JPH04336942A - Tracer control device - Google Patents

Abstract

PURPOSE:To avoid bite to a work by delaying a machine shop tool against a tracer head by a given time and by forming a correction command always complied with the displacement of a copying shaft. CONSTITUTION:There is provided an auxiliary shaft control means for driving a tracer head on each shaft of a machine shop tool by a submotor 37 superimposed on a main motor 36 respectively. A correction arithmetic means 5 determines a correction command value VxC to a feed shaft driving command by multiplying a displacement amount epsilonX accepted by the tracer head against every feed shaft by a predetermined correction gain. A copying speed command value Vx is corrected based on the correction command value VxC and is then temporarily stored in a delay memory means 1 and is finally outputted by delaying against each shaft of a machine tool by a predetermined time. A speed command value obtained by reducing the feed shaft driving command from the copying speed command value is given to the auxiliary shaft control means.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to a profile control device.
In particular, the present invention relates to a tracing control device that changes the cutter path at a corner when a tracer head traces a model prior to machining with a cutter.

0002

2. Description of the Related Art Conventional profiling control devices perform profiling control on the premise that the cutter (tool) shaft of a profiling machine tool is mechanically coupled integrally with a tracer head. That is, the profiling control device detects the amount of displacement of each axis applied to the stylus using the tracer head, and uses this amount of displacement to calculate a speed command for each axis in the profiling calculation circuit. Then, the motors of each axis are driven by this speed command to move the cutter relative to the workpiece, and the tracer head is moved along the model surface at the same speed. By repeating these operations, tracing control is executed to process the workpiece in the same shape as the model.

[0003] In this way, when a conventional profiling control device moves a tool such as a cutter and a workpiece relative to each other using a profiling speed command value, the tracer head and the tool are moved together and simultaneously by the feed axis drive command formed. In particular, the tracer head did not have the function of leading the tracer head relative to the cutter shaft.

0004

[Problem to be solved by the invention] However, when tracing a model with a stylus provided at the tip of the tracer head,
When the stylus hits a corner of the model, it is equivalent to the tracer head temporarily biting into the model. This is because the tracer head tends to go too far due to delays in the servo system that constitutes the drive section of the tracer head, inertia of the machine, and other factors.

As a result, the cutter also bites into the workpiece by the same amount as the tracer head, reducing machining accuracy at the corner. Therefore, the inventor previously proposed and filed an application for a tracing control device that can delay the tool for a certain period of time with respect to the tracer head and trace the same path.
121, submission date February 5, 1991).

According to the above proposal, an auxiliary axis for driving the tracer head is provided superimposed on each feed axis on each axis of the machine tool, and this auxiliary axis is controlled by an auxiliary axis control means, so that the tracer head is connected to the tool. Take the lead and align the model. As a result, it is possible to detect biting of the tracer head in a part of the model where the shape changes suddenly, such as a corner, and prevent biting in the corner during tracing machining using a tool.

[0007] With the profiling control device proposed above, it is possible to detect a sudden change in shape, but if the cutter simply follows the path of the tracer head with a certain amount of delay,
Biting cannot be prevented, and if biting occurs, the movement of the cutter must be forcibly stopped. Alternatively, if continuous tracing machining is to be performed using a tool, it is necessary to change the tool path at a portion of the model where the shape changes suddenly, both of which cause a decrease in machining accuracy. The present invention was made in view of these points, and it prevents the tool from digging into the workpiece by constantly forming a correction command according to the displacement of the tracing axis while delaying the tool relative to the tracer head for a certain period of time. It is an object of the present invention to provide a profiling control device that can reliably avoid this.

[0008]

[Means for Solving the Problems] In order to solve the above problems, the present invention calculates the displacement amount detected by the tracer head to obtain a tracing speed command value for each axis of the tool, and uses these tracing speed command values. In the profiling control device that forms a feed axis drive command for relatively moving the tool and the workpiece, controlling an auxiliary axis provided superimposed on the feed axis,
auxiliary axis control means for moving the tracer head relative to the model parallel to the feed axis; a correction calculation means for determining a correction command value; a delay storage means for delaying and outputting a feed axis drive command corrected based on the profiling speed command value and the correction command value; and the delay storage means. profiling control characterized in that it has a subtraction means for subtracting the value of the feed axis drive command delayed and output from the profiling speed command value and outputting the speed command value to the auxiliary axis control means. Equipment is provided.

