Berend's and Owen's Hot End Mod works great!

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Bradley

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Feb 29, 2012, 2:22:05 PM2/29/12
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As new improvements for higher resolution printing have come out (software slicers, fan ducts designs, etc), I too have tried them out to push the envelope of quality UM prints.   However, with every advance, there seemed to be one new plaguing problem introduced, simple because the printer was working harder to do something spectacular.

The last plaguing problem I was faced with was accumulated back-pressure from the hot end, causing the bowden tube to eventually release from its capture fitting, causing molten filament to harden in the gap between the shifted bowden tube and the brass pipe, eventually causing filament output to stop.   Once that happened, the hot end needed to be disassembled, the clog removed and the hot end reassembled and primed.   

This happened again and again on challenging prints, making using the machine an unpleasant and unsatisfying experience on many levels.   Owen had obviously experienced a similar problem and designed/developed his bowden clamp (http://www.thingiverse.com/thing:11864).   I carefully printed and installed his modification and, for a while, printing resumed without issue -- the bowden clamp did it's job at battling back pressure.

So I was fearlessly printing more and more difficult objects with both higher resolution and higher speed.   However, it seems, nothing good lasts forever, and so the back pressure eventually became strong enough to sheer Owen's clamp design in two during a print.   Foiled again.  This time I was really disappointed and, as a result, the machine sat dormant for a long time.

A few weeks later, I decided to catch up on the goings-on of the UM community on UM's new (non-google) forum.   There I was surprised to find this thread started by Berend: http://forum.ultimaker.com/viewtopic.php?f=6&t=184&p=1062&hilit=peek#p738 .    It contained an idea that was simple, elegant and logical.    I was also pleased to see that Owen (one of my favorite UM mods designers), had also noticed the thread and had also decided to try his own rendition of Berend's proposed modification.   Best of all, both these guys claimed that it, for now, had solved, for them, the same print issue I, too, was having.

I decided to design slightly different rendition of the modification (requiring little new parts/purchases -- using what I already had) and implement it.   Well...since implementing it a few days ago, I've been having great success, so I figured I'd post my thoughts so that others can benefit from this fairly simple mod.

Here it is in a nutshell:    Add a thread to the extruder hot end of the bowden tube, such that it threads in the peek insulator (sharing the same threads with the brass tube).   That's it.   See what I mean by simple and elegant?

For the bowden to share the threads of the peek with the brass tube, you need to make some room for the bowden in the peek threads.   To do that, you disassemble the hot end, removing the peek adapter and cutting the brass tube so it only extends 5-6mm above the aluminum heat block. I simply sheared down the brass tube using a dremel -- without even disassembling it from the heat block.  Then I reassembled the peek to the brass tube.   

To put the proper threads (6x1mm) on the bowden, take a 6x1mm thread die and cut about 8mm length of thread onto the extruder hot end of the bowden tube.  This is easily, quickly and carefully done by hand.   

Finally, screw the newly threaded bowden into the top part of the peek until it is snug (which means it is making full contact with the top of the shortened brass tube.    Reassemble the hot end and start printing.  It's that simple.

To make this modification more maintainable, it is suggested by both Owen and me to cut a short section of bowden off the extruder hot end of the tube, such that when it is screwed into the peek and assembled into the extruder wood housing, it protrudes about 10mm out of the very top hole of the extruder wood housing (i.e., the hole used in the original bowden arrangement).   To connect the shortened bowden section with the remaining longer bowden tube, simply use Owen's bowden clamp on top of the extruder housing.    The longer bowden goes into the clamp and mates with the shorter tube, allowing the filament to easily cross between the two tube sections.   In this same arrangement the bowden clamp with the longer tube provides an extra hold down on the shorter tube, preventing it from unscrewing/shifting.    By doing this mod with the two-piece bowden/clamp setup, you can easily disassemble the whole thing if you need to do any maintenance.

