JP6303357B2 - Machine Tools - Google Patents

Description

  The present invention relates to a machine tool that positions a holding unit that holds a workpiece processed by a tool.

  A machine tool holds a work on a table and performs various processes such as milling and tapping with a tool mounted on a spindle. The machine tool includes a spindle head that rotatably supports the spindle, a Z-axis moving device that reciprocates the spindle head in the vertical direction (Z-axis direction), and two horizontal directions (X-axis and Y-axis directions). An XY-axis moving device that reciprocally moves the main shaft and a main shaft driving device that rotationally drives the main shaft.

  The table for holding the workpiece may be fixed to the base of the machine tool, or may be configured to rotate the workpiece around an axis parallel to the Z axis, for example. In addition to the movement of the main shaft, more complicated machining can be performed by rotating the workpiece (see, for example, Patent Document 1).

  Patent Document 1 discloses a machine tool including a work table that holds a work, a spindle that rotates the work table, and a servo motor that supplies a rotational force to the spindle. A clamp disk is attached to the spindle, and the spindle is accommodated in the housing. The spindle is braked when the clamp disk contacts the housing.

  When positioning the workpiece, the control unit moves the clamp disc away from the housing, turns on the servo motor, and moves the workpiece to a predetermined position using the detection value of the position detector of the servo motor as feedback information. Then, the control unit turns off the servo motor and brings the clamp disk into contact with the housing to prevent the workpiece from rotating.

  The workpiece is processed in a state where the workpiece is prevented from rotating by the clamp disk. When the tool contacts the workpiece, a large force is instantaneously applied to the workpiece. Therefore, even if the brake is braked by the clamp disk, the spindle may rotate slightly, and the position of the workpiece may deviate from a predetermined position. If the amount of workpiece displacement is larger than the allowable value, an alarm is activated and machining is interrupted.

  Patent Document 2 discloses a machine tool including a saddle to which a machining head is attached, a screw shaft that is screwed into a nut portion of the saddle, and a servo motor that rotates the screw shaft. The saddle slides on the guide. The control unit of the machine tool moves the saddle by rotating the servo motor to the target position.

  After the saddle is moved, the rotation shaft of the servo motor is slightly returned to the drive mechanism such as the screw shaft due to the frictional resistance of the saddle and the guide. Therefore, the control unit calculates the return amount of the servo motor, subtracts the return amount from the target position, and resets the value after the subtraction as a new target position. Thus, the servo motor can be prevented from rotating in order to eliminate the return amount during the stop period, and the power consumption can be reduced.

JP-A-6-161527 Japanese Patent Laid-Open No. 6-187043

  When a workpiece is machined a plurality of times, for example, when a plurality of holes are drilled, the position of the workpiece is slightly shifted each time a hole is drilled. Since the servo motor is turned off and the spindle is braked by the clamp disk, the workpiece stops at a position shifted. The amount of positional deviation of the workpiece is gradually increased by a plurality of drilling processes. Therefore, in the machine tool described in Patent Document 1, when the above processing is performed, an alarm is activated, the processing is likely to be interrupted, and the production efficiency may be reduced. Further, when a workpiece is machined a plurality of times at the same position, for example, the same problem occurs when drilling and tapping are performed at the same location of the workpiece.

  In the machine tool described in Patent Document 2, since the saddle is located at a position different from the initial target position, the machining accuracy is lowered.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide a machine tool that can eliminate a positional deviation of a workpiece and prevent a decrease in manufacturing efficiency and machining accuracy.

Machine tools according to the present invention, a rotatable holder for holding the workpiece to be machined by the tool, a servo motor for rotating the holder, and a braking unit for braking the holding portion, the holding in the rotational direction In a machine tool comprising: a storage unit for storing a position of the unit and a command for machining the workpiece; and a control unit for reading the command stored in the storage unit and controlling the driving of the servo motor and the operation of the braking unit. A position detection unit that detects the position of the holding unit in the rotation direction; and a calculation unit that calculates a difference between the position of the holding unit stored in the storage unit and the position of the holding unit detected by the position detection unit; A determination unit that determines whether or not the difference calculated by the calculation unit is smaller than a preset first threshold, and the control unit is configured such that the servo motor is turned off. The holding unit is braked by the braking unit, and after the determination unit determines that the difference is smaller than the first threshold value, the difference calculated by the calculation unit is smaller than the first threshold value. when greater than a preset second threshold value, said servo motor is turned on to release the brake by the brake unit, which are not the holding portion so that moving to the position stored in the storage unit It is characterized by.

  In the present invention, when the difference between the position of the holding unit stored in the storage unit and the location of the holding unit detected by the position detection unit is smaller than a preset first threshold value, that is, the positional deviation of the workpiece is allowed. In the case where the value does not exceed the value, when the difference exceeds the second threshold value that is smaller than the first threshold value, the servo motor is turned on and the braking by the braking unit is released. The workpiece returns to the stored position before the displacement of the workpiece exceeds the allowable value.

