Line width changes depending on the direction the print head moves

Question

I just re-ran all basic calibration steps from the Original Prusa i3 MK2 Manual.

Now, when doing the first layer calibration, lines that are running in positive X direction are ok, while those running in negative X direction are severely squished.

(The "waviness" of my print bed is an artifact of the camera lens distortion of my smartphone)

I already did Bed level correction, so each line is exactly the same width over its entire distance and tried to raise the live-adjust Z, but that leads to the thin lines not adhering at all. My printer is 100% stock, I modified nothing about it.

What can I do to troubleshoot this further?

Can you check the g-code to be sure the head speed remains the same for movement in both directions? — Carl Witthoft, Jun 29 '18 at 13:49
@profesor79 I tried to wiggle it, but it stays put. My current assumption is a damaged or partly clogged nozzle. — iFreilicht, Jun 30 '18 at 20:57
@CarlWitthoft I don't think that can be the case. I did this calibration step successfully when assembling the printer for the first time and didn't change the gcode in the meantime. It was supplied with the printer. I'll have a look though. — iFreilicht, Jun 30 '18 at 21:01
Check the nozzle. I scrached my nozzle over the metal heat bed by accident...it becomes nasty... and produced inconsistent line widths. Since the metal of most nozzles is brass it is easy to machine...and easy to deform. And since you will need several nozzles over time get some new ones and try with them. — Horitsu, Jul 02 '18 at 04:58

score 3 · Answer 1 · edited Aug 04 '18 at 15:14

3

As pointed at by @Horitsu, the Nozzle was the problem. Its outflowing hole was not perfectly round anymore, leading to a higher extrusion rate in one direction than others.

I exchanged it, and now everything works great again!

edited Aug 04 '18 at 15:14

0scar

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answered Jul 04 '18 at 06:08

iFreilicht

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score 3 · Accepted Answer · edited Aug 04 '18 at 15:14

Due to the advice from @0scar i formulate my answer in the comments as a proper answer ;)

Check the nozzle, if it is in shape and good condition. I scratched my nozzle over the metal heat bed by accident...it becomes nasty... and produced inconsistent line widths. Since the metal of most nozzles is brass it is easy to machine...and easy to deform. And since you will need several nozzles over time get some new ones and try with them.

Also not every new nozzle will be perfect, so defect products happen, especially if they are cheap and have really tight measurements.

Line width changes depending on the direction the print head moves

2 Answers2