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[Solved] G2 and G3 arcs in Prusa  

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Michael Lew
(@michael-lew)
Trusted Member
G2 and G3 arcs in Prusa

Can a Prusa MK4 print a gcode file that includes G2 and G3 arcs? Are there limitations on the implementation of the arcs? Can G2 and G3 be used in a vase print where the end Z value is different from the initial?

I have consulted the RepRap page about Gcode commands ( https://reprap.org/wiki/G-code) and there is an annotation of the Prusa Marlin implementation of arcs that I don't really understand: "Prusa Firmware implements arcs only in Cartesian XY."

I can't seem to get PrusaSlicer gcode previewer to display G2 and G3 arcs. When I load a gcode file written with custom non-slicer software I can see the lines that are G1 but none of the lines that are G2 or G3. A buddy was unable to get my gcode to print on his Prusa Mini and it is making me concerned that the MK4 that I have ordered will not print my code.

Posted : 07/06/2023 11:44 pm
jseyfert3
(@jseyfert3)
Reputable Member
RE: G2 and G3 arcs in Prusa

This post appears to imply the printers support G2 and G3 codes, but PrusaSlicer only supports G1 codes. If that's the case, it's not surprising the gcode viewer won't display code with G2 and G3.

For the code tested on the MINI (which I also have), was the issue it didn't print properly, or the printer refused to print it at all?

Posted : 09/06/2023 3:42 pm
Walter Layher
(@walter-layher)
Prominent Member
RE: G2 and G3 arcs in Prusa

I have printed gcode files processed with the OctoPrint plugin Arc-Welder on my MK4. The gcode files do contain G2 and G3 codes. The printer prints them without problem, even if they are created with IS profiles. I send them from PrusaSlicer to OctoPrint and let them process by the plugin. Then I download them to the USB stick and print them from there via the display control on the printer. Printing files with input shaping via OctoPrint can lead to problems, like printer crashes with red screens and such. Printing them from the USB stick has been successful for me so far.

Posted : 09/06/2023 4:33 pm
Michael Lew
(@michael-lew)
Trusted Member
Topic starter answered:
RE: G2 and G3 arcs in Prusa

Jseyfert3: Thanks for your response. The report that I got from the person who tried to print my file was that the printer "raced through the % completion" but did not move.

I'm not certain that I can interpret that as the printer being unable to deal with arc commands because I have not yet worked out what the gcode file needs to contain in order to make the printer happy. I usually send 'naked' gcode to my Voron which is running RepRap firmware, but the Prusa firmware might want more (or different) information in the file than I supplied.

Since posting I have found that the latest 3.12 firmware release included bug fixes for the G2 and G3 arc routines and so it seems pretty likely that I should be able to get my files to print somehow or other. It is possible that the Mini that tested for me is running older firmware.

Yes, I suspect that the Prusa Slicer preview app does nto support arcs. That's a shame.

Posted : 09/06/2023 9:24 pm
Michael Lew
(@michael-lew)
Trusted Member
Topic starter answered:
RE: G2 and G3 arcs in Prusa

Thanks Walter. I'm now quite confident that my new K4 will be able to print arcs once it arrives. I'm not so sure that the Prusa Slicer preview app will show the arcs though.

Posted : 09/06/2023 9:26 pm
Walter Layher
(@walter-layher)
Prominent Member
RE: G2 and G3 arcs in Prusa

I just tested the gcode viewer of PrusaSlicer 2.6.0-beta4 with a gcode file that was created in the way I described in my last post above (it contains G2 and G3 codes). It shows the part just like it appears in PrusaSlicer in the slicing preview before the export of the original gcode file. This did not work with the gcode viewer of PrusaSlicer 2.5.2, that one did not show the part correctly but showed some straight lines where there should be arcs.

Posted : 09/06/2023 9:36 pm
Michael Lew
(@michael-lew)
Trusted Member
Topic starter answered:
RE: G2 and G3 arcs in Prusa

That's good news Walter. I'll download the 2.6 beta and play with it later today. It is looking like the Prusa software is catching up to my needs just before I get the printer. Excellent planning by someone.

Posted : 09/06/2023 9:38 pm
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