Ed Nisley's Blog: Shop notes, electronics, firmware, machinery, 3D printing, laser cuttery, and curiosities. Contents: 100% human thinking, 0% AI slop.
Most of the PolyDryer boxes had the same humidity as before, so I didn’t disturb them. When the humidity starts to rise, then we’ll see what’s going on in there.
The PETG Orange meter continues to misbehave and has been glitching from 22% to 30%. The indicator card shows the humidity is around 10% inside and the relatively low weight gain suggests there’s not much water to be adsorbed.
The PETG-CF Blue spool is new and, once again, shows filament does not arrive bone-dry in the factory wrapper.
Those two boxes now have alumina beads.
Dehydrating the jar of wet silica gel on the induction cooktop (set for 405 °F) sweated it down from 532 g to 503 g over the course of four hours, with nearly all of that change in the first two hours.
Obligatory photo from a while ago, because it looks pretty much the same now:
Having admired the paper craft at RavensBlight and with some experience in simple paper cuttery, I had to try my hand at the Ghost Truck. Rather than using an X-Acto knife and straight edge around the perimeter, I set it up for laser cutting.
The instructions & layouts are images in PDF files, so it’s straightforward to import them into LightBurn and trace the outlines:
Ghost Truck – LightBurn vectors
Tracing produces short vectors and irregular curves:
You must manually add any cuts buried in the pattern, as in the Trailer Wheels parts shown above, so pay attention to the instructions.
Use the Move Laser tool to put the laser head at an obvious point on the layout, then skootch the printed page (in a Letter size fixture) to put that point under the beam. Repeat for another point, iterate until satisfied, then Fire The Laser:
Ghost Truck – cutout overview
Some irregularities peek around the edges:
Ghost Truck – cutout detail
On the whole, it’s much better than I could do with a knife.
Repeat for the other seven pages of parts:
Ghost Truck – Assembly
With some diligence I may have it ready for All Hallows Eve …
Although I got one of the screws out of the cover while modeling the knob, the other was more firmly implanted and resisted my entreaties.
However, having recently spotted the small tool kit accompanying the generator, should the knobs fall off again, I’ll forcibly remove the screws, put them in the tool bag, and rely on the snaps to hold the cover in place.
At last, I can make plausible-looking punched cards:
Test Card 3 – punched
Then chop most of them up to make a layered eagle:
Apollo Eagle – V3 – overview
Back in the beginning, the grand overview explained the card production process, but now I can pull all the blog posts into a more coherent story.
Start by making trays to hold the 1/3 Letter sized printed cards and the final cut cards. A coat of paint improves the result:
Card Storage Tray – front
Then make a fixture to position the 1/3 Letter printed cards in the laser and a simple cover for the honeycomb to direct the air flow:
Punched cards – laser fixture overview
The current versions of the Python program to convert a line of text into the SVG images required to print and punch the cards, plus the Bash scripts handling all the command line parameters, are now in a single GitHub Gist . I used the source code from the Apollo 11 CSM AGC for historic reasons.
The Bash scripts invoke the Python program twice to produce both the printed layout:
Punched Cards – test card – printed
And “punched” holes surrounded by the perimeter cut for the laser:
Because my printer produces slightly off-size printed images, the script uses Inkscape to convert the SVG into a PNG, then downscales the image by a few percent (a different percent on each axis). It composites the card logo onto the PNG and slams the result onto a Letter page in the proper place to hit the 1/3 Letter sheets.
If you must have a stack of punched cards on your desk, a nice tray does wonders for the office decor:
Card Storage Tray – overview
That’s a coat of Rustoleum Painter’s Touch 2x [many more adjectives] Kona Brown Gloss rattlecan paint atop Trocraft Eco board. I sprayed the separate parts on a sheet of newspaper, waited 20 minutes, flipped them over, sprayed the other side, gave them another 20 minutes, and got them inside out of the wind for a day of curing.
They’re held together by cyanoacrylate adhesive dots between the tabs, with accelerator daubed on the other side of the joint to encourage prompt curing. In general I do not like cyanoacrylate, but sometimes it seems like the right hammer for the job.
