Questions on cut quality

[dovrosenberg]

I built a CNC machine using jd garage plans. I have a primeweld cut60 with the original 1.1 mm 60 amp tip. I think I finally got the cut speed and cut height figured out to minimize dross. Now I’m trying to figure out why the shape is off a bit. I assume a calibration of sorts may be needed. The material is 1/8” steel plate.

Thoughts are appreciated

Front side of cut

Back side of cut

Trying to understand why the shape is off on the top part

[weldguy]

Could be a number of things. Could be one of your axis binding up at a tight spot, you can turn the power off and move each axis by hand slowly to feel for any tight spots. Could be that you are accelerating too quickly on rapid moves and loosing steps, you can reduce your rapid speed to match your cut speed to start with and see if that helps. Check those things out and post back.

[bLouChipBlacksmith]

@weldguy, agreed.
I was helping another fella having just built a jdgarage table and with similar cut distortion; it seems the default grbl config values that the build instructions use are very high for the mechanical design of the table. There appears to be a lot of mechanical resonance in the gantry, especially in the original cantilever design. I had the fella dial down grbl config for XY acceleration and his cuts improved tremendously.
Specifically $120=350 and $121=350, that is X and Y acceleration in mm/sec2 .
$110=8000 and $111=8000 to limit XY rapid speed to 8000mm/min.

[weldguy]

Great info bLouChipBlacksmith, hopefully the OP see's this and it works for him.