Home Position for print head

I have purchased a 3mm thick Borosilicate Glass plate to print on. Is the home position for the print head fixed or related to the calibration. I do not want the print head to come down onto the glass and crack it.

I’m not sure if the homing is relative to calibration or not. I propose a fairly simple test, something you can do before ordering/mounting your new plate.

Without the plate, print a 3mm thick block. Or better, print something from 0.1mm to 3mm thick, with 0.1mm increments, so you measure the actual gap. (I looked on thingiverse for about 30 seconds, and didn’t see anything). Something like https://www.amazon.com/CTA-Tools-3235-Ramp-Type-Gapper/dp/B00144AZ6K/ref=sr_1_4, but in metric and up to 3mm thick. If you made one, I think I’d print it out for general household use.

If you’re going to be mounting the 3mm glass plate on top of the existing heated plate, I’d start by calibrating with the existing bed. Once you’re done, raise every point by 5mm, and save. Now start the calibration again, and see if the homing step would cause the print module to contact the plate. If you’re not sure, power off the snapmaker while it’s at it’s lowest homing position, and measure the gap. I would also repeat this during printing by starting a print, power off in home position, and measure the gap again.

If the gap is big enough in both cases (indicating that homing is relative to calibration), go ahead and mount your glass plate and calibrate with your glass plate on. If the gap isn’t big enough (indicating that homing is absolute), I’m unsure what would happen. I don’t think the Z axis has enough power to crack a borosilicate glass plate using the 3d print module underside. But having something in the way while homing might throw off the calibration. You could test that by leaving the 3mm measure tool in the front left corner of the stock plate, and start a print. If the Z axis clicks, it’s not gonna work. In that case, you might have to notch out the front left corner and sacrifice a bit of build area.

Be aware that updating the firmware will reset the calibration. So you’ll want to unmount the glass plate before you update firmware, then repeat these steps.

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The home position of the Snapmaker Original is a fixed position because of the endstop switches.-
Maybe its possible to adapt the position in the alu frame but this would be a little tricky i guess.

if you put the 3mm glass on it would collidate at homing.

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Hi Craig,
Thanks for this. I was not expecting such a detailed reply or so quickly. I will give it a try. I was going to try a calibration out on a bit of 3mm acrylic I have handy that I thought might be a bit more robust if it is not calibration related.
Regards
Bryan Parkinson

Hi Chris,
Thanks for that, I have it on good authority that some users are using Borosilicate Glass plates so there must be a work around if there isn’t enough space for the print head to home if it is absolute rather than related to calibration.
Regards
Bryan Parkinson

It would be possible if you put the axis about 3mm higher, print a sheet :+1:

Oh, that’s a good idea. Use a piece of the same glass to raise the Z axis. You can keep your existing calibration, and you won’t lose 3mm of Z volume.