Saturday, 5 May 2012


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I managed to repair my heated bed after nophead kindly brought a replacement power resistor into work last Monday.

When I've been printing large (200mm x 60mm) ABS parts I have relied upon the heated bed of my printer to keep the chamber hot enough to prevent warping. I later added a temperature controlled hot air gun to heat the chamber as in winter, the bed alone fails to keep it hot enough.

The hot air gun was software controlled through the PC parallel port, via an interface board. At the end of every vector, the software queries the cabinet temperature and turns the heater on if required.

This scares me. If the controlling software, or Windows, crashes. I am left with a heat gun dumping its output into my heated chamber with no control. I don't want to come back to find my printer melted, or my garage on fire.

So today I built this:

It is a combination of a thermostat and power relay. My PC controls the relay, and turns on power to the mains socket when the cabinet needs heating. The power is routed through the thermostat, so that if the relay is left on for too long, the maximum cabinet temperature is limited by the thermostat.

The worst case scenario with this configuration is that I return to find a failed print and a hot cabinet. But at least I will still possess a printer and a garage.

The sensor part of the thermostat looks a bit ugly inside the cabinet though:

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