The machine tool according to the present invention includes a rotatable holding portion that holds a workpiece processed by a tool, a servo motor that rotates the holding portion, a braking portion that brakes the holding portion, and the holding portion in the rotation direction. In a machine tool comprising: a storage unit for storing a position and a command for machining a workpiece; and a control unit for reading the command stored in the storage unit and controlling the drive of the servo motor and the operation of the braking unit. A position detection unit that detects the position of the holding unit in the direction; a calculation unit that calculates a difference between the position of the holding unit stored in the storage unit and the position of the holding unit detected by the position detection unit; and a determination section for determining small or not than the first threshold value the difference computed by the computing unit is set in advance, the control unit, the servo motor is turned off Wherein and braked the holding portion by the braking portion, the position of the holding portion stored in the storage unit after setting the position after the movement of the holding portion, the judgment unit the difference is the first by When it is determined that the value is smaller than the threshold value and the command for positioning the holding unit to the same position as the position of the holding unit stored in the storage unit is read, the difference calculated by the calculation unit is When the servo motor is turned on when the preset second threshold value is smaller than the first threshold value , the braking by the braking unit is released, and the read command is executed. And

  In the present invention, when the workpiece displacement does not exceed the allowable value and the workpiece is moved to the same position as the position stored in the storage unit, if it is larger than the second threshold value smaller than the allowable value, Before moving the workpiece, turn on the servo motor and release the braking by the braking unit. When the workpiece is moved to the same position as the position where positioning has already been performed (the position stored in the storage unit), the positioning of the workpiece is omitted in order to improve manufacturing efficiency. However, when the workpiece positioning is omitted, the workpiece displacement in the previous process remains. According to the present invention, when the workpiece is moved to the same position as the position where the positioning has already been performed, the workpiece is positioned again, and the positional deviation of the workpiece is eliminated. When the workpiece position deviation is smaller than the second threshold, it is considered that the position deviation is caused by the characteristics of the position detector or the like, or is a minute position deviation that does not affect the machining accuracy of the workpiece.

Machine tools according to the present invention, a rotatable holder for holding the workpiece to be machined by the tool, a servo motor for rotating the holder, and a braking unit for braking the holding portion, the holding in the rotational direction In a machine tool comprising: a storage unit for storing a position of the unit and a command for machining the workpiece; and a control unit for reading the command stored in the storage unit and controlling the driving of the servo motor and the operation of the braking unit. A position detection unit that detects the position of the holding unit in the rotation direction; and a calculation unit that calculates a difference between the position of the holding unit stored in the storage unit and the position of the holding unit detected by the position detection unit; , and a determination section for determining small or not than the first threshold value the difference computed by the computing unit is set in advance, the control unit, the servo motor is turned off Has braked the holding portion by the braking portion, after said difference by said determination unit is determined to be smaller than the first threshold value, is calculated by and reads the movement command or tool change command of the spindle the arithmetic unit When the difference is larger than a preset second threshold value smaller than the first threshold value , the servo motor is turned on in parallel with the execution of the spindle movement command or the tool change command, and the braking unit The brake is released and the actuator is moved to the position of the holding unit stored in the storage unit.

  In the present invention, when the workpiece position deviation does not exceed the allowable value and a command different from the workpiece positioning is read, if the command is larger than the second threshold value, the servo motor is turned on and braking by the braking unit is performed. To release. When a command different from the workpiece positioning is read, for example, when a spindle movement command or a tool change command is read, the workpiece positioning is executed. As a result, workpiece misalignment is confirmed and corrected in processes other than the workpiece machining process, so the process for confirming and correcting workpiece misalignment is performed simultaneously with a command different from workpiece positioning. Prolonging the cycle time in can be avoided.

  In the machine tool according to the present invention, when the difference between the position of the holding unit stored in the storage unit and the location of the holding unit detected by the position detection unit is smaller than a preset first threshold, In the case where the positional deviation of the workpiece does not exceed the allowable value, if the difference is larger than the second threshold value which is smaller than the first threshold value, the servo motor is turned on and braking by the braking unit is released. Since the work returns to the position stored in the storage unit before the work position deviation exceeds the allowable value, the work position deviation can be eliminated and the manufacturing efficiency and machining accuracy can be prevented from being lowered.

It is a perspective view of a machine tool. It is a front view of a machine tool. It is a right view of a machine tool. It is a perspective view of the machine tool which abbreviate | omitted the cover etc. which cover a guide rail. It is a front side perspective view of a workpiece | work support apparatus. It is a back side perspective view of a workpiece support device. It is a vertical front view of a turntable and a C-axis drive part. It is sectional drawing to which the piston and its peripheral part were expanded. It is a block diagram which shows the structure of a control part vicinity. It is a flowchart explaining the process which confirms and correct | amends the position shift of a workpiece | work.

