Well, the heated build platform is finally installed, wired up, and controlled by the extruder controller. I still need to calibrate the new firmware to the thermistors. I have a 1mm in the extruder and a 3mm in the HBP. In the end I've gone for a relay to drive the heater element, its a FRA2 from jaycar. The first data sheet
I found for it was in German, but the diagram covers the pin outs. I haven't included a diode for suppression of back current, as there is one in the mosfet driving the relay (so I've been informed by someone on the makerbot google group). The other bits
all assembled as expected. The heater element is mounted to the aluminum plate with 24mm wide kapton tape
, and then backed by the ceramic wrap that was supplied with my makerbot kit. I used the makergear braided insulation on the print head. I've raised the aluminum plate off the wooden build platform by putting a long M3 bolt through from underneath and spacing it out with spare M3 nuts.
I've run it up to an indicated 108C, which was enough to burn my self :), but I'll wait until I have a bit more confidence in the reading before I proceed. I have a couple of LM35
temp sensors and an unused arduino board, which I'll used to confirm the thermistor readings. I might get some sleep first though.
When I get printing again, I think the relay will need a nice mounting clip. :)
Photos will follow.
Note: the temp was still climbing at this point.