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joergen

Bowden connection: simple M7 thread?

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I was thinking about the complexities of the Bowden hot end connection, and wanted to see if the following has been tried and/or failed:

It is super easy to give the Bowden tube a M7 thread. I tested it with a scrap piece of Pla, cutting a M7 thread into it. The connection seems very solid, given the additional thread surface, without any pinching of the inner tube diameter.

So, in theory, wouldn't it be easier to simply take a piece of PEEK with a M6 and a M7 thread, and screw the Bowden into the PEEK? This would cut down the complexity while using less space, and make servicing the hot end easier... In addition, it should be easy to machine a Y configuration to allow for strange new configurations. Maybe it's even possible to feed 1.75mm filament through a proper Bowden (small adaptor screw to fit into the PEEK), and not worry about the filament being a bit loose in the 3mm brass barrel.

Opinions?

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Common sense suggests me that this has indeed been tried already, we do have a set of taps and dies here. But you have not tried any of the two materials involved: PFA and PEEK, did you?

The move from telfon (PFTE) to PFA was later in the development, and it is a bit stiffer than PFTE, so it might just work. The PEEK is something that should be gotten rid off as it is hard to source. A setup with a longer stainless tube instead of the brass that can be screwed into an alu heatsink is much more preferable. The ultimaker is not aimed at the gada price, so it is not on a silly energy budget. The extra losses from a heatsink do not weigh up to the simpler construction without PEEK.

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Common sense suggests me that this has indeed been tried already, we do have a set of taps and dies here. But you have not tried any of the two materials involved: PFA and PEEK, did you?

I do not know if it has been tried before, I had hoped that somebody from UM would occasionally read their own forum... :-(

 

The move from telfon (PFTE) to PFA was later in the development, and it is a bit stiffer than PFTE, so it might just work.

I agree, I don't think there is a large fundamental difference between the PTFT and the PFA, I think both should be easy to thread... I just happen to have 5m of PTFT, since my original tube got way to short in my uneducated and panic-stricken first 2 weeks of UM ownership. (If anybody in the NYC region needs some PTFT tubing, let me know.)

 

The PEEK is something that should be gotten rid off as it is hard to source. A setup with a longer stainless tube instead of the brass that can be screwed into an alu heatsink is much more preferable. The ultimaker is not aimed at the gada price, so it is not on a silly energy budget. The extra losses from a heatsink do not weigh up to the simpler construction without PEEK.

I agree, the PEEK is a somehow difficult item, that even as a rod (a 1.6cm rod costs about $1/cm, but there is usually a 30cm min order), which needs to be machined/lathed... but the PEEK offers another benefit: a lower k-value than metal, and mechanical stability. I do assume that it can be machined with metal tools like a thread cutter, but I haven't tried it yet (due to the lack to PEEK in my apartment. I'll think about a construction that doesn't stray from the original parts too much...

(see my other post at http://forum.ultimaker.com/viewtopic.php?f=6&t=206)

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All,

In my opinion the hot-end 'bowden-peek-brass interface' not the most serviceable part of the UM.

Inspired by your idea, I picked up an older project I did some months ago despite my hot-end was working fine.

- I tapped thread in a teflon hose so it can be screwed (?) inside the Peek and there it meets the brass tube.

- The other end of the threaded teflon I connected to the bowden tube with a printed interface (funnel on bowden side and thread on teflon side)

- The bowden is pushed in the funnel by Owen's :

http://www.thingiverse.com/thing:11864

(what a piece of art is this, perfect)

I know that nobody can understand the above told story so i added some pictures. (sorry for the sizes)

The first test i printed (an easy one) was perfect, second test is running OK at this moment, so i don't know how reliable it is on the long term or with difficult prints.

To be continued,

Berend

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Gooday Berend/All

I also carried out your mod but slightly different.

I cut the top of the threaded brass rod so 6mm was poking out above the heater block.

Ran a 6mm tap right through the Peek part.

Screwed a short piece of Teflon tube threaded with a 6mm die just long enough to go into Peek and meet the top of the brass threaded rod.

This piece of tube extended 11mm above the top piece of wood and into the bowden clamp (http://www.thingiverse.com/thing:11864).

I then put the regular bowden tube through the top of the bowden clamp to meet the top of the short tube.

I then tightened up the bowden clamp.

An added bonus is I've gotten some length added back to the bowden tube (after having cut the end off a few times).