[0009]

[Operation] The tracer head has an auxiliary axis superimposed on the feed axis for each axis of the tool, and the tracer head is controlled by the auxiliary axis control means, so the tracer head is driven independently of the tool axis. Ru. The correction calculation means determines a correction command value for the feed axis drive command by multiplying a displacement amount received by the tracer head for each feed axis by a predetermined correction gain. After the profiling speed command value is corrected based on the correction command value, it is temporarily stored in the delay storage means, and is output to each axis of the machine tool with a predetermined time delay. The auxiliary axis control means is given a speed command value obtained by subtracting the feed axis drive command from the profile speed command value. As a result, the tracer head is placed in front of the tool axis to align the model, and the tool is controlled by a corrected path command that is different from the path of the tracer head relative to the model to prevent digging. Can be done.

0010

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing the main control elements of the profile control device. The figure shows only the configuration of the part corresponding to the X-axis of the three axes that control the tool, but
For example, the Y-axis or Z-axis control elements are similarly configured.

[0011] The tracing speed command value Vx in the X-axis direction is obtained at a constant calculation cycle by tracing the amount of displacement detected by the tracer head. This profiling speed command value Vx is input to the FIFO memory 1 via the synthesis circuit 2 as a feed axis drive command. The FIFO memory 1 is a so-called first-in first-out delay storage means having a delay buffer function.

The profiling speed command values Vx are stored in the FIFO memory 1 as a plurality of feed axis drive command data in the order in which they are input, and when the storage capacity is full, the data are output in the order starting from the data input first. Therefore, the profiling speed command value Vx is stored in this FIFO memory 1 for a certain period of time, so that it can be used as the X-axis drive command VxB delayed by the necessary time to drive the X-axis main motor (Xm) 36.
is output to. Note that the delay time of the FIFO memory 1 can be freely set by an external delay time setting signal, etc., depending on the distance that the tracer head should precede the tool.

The profile speed command value Vx is further inputted to a subtraction circuit 3 as an addition signal. This subtraction circuit 3
Now, from the profiling speed command value Vx, the FIFO memory 1 is
The delayed X-axis drive command VxB is subtracted. The subtraction result of the subtraction circuit 3 is further corrected by a correction arithmetic circuit 4 and output as a speed command value to the X-axis sub-motor (Xs) 37.

Incidentally, in addition to the profile speed command value Vx, a correction command value VxC is inputted to the synthesis circuit 2 from a correction calculation circuit 5. The correction calculation circuit 5 uses this correction command value Vx
A predetermined calculation period (i, i+
1, i+2,...). The profiling speed command value Vx is combined with the correction command value VxC commanded from the correction calculation circuit 5 in the synthesis circuit 2, and inputted to the FIFO memory 1 as the X-axis drive command VxB.

In the correction calculation circuit 5, the correction gain G is determined according to the amount of bite of the tracer head and the diameter of the tool for machining the workpiece, and is set from the outside. Further, the amount of displacement εxi that the tracer head receives is inputted every predetermined calculation time s, and the correction command value VxCi is calculated sequentially from the following equation. VxCi=εxi×G/s
...(1)

Since the correction command value is determined every predetermined calculation cycle in accordance with the amount of displacement that the tracer head receives, a corrected path is always commanded to the tool. therefore,
When the tracer head detects a sudden change in shape, the main motor 36 not only controls the path of the tracer head so that the tool follows it with a certain amount of delay, but also sets a correction command value VxC to prevent digging. This enables continuous tracing machining while avoiding the tool from digging into the workpiece. Note that the correction calculation circuit 5 determines a correction command value VxCi according to the difference between the displacement vectors εx, εy, εz of each axis of the tracer head and the reference displacement every predetermined calculation cycle, and sends it to the synthesis circuit 2. It may be combined with the irregular speed command value Vx.

Furthermore, the tracer head temporarily differs from the cutter's movement locus due to the X-axis drive command VxB following the correction command value VxC and fluctuating from the speed command value Vx. Therefore, for example, a signal for correcting the speed command value to the X-axis sub-motor 37 is formed based on the distance that the tracer head actually leads with respect to the tool (actual leading amount La), and the correction arithmetic circuit 4 I am trying to input it into .

