How to adjust Jerk settings in GRBL (NEJE Max 4; Sculpfun S30)

[colorfulcabbage (Robin)]

Hi all,

I’m trying to fine tune the speed and smoothness of my machines: a NEJE Max 4 (E80) and Sculpfun S9 with an S30 Board.

I’ve worked out the max speeds of travel and acceleration for the axes, but I can’t seem to find where I could adjust the jerk (similar to a 3D printer)

I’ve tried searching for existing topics but couldn’t find something that answered this. I saw some users having jerk settings available but on a Trocen.

Does anyone how to tweak this setting on GRBL boards?

Thanks.

[berainlb (PY)]

I don’t believe jerk is an available configuration on GRBL boards.

You can accomplish similar things with Junction deviation ($11).

$11 - Junction deviation, mm

Junction deviation is used by the acceleration manager to determine how fast it can move through line segment junctions of a G-code program path. For example, if the G-code path has a sharp 10 degree turn coming up and the machine is moving at full speed, this setting helps determine how much the machine needs to slow down to safely go through the corner without losing steps.

How we calculate it is a bit complicated, but, in general, higher values gives faster motion through corners, while increasing the risk of losing steps and positioning. Lower values makes the acceleration manager more careful and will lead to careful and slower cornering. So if you run into problems where your machine tries to take a corner too fast, decrease this value to make it slow down when entering corners. If you want your machine to move faster through junctions, increase this value to speed it up. For curious people, hit this link to read about Grbl’s cornering algorithm, which accounts for both velocity and junction angle with a very simple, efficient, and robust method.

[colorfulcabbage (Robin)]

I see, with this the end of the scans are essentially really sharp corners then?

Thank you for the feedback. Will fiddle around with this.

[berainlb (PY)]

@colorfulcabbage

with this the end of the scans are essentially really sharp corners then?

If you’re optimizing for horizontal scanning I don’t believe Junction deviation will have a direct affect. That’s more for turning around corners of connected line segments. Not sure but I don’t think this would come into play on disconnected horizontal scan lines. Worth experimenting with in either case.