Homing Sequence Messes with X and Y Zero

Hello!

I have been noticing this issue since the first day I got the Shapeoko. Every time when it rehomes, it’s X and Y are slightly off. Doing normal operations are fine but when something does go wrong to the point that I need to stop the program or if the USB disconnects, the Zero on the X and Y becomes slightly off when it rehomes, and it’s very difficult to get the X and Y back to where it was before the homing sequence.

I was wondering if:

  1. Anyone else is having this issue and what their solution is?
  2. If there is any way to disable the homing sequence when the program is stopped?

Thank you!

How far off is it ?

We have had quite a few threads on this, and the conclusion tends to be that when the mechanical tuning of the machine is ok, both the mechanical limit switches and the proximity switches provide quite a good repeatability/precision.

Can you try “poor man’s homing” method and see if it improves things ?

I don’t think CM behavior of homing after the program is stopped is configurable.

3 Likes

Thank you for your reply! Its quite off. The contours or if we were to do a finishing pass are very obviously off even when just looking at it after a homing sequence. We are using induction switches.

For projects where repeatability is necessary I’ve found that dragging the gantry all the way forward and the carriage all the way left as described in @Julien’s link makes positioning more reliable. https://launch.carbide3d.com/elements/category/U_S__State_Flags

It is possible to slightly adjust the homing switches to adjust where the working area falls relative to the machine — just did that on my SO3 to get the working area nicely centered.

i would also suggest to check the belts for tightness/slippage plus the grub screws on the motor axle

1 Like

I’ve realized that even without homing it messes up the second time I run the program. I did a simple contour that is suppose to be 0.25 by 1.5 inches. The first time it made the contour it was good. I only cut halfway into the material so I can keep running it again. I ran it again and now its around 0.245 by 1.45 in. I ran it a third time and it didn’t change it again. Now I rehome the machine and after running it, the part comes out to 0.24 by 1.4 in. It made it smaller the second time even without rehoming and the forth time where it was rehomed really messed it up.

You’re not anywhere near the edges of the machine are you?

No, I did it in the middle. I don’t think its belt tightness because its able to make the part accurately just not when I run it again.

Well it’s not missing steps by hitting the end of travel then.

Still seems to be missing steps somewhere, have you tried the “draw a line across the pulley and end of motor spindle” trick to make sure they’re not slipping as the machine drives?

3 Likes

How do I do this?

Thanks again

We are using the HDZ not the belt driver Z axis and its only the X and Y I am having issues with.

1 Like

Draw the line across the pulley and motor shaft.

3 Likes

So, the suspicion is that the machine is losing movement somewhere because your different size cuts indicate it’s not just the zero point moving but the scale of the toolpath changing too.

As Neil says, on the end of the belt pulleys you should be able to see the end of the motor shaft too, if you take a fine point marker and draw a line that goes across the flat end of the pulley and the end of the shaft that shows the relative alignment of the shaft and pulley. After the machine has misbehaved, check them again and if any of them don’t line up any more you’ve found your slip.

4 Likes