the opening 42 so that the fixtures 43 face each other. In this embodiment, the fixtures 43 are fixed to fastening holes 40a located approximately in the center in the longitudinal direction (X-axis direction) of the opening 42, and are fixed to fastening holes 40a that divide the lateral direction (Y-axis direction) of the opening 42 into approximately three equal parts. That is, in this embodiment, the fixtures 43 are provided to support the workpiece W at six locations.

[0032] As shown in Figure 4, the mounting fixture 43 has a position fixing part 44 for fixing it to the base part 40 of the support table 4, and a work fixing part 45 attached to the upper surface of the position fixing part 44 so that it can be raised and lowered relative to the position fixing part 44.

[0033] The position fixing part 44 has a bottom surface part 44a which is fixed in contact with the upper surface of the base part 40, a top surface part 44b which is provided above the bottom surface part 44a so as to face the bottom surface part 44a, and a side surface part 44c which holds the bottom surface part 44a and the top surface part 44b in a state where they are separated by a predetermined distance. Each surface part is formed in a rectangular plate shape having a certain thickness. The position fixing part 44 is formed in a substantially U-shape in a front view by connecting one end of the bottom surface part 44a and the top surface part 44b with the side surface part 44c, and has an adjustment space CS surrounded by the bottom surface part 44a, the top surface part 44b, and the side surface part 44c.

[0034] The bottom surface portion 44a and the top surface portion 44b have insertion holes 44d, 44e formed in the approximate center in a plan view so as to penetrate in the up-down direction. The position fixing portion 44 is fixed by inserting a fastening means such as a bolt through the insertion hole 44d of the bottom surface portion 44a and screwing the tip of the fastening means into the fastening hole 40a of the base portion 40.

[0035] The workpiece fixing portion 45 has a bottom surface portion 45a that supports the workpiece W, an upper surface portion 45b that supports a fixing means for fixing the workpiece W supported by the bottom surface portion 45a, a side surface portion 45c that connects the bottom surface portion 45a and the upper surface portion 45b, and a height adjustment shaft portion 46 that extends downward from approximately the center of the lower surface of the bottom surface portion 45a. Each surface portion is formed in a substantially rectangular flat plate shape, and the bottom surface portion 45a and the upper surface portion 45b are formed in approximately the same shape in a plan view. The workpiece fixing portion 45 is formed in a substantially U-shape in a front view by connecting one end of the bottom surface portion 45a and one end of the upper surface portion 45b with the side surface portion 45c.

[0036] The height adjustment shaft portion 46 is provided integrally with the bottom surface portion 45a in a manner perpendicular to the lower surface of the bottom surface portion 45a. The height adjustment shaft portion 46 has a threaded portion 46a at its lower end.

[0037] The height adjustment shaft 46 has a screw portion 46a inserted into the insertion hole 44e of the position fixing part 44. The height adjustment shaft 46 is fixed at a predetermined height relative to the upper surface 44b by clamping the upper surface 44b of the position fixing part 44 from above and below with two nuts screwed onto the screw portion 46a. The work fixing part 45 can be adjusted by changing the insertion allowance d of the screw portion 46a inserted into the adjustment space CS through the insertion hole 44e of the upper surface 44b. In other words, when the insertion allowance d is increased, the height of the work fixing part 45 relative to the base part 40 is lowered, and when the insertion allowance d is decreased, the height of the work fixing part 45 relative to the base part 40 is increased. Note that the insertion allowance d in this embodiment refers to the distance from the lower surface of the upper surface 44b of the position fixing part 44 to the lower end of the screw portion 46a of the height adjustment shaft 46 protruding into the adjustment space CS.

[0038] The upper surface portion 45b has a workpiece fixing hole 45d formed in the approximate center in a plan view so as to penetrate in the up-down direction. A female thread is threaded into the inner peripheral surface of the workpiece fixing hole 45d. A workpiece fixing bolt 45e is screwed into the workpiece fixing hole 45d.

