JP2003205439A - Positioning method for machine tool - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a simple method for positioning in nano unit between a machine tool and a work piece or between an electrode of an electric discharge machine and a work piece. <P>SOLUTION: This positioning method comprises a step of relatively moving a part to be positioned to open along a relative moving axis by a designated distance by relatively moving the work piece and the electrode or the tool to come close to or into contact or separate after the machine origin return operation processing; a first contact sensing step of moving both along the moving axis at a preset speed to be close to each other until they come into contact with each other and stopping the same; a step of moving back both from the stop position until contact sensing is released along the moving axis by a designated very small distance and stopping the same; a second contact sensing step of setting the moving amount as a minimum set unit to the above backward very small distance, moving both to be close to each other until they come into contact, performing the movement at a preset designated low speed, stopping the same on sensing the contact, and storing that position; and a step of positioning the stored position of the second contact sensing of both to the machine origin. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to, for example, centering, end face positioning between a workpiece of a machining center and a cutting tool, or between a workpiece of an electric discharge machine and an electrode for electric discharge machining, or the position of the upper surface of a workpiece or the lower end of a spindle. The present invention relates to a method for rapidly performing high-accuracy positioning by utilizing contact detection between a workpiece and a tool or an electrode.

[0002]

Positioning of workpieces and / or tools utilizing contact sensing between the workpiece and the tool is widely used in electrical discharge machining because the workpiece and tool electrodes are conductors. In particular, it is often used for vertical placement of wire electrode tools for wire electric discharge machining. However, depending on the type of power supply used and the voltage value, the above-mentioned touch sensing may be several μm.
It is not used for submicron positioning due to the presence of front and rear discharge gaps and the occurrence of bending of the wire electrode tool, and also for the positioning of machine tools such as machining centers for the same reason. There is also a problem that a voltage applying means such as contact detection is not provided between the workpiece and the tool, or even if the voltage applying means is installed, there is no part suitable for contact positioning between the workpiece and the tool. , Was not used for sub-micron or better, ie, nm (nanometer) ordering.

A machine tool of this type, for example, a die-sinking electric discharge machine is constructed as shown in FIG. A workpiece 2 to be machined is fixed on a machining table in a machining tank (not shown), and a Z provided on a column (not shown).
The Z that is held by the axis processing head 8 so as to be movable along the Z axis
The machining table (not shown) faces the machining electrode 10 at the lower end of the shaft quill 12 and moves the workpiece 2 relative to the electrode 10 in the horizontal direction. And is attached and supported via a saddle 6 of the X-axis moving mechanism.

The Z-axis quill 12 is a rotary type in which a linear guide device such as a cross roller guide (not shown) is guided and held by the column and the machining head 8 by a hydrostatic bearing device, and a ball screw and a nut (not shown) are used for linear feed conversion. Z-axis drive device 1 consisting of a servo motor or a linear motor
1 sends it straight to the Z-axis.
The position of the shaft quill 12 is detected by a Z-axis linear encoder 14 which is a combination of a linear scale and a sensor between the quill and the fixed portion, and a Z-axis drive device 11 is instructed by a command from an electric discharge machining control means 22 having an NC device. The detected position signal is fed back to and controlled by the Z-axis motor drive control means 16 that has operated.

The X-axis and Y-axis moving mechanism 6 described above is used.
Also in 4 and 4, respectively, linear guide holding mechanisms (not shown), axis drive devices having motors, axis linear encoders 9 and 7, and axis motor drive control means 5 and 3 respectively.
Of course, the position of the workpiece 2 on the XY2 axes in the horizontal direction with respect to the Z-axis electrode 10 is controlled so that the operation of the command from the machining control means 22 matches the position.

An electric discharge machining power supply circuit means 18 for applying a machining voltage is connected between the machining electrode 10 and the workpiece 2 and a machining state between them, for example, a gap between the electrodes. The electric discharge machining state detecting means 20 for detecting the voltage and the machining current is connected, and the detected value is
It is input to the processing control means 22. The control means 22 is connected to a display means such as a CRT or LCD and an input means 26 such as a keyboard, and is also capable of inputting from an external recording medium 28 such as a flexible disk or HD. In such a processing device, the control means 2 is operated in accordance with a processing command from the input means 26 or a processing command of the NC program recorded in the recording medium 28.
The reference numeral 2 sends a command to the power supply circuit means 18 based on the setting of electrical processing conditions such as the current peak value and the on-time of the gate of the transistor constituting the circuit, and the drive control means 16 of the drive device having each axis motor. The position command signals are sequentially output to 5 and 3 to advance the machining by numerical control.

