Category: Machine Shop

Mechanical widgetry

Clover Mini-Iron Holder: Revised

The 3D printed Clover Mini-Iron holder served well over the last decade (!), even after one of Mary’s buddies misplaced the iron during a quilting bee:

Clover MCI-900 Mini Iron holder – melted

She asked for a new holder that put the iron at a higher angle for easier gripping, which required only slight tinkering to boot the OpenSCAD code into the current decade:

Clover MCI-900 Mini Iron holder – higher angle

The letters stand one layer proud of the surface just to see what that looked like. I think it’s a nice touch.

The alert reader will note the cord end isn’t quite snugged into its recess. In normal use, the cord hangs over the edge of the sewing table and pulls the iron into place.

I embiggened the base to fit an aluminum plate from the stockpile, because that same cord tends to pull the holder around on the table. The plate puts enough weight on the silicone rubber feet to hold it firmly in place.

A layer of good double-stick tape strips bonds the aluminum plate to the PETG iron holder, after I once again discovered that craft adhesive sheets do not bond to PETG.

2026-03-17
Laser-Cut Egg Carton Sprouter
Mary has been using Styrofoam egg cartons to sprout seeds for this year’s garden veggies:

Egg carton sprouter – hand cut

I looked at those artisanal holes and offered to make sprouters with precisely calibrated laser-cut holes.

After the laughter died down, this happened:

Egg carton sprouter – lid detail

Each egg compartment has a drainage hole in the bottom:

Egg carton sprouter – on platform

The LightBurn layout has four shapes in three virtual arrays:
- Drain holes: 3 mm circle, 6×3 array
- Top vents: 25×15 mm oval, 2×1 array
- Side vents: concentric 3×4 & 2×3 mm ovals, 2×4 array
Which looks like this:

Egg Carton Sprouter – LightBurn layout

Because this isn’t a high-precision operation, I align the patterns to the carton using the camera:

Egg Carton Sprouter – LightBurn camera alignment

The two halves of the unfolded carton aren’t the same height, which means the top and bottom patterns have different focus levels and must be cut in two operations.

The laughter made it totally worthwhile.
2026-03-16
Monitor Arm Tilt Adjustment: Bad Part Repair

The tilt (it’s really “pitch”, but I can’t make a case for being that pedantic) adjustment on a recently arrived monitor stand / arm was nonfunctional, because the metal clamp had been bent about a millimeter too narrow to fit the plastic core. This is how it should look:

Monitor tilt adjustment – installed

As delivered, the plastic core was 32-ish mm wide and the gap at the base of the metal clamp was 31 mm, so the clamp arms stuck out at an angle on both ends of the core .

Because the cap screw bottomed out on the threads in the far side of the clamp, it couldn’t be tightened enough to force the clamp arms against the core.

Well, if the core is a millimeter too large for the clamp, shortening it should solve the problem; I can always shorten the screw if it comes to that.

Quick! To the mini-lathe:

Monitor tilt adjustment – lathe setup

Shaving half a millimeter from each side:

Monitor tilt adjustment – shaved

Twirling a deburring bit in each hole got rid of the swarf.

Rather than trimming the cap screw, a pair of fender washers keep it from bottoming out. With the core fitting into the clamp, the arms grip the core firmly on both sides with plenty of friction:

Monitor tilt adjustment – tweaked

I’ve bought this brand of arm before and the most recent pair have definitely been cheapnified from earlier ones. Because only one had a bad tilt clamp, the OEM may be in the middle of a changeover and shipped it with mismatched parts.

I wonder how many stands / arms get returned because they just don’t work?

2026-03-13
Alumina Desiccant: Regeneration Timeline
Having accumulated a suspiciously precise 700 g of activated alumina desiccant from the PolyDryer filament boxes, I poured it into the same cast-iron pan on the induction cooktop:

Alumina regeneration – induction cooktop

Based on the results from last time, I set the temperature to the cooktop’s maximum 460 °F and, bother fiddling with condensing the moisture on a lid, and let it cook.

Weighing the beads (about) once an hour:
- Start: 700 g
- 1 hr: 678 g
- 2 hr: 666 g
- 3 hr: 661 g
The 39 g water loss is 5.6% of the wet weight and 5.9% of the dry weight, which is roughly the amount absorbed by both silica gel and alumina after a month or so in the filament boxes.

During those hours the surface temperature rose from 73 F to 190 °F, although the exact number depends on exactly where the IR thermometer was staring. Stirring the beads to get an average temperature might be more convincing, but not by much.

