Head expanding?

[fuchs 0]

I recently levelled my printing bed with a dial gauge and got it around 0.1mm even.

As the Z-Axis endstop is a little bit pesky, i set it so that i had to turn the Z-Axis by hand some clicks when the print starts.

For the first prints, i had so turn the Z-Axis around 6-8 "clicks" (to raise it) and all went fine. After a few hours (3-4), i noticed that i didn't need to turn (adjust) the Z-Axis that much, only about 2-3 "clicks". 3 hours later the machine printed without any change in Z-height and i was very happy (altough a bit suspicious).

After 3 more hours (cumulated running time around 10-12 hours) i noticed, that the start of printing did dig into the tape on the printbed and i had to _lower_ the Z-Axis :shock:

So it seems that the printing head did maybe extend, eating away the clearance between the gantry/head and the printing bed.

I checked the screws on the head - they are still as tight as usual, also the clearing at the head mechanism are all the same.

Printing works now (in the evening) when i lower the Z-Axis. Will check what happens tomorrow morning, when the machine is cooled down.

Is it possible that the whole head (heater and nozzle?) expand after long prints?

I am yet running with the v1 hotend (v2 was delivered yesterday, but i didn't install it yet, as my v1 doesn't leak atm and i currently prefer printing and experimenting to maintenance :-P )

ADD: Or is this a case of the nozzle getting looes and unscrewing itself? I am starting to find very tiny traces of burned PTFE leaking between the aluminium heater block and the nozzle...

ADD2: Ok, in the morning the clearance between head/nozzle and printing bed is as small as in the evening, meaning that either in the course of yesterday the Z-Axis has moved/the printing bed did raise ("Ascension") - which is kinda unlikely - or the head has sagged / nozzle is coming loose.

[jpg 1]

Or maybe your z-endstop is pushed up a little bit when homing your z-axis.

Thus after each homing, the endstop triggers a little bit later (i.e. z-platform higher).

if you use the stock z-endstop and not a non mechanic one (like an optosensor or a hall effect sensor) and if the screws holding the endstop are not tight enough, i guess this can happen.

Another possibility is that you z-platform itself went higher, because the screws holding it got unscrewed with the machine vibrations?

[fluxline 0]

ADD: Or is this a case of the nozzle getting looes and unscrewing itself? I am starting to find very tiny traces of burned PTFE leaking between the aluminium heater block and the nozzle...

Are you sure this is not leaking? My leaks were usually dark brown/black, I think PLA once it sits around a bit, as in a leak, burns a little.

[phut 0]

You know if you're going to use a dial gauge to level your bed to only 0.1mm even then you may as well adjust till you just touch the head and turn the M3 screws in by 1/5th of a turn (or whatever your need your 'lift' to be) instead.