X Axis random moving during cut

Over the last month or so, the X-axis will randomly decide to jog a little during one of the cuts, putting the whole cut out of position and destroying my part.

Here are some pictures:

Has anyone else seen problems like this?
I’ve run that gcode file a few times before so I can rule that out, but could it be something with the controller or UGS?
Any help would be good… I’m sick of chewing up good cedar.

You’re looking steps somehow, which means the motors aren’t controlling the motion as they should be. They’re either slipping and not movingenough or are being overwhelmed by your cut and moving too much.

Are your belts tight? Does your machine move unrestricted when not powered? Do you have your potentiometers properly calibrated?

What was your feed rate and depth of cut?

Make sure your stepper wires are securely connected at the controller and the terminal block.
Inspect your belts for wear (usually manifested as visible stretching and/or irregular belt teeth)

If everything looks ok with the connections and belt health:
Make sure your belts are tight.
Make sure your pulley is not slipping and grub screws are secure

If the belts are tight and the pulley is secured:
Make sure you’re getting enough, but not too much voltage to your stepper

If all of the above is ok - try slowing down your feed rate. You might just be overloading the single stepper.

If none of the above - yikes

The depth of cut is only 0.08" @ 125in/min with a 4-flute 1/4" bit. The router did about 3 passes before it decided to start taking a random path. My first thought was that it’s just too much of the motors and it didn’t follow the path, but this particular piece is square so the X-axis and Y-axis should be operating independently in this case.The motion was clockwise so it looks as if the bit decided to start moving early.

Belts are tight and the movement is unrestricted.

Possibly the bit is dull and grabbing, pulling the axis out of alignment. More than likely, its a combination of the two.
Try using a new bit, or even try disabling the idle step down (dip switch 4 on the controller for each axis).
This would increase the holding power of the stepper, instead of it going to 30% power at idle.

Belts are tight and the screws look good… I’m going to try reducing the feed rate and see if it comes back.

The real oddity is this is being cut in a clockwise pattern. If the stepper was overloaded, it should be coming up short on the cuts or chattering like crazy as it loses control. It seemed have no problem plowing a 0.25" furrow through the cedar at a weird jagged angle.

Good idea, I’ll change out the bit when I get home.

Is there any downside to disabling idle step down, like increasing heat or anything?

I’m willing to bet the current reduction is your problem. Yes it will increase heat slightly, but it’s set up to handle it. Flip that switch, dial in your motor current and you should be good to go.


As long as your steppers dont go past 176degF (continuous) they are fine.
Reduced Idle Current prevent the idle motors to reach max holding torque which may be needed to keep them in check.

The drivers may give a noticeable, continuous “hiss” with Idle Current @ OFF on occation, this is nothing to worry.
(rotor oscillate back and forth due to the switching current)

Is there a way to adjust current on the X-controller?
That might be the problem right there…

Dip Switch #4 IIRC

I don’t have one but apparently there are potentiometers for each axis. Someone with an x controller will need to confirm.

The dipswitch mentioned should enable/disable cutting current at idle

I adjusted all the currents up a bit, disabled idle step down, threw on a new bit, and turned the feed rate down a smidge.
Let’s see how this next batch of pieces fair, but I am hopeful :slight_smile:

You need to be somewhat careful when increasing current as too much current can cause your drivers to go into thermal overload. They will shut down momentarily to prevent damage, but this will result in similar lost steps. If you are operating close to the limits of your machine, there is a fine line between not enough current and too much causing overheating. In a machine that isnt pushed to the absolute limit, this margin between too little and too much as wider and a bit more forgiving. Just start to watch for similar missed steps and be familiar with the idea of thermal overload.

Here is a snippet from Inventables assembly instructions.