How to leave small gaps in cutting paths?

[TheMarkster]

I'm running grbl 1.1f on an arduino, so I have set the Processor to grbl in FreeCADs job settings. If that is the postprocessor you are referring to?

I inadvertently based my changes on some older code. I didn't think there would be any recent changes to the postprocessors. Here is a revised version based on the newest source:

grbl_post.py

(18.51 KiB) Downloaded 9 times

Let me know if it works for you or what, if any, changes need to be made. If it looks like it's working okay, I'll submit it as a pull request.

[leonardshelby]

Hey, thanks a lot for hacking that -noZ option. I'll try it. For my current 'workflow hack', to get holding tags for lasercutting, I have to use the Z changes as a source for "find and replace all" in a text editor.

I am placing the holding tags with some odd Z number, 90deg. Then I'll search and replace these lines with a way faster feed. This way, the laser quickly 'jumps' and creates the gap/holding tag. Then I will also "search/replace all" any Z movements by hand to fix the "drilldown" delay.

[TheMarkster]

Hey, thanks a lot for hacking that -noZ option. I'll try it. For my current 'workflow hack', to get holding tags for lasercutting, I have to use the Z changes as a source for "find and replace all" in a text editor.

I am placing the holding tags with some odd Z number, 90deg. Then I'll search and replace these lines with a way faster feed. This way, the laser quickly 'jumps' and creates the gap/holding tag. Then I will also "search/replace all" any Z movements by hand to fix the "drilldown" delay.

If it's not exactly what you need, attach a before and after gcode file, smaller and simpler the better so I can see exactly what changes you made. Might need to have a .txt extension for the board to accept the files.

[leonardshelby]

Thanks for your help!
Here's a simple 10mm square to be lasercut with holding tags on each edge.

square_freecad.txt is what i get out of freecad using grbl postprocessor.
square_laser.txt is how I would modify that file to make it work on a lasercutter.

The holding tags are too big in this case because I forgot to create a tool with a small diameter. But I think you'll get the idea?

Edit: A proper implementation would probably best be "laser" as a selectable tool. And then other options (speed/feedrate instead of height/angle/...) for the holding tags.

[TheMarkster]

Attach the .FCStd file, too. That way I could run the modified postprocessor on it and compare its output to your manually edited file.

[leonardshelby]

Sorry for answering so late, and thank you for your efforts! I am quite busy and have been trying to get this working :/ I have already deleted the .FCStd file. The problem should probably not be 'hacked' in a modified postprocessor anyway.. there are many settings and things that would still output bad gcode..just ditching Z in the files is not enough. E.g. there are still 'drilldown' movements that lead to the laser cutting a hole. FreeCAD would really need a laser option :/ I have been trying for days to get a working gcode file, but you'll get division by zero errors when trying to remove any Z-safe/tool/stepdown/.. heights, strange tool movements and orders with no way to change them and CAM simulation/visualization does not work for tiny diameters as lasercuts would be.

That said, the tags feature could/would be working for lasers as well. But it would need different settings (tool movement speed up in % + tag width would be enough).