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

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
Miniature Planetary Gear Bearings

Because it’s easy to scale solid models:

Small Planetary Gear Bearings – PETG PETG-CF

The small bearings are 25 mm OD, with correspondingly small clearances between their moving parts, but they all spun easily after a bit of breaking in.

As with their larger cousins, the orange PETG bearing has the most axial play and worked just fine right off the platform. The gray PETG-CF bearing was jammed and required concerted effort to get the gears rolling, but now has essentially no axial play while turning easily. The snappy-looking orange and black bearing has very little play and feels the best of the three.

The single-material bearings take about 20 minutes to print, while the mixed material one requires 80 minutes due to the extruder purging and nozzle clearing. The larger mixed material bearing took more than three hours, but time doesn’t scale as the cube of the size because changing materials runs at a constant time:

Small Planetary Gear Bearings – PETG PETG-CF with wipe towers

The smaller mixed gear produced the smaller wipe tower on the right, but changing materials remains an expensive process. Of course, if you were doing this in production, you’d make a couple dozen of the little things in one job: the machine would spend most of its time squirting out planetary gear bearings with the same number of material changes building the same size wipe tower.

They’re slightly too small for my fingers and surely pose a choking hazard to children, but they’re definitely cute.

2024-09-17
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
Planetary Gear Bearing Fondletoy: M2 vs MK4

It’s been about a decade since I made a batch of planetary gear fondletoys:

Planetary Gear Bearing – black red natural

So I loaded up the same STL in Prusaslicer and made three more:

Planetary Gear Bearing – M2 vs MK4

Both pictures show the same red bearing, done in PLA on the Makergear M2. The other bearings are PETG and PETG-CF on the Prusa MK4 + MMU3.

The blue bearing has about 5 mm of axial play, a bit more than the red.

The gray bearing is PETG-CF and has maybe 1 mm of axial play, which agrees with my original observation that an Extrusion Multiplier of 1.0 results in slightly overstuffed carbon fiber parts. It’s not much and, frankly, produces a better fit in this case, but it’s different than pure PETG. Which should come as no surprise, of course, given that it’s 15% carbon.

The gray-and-orange bearing looks spectacular in person and has about 3 mm of axial play, roughly the same as the red bearing, which you’d expect from overstuffed PETG-CF and pure PETG.

The single-color bearings print in about 1.5 hours and the two-color one weighed in over four hours. Multi-material objects are do-able, but you gotta want the results.

I told Prusaslicer to wipe the orange filament into the gray infill during color changes (per the Wipe Tower doc), but those two gray parts have so little infill as to make no difference:

Planetary Gear Bearing – PETG PETG-CF with wipe tower

The wipe tower in that posed photo has a nubbly texture because the filament just gets squirted without regard to anything other than maintaining the basic tower shape.

Seeing things appear on the platform never gets old!

2024-09-13
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
Razor Knife Blade Collet Repair

In the process of fixing something else, I discovered my favorite desktop razor knife had a loose blade. There being nothing like a new problem to take one’s mind off all one’s previous problems, I obviously had to fix it before proceeding:

Razor Knife – broken collet thread

Come to find out the plastic screw tightening the blade collet had snapped. The remaining stub stuck out from the red ribbed nut just far enough to prevent sliding the nut out of the black plastic body, but jamming a small screwdriver through the body got enough traction to unscrew the stub. It’s threaded 8-32, despite being old enough to be Made in Taiwan.

The red plastic feels like HDPE or a similar un-glue-able material, so it was going to need a mechanical splice. A tiny 2-56 setscrew falls in the class of things my buddy Eks describes as “If your design needs those, you’re doing it wrong”, but sometimes you gotta do what you gotta do.

For the record, a 2-56 setscrew requires a 35 mil hex wrench. My tiny ziplock bag with tiny hex wrenches has one:

Razor Knife – 2-56 setscrew

The little wrench in the background measures 28 mils for 0-80 setscrews, of which I have none and don’t expect to get any.

Anyhow, facing, drilling, and tapping the stub proceeded handily:

Razor Knife – setscrew in thread stub

You’d think I hadn’t faced off the end, but you’d be wrong. As far as I can tell, the end of the screw would be happy to break for as long as I’d be willing to try cutting it. Perhaps this indicates why it broke and suggests this repair will be temporary, at best.

Doing the same to the collet required a clamp to fit its slightly oblong body:

Razor Knife – laser-cut collet clamps

Those of long memory may recall the hooks.

Which then worked exactly as you’d expect:

Razor Knife – collet in lathe chuck

That’s aggressive stick-out for a little plastic rod, but sissy cuts saved the day; it faced / drilled / tapped easily enough:

Razor Knife – collet repair parts

Despite the non-glue-able plastic, I tucked some JB PlasticBonder into the recesses, screwed everything together, and coerced the 8-32 threads into alignment inside the plastic nut:

Razor Knife – collet thread alignment

Reassemble in reverse order after the adhesive set up:

Razor Knife – repaired

Done!

Now, what was I doing?

2024-09-11