Bowden tube comes loose in mid-print

[FalmouthLouis 3]

I've been doing some 10 hour prints on a UM2, using a .8mm nozzle and printing layers of .2mm. Jobs have failed twice with the bowden tube becoming disconnected from the print head, with the result that filament has just been pushed through into empty space. I've been printing for 3 years and this is the first time this has ever happened to me. The tube was fed into the print core in the normal way, with the little blue clip holding the white bit up and seeming locking the tube in place. Before the second print, I specifically checked the tube and I confirmed that it could not be pulled out. I'm also pretty sure that it had been pushed right down. Certainly, there had been no problems when I reloaded filament at the stat of the job. I was checking these jobs about every four hours, so I did not pick up any advance notice that this was going to happen.

 

So what on earth might have caused the bowden tube to pull out of the print core in the middle of printing something which should just have involved continuous printing? Could it be something to do with the volume of filament that I was printing - wide nozzle, thick layers? I was using one of the 3D infill patterns, so might they be posing issues? It's a machine which I've had for three years, and I can't remember if I've ever changed the Bowden tube so, might the age of the tube be an issue?

[gr5 2,210]

Every time you remove the bowden it tends to get worse.  But don't let that discourage you from removing it.  The fix is easy.  Inside the collet (that ring that holds the bowden in place) are 4 tiny metal blades.  They can scrape the outer surface of the bowden.  It's not obvious, the bowden may look fine.  Anyway...

 

Remove the bowden and look in the collet to make sure the 4 blades are still there (one may have broken off) and make sure they look the same.  Assuming the collet is fine (it usually is) cut off about 4mm from the end of the bowden.  This way when you insert the bowden back in the blades will get a grip on a fresh location of the bowden.  That's it.  Fixed.

[FalmouthLouis 3]

gr5 - that's very helpful. I never thought about how the collet actually worked. I shall look for those blades tomorrow.

 

 

[Gibba66 0]

gr5 - I have this same problem but it keeps happening, I’ve gotten different collets and tubes but it still keeps happening. What should I do?

[gr5 2,210]

What kind of printer do you have?  I saw something recently...  I'll go look it up.  I think it applied to certain Ultimaker printers?

[gr5 2,210]

Oh!  I see you have an UM3.  How old is it?

 

[lrodriguez 32]

You either have a stripped tube or worn collet. You can trim a few mm’s of the tube for now. This could also be a good time to replace it and pickup a new collet. It’s a yearly suggested replacement per the maintenance schedule. The tube, not the collet.

[gr5 2,210]

6 hours ago, Gibba66 said:

I’ve gotten different collets and tubes

Oops.  Somehow I missed this part.  Can you take the collet out and send a photograph of the blades in the collet?  There are 4 blades - like razor blades.  Curved to the shape of the bowden.

 

So when reinstalling a collet it is good to push down on the tube and the collet.  Then while still pushing down on the bowden tube with one hand, lift the collet with the other.  Then lift the tube and it should hold the collet up.  While the collet is up, slide the clip under.

 

I have to tell you that I've never had this problem (bowden slipping out a lot).  Well I had it a few times on my UMO but not the later machines that I own (UM2, UM3, S5).

[gr5 2,210]

Once a bowden has slipped out once or twice you really need to cut a few mm off the end so it has a fresh spot of bowden to grip with the blades.

[SandervG 1,521]

A lot of good advice here. Perhaps a summary would be helpful. If your bowden tube pops out of the collet do the following: 

- Push down the collet and pull out the bowden tube. See if there are any significant scrape marks on the sides. 

- Remove the collet from the socket and inspect the insides. Do you see 4 equal (small) blades in there? 

 

If the collet does not 4 equal blades you should contact your reseller for a replacement. If your bowden tube has significant scratches on its surface and your collet still has 4 blades, then you can try to cut off ~4mm of the bowden tube so the blades can grip a new and fresh part. Keep in mind: 

- Do not do this too often. When a bowden tube gets too short there will be other problems concerning the filament passing inside.

