Outline feature bug when using surfacing feature with soft limits enabled

Hello All,

Just setting up my 30 x 30 Mk 2 for first use and I’m running into a strange problem. It involves the outline feature which I have to first point out is not documented very well, if at all, anywhere online that I can find.

I’ve elected to go with limit switches on my system because I’ve worked in industry a lot and have seen the benefit of having them. So I have those installed, homing, hard limits and soft limits are all enabled in the settings.

So I got my system assembled, squared, screwed down, and homed. It will move to the 4 corner points just fine with no issues.

So I then selected the surfacing feature, and selected a 30 x 30 inch area starting in the home position (forward and left) and selected the spiral pattern.

When I load that in and then select outline, I’m getting a very strange result.

The XY axis will start moving diagonally across the work area, just as indicated on the screen representation. However when the Y axis gets just about 25% of its total distance, one Y axis stops while the other tries to keep going, and it makes a terrible noise. At which point I e-stop it. After reset, my Y axis position is completely off, and it need to a re-home it in order to recover. The X and Z axis are fine ,its just the Y axis coordinates that are messed up.

After homing again, I can again move to all 4 corners without any issue. But if I try to use the outline feature again, the same thing happens repeatedly.

Also, if I try to use the Test Run feature, I get a soft limits error which won’t allow it to run. However, the soft limits are all set correctly for a 30" W X and 32" D Y area. So I’m not sure why the soft limits are flagging, there should be no issue on the Z axis…

However, when I turn off soft limits then the problem with the outline feature is gone. So the problem is definitely a result of the soft limits being enabled, but why they would be having this strange effect is beyond me. The soft limits appears to be stopping just one of the two Y axis drives which is then throwing off the Y coordinates as it is actually stalled out while this is happening and it apparently thinks it’s still moving.

I did not have time to check to see if turning off soft limits allowed the test run to work without the soft limit alarms.

Anyone else seeing this problem? Or know what’s going on here?

Any help would be appreciated.

Hi Corey,

The outline feature generates gcode of the outer perimeter of your loaded file and runs it to verify that you won’t hit any clamps or other fasteners while cutting. It’s 100% optional and for peace of mind.

As to the main issue, I would somewhat lean towards this being an issue with machine setup being slightly off. Outline sends a string of generally short G0 commands, which should never cause one stepper motor to work while the other doesn’t since the GRBL firmware doesn’t work that way.

One thing you could try is simulating the issue with long continuous jog in a diagonal direction with soft limits disabled - from the home position to the opposite corner, see if you see the same issue with the Y axis skewing or one.

After that, with soft limits now enabled, try to move from one corner to the opposite diagonally - the rapid movement buttons from home position in bottom left to top right would be an easy option. You can then to the same movement diagonally from top left to bottom right.

What we’re looking for is a similar behaviour. There are a number of physical issues that could motors to not be in sync, including loss of power to one stepper motor, something mechanical slipping, or a misconfigured/faulty stepper driver. We’re trying to find a way to replicate the issue outside of the software itself.

Anyways, let us know the results,

Ok Kevin, thanks. I’ll give that a try tonight and report back the results. I’ll try to get some video if possible as well.


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There will be a slight delay getting to this while I get the new Y rail installed…


OK Kevin, I had the Covid so I’ve been out of commission for a few weeks here… I’ve made it through that now.

Anyway I just had the chance to get back on the system last night, and I have to withdraw this bug report.

At first it seemed to be related to the soft limits being enabled but it appears that was simply a coincidence. While it held true repeatedly, eventually the problem started showing itself even with the soft limits disabled. It was more related to how fast the axis was traveling.

First I checked the current settings and micro-step switch settings. Those were correct.

What I think the problem was, although I can’t confirm it, is that the lead screw nuts were binding intermittently on one axis. This caused some kind of a harmonic vibration to occur at higher speeds, and that caused that side to stop. Since the other axis continued that caused a binding which exasperated the problem further.

So I loosened and then re-tightened the screw nut mounting bolts until they were just snug. Then I moved the Y axis back a fourth across it’s full range and tightened the mounting bolts. And then I preloaded the anti-backlash screws until they were just lightly making light contact.

Since doing that the system has been working better, and the outline feature is working properly.

Thanks for the help, I’m sorry I lead you down a rabbit hole.


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@Ranchdude I’m glad that you are back in the saddle, so to speak, Corey. I hope that there are no lingering effects of Covid.

Since it looks like you have found the source of your original problem and addressed it, I’ll close the thread.