JPH04336943A - Tracer control device - Google Patents

Abstract

PURPOSE:To avoid the bite of a tool into a work, by carrying out a scaling process while delaying the tool for a specified time from a tracer head and using correction commands for auxiliary shafts. CONSTITUTION:A tracer control device is provided with an auxiliary shaft control means driving a tracer head for every shaft of a tool with respective sub-motors 37 superposed on a main motor 36. A correction culculating means 5 monitors the displacement of the tracer head, and when it exceeds a specified threshold value the means 5 decides a correction command value VxC for a feed shaft driving command. A tracer velocity command value Vx is corrected basing on the correction command value VxC, and N-times multiplied in a N-times multiplying circuit 1a, and delayed for a specified time T by means of a FIFO memory 1b to be outputted to the main motor 36. To the auxiliary shaft control means, a velocity command obtained by subtracting a feed shaft driving command NVx(t+T) from the tracer velocity command value Vx is applied.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tracing control device that changes the cutter path relative to the path of the tracer head at a corner when the tracer head traces a model prior to machining with a cutter. In particular, the present invention relates to a tracing control device that has a scaling function added to enable machining that expands or contracts a model shape.

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] As described above, 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 a feed axis drive command that is 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, the tracer head temporarily bites 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, on each axis of the machine tool,
Auxiliary axes are provided that overlap the respective feed axes, and the auxiliary axis control means causes the tracer head to precede the tool axis to 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] Although the profiling control device proposed above can detect a sudden change in shape, if the cutter simply follows the path of the tracer head with a certain amount of delay, it cannot prevent digging. Therefore, in order to perform continuous tracing machining using a tool, it was necessary to change the tool path at parts of the model where the shape changes suddenly, so that it differs from the path of the tracer head.

Furthermore, if the workpiece is a metal with a large coefficient of expansion, the size of the mold actually machined may differ from the profile model due to thermal expansion during cutting with a tool. . Therefore, a method has conventionally been used in which, for example, a slightly enlarged model shape is traced in advance with a tracer head, and the workpiece is cut to obtain the originally required mold. However, this method has a problem in that it requires a great deal of effort to create the model.

The present invention has been made in view of these points, and it performs scaling processing by delaying the tool relative to the tracer head for a certain period of time, and also prevents the tool from digging into the workpiece by a correction command to the auxiliary axis. It is an object of the present invention to provide a profiling control device that can reliably avoid this.

0010

[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 a profiling control device that generates a feed axis drive command for relatively moving the tool and workpiece, an auxiliary axis provided superimposed on the feed axis is controlled to model the tracer head in parallel to the feed axis. an auxiliary axis control means for moving the tracer head relative to the tracer head, and a correction command value for the feed axis drive command when a displacement amount exceeding a set threshold is detected; a correction calculation means for determining the value of the feed axis drive command; a command output means for multiplying the value of the feed axis drive command corrected based on the correction command value by a constant (N) and outputting the result after delaying by a certain time (T); A profiling control device is provided, comprising: subtraction means for subtracting the value of the feed axis drive command output by the output means from the profiling speed command value and outputting a speed command to the auxiliary axis control means. be done.

[0011]

[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 monitors the amount of displacement received by the tracer head, and determines a correction command value for the feed axis drive command when a displacement amount exceeding a set threshold is detected. The profiling speed command value is corrected based on the correction command value, and is output as a value scaled by N times with a delay of a certain time T to each axis of the machine tool. 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, the model shape is expanded or contracted by N times, and machining is applied to the workpiece, and the bite of the tracer head is detected at the corners of the model. By giving the corrected path command to the tool, it is possible to prevent biting at corners.

0012

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.

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 profile speed command value Vx is inputted to the N-times circuit 1a via the synthesis circuit 2 as the feed axis drive command Vx(t). This N-multiplying circuit 1a constitutes a command output means for a feed axis drive command together with a FIFO memory 1b which is a so-called first-in, first-out storage means having a delay buffer function.

The profile speed command value Vx is multiplied by N and stored in the FIFO memory 1b in the order in which it was input as a plurality of feed axis drive command data NVx(t). These feed axis drive command data are the feed axis drive command data NVx(t+T) delayed by a certain period of time T, in order from the first input data when the storage capacity of the memory 1b overflows.
is output as Note that the constant N of the N-multiplier circuit 1a and the delay time T caused by the FIFO memory 1b can be freely set by an external setting signal depending on the type of workpiece and the distance that the tracer head should precede the tool. .

The profile speed command value Vx is further input 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 feed axis drive command data NVx (
t+T) 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.

In this way, when outputting the distributed profiling speed command value Vx etc. of each axis to the cutter side, the command output means consisting of the N-fold circuit 1a and the FIFO memory 1b scales it by a factor of N. The sent feed axis drive command is delayed by the necessary time and output to the main motor 36. In other words, the N-fold circuit 1a expands or contracts the cutter movement by N times with respect to the model shape, and furthermore, it is stored for a certain period of time in the FIFO memory 1b, so that it is delayed by the necessary time. As the X-axis drive command NVx (t+T), the X-axis main motor (Xm)
36.

