JPH09120311A - Numerical controller and machining method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable smooth circular cutting. SOLUTION: A part program storage means 11 stores a part program including a circular cutting code 11a specifying the cutting operation mode of circular. A command value calculation table 12 contains a calculation expression for calculating a command value necessary when an additional block is generated. An additional block generating means 13 generates a block specifying the fast- feeding and positioning of a tool at a start point, a block specifying the approach path from a start point to a cutting start point by involute interpolation, a block specifying the circular cutting, a block specifying an escape path from a cutting end point by involute interpolation, and a block specifying the fast feeding and positioning to a return position.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a numerical control device, and more particularly to a numerical control device for performing arc cutting and a machining method.

[0002]

2. Description of the Related Art As a machining method for cutting the inside of an arc,
Generally, a method of approaching with an arc having a radius of a half of a circle to be cut and starting cutting is performed. 11 to 1
Reference numeral 5 shows the movement trajectory of the tool in this arc cutting method in order. However, the tool is shown with the tool diameter corrected.

FIG. 11 is a view of the initial state in which the tool is on the center of the cutting circle. The tool 1 is positioned on the center O of a cutting circle C3 which is a circle to be cut. The radius of the cutting circle C3 is r. Further, a point at which cutting is started or ended is defined as a cutting point P4.

FIG. 12 is a diagram in which the tool is moved to the starting point.
A point obtained by bisecting the line segment OP4 is defined as O1, and a circle centered at the point O1 and having a radius r / 2 is defined as C4. The intersections of a circle C4 and a straight line passing through the center O1 and orthogonal to the line segment OP4 are defined as P5 and P6, which are the start point and the end point, respectively. The tool 1 is fast-positioned on the path L3 by linear interpolation and moves to the starting point P5.

FIG. 13 is a diagram in which the tool is moved from the starting point to the cutting point. The tool 1 approaches the path on the circle C4 from the starting point P5 to the cutting point P4 by circular interpolation and reaches the cutting point P4 and then starts cutting on the cutting circle C3. Therefore, the cutting point P
4 is performed by such circular interpolation, the tangential velocity vector of the tool 1 and the moving direction vector at the cutting point P4 match.

FIG. 14 is a view showing that the tool is cutting on a cutting circle. The tool 1 starts from the cutting point P4 and goes to the cutting circle C3
After making one round of the upper part, the process returns to the cutting point P4 again to finish the cutting. FIG. 15 is a diagram in which the tool escapes from the cutting point to the end point. After the cutting is completed, the tool 1 escapes through the path on the circle C4 from the cutting point P4 to the end point P6 by circular interpolation. Therefore, the escape route from the cutting point P4 is performed by such circular interpolation,
The tangential velocity vector of the tool 1 and the moving direction vector at the cutting point P4 match.

As described above, the approach path to the cutting point and the escape path from the cutting point are interpolated with an arc having a radius of a half of a circle to be cut, so that the tool is moved at the cutting point. The tangential velocity vector and the moving direction vector match. As a result, it was possible to reduce the number of cutter marks formed on the work at the start and end of cutting.

[0008]

However, the tangential velocity vector of the tool moving on the circle C3 and the tangential velocity vector of the tool moving on the circle C4 are equal at the cutting point P4.
For this reason, since the radii of the circle C3 and the circle C4 are different, there is a difference in the normal direction acceleration at the cutting point P4. FIG. 16 is a diagram showing the respective normal direction accelerations of the circle C3 and the circle C4. The vertical axis is acceleration and the horizontal axis is time, and the tangential velocity is F
And Further, the time when the tool 1 is located at the starting point P5 is set to 0, and the time when the tool 1 is located when the tool 1 is located at the cutting point P4 by circular interpolation movement and approached is set to t.

At time 0 to t, the tool 1 moves from the starting point P5 to the cutting point P4 on a circle C4 having a radius r / 2. Therefore, the normal direction acceleration is F ² / (r / 2) = 2F ² / r. From time t, the tool 1 moves on the circle C3 having the radius r from the cutting point P4. Therefore, the normal direction acceleration is F ² /
r. Therefore, at time t, that is, the cutting point P4
As a result, there is a step difference in the acceleration in the normal direction as shown in the figure. Even when the tool 1 escapes from the cutting point P4 by circular interpolation movement, a similar step difference in normal direction acceleration is created.

In the case of high-speed cutting, this step becomes particularly noticeable, and the tool cannot follow the change in the acceleration in the normal direction at the cutting point, which deteriorates the processing accuracy in the part where the step in the normal direction is stepped. .

