Shapeoko XXL hitting the top of the Z

[cctdad]

I’m frustrated, working through a number of issues that have all of a sudden appeared. On this one, when I start a job my Z (belted) goes flying up and hits the stop, beats on it for a few seconds, and then comes down and commences cutting like nothing happened. This happens in CM (updated today) and UGS, and with files from both CC and VCarve. I’ve been trying to work through some other issues (issues that snapped an end mill and for which I blame the VCarve post processor…), so today I’ve been doing this without an end mill and with the router off. I can’t imagine that this has been going on for the last 18 months and I’ve just never heard it because the router was on. Thoughts? This video shows one where it just kisses the top, but at other times it goes at it for a full two or three seconds. Here’s the Z hitting the top.

[Julien]

Hi @cctdad,

Sorry to hear you are struggling with this. I think you are “just” running out of Z travel due to a combination of your setup and retract height settings: from that video is seems like you have a T-track wasteboard on top of the base board (as it should), then a supplementary wasteboard on top of that, and then your stock, this adds up to a lot of thickness, not leaving much Z travel from the top of the axis. We can see in the video that upon starting the Z axis is very close to the top already. What probably happens is that in your CC or VCarve projects, you set a retract height value that is larger than that small available Z travel you happen to have, which causes this crash at the top of the Z when starting (and then causes wrong depth of cut)

Your main options to solve this are a combination of

• removing one layer of wasteboard
• reducing your retract height in CC/VCarve to the minimum value compatible with your workholding. In that video I don’t see any clamps, so assuming you have free access to the whole top surface of your stock, you could set your retract height to just a few mm / 0.1".