  Hereinafter, the present invention will be described in detail with reference to the drawings showing a machine tool according to the embodiment. In the following description, up and down, left and right, and front and rear indicated by arrows in the figure are used. 1 is a perspective view of the machine tool 100, FIG. 2 is a front view of the machine tool 100, FIG. 3 is a right side view of the machine tool 100, and FIG. 4 is a machine in which a cover and the like covering the guide rail are omitted. 1 is a perspective view of a machine 100. FIG. The operator operates the machine tool 100 in the front and attaches / detaches the workpiece.

  The machine tool 100 includes a base 10, a Y-direction moving device 20, an X-direction moving device 21, a column 22, a Z-direction moving device 23, a spindle head (processing spindle device) 25, a workpiece support device 30, and the like. The machine tool 100 supports a workpiece (workpiece) with the workpiece support device 30 and processes the workpiece with a tool 26 attached to the spindle head 25. The tool 26 is detachably attached to the lower end portion of the spindle head 25 and can be changed by a tool changer (not shown). In the machine tool 100 according to the present embodiment, the spindle head 25 is movable in the X direction, the Y direction, and the Z direction, and the workpiece can be rotated about two axes.

  In general, when a workpiece is rotated about axes parallel to the X, Y, and Z axes, which are axes for moving the spindle head 25, the rotation axes of the workpiece correspond to the X, Y, and Z axes as A, B , Called the C-axis. The work support device 30 according to the present embodiment can rotate the work around the A axis by swinging a swinging body 40 described later, and a C-axis drive unit 60 (see FIG. 5) fixed to the swinging body 40. The workpiece can be rotated around the C axis.

  The base 10 includes a gantry 11, a spindle base 13, work bases 14 and 14 and the like. The gantry 11 is a substantially rectangular parallelepiped structure that is long in the front-rear direction. Four legs 12, 12,... That can be adjusted in height are provided at the four corners of the lower part of the gantry 11. The legs 12, 12, ... are arranged on the floor surface. The gantry 11 includes a bottom plate 11a, a side plate 11b, an upper plate 11c, and support plates 11d and 11d inside. The bottom plate 11a has a rectangular shape in plan view. The side plate 11b is connected to the four sides of the bottom plate 11a and surrounds the front, rear, left and right. The upper plate 11c has a deep dish shape having a rectangular shape in plan view, and four sides are fixed to the inner peripheral surface of the upper end portion of the side plate 11b. The upper plate 11 c has a through hole 11 e at a position below the work support device 30. Cutting chips, coolant, and the like generated by the processing fall downward through the through hole 11e and are collected by a collecting device (not shown). Each of the support plates 11d and 11d is erected upward from the bottom plate 11a, and the plate surfaces are spaced apart from each other in parallel with the plate surfaces of the left and right side plates 11b. The upper ends of the support plates 11d and 11d are in contact with the bottom surface of the upper plate 11c and support the upper plate 11c.

  The spindle base 13 has a substantially rectangular parallelepiped shape that is long in the front-rear direction, and is disposed in the rear part on the upper plate 11c. The spindle base 13 has two parallel support bases 13a and 13a that are long in the front-rear direction and supports guide rails 20a and 20a described later. The work bases 14 and 14 are arranged on the left and right of the front part on the upper plate 11c. Each of the work bases 14 and 14 includes a front support 14a and a rear support 14b. Each of the support bases 14a and 14b has a column shape, and the work support device 30 is seated on the upper surface and fixed.

  The Y-direction moving device 20 includes a pair of guide rails 20a, 20a parallel to each other, a plurality of blocks 20b, 20b,..., A Y-direction moving table 20c, and a Y-direction drive motor 20d (see FIG. 9). The guide rails 20a, 20a extend in the front-rear direction on the upper surfaces of the support bases 13a, 13a of the spindle base 13. The blocks 20b, 20b,... Are fitted to the guide rails 20a, 20a so as to be movable in the front-rear direction. The Y-direction moving base 20c is fixed on the blocks 20b, 20b,. The Y-direction moving table 20c moves in the front-rear direction by driving the Y-direction drive motor 20d.

  The X-direction moving device 21 includes a pair of guide rails 21a, 21a, a plurality of blocks 21b, 21b,..., A column base 21c, and an X-direction drive motor 21d (see FIG. 9). The guide rails 21a, 21a extend in the left-right direction on the upper surface of the Y-direction moving table 20c with an appropriate interval in the front-rear direction. The blocks 21b, 21b,... Are fitted to the guide rails 21a, 21a so as to be movable in the left-right direction. The column base 21c is fixed on the blocks 21b, 21b,. The column base 21c is moved in the left-right direction by driving the X-direction drive motor 21d.

  The column 22 has a columnar shape and is fixed on the column base 21c. The column 22 is moved in the front-rear direction and the left-right direction by the Y-direction moving device 20 and the X-direction moving device 21. The column 22 and the column base 21c are integrally formed.