As an added benefit, this modification an extremely easy and clog-free way to swap between filament colors with very little reserve filament left in the hot end.

Below I've added some pictures of the my modification.      Try it, you'll like it!


Shortened Brass Tube.


Bowden with new 6x1mm threads


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


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

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





Sverre Svenningsen

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Feb 29, 2012, 5:44:27 PM2/29/12
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Nice mod! I'd be very worried that there's a new weak point since the short brass tube only has a few mm of PEEK thread to hold onto, enough pressure might shear the PEEK threads? And it's a permanent modification to metal parts so measure thrice, cut once i guess :)

Maybe if the threaded bowden setup gets popular, someone can manufacture a new PEEK part that has threads all the way up and include a pre-tapped short length of teflon tube to sit inside the carriage? That would be helpful for people that have bowdens that already too short, too!

-Sverre

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Bradley

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Mar 1, 2012, 10:40:54 AM3/1/12
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On Wednesday, February 29, 2012 5:44:27 PM UTC-5, error1 wrote:
Nice mod! I'd be very worried that there's a new weak point since the short brass tube only has a few mm of PEEK thread to hold onto, enough pressure might shear the PEEK threads?
 
No worry about the strength of the peek threads -- it's not the point of least resistance -- the bowden clamp will still release way before the peek does.
 
And it's a permanent modification to metal parts so measure thrice, cut once i guess :)
 
 
Yes, if you're not good with tools and measuring -- I advise you to not try this mod
 
 
Maybe if the threaded bowden setup gets popular, someone can manufacture a new PEEK part that has threads all the way up and include a pre-tapped short length of teflon tube to sit inside the carriage? That would be helpful for people that have bowdens that already too short, too!
 
Yes, that's what I'm hoping UM or someone else does.
 

William

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Mar 1, 2012, 6:46:12 PM3/1/12
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I agree it really is a pain when the bowden pops out. I also have the owen mod, but its not enough(my theory still being: mount it right the first time and NEVER move it).

I have seen some mention of this treading-the-bowden in previous posts, but this seems a bit dramatic. Cutting the brass parts is serious business, you do it wrong, and the UM stays on the shelf for a long time.

Why not thread the bowden from the inside, and make it fit the brass(possibly making the PEEK hole 5mm deeper. I havnt tried this yet, but maybe i should.

Other to the threading-business: you cut it manually with the Xacto knife? Surely there mudt be a better way?

- william

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WilliamKempton

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Mar 2, 2012, 9:21:39 AM3/2/12
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Ok, i am ready to give this a try.

But to do this i need some more info about making the thread. where do i get this " 6x1mm thread die" , and what does it look like?

Also, you only thread the bowden, not the PEEK?

- William

Jelle Boomstra

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Mar 2, 2012, 9:26:45 AM3/2/12
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if you live in a metric country, a M3,4,6,8 tap and die set should not be hard to come by. Otherwise, you should try a little harder, I guess?



- William

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Bradley

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Mar 2, 2012, 10:15:59 AM3/2/12
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Here's an inexpensive example: http://www.amazon.com/gp/product/B000OBF01Y
 
 

On Friday, March 2, 2012 9:26:45 AM UTC-5, Jelle Boomstra wrote:
if you live in a metric country, a M3,4,6,8 tap and die set should not be hard to come by. Otherwise, you should try a little harder, I guess?

On Fri, Mar 2, 2012 at 3:21 PM, WilliamKempton <wil...@kempton.no> wrote:
Ok, i am ready to give this a try.

But to do this i need some more info about making the thread. where do i get this " 6x1mm thread die" , and what does it look like?

Also, you only thread the bowden, not the PEEK?


- William

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Dave Head

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Mar 2, 2012, 10:20:03 AM3/2/12
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hey that yoke is cool

sorry easily impressed 

WilliamKempton

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Mar 2, 2012, 11:03:41 AM3/2/12
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bought this baby for 18euros at the local hardware store. Of course 1 piece costs 12 euros, so why not the whole pack for 18.

