Maximum radius for G2, G3 codes?
I have been printing the Planeprint "Notos" lately and I encountered some issues. This design must be sliced with Cura that seems to be a capable slicer but does bad job in optimizing the gcode files for Prusa I3. It needs many tweaks to the default settings to create good quality gcodes for my printer (I3 MK3).
The first issue I found was that Cura creates so large files with huge number of G1 lines that the more complex pieces in fuselage did not rint smoothly. The printer started "hesitating" during the curved sections and this resulted into very uneven surface since the LW PLA foams all the time and a small stop of the nozzle creates a ball of PLA.
I found that a Cura plugin called "ArcWelder" can reduce file size by using also G2 and G3 codes instead of just G1. The initial tests showed a drastic effect, one example shrinked from 20 MB to just 2.3 MB. So far so good. I tested this without adjusting defaults and the hesitation was gone. Unfortunaltely I found a new issue: Some of the straight (or almost straight) sections did not print correctly any longer. See the image.
I studied the ArcWelder defaults and inspected the gcode file and found the following:
- The default max radius is very large, 1000000.0 mm by default
- In the cgode file I found for example this line that corresponds to one of the failed sections:
G3 X118.683 Y75.091 I664677.688 J9323.032 E3982.30632
Especially the I coordinate here is very large and I think this must be the culprit. I then reduced the max radius to 10000.0 which is still quite large and got the following change in the cgodes:
G3 X118.398 Y95.132 I7227.325 J92.424 E3981.82301
G1 X118.683 Y75.091 E3982.30632
The problematic G3 line above was replaced with one G3 that has much smaller radius and a straight line (G1). I have not printed this one yet since I ran out of LW PLA. Now to my question:
How large G2/G3 radius is allowable for the Prusa I3 firmware that still prints correctly?
I suppose the 8-bit MCU will have rounding or precision related problems above a certain limit.
Picture of the problem
Here's the picture that refused to show in my first post.