Tuesday, July 25, 2006


Mk2a RepRap Polymer Extruder Head

I've just finished assembling the current generation of polymer extruder heads, which I have taken the extreme liberty of referring to as Mk 2a. I thought a picture might be in order:

Some of the materials are different; the bits attached to the motor are made from SLS nylon, for example. Also I've used Philips head screws instead of cap screws throughout. There are a few other changes from the original design:

o The springs have been replaced with silicone tubing.
o The central channel that guides the filament now has little walls.
o The PTFE rod is now 16mm diameter.
o The nozzle is interchangeable.
o The filament is insulated nichrome, though this isn't working well.
o The coil is insulated and kept stable with fibreglass/plaster.
o The thermistor is on a tag, pierced by the barrel.

Does it work? Dunno yet. I have a Mk2a extruder controller board to build first!

Vik :v)

For interchangable nozzles, I found that sliced brass nuts with metal tips from pens and mechanical pencils works well. they solder right onto the end (it appears from the image that you have done similar)

Got 3mm and a .7mm tips that way with minimal effort.
Vik: That new extruder really looks great!

Reiuki: Wow! That's quite a nice little dodge for getting a good extruder tip. I hope you don't mind if I borrow it. :-D
The nut is actually a carefully shaped item, with as shallow a narrow bit as I can possibly manage. I've posted full details here:


Vik :v)
I was actually thinking of the same idea -- using a mechanical pencil tip for the extruder nozzle.

I was thinking of grinding it down to reduce flow resistance. I was also thinking a wire pushed into it from behind would make a reasonable on/off switch -- used in combination with an air compressor (another great idea.)
Preventing the wire from bending is going to be an interesting proposition :)

Vik :v)
Pencil idea is brilliant!

Instead of the wire shutoff, why not a nice stiff pencil lead of exactly the right diameter made from very-high-temperature-resisting, low-friction, graphite?

Not strong, I admit. But then not subject to lateral stress if the design is right.

Now - how can we use the pencil clutch mechanism to make the valve work?
Post a Comment

<< Home

This page is powered by Blogger. Isn't yours?

Subscribe to
Posts [Atom]