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Almost always missing layers / underextruding

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Posted · Almost always missing layers / underextruding

I believe this proves the theory, in my case anyway. I printed this with retraction turned off, (a wing from my little Dragon) and it is the smoothest print I've ever had, not a hint of under extrusion.

 

wing 01

wing 02

wing 03

wing 04

 

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Posted · Almost always missing layers / underextruding

Yes! Now let's try to get that bowden tube shoved down the teflon interface piece. You must get your printer up to snuff, I want to see what you end up printing with a properly functional UM2.

 

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Posted · Almost always missing layers / underextruding

Hey guys, thanks for the diagnosis.

I took a trip to the filament trashcan and found some of those tips that were cut off when changing filament.

filament end02

filament end01

I think I might have the same issue as braddock, albeit not that extreme. Regarding the bowden tube play, do you mean the whole bowden tube with the white ring at the top of the head? If yes, than I have about 1-2mm play when I pull on it. A the bottom, right above the teflon piece, I see the bowden tube moving up and down:

 

By the way, the long orange filament strand was attached to the tip that I cut off. I thought, one of these days this thing will get stuck inside the extruder, right above the knurled bolt and when I push new filament in it will move inside the head and definitely cause a clog...

 

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Posted · Almost always missing layers / underextruding

Definitely the same issue! Try a test with no retraction also, I think you'll find your under extrusion vanishes.

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Posted · Almost always missing layers / underextruding

Yeah! :smile: add this to the list of troubleshooting techniques; save the swapped out tips and examine their shape for mushrooming.

 

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Posted · Almost always missing layers / underextruding

I had similar, but not quite as severe, play like Nicolinux shows in the video when I first got the machine. After I got my first clog and disassembled the head I did what I describe above and now my play is maybe half a mm. My clog was due to contaminants though, not because of this play.

I guess a couple of years of fiddling with the original UM had some benefit after all heh.

 

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Posted · Almost always missing layers / underextruding

Just as a point of reference... my bowden tube and clip assembly at the hot end have about 1.5mm of play - and always has. It's hard to see down at the end of the bowden tube where it goes into the white coupler, because of the spring, but it seems that the tube does move at that point, but perhaps less than 1.5mm - probably because of a little tension in the tube between those two points. Certainly the bowden tube isn't coming out of the coupler as a result of the movement.

Under the coupler, the gap between the metal part and the coupler is 2.5mm on my printer.

I did notice that the top of the spring at the coupler/tube junction was covered in white powder - ground down bowden, I guess?

But it's still working perfectly, so I'm not about to pull any of it out and start analyzing it :-)

So... I think that the problem is probably to do with the seating of the bowden and the coupler somehow allowing soft filament to expand into a space where it shouldn't. Having the bowden move isn't ideal, but clearly there's some degree of movement that's acceptable before it causes a problem.

 

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Posted · Almost always missing layers / underextruding

Damn, I was about to ask you how your bowden tube behaves, and this isn't the answer I hoped for :)

The gap under the coupler, between the metal part and the coupler is at 1.2mm on mine. So maybe there isn't enough tension to keep the bowden tube in place.

 

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Posted · Almost always missing layers / underextruding

It would be interesting to see the tips from a filament change, if you have one illuminari.

 

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Posted · Almost always missing layers / underextruding

the other issue is material unspooling, if ever you actually hear the filament untangling as it unspools, there's a chance it's requiring enough force to cause under extrusion.

I think these two issues are the cause of 95% of my troubles, initially I was falsely diagnosing it as a blocked nozzle.

 

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Posted · Almost always missing layers / underextruding

I did the same thing - pulled up hard on the bowden. The ring held up by the red clip moves up and down a bit - I've noticed it before and was thinking of printing a thicker clip to replace the red clip. I measured it just now and with a strong pull (maybe 5 to 10 pounds force) it moves less than 1mm. About .5 to .8mm.

Looking down at the spring area I see nothing happening there. I looked from different angles. And through those holes in the metal. Nothing is visibly moving. The bowden is probably going up and down but you can't tell because it isn't dirty or scratched enough to see movement.