The perspective makes the dispenser look chonkier than it really is.
A wrap of black silicone tape around the spool embiggens it for a snug fit inside the tape core. A casual inspection of other tapes suggest enlarging the spool by a few percent would help, but it’s Good Enough™ as-is.
The two end thumbscrews fasten the 4×1 Gridfinity baseplate to the dispenser; both from Gridfinity Refined:
Gridfinity Tape Dispenser – baseplate
If I had my wits about me, I’d have used a nicely contrasting color for the baseplate, but it is what it is.
Although they’re called “thumbscrews”, the slot is sized for a US quarter (or cart coin).
An OpenSCAD one-liner produces an SVG model of the baseplate:
projection(cut=true) import("Grid 4x1.stl");
Import SVG into LightBurn, delete the magnet pockets, and Fire The Laser on some EVA foam:
Gridfinity Tape Dispenser – foam base
A layer of 3M 300LSE tape holds the foam in place, because neither side sticks well to the goo on a craft adhesive sheet due to their low surface energy. I stuck an oversize rectangle to the foam with the thin adhesive side before cutting, which required a second pass at higher speed.
The thumbscrews also close off the holes in the dispenser bottom through which I poured 275 g = 10 oz of sand for better traction. Steel shot is reputed to be Even Better, although most of the BBs are in the long-arm weight.
The dispenser model includes a printed serrated blade which works as poorly as the author suggested. A length snapped from an ancient Strombecker 4-I (“four eye”) blade in the Box o’ Big X-Acto Blades fits perfectly, works wonderfully well, and is sufficiently inconspicuous to warrant the warning label. An X-Acto #26 Whittling Blade would probably snap down equally well.
The small squares near the corners of the image appear on every layer to properly register all the eagle outlines.
Mirroring the layout produces the hole pattern as seen from the back side of the cards, where the tape is applied:
Apollo Eagle – V4 Layer 7 card layout – mirrored
Then it’s (relatively) easy to align the cards while muttering “the rightmost hole in the lower sequence number is just about aligned with the upper card edge, which puts the middle-ish hole in the group of four in the 9 row over the left hole of those two” and so on and so forth. Cut off a strip of tape, carefully lay it along the joint between the cards, and add them to the outgoing pile.
The top two layers are cut with the back = unprinted = blank side of the card upward to produce the eagle’s white head, with the outlines strategically located to avoid shredding the feathers with holes:
Apollo Eagle – V4 Layer 8-9 card layout
The value of this process becomes more apparent for the nine cards making up the bottom layer:
Apollo Eagle – V4 Layer 1 cards
Most of the white tail comes from the reversed card in the bottom row, inset into the two cards above it. The next layer covers those sections of the legs and olive branch, which is easy to confirm by aligning the layers using their border squares.
The layout mirrored for easier taping:
Apollo Eagle – V4 Layer 1 cards – mirrored
This is from a previous layout, but the improvement is obvious:
Apollo Eagle – V3 – tail
The trick with all this is to select only the eagle outline for cutting amid all the card details. Although putting the cards on a tool layer would avoid that problem, the holes are much less visible and they’re pretty much the entire point of this process.
Aligning the taped cards on the platform with the to-be-cut outline follows much the same process as aligning the printed cards for punching:
Select the cards and the eagle outline
Snap to the middle of the LightBurn workspace with the P key
Focus the laser on the cards if you haven’t already done so
Move the laser head to one of the card bevels using Ctrl-L and clicking on one end of the bevel
Skootch the cards to put that bevel at the red dot pointer location under the laser head
Move the laser head to another bevel
Skootch the cards as needed
Iterate until satisfied
Fire The Laser
Although each card layout has the four targets used to cut it from the printed card stock, those targets no longer exist on the cards because they’ve been cut off.
You could use Print and Cut to align the LightBurn workspace to the cards, but it’s easier and faster to just skootch the cards around.
Actually cutting the outline takes a few seconds and is kinda anticlimactic after all that setup.
The Smell of Molten Projects in the Morning 