Concave corner

[Alexanders]

I'm using a simple path for contour milling with compensation for tool wear.
KeepOffsetsMMFanucComp.set

Code: Select all

%
N100 (COMPENSATION-WEAR)
N102 (TOOL 1 - DIA 10.  mm)
N1 G90 G17 G40 G80 G00 
N103 M06 T1 ()
N105 G00 G54 G90 X15.145 Y221.578 S3183 M03 
N109 Z9. 
N110 G01 Z0. F668. 
N111 G41 D1 Y221.577 
N112 X246.474 
N113 X230.631 Y-5. 
N114 X-5.362 
N115 Z9.
N120 M30 
%

However, even with the smallest negative correction value, an error occurs: "Concave corner with cutter radius comp". The angle between the lines is 86 degrees.
Other CNC systems follow this trajectory with negative correction, without error messages.
I've tried adding small arcs to the corners, and it works. But it doesn't suit me. What can I change in the settings to prevent this message from appearing?

[TomKerekes]

Hi Alexanders,

That would be technically incorrect and is difficult to implement because one block of motion can't be determined until the following block of motion is known. Block 1's motion can't be determined before Block 2. Also if Block 1 or 2 consists of multiple small blocks the result is somewhat indeterminate.

gouge.png (5.49 KiB) Viewed 160 times

Your example of 86 degrees isn't really relevant is it? Any angle less than 180 degrees would cause gouging correct?

Which CNC systems support this?

Why doesn't adding arcs suit you?

One workaround might be to create the GCode slightly undersized such that all corrections would be positive. Would that work for you?

If you really need this to be added would you be willing to fully test it? There would be a number of special cases. Single stepping would execute delayed. A embedded MCode between compensated moves would either need to execute before the last motion or otherwise allow a gouge.

[Alexanders]

Your example of 86 degrees isn't really relevant is it? Any angle less than 180 degrees would cause gouging correct?

This is a real example from the machine's operation. Part of the above program that is not executed and causes an error.
This is contour milling of sheet material.

Test1.PNG (6.45 KiB) Viewed 109 times

One workaround might be to create the GCode slightly undersized such that all corrections would be positive. Would that work for you?

This is a bad path. Other program elements do not allow this.
The designer develops a G-code program using the CAM system. The CNC operator executes this program using only a cutter wear correction.

[TomKerekes]

This is a bad path. Other program elements do not allow this.

I don't understand what you mean.

But I think all the issues still exist.

Neg Offset.png (11.15 KiB) Viewed 103 times

Zoom.png (8.08 KiB) Viewed 103 times

Could you answer my questions?

[Alexanders]

I'm sorry for the long answer.

Why doesn't adding arcs suit you?

Because the product should have a sharp corner, without a radius. The products has a variety of geometries, and manually adding arcs is not advisable. This will increase the possibility of errors in the geometry. In addition, it will significantly increase the design time.

Which CNC systems support this?

Here are examples of running the same program in LinuxCNC:

Zero tool compensation:

Positive tool compensation:

Negative tool compensation:

No concave angle errors occur.


I'll also remind you of the question I asked earlier. These are additional cells for correcting the instrument's compensation. This is very convenient and reduces operator errors.

AddOffset.jpg (9.82 KiB) Viewed 76 times