  The Z-direction moving device 23 includes a pair of guide rails 23a, 23a, a plurality of blocks 23b, 23b,..., A spindle head base 23c, and a Z-direction drive motor 23d (see FIG. 9). The guide rails 23a and 23a are extended in the vertical direction on the front surface of the column 22 with an appropriate interval in the horizontal direction. The blocks 23b, 23b,... Are fitted to the guide rails 23a, 23a so as to be movable in the vertical direction. The spindle head base 23c is fixed to the front side of the blocks 23b, 23b,. The spindle head base 23c is moved in the vertical direction by driving the Z-direction drive motor 23d.

  The spindle head 25 is fixed to the spindle head base 23c. By driving and controlling the X-direction drive motor 21d, the Y-direction drive motor 20d, and the Z-direction drive motor 23d, the spindle head 25 moves back and forth, left and right, and up and down.

  The spindle head 25 rotatably holds a spindle (not shown) extending in the vertical direction inside the front portion 25a. The main shaft detachably holds the tool 26 at the lower end. The spindle is connected to a spindle motor 25b provided at the upper end of the spindle head 25. The spindle motor 25b rotates the spindle around the axis, rotates the tool 26 attached to the lower end of the spindle, and can perform cutting on the workpiece fixed to the workpiece support device 30.

  FIG. 5 is a front perspective view of the work support device 30, FIG. 6 is a rear perspective view of the work support device 30, and FIG. 7 is a longitudinal front view of the turntable 50 and the C-axis drive unit 60. The work support device 30 includes a gear box 31, a bearing box 34, an A-axis motor 36, a rocking body 40, a rotary base 50, a C-axis drive unit 60, and the like.

  The gear box 31 accommodates a shaft 41 on the right side of a rocking body 40 described later, and supports the shaft 41 so as to be rotatable around the X axis. In the following description, the central axis of the shaft portion 41 is expressed as an A axis. The A axis is an axis parallel to the X axis, and means a swing axis in the workpiece support device 30. The A-axis motor 36 is attached to the front side of the gear box 31, and the rotating shaft (not shown) faces the gear box 31. The rotation axis of the A-axis motor 36 rotates around the Y axis and drives a gear connected to the tip. The gear is composed of, for example, a known roller gear cam shaft and a cam follower, and converts the rotation about the Y axis into the rotation about the A axis which is orthogonal. A roller gear cam shaft is coaxially connected to the rotation shaft of the A-axis motor 36, a plurality of cam followers are arranged on the outer periphery of the end portion of the shaft portion 41, and the cam follower is engaged with the cam of the roller gear cam shaft. As the cam of the roller gear cam, a globoidal cam that does not generate backlash not only during stopping but also during rotation can be used. The gear box 31 has mounting seats 31a at the lower four corners, and is fixed to the right work base 14 by screws or the like.

  The bearing box 34 accommodates a shaft 41 on the left side of a rocking body 40 described later, and supports the shaft 41 so as to be rotatable around the A axis. The bearing box 34 has mounting seats 34a on the front and rear of the lower part, and is fixed to the left work base 14 by screws or the like.

  The oscillating body 40 is a structure in which left and right shaft portions 41 and 41 are connected, and has a substrate portion for fixing the C-axis drive portion 60 at a substantially center between the shaft portions 41 and 41. Each of the left and right shaft portions 41, 41 has a cylindrical shape, the right shaft portion 41 is supported by the gear box 31 so as to be rotatable around the A axis, and the left shaft portion 41 is rotatable by the bearing box 34 around the A axis. It is supported by. The shaft portions 41 and 41 are arranged so as to be coaxial with each other. The rocking body 40 is provided with a rotary table 50 above the substrate portion and a C-axis drive unit 60 below.

  The C-axis drive unit 60 includes a housing 61, a C-axis motor 79, a rotary shaft 80, an encoder 81, and the like. The housing 61 includes a body portion 62, a bottom plate 63, a bearing holder 64, an upper plate 65, and the like, and has a bottomed cylindrical shape. The body portion 62 has a cylindrical shape, and heat dissipating fins are formed on the outer periphery, and a stator 79a is fixed on the inner periphery. A bottom plate 63 is fixed to the lower surface of the body portion 62, and an upper plate 65 is fixed to the upper surface via a bearing holder 64. The bottom plate 63 has an annular shape, and a bearing 76 is fitted on the inner peripheral surface thereof, and is fixed to the body portion 62 at the outer peripheral edge portion.

  The bearing holder 64 is formed with an annular flange outwardly at the lower end of a cylindrical portion into which the bearing 75 is inserted. By inserting the bearings 75 and 76 into the bearing holder 64 and the bottom plate 63, respectively, and inserting the rotating shaft 80 into the bearings 75 and 76, the rotating shaft 80 is supported rotatably around the C axis. Here, the C-axis means the axial direction of the rotating shaft 80. In general, the C-axis means an axis parallel to the Z-axis, but in the present invention, since the oscillating body 40 oscillates, the C-axis direction is treated as being changed by the oscillation. The turntable 50 is fixed to the upper end surface of the rotation shaft 80 and rotates around the C axis together with the rotation shaft 80. A rotor 79b is fixed to the outer peripheral surface of the rotary shaft 80 in the middle in the vertical direction. The stator 79a and the rotor 79b constitute a C-axis motor 79. When power is supplied from the power supply line 82 to the C-axis motor 79, the rotor 79b rotates, and the rotating shaft 80 to which the rotor 79b is fixed has a rotating shaft 80. Rotate.

