Ed Nisley's Blog: Shop notes, electronics, firmware, machinery, 3D printing, laser cuttery, and curiosities. Contents: 100% human thinking, 0% AI slop.
The black-on-white look come from vinyl PS atop GITD tape atop some transparent red acrylic, which looks a whole lot better in its natural environment:
SCP Earrings – GITD in action
Making those ten samples requires 15 minutes of laser time (mostly kiss-cutting the patterns at maybe 5 mm/s) and another 25 minutes of weeding and primping. I’m not convinced this is an economically feasible activity, but I really like the results.
A small coaster laser-cut from scraps of EVA craft foam:
Biohazard foam coaster
It’s all of 60 mm OD, so not particularly practical, but it (and its predecessor, a complete botch) helped show the laser kerf in EVA foam is an astonishing 0.6 mm, when cut at 125 mm/s with maybe 30 W.
The white outer shape is the nominal size, so holes are 0.3 mm larger on all sides than the pattern. The tan inner shapes get a 0.6 mm outset (!) to make them larger, which definitely squared up the horn tips. The fit is snug, but another 0.1 mm might be even better.
The pieces stick to a 60 mm circle cut from cork with a PSA layer, which makes it entirely too bendy.
If you wanted to do this for real, all the patterns would require tweakage to make the smallest features about 2 mm. The huge kerf ate the 1 mm struts around the central white disk and the tan circles should clear the horn stems by 1 mm, so that’s just barely enough.
The faint blue corresponds to the LightBurn tool layer, because you’ll want to assign your own cutting parameters.
The circumscribing circle provides a convenient way to snap the pattern into something else, because the symbols in the middle are not necessarily centered around their geometric midpoint.
Suiting action to drawings:
SCP Earrings – black on yellow – cutting
The acrylic fire shows they’re called Danger Zone earrings for well and good reason!
Anyhow, weeding the black vinyl produces crisp results:
SCP Earrings – black on yellow – overview
The fallout shelter symbol (top right) should have a circle around it, but that’s in the nature of fine tuning. It’s also not part of the SCP canon, but it kinda goes along with the radiation warning sign.
They’re cut from transparent amber non-edge-lit acrylic with black vinyl PSA patterns:
SCP Earrings – black on yellow – detail
Still not enough to get me to go full-frontal Mr Clean.
I have no explanation for the different stroke widths, other than that SVG files seem to maintain a memory of every transformation applied to any object. LightBurn doesn’t use the stroke widths, so it should work out just fine.
One of the Dripworks Micro-Flow valves in Mary’s garden started spraying water through the mold mark in the middle of the bottom:
Dripworks valve – bottom view
The autopsy produced a handful of pieces and inconclusive results: no visible holes or cracks.
Having replaced it with a new (and drilled out) valve, I scanned the underside of the severed valve knob, blew out the contrast, imported it into LightBurn, and got a reasonable approximation to the outline:
LightBurn geometry over image
A few more tweaks, weld the outline together, add some markers, and it’s ready for cutting:
Dripworks valve helper – LB layout
Having just done some earrings with PSA vinyl figures, I changed the (green) engraved layer to a kiss cut and Fired The Laser:
Dripworks valve helper – cutting
The mess in the vinyl around the through cuts in the ¼ inch acrylic sheet suggest engraving will work better. Lesson learned.
A few minutes of weeding produced a finger-friendly helper with scorches around the central ends of the vinyl:
Dripworks valve helper
But it fits right over the knob, which was the whole point of the exercise:
Dripworks valve helper – in use
Now Mary can adjust the valve without squinting at obscure black-on-black shapes atop the knob.
I decided keying the helper to the knob so it fit in only one orientation on the knob would be a hindrance, because there’s no easy way to determine their mutual orientation without the aforementioned squinting. Now it’s a matter of putting the helper over the knob, turning it at most a quarter-turn until it drops around the knob, then making another quarter of a turn to put the other red marks parallel to the hose: if it was on, it’s now off, and vice versa.
After the PSA vinyl peels away, I’ll make another one with engraved lines and any other improvements.
Danger Zone Earrings – GITD and PSA vinyl – UV light
And UV powers up GITD tape something fierce:
Danger Zone Earrings – GITD radiation
Cutting the central pattern out of the GITD earring might make it look even better, but I like the subtle presentation.
If it’s flash you want, then retroreflective tape is your fashion friend:
Danger Zone Earrings – retroreflective
The bolder kiss-cut lines in the middle earring might suffice, but the cutouts on the right definitely look more distinctive. Perhaps the kiss-cut perimeter line would set the pattern off a little better.
Assuming PSA vinyl sticks to itself and GITD tape well enough to survive normal handling, that would make multicolor earrings an option:
Danger Zone Earrings – multilayer PSA vinyl
On the left: blue PSA vinyl on GITD tape. On the right: green PSA vinyl on red PSA vinyl on black acrylic. Peeling the PSA vinyl is tedious and I’m still not good enough to avoid small nicks in the underlying layer.
Draw a 42 mm circle, set the layer to cut corrugated cardboard, turn the circle into suitable arrays, flatten some boxes from the heap, and Fire the Laser:
Seedling starter pot bottoms
Collect the fallen disks from the chip tray and jam one in place as a serving suggestion, where it fits like it was custom-made:
TP roll seedling starter pot bottom
You’d still want to fold some flaps over the disk to keep it in place, but now your pot has a real bottom.
I have no idea if 42 mm is a Galactic Constant, but it worked for the pile of tubes we had on hand.
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.
The Smell of Molten Projects in the Morning 