The present invention has been made in view of the above points, and an object of the present invention is to provide a numerical control device capable of performing smooth circular arc cutting.

[0012]

In order to solve the above-mentioned problems, the present invention provides a numerical controller for performing arc cutting,
A part program storing means for storing a part program including an arc cutting code which is an operation command for the arc cutting, and a part required for generating an additional block for performing an approach operation and an escape operation to the arc cutting by involute interpolation. A command value calculation table that stores a calculation formula for calculating a command value, and when the arc cutting code is commanded during execution of the part program, the additional block is generated based on the command value calculation table. There is provided a numerical control device having an additional block generation means.

Here, the part program storage means includes a part including an arc cutting code for designating an arc cutting operation mode.
Store the program. The command value calculation table stores a calculation formula for calculating the command value of the additional block. The additional block generation means is based on the command value calculation table,
A block that specifies rapid traverse positioning to the start point of the tool,
A block that specifies that the approach path from the start point to the cutting start point is performed by involute interpolation, a block that specifies circular arc cutting, a block that specifies that the escape route from the cutting end point is performed by involute interpolation, and a return position. And a block that specifies fast-forward positioning to.

[0014]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a principle diagram of the present invention.
The numerical control device includes a part program storage means 11 for storing a part program including an arc cutting code 11a, and a command value calculation table 12 for storing a calculation formula for calculating a command value necessary for generating an additional block. , An additional block generating means 13 for generating an additional block for performing involute interpolation or the like based on the command value calculation table, a preprocessing means 20 for performing a preprocessing, an interpolating means 30, and an axis control means 4.
1, 42, servo amplifiers 51 and 52, and servo motors 61 and 62.

The part program storage means 11 stores a part program including the arc cutting code 11a. The arc cutting code 11a is a G code and specifies the control operation mode as the arc cutting mode. This arc cutting code 1
The radius of the cutting circle which is a circle to be cut and the feed rate of the tool are set in 1a.

The command value calculation table 12 stores a calculation formula for calculating a command value required to generate an additional block. When the circular arc cutting code 11a is instructed during execution of the part program, the additional block generation means 13 determines the additional blocks required for a series of circular arc cutting operations by the command value calculation table 1
It is automatically generated based on 2. Specifically, the additional block generation means 13 specifies a block that specifies rapid-feed positioning to the start point of the tool, a block that specifies that the approach path from the start point to the cutting start point is performed by involute interpolation, and arc cutting. Block, a block that specifies that the escape route from the cutting end point is performed by involute interpolation, and a block that specifies fast-forward positioning to the return position.

The preprocessing means 20 is the additional block generation means 1
3. Decode the additional block generated in 3. The decoded result is output to the interpolation means 30 as an X-axis and Y-axis movement command. The interpolation means 30 interpolates the axis movement command to create an interpolation pulse, and the axis control means 41, 4 corresponding to each axis are provided.
2 is distributed and output. The interpolating means 30 can perform circular interpolation and involute interpolation. Axis control means 4
1, 42 are connected to the servo amplifiers 51, 52,
The servo motors 61 and 62 are driven.

FIG. 2 is a flow chart showing the processing procedure of the processing method according to the present invention. [S1] Perform rapid feed positioning to the start point. [S2] The approach path from the starting point to the cutting start point of the arc is performed by involute interpolation. [S3] The inside of the arc is cut from the cutting start point. [S4] The escape route from the cutting end point of the circular arc is performed by involute interpolation. [S5] Fast-forward positioning to the return position is performed.

Next, the movement locus of the tool in the machining method using involute interpolation according to the present invention will be described in detail. However, the tool is shown with the tool diameter corrected.
FIG. 3 is a diagram in which the tool has moved to the start point of involute interpolation. With the center O of the cutting circle C0 as the origin, the coordinates of the X axis and the Y axis are taken, and the basic circle C1 is set as shown in the figure. Basic circle C
The radius α of 1 is r / 2π, and the circumference of the basic circle C1 is equal to the radius r of the cutting circle C0. The tool 1 interpolates on the involute curve set by the basic circle C1 to approach the cutting circle C0. In addition, the start point P1 of the involute interpolation
Has an X coordinate of α and a Y coordinate of (3r / 4) + α. The tool 1 is fast-positioned on the path L1 by linear interpolation.

FIG. 4 is a diagram in which the tool is moved from the starting point to the cutting point. The tool 1 approaches the path from the starting point P1 to the cutting point P2 by involute interpolation, and after reaching the cutting point P2, starts cutting on the cutting circle C0. Here, the cutting point P2 is also the end point of the involute interpolation. In addition, a drawing in which the tool cuts on the cutting circle is omitted.

