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.

Category: Machine Shop

Mechanical widgetry

  • Acrylic Engraving Dust

    Acrylic Engraving Dust

    The MDF signs I made last year disintegrated pretty much on the expected schedule, so it’s time for something more durable:

    Please Close The Gate - acrylic engraving
    Please Close The Gate – acrylic engraving

    The idea is to engrave both sides of a 3 mm orange acrylic sheet, shoot it with rattlecan black paint, and declare victory. The second step awaits warmer weather, but at least I’m doing my part to prepare for the new gardening season.

    Vaporizing that much acrylic produces a fair bit of debris:

    Please Close The Gate - acrylic dust on laser head
    Please Close The Gate – acrylic dust on laser head

    Some dust / vapor accumulates / condenses on the honeycomb platform beyond the orange sign, but most of it gets through to the baffle on the exhaust duct:

    Please Close The Gate - acrylic dust on exhaust port
    Please Close The Gate – acrylic dust on exhaust port

    A closer look shows it really does grow out from the perimeter of each hole:

    Please Close The Gate - acrylic dust on exhaust port - detail
    Please Close The Gate – acrylic dust on exhaust port – detail

    Now, if that doesn’t trip your trypophobia, nothing will …

    A few passes with the trusty Electrolux vacuum’s dust brush brought the visible surfaces back to normal.

    By now, the duct fan blades have surely layered on a good coating, too, which shall remain undisturbed until I find a better reason to open the duct.

  • Brick Wall in Z-Scale

    Brick Wall in Z-Scale

    A LightBurn forum discussion about problems making Z-scale (1:220) bricks led me to trying a few ideas on the way to figuring out what was going wrong.

    Each brick is about 1.0×0.5 mm, so an entire wall doesn’t cover much territory:

    Z-scale bricks - assortment
    Z-scale bricks – assortment

    Yes, those are millimeters along the scale.

    The kerf on my 60 W CO₂ laser seems slightly wider than the “mortar” lines should be, so I made a layout with the vertical lines slightly inset from the horizontal ones:

    Z Scale Brick Wall - LB layout
    Z Scale Brick Wall – LB layout

    That let the kerf complete the lines without burning into the adjacent bricks:

    Z Scale Brick Wall - laser lines
    Z Scale Brick Wall – laser lines

    The cuts are obviously too wide (and deep!), but just for fun I colored the chipboard with red marker and rubbed a pinch of flour into the lines:

    Z Scale Brick Wall - color and flour
    Z Scale Brick Wall – color and flour

    Which looks chunky, but not terrible, for what it is. Maybe concrete blocks would look better?

    The next attempt started with a raster bitmap scaled at 254 dpi = 10 pix/mm, so that single-pixel “mortar” lines between 10×5 pixel bricks would be 0.1 mm wide:

    Raster Z-Scale Bricks
    Raster Z-Scale Bricks

    Scanning the image at 100 mm/s makes each pixel 1 ms “wide” and, because the power supply risetime is on the order of 1 ms, the laser won’t quite reach the 10% power level across the vertical lines:

    Raster Z-Scale Bricks - LB layer settings
    Raster Z-Scale Bricks – LB layer settings

    The raster lines come out lighter and (IMO) better looking:

    Z Scale Brick Wall - raster lines
    Z Scale Brick Wall – raster lines

    The horizontal lines are darker because the beam remains on at 10% across their full length, but the overall result seems much closer to the desired result.

    The original poster will use a diode laser and, combining all the ideas we came up with, now has a path toward making good, albeit invisibly small, bricks.

    His modeling (and coloring!) hand is strong!

  • Bobbin Rock

    Bobbin Rock

    Mary handed me a bobbin with a trouble report: it fit into the bobbin holder either way, but would go into the sewing machine either poorly or not at all.

    Based on past experience with this lot of bobbins (*), I expected to find a burr inside the steel hub left behind by the saw cut creating the drive dog slot, so this came as a surprise:

    Bobbin Rock - overview
    Bobbin Rock – overview

    A closer look:

    Bobbin Rock - detail
    Bobbin Rock – detail

    That pebble was jammed in place so firmly I needed a pin punch: a small screwdriver wasn’t enough.

    It came new from the factory like that, which makes one wonder just exactly what the factory floor looks like.

    More likely, the bobbins spend their last few hours in a vibratory polisher and that little rock just crept with all the walnut shell kibble.

    Works fine now, so we’ll call it a win.

    (*) I gave her a lot of 100 to ensure she never had to unload a bobbin to keep her new Juki well-fed.

