Well, since my last post the Makerbot has been busy!
Busy breaking and requiring troubleshooting and maintenance. But that's behind us now; I've a lot more knowledge of Makerbotting, and a much tougher Plastruder as a result. Many, many thanks to Mark Adams for the replacement part he printed and sent to me!
So, I'll keep it brief. The Makerbot is prone to a failure that occurs when plastic melts too high up in the barrel; this leads to increased friction, but also to some molten plastic being shoved up into the insulator by displacement as the filament forces its way down. This molten ABS hardens in the insulator, causing a tight blockage. The result is that printing requires steadily higher printing temperatures to melt the blockage upstream, which can lead to two potential failures:
Your insulator overheats, softens and the heater barrel is forced out by the hefty forces applied to the filament inside. Very bad news, as this usually de-threads the insulator and demands a replacement. Building a plastruder using an M6 nut to take the forces instead of the insulator seems to be a reliable preventative measure.
The diverted forces instead cause your insulator retainer (or worse, the lasercut parts above it) to shatter violently.
In my case, it was the retainer piece, a circular piece of acrylic (as given in the kit) that is apparently there to keep the insulator from wobbling away from the filament's entry point and also to shatter instead of the more important parts above. Thankfully, a printable replacement is available on Thingiverse.
I fixed it and upgraded it
While I awaited the donated replacement part (did I mention I love this community? Fellow Makerbotters rock!), I ordered and installed a proper internal power supply, so the Makerbot is prettier and more mobile. I also was donated a little hose clamp from my Mechanic up the road, which some recommend as both a brace and a heatsink for the insulator. Finally, I rebuilt the plastruder so the circuit board was out-of-the-way, which makes it easier to see what I'm doing.
The end result:
And it prints!
I used a delightfully geeky item for my test print: A Clip-On Reading LED for glasses. It printed quite beautifully, but didn't fit my glasses (which are usually pretty small-framed). So, I drilled two holes, threaded a tiewrap through and used it as a wedge to fit smaller frames. I plan to put a red LED in there so I can use it for nighttime navigation without losing my nightsight! I just need a battery now.