Therefore, the relative positioning between the workpiece 2 and the machining electrode 10 in such a machining apparatus is as follows.
For example, a contact sensing control means 19 which may be also used for the electric discharge machining power supply circuit 18 is connected between the two to apply a contact sensing voltage, and it is detected that both are in a predetermined contact state to detect a contact sensing signal. To the control means 22, and the positioning operation until the control means 22 detects and stores the position of each axis with respect to the origin at that time, a positioning program by contact detection from the recording medium 28 in the control means 22 or the like. It turns out that can be done using.

[0008]

However, in such a method, the positioning accuracy is set to high accuracy of the order of nm (nanometer), and such high-precision positioning is performed rapidly with high repeat accuracy in a short time. There were many problems to solve before we could do it. That is, a laser interferometer or the like is conventionally used for such high-accuracy measurement and positioning, but for measurement with a work piece, a tool, an electrode, or the like attached, the problem of installation, arrangement, and a polluted environment, etc. It was difficult because Therefore, an object of the present invention is to enable high-accuracy positioning quickly by using a simple method called contact sensing.

[0009]

The above-mentioned objects of the present invention are as follows.
(1) In a method of applying a predetermined voltage between two objects having at least a part of a conductor, and detecting the proximity contact between the two, and performing positioning, after the mechanical origin return operation process, the two are brought into proximity contact by relative movement. And a step of relatively moving the parts to be separated and positioned so as to be opposed to each other at a predetermined distance along the relative movement axis, and to move the both at a set speed from the opposed position to the movement axis. A first contact sensing step of moving close to and stopping along the contact point; a step of retracting and stopping a predetermined minute distance along the moving axis until the contact sensing is released from the stop position; A minute length that is sufficiently smaller than the distance is set as the minimum setting unit of the movement amount, and the proximity movement from the retraction stop position to the contact due to the relative movement is set to the above-mentioned setting. And a second movement step, which is performed by performing the minimum movement unit as a minimum movement unit and at a preset predetermined speed, detects the contact detection of the both, stops the operation, and stores the position. A method of positioning a machine tool, comprising the steps of returning from the storage position to the opposite position by relative movement, and positioning the second contact-sensing storage positions of the both with respect to the machine origin. It

Further, the above-mentioned object of the present invention is: (2) The minimum setting unit of the moving amount to be set is 1 nm, and the speed command for the set predetermined speed is 0.1 mm / min. This is achieved by the method for positioning a machine tool described in (1).

Further, the above-mentioned object of the present invention is: (3) Positioning of the machine tool according to (1) or (2), wherein one of the two objects of the relative positioning is a workpiece and the other is a cutting tool. It is achieved by the method.

Further, the above-mentioned object of the present invention is: (4) The machine tool according to (1) or (2), wherein one of the two objects for relative positioning is a workpiece and the other is an electrode for electric discharge machining. It is achieved by the positioning method of.

Further, the above-mentioned object of the present invention is described in the above (1), (2), (3) or (4), wherein the moving axis of the relative movement is the moving axis of the Z-axis main axis. It is achieved by the method of positioning a machine tool of.

Further, the above-mentioned object of the present invention is: (6) The above-mentioned (1), (2), (3), or (3) in which the movement axis of the relative movement is a composite axis of two or more orthogonal axes. This is achieved by using the machine tool positioning method described in (4).

[0015]

1 is a block diagram of a Z-axis motor drive control means 16 used for implementing the present invention, in which the contact detection control means 19 is additionally provided. The drive control means 3 and 5 for the two horizontal axes of the Y axis are different only in the stroke of each axis and the power.
Others are omitted because they are substantially the same.

The servo motor drive control means 16 is mainly composed of a position control unit 13, a speed control unit 15, a current control unit 17, and a contact detection control means 19. The position command signal A input from the electric discharge control means 22 including a numerical control device is detected by the Z-axis linear encoder 14 and fed back by the position detection signal B in the input subtraction section 21 of the position control unit 13. The subtracted position deviation signal C is input to the position control unit 13 and is calculated by a calculation unit with a predetermined proportional gain to generate and output a speed command signal D. In order to speed up the response to the position command, a feedforward unit (not shown) or the like is attached as needed.

The speed command signal D is obtained by calculating the feedback position detection signal B in the subtracting section 23 and calculating the feedback position detection signal B in the calculating section 25 after addition of output signals of a feedforward unit or the like provided as necessary. The speed control unit 15 becomes the speed deviation signal F by subtracting the speed signal E
The current command signal G is generated and output by performing an integration operation and an integration operation using a predetermined proportional gain or the like in the operation unit.

