All-metal extruders

Just fishing for any advice or knowledge any of you may have regarding extruders. It is the weak point in many printers and the one thing that drives me nuts on any of mine. I recently helped a friend finish a Mendel Prusa he was building and had to make one of those MBE extruders work with it. The firmware is the first challenge but I finally got it figured out with a lot of searching of this site and others, but the thing only did one print before the drive pulley came loose and it's a half hour job to repair every time that happens. I'd hate to have it do it halfway through a larger printing job.The extruder is nicely made but a flawed design relying on the end of a set screw to press the filament against the hobbed pulley. It really needs a bearing on the end of the grub screw and some users have tried polishing the end of the grub screw to make it work but it needs to be tight to make the filament grip yet loose so that the filament will pass by.
Anyway like I say it is nicely made but a crap design.
So the original reason for this post, are there any other all-metal designs out there that work?

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Richmond, New Zealand
Thingiverse ~ YouTube

Do you really mean extruders Simon, or are you really talking about the hot end?
It seems to me from peoples feedback that (as you have experienced) there is no totally reliable all metal hotend or any other for that matter!
My current setup is really a hybrid of metal, ptfe and a fibrous restriction tube. It works for me. Anyway, I have never bought an Extruder/ hotend - all metal or otherwise because I have yet to see any that performs any better than what I can make at home. Maybe the future of 3D will have to go with completely different technology? Who knows.

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Waitaki 3D Printer

The whole thing. When I saw the MBE one MBE Extruder I was initially impressed, it is a very nice object. I have since found a few others including this overpriced one on kickstarter: Kickstarter which looks like a good unit but is too expensive I feel. I've been using a variety of ones I've modified from the Wade including this version I made last year Thingiverse but they all have their limitations and being plastic they eventually wear out and clog up.
Edit: This looks good: Printrbot

Edited 1 time(s). Last edit at 12/31/2013 03:31PM by Wired1.

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Richmond, New Zealand
Thingiverse ~ YouTube

Quote
Wired1
(snip!)
Edit: This looks good: Printrbot

It is, indeed, good. Simple, robust, easy to clean, easy to see what you're doing when loading filament, very easy to swap out hotends (less fiddly than changing nozzles).

Downsides:

A little clumsy pushing down lever, easily remedied with this:

[www.thingiverse.com]

Conducts heat from stepper motor, making use of PLA problematic (no problems thus far with ABS). Also easily remedied with something like this:

[www.thingiverse.com]

Hi Simon You may be interested in a “direct drive extruder” I designed recently and fitted to my OB1.4 printer. The design uses your original “OBXcarry20” part. There is a small 11mm dia x 5mm dia x 4mm wide bearing to push the 1.75mm filament directly against a 8mm hobbed driver from “MAKERshop”. The filament goes directly through the middle of the toggle lever. One of the advantages of the design is that it almost retains your original X,Y,Z sizes and it certainly works well.
Enclosed are a few photo’s and a 3D PDF file showing the complete assembly. With this file it’s possible to rotate and view all components individually and to turn them on/off as required.