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Extruder slipping?  

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Thiscord
(@thiscord)
Active Member
Extruder slipping?

Hi everyone,

I've been having all kinds of issues with my Prusa MINI recently. I think I've resolved most of them by changing the PTFE tube (cutting it a bit shorter) and raising the heatbreak as far up as I could.

What's happening now are some occasional black-outs in extrusion. I don't want to call it under-extrusion because there's no extrusion happening whatsoever. And then it suddenly starts working again. I suspect it may be due to the extruder cogwheels slipping. Why do I think so? It failed to load the filament all the way a couple of times and one time when there was no extrusion happening I pulled it out and it wasn't fully in either.

Has anyone encountered this? Could it be that I added lubricant to the extruder cogwheels?
Cheers

Posted : 03/07/2021 1:56 pm
Diem
 Diem
(@diem)
Noble Member
RE: Extruder slipping?

Have you tried adjusting the screw on the extruder idler?

Cheerio,

Posted : 03/07/2021 5:02 pm
Thiscord
(@thiscord)
Active Member
Topic starter answered:
RE: Extruder slipping?

@diem

I've tried that. Unfortunately, made no difference.

In addition to what I've described, I've also taken the extruder assembly apart, cleaned the extruder clogwheels from the gumming as well as the lubricant. This game me one perfect first layer test but when I started priting again the issue came back after a couple of minutes. I'm at a loss now...

Posted : 03/07/2021 5:12 pm
Thiscord
(@thiscord)
Active Member
Topic starter answered:
RE: Extruder slipping?

This is what it looks like when printing now. Sometimes it looks fine but it always goes wrong.

Posted : 03/07/2021 5:23 pm
Diem
 Diem
(@diem)
Noble Member
RE: Extruder slipping?

Could it be that I added lubricant to the extruder cogwheels?

I wonder.  What did you use?

A tiny dab of lithium grease is advised.  Oil is too mobile and when warm it may spread to the gripping surface and wick into the housing where is becomes a reservoir of trouble.

cleaned the extruder clogwheels from the gumming as well as the lubricant.

Grinding in the extruder usually produces dust, not gum.  If there was enough lubricant to pick up the dust and mix it to a paste then you will need to do some serious degreasing... not just the part but anywhere it might have migrated.

If this doesn't lead to a fix it's time to contact Prusa Support.  Log into your Eshop account, navigate to support and live chat is at bottom right in most browsers. If not you may need to disable your ad-blocker temporarily.

Cheerio,

Posted : 04/07/2021 8:44 am
Thiscord
(@thiscord)
Active Member
Topic starter answered:
RE: Extruder slipping?
Posted by: @diem

Could it be that I added lubricant to the extruder cogwheels?

I wonder.  What did you use?

I used the lubricant that came with the printer. Where exactly would you apply the lubricant?

Perhaps, gumming was not the right word. There was a very fine dust in the grooves just like show in this picture

The thing is, this was been there for a while without causing any issues.
The whole chain of problems started with me getting some clicking in the extruder and filament getting chewed up which was causing underextrusion. I did a couple of cold pulls, cleaned the nozzle, exchanged the PETG tube and that seemed to have solved the clicking.
But then I started getting underextrusion without clicking. So pushed the heatbreak up. This seemed to have helped a bit now it's come back. Sometimes there's no extrusion at all, sometimes it's just fine and other times it's partial.

I'll try degreasing the whole extruder like you said.

Posted : 04/07/2021 9:15 am
karl-herbert
(@karl-herbert)
Illustrious Member
RE: Extruder slipping?
Posted by: @thiscord

Hi everyone,

I've been having all kinds of issues with my Prusa MINI recently. I think I've resolved most of them by changing the PTFE tube (cutting it a bit shorter) and raising the heatbreak as far up as I could.

What's happening now are some occasional black-outs in extrusion. I don't want to call it under-extrusion because there's no extrusion happening whatsoever. And then it suddenly starts working again. I suspect it may be due to the extruder cogwheels slipping. Why do I think so? It failed to load the filament all the way a couple of times and one time when there was no extrusion happening I pulled it out and it wasn't fully in either.

Has anyone encountered this? Could it be that I added lubricant to the extruder cogwheels?  
Cheers

It has also happened that Prusa forgot to install the spring in the extruder. Have you ever checked this?

https://forum.prusaprinters.org/forum/hardware-firmware-and-software-help/what-is-a-good-tension-for-the-prusa-mini-feeder/

wbr,

Karl

Statt zu klagen, dass wir nicht alles haben, was wir wollen, sollten wir lieber dankbar sein, dass wir nicht alles bekommen, was wir verdienen....
Posted : 04/07/2021 10:51 am
Diem
 Diem
(@diem)
Noble Member
RE: Extruder slipping?

