Tag: Laser Cutter

This came out all glittery:

Epoxy tinted with transparent black dye does a pretty good job of not obliterating the cracks between the cuboids. In person, the cracks seem less conspicuous around the borders of the glass pieces, but they’re visible enough for this ahem use case.

Under the proper lighting, a few bubbles appear along and above the black layer:

The new thing this time around were three pins holding the layers in alignment while the epoxy cured:

The conical end comes from grabbing an 8 mm snippet of 3/64 inch steel rod in a pin vise and twirling it against Mr Bench Grinder for a few seconds.

The pins pretty much dropped into 1.1 mm holes created while cutting the sheets. The tiny circles mark the laser path around the pin holes:

The “holes” in the top sheet (upper middle) are in the Tool 2 layer so they’re not cut, because it was easier to match-drill holes halfway into the top sheet with the drill press than to figure out how to convince the laser to not punch all the way through. Engraving (along the lines of the earring borders) might work, but I’m not sure how well a high-aspect-ratio hole will engrave.

The mirror sheet is reversed left-to-right in order to cut it from the back of the reflective layer. I’m not certain this is necessary, because acrylic is basically opaque to 10.6 µm IR light and any doubly attenuated reflected light will diverge strongly from the focus point at the top surface, but it’s the recommended procedure and easy enough to do.

The cork cuts with its adhesive layer up and blue tape on the bottom to prevent soot from accumulating in all the surface crevices.

The alignment pins worked surprisingly well:

The top sheet sticks out 0.3 mm on one side:

Oddly, there’s no place where the top sheet is indented by any noticeable amount, so there may be slight size differences depending on all the colors and ages in that stack of plastic sheets.

I’ll cure the next one top-side down, giving the bubbles an opportunity to rise toward the mirror layer and maybe become less conspicuous:

The tricky part: finding and arranging glass chunks within a 100 mm circle!

Avoiding narrow gaps and acute angles in the perimeter, as the notch on the left side, should simplify draining the epoxy.

Snugging the perimeter around the smashed glass fragments definitely improves the result:

It’s just under 100 mm = 4 inch across the longest dimension and surprisingly glittery:

The coaster is a five-layer sandwich half an inch thick:

From the top:

• Clear acrylic: 1.5 mm = 1/16 inch
• Black acrylic: 1.5 mm = 1/16 inch
• Clear acrylic: 3.2 mm = 1/8 inch
• Mirror acrylic: 2.7 mm
• Cork: 2.7 mm cut from a standard round coaster base

The smashed glass pieces sit atop the mirror, so the trick is making the layers around it add up to the same thickness. This is not possible by adding the nominal dimensions, because cast acrylic sheet thickness isn’t well controlled; I’ve finally written the actual (metric!) thickness on the sheets so I can select which 1/8 Inch sheet has the proper thickness.

A chipboard template (seen atop the finished coaster) verified the glass pieces fit easily within their openings:

I laid the clear frame on the mirror, poured generous epoxy puddles along the middle of the fragment openings, eased the glass in place, and gently pressed the slabs down to get a uniform epoxy layer, with the excess oozing under the frame all around. Then lay the black frame around the glass atop the clear, squirt more epoxy along the gaps around the glass, pour more epoxy atop the fragments, ease the top sheet in place paying considerable attention to coaxing the bubbles along to the edge, align the sides, and wait.

The epoxy cured while stuck atop a styrofoam pillar to let it drain smoothly off the edges:

I encouraged the epoxy out of the acute corners, as shown by the larger puddles, over the next few hours until the epoxy stiffened up. Those puddles also show the transparent black tint, to the tune of four drops in 8 ml of epoxy, which turned out to just barely suffice for the job. The whole assembly sat level while curing, but the layers didn’t remain aligned even after gently shoving them around while the stack cured.

The black epoxy joins nicely with the black frame layer to conceal most of the remaining bubbles. A different color frame with matching epoxy might looks less ominous, but colors more transparent than dark gray would likely reveal the bubbles.

It Would Be Nice™ if the acrylic sheet on the top had a transparent plastic film cover, but it arrived with brown paper on both sides. Despite that, I spattered only a few tiny drops on the bare surface and managed to scrape most of them off without further damage.

Overall, I think the conformal perimeter looks much better than the polygonal outline smashed glass coasters.

The POC earrings had a pair of 1.5 mm acrylic disks epoxied around the glass fragment, with the “gold” ring captured in a rebate around the rims. That process was both tedious and messy, so I tried laser-engraving a deeper rebate into a 3 mm sheet, then epoxying the fragment and the ring in place:

They’re stuck to a strip of Kapton tape to keep the epoxy off the bottom surface of the glass, while aligning it with the surrounding disk.

Peeling the protective film / plastic off reveals the acrylic disk:

They all required more effort to remove the epoxy remaining around the ring, but it worked out better than I expected.

A lighter background shows off their internal structure:

A closer look at the pairs:

As always, glooping clear epoxy around the edges fills many of the internal cracks and reduces the glittery aspect of all those glass-to-air-to-glass interfaces, but I don’t see another good way to keep the fragments under control.

The results may not be up to a “fine jewelry” standard, whatever that may be, but a slipcase box definitely improves the presentation:

If I had the courage of my convictions, I’d go for the Mr Clean look myself, but …