I haven't done enough printing with it yet to determine how good it is though.

I don't think this is the ultimate solution but the good thing is the Bowden tube mating is a bit less dependent on the 4 main screws of the wooden parts and you don't need to get the 8mm out the end just right etc.

Please excuse my shoddy iPhone photos.

IMC DMM video EM3-YouTube sharing.mov

Ultimaker 2 Press Kit.zip

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I did a similar mod to Owen's. Mine is working great without clogging, however I did find on prints with large filled downskins, filament backpressure will still build up and pop the bowden out of the Owen's clamp. If I loosen the tension on the extruder drive clamp, when pressure builds up enough, the filament slips somewhat, but the bowden clamp holds.

I hope that the Ultimaker folks are taking note of our modification experiments and are working towards a better designed bowden interface to the hot end.

Here's my posting on the Google groups: http://groups.google.com/group/ultimaker/browse_thread/thread/706e9777955b6e96

Here are some pictures of my mod:

Shortened Brass Tube:

IMG_0008.JPG

Bowden with new 6x1mm threads:

IMG_0003.JPG

Testing fit and depth of the threaded bowden into the peek isolator:

IMG_0006.JPG

Testing assembly of the bowden to brass mating within the peek insulator:

IMG_0007.JPG

Final assembly -- can you tell anything's changed on the bowden? :

photo.JPG

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I did a similar mod to Owen's. Mine is working great without clogging, however I did find on prints with large filled downskins, filament back pressure will still build up and pop the bowden out of the Owen's clamp. If I loosen the tension on the extruder drive clamp, when pressure builds up enough, the filament slips somewhat, but the bowden clamp holds.

 

Gooday Brad

I had mine pop initially too and found I had to tighten up the Bowden Clamp a bit tighter to the limit of what it can handle probably.

I have still been having a very good run with it and have basically just been printing stuff lately and not mucking around with my machine anymore.

One small issue I get quite often when changing filament is if the filament has a slight lump in it when I retract it, it gets stuck at the bowden clamp and I need to undo the clamp and snip the end of the filament off there.

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Follow-up from my mod post. I've been using this mod for several weeks and have completely eliminated the hot end clogging issue. Thus, threading the bowden into the peek works!

I still had an issue with unthreaded portion of the bowden popping out of the bowden clamp, so I replaced the clamp with a connector similar to the one that is on the extruder drive-side of the bowden. So far, works PERFECTLY!

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Follow-up from my mod post. I've been using this mod for several weeks and have completely eliminated the hot end clogging issue. Thus, threading the bowden into the peek works!

I still had an issue with unthreaded portion of the bowden popping out of the bowden clamp, so I replaced the clamp with a connector similar to the one that is on the extruder drive-side of the bowden. So far, works PERFECTLY!

That's great Brad, I've had a fantastic run with mine too. No more plugs since I've done it and the Nozzle height remains the same irrespective of tightening of the bolts etc. I do find I have to do my Bowden clamp up very tight or it pops. The only issue I have now is when I change filament that I have to undo the Bowden clamp and cut the blob off the end of the old filament to pull it back out. It's a fairly quick and easy process but I'd rather not have to do it. I think if I pulled it back at the right speed or set the temp right I might be able to avoid it. I've been thinking lately about getting rid of the Bowden Clamp altogether and seeing if just the thread on the end of the Bowden tube would hold on it's own. It would mean that to remove it from the hot end I would have to undo it at the cold end first. It wouldn't be an issue as it hardly ever needs to be done anymore anyway. Only problem is the other tube I have has a smaller diameter than the original so I'm not sure if it will be too tight.

btw how do you go when you swap your filament? Does it get stuck at the junction between the two tubes?

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btw how do you go when you swap your filament? Does it get stuck at the junction between the two tubes?

Nope. Just pull straight out/away.

That's great Brad. Sounds like it would be better than having my clamp on, especially as it would be shorter too I'd imagine.

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Hi Owen,

I'm using your bowden tube holder too and I think the main solution it provides is keeping stable the tube in the printing head while avoiding any unwanted movement while it moves on the platform.

My question is: is there any reason you didn't include a support for the electronics to fit in another place?

As of now they're just screwed in one point for my assembly. Is it the same for yours?

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Not a problem indeed but sometimes it look a bit fragile.

I'll see if I can design an accessory to attach to your build so that I can fix it with both the screws on it :)

Will keep you posted on that :)

No worries Antiklesys, I'll be looking out for it.

