Paper like, flexible prints when using black PLA

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reibuehl
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Paper like, flexible prints when using black PLA

Post by reibuehl » March 1st, 2018, 10:47 am

Hi all,

I have a really strange problem: I printed a part in white PLA (ColorFabb I think) and then changed the infill from 20% to 100% and printed it with black PLA from Material4Print. The black part which should be sturdier, is nearly flexible:
WIN_20180301_16_33_03_Pro.jpg
On the picture I press both parts equally, the white one hardly flexes at all and the black 100% infill part flexes as if it would be Innoflex! The layers on the black part seem to be only connected in the Z-Axis but have close to no adhesion between parallel passes of the nozzle. The wall of the part that I press on feels like layers of paper standing upright next to each other.

What could I change to print proper parts with the black PLA?
Reiner.

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LePaul
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Re: Paper like, flexible prints when using black PLA

Post by LePaul » March 1st, 2018, 12:16 pm

Same slicer settings on each?

reibuehl
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Re: Paper like, flexible prints when using black PLA

Post by reibuehl » March 1st, 2018, 12:48 pm

Yes, except for the different infill. All done in Cura 15.04.
Reiner.

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Re: Paper like, flexible prints when using black PLA

Post by Roberts_Clif » March 1st, 2018, 1:37 pm

The only thing I can thing of that could cause this is if you accidentally changed the Filament diameter from 1.75 to 3.0mm (Have done this myself).
That will cause under-extrusion or even a clogged nozzle.
Electronics Technician / Computer Programmer

reibuehl
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Re: Paper like, flexible prints when using black PLA

Post by reibuehl » March 1st, 2018, 2:17 pm

I checked that. I use the builtin PLA profile of the UM2. I also did a quick check with the caliper and both filaments seem to be more or less the same diameter: The white PLA was 2.84 and the black PLA was even a little more, more like 2.88. So I would expect a little over extrusion but not such under extrusion, or?
Reiner.

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Re: Paper like, flexible prints when using black PLA

Post by LePaul » March 2nd, 2018, 9:57 am

That's a truly weird one! I'd almost wonder how it would work using the white pla

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Re: Paper like, flexible prints when using black PLA

Post by reibuehl » March 2nd, 2018, 10:14 am

Unfortunately that roll is out... :-( I tried printing with higher temperatures since some people on the net mentioned that Filament4Print PLA should be printed towards the upper end of their recommended temperature range of 190-225°C. I also tried bumping the feed rate to 105% but nothing helped. The results seem to get even worse.
Reiner.

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Re: Paper like, flexible prints when using black PLA

Post by reibuehl » March 2nd, 2018, 10:16 am

I have ordered a spool of black DasFilament PLA now to see if that works better.
Reiner.

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Re: Paper like, flexible prints when using black PLA

Post by danilius » March 9th, 2018, 3:08 am

This might be down to a couple of things: the nozzle or bowden tube. If you don't have the Olsson block upgrade, you definitely want to get one now. With a quick nozzle change, you can eliminate a partially blocked nozzle as the cause.

If you do have an Olsson block, then here is a neat way to ensure the nozzle definitely clean: use a heatgun and some spare plastic to perform cold pulls with the nozzle dismounted. You are probably going to need pliers to hold the nozzle, be sure to avoid damaging the threads by not holding the nozzle by the threads.

If it's the bowden tube, that's much harder to diagnose, but here too there is a neat trick. Reverse your bowden tube. Essentially, take it out and stick it back it the other way around. Why? Because the tube gradually picks up a bend in one direction, which causes it to distort sufficiently to restrict the travel of the filament. Reversing the bowden tube cures that for a while.

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Re: Paper like, flexible prints when using black PLA

Post by reibuehl » March 9th, 2018, 3:27 am

I do have the Olsson block and did a few cold pulls but that seems to have no effect regarding my issue. I think I can rule out the nozzle and bowden since before and after printing with this particular spool of black filament, I could print fine with other spools of filament.
I wonder now if this is just a bad batch since I had black PLA from Material4Print before and that one was printing fine too. I still have an unopened 1 KG spool of white PLA from them and now I wonder if I should try to sell it before opening it and running into the same issues there...
Reiner.

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Re: Paper like, flexible prints when using black PLA

Post by danilius » March 9th, 2018, 4:32 am

I forgot to mention one more possibility, which is that the spool is damp. Try drying it at 45C for a few hours. I use a food dryer.

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Re: Paper like, flexible prints when using black PLA

Post by reibuehl » March 9th, 2018, 4:49 am

That is a good idea. I have contacted the manufacturer, so I will wait with the drying procedure until they come back to me. Maybe they just replace the spool...
Reiner.

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