I will try this mod now, hoping for more durable results.

- William

Joergen Geerds

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Mar 2, 2012, 2:19:43 PM3/2/12
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On Friday, March 2, 2012 11:03:41 AM UTC-5, WilliamKempton wrote:


bought this baby for 18euros at the local hardware store. Of course 1 piece costs 12 euros, so why not the whole pack for 18.

virtually identical to this set:

WilliamKempton

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Mar 4, 2012, 7:23:51 AM3/4/12
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Ok, so I cut down the brass like mentioned on this post (added a picture to clarify to those who want to try), and threaded the bowden cable.

And its was:

Success!

This is a great mod. I have only had this for a day now, but no problems so far. I strongly recommend anyone who has had problems with their bowden cables popping off, to do as this thread recommends.

- william

3DTOPO

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Aug 20, 2012, 6:39:31 AM8/20/12
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I am seriously considering this mod. Can anyone provide an update? Is it still working without clogs? Thanks!

(Sorry for bringing this thread back to life, but an update would be great!)

Scott Mayson

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Aug 20, 2012, 7:27:55 AM8/20/12
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I would be cautious about shortening the heater barrel as this will allow less surface area for heating PLA or ABS and reduce room for transition from "glass to melt point" and could force molten material back up into the bowden tube if your UM is left at temp for a too long a time?

On commercial machines the heater barrel for 1.75mm fillament is >80mm in length and capable of printing Ultum etc. We have some Fortus machines and I have analysed the heater barrels http://www.flickr.com/photos/scottmayson/6791884597/in/photostream BTW they are interchangable as they also block-up! maybe the open source industry needs to move to cheep swapable printer heads?

Best
Scott

Boman33

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Aug 20, 2012, 8:49:50 AM8/20/12
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Thanks Scott for the picture.

Do you have any pictures or info on the heater block and its mounting?

 

Did you see the throw-away extruder on the Mojo printer?  See my mini-review at:

http://www.vinland.com/blog/?p=114

Bertho

Berend

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Aug 20, 2012, 10:40:28 AM8/20/12
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All,

I used this threaded bowden mod for quite a while but on the long run it failed.
The thread (on the tube side) exhibited some wear, witch caused clogging again.
Maybe it has to do with the quality of the PFTE tube in the hot end, dunno.

It is less elegant but works great as long as i use it.
If this solution fails i think of making a combination of these two: pushing the bowden to the PEEK by screwing but with the thread in the cold part of the extruder.
I see the exactly 8mm cut off as the weak part because it is very critical and not adjustable. I think that adjustment with screwing is the solution.

Grtz,
Berend

OwenB

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Aug 20, 2012, 4:32:13 PM8/20/12
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This has been working still for me but with a slight mod due to a non-smooth passage of the filament.
I still have the short riser piece screwed into the hot end.
I have a nut threaded onto the Bowden tube and use my Bowden Clamp to hold this down rather than have the Bowden Clamp squeezing on the tube.
The nut gives an adjustment to make the two tubes meet while being able to do the Bowden Clamp up tight.
Let me know if you want me to do a drawing.
I never get plugs though occasionally it stops extruding though this hasn't been happening since I have the V3 bolt.
I have been doing a 40+ hour print lately with no problems.
I haven't achieved good retraction yet, though looking at a recent video from Florian it looks like my extruder is spinning too fast.
I'm not sure if the shortened brass tube would be good for retraction. I think a smooth passage for the filament should help.

Owen

Scott Mayson

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Aug 20, 2012, 9:51:39 PM8/20/12
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@Bertho

Here is an image of the inside of a Fortus 900 http://www.flickr.com/photos/scottmayson/6631482093/in/photostream

Scott

Boman33

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Aug 20, 2012, 10:21:28 PM8/20/12
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Thanks Scott,

Do you know why they have the big washer at the end of the tube?

It appears to be floating in air and not touching the heater or the heater block,

Bertho

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