FIG. 5 is a diagram in which the tool escapes from the cutting point to the end point. The basic circle C2 is set as shown in the figure. The radius is α. The tool 1 interpolates on the involute curve set by the basic circle C2, and the tool 1 escapes from the cutting circle C0. Here, the cutting point P2 is the starting point of involute interpolation. Also, the X coordinate of the end point P3 of the involute interpolation is −
In α, the Y coordinate is − {(3r / 4) + α}.

FIG. 6 is a diagram of returning from the end point to the return position.
The tool 1 is positioned on the path L2 at a rapid feed by linear interpolation, and moves to the center O which is the return position. FIG. 7 is a diagram showing the acceleration in the normal direction of each of the cutting circle and the involute curve. The vertical axis is acceleration and the horizontal axis is time, and the tangential velocity is F. The time when the tool 1 is located at the starting point P1 is 0, and the time when the tool 1 is located when approaching the cutting point P2 by involute interpolation movement is t.

At time 0 to t, the tool 1 moves on the involute curve from the starting point P1 to the cutting point P2. Therefore, at time 0, the normal direction acceleration is F ² / L1. From time t, the tool 1 has a circle C0 having a radius r from the cutting point P2.
Move up. Therefore, the normal direction acceleration is F ² / r. Therefore, at the time t, that is, at the cutting point P2, the radius of curvature of the involute curve and the radius of the cutting circle C0 become equal, so that the change in the normal direction acceleration is continuous. Similarly, when the tool escapes from the cutting point P2 by involute interpolation movement, the acceleration in the normal direction is continuous. Therefore, even during high-speed cutting, a step does not occur in the acceleration in the normal direction, so that the tool can follow and the machining accuracy is not reduced.

Next, the additional blocks generated by the additional block generating means in correspondence with the tool path described above will be described with reference to FIGS. 8 and 9. FIG. 8 is a diagram showing an arc cutting code and additional blocks. Arc cutting code 11a "G12.3 I1" in the part program storage means 11
00. "F1000;" is a code for performing arc cutting using involute interpolation. "G12.3" is a G code for arc cutting using involute interpolation newly set in the present invention. Further, the radius r of the cutting circle C0 is 1
00, the feed rate of the tool 1 is set to 1000. When this circular arc cutting code 11a is instructed during the execution of the part program, the additional block 13a required for the circular arc cutting operation is automatically generated by the additional block means 13.

The command of the sequence number N01 "G91
"G00 X15.924 Y90.924;" is a positioning command, and is a block that specifies the rapid feed positioning to the start point of the tool. Starting point P1 (15.924, 90.
The tool 1 is rapidly positioned in 924). The coordinate value of the starting point P1 which is the command value is a value calculated based on the calculation formula X = α, Y = α + β of D01 of the command value calculation table 12 of FIG. Note that α = r / 2π, β = 0.7
It is 5r. Further, the coordinate value of the additional block after "G91" is an incremental value.

The command "G02.
2 X84.076 Y-90.924 I-15.9
24 J-75. R15.924 F1000. ; "
Is an involute interpolation command for the approach path, and is a block that specifies that the approach path from the start point to the cutting start point is performed by the involute interpolation. “G02.2” represents clockwise involute interpolation, and “X84.076”
"Y-90.924" is an incremental coordinate value at the end point of the involute interpolation and is the cutting point P2. Also,
"I-15.924 J-75. R15.924 F
1000. "," I and J represent the center positions of the basic circle C1 of the involute curve viewed from the starting point P1. R is the radius of the basic circle C1, and F is the feed rate on the involute curve. These command values are calculated using the calculation formula X = r−α, Y = − (α + β) of D02 in the command value calculation table 12 of FIG.
It is a value calculated based on I = -α, J = -β, and R = α.

The command "G02" of the sequence number N03
I-100. ; Is a clockwise circular interpolation command,
This block specifies arc cutting. One round of a cutting circle C0 having a radius R = 100 is cut. This command value is also based on I = -r of D03 in the command value calculation table 12 of FIG.

The command "G02.
2 X-84.076 Y-90.924 I-10
0. "J-15.924 R15.924" is an involute interpolation command for the escape route, and is a block that specifies that the escape route from the cutting end point should be performed by involute interpolation. "X-84.076 Y-90.92
4 ”is the incremental coordinate value of the end point of the involute interpolation, which is the end point P3. In addition, "I-100.
"J-15.924 R15.924", I and J represent the center position of the basic circle C2 of the involute curve seen from the cutting point P2. R is the radius of the basic circle C2, and F is the feed rate on the involute curve. These command values are shown in Fig. 9.
Formula for D04 in the command value calculation table 12 of X =-(r
-Α), Y =-(α + β), I = -r, J = -α, R =
It is a value calculated based on α.

