Ed Nisley's Blog: Shop notes, electronics, firmware, machinery, 3D printing, laser cuttery, and curiosities. Contents: 100% human thinking, 0% AI slop.
I added a finger slot behind the front opening so I could pick up the whole stack at once:
Punched Card Trays – LightBurn layout
Admittedly, my “stacks” are nothing compared to the Bad Old Days, but …
The program adds a sequence number in columns 73-80 as a last-ditch effort to ensure the punch pattern matches the print pattern: after a few dozen cards, the digits in the last few columns become recognizable.
Creating a punched card with a laser requires a fixture holding the printed card-to-be flat and slightly above the honeycomb to reduce flash burns / schmutz on the underside:
Punched cards – laser fixture overview
A closer look while evaporating the holes:
Punched cards – laser fixture
The finger-crushingly strong magnets hold the fixture firmly to the (steel!) honeycomb, while allowing some adjustment. Unlike most fixtures, this one must slide around to align the printed targets with the laser positions; for reasons to be explained later, LightBurn’s Print and Cut alignment isn’t useful.
The pieces:
Punched Card Fixture
The top layout (on a LightBurn tool layer) matches the 1/3 Letter just-printed card, with targets bracketing the finished card outline. All the other pieces derive from those outlines with suitable offsets.
Glue the next three pieces together:
Chipboard extending a millimeter over the card edges to hold it down
Thin cardboard, about 0.6 mm thick, a millimeter beyond the card sides and flush with its top
3 mm MDF baseplate on the honeycomb
The card-shaped baseplate cutout lies 2 mm outside the card perimeter, for obvious reasons.
Set the laser speed / power so the blue lines on the baseplate mark the MDF for easy positioning of the cardboard spacer. The three parallel lines in front make it obvious when the card isn’t flush against the rear edge of the spacer; I’d only need one line if my paper cutter were perfectly calibrated.
The big blue rectangle on the bottom cuts a hole in a sheet of corrugated cardboard covering the platform, ensuring the air flows across the card and through the honeycomb behind the fixture; you want as little smoke hovering over the card as possible. The seam in my cardboard sheet was where they glued the box together; there’s no reason to be fussy with an air shield.
When the cutting is done, the finished card falls free:
Punched cards – laser fixture – cut
A snippet of masking tape helps extract the card without bending it.
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.
Although the larger fragments were still holding together when I laid them in their recesses, they apparently consist of several sub-fragments with larger continuous cracks letting the epoxy flow / ooze inside.
Now that I know what to look for, the original picture also shows them, albeit less distinctly:
Printed Fragment Coaster 165mm – overview
They’re not obvious in the scanned image of the fragments, although I could convince myself I see some:
Fragments 165mm square – scan sample
The many smaller fragments I’ve been turning into coasters probably separated from similar large chunks along such cracks, which is why I’ve never seen rivers of crack before.
Apologies if you arrived here expecting a tirade concerning the drug trade … :grin:
The next morning found it huddled against the cold:
Mantis – chilled
It had reached operating temperature and gone about its business a few hours later.
I deployed a cardboard Mantis in its honor as a seasonally appropriate yard decoration, but mine didn’t survive the night nearly as well as the real one:
The Smell of Molten Projects in the Morning 
