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gael

Very high Friction in the Bowden tube

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Hello all,

I am in trouble with my machine. My problem is the following.

The friction in the bowden tube is very high. Then the extruder motor has difficulties to push the filament. Then, most of the availlable torque is wasted in friction instead of creating the pressure to extrude properly. pushing the filament by hand down to the head is very difficult....

As the friction is very high, I have to tighten a lot the filament to keep it moving in the bowden which adds small indentations to the filament that increases even more the friction. (I had to upgrade the extruder into a Geo Hagen style extruder to get enough grip)

Aside from that, The printing head gets stuck all the time altough I never can see any PLA plug when I dissasemble it...

I start to be a bit desesperate on this last point....

Any idea or advice?

Gaël

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How thick is your filament? And it is round or oval? The compression from the drive might make it even more oval which results in getting it stuck in the tube.

Hi Daid,

I will check that this evening....

Anyhow, does everybody accept that a few tens of mm variability in the filament diameter or circularity can jam the machine?

Gaël

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I've printed with filament that varied by 0.3mm. it gave lousy prints but it didn't jam anything.

good filament shouldn't vary by more than 0.05mm (ideally less).

I think Daid's point is that if the thumbwheel is too tight you will deform the filament which may cause problems. however i've never managed to do that by hand.

I heard of someone who had a bowden tube with a slightly mangled end on it which caught on the filament as it went into the hot end - they pulled it out, cut it square and suddenly everything was great again. but that doesn't necessarily mean any of these are your problem..

is your filament Ultimaker silver by any chance? ;)

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The best thing is to measure your filament (both along and perpendicular to the spool axis) with (digital) calipers. It's possible that one of these values is too large - it shouldn't be more than 2.90mm. At 3.00mm or over you will get a large amount of friction in the bowden tube, causing problems like the one you're having right now.

I don't think you could deform filament to an oval to this point without thinking twice about the force you're putting on the screw. You will know that you're forcing it then.

What do you mean by 'the printing head is getting stuck'? Does the extruder grind on the filament? Maybe you're overextruding (slightly), causing pressure in the filament and giving the feeling of a plugged hot-end. This is most noticeable in large filled areas (like the first layer of a big print) - but first i'd check your filament diameter. If it is in fact too big you'll also be overextruding (because you push more volume of plastic per extruder step).

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Hello all,

I measured my filament and its diameter is 3.0mm. In theory, it should be ok if I believe what is written about filament tolerance on the Ultimaker's consumables shop. (2.8-3.1mm)

When I say that the head gets blocked, I mean that even when pushing very hard the filament using a plier, I don't get anything coming out of the nozzle.

I disassembled several times the head, cleaned any trace of PLA with solvent and put everything back together with the small improvements mentionned in the "jamming" page.

I switched back to a silver filament bought from Ultimaker (2.75mm diameter) and the friction in the bowden became very reasonable and the head did not get blocked during several hours of printing.

So you were right, my filament was too big. I think that the horseshoe holder reduces locally the inner diameter of the bowden tube just enough so that a 3mm filament with a bit of indentation from the knurled driver gets stuck there. This added to the high level of friction in the bowden prevents any extrusion...

I will have to dispose of my spools of 3mm PLA filament and gets some 2.75mm filament from Ultimaker....

Thanks for your advice!!!

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I will have to dispose of my spools of 3mm PLA filament and gets some 2.75mm filament from Ultimaker....

Not sure how much 3mm you have, but if it's a lot then it might be interesting to find another solution.

I know they had some bad filament at Protospace, and they needed a solution. So they used something called a "trekijzer" in dutch:

http://www.dezilverwinkel.nl/trekijzer3 ... p-794.html

Normal sold 3mm filament is actually around 2.9mm. However, some new sellers don't know this custom and thus make 3mm filament around 3.0mm

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Hi Daid,

I bought my filament from Paoparts. I have 4 rolls of 1.5kg (one red, one transparent, one blue and one white) I only unpacked the white one....

But I also though is might be interesting to design a "filament calibrator" to adjust filament diameter and circularity to optimal values...

I'll have a look at the "trekijzer"...

Thanks for the tip!

++

Gaël

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A couple of things I have found:

- It is possible to have enough compression to make the filament oval if you tighten up the thumb screw when the filament starts to strip because the tightening mechanism moves in to take up some of the carved out space in filament. When the filament moves past that point, the compression goes up.

