Thursday, February 5, 2009

NoGo Extruder

Well I thought I would try a variation on Forests 5/32 tube extruder. My goal was to combine a variation of Forest’s approach along with Demented’s to come up with a hardware store extruder that didn’t require any machining or brazing.

I worked out a variation to Demented’s approach that is easy and I am happy with (more about that in a future post assuming it actually works).

Links to their posts where I got the idea’s from are:



Anyway on to passing on what didn’t work.

What I didn’t initially like is that Forest’s extruder was the same Nichrome Wire/JB Bond or other cement, and the fixed one shot nozzle size.

I had what seems to be winner to avoid with my experiment with four five watt resistors.

Here’s my attempt to resolve this:

My first idea was to simply retract the fiber about a centimeter and fill it in with solder as nophead did on his test of the de-soldering iron and then drilling the solder. Like nophead did with his de-soldering iron test.

In hindsight I may revisit this once I figure out what high temperature solder really is.

While it was easy to fill the end of the tube with solder and drill out a 4.5MM hole. In my initial test it showed the temperature going up to 180C and then my solder came out as a big blob, so I must have been using the wrong conversion table or didn’t get enough heat transfer between the tube and sensor.

Anyway after that experience I figured I would go with solid brass for my heater area and this is what I came up with.

Previously I had surrounded the heater barrel with the power resistors that I had sanded the corner off.

Since this 5/32 tube was of a smaller size and with the mass of the brass fittings I assumed it would be better to heat the fittings and nozzle and let heat travel up the tube to pre-heat the filament as it enters the final stage.

To minimize the heat escape; I used fiberglass gasket material for doors on wood stoves.

Experiment results

Didn’t quite work out the way as when I heated everything up I got initial feed of the filament and then everything came to a stop no matter how hot I cranked the heat up too.

So what happened?

Here’s the view after taking the nozzle off.

First attempt to pull the road block out.

What it looks like after extracted out of the tube.

Everything pulled out.

Ok what have we seen?

First off no melting took place in the primary heat transfer area or the nozzle, all the heating of the fiber was from heat that transferred up the tube from the limited contact between the fittings that made up the nozzle assembly.

The initial filament movement was melted fiber from the tube being pushed into the gap or well between the fitting and nozzle plug, after that it solidified and prevented future movement and turning up the heat cooked it into a harder mass.

So what might have made this work?

If I had prefilled the chamber area behind the nozzle with plastic to be melted and form a reservoir to be refilled!

What did work?

Heat traveling up the tube to uniformly heat the ABS fiber from all sides.
Fiberglas gasket material as insulator.

What also didn’t work?

I had tried stove and gasket cement as an easy bonding agent, but it turned out to not bond too well between the fittings and the power resistors and was fragile to any mechanical pressure.

Might have been better if I used it liberally.