Note that the relative movement between the tracer head and the model is controlled equivalently to the tracing speed command value Vx by a sub-motor 37 which is controlled superimposed on the movement of the main motor 36. In other words, the amount of movement by the main motor 36 is
It is determined by the feed axis drive command data NVx (t+T) output from the FIFO memory 1b, and the sub motor 37
The amount of movement is determined by Vx(t)-NVx(t+T). Therefore, the relative movement amount of the tracer head as seen from the model is Vx(t). As a result, the sub-motor 37 moves the tracer head in advance of the movement of the cutter, and the tracer head movement trajectory seen from the model accurately matches the movement trajectory based on the speed command value Vx.

By the way, the synthesis circuit 2 includes a correction calculation circuit 5.
Correction command value VxC corresponding to the sudden shape change part of the model
is commanded and combined with the profile speed command value Vx. The feed axis drive command Vx(t) corrected based on this corrected command value VxC is input to the N-fold circuit 1a. A threshold value εt is set to the correction calculation circuit 5 from the outside, and the amount of displacement εi received by the tracer head is inputted at every predetermined calculation cycle. As will be explained later, in this correction calculation circuit 5, displacement vectors εx, εy, εz for each axis,
Based on the composite displacement amount ε determined from these displacement vectors εx, εy, and εz, the displacement amount εi received by the tracer head is monitored, and the threshold value ε set in the correction calculation circuit 5 is
At the time when a displacement amount εi exceeding t is detected, a correction command value VxC for the feed axis drive command Vx(t) is input. As a result, the profiling speed command value Vx and the correction command value VxC
An X-axis drive command having a size that is a composite of the above is determined.

In this way, when a sudden change in shape is detected, 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 adjusts the correction command value to prevent digging. By determining VxC, it is possible to perform continuous tracing machining while avoiding the tool biting into the workpiece. Furthermore, the movement loci of the tracer head and cutter temporarily do not match due to causes such as the X-axis drive amount varying from the speed command value Vx due to the correction command value VxC. 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 from the profile speed command value Vx to the above FIFO memory 1b.
This circuit subtracts the delayed feed axis drive command data NVx (t+T), and corresponds to the subtraction circuit 3 described above. After the subtraction result is converted from the speed command to the position command,
It is input to the register circuit 7 as the command advance amount (theoretical advance amount) L. The data stored in this register circuit 7 is
This shows the current value of the command leading amount L which is commanded by the tracing control device to the tracer head which is to precede the movement of the cutter. On the other hand, the actual leading amount La of the tracer head is
The signal 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 arithmetic circuit 9 receives the command advance amount L as a subtraction signal.
However, the actual advance amount La is input as an addition signal, and the correction signal of the X-axis sub-motor 37 is calculated as the difference between L and La in the calculation circuit 9. The output (L-La) of this arithmetic circuit 9 is multiplied by a predetermined gain G in a constant circuit 10 and is used as a subtraction signal for the arithmetic circuit 4 for correction.

[0021] Since the advance amount increases or decreases due to scaling, it is also necessary to consider the magnification N when setting the advance amount, that is, the delay time T. If it becomes necessary to consider the rate of expansion or contraction, the value of the feed axis drive command data NVx (t+T) output from the FIFO memory 1b is multiplied by 1/N and then input to the arithmetic circuit 6.

[0022] As described above, in the profiling control device of the present invention,
By tracing a model in advance, you can process a workpiece N times the size. Moreover, since feedback control is applied to the advance amount for each axis so that the actual advance amount La always matches the commanded advance amount L, even if there are fluctuations in the command speed based on the model shape, the The tracer head and cutter can be controlled so that their movement trajectories match. Note that the N-times circuit 1a and the FIFO memory 1 constituting the command output means
The output of the FIFO memory 1b may be expanded or contracted by the N-fold circuit 1a by switching the connection relationship with the FIFO memory 1b.

FIG. 2 illustrates the relationship between the displacement amount εi of the tracer head input to the correction calculation circuit 5 and the X-axis drive command VxB (or Z-axis drive command VzB) corrected by the correction command value VxC. This is a diagram. In the following explanation, the X-axis drive command VxB is used as the feed-axis drive command data NVx.
(t+T), and its N is assumed to be 1. (a) of the same figure is a diagram illustrating the biting of the tracer head 32 preceding the tool 34 in the case of tracing the contour of an internal angle in the X-Z plane. When the tracer head 32 moves at a corner, the displacement in the X-axis direction first increases, and the displacement in the Z-axis direction decreases after a delay. Generally, the direction of displacement occurs in the three axes of X, Y, and Z, so the composite displacement amount ε is determined from the displacement vectors εx, εy, and εz of each axis of the tracer head 32 so that ε2 = εx2 +εy2 +εz2. ing. Then, the difference from the threshold εt (ε−εt
) is calculated as the error displacement Δεi by the correction calculation circuit 5 at every predetermined calculation cycle.

