Ed Nisley's Blog: Shop notes, electronics, firmware, machinery, 3D printing, laser cuttery, and curiosities. Contents: 100% human thinking, 0% AI slop.
I planned to replace the vinyl straps on our set of (salvaged) lawn / patio chairs and made a pair of rivets for one long-missing strap:
Lawn chair strap rivets
The overall project is on indefinite hold, as a Steel-blue Cricket Hunter (*) has decided at least one of the chairs is an ideal place to start a family:
Lawn chair – wasp nest under construction
The patio under the chair is littered with blades of grass and twigs that didn’t quite fit through the 5 mm vent hole in the tube, but that long stem went in just fine:
Lawn chair – wasp nest grass stem
We have seen the wasp airlifting crickets near the chair, so provisioning has begun. The cricket seemed not only larger than the hole, but also larger than the wasp; we assume the wasp knows what she’s doing.
The new wasp will hatch this year, pupate over the winter, then hatch and emerge next summer, but I plan to replace the straps after the construction season ends.
I have no idea how to clean out whatever’s accumulating in there …
(*) I learned them as Steel-blue Cricket Killer, but the crickets are just paralyzed, not completely dead.
So, back to the Basement Shop, where a laser-cut and -engraved layout guide helps arrange and carry some suitable fragments:
Glass Coaster – Layout tray
As before, scan the bottom of the fragments and wrap selections around them:
Coaster Layout – selected fragments
Apply the usual operations to get a suitable mask:
Coaster Layout – fragment masks
Fire the laser to cut the chipboard test template holding the fragments, then a white octagonal acrylic base plate and a transparent acrylic layer surrounding the fragments, and:
Glass Coaster – base epoxy setup
Mix up some pourable epoxy, smooth it over the base plate, squish the transparent layer atop it, use the tape (sticky side up) to hold the two layers in alignment, and gently insert the fragments:
Glass Coaster – fragment epoxy
I eased some epoxy around the perimeter of each fragment with a pipette in an attempt to reduce the glass-sliver hazard:
Glass Coaster – fragment epoxy detail
Yes, that’s on top of the protective paper, because then I can whisk the paper off to reveal the pristine surface around each fragment:
Glass Coaster – fracture filling
As with the smaller coaster, the epoxy penetrates the fractures and reduces the shattered appearance. Mary suggests tinted epoxy would produce an interesting effect and I’ll try that the next time around.
Seen through the edge of the coaster, the uneven surface of the epoxy fill around the fragments shows up clearly:
Glass Coaster – fragment edge profile
The top of the glass stands half a millimeter above the transparent acrylic. I knew that would happen and wanted to see how the bottom of the mug interacted with the epoxy-coated sides:
Glass Coaster – first test
As it turned out, the epoxy coating wasn’t quite good enough to prevent tiny slivers from chipping off and, in the cold light of day, the pale-green-ish tinted glass didn’t stand out well against the white background.
So I taped up the perimeter, leveled the base, mixed up another batch of epoxy, added two drops of opaque black dye, and poured just enough to level the surface with the glass:
Glass Coaster – black epoxy pour
Introducing the meniscus to Mr Belt Sander put a bevel around the edge and finished it off well enough:
Glass Coaster – second test
The Squidwrench logo looks a bit battered after three and a half years of trips through the dishwasher, although I didn’t expect it to last nearly this long.
There’s still a slight upward tilt around the perimeter, but it meets my simple requirements and the fragments definitely look better in black. The white base sets off the fragments, but a clear plate takes advantage of their transparency; a mirror sheet might be even more interesting.
If you’re a particularly sharp person, these may accentuate your wardrobe:
Earrings – 12mm – finished
They’re fragments of smashed tempered glass, epoxied into laser-cut disks, with a ring providing some structural support. Although it’s hard to tell from the photos, the fragments sit flush with one side of the disk, which is likely the side you want closest to your carotid artery:
Earrings – 12mm – finished
Each chunk consists of a few smaller cuboids, so you get internal reflections from the minute air gaps between them. They’re not diamonds, but they’re surprisingly glittery in the proper light. Bonus: you can see right through!
The “gold” band around the disk is a beading ring held in a notch engraved around both disks:
Earrings – rings
The smaller ring is 12 mm OD, the larger is 25 mm, with 16 mm (the descriptions says 15, but ya get what ya get) and 20 mm available for other glass fragment sizes.
The engraved recess (green) is slightly larger than the OD to allow the perimeter cut to proceed through a thinner section:
Earring templates – 25 20 16 12 mm
Cross-hatch engraving puts a steep edge all around the recess, so the ring fits with just a little slack and turns freely around the disks.