[0039] The workpiece fixing bolt 45e is for fixing the workpiece W placed on the upper surface of the bottom surface portion 45a. In the workpiece fixing portion 45, the workpiece W is placed on the upper surface of the bottom surface portion 45a, and the upper surface of the workpiece is pressed downward by the workpiece fixing bolt 45e, thereby being fixed to the workpiece fixing portion 45. In other words, the workpiece W is fixed to the workpiece fixing portion 45 by being clamped between the upper surface of the bottom surface portion 45a and the tip of the workpiece fixing bolt 45e.

[0040] As described above, the workpiece W fixed to the base portion 40 in the machining tank 3 is fixed to the workpiece fixing portion 45 by the workpiece fixing bolt 45e, and is supported so that its height can be adjusted according to the insertion allowance d of the screw portion 46a into the adjustment space CS of the position fixing portion 44.

[0041] Furthermore, since the support table 4 and the machining tank 3 are fixed together via the legs 41, the workpiece W can be moved together with the machining tank 3. In other words, the movement amount of the machining tank 3 and the movement amount of the workpiece W by the rocking mechanism 2 are the same, and the movement amount of the workpiece W can be precisely controlled simply by numerically controlling the rocking mechanism 2.

[0042] As shown in Figures 2 and 3, the electric discharge machining mechanism 5 has a control means CM that controls the inclination of the wire electrode E with respect to a vertical plane in accordance with the inclination of the top surface of the workpiece W with respect to a horizontal plane, an upper wire head 53 that can be moved in the X-axis, Y-axis, and Z-axis directions by the control means CM, a lower wire head 54 connected to the tip of the lower arm portion 6 extended from the arm fixing hole portion 14 of the column body 13 toward the machining tank 3, and a wire electrode E stretched between the upper wire head 53 and the lower wire head 54.

[0043] The control means CM includes an upper arm portion 50 extending from the upper end of the column body 13 toward the front in the Y-axis direction, a head portion 51 connected to the tip of the upper arm portion 50 so as to be movably connected along the X-axis direction, and a lifting portion 52 connected to the front end of the head portion 51 so as to be movably connected along the up-down direction.

[0044] The upper arm portion 50 has a Y-axis guide rail 50a provided on the upper surface of the column body 13, and an arm box 50b provided so as to be movable in the Y-axis direction along the Y-axis guide rail 50a.

[0045] As shown in Figures 2 and 3, the Y-axis guide rail 50a is formed in a substantially rectangular shape in cross section, extends along the vicinity of the left and right ends of the upper surface of the column body 13, and is laid in a manner such that it protrudes from the front and rear ends of the column body 13.

[0046] The arm box 50b has a box-shaped arm box main body 55 and a Y-axis slide guide 55a provided on the lower surface of the arm box main body 55 in the vicinity of the approximately center in the front-rear direction and the rear end in a side view. The arm box main body 55 is connected to a swing mechanism (not shown). The arm box main body 55 is movable in the front-rear direction by the swing mechanism, and can move in the Y-axis direction along the pair of Y-axis guide rails 50a by fitting the Y-axis slide guide 55a of the arm box main body 55 into the Y-axis guide rails 50a.

[0047] The Y-axis slide guide 55a has a recess that is recessed from front to back in the center of the left-right direction on the bottom surface. The Y-axis slide guide 55a has the Y-axis guide rail 50a fitted into the recess. That is, the arm box body 55 is movable in the Y-axis direction along the Y-axis guide rail 50a by fitting the Y-axis guide rail 50a into the recess of the Y-axis slide guide 55a.

[0048] Furthermore, the arm box body 55 has an X-axis guide rail 55b along the X-axis direction on the front surface. The X-axis guide rail 55b is provided near the upper and lower ends of the front surface of the arm box body 55. The X-axis guide rail 55b is formed in a substantially rectangular shape in cross section, and is provided along the X-axis direction from near the left end to near the right end of the arm box body 55.