The command "G00" of the sequence number N05
"X-15.924 Y90.924;" is a positioning command, and is a block for designating fast-forward positioning to the return position. These command values are values calculated based on the calculation formulas X = -α and Y = α + β of D05 in the command value calculation table 12 of FIG.

FIG. 10 is a diagram showing a schematic configuration of hardware to which the present invention is applied. The processor 71 controls the basic functions of the numerical controller. Read-only storage device (R
The OM) 72 stores a system control program. The random access memory (RAM) 73 stores temporary data such as input / output signals. The non-volatile memory 74 stores various data such as a part program including an arc cutting code to be retained even after the power is turned off. A graphic control circuit 81 and a display device 8 are provided in the panel 80.
2, a keyboard 83 and a software key 84 are provided. The graphic control circuit 81 is the processor 71.
The image information sent from is converted into a displayable signal and output to the display device 82. As the display device 82, a CRT, a liquid crystal display or the like is used. The keyboard 83 includes operation keys and function keys used for data input. The meaning of the software key 84 changes according to the operator's screen selection, and the necessary keys are displayed on that screen. The axis control circuit 40 receives a command such as an interpolation pulse from the processor 71 and outputs a command to move the axis to the servo amplifier 50. The servo amplifier 50 receives the movement command and drives the servo motor in the machine tool 90. The programmable machine controller (PMC) 75 is a sequence program formed in a ladder format and is a machine tool 9
Control 0. Note that these components are connected to each other by a bus 76.

[0031]

As described above, in the present invention, the approach path to the cutting start point of the arc and the escape path from the cutting end point are determined by involute interpolation. This allows
Since there is no step difference in acceleration near the cutting start point and the cutting end point, the machining accuracy can be improved.

[Brief description of the drawings]

FIG. 1 is a block diagram showing the principle of the present invention.

FIG. 2 is a flowchart showing a processing procedure of a processing method according to the present invention.

FIG. 3 is a diagram in which a tool is moved to a start point of involute interpolation.

FIG. 4 is a diagram in which a tool is moved from a starting point to a cutting point.

FIG. 5 is a diagram in which a tool escapes from a cutting point to an end point.

FIG. 6 is a diagram in which the tool returns from the end point to the return position.

FIG. 7 is a diagram showing respective normal direction accelerations of a cutting circle and an involute curve.

FIG. 8 is a diagram showing an arc cutting code and an additional block.

FIG. 9 is a diagram showing a command value calculation table.

FIG. 10 is a diagram showing a hardware configuration to which the present invention is applied.

FIG. 11 is a view of the initial state in which the tool is on the center of the cutting circle.

FIG. 12 is a diagram in which a tool has moved to a start point.

FIG. 13 is a diagram in which a tool is moved from a starting point to a cutting point.

FIG. 14 is a view showing that the tool is cutting on a cutting circle.

FIG. 15 is a diagram in which a tool escapes from a cutting point to an end point.

FIG. 16 is a diagram showing respective normal direction accelerations of a cutting circle having a radius r and a circle having a radius r / 2.

[Explanation of symbols]

 11 Part Program Storage Means 11a Arc Cutting Code 12 Command Value Calculation Table 13 Additional Block Generation Means 20 Preprocessing Means 30 Interpolation Means 41, 42 Axis Control Means 51, 52 Servo Amplifiers 61, 62 Servo Motors

Claims (3)

[Claims] 1. A numerical control device for performing arc cutting, a part program storing means for storing a part program including an arc cutting code which is an operation command for the arc cutting, and an approach operation for the arc cutting. A command value calculation table that stores a calculation formula for calculating a command value required to generate an additional block that performs escape operation by involute interpolation, and when the arc cutting code is commanded during execution of the part program, An additional block generation unit that generates the additional block based on the command value calculation table, and a numerical control device. 2. The additional block generation means specifies a block for rapid-feed positioning to a starting point of a tool, a block for specifying an approach path from the starting point to a cutting start point by the involute interpolation, and the arc. 2. A block that specifies cutting, a block that specifies that an escape route from a cutting end point is to be performed by the involute interpolation, and a block that specifies rapid feed positioning to a return position are generated. Numerical control device. 3. A machining method for performing arc cutting, wherein the approach path of the arc to the cutting start point is performed by involute interpolation, the inside of the arc is cut from the cutting start point, and the cutting end point of the arc is cut. A processing method, wherein the escape route is performed by the involute interpolation.