JPH06332512A - Method and device machining curved surface using nc machine tool - Google Patents

Abstract

PURPOSE:To ensure a machining operation at a high speed and with high accuracy by calculating a delay amount of the acceleration/deceleration control from the feeding speed of a spindle and correcting a machining program based on the calculated delay amount for shift of the spindle and machining of a curved surface. CONSTITUTION:An arithmetic unit 6 divides the moving amount of each axes 10-12 with the unit time based on a machining program and calculates the feeding speed of each axis. Then, the unit 6 calculates a delay amount from the feeding speed of each axis and the parameter of a memory 2. The delay amount of each axis is added to the moving amount of each axis of the machining program. The difference between the immediately precedent feeding speed and the read-out feeding speed is divided by the unit time to calculate the acceleration. A mechanical error is obtained based on an error table of the memory 2 against the acceleration and then added to the machining program of a memory 1 to acquire a command program. Then, the command program is sent to an NC device 8 via a communication interface 7, and the servo motors 10, 11 and 12 are actuated for the X, Y and Z axes respectively to shift a spindle.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a curved surface processing method and a curved surface processing apparatus by an NC machine tool, which is applied to the processing of a mold or the like whose processing surface is a curved surface.

[0002]

2. Description of the Related Art Usually, when a die having a complicated free curved surface is manufactured, a curved surface A is divided by a straight line B as shown in FIG. ing. In this method, when the linear command of the program is made fine and the interval C between adjacent line segments (see FIG. 11) is made small, the smoothness of the machined surface is improved,
The polishing time by hand can be shortened. But,
In reality, since the length of the machining program becomes long, the machining time becomes too long with the conventional feed rate, and the shortening of polishing cannot be used as an advantage overall.

[0003]

By the way, in recent years, NC
By increasing the equipment speed, it became possible to increase the feed rate, which made it possible to increase the die machining speed.However, when machining a free-form surface at a high speed, the actual radius of curvature of the free-form surface and the feed rate make it practical. The machining locus of is different from the command locus and cannot perform high-speed and high-precision machining.

The causes of the above-mentioned error in the machining locus in high-speed machining are as follows. (A) Radius reduction error between the delay due to the acceleration / deceleration control of the NC device and the delay due to the servo (an example of radius reduction when an arc command of 360 degrees on two axes is shown in FIG. 12). (B) If a small radius of curvature is to be machined at high speed, the acceleration will increase and a mechanical error will occur.

Among the error factors of the machining path in high-speed machining, the error ΔR1 due to the servo delay and the error ΔR2 due to the acceleration / deceleration control delay are expressed by the following equations (1) and (2). ΔR1 = V ² / (2 × Kp ² × R) (1) where, V: feed rate R: arc radius Kp: servo loop gain

ΔR2 = (V ² × T ² ) / (24 × R) (2) where V: feed rate T: linear acceleration / deceleration time constant after interpolation (time constant of acceleration / deceleration control) R: arc radius

From the above equation, in order to reduce the error, the servo loop gain Kp may be increased and the linear acceleration / deceleration time constant T after interpolation may be decreased. However, in practice, this constant is a mechanical condition, that is, the servo motor It cannot be changed from torque, etc., and remains constant.

For this reason, conventionally, a method has been adopted in which the speed is reduced when the radius of curvature of the free-form circular arc is small, and the feed speed is increased when the radius is large to make the error constant (Japanese Patent Application No. 63-264589). . This processing method has a drawback that it cannot be processed in the shortest time even though the motor has a sufficient torque.

The present invention is an NC machine capable of high-speed and high-precision machining.
An object of the present invention is to provide a curved surface processing method and a curved surface processing device using a machine tool.

[0010]

In order to achieve the above object, a curved surface machining method using an NC machine tool according to claim 1 is
In an NC machine tool that moves a spindle with a servo motor according to a machining program to perform curved surface machining, calculates the delay amount of acceleration / deceleration control from the feed rate of the spindle, corrects the machining program with the delay amount, and moves the spindle to perform curved surface machining. And

According to the curved surface machining method of claim 2, in an NC machine tool in which a spindle is moved by a servo motor according to a machining program to perform curved machining, a servo delay amount is calculated from the feed rate of the spindle and machining is performed with the delay amount. The program was corrected to move the spindle to make curved surface processing.

According to a third aspect of the present invention, in an NC machine tool in which a spindle is moved by a servomotor according to a machining program to perform curved surface machining, the acceleration of the spindle is calculated, a mechanical error due to the acceleration is calculated, and the machining program is calculated with the error. Was corrected to move the main axis to perform curved surface processing.

Further, according to the curved surface machining apparatus of claim 4, in an NC machine tool for machining a curved surface by moving a spindle by a servo motor according to a machining program, parameters for calculating acceleration / deceleration control and servo delay and spindle acceleration. And a storage means for storing an error table showing the relationship between the mechanical error and the spindle feed rate and the above parameters to calculate the acceleration / deceleration control and servo delay amount, and also calculate the spindle acceleration to calculate from the above error table. A mechanical error of the acceleration is calculated, a machining program is corrected based on the delay amount and the mechanical error, and is output to the NC device that controls the servo motor.