Where exactly would you apply the lubricant?

Where metal engages metal.  A minute dab every year is enough.

Cheerio,

Posted : 04/07/2021 6:02 pm
Thiscord
(@thiscord)
Active Member
Topic starter answered:
RE: Extruder slipping?

@karl-herbert

Thank you but luckily the part is there

@Diem
Thank you!

Having observed the printer a bit more it really seems that it's having trouble pushing the filament through the PTFE tube towards to hotend. The problem is, I've reassembled and fixed this part twice already. I don't know what else I could do to it. Perhaps it was a mistake to cut a piece off the PTFE tube (to make it flush just like in the guide).

Posted : 04/07/2021 7:05 pm
karl-herbert
(@karl-herbert)
Illustrious Member
RE: Extruder slipping?

@thiscord

The fault may be in the area of the crimp connections (pressed olive part). If these are tightened too much, the diameter of the PTFE tube is compressed and blocks the filament. Maybe you replace these parts or you expand the PTFE inner diameter in the clamping area with a 2mm drilling tool.

good luck!

 

Statt zu klagen, dass wir nicht alles haben, was wir wollen, sollten wir lieber dankbar sein, dass wir nicht alles bekommen, was wir verdienen....
Posted : 04/07/2021 8:18 pm
Diem
 Diem
(@diem)
Noble Member
RE: Extruder slipping?

Perhaps it was a mistake to cut a piece off the PTFE tube (to make it flush just like in the guide).

Oops I wasn't paying attention.  Do you mean you cut the hotend PTFE tube?  The length is critical; if this is the case you will need a replacement.

https://help.prusa3d.com/en/guide/how-to-replace-a-hotend-ptfe-tube-mini-mini_119449

Cheerio,

 

Posted : 05/07/2021 12:41 am
Thiscord
(@thiscord)
Active Member
Topic starter answered:
RE: Extruder slipping?

@Diem

I did exactly the same thing as this guy here
I guess it may have been a mistake. I've orderer some replacement tubes. I'll keep you updated. Thanks!

@karl-herbert

Thanks for the tip! I'll first try replacing the PTFE tube and if that doesn't help, I'll give this a try. Thanks!

Posted : 05/07/2021 7:52 am
Thiscord
(@thiscord)
Active Member
Topic starter answered:
RE: Extruder slipping?

So I've finally received my replacement hotend PTFE tubes and replaced it as instructed here https://help.prusa3d.com/en/guide/how-to-replace-a-hotend-ptfe-tube-mini-mini_119449/

Now I'm back to my original problem though. There's some serious clicking coming from the extruder and I'm getting massive underextrusion.

I ran into the same problem as last time. The PTFE tube is simply too long to be pushed down so far as to be flush with the the rims of the hole like this . Or at least now while having the heatbreak pushed all the way up (which is why I cut it short last time). It's one or the other. So I'm guessing the underextrusion happens due to the heatbreak being too low. But to do now?

Posted : 09/07/2021 4:28 pm
Diem
 Diem
(@diem)
Noble Member
RE: Extruder slipping?

If you have altered the assembly so the tube no longer fits you might find it helps to review the assembly process.  Take a look at: https://help.prusa3d.com/en/guide/how-to-replace-a-heaterblock-heatbreak-mini-mini_122769   step 11 onwards.

Cheerio,

Posted : 09/07/2021 5:17 pm
Thiscord
(@thiscord)
Active Member
Topic starter answered:
RE: Extruder slipping?

@diem

So I did that but the problem persists. There's nothing no issues in the heatbreak assembly. I guess the PTFE tube is simply too long. When I push the heaterblock all the way up as it should be like this:

 

I'll end up with the PTFE tube sticking like this.

Then screwing the fitting on will simply push the heaterblock down as there's no space left to go. Have the dimensions changed between models or something? Or it may be time to contact prusa support.

Posted : 10/07/2021 1:32 pm
Diem
 Diem
(@diem)
Noble Member
RE: Extruder slipping?

Yes, this is one for Support.  Have these pictures ready to upload (or refer them to this thread) and have a camera to hand then:

Log into your Eshop account, navigate to support and live chat is at bottom right in most browsers. If not you may need to disable your ad-blocker temporarily.

Cheerio,

Posted : 10/07/2021 2:49 pm
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