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 28 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).