- A solution that I have found is to use a larger ID on the Bowden tube. McMaster Carr sells 1/4 inch PFA tubing with a 5/32 inch inside diameter. This allows for a larger diameter filament to go through the Bowden tube. The only thing would be if the filament gets caught on the inside edge of the brass tube. I just reamed out (very carefully) the end of the brass tube to a slightly larger diameter. Make sure that there is no plastic in the hot end before removing any brass though, or the brass filings could plug up the nozzle.

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Hi.

I just found a piece of PTFE tubing. outer diameter is 6mm and Inner is 4mm. It tested it up to 300°C with a soldering iron. It seems to withstand the temp.

I made a test by hand with my 3.0mm indented filament and the force required to push is through is very low. I have to find out how to reliably hold it in place on my UM.

I think I'll print Owen's Bowden clamp for that...

++

Gaël

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Hi.

I just found a piece of PTFE tubing. outer diameter is 6mm and Inner is 4mm. It tested it up to 300°C with a soldering iron. It seems to withstand the temp.

I made a test by hand with my 3.0mm indented filament and the force required to push is through is very low. I have to find out how to reliably hold it in place on my UM.

I think I'll print Owen's Bowden clamp for that...

++

Gaël

I would love to see that!

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Hello all,

I replaced the original bowden tube with a new one. The inner diameter is bigger (4.0mm instead of 3.2mm). Then a filament indented by the knurled bolt doesn't produce a big friction in the tube. Before, I had to force a lot on the filament to load in on the machine. Now I just have to lightly push with the filament between the thumb and the index.

https://picasaweb.google.com/1128421795 ... May272012#

Another problem with the original tube is the horseshoe clamp. it strangles a bit the tube to hold it and then its inner diameter is reduced by a few tenth of millimeter. This increases a lot the pressure required to extrude the filament. this high pressure and the proximity of the horseshoe clamp with the heating section of the print head makes the filament expand between the horseshoe clamp and the printhead that makes the jamming.

With the new tube, a small reduction of the inner diameter does not block the filament anymore. Or at least the friction became very reasonable.

As the tube is thinner, it was necessary to add to the UM Owen's tube clamp to prevent it to move.

Now it seems to work fine and I can print with the indented 3.0mm filament...

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Hi (again)

I added the following post on this topic : viewtopic.php?f=21&t=932&p=5451#p5451

It's related to excessive pressure on the filament and back pressure leading to failed prints:

From what I observed, when you print large areas completeley filed, the output of the filament is restricted by the short distance between the nozzle and the printed flat surface. A back-pressure grows in the heated section of the printing head that makes the filament bulge just above the heated section. The resulting friction of the filament against the inside of the bowden tube slows down the extrusion that may stall and make fail the print...

You can first reduce this back pressure by leveling perfectly the machines table. This way you'll prevent the nozzle to get too close from the support that leads to a excessive back-pressure.

Using a thinner filament (<2.9mm) also helps to push back the moment the extrusion will get stuck.

You can do something to diagnose the problem: When you see the extrusion stalling, let the machine run and manually pull the filament out. you will be able to see the section of filament that bulged a blocked the extrusion.

Filament_stucked_annotated2.jpg

On this image, you can see the indentations that increase the friction in the bowden tube, the restriction in diameter from the horseshoe clamp that increase also the friction and the bulge of the filament just above the metling section that also inceases the friction on the filament.

All this causing the printing to fail...

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Hi all,

I'm also having problems with the friction in the bowden tube.

There is a lot of friction if I manually push in the filament, and after about 20 cm, it becomes impossible to push it in further.

This is the case with 6 out of 7 different plastic filament I tried, including the silver-grey filament that was supplied with the ultimaker.

The only one that worked was transparent blue filament, but even that one required quite a bit of force.

This is with a brand new ultimaker I just constructed this weekend.

Perhaps the bowden tubes supplied with new ultimakers are bad?

I'm now also looking to get some new PTFE tubing with a bigger inner diameter. Where did you find yours?

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I just finished my Ultimaker and in the process of tuning the plastic feed, it stopped feeding at all. The feeder ground into the side of the filament, and as reported here I could barely push it by hand.