[0049] The head portion 51 has a box-shaped head body 51a, an X-axis slide guide 51b provided near the upper end of the back side of the head body 51a and near approximately the center in the vertical direction, and a Z-axis guide rail 51c provided on the front side of the head body 51a, extending from the upper end to the lower end at approximately the center in the left-right direction and protruding downward from the lower end of the head body 51a.

[0050] The head body 51a is connected to a swing mechanism, similar to the upper arm unit 50. The swing mechanism allows the head body 51a to move in the X-axis direction along a pair of upper and lower X-axis guide rails 55b while maintaining the head body 51a in a horizontal state.

[0051] The X-axis slide guide 51b has a recess extending from left to right in the center of the rear surface. The X-axis slide guide 51b has an X-axis guide rail 55b fitted into the recess. That is, the head main body 51a is fitted into the X-axis guide rail 55b via the recess of the X-axis slide guide 51b, so that the head main body 51a can move in the X-axis direction along the X-axis guide rail 55b while maintaining a horizontal state.

[0052] The lifting unit 52 has a box-shaped lifting unit main body 52a and a Z-axis slide guide 52b provided on the back side of the lifting unit main body 52a. The lifting unit main body 52a has a swing mechanism. The lifting unit 52 can move the lifting unit main body 52a in the Z-axis direction along the Z-axis guide rail 51c by the swing mechanism.

[0053] The lower end of the lifting section 52 is provided with an automatic wire feeder that supplies the wire electrode E used during electric discharge machining, and an upper wire head 53. In addition, the lifting section 52 is provided with a measuring means 56 on either the left or right side near the lower end.

[0054] The upper wire head 53 incorporates a die guide, a jet nozzle, an electrical supply, etc., as in the conventional case. That is, the upper wire head 53 can send out the wire electrode E supplied from an automatic wire feeder to the lower wire head 54 through a wire feed port of the die guide. The wire electrode E is connected to an electrical supply having one end connected to a power source that generates a predetermined voltage during electric discharge machining within the upper wire head 53. The wire electrode E is connected to the anode side of the power source by the electrical supply.

[0055] The upper jet nozzle is provided near the wire feed outlet of the die guide, with its outlet aligned along the feed direction of the wire electrode E.

[0056] The lower wire head 54 is disposed below the base 40 of the support table 4 and faces the upper wire head 53. The lower wire head 54, like the upper wire head 53, incorporates a die guide, a jet nozzle, a power supply, a pulley for guiding the wire electrode E after discharge to the lower arm 6, and the like. The lower wire head 54 receives the wire electrode E sent out from the upper wire head 53 through a wire receiving port of the die guide. The wire electrode E is connected to a power supply in the lower wire head 54. One end of the power supply is connected to a power source that generates a predetermined voltage during electric discharge machining. The power supply provided in the lower wire head 54 has the same potential as the power supply provided in the upper wire head 53, and is connected to the anode side of the power source like the upper wire head 53.

[0057] The wire electrode E in this embodiment is a thin metal wire, and is stretched with a constant tension between the upper wire head 53 and the lower wire head 54. The wire electrode E enters the wire receiving port of the lower wire head 54 from the wire outlet port of the upper wire head 53, is guided to the lower arm 6 via the pulley, and is sent out to the outside of the machining tank 3 from the other end of the lower arm 6. The wire electrode E is sent out to the lower arm 6 by the pulley without bending within the lower wire head 54. The wire electrode E is discharged to the outside from the base end of the lower arm 6.

[0058] The measuring means 56 has a probe support portion 56a and a spherical trigger probe 56b connected to the lower end portion of the probe support portion 56a. The measuring means 56 applies a weak voltage between the spherical trigger probe 56b and the workpiece W in advance, and detects the change in voltage when the probe support portion 56a comes into contact with the workpiece W, thereby detecting the position coordinates of the surface of the workpiece W that the trigger probe 56b comes into contact with. Note that the position coordinates of the trigger probe 56b of the measuring means 56 are measured by determining a reference position coordinate, and then measuring the amount of movement of each of the upper arm portion 50, the head portion 51, and the lifting portion 52.

