Z axis keeps crashing the bed when printing

When I do homing, everything works fine and there are no crashes. When I then go to try and print, the y and x axis home, and then the z axis goes down and crashes the bed. What could I be doing wrong? Thanks for the help.

And to put things in reference, I have an Ormerod 1

First things first, have you tested that Z is going the correct direction?

Yes it is

Ok. when does it hit the bed. the gcode generated by slic3r by default moves the Z axis up 5mm after the bed heats, and before the print head heats, then moves if back down to the layer height after the hotend is at target temperature. Does the hotend hit the bed then, or does it happen over time afterwards?

It hits after the hotend heats up. And it hits at basically x=0 y=0 if that helps

I sometimes have a similar issue, because the steppers do not keep up with the command to raise the extruder to 5mm. Sometimes the motors just make noise, but the command to drop back down works, and the result is as you describe. I usually wait for the hotend to finish heating, then immediately re-home the Z axis to move it to its correct location. it's not a good solution, but works.

I'm still looking for a better solution. I believe that the bias current on the Z steppers is adequate, and they move very well under program control, or using the commands in pronterface, it is only the initial raise/lower commands which I've seen cause issues.

When the bed heats-up it deforms or expands. Some hotends dimensions may vary a few too. So it raises a few tenths of milimeters. I think the problem is simple as that. You must do your bed leveling when everything's hot. Don't forget to raise your Z of the height of the thickness of your setup block or paper. I had some issues with slicer, the nozzle hitting one buldog clamps when reaching it's printing start position. Now I use the Cura engine (which is IMHO better), and raise 10mm on the Z then ramps-down XYZ to the printing position. So, no chance to hit any clip near an edge.

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Collective intelligence emerges when a group of people work together effectively. Prusa i3 Folger (A lot of the parts are wrong, boring !)

Marlin does have the endstops only active while homing at default , don`t know who came up with this silly idea.

Just go to configuration_adv.h -> mechanical settings

and comment the following line with two // out

Quote
//#define ENDSTOPS_ONLY_FOR_HOMING // If defined the endstops will only be used for homing

With this it at least won`t move into your bed anymore, but still don`t resolve probably loosing steps issues.

Chri

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