FIG. 3B shows a change in the composite displacement amount εi at the position X2 of the tracer head 32 with respect to the time axis. When a displacement amount εi exceeding a threshold value εt is input at time t1, the correction calculation circuit 5 determines correction command values VxCi and VzCi based on the following equations. VxCi=VCi×cosθ−VN×cosθ
．． ．． ．． (1) VzCi=VC
i×sinθ−VN×sinθ
．． ．． ．． (2)

Here, VCi is a value obtained by dividing the error displacement Δεi by one calculation period s, and corresponds to the correction distance required to cancel the error displacement in one calculation period. VN is a value corresponding to a corrected velocity component in the model normal direction in the profiling calculation, and θ is a value corresponding to the profiling direction angle.

(c) of the figure shows the X-axis drive command VxB corrected by the correction command value VxC of the tool 34 when the tracer head 32 is at position X2. The X-axis drive command VxB is temporarily stored in the FIFO memory 1b,
Since the output is delayed by a certain time ΔT, if you freely set the distance that the tracer head 32 should lead,
- It is possible to reliably prevent the tool 34 from biting into the workpiece on the Z plane.

FIG. 3 shows an example of the relationship between the cutter path, the tracer head path, and the correction speed in the X-Z plane. Assuming that a displacement εi of the tracer head exceeding a threshold value εt is detected at the coordinate point P, the tracer head is moved with velocity components Vxi and Vzi determined by tracing calculation,
Difference V in correction command value determined according to error displacement Δεi
xC(i)-VxC(i-1), VzC(i)-VzC
(i-1), speed command values Vx(i-1), Vz(
The corrected speeds added to i-1) are stored in the FIFO memory 1b as each axis drive command VxBi, VzBi. The FIFO memory 1b transmits each axis drive command VxBi, VzBi to the main motor 3 with a delay of, for example, 10 calculation cycles.
6, the cutter path will arrive at the coordinate point P with a delay corresponding to that amount, and then the corrected each axis drive command V
The cutter path is determined according to xBi and VzBi.

FIG. 4 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 a feed axis drive command from the profile control device 20 and drive the main motors for the X-axis, Z-axis, etc. In addition, the servo amplifier 24
, 25 receive auxiliary axis drive commands 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.

[0030] 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.

[0031] And the main motors 36xm and 36z
m is rotated with a delay of a certain time T in accordance with the feed axis drive commands Vxm and Vzm, which are scaled values N times. Further, the sub motors 37xs and 37zs rotate according to speed command values obtained by subtracting the feed axis drive command from the profiling speed command value, as speed command values Vxs and Vzs different from the feed axis drive commands Vxm and Vzm.

In the profiling machine tool 30 having the above configuration, the profiling control device 20 multiplies the path traversed by the tracer head 31 by N times, and the cutter 34 passes along a trajectory similar to the model shape with a certain time delay. That is, the tracer head 31 follows the model 33 in advance of the cutter 34, and therefore the corner portion CN as shown in FIG.
When the tracer head 31 enters the biting state, the cutting path by the cutter 34 is corrected. A scaling function that takes into account thermal expansion of the workpiece can be added to such advance detection pattern. Therefore, even when scaling is performed by delaying the tool for a certain period of time with respect to the tracer head, the path can be corrected to prevent cutting into the workpiece 38 without stopping the cutter 34.

[0033]

Effects of the Invention As explained above, in the present invention, an auxiliary shaft is provided to drive the tracer head independently of the tool shaft, and even when the workpiece is a metal with a large coefficient of expansion, the heat generated during cutting by the tool can be reduced. Accurate tracing control is achieved by eliminating effects such as expansion. Further, by delaying the movement of the tool under control, the tracer head is apparently moved in advance of the tool at the tracing speed command value, thereby reliably avoiding tool bite. Moreover, by changing the tool path at parts of the model where the shape changes suddenly, continuous tracing machining can be performed on the workpiece.

[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 a diagram illustrating the relationship between the displacement amount εi of the tracer head and the corrected X-axis drive command VxB.

FIG. 3 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. 4 is a block diagram showing the overall configuration of the profiling control device and profiling machine tool of the present invention.

[Explanation of symbols]

1a N-fold circuit 1b FIFO memory 2 Synthesis circuit 3 Subtraction circuit 4. Calculation circuit for correction 5 Correction calculation circuit

Claims (2)

[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. In the tracing control device, 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, and the tracer head a correction calculation means for monitoring the amount of displacement received by the feed shaft drive command and determining a correction command value for the feed axis drive command when a displacement exceeding a set threshold value is detected; a command output means for multiplying the value of the feed axis drive command by a constant (N) and outputting it with a delay of a certain time (T); 1. A profiling control device comprising: subtraction means for subtracting a command value from a command value and outputting a speed command to the auxiliary axis control means. 2. The profiling control device according to claim 1, wherein the leading amount of the tracer head relative to the tool is determined by appropriately setting a constant N of the command output means and a delay time T thereof.