Monday, 27 July 2009

Heater Blocks

In my quest to ignore conventional wisdom and make my own extruder, I've started playing around with resistor heaters in blocks like NopHead.

I looked around for a while, and found a mild steel block (30x30x10mm) at my local engineering suppliers. They also supplied me a couple of 1 inch (25mm) cubes of copper.

With one of the steel blocks, I drilled two 7.5mm holes laterally and filled them each with a resistor wrapped in tinfoil to provide a tight fit (and better heat transfer). I drilled a 5.5mm hole through the block and tapped it to M6 thread.
From ResistorHeater
With an M6 welding tip, I extended the m6 thread to all the way down the barrel. Then, drilling it out to 3.2mm, I made a mistake and drilled it all the way through. I now had a short copper tube with m6 outer thread. This screwed through the heater block, leaving 5mm top and bottom. The existing BfB nozzle screws nicely onto the copper thread.

Screwing a m6 coupling nut onto the top allows me to connect a drilled stainless steel bolt. Stainless steel is a poor conductor of heat - not as good as PTFE insulation, but helps stop the heat transfer up the shaft.
From ResistorHeater
Firing it up, there is a lot of thermal inertia - it takes a while to get going (2-3C per second). It finally tops out at 210C without any insulation. The stainless is not a brilliant insulator - it gets fairly hot (70C) at the washer/support end, but should be usable.

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