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Extruder Heater Materials
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To attach the barrel to the extrusion mechanism, a rigid block of insulating concrete is used. This need be no more than 50mm in diameter and 60mm high. Any narrower in diameter, and it will be hard to get enough concrete around the threaded rod that will attach it to the extruder mechanism.
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Concrete itself is quite stable at temperatures up to 300C (540F), and can take twice this for brief periods without significant damage. However, it may shed particles at high heat, which is not good news for nozzles.
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A concrete is made from cement mix with added perlite and vermiculite. Due to the small size of the insulator, a fairly damp mix may be needed to ensure the concrete cures before it dries out. This, of course, weakens the concrete so a happy medium needs to be found. Absolute minimum use of water and precautions against evaporation should be tried.
A 3mm knitting needle through the centre of the block will maintain the central cavity, and hold the heater barrel in allignment. The needle will be removed before the concrete fully hardens and the hole tidied manually. Hardener or ceramic paint may be necessary to prevent wear at the edges.
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