How to calibrate z=0

Hi Guys,

I´ve been struggling with this for a while and must confess my patience is gone.

I am trying to calibrate the Z axis but I am missing something. The way I try to do this now is to put a "caliper" (it´s an old PCB board (1.65 mm thickness) which has a wire attached to it and also connected to the ground of Z-Min connector. The extruder has an alligator clip with a Wire connected to it and to the signal of Z-Min connector. So, sending a M119 I can see if the circuit is closed) and lower the extruder until it touches it then I send a G92 Z1.65 command and then M500.

Next, I home Z-Axis and send it to z=0.4 using G0 Z0.4 I was expecting it to be exactly 0.4mm from the bed but it crashes all the time.

I am using Marlin 1.1.6 and Repetier as host.

Could you guys teach me how to do it correctly?

Regards,

Marcus

“Next I Home the z axis”

What firmware? Do you have an end stop?

In most firmwares, homing an axis equates to moving it to the endstop (that’s a known position) and then loading the value configured with M851 as the current Z.

That completely overrides all you are doing with G92, which would not be saved to EEPROM anyway.

Agreed. when you start a print it tries to home X Y and Z before printing.

Hi Guys,

Thanks for the answers. I am using Marlin 1.1.6 and I have a Endstop configured as Z-Max.

Since I shall not perform a Z-Home, what should be the operational sequence? Should I do as follow?

• Send G92 when Z is above the table, at a known distance;
• Send M500;
• Start printing without homing Z-Axis;

Regards,

Marcus

If you home to Zmax the bed or X axis has to go all the way down/up before returning to the printing position. If there is any error in your Z axis calibration sending the Z axis all the way back to z=0.4 may miss the mark completely.

The normal way is to put the Z limit switch at Z=0 or close to it. Then you home to that position which is either the print position or close to it and the calibration of the Z axis won't matter much, at least as far as getting the first layer to stick is concerned.

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Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]

Does your printer have a Z probe? If so, you can use the probe to set an accurate Z=0 height after homing. Or you can use the Z probe to do Z homing instead of the switch.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

Hi Dc42,

Yes, my printer has a Z probe.The way I try to do this now is to put a "caliper" (it´s an old PCB board (1.65 mm thickness) which has a wire attached to it and also connected to the ground of Z-Min connector. The extruder has an alligator clip with a Wire connected to it and to the signal of Z-Min connector. Therefore, when the tip of the nozzle touches the PCB board, a signal is sent to RAMPS informing that Z-Min was reached.

Could you teach me how to calibrate the Z axis using the probe as Z-min?

Thanks,

Marcus

If you have RAMPS hardware then I guess you are using either Marlin or Repetier firmware. I am not very familiar with either, so I'll leave to someone else to give you instructions.

Edited 1 time(s). Last edit at 11/29/2017 02:19PM by dc42.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].