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Inconsistent Extrusion  

Active Member
Inconsistent Extrusion

This was printed with a Mk2s and 1.75mm PLA. I recently did a print of the marker from dead space at 20 cm tall and about 70% through it had fallen down and there was already a mess of plastic that kept extruding. After that I did two smaller prints which came out ok, even though there was a bit of scarring in the first layer but not bad overall.

However next print I did the first layer just would not stick to the bed, and I started noticing that the width of the extrusion was not consistent.

I tried to do some cold pulls, I'm not really sure if I'm doing it right but nothing seems to come out. The weird thing is that when I unload and reload the filament the bit it shoots out to clear the color seems to have consistent width, but when printing on the bed it just goes wrong. The last image shows how the filament looks after loading it, it does measure 0.4mm pretty consistently.

I am going to try getting a needle or thin wire and seeing if I can get it in.

What do you think it is? Could it be dirt or a pratial clog, or is it something else?

Posted : 13/01/2018 6:42 pm
Active Member
Re: Inconsistent Extrusion


I think I might know what's going on. I had a problem like this a while back and the way I was able to fix it was by making sure the little piece on the motor that pushes the filament through is tightened enough. If it isn't it can cause the printer not to push out some of the filament on some prints.
Hope that helps.

Posted : 19/01/2018 7:01 pm
Active Member
Topic starter answered:
Re: Inconsistent Extrusion

Hi! Thanks for the reply. I tried a lot of thing since, and I've gotten some good prints and some bad prints. Main problem seems to be first layer adhesion, after that everything works perfect. But the weird thing is that when printing the live adjust z calibration surface found on this forum, everyhing works great at -0.625.

I've realised my bed is a bit scratched, and some of the scratches seem a bit deep to be just the PEI sheet but I'm crossing my fingers that they are not. Sometimes when printing something big, everything adheres well but when the extruder goes over a scratch it doesn't stick and ruins the whole print.

Also, the PLA I'm using might not be the best. We don't really get many of the well known PLA brands here, so I'm using a local one which might not be the greatest. I went through a white PLA spool and switched to a grey one, and have noticed a lot more stringing and residual looking strands during extrusion.

To be sure, could you refer to what the "little piece on the motor that pushes the filament through" is? Is it the one shown in step 11 here?
I got the printer assembled, so I'm not that familiar with this part.

EDIT: Oh and one more thing in case it helps someone, right now I'm trying out cleaning the PEI sheet with acetone (nail polish actually because it's what I have right now, with a low content of acetone) like it says here:
I usually clean the heatbed with 99,9 IPA but filament was still just sliding around the bed. Right now after using nail polish it looks like a print of 5 coins that I tried yesterday and failed is now going well.

I also have some adhesive spray that comes with the PLA I bought, but I thought the point of a heatbed was that you didn't really need anything else for bed adhesion.

Posted : 31/01/2018 4:42 pm
Re: Inconsistent Extrusion

Nail polish remover usually has oil in it. Which is not good for heatbeds.

Check the content list.
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 : 31/01/2018 8:38 pm
Re: Inconsistent Extrusion

by the way: inconsistent extrusion might as well been caused by a leakage of the hotend.
if there is a leakage (most often when nozzle and heatbreak doesn't seal each other), you'll get an inconsistent pressure and the molten filament sometimes finds an escape option beside the nozzle.

dem inscheniör is' nix zu schwör...

Posted : 01/02/2018 11:09 am
Noble Member
Re: Inconsistent Extrusion

Common issues can be found here:

I am guessing your don't have the tension (screws on the extruder) set correctly.

Any advices given are offered in good faith. It is your responsibility to ensure that by following my advice you do not suffer or cause injury, damage or loss. If you solve your problem, please post the solution…

Posted : 06/02/2018 4:38 am