[0059] In this embodiment, the three-dimensional coordinates of the contact point are measured by contact with the spherical trigger probe 56b, but the method of measuring the three-dimensional coordinates may be any means capable of measuring the position coordinates of the top surface of the workpiece W, such as a laser rangefinder that irradiates laser light from the measuring instrument and measures the distance to the object to be measured based on the time it takes for the irradiated laser light to return to the measuring instrument, or an optical measuring device that irradiates light other than laser light in the same manner as a laser rangefinder and measures the distance from the measuring instrument to the top surface of the workpiece W by measuring the time it takes for the light to return.

[0060] The lower arm portion 6 is supported and fixed in a cantilever manner in an arm fixing hole portion 14 provided in the column body 13. The lower arm portion 6 has a hollow lower arm body 60 extending from the arm fixing hole portion 14 along the Y-axis direction. The lower arm portion 6 has a lower wire head 54 connected and fixed to the tip portion of the lower arm body 60 so as to partially close the tip opening of the lower arm portion 6. Thus, in this embodiment, the lower wire head 54 is provided in a manner fixed within the processing tank 3 by the lower arm body 60.

[0061] According to the wire electric discharge machine M of this embodiment as described above, by supporting the workpiece W at points using the six liftable fixtures 43, it is possible to unify the direction of deflection of the workpiece W due to its own weight supported by the fixtures 43 in the direction of the center of gravity of the workpiece W. In other words, by unifying the deformation direction of the workpiece W supported by the fixtures 43 in the machining tank 3, there is no risk of sudden deflection occurring on the upper surface of the workpiece W, and the machining accuracy of the workpiece W can be improved.

[0062] Furthermore, according to the wire electric discharge machine M of this embodiment, the upper and lower wire heads 53, 54, on which the wire electrode E is suspended, are made movable relative to the lower wire head 54 in the X-axis, Y-axis and Z-axis directions by the upper arm section 50, head section 51 and lifting section 52 as a control means CM. As a result, the wire electrode E can be easily adjusted in a perpendicular direction in response to deflection of the workpiece W due to its own weight that occurs when the workpiece W is supported by the mounting fixture 43 at a distance above the base section 40, thereby improving the machining accuracy of the workpiece W.

[0063] A wire electric discharge machining method for performing wire electric discharge machining of a workpiece W placed on the support table 4 of the machining tank 3 with good machining accuracy using the wire electric discharge machine M configured as described above will be described below. The wire electric discharge machining is performed according to the process flow of FIG. 7. Such a wire electric discharge machining method will be described with reference to FIG. 6 and FIG. 7. In FIG. 7, the reference measurement step S1 is performed in a state where the workpiece W is placed on a platen having a horizontal surface that is installed outside the wire electric discharge machine M. Moreover, the adjustment step S2 to the machining step S6 are performed in a state where the workpiece W is placed inside the wire electric discharge machine M. In FIG. 7, the two-dot chain line indicates the division between the processing performed outside the wire electric discharge machine M and the processing performed inside the wire electric discharge machine M. That is, the upper side of the two-dot chain line in FIG. 7 is the processing outside the wire electric discharge machine M, and the lower side of the two-dot chain line is the processing inside the wire electric discharge machine M.