The current command signal G is added to the output signal of the feedforward unit or the like, and then subtracted by the subtraction unit 27 in the current control unit 17 in the same manner as in the case of processing the speed command signal D. The current detector 30 detects the current J output from the servo amplifier 29 to the servomotor of the Z-axis drive device 11 by the current command, and subtracts it from the fed back current detection signal H to obtain the obtained current deviation I. The current control unit 17 operates so as to be input and calculated, and to output to the servo amplifier 29 a current command K that commands the output of the drive current J. As described above,
The servo motor drive control means 16 receives the feedback of the detected position signal from the Z-axis linear encoder 14, and the speed control unit 15 that processes the speed signal instructs the position that the position control unit 13 that processed the position signal indicates. The drive current J is output to the servo motor of the Z-axis drive device 11 so that the Z-axis quill 12 moves at a speed.
The control loop from the feedback of the position signal to the output of the drive current is repeated with a cycle time of, for example, about 500 μs.

The present invention uses the axial movement control means 16 as shown in FIG. 1 and operates by an NC positioning program utilizing the contact detection control means 19 to perform positioning. As an example, a description will be given of a case where the above-mentioned touch sensing operation portion is processed by a motion program (G140) and other positioning operations are correspondingly processed by a macro program. Since the present invention performs positioning with accuracy on the order of nm as the linear encoder 14 for each axis such as the Z axis, it is naturally high speed (for example, response speed: 300 mm / s) and high resolution (for example, ,resolution:
An analog output type detector having a period of 0.1379 (.mu.m) is used, and the detection signal is subjected to electrical interpolation processing (for example, 1/128) to enable divided reading.

In FIG. 2, a stylus or a reference sphere 10P is attached to the lower end of the quill of the machining head or the spindle in place of the electrode tool 10 or the cutting tool, and the workpiece 2 is provided with a predetermined positioning side surface or two back side surfaces. By sensing contact with
It is explanatory drawing of the operation which carries out an end surface positioning or centering operation.

Further, FIG. 3 shows the cutting edge portion 10A of the cutting tool.
Is an insulating or high-resistive material such as diamond, but the handle portion 10B to which the cutting blade portion 10A is attached is a conductor, and the lower tip of the cutting blade portion 10A and the lower end portion 10C of the handle portion 10B, for example. Is a highly accurate known positional relationship, the lower end surface 10C is used as a positioning reference surface on the tool side, and the predetermined positioning reference surface portion 2C on the upper surface of the workpiece 2 is used as the Z movement axis in this case. By facing each other in the direction and making contact detection by proximity movement and positioning,
It is explanatory drawing of the operation | movement which positions the lower end of the said cutting blade part 10A and the upper surface 2C of the workpiece 2 in the Z-axis direction.

Next, according to the NC program, a method of highly accurate positioning using the contact sensing control means 19 and the axis movement control device 16 of the present invention for each axis will be described with reference to FIG. 1, FIG. 2, FIG. The flow will be described with reference to FIG. S
01 to S10 indicate step numbers. The axis movement command speed F in the axis movement control means 16 can be selected from a minimum of 0.1 mm / min to a maximum of 1000 mm / min, but if the command speed is not set, 10 mm / min (F10) is set. Also,
The minimum setting unit for axis movement is 1 nm minimum to 0.1 μ maximum.
It is configured such that a program command can be made by selective setting between m.

First, in S01, the machining head or the spindle attached with the stylus or the reference sphere 10P returns to the origin by the relative axis movement with respect to the machining table attached with the workpiece 2, and a predetermined positioning is made with respect to the reference point of the machine. In the case of FIGS. 2 and 3, they are located at the position of 10P1.

In S02, the stylus or reference sphere 10P that has returned to the original position is the start position of the contact sensing control operation programmed by the machining table to which the workpiece 2 is attached, in the X-axis direction of the workpiece 2 in FIG. (Horizontal direction in the drawing)
At a predetermined position 10P2 in the X-axis direction (preferably the central position in the X-axis direction) on the upper surface of the workpiece 2 suitable for starting the centering operation by positioning the end faces in one direction or positioning both end faces, the above-mentioned origin From the return position 10P1 by the program setting and the like, for example, along the path-1 of the long dashed line,
It is set by axis movement. Then, here, the touch sensing control means 19 causes the stylus or the reference sphere 10P to be operated.
And the workpiece 2 are connected or activated.

