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: Home Ec

Things around the home & hearth

Ceiling Lamp Nuts
While cleaning dead bugs out of the ceiling lamps, we discovered the kitchen light was missing one of the three nuts holding its cover in place. While spare nuts might be available, this seemed like a quicker & easier solution:

Ceiling Lamp Nut – bottom view – solid model

The stepped interior fits a brass insert with 8-32 threads (not metric, to my utter astonishment) rammed in place with a heat-set tool:

Ceiling Lamp Nut – insert staking

Using the nominal diameters seems to work fine, although I’m sure some finesse will be needed with smaller inserts.

Printed four just to be sure, rammed three inserts, and they’re ready:

Ceiling Lamp Nuts – as-built

The curved cap matches the original nut through the use of the Chord Equation to get the cap radius as a function of its height (sagitta) & base diameter. Admittedly, it looks kinda grotty with only a dozen layers, but it’s the thought that counts.

The original nuts are heavy knurled steel and the new ones are cheap plastic, but nobody will ever know:

Ceiling Lamp Nut – installed

Bonus: now I have two spare steel nuts for the next time …

The OpenSCAD source code:
```
// Nuts for LED ceiling light fixture
// Ed Nisley KE4ZNU
// 2024-09-27

KnurlLength = 7.4;
KnurlOD = 9.0;

CapOD = 9.0;
CapHeight = 2.0;
CapRadius = (pow(CapHeight,2) + pow(CapOD,2)/4)/(2*CapHeight);
echo(CapRadius=CapRadius);

NumSides = 1*(2*3*4);
$fn = NumSides;

Protrusion = 0.1;

difference() {
    union() {
        intersection() {
            translate([0,0,KnurlLength + CapHeight - CapRadius])
                sphere(r=CapRadius);
            translate([0,0,KnurlLength])
                cylinder(d=2*KnurlOD,h=KnurlLength);
        }

        cylinder(d=KnurlOD,h=KnurlLength);

    }

// Ad-hoc 8-32 brass insert sizes

    cylinder(d=5.5,h=8.0);
    cylinder(d=5.9,h=5.7);
    cylinder(d=6.2,h=2.2);
    translate([0,0,-Protrusion])
        cylinder(d=6.2,h=2.2);

}
```
2024-10-01
Subaru Upholstery Peg
One of the flat-topped pegs anchoring the fuzzy black upholstery / carpet to the back of the rear seats went walkabout a while ago, but the situation only became critical after I vacuumed the crud out of the car.

Living in the future simplifies things:

Upholstery Peg – solid model

Rather than getting all fancy with barbed ends and suchlike, I just slathered the stem with hot-melt glue, jammed it in place, and waited a few breaths:

Upholstery peg – installed

The vivid yellow stuff is seat cushion foam.

3D printing is wonderful for simple parts like that.

The OpenSCAD source code is simple enough:
```
// Upholstery pin for Subaru back seat
// Ed Nisley KE4ZNU
// 2024-09-13

HeadThick = 1.5;
HeadOD = 25.0;

PegLength = 10.0;
PegOD = 8.0;
SlotWidth = 1.5;

rotate_extrude(angle=360,$fn=32)
    polygon(points=[[0,0],[HeadOD/2 - 1,0],[HeadOD/2,HeadThick],[0,HeadThick]]);

difference() {
    rotate(180/8)
        cylinder(d=PegOD,h=10.0,$fn=8);

    translate([0,0,HeadThick ])
        cylinder(d=PegOD/2,h=PegLength,$fn=8);

    for (a=[0,90])
        rotate(a)
            translate([0,0,PegLength/2 + HeadThick + 1.0])
                cube([SlotWidth,10.0,PegLength],center=true);

}
```
2024-09-26
Simpleminded Photographic Light Box

The general idea of a light box is (wait for it) a uniform background in a box full of bright light:

Light Box – overview

Obviously, this is a low-budget light box, but it makes perfect sense if you already have an essentially unlimited supply of moving boxes, 11×17 inch plotter paper, and a couple of photo / video lights lying around.

A two-layer cardboard ring glued to the top keeps the light from sliding off the box and stiffens the gaping hole letting the light shine through.

You’d normally use a fabric background to get rid of those ugly gaps around the edges and a larger box would be better, so this is along the lines of a proof-of-concept.

From the camera’s viewpoint, it looks better than my crusty desktop cutting mat:

Light Box – gears overview

Those gears would not look out of place in Bowman’s bedroom in 2001: A Space Odyssey.