[0064] First, the worker places the workpiece W, which is approximately rectangular in plan view, on a surface plate. The worker arbitrarily selects one point from each corner of the upper surface of the workpiece W, and sets the corner O as the origin. The worker measures three-dimensional position coordinate information A (A1 to A12) for the other corners C1, C2, C3, and arbitrary measurement points C4 to C12 using the measurement means 56 (reference measurement step S1). After that, the worker converts the position coordinate information A for each measurement point including the corner O into a workpiece coordinate system with the corner O as the origin. The converted position coordinate information A for each measurement point including the corner is stored in the memory of the control unit (not shown). Note that the workpiece coordinate system with the corner O as the origin here means converting the position coordinates A1 to A12 of each measurement point C1 to C12 into a coordinate system with the corner O as the origin (0,0,0). In addition, the measuring means 56 in this embodiment may be any means for measuring, such as a three-dimensional measuring device, a laser distance meter, an optical measuring device, etc. In this embodiment, the measurement is performed using a contact-type three-dimensional measuring device. The corners O, C1, C2, and C3 and the measurement points C4 to C12 are as shown in FIG. 6.

[0065] The worker stores the data of position coordinate information A (A1, A2, A3) converted into the work coordinate system in the memory of the control unit, and then fixes the work W placed on the table to the base 40 in the processing tank 3 via the mounting fixture 43.

[0066] The worker measures position coordinate information B (B1 to B3) of corners C1, C2, and C3 on the top surface of the workpiece W fixed to the base 40 in a workpiece coordinate system with the corner O as the origin using the measuring means 56, and stores the information in the memory of the control unit.

[0067] Next, position coordinate information A (A1, A2, A3) measured in a workpiece coordinate system with the corner O as the origin is compared with position coordinate information B (B1, B2, B3) measured in a workpiece coordinate system with the corner O as the origin, and the difference between the position coordinate information A and the position coordinate information B is calculated as differential coordinate information D (D1, D2, D3) and stored in the memory of the control unit. The worker adjusts the height of the workpiece fixing part 45 by adjusting the insertion allowance d of the height adjustment shaft part 46 according to the differential coordinate information D (D1, D2, D3), and matches the position coordinate information B (B1, B2, B3) with the position coordinate information A (A1, A2, A3). In other words, the positions of the corners C1, C2, C3 of the workpiece W are adjusted by the height adjustment shaft part 46 so that the X coordinate, Y coordinate, and Z coordinate of the differential coordinate information D (D1, D2, D3) are all (0, 0, 0). In other words, in a work coordinate system with the corner O of the work W as the origin, the height of the work fixing portion 45 of each mounting fixture 43 supporting the work W is adjusted by the height adjustment shaft portion 46 so that the positional relationship of the corners O, C1, C2, C3 of the work W when placed on the table matches the positional relationship of the corners O, C1, C2, C3 of the work W placed in the processing tank 3 (adjustment step S2).

[0068] Next, the workpiece W is left in the machining tank 3 for a predetermined time with the X coordinate, Y coordinate, and Z coordinate of the differential coordinate information D (D1, D2, D3) all being (0, 0, 0). Note that the time for which the workpiece W is left is not particularly limited as long as the workpiece W supported by the fixture 43 has deformed to a state where it cannot be deformed any further.

[0069] After a predetermined time has elapsed while the workpiece W is fixed to the fixture 43 in the processing tank 3, the position coordinate information B (B4 to B12) of each measurement point C4 to C12 of the workpiece W is measured by the measuring means 56 provided on the lifting section 52 (measurement step S3).

[0070] At this time, the measuring means 56 mathematically calculates the upper surface in the X-axis direction and the Y-axis direction from the position coordinate information B (B1-B12) of each of the measurement points C1-C12 for the top surface of the workpiece W. That is, for the X-axis direction, the control unit calculates a function connecting the measurement points O, C5, C4, C3, C6, C10, C11, C12, C9, and C1, C7, C8, C2 from the position coordinate information B of these measurement points C. Also, for the Y-axis direction, the control unit calculates a function connecting the measurement points O, C6, C1, C5, C10, C7, C4, C12, C8, and C3, C9, C2.

[0071] Next, a tangent plane is calculated for each of the measurement points C1 to C12 of the measured workpiece W. After that, a direction perpendicular to the calculated tangent plane, i.e., a normal vector for each of the measurement points C1 to C12, is calculated, and the position of the upper wire head 53 relative to the lower wire head 54 along this normal vector is stored in the memory of the control unit (normal calculation step S4).

