Friday, February 10, 2006


Concrete insulator Mk 1

I've just taken the concrete insulator assembly out of the mould. Here's a view of what it came out looking like. Prognosis is good, and it is now drying off in a reasonably safe location with the heater barrel still in place. The concrete is quite dense due to the use of vibration to settle it, though there are still some bubbles visible:

I worry that the concrete will shed bits into the polymer stream and jam the extruder head. :-(
Me too. But with the test article, there is a very limited amount of shedding, and that goes away after a brush-down. I have pulled a piece of wire wool through the bore a few times, and can now no longer cause it to shed. The vibration has caused the concrete to be quite dense.

Also, there is no great stress betwene the side of the plastic filiament and the sides of the bore.

Oh, the heater barrel unscrewed from the concreted nuts without much difficulty.

Vik :v)
Perhaps the bore could be glazed with a light wash of water glass, if this is a serious concern? For instance,


I suspect it would also enhance the tensile strength a bit, by closing up crack nucleation sites.
Good idea. I'll see if it's necessary first though. I don't mind wrecking this one; it's not very tidy. Quite servicable though, I strongly suspect.

The BBQ-painted heater barrel has unscrewed from the concrete, and I've given it 5 coats. It is now enjoying the company of my weekend roast while the paint cures properly.

Tomorrow, I attempt to plaster-cast on the heating element with glass fibre.

Vik :v)
Well, have you tried extruding with it yet? :-)
Nope - got to make more 3mm Polymorph. How's that bulk extruder coming along?

I have however managed to get it up to 195C, and the concrete is doing its job wonderfully.

I might need some PLA filiament too!

Vik :v)
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