suddenly 4mm space at z 0

Hi all,

my 2nd M90 (I bought it used from a German member here) is currently at a friends place. It was a few weeks before in our local hackerspace. Almost every week there were broken parts (due to too much force from the owner before). So I replaced both z motor holders and the top bar clamps. Then I did a full calibration and gave it to my friend.

The first few days he printed very well, but suddenly there is a 4mm gap when z goes to 0. I'm out of my ideas. All parts are fixed. Nothing loose. I proved the endstop switch. The x axis is level as it should be.

Where are the 4mm coming from?
Sure I can do the steps to set the z home point to the "new" situation - but I think the error goes away as it came - and then the nozzle will drive into the bed.

Any ideas?

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MfG / Regards

Stefan

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Blog / Gallery / Wiki / Mendel90 kit since Sep 2013 from Nophead / Original Prusa I3 MK3 since Feb 2018 /
OpenScad Workshop: Kursdateien
Octoprint Patron since April 2016

a few to try:
- slippage on the left side smooth rod clamp
- binding on the threaded rods (check for damaged threads, try greasing
- nuts not fully seated in the x-end clamps
- loose screw on the bed
- slicer of choice bed offset

is the coldend of the hotend in good condition?
When it gets too hot it melts and the whole hotend can shrink and it is getting shorter

Another possibility not yet mentioned is that perhaps the X carriage is not fully seated on the linear bearings. This can happen if you are not using zip ties to hold the carriage in place and hit some kind of bump during printing, or perhaps if your friend removed and reattached the carriage without checking the bearings were fully seated.

Maybe the extruder was not touching the top of the cabity in the wades extruder where it is placed.

Perhaps the Y carriage wasn't seated properly and now is. If I get something like that happening then I check the whole machine for loose parts. I would check the z calibration with the X and Y carriages at each corner which will narrow the possibities.

Hi,

again, I checked all parts of beeing loose. After I did the Z home point there was a 2 weeks phase of working good. Last week it starts with a slightly new Z. Deeper than the glas. I advised my friend to play with the z offset in slic3r. It seems that from day to day it is once more and once less.

I've one idea: When I got it as a used kit, there was an automatic leveling change from the owner before. I did not use it, instead I built it as in the original assembly manual - but there was a different z endstop switch (with a metal thing and a roller) - it worked very well, but I think the exact point when it switches isn't all the time the same point. Could that be the reason of all the z level problems? Are those switches possible?

Edited 1 time(s). Last edit at 05/09/2016 02:55AM by bastard.

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MfG / Regards

Stefan

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Blog / Gallery / Wiki / Mendel90 kit since Sep 2013 from Nophead / Original Prusa I3 MK3 since Feb 2018 /
OpenScad Workshop: Kursdateien
Octoprint Patron since April 2016

Switches with levers will be less accurate because any non-repeatability of the basic switch is multiplied by the lever ratio. However I don't see how it could make 4mm difference unless the switch is broken.

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Not sure if you have solved your problem yet put I have a very similar one (I made a thread before finding this one). After discovering the Z limit switch is broken I replaced it. That didn't solve the issue. Then I discover the Z brass nut is totally worn out! It just spins on the threaded rod. Oh my. And I have always keep the rods well oiled. Well, I have spare nuts so will replace both sides. I gather we have had our machines roughly the same length of time and maybe your nuts have worn out too?

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