Ed Nisley's Blog: Shop notes, electronics, firmware, machinery, 3D printing, laser cuttery, and curiosities. Contents: 100% human thinking, 0% AI slop.
Some geometry review and a bit of fiddling with LightBurn produced regularized patterns suitable for laser cuttery:
Danger Zone Earrings – radioactive – handful
A key trick: circumscribe the figure with a circle on a tool layer, then group the whole mess together, so that the center of the circle coincides with the desired center of the figure. In particular, the geometric center of an equilateral triangle is not at the center of its vertical extent:
Danger Zone Earrings – radioactive – LB layout
The dark blue layer engraves the surface, the red layer cuts through 3 mm acrylic, and the light blue layer is the tooling.
I like the edge-lit ones, although the simplicity of laser-cut clear acrylic is hard to beat:
Danger Zone Earrings – radioactive – white light
Wearing them in a place flooded with UV radiation would set you apart:
Danger Zone Earrings – radioactive – GITD UV
The careful observer will note stress cracking in the two clear earrings in the middle row. Those came from the vintage paper-covered acrylic sheet and I used alcohol to clean off the not-quite-vaporized glue just to see if isopropyl alcohol would behave differently than denatured alcohol. Nope, the cracks appear instantly.
Peeling the paper and engraving the bare surface produced the clear-frosted earring in the upper right, with the radiation symbol cut out of the sheet. Engraving without surface protection tends to deposit vaporized acrylic dust everywhere, so it would require hand cleaning without the cutouts.
The cutouts get 0.1 mm inward offsets to slightly increase the wall thickness around that central circle.
One combination I didn’t try: engrave the triangle perimeter for emphasis and cut out the symbol for contrast with edge-lit acrylic.
Dropping other symbols into place should be straightforward, with the center of the circumcircle as the snap target.
Then I traced them into LightBurn vectors suitable for engraving, added hanging holes, and fit a perimeter cutout. This being a test, I took a number of shortcuts resulting in slightly off-center engravings and ignored a number of image botches (most notably in the Inconsistent Topology figure.
A quick painting fixture kept (most of) the rattlecan paint off the edges:
SCP Warning Labels – fixture clamping
The acrylic is old enough to have brown paper protective layers, rather than fancy plastic sheets. I peeled various combinations and shot various sides with purple:
SCP Warning Labels – purple coat
Remove some, flip others over, and hit ’em with yellow:
SCP Warning Labels – yellow coat
I expected purple markings over a yellow background to look best:
SCP Warning Labels – purple over yellow
But the inverse version seems more contrasty (ignore the off-center cutout):
SCP Warning Labels – yellow over purple
I think the purple-on-clear version would look better with edge-lit acrylic:
SCP Warning Labels – purple over clear
The 0.15 mm line spacing seems too coarse, but trying to get a perfectly flat engraved bottom seems futile.
A second coat of paint on the engraving would definitely boost the contrast.
If you were going to do this for real, you’d definitely recreate the images with vectors right from the start, using the original images as inspiration.
All in all, I like ’em, but there’s some improvement required before anybody else does!
Using Bash arrays is an exercise in masochism, but I got to recycle most of the oddities from the previous script, so it wasn’t a dead loss.
The cameras use individually unique / screwy / different filesystem layouts, so the script must have individual code to both copy the file and decapitalize the file extensions. This prevents using a single tidy function, although laying out the code in case statements keyed by the camera name helps identify what’s going on.
My previous approach identified the MicroSD cards by their UUIDs, which worked perfectly right up until the camera reformats the card while recovering from a filesystem crash and installs a randomly generated UUID. Because there’s no practical way to modify an existing UUID on a VFAT drive, I’m switching to the volume label as needed:
In particular, note the two UUIDs for the M20 camera: there’s a crash and reformat in between those two lines. The two C100 cameras started out with labels because the M20 taught me the error of my ways.