  The upper plate 65 has a substantially annular shape, and a shaft hole through which the rotation shaft 80 passes is provided at the center. The shape of the upper plate 65 will be further described later. The turntable 50 is arranged so as to cover the shaft hole, and holds the workpiece on the mounting surface 50a opened upward. An annular labyrinth seal 66 concentric with the rotating shaft 80 is formed between the outer surface 65a of the upper plate 65 facing the rotating table 50 and the surface of the rotating table 50 facing the outer surface 65a. A cylindrical air injection chamber 67 concentric with the rotary shaft 80 is formed inside the labyrinth seal 66 (inside the housing 61).

  The air injection chamber 67 is narrowed with its upper end covered with a wall surface, and communicates with the inside of the labyrinth seal 66. An oil seal 68 is disposed at the lower end of the air injection chamber 67 so that air does not leak downward. The upper plate 65 is formed with a flow channel 69 penetrating horizontally from the outer periphery toward the outer peripheral wall surface of the air injection chamber 67. The gaps of the compressor C, the flow channel 69, the air injection chamber 67, and the labyrinth seal 66 are communicated with each other via the openable / closable air regulator V1.

  A brake mechanism as a braking portion is provided on the lower surface side of the upper plate 65. The upper plate 65 has a substantially annular shape as described above. Specifically, a cylindrical portion is formed downward from the outer edge of the disk-shaped wall portion forming the outer surface 65a, and the upper plate 65 faces outward from the lower end of the cylindrical portion. A flange portion is formed on the outer periphery, and a cylindrical portion is further formed downward from the outer edge of the flange portion. The rotary shaft 80 has a flange on the outer peripheral surface at the end of the rotary base 50, and a brake plate 70 is fixed to the flange by a screw or the like. The brake plate 70 has a disk shape having a hole through which the rotary shaft 80 passes. A piston 71 is disposed on the outer peripheral surface of the cylindrical portion into which the bearing 75 of the bearing holder 64 is inserted.

  FIG. 8 is an enlarged cross-sectional view of the piston 71 and its peripheral portion. The brake plate 70 is disposed to face the inner surface 65b of the upper plate 65. The piston 71 is formed by forming a cylindrical portion and an annular flange portion outwardly at the lower end of the cylindrical portion. The inner peripheral surface 71 a of the cylindrical portion of the piston 71 faces the outer peripheral surface 64 a of the cylindrical portion of the bearing holder 64, and the outer peripheral surface 71 c faces the inner peripheral surface 65 c of the cylindrical portion of the upper plate 65. An inner peripheral surface 65c of the upper plate 65 is a cylinder into which the piston 71 is inserted. An upper end surface 71 b in the cylindrical portion of the piston 71 faces the lower surface of the brake plate 70. The outer peripheral surface 71 d of the flange portion of the piston 71 faces the inner peripheral surface 65 d of the cylindrical portion of the upper plate 65. The lower end surface 71e of the piston 71 faces the upper surface 64e of the flange portion of the bearing holder 64, and a brake pressurizing chamber is formed between the lower end surface 71e and the upper surface 64e. The upper surface 71f of the flange portion of the piston 71 faces the lower surface 65f of the flange portion of the upper plate 65, and a brake release pressurizing chamber is formed between the upper surface 71f and the lower surface 65f.

  Between the inner peripheral surface 71a of the piston 71 and the outer peripheral surface 64a of the bearing holder 64, and between the outer peripheral surface 71c of the piston 71 and the upper plate 65 so that each of the brake pressurizing chamber and the brake releasing pressurizing chamber has a sealed structure. D rings 74 are mounted between the peripheral surface 65c and between the outer peripheral surface 71d of the piston 71 and the inner peripheral surface 65d of the upper plate 65, respectively. A communication channel 72 that penetrates the upper plate 65 from the outer peripheral side communicates with the brake release pressurization chamber, and a communication channel 73 that penetrates the bearing holder 64 from the outer peripheral side communicates with the brake pressurization chamber. . The valve V2 (see FIG. 7) can be opened to introduce the air from the compressor C into the flow path 72 and pressurize the brake release pressurizing chamber. The valve V3 can be opened to pass the air from the compressor C through the flow path 73. And can be pressurized to the brake pressurizing chamber. The piston 71 moves up and down by the pressure applied to the brake release pressurizing chamber or the brake pressurizing chamber, so that the brake release operation and the brake operation can be performed. The valves V1 to V3 are electromagnetic valves.

