Hi,
Your a frequent poster and reader, I see.
So when you've checked all your temps and feeder bla bla...
I would give this part a try.
https://www.youmagine.com/designs/dual-bowden-clamp
Not my own design! :shock:
Just uploaded as a set to try and save some frustrations with other dual experimenters.
Will work for a single extr. aswell
Broken link, my friend 
oeps..
edited.... I've changed the title afterwards..
I'm having the same problem, and have even printed the improved nozzle clamp as referenced above. I did add a heated bed to the mix which meant I used a firmware compiler that I found on the forum here. The reason I bring it up is that I wonder if there is some mismatch in the parameter of filament feed/ to the actual depositing volume which after maybe 5-10 minutes builds up such force to pop the tube out from the clamp? I even tried to reinforce a volume of the clamp with a piece of paper around the tube and can indeed lift the ultimaker from the tube when I start up.
Need help!
My UM weighs about 15 pounds but the front half weighs about 5 and the back half about 10. So if the print head is near the front of the UM and you only lift the front part you are only pulling 5 pounds. Can you completely lift off the table?
The feeder should be able to pull about 22 pounds before it grinds the filament instead of moving it.
So if it can completely lift the UM off the table, that's pretty good but not as good as it should be.
What temp and speed and layer height are you printing at?
I'm having the same problem, and have even printed the improved nozzle clamp as referenced above. I did add a heated bed to the mix which meant I used a firmware compiler that I found on the forum here. The reason I bring it up is that I wonder if there is some mismatch in the parameter of filament feed/ to the actual depositing volume which after maybe 5-10 minutes builds up such force to pop the tube out from the clamp? I even tried to reinforce a volume of the clamp with a piece of paper around the tube and can indeed lift the ultimaker from the tube when I start up.
Need help!
Hi Fabbers,
Are you using dual extrusion?
This cone clamp keeps my tube's in place now. But I had problems after a few layers, running dual extrusion, because the 16mm standard retraction was to much for one nozzle.
Have to look in to it, but I think the none extruded filament cooled down in gap somewhere between the brass tube and the nozzle. Resulting in the Bowden tube pops out, or grinding in the feeder.
Setting the dual switch retraction to 12mm solved that problem.
Well I am having this problem again specifically with the silver PLA
After a few prints with the blue PLA (2.8mm), I wanted to use the silver PLA again for a few prints (2.9mm) No sooner had I loaded it into the machine, the bowden tube popped off the print head (teflon tube). The blue piece was still attached up top, so that's not doing anything :(
I know Barnacules made a piece to deal with this...
...but I know Sander had some worries about diameter of the clamp and heat.
Any other ideas?
Indeed, I have 
How does the surface of the bowden tube look like?
In the white tightner are 4 tiny knives holding the bowden tube at its place.
If you frequently have this problem, there is a very good chance either the 'knives' are bent/broken or just scraped the surface of the bowden tube so now they can't hold the bowden tube no more.
The blue piece is there to make sure the white tightner is 'locked/secured'. But if there is a problem with the little knives inside, that is kinda like locking an open door..
I never had this problem either, but on rare occasions one of the machines in the office has its tube popping.
Make sure you are not printing too hot compared to the speed you are printing at.
When you print too hot, you have a high chance of a plug forming > bowden tube popping.
I have my doubts about that add on, as it implements pressure on the tube. To me that sounds like you have a high chance of deforming the tube or making the inner diameter smaller, causing friction, leading into under extrusion.
(perhaps even friction > pressure > higher chance of bowden tube popping.)
I'm printing at 215 to 220 C on my prints.
Is the Bowden tube a specific tube itself? Could I replace this with something found at a hardware store?
I don't see any marks on the tube on the teflon end or where it is clamped into place with the blue piece.
Alternatively, can a clamp like that used to control the movement from the extruder be used on this end?
I know Barnacules made a piece to deal with this...
...but I know Sander had some worries about diameter of the clamp and heat.
I'm using this for monthes now. The 'knives' had started to scrape the surface of the bowden tube, and then it will fail inevitably, sooner or later. Once it starts (not careful when pulling it out, and your done) it will weaken the surface further, speeding up the process.
It did not work out of the box, cohesion was too low despite the screw and the cone. I added a small piece of sanding paper, now it sticks. It sticks so perfect, that I probably will have to destroy the part should I ever want to remove it :roll:
Diameter reduction because of the pressure does not seem to be a problem, one filament has a diameter of 3.03 and prints fine as all others. I think the reduction is minimal because it is hard to reduce the diameter if a tube if you apply symmetric radial pressure.
Another idea I read about was to construct something about a part like this which cuts slightly into the tube:
I'm a little frustrated this keeps happening to me. I wish there was a better fix
this keeps happening to me.
Sorry man. Next time it pops off try the sandpaper trick.
I'm a little frustrated this keeps happening to me. I wish there was a better fix
@LePaul, have you actually tried one of the cone like clamps yet? (can't find it in your posts).
Using it for almost a year now and it's one reason less to throw prints in the trash.
And a lot easier to get the bowden tube out again, you don't end up with a to short tube (because of cutting the ends clean again to give it another try)
And as said somewhere above, it's almost impossible to turn the nut to tight and cause more friction.
@MatEngi, considered to give it a try with a FlexPla cone? Next Flex Pla run I will try some soft cones, should give more friction I guess.....
