rafal.d
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Joined: Apr 28, 2017 8:07 pm
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Inconsistent first layer

Feb 02, 2019 12:01 pm

Hello all,

after a break for several months I began printing again and am experiencing problems with the first layer I never had before. The lines near the edge of an object are visibly much wider than the inside part of the model, like ghosting but horizontally - any idea what might cause this?
first_layer.jpg
first_layer.jpg (964.56 KiB) Viewed 129 times
The same is visible on the small rectangle printed during FL calibration from the firmware, the inside looks different from the edges and it's also unevenly distributed, could it still be a bed-leveling issue, extrusion/retraction problem or a problem with the PEI surface?

Any help is appreciated ;)

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tim.m30
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Joined: Sep 09, 2018 11:03 pm
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Re: Inconsistent first layer

Feb 02, 2019 7:52 pm

Some might say your z-level is a bit low. Raise the nozzle 25 - 50 um and try again.

Also - the problem seems related to acceleration zones, you may want to make sure your extruder and move settings are correct.

rafal.d
Posts: 49
Joined: Apr 28, 2017 8:07 pm
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Re: Inconsistent first layer

Feb 02, 2019 9:37 pm

Thanks tim, I actually thought it might be too high but I'll try raising it a bit and see if this helps. Not sure though what you mean by accerelration zones, I use the original slic3r prusa presets for printer/extruder settings.

What I forgot to mention though, this particular print was made with 0.2mm layer height and 0.3mm for first layer - but the original presets define a maximum layer height of 0.25mm, maybe this was the issue? I'll try another print soon with lower layer heights.

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tim.m30
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Joined: Sep 09, 2018 11:03 pm
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Re: Inconsistent first layer

Feb 03, 2019 7:26 am

Acceleration is when the nozzle starts moving. The nozzle must ramp from 0mm/s to the designated extrude speed (e.g., 40mm/s). This can make the first few mm of extrusion look different than the rest of the line. Normally not an issue, but in rare cases it might be. Jerk is the initial speed setting the motor controller is set to; it can be zero, but getting to some speed quickly helps reduce stringing. But too high a jerk will cause stalls (aka: layer shift). Once the controller is spinning the motor at the jerk speed, it ramps the speed up over time, so many mm per second. Actual distance traveled during this ramp period depends on many factors, but an estimate is possible by doing the math. Similar control is used for slowing the motor to avoid overruns.
Movement.png
Movement.png (9.62 KiB) Viewed 102 times

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