Z-Axis loses zero


After the construction, I am using Winston’s GC to cut out holes for T-Nuts - you will notice that on the second hole, the machine starts to lose the Z-Axis orientation.At 00:24s you will hear sound as if cutter is hitting something, but the cutter does not cut through the MDF and hit the plates below. This causes it lose the orientation. Any thoughts?

I am using Shapeoko 3 XL.

@funnyenough - keybase.io/funnyenough

Go Green. Please do not print unless absolutely necessary.


Power on your machine, and push on the x and z axis. Does the z move, yet the x does not?

FYI : all the steppers lock when powered on, so they should all have equal holding power.

The steppers locking is governed by a Grbl setting:

$1=255 (step idle delay, msec)

Make certain that it’s set to 255, which means that they hold continuously when not moving.

I was having the same issue. Seems that the tension on the Z axis drive belt was too loose. Once I corrected that problem, I haven’t had any more issues. Just a thought.

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I had the same thing happen, it was the belt tension. Easy way to tell is if you take the bit out (leave the router powered off) and use the jog command on the Z axis, it will ‘pop’ up after the spring tension overcomes the belt tension if it is too loose.

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Yes, it is set to 255.

Thanks for the quick response. I was away. But now I am back, and I able to do as suggested. The all the axis are locked including Z-Axis when the power is on.

Video: https://youtu.be/rTIpl9aXFSM

Not sure if it is related but it seems like it is - the Z-Axis position gets messed up when the bit hits the board.

Video: https://youtu.be/vexuHXJaOqo

When the belt skips (what happens when the Z-Axis hits the board) then that Z axis value will no longer be accurate. It’s open-loop control, the controller only knows that it told the stepper to move the axis, so it now believes the axis has moved. It does not know that it did not move.

It does sound like that is what is happening in you first video; could upload the gcode used? It could be that one hole is set to cut deeper and the bit hits the metal strap.

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How does one tighten the belt without fear of bending motor shaft?

GCode (by @wmoy) attached. wasteboard-tnuts.nc (83.8 KB)


From the video this is what i see: the Stepper motor has no where to go, so its slipping.
The position is changing in Carbide Motion because its counting the pulses.

I don’t know if you do need to tighten the belt.
Are you at the bottom of the travel?

If your trying to machine holes into the wasteboard, turn the router on. Even with the tightest belt, if you plunge into a surface with the router off, its going to skip at the Stepper motor.

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makes sense - in essence the cutter needs to cut faster than the plunge rate to avoid this behavior.

does that mean my Router is not cutting fast enough, i.e. the cutter RPM?

For my Makita Router the dial is set between 2-3 on the router.

It could be the RPM is too low, but more likely your at the bottom of the Z travel.

You may need to add another sheet of material to lift your work piece in order for the tool to reach.

How long is that tool? It appears to be sticking out of the collet. Do you have at least 3/4" of the tool inserted into the collet?

Maybe you are right that I am at the end of the Z travel. I can verify it tomorrow when i go back to the studio.

As this project was built with an assumption that the router is DeWalt. @wmoy did post something the other day about Makita routers being short on Z travel by as much as 1/2".

how big is that hole and what size bit is that? tight holes that go real deep can be tricky. are you using carbide create?


Alright, so raised the base by an inch so that the Z travel never passes the midpoint. I also verified that the cutter is in the collet at 3/4". Still the same issue - within few passes Z-axis had lost 5-6mm.

Any other thoughts?

any thoughts on the GC i uploaded?

Hole is 8mm. Cutter is the stock 1/4" Carbide #1. @fiero1 I have attached the GC in my previous response.

your z belt is loose. tighten it up, I’m not sure if you have the adjuster screw but my z belt is TIGHT. Your motor should not be slipping that easy against the waste board. G/lRay

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Silly question, but have you checked the set screws on the pulley. That was giving me some trouble.

When I first set it up, I didn’t use the threadlock (because I found myself taking things apart and re-assembling). Those set screws loosen easily without the threadlock and can slip just enough to mess you up.