I have no soft PLA yet. If yes, I'll give it a try. For fallback reasons I made one of these:
http://www.thingiverse.com/thing:87775
I think it would be better to get to the bottom of this problem. Like Sander said - few machines have it.
@LePaul: You have a rev. 4 Ultimaker like mine. I never ever experienced this problem so if we both followed the same build instructions, we should have fairly similar printers.
I suggest you try to find a simple object where the popping happens every time. Then print it with different settings and see if helps. Maybe you are doing something fundamentally wrong with your prints (like printing way too fast at 220° so the pressure builds up). Or maybe there is indeed a partial clog somewhere.
Heat up to 240° and rotate the extruder (slowly) by hand. You shouldn't feel much resistance. If you do and there is a clog, maybe you can get away with this "trick". Heat up to 260° and extrude by hand a bit faster. If you then feel a difference in the resistance, you might have just pushed out the blocker.
And another idea. Heat up to the normal temperature where you switch filament and pull it out. Then remove the small blue clip from the bowden tube (near the head not the extruder). Now you can lift the bowden tube a bit, just enough to take alook inside the hole where the bowden tube enters the head. There might be loose strands of filament.
This could happen when you pull out filament and it forms thin strands of plastic that remain in the bowden tube. The next time you push new filament in, the thin strands will be compressed and pushed into the head and might partially block the entry or make it harder for the filament to pass through.
I don't think I have a blockage but it doesn't hurt to check...but what I am noticing is that the blue collar piece doesn't seem to really do anything. I haven't had a chance to mess with the machine much this week, with school finals and several Halloween/Charity events with my R2-D2 replica
As mentioned earlier, I'm not convinced the white collar piece has a good "grip" and wonder if I should resemble the other end, where I have applied the shim? For example, see this pic
Note how the top of the clamp is lifted upwards. Should this be how it looks on the other end above the print head?
If so, I can try shimming it some more and make that will give me the hold I need
The way the two ends of the bowden are held down are apparently different but I don't quite understand it myself. But on the print head you definitely need the clip but not on the extruder (although it helps with accurate retraction).
I am told that there are tiny metal knives inside the part on the print head that help hold the bowden in. When removing the bowden from the print head you have to hold down the outer ring (which means the blue clip must be removed).
Sometimes, even though you hold down the outer ring I suspect the tiny knives don't retract enough so when you remove the bowden you get two possible issues:
1) you scrape a thin layer off the outside of the bowden making it weaker and smaller and harder to grip next time.
2) sometimes the scrapings land inside the print head and the next time you print you get clogs. Hopefully they almost always miss the print head and blow away but someone on these forums reported this issue recently.
If #1 is your problem then you should probably print up one of the many bowden tube holder designs mentioned up above. Reread all the great answers up above. I particularly like the one with the huge plastic tightener bolt shown way up above as no one seems to have trouble with those even though Sander is skeptical.
Sorry I haven't been as active here as I wanted to be. Work, Halloween, charity work...but anyways, I am back!
The situation I am in is I can't really print (reliably) and solutions at the moment! I mean, as an alternative, I can CNC something out of aluminum on the machine I have access too.
Hey LePaul, you asked about this problem also in respons to my post in 'Fixing Pulley Accuracy' and by chance I just saw the picture of your printhead in this topic. I told you that I never had any problems with the bowden popping out but now I see that you have this black plastic thing screwed on the head. My UM came without this black thing so my white insert is just directly inserted in the wood. I guess this black part is an 'upgrade' on later UM's to prevent the bowden from comming out but maybe you should try remove it. Then insert the white insert in the wood and try printing.
Hope this helps!
Interestingly, on my UM2 I have just noticed this only happens with the silver PLA.
Interestingly, on my UM2 I have just noticed this only happens with the silver PLA.
Wait - what? What? You have a bowden popping off a UM2???? I haven't heard of that before. I thought the extruder was too weak. If you pull real hard how much force does it take? The UM Original feeder can push 22 pounds of force so obviously the bowden should be MUCH stronger than that. You should be able to pick up the machine by the bowden - either end. At least I can on my UM Original - just tried it. The UM2 might be heavier.
OK making sure we are talking of the same thing. I mean the plastic tube that runs into the print head. I notice when ever I use the silver, the plastic tube pulls back and you can see the PLA exposed just above the head. Once the print has finished I push this back in place.
OK edit - Just spotted the same occurs with the Blue. As far as I can tell, the only issue is when replacing the PLA, I have to make sure that the tube is seated correctly as this can cause some issues with the feed.
Once the tube is re seated, I am unable to pull this away, it seems this occurs when the print starts or rather the PLA gets retracted.
Is this something that I need to be concerned about?
Oh. I don't know what that is. It looks like it *might* be a problem. Sorry I don't have a UM2. Yet.
The Bowden tube is the long, clear tube that runs from the feeder to the head. I don't know how far down into the head it goes. But maybe it goes all the way into your picture?? I don't know.
Could you take a picture of the top of the print head also? I want to see if you are missing the little blue clip.
Bowden tube is a mechanical term. Other examples are the tubes that contain bicycle brake cables, bicycle gear shift cables, automobile speedometer cables.
ArunC posted a topic in UltiMaker Cura,
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gr5 2,167
I'm not familiar with this issue although many other people are. I suggest you google these forums and the google groups. In fact, just use google. Perhaps "ultimaker bowden tube pops off".
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