In S03, the stylus or the positioning reference sphere 10P is NC along the X-axis which is the relative movement axis.
From position 10P2 to position 10 according to the macro program of
The stylus or the reference sphere 10P moves relative to P3 and further along the Y-axis to the position 10P4, and the stylus or the reference sphere 10P performs contact sensing with the reference side surface of the workpiece 2 in the X-axis direction by the X-axis movement. A position 10P4, which is preferably close to the left end face of the workpiece 2 for starting the positioning operation, is programmed. That is, since the position 10P4 is 0.1 μm which is the maximum when the minimum setting unit of the axial movement amount for the next contact detection is not set, and the speed command is 10 mm / min, the position 10P4 is the same as the left end face of the workpiece 2. The distance is preferably programmed to be within 10 mm.

The stylus or reference sphere 10P is located at a position 10P4 in which the positioning portion of the workpiece 2 directly faces the positioning position 10P1 for returning to the origin along the path-2 of the long broken line, along the relative movement X axis. The NC program described above can be created and activated to move to.

In the case of the cutting tool shown in FIG. 3, the tip reference end face 10C of the handle 10A having the cutting edge 10A attached thereto from the positioning position 10P1 for returning to the origin is the workpiece 2 as shown in S04. It can be programmed to directly move along the path-2 of the above-mentioned long dashed line so as to face the required reference surface portion 2C at a predetermined interval.

The relative movement along the path-2 indicated by the broken line of the long line may be movement on the two-axis synthetic axis along the ZY or ZX plane or movement along the three-axis ZYX synthetic axis. . It should be noted that the relative movements of the close contact and the separation between the workpiece 2 and the stylus or the tool 10P in the positioning operation using the contact sensing operation by the motion program in FIGS. 2 and 3 are described as uniaxial movements such as the X axis. However, it goes without saying that the relative movement may be movement on a multi-axis composite axis of one or more axes.

Then, from S05, the motion program (G140 X (Y, Z) U V W F
Sequentially actuated by the positioning subprogram of the touch sensitive control programmed by _). First, the relative axis movement of X + indicated by the arrow of the two-dot broken line with the reference numeral is 1 nm to 0.1 μm, usually 0.1 μm, which is the minimum setting unit and the minimum movement unit, until the touch sensing control means 19 operates. , And the first touch sensing step of coarse positioning is performed in which the velocity command is moved at a setting of 10 mm / min and the touch sensing is stopped.

Next, the movement of the solid arrow marked with a symbol in S06 is a relative backward axis movement for releasing the contact state between the workpiece 2 and the stylus or the reference sphere 10P in the previous step, and Since it is located near the positioning position due to the stop of contact detection in the process, it is immediately detected by the detection of the contact state so as not to greatly move and increase the movement processing time of the second contact detection step of the precise positioning in the next process. It is preferable to stop or set UX-0.01 so that the contact state is released by retracting 0.01 mm from the contact stop position.

Next, in S07, the movement of VX + indicated by the broken line arrow with a symbol until the contact is made again detects the position of the target positioning in the minute retreat path of the previous process more accurately by contact sensing. The minimum setting unit and the minimum movement unit are 1 to 100 nm, the finer positioning is 1 nm, and the speed command is 0.1 mm / mi.
The setting of the motor drive control means 16 is switched to n and moved until contact sensing works, and from this, the position signal at which the second contact sensing works or the position signal stopped by working is detected and fed back from the linear encoder 14 of the moving axis. The positioning is performed and the positioning position is stored in the storage device of the control means 22.

After this precise positioning is completed, the stylus or the reference sphere 10P is opened from the workpiece 2 to end the contact sensing positioning of the subprogram at S10, or temporarily interrupted, and the mirror image function is operated to activate the core. Out S
In order to operate so as to perform 09, the distance to return to the position 10P4 at which the first touch sensing is started, or to retreat along the movement axis as shown in S08, for example, 1.0 mm
Then, the WX-1 is moved as indicated by a solid arrow with a reference numeral to complete the contact positioning of the subprogram.

When this positioning is end face positioning,
As described above, the position processing is performed in S10, the detected positioning position is stored in the storage device, the positioning operation is ended, and the NC program such as the next cutting process is executed. In the case of centering the electrode or tool such as the workpiece 2 or the stylus or the reference sphere 10P, the mirror image function of S09 is activated to perform the contact sensing and positioning operation between the end face of the workpiece 2 and the end face facing back. Move.