The script simply iterates through a list array of the cameras and tries to mount the corresponding MicroSD card for each one: the mount points are cleverly chosen to match the camera names in the array. Should the mount succeeds, an asynchronous rsync then slurps the files onto the bulk video drive.
With all the rsync operations running, the script waits for all of them to complete before continuing. I don’t see much point in trying to identify which rsync just finished and fix up its files while the others continue to run, so the script simply stalls in a loop until everything is finished.
All in all, the script scratches my itch and, if naught else, can serve as a Bad Example™ of how to get the job done.
A picture to keep WordPress from reminding me that readers respond positively to illustrated posts:
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Cutting or engraving patterns on earrings should go more smoothly with a fixture:
Earring fixture – demo install
That’s a serving suggestion, using the Biohazard test pieces, which also helped align the top and bottom layers while gluing:
Earring fixture – clamping
That used all my little clamps: obviously I need more!
The bottom layer (red) is MDF for strength and the top layer (orange) is chipboard because that’s all it needs:
Earring fixture – LB layout
The little tab along the top ensures alignment using the jump ring cutout. The central hole will let me cut through the earring, should that be necessary.
The two strips over on the left get glued on the bottom, spaced to align along one of the aluminum knife blade rails, as with the craft stick fixture. With that lined up, any two of the four targets will serve to align the template with the fixture using LightBurn’s Print-and-Cut tool, as with the craft stick template.
The fox caught what looks like a small groundhog for supper:
IM_00307 – Fox with supper – 2023-05-25
The tom turkeys have been forming and re-forming their groups:
IM_00178 – Turkey parade – 2023-05-24
The gray cat may have spotted breakfast out there in the yard:
IM_00112 – Gray Cat – 2023-05-23
We haven’t seen a raccoon stand up like this before, so something must be very interesting out there:
IM_00089 – Standing raccoon – 2023-05-27
Off to its far right, Mary had fertilized a new pepper planting, which evidently smelled good enough to motivate vigorous digging. None of the plants sustained damage, despite being tossed around, but dexterous paws were surely involved!
An unfortunate confluence of weather, schedule, and enthusiasm led to mowing all the yard in one session:
Mowing pattern – 2023-05-27
I managed to remember to pause the tracker during a break in the middle, so it’s really just shy of three wall-clock hours from start to finish. It’s amazing how much work you (well, I) can get out of 100 mg of caffeine.
Despite what you see here, the path on what’s euphemistically called “our lawn” show a much more organized solution to the problem of covering our property with non-overlapping foot-and-a-half stripes. As with my leaf-shredding track, I neither venture into the road nor mow the neighboring yards.
That’s built directly from the original specs to get the spacing and symmetries correct. The freebies I could find all suffered from various degrees of bad design & layout.
Shrunken down to 25 mm OD, the tips become vanishingly small:
Biohazard earring – vinyl sample
It’s the same laser-safe polyurethane vinyl as the SD card reader, this time applied to 3 mm black acrylic. The “gold” ring is just parked in place, as this one wasn’t presentation-quality.
Contrary to the usual transfer-tape method of applying PSA vinyl, I stuck the sheet to the acrylic before cutting, then weeded it directly off the acrylic:
Biohazard earring – vinyl weeding
Kiss-cutting the vinyl with dot mode ate into the acrylic, but the soon-to-be-weeded areas protected the surroundings and the result came out looking pretty good. To me, anyhow.
Flushed with success, I tried some almost certainly not laser safe glow-in-the-dark tape:
Biohazard earring – GITD weeding fail
The mess in the upper left is the tape’s double-sided adhesive intended to hold the glowy layer in place forever. Of course it weeded poorly!
Seen in its natural environment, however, weeding may not be necessary:
Biohazard earring – GITD tape glow
Engraving the rebated rim leaves quite a bit of debris & scorch marks around the perimeter. A mask layer atop the GITD tape seems like a Good Idea™.
The Smell of Molten Projects in the Morning 
