The Smell of Molten Projects in the Morning

Ed Nisley's Blog: Shop notes, electronics, firmware, machinery, 3D printing, laser cuttery, and curiosities. Contents: 100% human thinking, 0% AI slop.

Author: Ed

  • Opossum in the Attic!

    Quite some years ago, before I stapled a wad of steel wool in the hole gnawed in the corner of the garage door, the scrabble of little feet in the attic meant it was time to re-bait the mouse traps. Then, one night, we heard the scrabble of big feet in the attic…

    This is the point where the horror film audience starts chanting “Don’t open the door! Don’t open the door!“, but, to our credit, we did not don our skimpiest underwear before venturing into the attic. We didn’t encounter any zombies, either, but we did find this chap:

    Opossum in attic
    Opossum in attic

    This is about as far north as opossums get; their ears suffer frostbite over the winters and get all raggedy, hence the pink teddy bear aspect. These are not, however, cute and cuddly critters.

    The house has a full hip roof with a four-foot soffit over the patio, which must be the best place for a ‘possum to hang out:

    Opossum in attic soffit
    Opossum in attic soffit

    Some quick searches with the usual keywords suggested leaving the lights on and playing loud music, so we deployed several shoplights and a radio turned up all the way. It took two or three days, but eventually Mary spotted the critter on its way out of the garage… and now we don’t leave the garage door open any longer than needed.

    FWIW, the path from the garage to the attic requires climbing those shelves, scaling three feet of vertical plasterboard wall, then crawling through a (now securely closed) vent hatch.

  • Exposed Stepper Motor Windings

    Got a stepper motor from halfway around the planet from the usual eBay source, intended for a direct-drive extruder (at some point). This one has integral wire leads, which is fine with me, but the opening in the rear endcap reveals a bit more of the innards than one usually sees:

    ACT 17HS5425 stepper - exposed winding
    ACT 17HS5425 stepper – exposed winding

    Yup, that’s one winding peeking out. Although the wire insulation should take care of anything conductive, I’d expect the same casual attention to detail in the winding terminals.

    I’d worry more if this were being used in a metal-cutting operation, but a snippet of heatshrink tubing and a blob of hot-melt glue seem in order.

    For what it’s worth, the motor is an ACT 17HS5425:

    • 1.8°/step
    • 48 mm case length
    • 3.1 V
    • 2.5 A
    • 1.25 Ω
    • 1.8 mH
    • 48 oz·in holding torque
    • 2.8 oz·in detent torque
    • 68 oz·in rotor torque

    No torque curves and nothing more in the way of a datasheet.

  • Tour Easy: Squeaky Pedal

    Of late my Tour Easy has developed a squeak at the pedal-go-round rate. It has Performance Bike Campus pedals, with SPD cleats on one side and a rat-trap surface on the other, and only the SPD side squeaked.

    Turns out that the two little mounting screws holding the cleat dingus worked their way loose.

    SPD pedal screws
    SPD pedal screws

    I should probably ease some lube under that plate, just to be sure, but the simple fix worked fine…

    (And, yeah, I should clean it, just once, to see what it’s like, right?)

  • Upholstered Mouse Nest

    After rearranging the pressure washer pipes, I hauled the grill out on the driveway and opened the lid. My Shop Assistant denied putting that ball of fuzz in there:

    Wool ball in propane grill
    Wool ball in propane grill

    Gingerly prying it open revealed a mouse-sized pocket in the middle:

    Wool ball interior
    Wool ball interior

    And a bit of investigation uncovered the source of the batting. Evidently, the corner seam of the ancient lawn couch thing (which came with the house and has been unused for over a decade) sitting on the patio had burst, leaving just enough room for an industrious mouse:

    Source of the wool ball
    Source of the wool ball

    They’d been camping inside the cushion at least over the winter and evidently used the far corner as their latrine. We bagged the whole cushion and added it to the van full of trash headed for the town’s bulk collection, which fortunately occurred that weekend.

    Now, to haul the frame to the metal recycler and take advantage of the current commodity price bubble…

  • Thing-O-Matic: Bicolored Prints

    This isn’t rocket science and it’s certainly not original, but I finally screwed up enough courage to start routinely swapping in a new filament color without pulling out the old one. The trick is to cut both ends flush (with a flush-cutting wire cutter) and maintain gentle pressure on the new filament so it slides right into the grip of the extruder drive gear.

    Seeing as how I need tchotchkes in a big way, I run off a plate of Chalk People whenever it’s time for a new color:

    Multicolored Chalk People
    Multicolored Chalk People

    The transition between yellow and black was rather weird. Fortunately, the gory details remain hidden inside that quartet of Chalk Women.

    These have all the right attributes for a tchotchke: fast printing, not much plastic, smooth edges, a little fill to show how it works, a few small defects for education.

  • Reversal Zits: Temperature Variations

    Just for completeness, it turns out that extrusion temperature doesn’t have any effect on Reversal zits. A while back I dropped the standard temperature from 210 °C to 190 °C in one fell swoop and it didn’t change anything worth mentioning, let alone the zittage.

    The white one was hotter, the orange one is cooler:

    Octopodes - Temperature variation
    Octopodes – Temperature variation

    The zits are pretty much due to Reversal followed by in-plane motion, it seems to me.

    A dramatically lower extrusion temperature works fine for smaller objects, but I’d expect very large objects to delaminate like crazy. The Barbie Pistol was, IIRC, printed at 220 °C, and it had some troubles.

    It’s also worth noting that the indicated temperature has only a casual relationship to the actual extrusion temperature. I’ve put considerable effort into electrically insulating and thermally bonding the thermocouple to the Thermal Core, so I think it’s a good indicator, but your results will certainly differ.

  • Reversal Zits: Speed Variations

    The Vica Illusion Sculpture provides an interesting data point: Reversal zits aren’t much of a problem at very slow extrusion speeds.

    This view shows it lying down, with focus on the the zits along facing edges of the columns.

    Vica Illusion - Reversal zits
    Vica Illusion – Reversal zits

    They’re annoying, but not nearly as obvious as the ones on the Pink Panther Woman I examined yesterday.

    The nominal speed is 30 mm/s with 100 mm/s moves, but the actual printing speed for those layers works out to maybe 15 mm/s because they’re so small.

    In round numbers the extruder runs at half the previous speed, too, which means its internal pressure will be lower. I’m sure that’s a breathtakingly nonlinear process, so it’s not half the pressure.

    Low speed isn’t the complete answer, though, because I’ve also done octopodes at 20 mm/s that looked essentially identical to those at 30 mm/s. Yes, it’s nonlinear, but I doubt it falls off a cliff under 15 mm/s.

    I set Reversal to 25 rev/min and 125 ms quite some time ago as the smallest values that would eliminate drooling between separate parts. The only thing for it will be to explore the Reversal parameter space again; at least now I know what I’m looking for.