[0014]

According to the invention of claim 1, an error caused by delay of acceleration / deceleration control, an error due to delay of servo in the invention of claim 2, and a mechanical error due to acceleration in the invention of claim 3 are respectively described. It can be removed, and high-speed and high-precision machining is possible. Further, according to the invention of claim 4, one or more of the above three errors can be removed to perform higher speed and higher precision machining.

[0015]

1 to 8 show an embodiment of the present invention.
In these drawings, reference numerals 1 and 2 are memories. The machining program 3 (FIG. 2) is stored in the memory 1. In the machining program 3, the movement amount of the command of each axis (there are combinations of the X axis and the Y axis, the X axis and the Z axis, and the Y axis and the Z axis, but the X axis and the Y axis will be described below) is a unit. It is given by the moving distance per time (constant) and is in the form including the feed rate (binary form). XX (N-1) is the block number N
The X-axis movement distance of the main axis (not shown) at
(N-1) indicates the Y-axis movement distance of the spindle in the block number N.

Further, the memory (storage means) 2 has an X-axis error table 4 showing the relationship between the X-axis acceleration and mechanical error.
(Fig. 3) and Y showing the relation between Y-axis acceleration and mechanical error
Axis error table 5 (FIG. 4) and parameters T1, Tx, Ty, K for calculating the amount of delay between servo and acceleration / deceleration control.
px, Kpy (FIG. 5) are stored. The error tables 4 and 5 are created based on calculations, experiments, or the like.

Here, T1 is a unit time in binary format Tx is an X-axis acceleration / deceleration time constant Ty is a Y-axis acceleration / deceleration time constant Kpx is an X-axis servo loop gain Kpy is a Y-axis servo loop gain. .

An arithmetic unit 6 is connected to the memories 1 and 2. The arithmetic unit 6 has the following functions. (1) Read the machining program 3 of one block (N) from the memory 1 (if the previous machining program is not read, read the next one block).

(2) From the machining program 3, the moving amount of each axis is divided by the unit time to calculate the feed rate of each axis. (3) The delay amount is calculated from the feed rate of each axis and the parameters of the memory 2.

(4) The delay amount of each axis is added to the movement amount of each axis of the machining program. (5) Divide the speed difference between the immediately preceding feed speed and the read feed speed by the unit time to calculate the acceleration.

(6) A mechanical error corresponding to the acceleration obtained above is obtained from the error tables 4 and 5 of the memory 2, and the error is added to the machining program 3 of the memory 1 to obtain a command (correction) program. . (7) The above command program is output to the NC device 8 via the communication interface 7. The communication interface 7 transmits the command program of the arithmetic unit 6 at high speed to the NC unit 8 by high speed communication means to directly perform numerical control.

The NC device 8 is well known and operates the X-axis servo motor 10, the Y-axis servo motor 11 and the Z-axis servo motor 11 according to a given command program,
Move the spindle.

A calculation example of the arithmetic unit 6 will be shown. Previous block; X (x0), Y (y0) Current block; X (x1) Y, (y1) X-axis movement command; X (x0), X (x1) Y-axis movement command; Y (y0), Y (Y1) Movement amount of each axis; x0, x1, y0, y1 Delay amount due to X axis acceleration / deceleration time constant; Sx1 Y axis Delay amount due to acceleration / deceleration time constant; Sy1 Delay amount due to X axis servo loop gain; Spx1 Y axis Servo loop gain delay amount; Spy1 X-axis acceleration; Gx1 Y-axis acceleration; Gy1 Feed rate of each axis; Vx0, Vx1, Vy0, Vy1 Mechanical error corresponding to X-axis acceleration Gx1; Mx1 Corresponding to Y-axis acceleration Gy1 Mechanical error: My1 Vx0 = x0 / T1 Vx1 = x1 / T1 Vy0 = y0 / T1 Vy1 = y1 / T1 Sx1 = 1/2 × Vx1 × Tx Sy1 = 1/2 × Vy1 × Ty Spx1 = Vx 1 / Kpx Spy1 = Vy1 / Kpy Gx1 = (Vx1-Vx0) / T1 Gy1 = (Vy1-Vy0) / T1 Command program corrected from machining program (x1) =
(X1 + Sx1 + Spx1 + Mx1) Command program corrected from machining program (y1) =
(Y1 + Sy1 + Spy1 + My1)

Next, the curved surface processing method of the present invention will be described with reference to the flowcharts of FIGS. The arithmetic unit 6
Has arithmetic registers R1, R2 to R20. When the curved surface processing is started, the initial setting is performed, the block number is set to N = 1, and the registers R1 to R20 are set to 0 (step S1). Then, the program 3 of the block number N in the memory 1 is set to the register R1. Transfer to R2 (step S2).