 

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Posted · Almost always missing layers / underextruding

And in this image that sander posted my gap is 2.2mm:

 

Print head Ultimaker 2

 

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Posted · Almost always missing layers / underextruding

Sander corrected himself later on that thread though regarding that gap.

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Posted · Almost always missing layers / underextruding

My Bowden tube is still coming out, any suggestions on how to keep it there? This is a really silly problem to be having, days and days of wasted time and frustration due to a poorly designed fitting.

 

 

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Posted · Almost always missing layers / underextruding

Sander's correction was that it had to be more than 1mm (not less). And 2mm is probably better.

 

any suggestions on how to keep it there?

 

This is a common problem. There are 2 very common causes. Either the tube is defective or the "fitting".

Take the tube out and look inside the fitting. There should be metal blades inside. They can get bent backwards so that they no longer work or can fall out or break. If the blades all look fine and are symmetrical then the problem is with the tube. If the"fitting" is defective you need a new one. I have no idea where to get new ones other than through UM: support.ultimaker.com

bad tube: One of the times the tube was removed (either by you or by pressure) the tube got a thin layer scraped off. If you look at the tube very carefully you might see that it is thinner or different where the blades "bite" into it.

Anyway if the tube is "bad" it's very easy to fix. Just cut off 5 to 10mm from the end and now the blades will bite into the bowden tube higher up where it isn't damaged yet. Of course you can only do this a few times before you will need a new bowden.

Or maybe I misunderstand. Maybe nothing is wrong with the bowden nor the fitting. Maybe you just didn't assemble it "tight" enough per Robert's directions (earlier in this thread post #43). I'm not sure 3 or 4 turns is tight enough though - maybe more like 6 but I don't know as I haven't taken this apart myself.

 

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Posted · Almost always missing layers / underextruding

I've assembled it a bunch of times, each time making sure it's pushed into the teflon part as far as it will go.

The teeth on the clip / fitting all look ok, though very small, the clip just doesn't seem to be up to the task.

My tube is definitely scraped on the sides though, due to pulling apart so many times.

I wonder if some teflon tape around the tube might help?

 

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Posted · Almost always missing layers / underextruding

@braddock: I don't know if this is such a good idea. If pieces of the teflon tape get inside the bowden tube, you'l get another clog/plug for sure.

 

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Posted · Almost always missing layers / underextruding

Just cut 5mm off the end of the tube so that the blades cut in to fresh virgin bowden tube.

 

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Posted · Almost always missing layers / underextruding

I just meant putting the tape around the outside of the tube where the collet clamp is, nowhere near the hotend / tube end.

gr5 - It also has scrapes from removing the black clips that hold the cable netting and bowden tube together, but I might give that a go.

The actual collet just looks like a generic part you should be able to find in a plumbing store, I'd like to know where UM source them from.

 

@braddock: I don't know if this is such a good idea. If pieces of the teflon tape get inside the bowden tube, you'l get another clog/plug for sure.

 

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Posted · Almost always missing layers / underextruding

The actual collet just looks like a generic part you should be able to find in a plumbing store

 

I believe they are specialty. Used in air conditioner low pressure water lines only. Very very specific application and although the tube is common the different types of "fittings" are varied and only one, rare one, is the correct one.

I looked on mcmaster carr and couldn't find it. If it's not on mcmaster carr then it's damn hard to get. Although it may have been there but just difficult to find.

You can probably get them at a plumbing supply place that deals with plumbers that deal with commercial air conditioning. But not at a typical hardware store.

 

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Posted · Almost always missing layers / underextruding

Yeah - I think I found those. But those aren't the same as on the extruder or head, right?

 

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Posted · Almost always missing layers / underextruding

Those are the ones that are on the UM1... on the 2 I'm not sure - maybe one of the 'drill and install' install types? (plus the c-clip).

 

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Posted · Almost always missing layers / underextruding

I thinking some kind of mod / hack is needed. It's too common a problem not to be addressed by a better solution. A drill style mechanical collet would be a better design.

 

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Posted · Almost always missing layers / underextruding

Well mine have never slipped. But I've also never taken out the bowden on either machine because I'm afraid of damaging it.

 

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