[0072] Next, the deflection of the workpiece W other than each of the measured measurement points C1 to C12 of the workpiece W is calculated assuming that the amount of deflection gradually increases (or decreases) without causing a sudden change between adjacent measurement points (intermediate portion calculation step S5).

[0073] Next, the locus along which the upper wire head 53 moves along the normal vector formed in normal calculation step S4 and intermediate portion calculation step S5 is calculated by the control unit and recorded in memory.

[0074] The wire electric discharge machine M according to this embodiment performs wire electric discharge machining while moving relatively to the lower wire head 53 in accordance with the trajectory information of the upper wire head 53 recorded in the memory (machining step S6).

[0075] In this way, by calculating the normal vector for each measurement point C (C1 to C12) on the workpiece W through each step and adjusting the relative position of the upper wire head 53 with respect to the lower wire head 54 so that it is along this normal vector, the wire electrode E can be made perpendicular to the upper surface of the workpiece W in accordance with the deflection due to the weight of the workpiece W, thereby improving the machining accuracy of the workpiece W.

[0076] In this embodiment, the measurement means 56 calculates normal vectors at 13 measurement points including the corner O, which is the origin of the workpiece W, but the present invention is not limited to 13 measurement points, and the workpiece W may be further divided and measured. By increasing the number of measurement points of the workpiece W, the machining accuracy can be further improved.

[0077] Although one embodiment of the present invention has been described, the above description is merely an example of the present invention, and the present invention is not limited to the above-described embodiment. Therefore, even if the embodiment is different from the above-described embodiment, various modifications can be made depending on the design, etc., as long as they do not deviate from the technical concept of the present invention. [Explanation of symbols]

[0078] 1 Processing machine body 2. Swing mechanism 3 Processing tank 4 Support stand 5 Electric discharge machining mechanism 6 Lower arm 43 Mounting fixture 53 Upper Wire Head 54 Lower Wire Head 56 Measurement methods E Wire Electrode M Wire EDM Machine CM Control Measures CS adjustment space

Claims

1. a machining tank configured to be swingable in the vertical and horizontal directions via a swing mechanism connected below for alignment of the electric discharge machining; A support table including a base and legs that is provided on an inner bottom surface of the processing tank and supports the workpiece at a predetermined height; an electric discharge machining mechanism provided in the machining tank so as to face each other vertically and having upper and lower wire heads with a wire electrode stretched therebetween; In a submerged wire electric discharge machine comprising: A plurality of fixtures for supporting a peripheral portion of the workpiece are provided on the support table, The mounting fixtures are configured to be independently movable up and down, a measuring means for detecting position coordinates of an upper surface of the workpiece supported by the plurality of fixtures; a control means for controlling the wire head positioned above the workpiece to be moved relative to the wire head positioned below the workpiece in accordance with the position coordinates measured by the measuring means; An immersion wire electric discharge machine equipped with:

2. a reference measurement step of measuring the position coordinates of an upper surface of a workpiece placed on a surface plate; an adjustment step of adjusting a relative positional relationship of a corner of the workpiece supported by the fixture so that position coordinates of the corner of the workpiece among the position coordinates measured in the reference measurement step coincide with position coordinates measured in the reference measurement step; a measuring step of measuring position coordinates of each part on the upper surface of the workpiece in a manner that the relative positional relationship of the corners of the workpiece in the adjustment step is matched to the relative positional relationship measured in the reference measurement step; a normal calculation step of comparing the position coordinates measured in the measurement step with the position coordinates measured in the reference measurement step to calculate a difference therebetween, and calculating a normal direction at each position coordinate in accordance with the difference; an intermediate portion calculation step of calculating a normal direction between each of the position coordinates from the normal direction calculated in the normal calculation step; having a wire electric discharge machining method for machining a workpiece by tilting a wire electrode along the normal direction calculated in said normal line calculation step and said intermediate portion calculation step;

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