Next, the arithmetic unit 6 transfers the contents of the registers R1 and R2 to the registers R9 and R10 (step S
3), the contents of the registers R9 and R10 are sent to the communication interface 7, and the communication interface 7 transmits it to the NC device 8 (step S4).

Next, the arithmetic unit 6 calculates N = N + 1 in preparation for reading the next block (step S
5) Calculate the speed of each axis and register the result in the register R5
The data is stored in R6 (step S6). In step S7, the arithmetic unit 6 calculates the delay amount and stores the result in the registers R13 and R14.

Further, the arithmetic unit 6 calculates acceleration and stores the result in the registers R11 and R12 (step S
8) After that, the error tables 4 and 5 of the memory 2 are searched from the accelerations stored in the registers R11 and R12, and the mechanical errors Mx and My are obtained and stored in the registers R17 and R18 (step S9).

Next, the arithmetic unit 6 registers the registers R1 and R2.
Is transferred to the registers R3 and R4, the contents of the registers R5 and R6 are transferred to the registers R7 and R8 (step S10), and the program 3 of the block number N of the memory 1 is transferred to the registers R1 and R2 (step S11). . The arithmetic unit 6 adds the above delay amount and mechanical error to the machining program 3 of the memory 1 in the next step S12,
The contents of the registers R13 and R14 are stored in the registers R15 and R1.
6, the contents of registers R17 and R18 are transferred to register R1
9 and R20, respectively (step S13).

In step S14, it is determined whether or not the block is the final block. If NO, the process proceeds to step S15 and the contents of the registers R9 and R10 are transmitted to the NC unit 8 via the communication interface 7.

If YES at step S14,
The registers R13, R14, R17, R18 are set to 0 (step S16), and the delay amount and the mechanical error are added back to the machining program (step S17).
9, the content of R10 is N via the communication interface 7.
The data is transmitted to the C device 8 (step S18), and the process ends.

FIG. 9 shows the effect of the present invention. The locus D of the curved surface processing method of the present invention in which the mechanical error and the delay error due to acceleration are corrected is the loci E and F in which the above errors are not corrected.
Rather, it becomes much closer to the planned trajectory H of the machining program, and it can be seen that high precision machining is performed.

[0032]

As described above, since the present invention is configured as described above, high-speed and high-precision machining is performed by correcting mechanical errors due to acceleration / deceleration control delay, servo delay, and acceleration. Can be realized.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of a curved surface processing apparatus of the present invention.

FIG. 2 is a diagram showing an example of a machining program.

FIG. 3 is a diagram showing an example of an X-axis error table.

FIG. 4 is a diagram showing an example of a Y-axis error table.

FIG. 5 is an explanatory diagram of parameters.

FIG. 6 is a flowchart of steps S1 to S7 showing an embodiment of the curved surface processing method of the present invention.

FIG. 7 is likewise a flowchart of steps S8 to S12.

FIG. 8 is likewise a flowchart of steps S13 to S18.

FIG. 9 is a comparison diagram of a locus of a machining program and a locus of a command program according to the present invention.

FIG. 10 is an explanatory diagram of a conventional curved surface processing method.

FIG. 11 is a diagram for explaining an interval between adjacent line segments.

FIG. 12 is a diagram showing an example of reducing a radius in a conventional curved surface processing method.

[Explanation of symbols]

 1 Memory 2 Memory (Storage Means) 3 Machining Program 4 X-Axis Error Table 5 Y-Axis Error Table 6 Arithmetic Device 8 NC Device 10 X-Axis Servo Motor 11 Y-Axis Servo Motor 12 Z-Axis Servo Motor

Claims (4)

[Claims] 1. An NC machine tool for machining a curved surface by moving a spindle by a servo motor according to a machining program,
A curved surface machining method using an NC machine tool, which calculates a delay amount of acceleration / deceleration control from a feed rate of a spindle, corrects a machining program by the delay amount, and moves a spindle to perform curved surface machining. 2. An NC machine tool for machining a curved surface by moving a spindle by a servo motor according to a machining program,
A curved surface machining method using an NC machine tool, which calculates a servo delay amount from a spindle feed rate, corrects a machining program based on the delay amount, and moves the spindle to perform curved surface machining. 3. An NC machine tool for machining a curved surface by moving a spindle by a servo motor according to a machining program,
A curved surface machining method by an NC machine tool, characterized in that an acceleration of a spindle is calculated, a mechanical error due to the acceleration is obtained, a machining program is corrected by the error, and the spindle is moved to perform curved surface machining. 4. An NC machine tool for machining a curved surface by moving a spindle by a servo motor according to a machining program,
Parameters for calculating acceleration / deceleration control and servo delay amount, and storage means for storing an error table showing the relationship between spindle acceleration and mechanical error, and acceleration / deceleration control and servo NC for controlling the servo motor by calculating the delay amount, calculating the acceleration of the main axis, obtaining the mechanical error of the acceleration from the error table, and correcting the machining program with the delay amount and the mechanical error. A curved surface processing device, comprising: an arithmetic device for outputting to the device.