It's been a while since my last update, not for lack of having done anything, but rather because I haven't had much time to write it up.

First things first, the frame has progressed some more, and the lower print bed is now attached: IMG_20121116_174955.jpg

Mostly no problems here, except at the top of the frame I found that the M3 bolts were a bit too long and interfered with the motor, so I put three washers on each one: IMG_20121027_021822.jpg

My main achievement recently though is with the heated bed. My first plan was to take a plate of aluminium and glue the PCBs to it copper-side to the metal, but first covered with conformal coating to prevent short circuits. I'd fix them down with superglue round the edge and thermal paste in the middle. I first drilled a hole through the corners of the PCBs... IMG_20121101_193448.jpg ..and put vias through, soldered on the track side and sticking out the component side. IMG_20121101_211311.jpg

This left raised blobs of solder on the board, so to accomodate for these I dremelled away at the bottom of the aluminium sheet. IMG_20121101_212230.jpg

I covered the PCBs in conformal coating, about four layers iirc. I quickly got bored of waiting for them to dry, so hooked them up to 12VAC to speed up the process. IMG_20121101_222349.jpg

...and then I stuck them down with superglue and thermal paste. IMG_20121102_010716.jpg

Not thinking to test the resistance first, I wired the whole thing up to 12VAC and it caught fire. In hindsight, this was a shit idea. Clearly the conformal coating had failed at the solder points and short-circuited the whole thing. Armed with a bottle of nail varnish remover, a screwdriver and a scourer, I set about removing the boards and cleaning up the plate. I removed the vias from the PCBs and glued them back on, this time component side to the plate. I'd initially wanted to avoid doing this because of the thermal resistance of the PCB, but it seems I have no other option. Here's the end result: IMG_20121116_182144.jpg I still need to mount the thermistor (probably with milliput) and wire up the PCBs. I need to buy some silicone wire first for this.

And the other side of the heatbed, covered in kapton tape. There are a lot of air bubbles although I tried my best to avoid them. In any case, I'm not sure how this affects the print quality. IMG_20121116_182202.jpg

So that's my progress to date. I'll continue to post updates here.