  Returning to FIG. 7, the configuration of the lower end portion of the housing 61 will be described. A substantially annular substrate 77 is fixed to the lower end portion of the rotating shaft 80. The substrate 77 is disposed so as to cover the shaft hole formed in the bottom plate 63, and has a facing surface that faces the outer surface of the bottom plate 63. The sealing portion 78 includes labyrinth seals 78 a and 78 b and seals a gap between the outer surface of the bottom plate 63 and the opposing surface of the substrate 77. The labyrinth seal 78 a is configured by providing an annular convex line concentric with the rotation shaft on the opposite surface of the substrate 77, and providing an annular fitting groove on the outer surface of the bottom plate 63 for fitting the convex line. The labyrinth seal 78 b is configured by providing an annular convex groove concentric with the rotation shaft on the outer surface of the bottom plate 63, and providing an annular fitting groove on the opposing surface of the substrate 77 for fitting the convex line. The encoder 81 is an optical or magnetic angle detector. The encoder 81 detects an angle by detecting a detection object 81a such as a disk arranged on the rotation side by a detection element 81b arranged on the fixed side. The detection object 81 a is fixed to the outer peripheral surface of the substrate 77 that rotates together with the rotating shaft 80, and the detection element 81 b is fixed to the outer surface of the bottom plate 63. The sealing portion 78 prevents, for example, lubricant that has leaked from the bearing 76 from entering the encoder 81.

  When the workpiece is rotated by the C-axis drive unit 60, the valve V3 is closed, the valve V2 is opened, the air from the compressor C is introduced into the flow path 72, and the brake release pressurizing chamber (the lower surface of the flange portion of the upper plate 65). 65f and the space between the upper surface 71f of the flange portion of the piston 71) is pressurized. The piston 71 is pushed down by the pressurization to the brake release pressurizing chamber, the brake plate 70 is separated from the inner surface 65b of the upper plate 65, the brake is released, that is, the brake is released, and the rotating shaft 80 can be rotated.

  When the work is fixed so as not to rotate around the C axis, the valve V2 is closed, the valve V3 is opened, air from the compressor C is introduced into the flow path 73, and the brake pressurizing chamber (with the lower end surface 71e of the piston 71 and The space between the flange 64 and the upper surface 64e of the bearing holder 64 is pressurized. The piston 71 is pushed up by the pressurization to the brake pressurizing chamber, the upper end surface 71b of the piston 71 presses the brake plate 70 against the inner surface 65b of the upper plate 65, and the brake is applied, that is, the rotary shaft 80 is braked. Is restricted. Note that when the valve V2 or V3 is closed, the air in the brake release pressurizing chamber or the brake pressurizing chamber that is not pressurized may be decompressed by a decompression means (not shown).

  In the work support device 30, the swinging body 40 swings and the turntable 50 rotates by a control signal given from the control unit 90 (see FIG. 9) to the A-axis motor 36 and the C-axis motor 79. The rotation shaft of the A-axis motor 36 is rotated by the control signal to the A-axis motor 36, and the rotational force is transmitted by the gear accommodated in the gear box 31, so that the shaft portion 41 in the gear box 31 rotates around the A axis. To do. As the shaft portion 41 rotates, the work supported by the rocking body 40 and the turntable 50 rocks. Assuming that the normal direction of the mounting surface 50a of the turntable 50 faces upward (for example, the state shown in FIG. 5) is 0 degrees, the shaft portion 41 is in the range from +90 degrees to −90 degrees around the A axis. Thus, the workpiece can be rotated to an arbitrary angle and stopped, and the workpiece surface facing the tool 26 can be cut.

  The rotating shaft 80 is rotated by the rotation of the C-axis motor 79, and the rotating table 50 connected to the rotating shaft 80 and the work supported by the rotating table 50 rotate around the C axis. If there is no mechanical interference, the workpiece can be set at an arbitrary angle around the C axis. Combining rotation around the C axis and rocking by the rocking body 40, cutting to a work surface having a normal direction on the hemisphere with the normal direction of the mounting surface 50a of the turntable 50 as the zenith direction and the normal direction. Processing becomes possible. Further, turning can be performed by rotating the workpiece at a high speed by the C-axis motor 79 and pressing the tool 26 against the workpiece and sending it.

  FIG. 9 is a block diagram showing a configuration near the control unit 90. The machine tool 100 includes a control unit 90. The control unit 90 includes a CPU (Central Processing Unit) 91, a ROM (Read Only Memory) 92, a RAM (Random Access Memory) 93, and the like. The ROM 92 stores a control program for the machine tool 100. The CPU 91 reads a control program from the ROM 92 to the RAM 93 and controls the machine tool 100 using the RAM 93 as a work area. The RAM 93 reads a machining program stored in an external storage device (not shown). The machining program has a plurality of instructions, and the CPU 91 sequentially reads and executes the instructions.

  The RAM 93 stores a variable P indicating the position of the workpiece, a variable E indicating the difference between the variable P and the position of the turntable 50 detected by the encoder 81, a first threshold, and a second threshold smaller than the first threshold. Instead of the ROM 92, a rewritable storage medium such as an EEPROM (Electrically Erasable Programmable ROM), an EPROM (Erasable Programmable ROM), or an HD (Hard Disk) may be used. Note that the ROM 92 and the RAM 93 function as a storage unit.