The positioning of the tip of the cutting tool in the Z-axis direction of FIG. 3 or the upper surface of the workpiece 2 is performed by replacing the X-axis of FIG. 2 with the Z-axis as shown in the figure, and therefore the same procedure as described above is performed. Since it is clear that the above-described positioning in the Z-axis direction is possible, the description thereof will be omitted.

The outline of the positioning method using the touch sensing according to the present invention has been described above. In the present invention, the touch sensing positions of two objects to be touch-sensed by the first touch sensing performed first are as follows.
It is detected as a position near the target positioning position, and the minimum setting unit and minimum movement unit can be set to a predetermined, normal setting from the retracted position that is a minute distance from the first touch sensing positioning position near the positioning position. The minimum contact length is set by the second contact sensing process that causes the proximity contact movement by the digital movement of the minimum movement unit to be executed as the movement based on the speed command of a sufficiently low speed and the normally settable minimum speed. The accuracy can be improved.

[0036]

As described in detail above, according to the present invention, high-accuracy positioning such as electric discharge machining or cutting can be performed quickly by using a simple method called contact sensing between a workpiece and an electrode or a tool. In addition to being surely performed, it has a capability of finishing the dimension and shape accuracy within 50 nm in ultra-precision cutting using a diamond tool, for example.

[Brief description of drawings]

FIG. 1 is a block diagram of a moving shaft motor drive control means used for implementing the present invention.

FIG. 2 is an explanatory view in the case where the processing operation of the touch sensing of the present invention is performed in the horizontal axis direction between the electrode (stylus) or the tool (reference sphere) and the workpiece.

FIG. 3 is an explanatory view of the case where the touch sensing processing operation is performed in the Z-axis direction.

FIG. 4 is a flow diagram of a positioning process operation using touch sensing according to the present invention.

FIG. 5 is an explanatory diagram of a configuration of a die-sinking electric discharge machine which is one of machine tools to which the positioning method of the present invention can be applied.

[Explanation of symbols]

1, bed 2. Workpiece 3, 5, 16, each motor drive control means 4. Moving body of Y-axis moving mechanism 6. Saddle for X-axis movement mechanism 7, 9, 14, linear encoders for each axis 8. Z-axis processing head 10, processing electrode 11, Z-axis drive 12, Z axis quill 13. Position control unit 15, speed control unit 17, current control unit 18, EDM power supply circuit means 19, touch sensing control means 20, EDM state detection means 21, 23, 27, subtraction unit 22, EDM control means 24. Display means 25, speed calculator 26, input means 28, recording medium 29, Servo amplifier 30, current detector 10A, cutting diamond 10B, handle 10C, lower end surface 2C, reference surface 10P, electrode (stylus) or tool (reference sphere) 10P1-10P4, position

Claims (6)

[Claims] 1. A method of applying a predetermined voltage between two objects having a conductor part at least in part to detect proximity contact between the two objects for positioning, and after the mechanical origin returning operation processing, both are moved by relative movement. A step of relatively moving the parts to be positioned by bringing them into close contact with each other and separating them from each other at a predetermined speed along the relative movement axis so that they are opposed to each other at a predetermined distance, A first contact sensing step of moving the arm closer to contact with the moving axis until it stops, a step of retracting a predetermined minute distance along the moving axis and stopping until the contact sensing is released from the stop position, Set a minute length that is sufficiently smaller than the retracted minute distance as the minimum setting unit of the movement amount,
The proximity movement from the backward stop position to the contact by the relative movement is performed by setting the set minimum setting unit as the minimum movement unit and at a predetermined speed set, and detecting the contact between the two. A second touch sensing step of detecting and stopping, and storing the position, a step of returning from the stored position to the facing position by relative movement,
A method of positioning a machine tool, comprising the step of positioning the second touch sensing storage position of both of them with respect to the machine origin. 2. The minimum setting unit of the moving amount to be set is 1n.
In m, the speed command of the set predetermined speed is 0.1 m
The machine tool positioning method according to claim 1, wherein m / min. 3. The method for positioning a machine tool according to claim 1, wherein one of the two objects for relative positioning is a workpiece and the other is a cutting tool. 4. The method for positioning a machine tool according to claim 1, wherein one of the two objects for relative positioning is a workpiece and the other is an electrode for electric discharge machining. 5. The method for positioning a machine tool according to claim 1, wherein the movement axis of the relative movement is a movement axis of a Z-axis main axis. 6. The moving axis of the relative movement is a multi-axis composite axis of two or more axes orthogonal to each other.
The method for positioning a machine tool according to 2, 3, or 4.