When I first got it working, I had to tighten the thumbwheel with what felt like a lot of force, or it would not feed. Now after printing only four objects (3 test 2mm cubes and a whistle) it stopped feeding 1/3 of the way into another 2mm test cube. It just chews into the filament.

Does the PTFE tubing stay in the stock fittings? If not, what did you use?

Edit: I'm using Cura, and this is the version of the feeder that is an allen head bolt.

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Hi!

You got the same kind of problem as I had.

You have a lot of friction in the tube, so you tighten more the feeder, so you get more indentation to the filament, so you get even more friction...

Have you measured the diameter of your filament? It seems that this problem is less noticeable with smaller filaments.

To solve the problem, I used this tubing:

http://www.factorydirect.fr/tube-air-comprime-calibre-en-ptfe-diam-4-6-couronne-25m-blanc-279.php

It allows a smooth extrusion with indented 3.0mm filament.

Yesterday I noticed that Cura's retraction function that prevents stringing (by inverting feeder's rotation) works much better since the filament can move freely inside the tube.

++

Gaël

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I've been following this thread with interest, as I've been running into similar problems.

I've been thinking about doing something similar but using parts found in North America (save me a bit of cash on shipping & duty). I found a tube at McMasters that looks interesting:

http://www.mcmaster.com/#pfa-tubing/=hrc6gt

One of them is the 5/32" ID and 1/4" OD. Which is ~3.9mm inside and ~6.4mm outside for $4.33 per foot.

The other is in the metric side, 4mm ID and 6mm OD. Cheaper too at $3.15 per foot.

Are either of these fine to use, do you think?

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One of them is the 5/32" ID and 1/4" OD. Which is ~3.9mm inside and ~6.4mm outside for $4.33 per foot.

The other is in the metric side, 4mm ID and 6mm OD. Cheaper too at $3.15 per foot.

Are either of these fine to use, do you think?

Hi!

The metric one looks identical to the one I used.

The other one looks good to me regarding the inner diameter.

I would just check that the outer diameter is compatible with the feeder's quick-fit coupling.

++

Gaël

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http://www.mcmaster.com/#pfa-tubing/=hrc6gt

One of them is the 5/32" ID and 1/4" OD. Which is ~3.9mm inside and ~6.4mm outside for $4.33 per foot.

The other is in the metric side, 4mm ID and 6mm OD. Cheaper too at $3.15 per foot.

 

Thanks, I am going to order some of this. I think I'm also going to try printing the Thingiverse mod to the Bowden pressure plate that adds a ball bearing where it presses on the filament.

http://www.thingiverse.com/thing:21674

I had forgotten to mention that my filament is the 3.0mm (actually about 2.70mm) white that came with my Ultimaker.

I was -very- impressed with the finish on the side of the test cube just before it stopped feeding.

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I ordered a few types just in case:

1 4 ft. 5733K54 Crack-Resistant Tubing Made w/ Teflon® ® PFA Metric, 4mm ID, 6mm OD, 1mm Wall Thickness, Clear today $3.15 ft. 12.60

2 4 ft. 5239K12 Extreme-Temp Tubing Made with Teflon® PTFE 3/16" ID, 1/4" OD, 1/32" Wall, Semi-Clear White today $1.69 ft. 6.76

3 4 ft. 52335K34 Metric Extreme-Temp Tubing Made with PTFE 4 mm ID, 6 mm OD, 1 mm Wall, Semi-Clear White today $2.48 ft. 9.92

The PTFE specified that it has a very smooth finish inside, so I thought I'd try it, too.

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I'm hoping I don't get a nasty surprise, McMaster-Carr does not tell you me what the shipping will be.

I also ordered two ball bearings, 10-6-3 for the feeder upgrade. So I've got an extra. I ordered four feet of each the three tubing. I'm not sure how long the Bowden tube must be as I'm not home now to measure it. What I'm getting at is that I'd be happy to help you once I get the tubing and bearings.

Later I think I might build this upgrade to the feeder. I like the increased contact area of the MakerBot driver:

http://www.thingiverse.com/thing:19551

Of course, the key is to make another one right after the first one is working, so as to avoid the dilemna I'm in now where I cannot make a part I need in order to make the part I need.

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I'm not sure how long the Bowden tube must be as I'm not home now to measure it. What I'm getting at is that I'd be happy to help you once I get the tubing and bearings.
I think the tube is 80mm in length. So 4 feet should work.

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