Tuesday, October 06, 2009
Getting away from fire cement...
When I tried to insert the PEEK thermal break, however, things went wrong. The PEEK cylinder jammed in the extruder barrel's sleeve and in trying to get it back out again I managed to apply a bit of torque to the barrel. This shattered the fire cement.
I was able to recover both the thermistor and the nichrome heater wire, largely because the fire cement, even oven cured, has the consistency and tensile strength of dry silt mud. I cleaned the barrel with a small screwdriver and electrical pliers with zero trouble. You can see the results here.
I had used ceramic coatings before with nichrome and called Danny at Cotronics in Brooklyn. He recommended their 907 formulation which is, if I've read the data sheet correctly, a mica-based ceramic adhesive formulation with considerable compressive and tensile strength. Better still, I was able to order it through a retailer, McMaster-Carr, here in California in Long Beach. I was able to get it ordered, shipped and delivered overnight using a local courier service for about $5.
Right now I am trying to decide whether I should sand it down before or after I heat cure it. If I'd been smart I would have painted it on after I installed the heater barrel flange, then having to slide the flange over the ceramic adhesive wouldn't have been an issue.
It adheres very tightly to the aluminum.
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