Regarding this point, the configuration corresponding to the correction of the advance amount in FIG. 1 will be further explained. Arithmetic circuit 6
is for subtracting the X-axis drive command VxB delayed by the FIFO memory 1 from the profile speed command value Vx, and corresponds to the arithmetic circuit 3. The subtraction result is inputted to the register circuit 7 as a command advance amount (theoretical advance amount) L after converting the speed command into a position command. The data stored in this register circuit 7 indicates the current value of the command leading amount L which is commanded from the tracing control device to the tracer head which is to precede the movement of the cutter. On the other hand, the actual lead amount La of the tracer head is stored in the register circuit 8 as a feedback signal fed back from the sub-motor for each axis. The outputs of these two register circuits 7 and 8 are compared in an arithmetic circuit 9. That is, the commanded advance amount L is input as a subtraction signal and the actual advance amount La is input as an addition signal to the arithmetic circuit 9, and a correction signal for the X-axis sub-motor is calculated as the difference between these L and La. Arithmetic circuit 9
The output is multiplied by a predetermined gain G1 in a constant circuit 10 and used as a subtraction signal for the correction arithmetic circuit 4.

In this way, when outputting the distributed profiling speed command value Vx etc. of each axis to the cutter side, the FIFO
A feed axis drive command is output from the memory 1 to the main motor 36 after being delayed by a necessary time. The relative movement between the tracer head and the model is controlled equivalently to the profiling speed command value Vx by the sub motor 37 which is controlled superimposed on the movement of the main motor 36. Therefore, the tracer head can be placed in front of the tool axis to align the model, and the tool can be controlled by a corrected path command different from the path of the tracer head with respect to the model.

In addition, in the profiling control device of the present invention, since feedback control is applied to the lead amount for each axis so that the actual lead amount La always matches the command lead amount L, the command speed based on the model shape Even if there is a fluctuation in the cutter, the cutter movement trajectory is always controlled along a path that corrects the amount of displacement from the tracer head.

FIG. 2 shows an example of the relationship between the cutter path, the tracer head path, and the correction speed in the XZ plane. Now, the profiling speed command Vx calculated by the profiling calculation,
Vz causes the tracer head to change the velocity vector V1,
It is assumed that the model moves from the coordinate point Pt based on V2 and V3, and the amount of intrusion becomes large at a part where the shape of the model suddenly changes. From equation (1) above, the X-axis component of the corrected velocity vectors VC1, VC2, VC3 can be calculated using the displacement εx generated on the tracing axis and the set gain G, and in the same way, the Z-axis component can be calculated using the displacement εz. can.

[0022] Then, a command speed vector VB1 that determines the corrected cutter path from the coordinate point Pc of the cutter head.
, VB2 and VB3 are determined as follows. VxBi=Vx(i)+
VxC(i)-VxC(i-1)
VzBi=Vz(i)+VzC(i)-VzC
(i-1) Here, i is the value in the current calculation cycle, i-1
indicates the value in the previous calculation cycle, and the velocity component Vx(i
), Vz(i) is actually a delayed storage means FIF
A value delayed by the delay in O memory 1 is used. That is, the difference in the correction command value obtained by multiplying the displacement amount of each axis received by the tracer head by a predetermined correction gain G is VxC(i)-
The corrected speed obtained by tracing VxC(i-1), VzC(i)-VzC(i-1) and adding them to the speed command values Vx(i-1) and Vz(i-1), respectively, is the axis drive command VxB( i)
, VzB(i) in the FIFO memory 1.

If the FIFO memory 1 outputs each axis drive command VxB(i), VzB(i) to the main motor 36 with a delay of, for example, 10 calculation cycles, the cutter will arrive at the coordinate point Pc with a delay of that amount. . Therefore, even if the speed vector of the tracer head increases from V1 to V2 at a sudden shape change part of the model and the amount of biting increases, the cutter head will be moved by the corrected drive command V of each axis.
The cutter path is determined according to xB(i) and VzB(i).

FIG. 3 is a block diagram showing the overall configuration of the profiling control device and profiling machine tool of the present invention. In the figure, a tracing control device 20 includes a CPU 11 that executes tracing calculations and the various calculations described above, a ROM 12 that stores a control program, a RAM 13 that corresponds to storage means such as the register circuits 7 and 8, and a nonvolatile memory 14. are doing. The nonvolatile memory 14 is backed up by a battery (not shown), and stores various parameters related to the tracing direction, tracing speed, etc. that are input from the operation panel 21.

