When milling the outer circle, the size is too small. How to modify the shape of the tool offset (D)? Should I fill in a positive value?
Two points:
1. G41/G42 selection
2. G41/G42 compensation principle
I. G41/G42 selection
Selection basis:
Looking along the tool movement direction, if the tool radius is compensated to the left, it is G41, and if it is compensated to the right, it is G42
Example 1:
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G41 is specified in the program
The operator enters the tool radius value (positive value) in the machine tool radius compensation interface
Looking along the tool movement direction, the tool will compensate to the left.
Example 2:
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G42 is specified in the program
The operator enters the tool radius value (positive value) in the machine tool radius compensation interface
Looking along the tool movement direction, the tool will compensate to the right.
2. Compensation principle of G41/G42
I divide compensation into three stages:
1. Start compensation
2. Compensation status
3. Cancel compensation
Example:
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1. Start compensation stage:
Let's look at the above program:
N1 program segment: compensation has not started yet, that is, the tool center is at X=0, Y=0 (not the tool edge)
N2 program segment: G0G41X20.Y10.D1 Start compensation
Please note: X=20.Y=10. is the coordinate point of the tool edge (not the coordinate point of the tool center), and compensation has started;
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Because, from X=0,Y=0 to X=20.Y=10., the tool will gradually move to the left. (Because G41 is specified in the above program)
How much does it move?
The offset (positive value) is determined by the corresponding tool radius value entered by the operator in the machine tool radius compensation interface.
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For example, for a D10 milling cutter,
if you enter the corresponding tool radius value of 5 in the radius compensation interface, it will move 5mm to the left.
If you enter 4, it will move 4mm;
If you enter 0, it will move 0mm (the tool center is at X20, Y10 at this time, which means there is no compensation);
If you enter -5, it will move -5mm to the left, in other words, it will move 5mm to the right;
Okay, the above analysis of the process of establishing radius compensation is 1. The tool radius compensation command must be specified in the program, and 2. The operator enters the compensation value in the machine tool radius compensation interface.
After analyzing this, please pay attention to the sentence in my previous text:
From X=0, Y=0 to X=20.Y=10. The tool will gradually move to the left.
The two coordinate points from X=0, Y=0 to X=20.Y=10 are very important.
That is, the X, Y values in the program segment before establishing radius compensation are the same as the X, Y values in establishing radius compensation.
At least one of the vertical distances between these two points must be greater than the compensation in tool compensation.
Note: Compensation is required in G00 or G01 state at the beginning of compensation (compensation cannot be performed under G02 or G03 instructions, otherwise the machine tool will alarm);
2. Compensation stage
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In the compensation stage, the machine tool system will pre-read the following two program segments (i.e. N3 and N4 program segments) to determine the direction of the compensation vector.
Therefore, it is recommended that the two program segments after G41 or G42 compensation should not both have Z values.
Take the following example:
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When radius compensation is established from segment N3, the CNC system can only pre-read the next two program segments,
and both segments N4 and N5 are Z-axis movement (the system cannot determine the vector direction of the next compensation,
After the N3 segment is executed, the tool trajectory changes. It is no longer the original P point, but P1 point (tool center point), and then moves to the intersection of P2 (gradual compensation), so overcutting occurs as shown in the figure above.
How to modify?
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Before compensation, set non-interference auxiliary points, Z axis down once, and three axes down at the same time
3. Cancel compensation
The command to cancel tool radius compensation is G40, It must also be in G00 or G01 state and cannot be canceled under G02 or G03 instructions.
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Canceling radius compensation starts from the N7 program segment, (N7G40G00X0Y0)
Starting from the end point of the N6 program segment, to the X=0, Y=0 in the N7 program segment as the end point, the tool center returns to the (X=0, Y=0) point.
