Z axis starts too low

On this project the Z axis goes to max before it starts down. Then it starts too low (about 0.3" into the wood). I have tried to reset the z zero but with same results. I have checked the belt and other hardware on the z axis. I moved the origin from bottom left to center since the pocket I need is in the center of the project. The same thing happens.

Hi @keith,

to figure it out together, could you please:

  • post your design file
  • post the associated generated G-code file that you ran
  • describe in details how you set the zero, and what’s the setup of your machine (do you have a BitSetter or not, etc)

I just read your post from Feb. about the z crashing the limit and then going lower on thicker material. I think this is whats happening. The project is 1.4" thick.

I sent the gcode to William last night. Let me find the gcode again.

The project is in vcarve pro. Don’t know how to share that. Also the gcode is long and wants me to consider to replying in several posts. Would you like me to email it to you? No bitsetter. Here is a picture of the project when I had the origin on bottom left.IMG_2975

To post anything that is not in a file format supported by the forum, the easiest is to make a zip file and post that.
If you already sent your file to support, that’s fine they’ll take care of you, and in the meantime we can discuss possible culprits here.

First thing first: during the initial Z retract, do you see it/hear it actually making contact at the top (it usually comes with a bad grinding/clicking noise) ?

Yes it made a noise.

I saw it hit. Not just that time but every time since on this project.

Ok then, so problem confirmed (thick stock + large retract = the machine tries to retract further away than it mechanically can, and when it contacts the top, it skips/loses steps. Then when it plunges toward the materal, it thinks it’s higher than it actually is, resulting in a cut that’s too deep)

Try reducing retract height if your workholding strategy allows ?

I will try that. Thanks

That was it!! Thanks for the help.

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Glad you got it sorted! Man its a bugger watching it drive up then slam into your work!

I always aim for 0.5" or 12mm above the material or highest clamp

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Isn’t it silly that the machine and program is designed and set to allow itself to crash into its own frame…

Finger on the stop switch guys…

That was before I had limit switches and soft limits, now when I load my gcode I get a warning that my machine is going to go outside machine limits.

Still hasn’t stopped me running into clamps though…

Another trick if your stock is tall and you don’t need to cut deep is to mount the router up higher for the job.

How do you get a warning? Are you using something other than Carbide Motion? That sounds very useful!

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Yeah I am using LinuxCNC. I had to replace my control board due to Issues with a noisy power circuit at my house causing disconnect issues.

Basically it’ll show you your machine limits as a 3D box on the preview screen, then when you load the gcode you can see if your toolpath is outside the limits, if it is and you click start job it comes up with an error saying ‘Line 35 takes machine out of limits - continue?’ Then a yes/No click box.

I have never had issues hitting stops since I changed.

Maybe this could be incorporated into CM in future? @robgrz


That’s absolutely on the TODO list.


Marvellous :smiley:

FYI The LinuxCNC implementation is done fairly well, identifying the axis that will be taken out of limits, as well as the specific line of Gcode. This makes troubleshooting the cause quite easy


Shoot me a screenshot of what LinuxCNC looks like with one of your files, we’re always looking for ideas.

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