Underextrussion at lower layer thickness

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Sigma
Posts: 6
Joined: 15 Oct 2017, 21:35

Underextrussion at lower layer thickness

Post by Sigma »

Let me start saying I have already solved my problem (and it was not KISSlicer fault to begin with), but I want to leave this here in case someone else is struggling with the same. Please mods, move this post if it does not belong here :)

I downloaded KISSlicer and tuned my profiles, etc. The quality was pretty good. The problem was when I tried printing a small model using lower layer thickness (I ussually use 0.2mm). For small models, and 0.2mm layer thickness the quality was acceptable but not the best. At lower thickness it was almost garbage :cry:

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At 0.08 the print was....
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I tried printing single walled sqares, and they came out pretty good. My caliper measured 0.4mm in the walls on every model (+- 0.02mm or so) :?

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I also calibrated my printer e-steps over and over again. But nothing worked. The lower the layer thickness, the worse it was.

Well... 2 days later (and tons of little angels later :P ), I realized what was wrong. :!:

All this time I was printing using Relative-E distances, and such small models (and layer thickness) generate very small E movements. So small the firmware simply ignores them. :(

I mean, I think it's reasonable. Should have realized sooner :oops: .

So in the end, I switched to absolute-E and everything is fine for small layer thickness (and I can finally use that sweet variable layer thicknes feature 8-) )

Finally, a nice 0.08mm print...
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Again, I know this is not KISSlicer fault. Not even sure it is my firmware fault (idk, the firmware could keep track of small movements and accumulate them, but again, I never updated my firmware in the first place :oops: )

So that's it. I only regret I used orange PLA, it's so bright it's really difficult to take good photos :P
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pjr
Posts: 692
Joined: 05 May 2015, 10:27
Location: Kamnik, Slovenia

Re: Underextrussion at lower layer thickness

Post by pjr »

Sigma wrote:the firmware could keep track of small movements and accumulate them
Marlin does exactly that. It uses a float to add the relative extrusion value and then extrudes the difference. The biggest issue with this is that it uses a "float" with (I believe) only 7 significant figures of accuracy. So I reset the extrusion every tool change or layer (G92 E0).

Peter
Sigma
Posts: 6
Joined: 15 Oct 2017, 21:35

Re: Underextrussion at lower layer thickness

Post by Sigma »

Yeah, I'm still not sure, but I think the problem is my firmware. I bought a Tronxy p802m kit more than a year ago and came with an old repetier firmware (0.91 I think, not sure right now). I may need to upgrade my firmware.... sometime :P
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