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I've done a similar mod. I cut the brass tube by 5.7mm and squared the end by filing the edge against the face of an M6 die. (my machinist friends would be horrified by how I treat my tools). I threaded a new piece of tubing M6 x 8mm lg. Pretty hard to get the die started, I had to turn down the OD from .25" to 6mm first. If you have the tubing in a lathe, make sure you tweak the plastic to run out true or else the ID might be off center and cause problems. Assemble the hot end leaving the threaded rods abit loose. Thread in the bowden tube through the top hole and into the PEEK block as tight as you can manage by hand. Tighten up the threaded rods while keeping the heat sink square. Burn fingers. Massage the bend of the tube towards the extruder if the natural bend doesn't point that way. Insert extruder end into extruder bowden clamp and refeed.

So far so good, even without an Owen's clamp. I've not had any plugs, and when I need to remove the filament it comes out easy with a low 160 preheat.

Thank you guys for the great idea!

Kyle

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Hi,

I mostly like the clamp Owen designed because it keep the tube fixed between the top of the moving part and the hot end. I noticed that otherwise the tube tend to flex a week bit while the hot end moves during a print. I found that this reduces a lot of the stress which is put on the pla and I'm extruding nicely almost all the time. I'm now upgrading my feeder mechanism a bit too but that's another story :)

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Inspired by the ideas in this thread I have taken it a slightly different direction. I have put the M7 thread on the *inside* of the PTFE tube so that the brass tube threads into it. I have also flipped the bottom wooden plate which reverses the direction that the bowden tube is being cinched. I have placed a large spring between the heater block and the aluminum heat spreader. There is some heat transferred from the heater block to the spreader, but it is not too much since it must travel through the narrow spring, but I intend to further reduce it by adding a silicone gasket or two at the ends of the spring.

R7Cq8.jpg

Best thing about this design is that it eliminates the need for the PEEK part. This also simplifies dismantling and re-assembling the hot end such as when changing nozzles. Worst thing about this design is that the heater block does not sit flush and level by default, and the position of the spring must be manually adjusted to get it centred. Ideally there would be a recess cut for the spring to sit in at either end.

I am still field testing this, no saying how it will work in the long run.

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You have put a M6 thread on the inside of the bowden, not a M7 (since the bowden disappears when you use a M7 tap)...

it's a cool design, although I wonder about wobble/jerk/general inertia when the head moves at higher speeds, and the spring is only emphasizing it.... please tell us if you see extra bumps on the corners from the wobble.

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wow awesome! Your spring idea makes me think it would work well for leveling multiple extruder heads! Just pull the bowden up/down to get the nozzles at the same height. I too am wondering though how stiff is that spring? does it pull the head up when you go to the front left corner/ allow the head to go down when you are at back right?

If the spring actually works it might mean great news for multiple extruder ultimakers, you could even set up a servo to pull the print head up when not in use and then back down for printing...

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You have put a M6 thread on the inside of the bowden, not a M7 (since the bowden disappears when you use a M7 tap)...

it's a cool design, although I wonder about wobble/jerk/general inertia when the head moves at higher speeds, and the spring is only emphasizing it.... please tell us if you see extra bumps on the corners from the wobble.

Thanks for the tip, it works much better with an M6 thread. Preliminary testing has shown no noticeable difference from sudden changes in direction, my corners are still nice and sharp and I have cranked up Jerk and Acceleration.

The spring is quite stiff, in fact maybe too stiff - when I tried to compress the spring too much the heated bowden tube stretched and broke from the pressure :(. I believe a shorter spring with less tension would be better. Also one thing I didn't test is the rapid back and forth movement you sometimes get, it shakes the printhead by default so I'm thinking it might cause the spring to resonate at certain frequencies. One other problem I encountered was some minor slippage of the spring against the heater block. The first part I printed could be seen to have a slight "wave", although it seemed to have settled into place after that. If the head was to catch on a high bit of plastic or resonate too much it might set the spring to slipping. If the spring had a proper seat that could be prevented, or else maybe some high temperature solder, or maybe even spot welded into place...

I am going to try some revisions, I will update when I have something more solid.

PS my bowden tube is slowly getting shorter and shorter from my modifications - time to source a new one..

 

does it pull the head up when you go to the front left corner/ allow the head to go down when you are at back right?

It does not affect any of that..

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