Archive for October, 2013


October 25, 2013



What’s worse than this dog’s breakfast is the fact that I thought I had blown out the stepper motor in the previous extruder after weeks of running it way too hot, but after I’d gone too far with this version to unwind my hot-end modifications, I found I hadn’t.  It’s a really bad design, but it was what I could do without being able to print up any new parts. Probably my most serious mistake  is the idler, which is a skate bearing in a bent-aluminum frame being pushed against the old makerbot drive pulley by those three torsion springs, which were the strongest things I could find at the local hardware store. All the pivoting designs have a serious mechanical advantage, but this has none. The springs acquire a permanent bend and stop working after a few hours, so I am ordering some stamping-machine compression springs from McMaster-Carr that max out at about 200 pounds. With luck, it will last long enough for me to print a lever-action extruder and maybe even some herringbone gears.


I found myself thinking a lot about the kind of design you do when bodging pre-existing parts into shape versus printing pieces from scratch. I can go to the drill press and put a new hole in my piece of old aluminum extrusion in a few minutes, or bend a piece of flat stock to the right shape and drill and tap it. But once I’ve done that, especially with the extrusion body, I’m pretty much stuck with it, unless I want to chop up another piece and start from the beginning. If I print something, it will be a few hours (at least), but if I have a completely different idea I can just discard the old piece and print up the new. It’s a very different style, sorta like the difference between writing software at a REPL or in a really fast IDE versus old-fashioned edit-compile-make-run-curse. But also sorta not. Anyone else have thoughts about that?

Oh, and I also learned that the mini-hyena drive gear is brilliant for an extrude that’s well tuned, but once you start slipping  you’re going to need acetone or fire or who knows what to get the ground-up filament out of those sharp little grooves.