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

Punched Card Production
For reasons I cannot divulge at the moment, I have undertaken a project requiring Old School punched cards, although they will never be fed through a card reader. Because we live in the future, punched cards are no longer a cheap and readily available resource; I will always deeply regret trashing an entire box back in the day.

However, living in the future does confer some advantages:

Punched cards – Apollo 11 CM

The process involves a vast number of moving parts, not all of which I fully understand, but I can (generally) produce consistent results and that must suffice. This post is an overview; I will go into the moving parts in more detail so I can remember why I did what I did.

A Python program converts a line of text into an SVG file that contains either the card’s printable contents or the paths required to cut its holes & perimeter. A handful of command-line switches determines the outcome, so you run the program twice with different switches for each line of text to get a matched pair of SVG files.

A Bash script read a text file and hands each line to the Python program, producing two SVG files for each card. It then invokes Inkscape to convert the printable SVG into a PNG image, uses Imagemagic to composite the logo behind the card contents & scale the result to make my printer’s output match the laser’s dead-on positioning, then properly position the card image in a Letter-size PNG image that’s apparently the only way to print it accurately on a punched card:

Composited Letter layout – exvb-00000710-lt

That’s not full size.

N.B.: there’s no such thing as a blank card that will be punched later, because the printed card includes the text across the top. The program also suppresses the row digits where a punch will appear, thus making slight misalignments less painful and mismatched SVG files more obvious.

Print all the card images on precut 1/3 Letter size sheets of heavy cardstock:

Ext Verb cards – 0280 skewed print

Yes, the printing on the middle card is slightly skewed with respect to the precut card blank. The overall process must handle about two millimeters of positioning inaccuracy and whatever angular skew comes from the printer’s paper feed rollers / guides.

A ~~DOS~~ Windows BAT file feeds the SVG files with the holes & outline paths to LightBurn, one by one. No lie.

Put each printed card in a fixture and align its targets, whereupon LightBurn evaporates the holes and cuts the outline:

Punched cards – laser fixture overview

In my somewhat biased opinion, the results look good:

Ext Verb cards – 0270-0290 punched

The Python program also produces cards with test patterns useful for wringing out the process:

Punched cards – character tests

“Punching” a lace card is no problem and, given an all-blank text line, the result looks like a blank card:

Punched cards – lace and blank tests

If you happen to have a card punch, be my guest.

The source text for the cards comes from the Apollo Guidance Computer in the Apollo 11 Command Module, via an amazing GitHub repository. You can run a virtual AGC in the privacy & comfort of your own home.

Useful links:
- The KEYPUNCH029 dot font: thank you scruss!
- Punched card codes, of which I used EBCDIC, from a heroic collection of punched card information
- Baffling Inkscape command line doc
- Imagemagick command line options doc
- SVG doc from Mozilla
- svg.py library for making SVG files
- Python library doc
- Another punched card generator
2026-02-02
OMTech Laser Cutter: Custom Air Fitting Wrench

Changing the lens on the laser requires unscrewing the nozzle after removing the assist air fitting that collides with the focus pen holder:

Laser head – assist air vs focus pen

All the 12 mm open-end wrenches in my Drawer o’ Spare Wrenches being much too large, I finally got around to making a custom wrench:

Air fitting wrenches

The plywood wrench came from a traced scan of a similar wrench, then adjusting the jaw opening to 12 mm. It served to verify the overall shape & size, then became a template for the real wrench atop a scrap of 1/8 inch aluminum sheet with flaking paint.

Some bandsawing and filing later:

Air fitting wrench – at nozzle

A little wrench makes swapping the lens somewhat less tedious, which is a Good Thing™.

Protip: Remember to adjust the Focus Distance by the difference between the two lenses.

2026-01-30
Plywood Coaster Warpage

This is what happens to an uncoated plywood coaster with fairly deep laser engraving after about half a year of use:

Warped plywood coaster – front

The poor thing went all potato chip:

Warped plywood coaster – side

I swapped it for one with polyurethane sealant, much like those fancier coasters with the same layout, and we’ll see if it survives longer …

2026-01-27
Snow Day

Today looks like a good day to fire up the snowblower and clear the driveway:

Snow – 2025-01-26

One of the bolts holding the muffler on the engine worked its way past its rebuilt locking plate and will require attention before getting out there.

Fortunately, it looks like a good day for shop projects …

2026-01-26
Silica Gel Beads: Indicator vs. Water

Just to see what happened, I dumped a few of those beads:

Silica gel beads – 36pctRH ambient

Into a few drops of water in a bottle cap:

Indicating silica gel beads – saturated

After a few days, it was obvious only the larger beads changed color and, no matter what the description said, they were not going to become any color I would recognize as green.

While the larger ones did get darker, the smaller ones must have already been at their limit of adsorption and remained at the same shade.

For humidity levels under about 20%, I think changing the desiccant every month or so is the only way to be sure.

2026-01-23
Ortur YRC-1 Chuck: Tube Reinforcement

Tuck a neatly laser-cut disk into a flimsy cardboard tube:

Ortur YRC-1 – cardboard tube reinforcement

Put a big conical center in the tailstock:

Ortur Chuck Rotary conical center – front

Whereupon the tube remains nicely tubular on both ends and aligned along the chuck axis:

Ortur YRC-1 – chucked cardboard tube

Which is why you save all that scrap material …

Yes, it’s the core from a toilet paper roll, which is way cheaper than burning through tumblers / mugs / shot glasses / whatever while figuring this stuff out.

2026-01-22
Prusa MK4 Nozzle Tool Mod

Contemplating a 0.8 mm nozzle to print more-transparent things, I ran off an Official MK4 Nozzle Replacement Tool to stabilize the heater block while applying a wrench to the nozzle:

Prusa MK4 Nextruder Tool – without inlet scoop

For obvious reasons, it doesn’t fit with the inlet scoop I installed as part of blinging the MK4:

Prusa MK4 Nextruder Tool – inlet scoop installed

Removing the scoop is a matter of removing those two cap screws, which is no big deal, but a little flush-cutter action made that problem Go Away forever:

Prusa MK4 Nextruder Tool – inlet scoop mod

Yeah, I should have modified the solid model. Maybe next time.

A version of the tool fits extruders covered with an Official Prusa Silicone Sock thermal insulator, but they were out of stock when I was in the mood. My heater wears a knockoff sock:

Prusa MK4 Nextruder Tool – silicone sock vs nozzle

Unlike the Official Sock, there’s no way to get a wrench on the nozzle with that one installed, but removing the sock is no big deal.

I apparently installed the nozzle / heater block slightly higher than specified, so the tool didn’t quite fit. Loosening those two thumbscrews and lowering the nozzle to fit the tool solved that problem. Fortunately, the automatic bed leveling routine corrects for nozzle height differences on the fly.

The scoop is back on the fan, the sock once again surrounds the heater, and I can easily swap in the 0.8 mm nozzle when the time comes.

2026-01-21