- If you decide to cut it, cut it straight. If the bottom is not flat there can also be extrusion issues over time where the filament can expand due to heat and pressure in that small area where it is not touching. 

 

It is not a bad idea to replace them once a year or so to ensure all is in good condition. Check out the maintenance schedule for your printer for more information on this topic.

[AddMan 2]

Hi Guys,

 

This has happened twice now in the last two days on my new S5. In my case its at the extruder end. If I cut a small piece off at this end I lose the bevelled edge. Will this affect the filament feeding into the bowden?

[Maxiforja 0]

On 7/7/2020 at 5:08 AM, SandervG said:

A lot of good advice here. Perhaps a summary would be helpful. If your bowden tube pops out of the collet do the following: 

- Push down the collet and pull out the bowden tube. See if there are any significant scrape marks on the sides. 

- Remove the collet from the socket and inspect the insides. Do you see 4 equal (small) blades in there? 

 

If the collet does not 4 equal blades you should contact your reseller for a replacement. If your bowden tube has significant scratches on its surface and your collet still has 4 blades, then you can try to cut off ~4mm of the bowden tube so the blades can grip a new and fresh part. Keep in mind: 

- Do not do this too often. When a bowden tube gets too short there will be other problems concerning the filament passing inside.

- If you decide to cut it, cut it straight. If the bottom is not flat there can also be extrusion issues over time where the filament can expand due to heat and pressure in that small area where it is not touching. 

 

It is not a bad idea to replace them once a year or so to ensure all is in good condition. Check out the maintenance schedule for your printer for more information on this topic.

I had this issue today, and your post was really helpful!

But, since this is a known issue that seems to affect many users, couldn't Ultimaker implement some kind of sensor just before the print core to check for material flux?

If the bowden tube slips on a Friday night, the printer will be a mess on Monday morning, and the initial part of the print will be lost.

It would be great if the printer just stopped itself when this happens, just like it does when the material spool is empty.

[gr5 2,210]

It's actually pretty rare.  I think.  I have 5 active Ultimaker printers all with the same type of bowden material and same clips and have not had any slips in probably 7 years.

 

Although as far as I'm concerned, the more sensors the better!!!

 

[GoguyT3d 8]

For me the blades on the collet were fine but I noticed significant wear(chew marks) where it was before and I ended up cutting 10mm off which is juuuuust above where it chews for grip. I also noticed on the piece of tubing I cut off of the official ultimaker bowden, there is a chamfer (on the extruder end) on the inside diameter of the tubing probably for easy filament insertion, so on my newly cut piece i used a chamfer drill bit to make it the same profile. I've included some pictures of the super chew and the chamfer on the origial bowden.

[dlesser71n 0]

Great idea on the chamfer. Anything that minimizes the "magic" inside the "not so detailed oriented" tension mechanism, as you did above, helps tremendously with metallic / brick PLA.

 

Thank you again,

[Torgeir 250]

Hi @GoguyT3d,

 

Yes this is the way we do it, right the chamfer is to make it easier to install the filament.

If you buy a new bowden tube, the chamfer end is marked with tape.

 

Thanks

Torgeir

 

Don't know what happen here, I was replaying another post that's gone now.. 🤔

Edited May 15, 2023 by Torgeir
New Text

[mbhsict 7]

https://support.makerbot.com/s/article/1667412704648#:~:text=UltiMaker has investigated the root,force on the Bowden tube.

print off the upgraded clips, had our bowden tubes pop out a few times over 4 printers and not once since printing off the thicker clips

[BrettSneider1 0]

Always good to replace bowden tubes once every 3 months or so. These printers need maintenance just like anything else. Poly-tetra-flouro-etyhylene teflon bowden tube are durable and thermally resistant but wear and tear takes place when user takes it in and out of print head and feeder coupling. Chamfer end does go on print head side. Should order extra tubes and clips or print your own clips. Collets could be printed but these things are so cheap worth just buying extras for good parts