Bad limit switch work around?

So yesterday I got a board taped down ready to do a 3D cut on my XXL. Went to home and got an error - something about limit switch. Looked at CM and it showed Z limit switch as active, blue light on as well. Removed Z wire from board, light went out, plugged back light on. Just to be sure I didn’t have a short in the wire, I clipped one of the wires about 6" from the switch - light went out. Definitely a bad switch! Contacted Carbide 3D, spoke with Brandon (nice guy) and new switch will be going out Monday. In the meantime my machine is useless.

My question is, is there a work around to bypass the homing until the new switch gets here in about a week? Barring that, my other question is, if there is no bypass will my tape and glue hold down be good a week or so from now, or should I remove it and redo it when I get the new switch?


Folks have talked about using a switch from an appliance such as a washing machine lid (I miss Radio Shack).

One could revert to Grbl 0.9 and use CM3: GRBL 1.1 and Carbide Motion 4 or use a 3rd party tool which doesn’t require homing.

If your job is such that you will not need to re-home before completing it, you could temporarily use a difference G-code sender, say CNCjs, and use the “$X” GRBL command to unlock the machine (i.e. skip homing) and run your code normally.

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After mine broke, I cut out and soldered in a micro lever arm similar to these

But I had to make a small bracket to attach as the holes don’t align. But it works fine.

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Did you check that the switch little button is not stuck in the ON position? I had one of those and I was able to pull it out until a replacement was shipped to me.

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I think we still have Fry’s in San Diego, but I’m not sure because Amazon prime can usually get almost anything (including limit switches) to me the next day.

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If you are in a situation where you can’t stop working, then you really should have spares for switches, bits, belts and other stuff. Perhaps C3D can include switches in the repair kit? I don’t remember them being in there.

@luc.onthego - I did check that. The switch plunger works fine, it’s got to be the internals of the switch .

@CrookedWoodTex - I do have bits and recently upgraded to steel belts and I have plenty of that left over. I believe Brandon said he will send a couple switches for this. I’m also holding out for the C3D proximity switch upgrade that @Luke (I think it was him) hinted about.

@Julien - Will CNCjs work with the bitsetter right out of the box? I did save this toolpath using the “Shapeoko Toolchange” post processor.

Not “out of the box”, but @neilferreri’s Bitsetter macros would allow you to use it


So it’ll start with bit 1, run bit setter macro, run the first bit, tell me to change to second bit, run macro again and so on?

Sorry for the delayed answer, timezones and all that…

If you want to use CNCjs and Neil’s macros, first you will need to do a one time configuration by updating the PROBE_X_LOCATION, PROBE_Y_LOCATION, and PROBE_Z_LOCATION in the Initial_Tool_BitSetter macro, to match your machine configuration (just like you do with CM when installing the BitSetter).

Then the workflow is

  • generate a multi-tool g-code file normally (i.e. it will have M6 commands in it)
  • install first tool and set zeros normally
  • run the Initial_Tool_BitSetter macro
  • run the file normally
  • CNCjs will cut the toolpaths for the first bit, and then it will come across an M6 command, and will pause there: that’s when you change the bit, and run the New_Tool_BitSetter macro
  • then click to resume the job
  • rinse and repeat if there are additional tool changes (i.e. run New_Tool_BitSetter each time there is a pause for tool change)

But I probably can’t set the bit setter location right now since it won’t know machine position without homing, correct? So I think I’ll have to do it with individual files until I get my Z limit switch

…indeed. No point in messing with the macros to work in full relative mode, for just a temporary workaround.

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Being a Boy Scout many years ago, has taught me to Be Prepared; so while it’s not a work around, but moreover info for the next time. I stock, extra switches, belts, and a Router (as will as a few other items) to eliminate any downtime due to a breakdown.


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