The servo amplifiers 22 and 23 receive feed axis drive commands from the profile control device 20 and drive main motors for the X-axis, Z-axis, etc. In addition, the servo amplifier 24
, 25 receive an auxiliary axis drive command from the profile control device 20 and drive sub motors for the X axis, Z axis, etc. In order to enable three-dimensional profiling, the profiling machine tool 30 is provided with auxiliary axes parallel to and superimposed on the feed axis for each of the three axes including the Y-axis (not shown). Then, the tracer head 31 on the tracing machine tool 30 side detects the displacements εx, εy, and εz in the X-axis, Y-axis, and Z-axis directions caused by the stylus 32 at its tip coming into contact with the model 33, and performs tracing. It is input to the control device 20.

[0026] The cutter 34 is attached to the column 35,
The column 35 is moved in the Z-axis direction by a main motor 36zm. In addition, the column 35 has a sub motor 37zs
and 37xs are installed, and these sub motors 3
7zs and 37xs, the tracer head 31 further moves in the Z-axis direction and the X-axis direction superimposed on the movement of the column 35. The workpiece 38 and the model 33 are fixed on a table 39, and the table 39 is moved in the X-axis direction by a main motor 36xm.

[0027] And the main motors 36xm and 36z
m rotates according to feed axis drive commands Vxm and Vzm,
The sub motors 37xs and 37zs rotate according to speed command values Vxs and Vzs calculated from the tracing speed command value, and drive the tracer head in advance of the cutter head.

In the profiling machine tool 30 having the above configuration, the cutter 34 passes through the cutter 34 after a certain time delay while the profile control device 10 corrects the path traversed by the tracer head 31. That is, the tracer head 31 traces the model 33 in advance of the cutter 34, and the cutting path by the cutter 34 is corrected according to the biting state of the tracer head 31. Therefore, when biting occurs, the path can be corrected so as not to cut into the workpiece 38 without forcibly stopping the movement of the cutter, and continuous tracing machining can be performed.

In the above explanation, the correction calculation circuit 5 multiplies the amount of displacement received by the tracer head by a predetermined correction gain to determine the correction command value for the feed axis drive command.
The correction command value may be determined in accordance with the difference between the displacement vector components εx, εy, εz of each axis of the tracer head and the reference displacement at each predetermined calculation cycle.

[0030]

Effects of the Invention As explained above, in the present invention, an auxiliary axis is provided to drive the tracer head independently of the tool axis, and by controlling the movement of the tool to delay it, the tracer head appears to be ahead of the tool. It is possible to reliably avoid tool digging by moving the tool at the following speed command value. Moreover, by controlling the tool using a corrected path command that is different from the path of the tracer head with respect to the model, it is possible to perform continuous tracing machining on the workpiece while preventing biting. Therefore, highly accurate tracing control is realized in which the cutter does not dig into the workpiece at the corner portion.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing main control elements of a profiling control device of the present invention.

FIG. 2 is an X-Z plan view showing an example of the relationship between the cutter path, the tracer head path, and the correction speed.

FIG. 3 is a block diagram showing the overall configuration of the profiling control device and profiling machine tool of the present invention.

[Explanation of symbols]

1 FIFO memory 2 Synthesis circuit 3 Subtraction circuit 4. Calculation circuit for correction 5 Correction calculation circuit

Claims (3)

[Claims] 1. A tracing speed command value for each axis of the tool is obtained by tracing the displacement amount detected by the tracer head, and a feed axis drive command for relatively moving the tool and the workpiece is formed using these tracing speed command values. The tracing control device includes: an auxiliary axis control means for controlling an auxiliary axis provided superimposed on the feed axis to move the tracer head relative to the model parallel to the feed axis; a correction calculation means for determining a correction command value for the feed axis drive command by multiplying the amount of displacement received by the tracer head by a predetermined correction gain; a delay storage means for outputting a feed axis drive command delayed by a predetermined time; and a value of the feed axis drive command delayed and outputted by the delay storage means is subtracted from the profiling speed command value to control the auxiliary axis. 1. A tracing control device comprising: subtraction means for outputting a speed command value to the means. 2. The profiling control device according to claim 1, wherein the correction gain of the correction calculating means is determined according to the amount of bite of the tracer head and the diameter of a tool for machining the workpiece. 3. In the correction calculation means, a correction command value is determined in accordance with the difference between the components εx, εy, εz of the displacement vector for each axis of the tracer head and a reference displacement at each predetermined calculation cycle. 2. The tracing control device according to claim 1.