Thursday, April 21, 2011

April 21, 2011

I replaced one of the broken TIP120s on the pwm heater boad with a MOSFET, testing with a multimeter looked like it was working properly, so I connected it to the heated on my extruder. Testing that proved, or created, a short in the nichrome heater somewhere. Instantly smoked and fizzled. So I killed it and left it to today.  I have it dissected so far, and I did not find the short, but there was a blob of black PLA where the PWM leads connect to the nichrome wire, so it could have been in there... or something else made a terrible smoke, acrid smell, AND killed the heater... maybe a tiny Genie... for my First wish, a thousand more wishes and my Second; a simpler to disassemble hot end with a resistor heater block, and Thirdly; a peanut butter, banana, cream cheese sandwich.

Since I still have an amount of nichrome wire I'll just have to rebuild the same design.  I might as well get some pictures of what I've been doing to wrap my hot end.

Monday, April 18, 2011

April 18, 2011

I'm posting this set of PLA Prusa Mendel parts to Ebay in a moment... (here it is) it's been a long to trip to finishing this set.  There was a power brown-out here about 2 weeks ago, I've never found a need to buy a UPS until then. I was in the middle of a long print, 1 of 2 last parts for this set of parts, the computer shutdown, my printer's power supply developed an odd tick to it, which I found later... So after hours of trying to find out why I couldn't hold at a decent heat after the power outage, and the printer kept stopping for no reason in the middle of prints I discovered the PSU was dying, then a transistor for the heater blew up with what seemed like a thunderous clap.
I switched the PSU out, switched to another pwm channel on the heater board... everything seemed to be coming up roses. I still couldn't get the heater to work properly... anyway lots of desoldering, repairing, and resoldering... still no good solution. So the last two parts to the set were the extruder block, and 39 tooth gear, I had a few spares sitting around... They aren't as high quality as I'd make today, but it completes the set. And I can move on to rebuilding electronics.

I have a couple MOSFETs I got from digikey that I think I can use to repair the PWM heater board.  And I'm starting on a new arduino board similar to the sanguinololu in principle, but I have an atmega328p.  I'm thinking a simple Arduino, bare-bones laid out on perfboard, one heater circuit, one thermistor circuit, connections out to sensors, and stepper boards.  If I can repair the PWM heater board, this will be a start on a new 'bot, but if not; I have a replacement for the rat's nest that is running my printer now. Point to point wiring has worked, but it is certainly not intended to last as long I've been using it.

*exhale* Time to go for a run.