  The control unit 90 controls the spindle motor 25b, the X direction drive motor 21d, the Y direction drive motor 20d, the Z direction drive motor 23d, the A axis motor 36, the C axis motor 79, and the valves V1, V2, and V3 via the output interface. Output a signal. The machine tool 100 includes a buzzer 95, and the control unit 90 outputs a control signal to the buzzer 95 via an output interface.

  The control unit 90 takes in position information about the C axis of the turntable 50 from the encoder 81 via the input interface. The control unit 90 controls the rotation of the C-axis motor 79 based on the position information acquired from the encoder 81 and moves the workpiece to the target position. That is, the C-axis motor 79 performs servo control using the detection value from the encoder 81 as feedback information. The C-axis motor 79 and the encoder 81 function as a servo motor. A position detector that detects the position of the turntable 50 may be provided separately from the encoder 81.

  FIG. 10 is a flowchart for explaining processing for confirming / correcting the work position deviation. The flow of FIG. 10 is started at a predetermined cycle after the power is turned on and the initialization is completed, and the processing for reading out the machining program command is performed in a main routine (not shown). The control unit 90 confirms the positional deviation of the workpiece. For example, the positional deviation around the C axis is confirmed. In the initial state, it is assumed that the machine tool 100 is not processing a workpiece, and the control unit 90 brakes the rotary shaft 80, turns off the C-axis motor 79, and turns off the function as a servo motor. Further, it is assumed that the CPU 91 of the control unit 90 has set the position where the turntable 50 should be based on the machining program as the variable P.

  The CPU 91 fetches the position P1 around the C axis of the turntable 50 from the encoder 81 (step S1), and calculates the difference E between the fetched P1 and the variable P (step S2). The CPU 91 determines whether or not the difference E is greater than or equal to the first threshold (step S3). When the difference E is greater than or equal to the first threshold value (step S3: YES), the CPU 91 outputs an on signal to the buzzer 95 (step S10) and ends the process. When the difference E is equal to or greater than the first threshold, the position of the turntable 50 is greatly deviated from the position set in the variable P. Therefore, the buzzer 95 is turned on to notify the operator to that effect. When the buzzer 95 is turned on, the turntable 50 stops.

  When the difference E is less than the first threshold value (step S3: NO), the CPU 91 determines whether or not the read machining program command is a positioning command for the turntable 50 around the C axis (step S4). When the command of the read machining program is a positioning command for the turntable 50 around the C axis (step S4: YES), the CPU 91 determines whether or not the commanded position is a position set in the variable P. (Step S5).

  If the commanded position is not the position set in the variable P (step S5: NO), the CPU 91 sets the commanded position in the variable P (step S6). The CPU 91 releases the braking of the turntable 50 and turns on the C-axis motor 79 to perform servo control (step S7).

  The CPU 91 positions the turntable 50 at the position of the variable P (step S8). After the positioning of the turntable 50 at the commanded position is completed, the CPU 91 brakes the turntable 50 and turns off the C-axis motor 79 to release the servo control (step S9). Then, the CPU 91 returns the process to step S1.

  When the read machining program command is not a positioning command for the turntable 50 around the C axis (step S4: NO), the CPU 91 determines that the read machining program command is another positioning command (for example, in the X to Z axis directions of the spindle). It is determined whether it is a positioning command) (step S11). If the read machining program command is not another positioning command (step S11: NO), the CPU 91 returns the process to step S1.

  When the command of the read machining program is another positioning command (step S11: YES), the CPU 91 determines whether or not the difference E is greater than or equal to the second threshold (step S12). When the difference E is less than the second threshold (step S12: NO), the CPU 91 returns the process to step S1.

  When the difference E is greater than or equal to the second threshold (step S12: YES), the CPU 91 advances the process to step S7. In step S5, when the commanded position is a position set in the variable P (step S5: YES), the CPU 91 advances the process to step S12.

When a workpiece is machined multiple times at the same position, for example, when drilling or tapping is performed on the same part of the workpiece, the positional deviation increases sequentially, so an alarm is activated and machining is likely to be interrupted. Become.
In the machine tool according to the embodiment, when the workpiece displacement does not exceed the allowable value and the workpiece is moved to the same position as the position set in the variable P, the second threshold is smaller than the allowable value. If it is larger, the servo motor is turned on, the braking by the braking unit is released, and the position moves to the position of the variable P, so that a small displacement of the workpiece can be eliminated and the machining accuracy of the workpiece can be improved. Moreover, since this is eliminated when the positional deviation is small, it is possible to prevent the alarm from being activated and the processing from being interrupted, and to avoid a reduction in manufacturing efficiency (see steps S5 to S9 and S12).
When the workpiece is moved to the same position as the position already set in the variable P, the positioning of the workpiece is omitted in order to improve manufacturing efficiency. However, when the workpiece positioning is omitted, the workpiece displacement in the previous process remains. Even when the machine tool 100 according to the embodiment moves the workpiece to the same position as the position already set in the variable P, the workpiece is positioned and the positional deviation of the workpiece is eliminated. When the workpiece position deviation is smaller than the second threshold, it is considered that the position deviation is caused by the characteristics of the position detector or the like, or is a minute position deviation that does not affect the machining accuracy of the workpiece.