Exactly how dry the beads become after three hours remains unknown, but the temperature increase suggests most of the water has gone elsewhere.

Cooling the beads in a covered bowl and pouring them into a jug produced a total weight of 767 g, which settled at 770 g over the course of two days; the jug seems reasonably vapor-tight.

Alumina beads seem much less prone to damage by overheating than silica gel beads and have similar performance in the boxes, which makes them a strong contender for the next round.
2026-03-12
Punched Cards: Apollo Eagle Card Layout
With some lessons learned from the first pass, the bottom layer of the Apollo Eagle gets a reversed card for the white tail feathers:

Apollo Eagle – Layer 1 card layout

Which looks like this just after cutting the outline:

Apollo Eagle – Layer 1 as cut

Gently removing the scrap from the edges reveals the eagle:

Apollo Eagle – Layer 1 cutout

The top two layers also come from a reversed card, with those shapes arranged to put the holes in attractive places:

Apollo Eagle – Layer 7 8 card layout

The five layers in between as a slide show:
Apollo Eagle – Layer 2 card layout
Apollo Eagle – Layer 3 card layout
Apollo Eagle – Layer 4 card layout
Apollo Eagle – Layer 5 card layout
Apollo Eagle – Layer 6 card layout
It took a while to get over cutting up all those nice cards.

Some deft glue stick work produces a layered eagle:

Apollo Eagle – assembly overview

I managed to get a dark bottom in the nostril, which turned out weird:

Apollo Eagle – head detail

All in all, though:
- Fewer layers are better
- The head came out OK-ish
- The bottom layer card arrangement is too fussy
- The olive branches still look weird
- The claws are still ugly
- The tail needs more contrast, perhaps two layers
- Having horizontal card splices aligned on successive layers is bad
More study is definitely in order …
2026-03-11
LED Garage Light: Autopsy

The hidden part of all three LED arrays in the dead garage light looked like this:

LED Garage Light – inadequate heatsink compound

Although the compound was still gooey, there wasn’t nearly enough of it. The few tendrils on the heatsink suggest the LED array had bowed upward, pulled away from the cast aluminum, and eliminated any direct conduction.

A bit of probing showed each LED array had 16 series groups of 4 parallel LEDS, with one group in each array failed open. That group was toward the end away from the inadequate heatsink compound: the LEDs died from heatstroke brought on by neglect.

The Drawer o’ LED Arrays disgorged a bag of surplus LEDs labeled “10 W 9-12 V 750 mA”:

LED Garage Light – epoxy replacement

It’s sitting on a generous blob of steel-filled JB Kwik epoxy that should do a great job of conducting heat. A bag of cheap constant-current supplies is on order.

Amazon has similar “10 W 9-12 V 350-450 mA” arrays.

Try as I might, I can’t get 10 W from those numbers, but I’ve never understood advertising math.

2026-03-10

Polydryer Humidity: February

After two months of sitting around:

	2026-03-07				2026-03-08
Filament	%RH	Weight – g	Wt gain – g	Gain %	%RH
PETG White	14	53.2	3.2	6.4%	10
PETG Black	14	52.3	2.3	4.6%	14
PETG Orange	24	52.1	2.1	4.2%	32
PETG Natural	18	52.6	2.6	5.2%	14
PETG-CF Blue	18	52.8	2.8	5.6%	14
PETG-CF Gray	18	53.5	3.5	7.0%	14
PETG-CF Black	14	53.2	3.2	6.4%	10
PETG Blue	10	52.5	2.5	5.0%	10
TPU Clear	18	52.7	2.7	5.4%	10
TPU Black	14	53.6	3.6	7.2%	10

The last three boxes had 50 g of activated alumina and got fresh doses from the same bottle.

The other boxes had 50 g from the original bottle of silica gel beads and now have regenerated (and likely damaged) silica gel beads.

AFAICT, the meter in the orange PETG PolyDryer box isn’t working right, because the humidity indicator card in there has blue spots all the way down to 10%, just like the other boxes. Color differences for meter readings in the teens may be too subtle for my eyes.

Next time around, they’ll all get alumina beads.

2026-03-09

Category: Machine Shop

Clover Mini-Iron Holder: Revised

Laser-Cut Egg Carton Sprouter

Monitor Arm Tilt Adjustment: Bad Part Repair

Alumina Desiccant: Regeneration Timeline

Punched Cards: Apollo Eagle Card Layout

LED Garage Light: Autopsy

Polydryer Humidity: February