Lines on bottom layer where infill print has changed direction
 
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darren.s2
(@darren-s2)
New Member
Lines on bottom layer where infill print has changed direction

Hi and thanks for reading.
I am trying to dial in my printer to get the desired outcome and not sure how to proceed.
Mk3s assembled from kit, tested and calibrated 1st time with no issues. Have completed number of prints with no significant issues.(but it's still kinda new)

I am now trying to print some switch panels and am after a consistent looking front face (bottom layer). I'm using the powder coated sheet and generally the result is ok, but as you can see from the picture there are some noticeable lines. The face actually seems to be quite smooth and there is no detectable change in height, yet they are clearly visible.

Settings are Prusaslicer 2.0.0 , Prusa PLA 215deg/60deg silver, Standard 0.20mm Speed Mk3 – but with modifications tried (see below)

When the print commences, the 1st layer infill is printer left to right on 45deg as per standard , skipping sections due to the holes. Then the printer prints right to left and fills some gaps and so on. It is where the left to right sections meet the right to left printed sections that the lines occur. If the printer goes back and continues a section in the same direction there is no line (or not as noticeable).

So I am assuming that the slicer decides in what order and direction the layer infill is printed. Is this the case?
If the layer would print in only one direction, (eg left to right) these lines wouldn't appear (or would not be so noticeable) but I can see no way of controlling this. I have also tried varying a range of setting to see if I can alter the outcome. Usually this just results in a worse print than what I have.
Z Axis lower to squeeze on to the plate hopefully eliminating the lines - issue remains and rippling appears
First layer height 0.2/0.3 - no detectable change
First layer extrusion 0.3 to 0.6 – less noticeable lines on lower setting but then run in to issues of incomplete coverage and small gaps between print lines, so it is hard to tell
I have also tried reducing the speed a bit and upping the temp a bit.

This is not to say I’m not altering the right settings, but perhaps not in the right combination?

So with all this in mind, can anyone give some pointers on what else to try?
Or is there some way I can force the infill to be only printed in one direction (eg left to right)?

Thanks for your consideration!

 

 

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Posted : 13/08/2019 9:42 am
JoanTabb
(@joantabb)
Moderator
RE: Lines on bottom layer where infill print has changed direction

May I suggest that some of the effect you are seeing is due to the sparkly particles in the filament, these are causing an optical effect that looks like texture in the surface finish.

a plain colour will give a different look

also using a pattern on the lower surface will disrupt the current slicer path optimisation, and possibly give a more pleasing result,

try hilbert curve, or Octogram spiral!

regards Joan

I try to make safe suggestions,You should understand the context and ensure you are happy that they are safe before attempting to apply my suggestions, what you do, is YOUR responsibility. Location Halifax UK...
Posted : 13/08/2019 10:03 am
Neophyl
(@neophyl)
Famed Member
RE: Lines on bottom layer where infill print has changed direction

This is already on the github reported as an issue but you are essentially right in that the printing direction causes a slight difference where they meet from 2 different directions.  At the moment there nothing you can do about it except experiment with various pattern options as suggested by Joan.

Posted : 13/08/2019 10:48 am
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(@)
Illustrious Member
RE: Lines on bottom layer where infill print has changed direction

Slowing print speed is the most effective way to reduce or eliminate the effect.  That and minimizing infill direction changes by adjusting angle.

Posted : 13/08/2019 1:00 pm
Sembazuru
(@sembazuru)
Prominent Member
RE: Lines on bottom layer where infill print has changed direction
Posted by: joan.t

May I suggest that some of the effect you are seeing is due to the sparkly particles in the filament, these are causing an optical effect that looks like texture in the surface finish.

a plain colour will give a different look

also using a pattern on the lower surface will disrupt the current slicer path optimisation, and possibly give a more pleasing result,

try hilbert curve, or Octogram spiral!

regards Joan

I haven't tried octogram spiral, but I've found that I really like the look of the hilbert curve with the Prusa PLA (Filament PM) Silver. Gives it an almost holographic look.

See my (limited) designs on:
PrusaPrinters - https://www.prusaprinters.org/social/1448-sembazuru/prints
Thingiverse - https://www.thingiverse.com/Sembazuru/designs...
Posted : 13/08/2019 4:09 pm
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(@)
Illustrious Member
RE: Lines on bottom layer where infill print has changed direction

One other thing to consider: a poor looking layer one seldom looks as bad after a few layers of plastic are down.  It usually turns out looking quite good, despite the initial "ugliness" of the single layer.

 

Posted : 13/08/2019 4:30 pm
darren.s2
(@darren-s2)
New Member
Topic starter answered:
RE: Lines on bottom layer where infill print has changed direction

Thanks everyone for the prompt and helpful replies!!

Much appreciated by a first time poster.

Joan, I hadn't considered that maybe the silver would be more prone to showing the issue. You were right, I printed in plain black and it was still there but you really had to tilt the panel in the lights and look pretty hard to see it. I also tried the hilbert curve (thanks too sembazaru) as it seemed most likely to give a uniform finish across the whole panel, which it did (so that worked) however it looked a little too granular for this use, so I'll do some more work with sold colours. Still hoping to use silver but at least I know Black works. 

Neophil, thanks for the heads up, I hadn't considered poking around github. I still couldn't find the issue though... any chance you could link to it? I'm keen to know if this is just a recent problem with PrusaSlicer and is it likely to have a fix soon, or do I need to look at some alternative slicer for this particular part?

Tim, 1st layer speed is 20mm/s which I thought was quite slow. Do you suggest slower again? With regard to the ugly 1st layer, I understand what you mean. In this case the part is fully printed and flipped over in the picture and when assessing the overall outcome. I did adjust the angle as you suggested which has also helped the end result slightly and makes the lines that you can see at least look more uniform. It also reduced the number of direction changes - Thank you.

 

 

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Posted : 14/08/2019 11:45 am
Neophyl
(@neophyl)
Famed Member
RE: Lines on bottom layer where infill print has changed direction

The github issue is https://github.com/prusa3d/PrusaSlicer/issues/2556 I believe it was actualley opened by tim-m30 (Tim please correct me if I'm wrong about that).

Posted : 14/08/2019 1:21 pm
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