Inconsistent extrusion  

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simeon
(@simeon)
Active Member

Hi,

I'm sure this is a common problem - but I've tried many of the common solutions and I am a bit stumped.

I have a Prusa MK3s with Olsson Ruby Nozzle. The other thing to note is I was printing the ABS in an enclosure which reached about 45 C.

I noticed that that a number of my prints were showing regions of under extrusion. When I manually extruded filament I noticed that it doesn't come out consistently and more in spurts. It only took a very minor amount of pressure from me pushing the filament to assist the gears in extruding.

Figuring this was a clogged nozzle, I attempted to do a few cold pulls both with ABS and also some Nylon+CF I had lying around (ABS was first and then when the steps I mention below didn't work I did the Nylon+CF). The latter I did because I did do a number of prints with it and figured a cold pull would be ineffective with ABS if the build up is something with a higher melting point. Cold pull was ineffective.

I noted that my idler was a little lose so I tighten that up and had dramatically improved results but not perfect. I then inspected the idler and extruder gear and noticed that there was a bit of filament grind on them. I used some canned air and that cleaned them easily. Alas, this had no impact on the extrusion.

I inspected the gears and to my untrained eye they don't seem to be stripped.

I am stumped.

 

Posted : 01/08/2020 10:01 am
simeon
(@simeon)
Active Member

I should add that I'm not hearing and clicking or other noises.

Posted : 01/08/2020 1:04 pm
simeon
(@simeon)
Active Member

So just an update. I had a closer look at the idler door and I've noticed that its very deformed - particularly the bit where the idle gear sits and changing it's alignment. 

It clearly got hotter than I thought in the enclosure - though I am surprised because I thought the extruder was made from ABS and could handle higher than that. 

I managed to use a heat gun to do a temporary repair whilst I print some replacement parts. Looks like I need to do nylon+cf. 

Posted : 01/08/2020 2:22 pm
joan.t
(@joantabb)
Veteran Member Moderator

the extruder is typically PETG, with ABS for the fan shroud

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 : 01/08/2020 2:47 pm
simeon
(@simeon)
Active Member

@joantabb

Thanks Joan.

I reprinted the idler cover and all my problems went away. I've also noticed that the PINDA holder has deformed too.

I'm surprised because I thought PETG was suppose to handle 80 C. I can't believe it got to 80 C in the enclosure :S

I suspect not all the parts are negatively impacted by deformation (like the parts that merely act as housing), but I'll reprint them all.

Posted : 01/08/2020 5:00 pm
joan.t
(@joantabb)
Veteran Member Moderator

I printed my fan shroud in tough transparent red resin, on the SL1, because I don't print ABS...

i have also printed resin bondtech doors...  no complaints so far!

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 : 01/08/2020 6:45 pm
simeon
(@simeon)
Active Member

Further update. Replaced most of the extruder. As I took it apart the deformation was through the whole thing. Even the filament sensor lever was deformed.

Prints as if brand new.

I'll have to put some venting in and circulation to prevent the build up of it.

Still surprised. Would not have expected the temperatures I saw in the enclosure to have such an impact.

Posted : 02/08/2020 5:03 am
peter.m26
(@peter-m26)
Honorable Member

Enclosure needs to be under 40 degrees, that is the maximum for the air cooled extruder, even lower is better.

But what will help a lot is , a extra cooling fan on top of the extruder motor, then no heat reaches the gears, or other parts, on thingiverse you can find this, blow the air to the top of the enclosure.

A extra cooling fan for enclosure, you could look for temp triggered sensor, for in a computer, if you make this then you could also combine the extra power supply with the fan on the extruder.

If you buy all in 5 volt (fans)then you could use a phone charger.

There also should be small temp sensors to run the fans.

Posted : 03/08/2020 10:00 am
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