In this day and age, you’d normally use a phone camera:

Light Box – gears overview – DOF

The lens on my Pixel 6a has a fixed focal length (around 4.4 mm = 27 mm equivalent) and a fixed f/1.8 (-ish) aperture, producing a razor-thin depth of field at the rear of the front gears. Note the fuzzy gears in the background, all of three inches away, and the slightly fuzzy front edge of the front gears. The camera’s digital zoom doesn’t help matters in the least, despite the AI-powered interpolation.

Keeping things close together helps, although the far end of the wipe towers and the rear of the gears lose detail:

Light Box – gears stacked

Looking from above also helps a little, but a top viewing port would reduce the skewed perspective:

Light Box – gears detail – DOF

Shallow DOF keeps your attention on the foreground, which is why real photographers use it for portraits:

Light Box – gears standing – DOF

The camera, an ancient Sony DSC-H5 with a zoom lens going down to f/8, still does nice work through a 2× macro adapter lens:

Light Box – gear detail – top light

The DOF is still narrow, but at least the entire front gear is in focus.

Adding a front light picks out the knurling:

Light Box – gears detail – front light

The results definitely look better than before, but it’ll take a bit of getting used to traipsing to the Basement Laboratory for every photo …

2024-09-23
Husky Workbench Caster Feet

The flat robot vacuum assigned to clean the floors around here would occasionally get stuck under the leg of my Husky workbench-as-desk and fail to complete its mission. Living in the future makes solving that problem a matter of minutes:

Husky workbench caster feet – installed

The upper rim captures the locked-in-place wheel in a 35×25 mm recess atop the middle 45×35 mm slab, with a 2.5 mm cork layer on the bottom. Laser-cut, of course, glued with ordinary yellow wood glue, and clamped for about half of a Squidwrench remote meeting.

Raising the desk by 5.5 mm gives the Flat One juuust enough clearance to scuttle under there:

Husky workbench caster feet – vacuum clearance

That was easy …

2024-09-20
Revised Measuring Spoon Drainer

A small tweak to the venerable spoon drainer adds a configurable cutout adapting it to a slightly different dish drainer rack:

Measuring Spoon Drainer – solid model

Which lets it snuggle into the corner:

Measuring spoon drainer – installed

Both the old and new racks had coated steel loops stuck into rubberoid feet perfectly suited to collect water and eventually rust the loops. Given a new rack, I figured potting the feet in JB PlasticBonder urethane adhesive would help forestall the rust:

Rubbermaid dish drainer – foot potting

I wish it were white, rather than black, but the only other color choice is tan and I can’t wish nearly that hard.

Along those lines, however, the gray JB Weld epoxy coating on the cheese slicer and the smaller repairs on the big knife are doing fine after years of use. JB Weld is good stuff!

2024-09-16
Prusa MK4 + MMU3 vs. Steamopus

So as not to bury the lede:

Steamopus – test pieces

The model is the Steampunk Octopus (in retrospect, the lower-vertex NixFix version should print better with its under-engine braces). The tests were to see how well its articulated tentacles printed and whether I understood how PrusaSlicer’s Multimaterial Painting worked. The answers: “Perfectly” and “Undo is my copilot”.

They’re both in PETG, with the orange eyes & features painted onto the STL model using the Smart Fill tool type to select surface facets joined within a given angle. Getting that right requires some fiddling, because you (well, I) can inadvertently select & flood a nearby area.

With Halloween fast approaching, they should be useful:

Steamopus – black at door

Readers of long memory will recognize the doorbell button.

The albino Steamopus looks downright weird:

Steamopus – white at door

Only the delivery folks have seen them so far …

2024-09-12
Double-faced DVD Coasters

Given an essentially unlimited supply of scrap CDs / DVDs (rendered unreadable by scarring the label side with a Guilloche pattern) and the failure of foam backing, it seemed reasonable to try sticking two of them together:

Double-faced DVD coaster – components

The fixture in the lower left is just an MDF square with a 15 mm post of more MDF glued in the middle to align the pieces. The white disk is the adhesive sheet, cut to 119 mm OD to leave half a millimeter clear around the outer edge, thus avoiding embarrassing stickiness.

Peel one side of the adhesive sheet and drop it over the post sticky side up:

Double-faced DVD coaster – adhesive sheet ready

Drop one of the DVDs over it, label side down:

Double-faced DVD coaster – first disc on adhesive

Lift it off, peel the other side of the adhesive sheet, put it over the post sticky side up, and drop the other DVD on top:

Double-faced DVD coaster – finished

The data side of the discs has a 0.3 mm raised rim just inside the track zone, so they don’t sit exactly flat on the table and expect a slightly concave lower surface on the mug / glass / cup. Neither of those seem like dealbreakers thus far, although I’m sure somebody will object.

A ring or two of general-purpose glue, along the lines of E6000 urethane, would be significantly less fussy than cutting adhesive sheets.

2024-09-10