Launch the goo!

It took some doing, but the reprap is finally squirting plastic.

A lot of faffing about with the firmware and the thermistor started reading approximately the right temperature, so I could start testing the hot end. Unfortunately I soon discovered that the thermistor would short out when it got above about 130 degrees, and start reading 255 permanently until it cooled down and I fiddled with the leads. Since the short appeared to be somewhere in the thermal epoxy I ended up digging away at it to try and expose more of the thermistor leads... and broke one in the process. Oh no! Some more digging and I was able to expose enough of the broken lead to solder back to it. After that the thermistor started behaving reliably. Yet another bullet dodged! Then we had a bit of trouble getting the hot end to heat up enough, so Buzz wrapped some fire blanket around the hot end to insulate it a bit, and finally the hot end was working well.

And the smell? It gave off a bit, but only enough to notice it and not enough to act like mustard gas now that the control loop is closed - thank god.

I sent the G-codes to start the extruder motor... and watched as the machine stubbornly refused to activate it. Aargh! A couple of hours of hardware testing didn't get me or Buzz anywhere, so I had to come back after a nights sleep to attack the firmware code and find out what was happening. Turns out that the firmware defaults to an extrusion speed of ZERO, and will faithfully turn on the extruder motor at that speed - the reprap host software isn't explicitly setting the speed. Changing the extruder speed manually to 255 before turning it on got it going immediately.

Setting the heater on to 190 degrees and starting the extruder motor gave me some nice little blobs of goo, which I then stretched out by moving the head most of the way across the print bed. And then the X-axis stopped moving - turns out that the shaft coupling on the stepper had worked it's way loose, and I ended up having to disassemble it to realign and tighten the grub screw down hard(-ish) again. There's only so far I can do that without ripping the acrylic coupling apart, so I might have to get in there with some superglue or epoxy if it comes loose again.

Speaking of the steppers, there's something of a heat problem with them. The steppers themselves get very hot, which isn't too big a problem (and I have a couple of random CPU heatsinks stuck to them now) but the stepper drivers get even hotter, which is. The heatsinks aren't sufficient to keep the chips cool, and when they get too hot (i.e. ten seconds after power on) they start sending lots of random steps to the motors. I've got a fan set up, but it's only able to keep the X and Y drivers cool. Before I finally start the Z axis up, I need to sort out a much better heatsinking solution for all three driver boards.