  • Ersatz Library Card: Fixed

    Ersatz Library Card: Fixed

    Sharper eyes than mine pointed out I misspelled Poughkeepsie, so I took advantage of the opportunity to make the whole thing look better:

    Library card tag - revised front
    Library card tag – revised front

    It turns out the low-surface-energy tape stuck like glue to the acrylic tag (because that’s what it’s designed for) and peeled right off the laminating film on the printed paper. So I stuck some ordinary adhesive film to the back of the new paper label, left its protective paper on the other side, cold laminated the film+paper, laser-cut the outline, peeled off the back side of the laminating film with the protective paper, and stuck the new adhesive to the LSE tape still on the tag.

    I have no idea how well this will work out in the long term, what with two adhesive layers bonded to each other, but this whole thing is in the nature of an experiment.

  • Eyeglass Spring Temple: Screw Hole Tweak

    Eyeglass Spring Temple: Screw Hole Tweak

    A screws in one of Mary’s eyeglasses unscrewed itself, but, miraculously, we found it and I retired to the shop.

    Because the glasses have spring temples, the screw would not align no matter what force I applied to it:

    Eyeglass spring temple - screw misalignment
    Eyeglass spring temple – screw misalignment

    So I just embiggened the hole until the available force did the trick:

    Eyeglass spring temple - hole filing
    Eyeglass spring temple – hole filing

    Dots of Loctite worked into the threads should prevent that from happening again, but I’ve learned to never say never.

    In retrospect, the temple pivots have an exposed slot that I think would allow jamming a block in place after pulling the spring-loaded pivot outward. Temple springs are impossibly stiff and I have previously failed to budge them in glasses without the slots, so I don’t know how well that might work.

    Verily: If brute force isn’t working for you, then you’re not using enough of it.

  • Kitchen Under-sink Cabinet Fan Incident

    Kitchen Under-sink Cabinet Fan Incident

    During the course of diagnosing and fixing the latest oven igniter failure, an unrelated series of events produced a flood under the kitchen sink and across the floor. After cleaning up the mess and determining the floor under the cabinet was merely damp, rather than wet, I drilled a hole suitable for another PC cooling fan from the Box o’ MostlyFans, installed the fan to pull air upward, and let it run for a couple of days while watching the humidity drop.

    Fortunately, I had a hole saw exactly the right size for an 80 mm case fan:

    Kitchen sink - fan cover plate
    Kitchen sink – fan cover plate

    I will lay big money on a bet saying your kitchen cabinets don’t have Real Wood like that, nor are the interiors painted bold Chinese Red. This place really is a time capsule from 1955.

    While the drying happened, I made a hole cover from 1.5 mm black acrylic and, there being no style points involved, rounded up a quartet of black-oxide self-drilling sheet metal screws to hold it in place.

    Although it’s not obvious, there’s a layer of transparent plastic “shelf paper” in there. It covers the fan hole under the cover, so any future spills will have approximately the same difficulty reaching the floor as this one did.

    The LightBurn layout produces both the fan cover and a template to mark the four screw holes around the fan opening:

    Kitchen Sink Fan - LB layout
    Kitchen Sink Fan – LB layout

    The blue tool layer lines serve as a guide for the rest of the cover layout; the matching orange square on the right marks the fan outline on the drill template as a quick size check.

    No need for an SVG version, because now that you have the general idea, it’s easy to recreate it for your own fan.

  • Kenmore 362.75581890 Oven: Another Igniter Bites The Dust

    Kenmore 362.75581890 Oven: Another Igniter Bites The Dust

    Our story so far:

    • We installed a Kenmore gas range around the turn of the millennium
    • 2006 – Oven burner tube & igniter replaced
    • 2014 – Igniter replaced

    Apparently igniters last about eight years, regardless of provenance, because the igniter just failed, with the usual symptoms of low current draw (about 2 A), failed ignition, and a faint smell of propane (well, mercaptan) before the safety valve kicked in:

    Oven igniter - location
    Oven igniter – location

    The new igniter, another low-buck Amazon offering, came with half a green plastic connector block that mated neatly with the existing half under the oven. Unfortunately, the new wires had female pins crimped on their ends, rather than the male pins required by the existing connector and the ceramic wire nuts I’d used to join the previous igniter to the OEM connector were non-removable.

    So I trimmed the old wires to a usable length and applied the new ceramic wire nuts to the stubs:

    Oven igniter - connector rewiring
    Oven igniter – connector rewiring

    Also as before, the new igniter measures 3 A, definitely below the low end of the valve’s 3.3 to 3.6 A range:

    Oven igniter - current test
    Oven igniter – current test

    If this one lasts eight years, I won’t be the guy replacing it …