Feed tube keeps popping out

[raymie 0]

Finally got the platform all set, roughly 0.1mm from the print head, prints start fine but the feed tube pops out from the clip near the print head now. Any ideas on how to stop this and improve on the design of this component (without needing to print a part!)?

[mastory 44]

I just so happen to have the same problem, and I have a couple ideas. The first of which I have the parts on hand to make the repair if I decide to go forward with it.

I went digging in my box of misc plumbing stuff. I found some brass compression fittings that are normally used for connecting a 1/4" water line to a fridge ice maker. There are 3 pcs to the fitting; a nut that goes on the tube prior to connection, then there is a ferule that presses into the tubing, and the threaded piece that he tube is being connected to. My interest right now is the ferule. It has a ID of .135", OD of .165" and is about .66" long with a flute at one end.

like this: http://www.alibaba.com/product-gs/448245319/Brass_Tube_Insert_Sleeve_brass_compression.html

The filament slides right thru it.

I am considering silver soldering the fluted end to the top end of the famous brass tube. The ferules OD should make a very tight press fit into the Bowden tube. The ferule is long enough to pass thru and be clamped by the little white bushing. Since the OD of the bowden tube will be increased with the ferule inside, it should grip much better in the plastic bushing.

The silver solder will make a very strong connection and will not melt below 450C.

My concerns; What will happen to the bowden tube when the ferrule conducts heat into the first 5/8" of the tubing? I don't yet know if the increased diameter will fit in the white bushing.

What material is the bowden tube is made of?

What do you guys think?

Matt

[joergen 2]

I just so happen to have the same problem, and I have a couple ideas. The first of which I have the parts on hand to make the repair if I decide to go forward with it.

I went digging in my box of misc plumbing stuff. I found some brass compression fittings that are normally used for connecting a 1/4" water line to a fridge ice maker. There are 3 pcs to the fitting; a nut that goes on the tube prior to connection, then there is a ferule that presses into the tubing, and the threaded piece that he tube is being connected to. My interest right now is the ferule. It has a ID of .135", OD of .165" and is about .66" long with a flute at one end.

like this: http://www.alibaba.com/product-gs/448245319/Brass_Tube_Insert_Sleeve_brass_compression.html

The filament slides right thru it.

I am considering silver soldering the fluted end to the top end of the famous brass tube. The ferules OD should make a very tight press fit into the Bowden tube. The ferule is long enough to pass thru and be clamped by the little white bushing. Since the OD of the bowden tube will be increased with the ferule inside, it should grip much better in the plastic bushing.The silver solder will make a very strong connection and will not melt below 450C.My concerns; What will happen to the bowden tube when the ferrule conducts heat into the first 5/8" of the tubing? I don't yet know if the increased diameter will fit in the white bushing.

What material is the bowden tube is made of?

What do you guys think?

I think that there are already 3-4 good solutions for this problem outlined in the forum and in the google group, and I would start reading those first: print the owen bowden clamp, use a 1/4in compression fitting (upper part of the head), thread the peek with a M7, or in the extreme case, thread the bowden directly to the alu (see my multi-color post), etc etc.

The bowden is made of PTFT or PFA, with a similar heat resistance as the peek (>250C).

as a hint, the white ring in the lower part of the head is clearly a one way (metal teeth biting into the bowden), do not try to push it upwards, rather go all the way through, and re-insert it from the top again.

[joergen 2]

Finally got the platform all set, roughly 0.1mm from the print head, prints start fine but the feed tube pops out from the clip near the print head now. Any ideas on how to stop this and improve on the design of this component (without needing to print a part!)?

onve you get your head reassembled, make sure that your print temp is proper: if your temp is too low, the plastic doesn't really melt in the nozzle, and the bowden will pop again. find your extrusion temp first (180-240C, the UM TC isn't always reporting the right temp)

[raymie 0]

For the moment I have I think solved this and only using the parts that come with the UM.

I took a drill with a countersink bit and drilled a countersink groove onto the bottom part of the hole in the top of the print end where the tube comes out and then used the second of the white retaining clips on that hole (so that both clips are on the tube).

When drilling the grrove I made it so that the end of the clips only partially came out of the top (i.e. not enough to get the blue clip attached.

This way I can just about push the tube through the top (with a fair bit of force) and so for the tube to come free againi it would need enough force to free itself from both the bottom ring and the new top one, chance are that extrusion gear would be more likely to jam first.

I did consider compression fitting but if you are going to use these on a plastic pipe you really should be using a inset as well to stop the olive compressing the pipe and that seemed like too much bother over using the white clip already provided. Not sure why UM provide two and then don't make sure of the second one, would just need the countersink holes to be added to the upper part as they already have for the bottom one.

[raymie 0]

and after a day of trying to print something it popped out again. Starting to wonder however is this is to do with the print and not just the machine given the force needed to move the pipe.

Next time I rebuild the head I will try the same again but go back to the thin wall print samples first to see if that works.