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Nozzle Scratches after a few layers

Posted: Fri Mar 08, 2019 3:31 pm
by in5omni4

I've made the Bondtech Extruder Upgrade. After adjusting the Vref to 0.5V and the X,Y,Z to 0.8V (checked it twice) the right nozzle scratches after a few layers. I am printing the Standard Examples 20mm_Calibration_Box and 35 mm fan bottom cover. It seems the Z motor works with too less steps or voltage. E steps are 415 as described! The supporting plate will be printed properly. Scratching begins after 5-10 layers.

Any ideas?

Printer: N2 Dual with Bondtech Extruder
Filament: PLA 1.75mm, red
RaiseTouch and Firmware are newest.

Re: Nozzle Scratches after a few layers

Posted: Tue Mar 12, 2019 12:20 pm
by in5omni4
Done some tests. Double checked the Vref of 0.9V, same. Switched the z driver, no changes. Next I'll level the bed. But that has nothing to do with the z-height consistency between the layers. I've noticed the z-shifting of the bed between the layers. So, he's not losing the command. Z stepping is 800 as default.

Re: Nozzle Scratches after a few layers

Posted: Thu Mar 14, 2019 7:56 am
by Squenz
I'd suggest to calibrate E-Steps on all extruders before hunting any other ghosts.

I did mine years ago and it came out at 437 and 439 or so, iirc.

Makes a huge difference and gives you much more consistent prints in the long shot. You might need to turn down the flow rates on your slicer profiles, what's bit of a pita, but you'll be happy you gone through it.

Re: Nozzle Scratches after a few layers

Posted: Thu Mar 14, 2019 8:59 am
by in5omni4
Yes, indeed.
Replaced the z driver to check if it is skipping steps or having other problems. I actually swapped it from one of the extruder, because they are of the same model. The results were the same.
I think I'm at a state where I can say the hardware is OK again and it's some tweaking of settings.
Leveled the bed, played around with different distances between the nozzle and the print plate. Scratching is now not as hard as before, so I can print a whole model without risk. It is more a diving/smearing through still warm filament strings in the first few layers. After 10-12th they're coming out clean and consistent. Lowered the heatbed to 40°C (Buildtek Flexplate) made it a bit better. Without heating it, the models sticking very hard to the surface and the effect of geometry/layer distortion remain the same.
I think it has something to do with the nozzle distance, feed rate and temperature. Are the first layers cooling down slower because of the proximity and warmth of the heatbed and/or the nozzle isn't near enough to push the filament down and make the strings slim enough. I've noticed that the nozzle is pressing down the warm an still flexible model in this first layers.

I'm printing with 0.4 mm nozzle and 0.25 mm layer thickness. A this time 0.10 mm will not work.

Re: Nozzle Scratches after a few layers

Posted: Thu Mar 14, 2019 10:38 am
by in5omni4
OK, this is new: Without any plattform additions layer 15-20 are inaccurate.

SOLVED: Nozzle Scratches after a few layers

Posted: Thu Mar 14, 2019 1:13 pm
by in5omni4
Z-Coupler checked, playing around with the manual moving of the z-motor, noticed some lost motion between the 4th and 5th mm of height (reproducible). :!: Tighten all grub screws - the upper ones were a bit loose. After checking again, everything is fine! Prints without any issues.
Looking back, all things make sense. Afterwards one is always wiser. ;)

Re: Nozzle Scratches after a few layers

Posted: Tue Apr 09, 2019 9:17 pm
by DeX
What do you think about this situation: maybe it is similar problem?