  Further, when the workpiece position deviation does not exceed the allowable value and a command different from the workpiece positioning is read, the servo motor is turned on if the command is larger than a second threshold value smaller than the allowable value, and the turntable 50 Release the brake and move to the position of variable P. When a command different from the workpiece positioning is read, for example, when a spindle movement command or a tool change command is read, the workpiece positioning is executed. Since the work position deviation is checked and corrected in processes other than the workpiece machining process, the work position deviation check / correction process is performed at the same time as a command different from the work positioning, so the cycle time in work machining Can be avoided.

  In the embodiment, the process for confirming and correcting the positional deviation of the turntable 50 around the C axis is performed. However, the same process is applied to the position deviation of the turntable 50 around the A axis or the B axis. May be.

DESCRIPTION OF SYMBOLS 100 Machine tool 25 Spindle head 50 Turntable 60 C axis drive part 61 Housing 67 Air injection chamber 70 Brake plate 71 Piston 79 C axis motor (servo motor)
80 Rotating shaft 81 Encoder (Position detector, Servo motor)
90 control unit 91 CPU
92 ROM
93 RAM

Claims (3)

A rotatable holding portion for holding a workpiece to be machined by a tool, a servo motor for rotating the holding portion, a braking portion for braking the holding portion, a position of the holding portion in the rotation direction, and a command for machining the workpiece In a machine tool comprising: a storage unit that stores the control unit; and a control unit that reads the instructions stored in the storage unit and controls the driving of the servo motor and the operation of the braking unit.
A position detection unit for detecting the position of the holding unit in the rotation direction;
A calculation unit that calculates a difference between the position of the holding unit stored in the storage unit and the position of the holding unit detected by the position detection unit;
A determination unit that determines whether or not the difference calculated by the calculation unit is smaller than a preset first threshold;
The controller is
The servo motor is turned off, the holding unit is braked by the braking unit, and after the determination unit determines that the difference is smaller than the first threshold, the calculation unit calculates When the difference is larger than a preset second threshold value that is smaller than the first threshold value, the servo motor is turned on, braking by the braking unit is released, and the holding unit is stored in the storage unit machine tool, wherein you have to so that is moved to the position. A rotatable holding portion for holding a workpiece to be machined by a tool, a servo motor for rotating the holding portion, a braking portion for braking the holding portion, a position of the holding portion in the rotation direction, and a command for machining the workpiece In a machine tool comprising: a storage unit that stores the control unit; and a control unit that reads the instructions stored in the storage unit and controls the driving of the servo motor and the operation of the braking unit.
A position detection unit for detecting the position of the holding unit in the rotation direction;
A calculation unit that calculates a difference between the position of the holding unit stored in the storage unit and the position of the holding unit detected by the position detection unit;
A determination unit for determining whether the difference calculated by the calculation unit is smaller than a first threshold value set in advance;
With
The controller is
The servo motor is turned off, and then brake the holding portion by the brake unit, the position of the storage unit stored in the holding unit after setting the position after the movement of the holding portion, When the determination unit determines that the difference is smaller than the first threshold, and then reads an instruction to position the holding unit at the same position as the holding unit stored in the storage unit, When the difference calculated by the calculation unit is larger than a preset second threshold value smaller than the first threshold value , the servo motor is turned on, the braking by the braking unit is released, and the read command it characterized in that are to be executed machine tools. A rotatable holding portion for holding a workpiece to be machined by a tool, a servo motor for rotating the holding portion, a braking portion for braking the holding portion, a position of the holding portion in the rotation direction, and a command for machining the workpiece In a machine tool comprising: a storage unit that stores the control unit; and a control unit that reads the instructions stored in the storage unit and controls the driving of the servo motor and the operation of the braking unit.
A position detection unit for detecting the position of the holding unit in the rotation direction;
A calculation unit that calculates a difference between the position of the holding unit stored in the storage unit and the position of the holding unit detected by the position detection unit;
A determination unit for determining whether the difference calculated by the calculation unit is smaller than a first threshold value set in advance;
With
The controller is
The servo motor is turned off, the holding unit is braked by the braking unit, and after the determination unit determines that the difference is smaller than the first threshold, a spindle movement command or tool change When the difference between the command read out and calculated by the calculation unit is greater than a preset second threshold smaller than the first threshold , in parallel with the execution of the spindle movement command or the tool change command, the servo motor is turned on to release the brake by the brake unit, machine tool you characterized that you have to move to the position of the stored in the storage unit the holder.

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