You will, of course, have different glass fragments requiring different shapes, but the outlines came from the same process I used to make the palette organizing the fragments:
Smashed glass palette – fresh cut
You (well, I) can just import that layout, copy the outline of the chunk to be used, then delete the rest. Mirror the outline so the engraved sides of the disks fit together around the chunk, position symmetrically in the template halves, and fire the laser.
Affixing the fresh-cut disk and its glass chunk to a strip of Kapton tape (sticky side up) holds them in proper alignment and prevents the epoxy from leaking out the bottom:
Earrings – 12mm – taped
With everything lined up, run a small bead of epoxy around the chunk, squish the top disk in place, and line up the notches. When the epoxy cures, peel the earring off the tape and slide a jump ring into the notch.
As a finishing touch, you’d add a suitable ear hook or stud, but I think it’s fair to assume anything from Amazon would consist of the finest arsenic-plated plutonium and be completely unsuitable for skin contact. Neither of us have any piercings, so I cannot provide enticing action photos.
The 25 mm versions failed because I made the outlines such a snug fit around the chunks they didn’t quite fit:
Earrings – 25mm – failed
Protip: do not attempt to coerce two rigid bodies into alignment by applying firm pressure, particularly when one of them is already-broken glass.
The small earrings weigh 0.7 g each and a 25 mm one (well, the parts for a large one) comes in a bit over 3 g, plus whatever hardware goes in / on / around your ear.
This was (obviously) an exercise in small-scale laser machining, rather than a venture into haute couture. In the highly unlikely event you can’t live without a pair of custom-designed high-impact earrings, I’ll shut up and take your money … let me know if you want little or big. Black is the new black; I do have other colors, but who are you kidding?
Blow out the contrast, flip right-to-left, then mask them en masse:
Small fragments – masked
Delete the images (inside their selection masks) to create a binary mask:
Small fragments – masks
Have LightBurn trace the binary images, wrap a rounded rectangle around the lot of them, duplicate the rectangle as a base plate, then fire the laser:
Smashed glass palette – fresh cut
They’re not secured in their sockets, but they won’t fall out unless I fat-finger the whole affair:
Smashed glass palette – loaded
The thing that takes getting used to: the whole process was about two hours of wall clock time from start to finish, with a leisurely breakfast and KP in the middle.
Lay some pieces atop an acetate sheet (to prevent scratching) on the scanner, grab the whole thing, then isolate an interesting chunk:
Smashed Glass – dark – piece 1
Next time: flip the image left-to-right to match the glass piece as seen from the top, because the scanner was looking at the bottom.
The weird purple background started as black, but blowing out the contrast while ignoring the color mis-correction makes the next step easier.
Trace around the perimeter with Scissors Select, clean up the result in Quick Mask mode, expand the selection by a few pixels to improve clearance, then turn it into a two-color image mask:
Smashed Glass – piece 1 – outline
Import the mask into Lightburn, trace it into vector paths (which is trivially easy and accurate given such a high-contrast image), then cut a chipboard prototype to make sure it fits:
Smashed Glass – piece 1 – acrylic mount
Clean up any misfits, test as needed, cut the inner shape and outer perimeter from 1.5 mm black acrylic, cut just the outer perimeter from 3 mm clear acrylic. Put the piece of black acrylic matching the glass shape into the scrap box.
Mix up a few milliliters of clear pourable epoxy, butter up the clear acrylic, lay the black acrylic on top, line up the edges, then gently place the shattered glass into the cutout:
Smashed Glass – piece 1 – acrylic top
Next time: apply gentle pressure, perhaps through a flexy sheet, to ensure the entire glass surface contacts the epoxy layer while squeezing out the bubbles. This will surely skate the glass across the acrylic, so don’t leave it unsupervised.
The relatively clear areas show where epoxy eased its way into the cracks between the granules; there is no correlation between the air bubbles and unfilled cracks. The epoxy had the viscosity of warm honey and I didn’t expect it to flow so easily, but it doesn’t affect the outcome.
Wait for a day, no matter how hard that may seem, for the epoxy to cure. Leave the small cup holding the remnants of the mixed epoxy nearby so you can test the cure without disturbing the Main Event.
The bottom looks pretty much like the top:
Smashed Glass – piece 1 – acrylic bottom
The shattered edge reflects off the bottom of the clear acrylic, as seen through the side:
At first we thought a mighty crunch in the morning meant the trash collection truck had dropped a garbage bin from a great height, but the sound of sirens and a myriad flashing lights revealed the true cause in our neighbor’s front yard:
NHR Crash – frontal view
The extent of the damage was more apparent from the road side:
The driver was walking around uninjured and the ambulance left quietly.
A day later, the trajectory became apparent:
NHR Crash – trajectory
The right side barely kissed the tree on the right, but the front wheel hooked the utility pole (that’s the new pole in the picture), snapped it off at ground level in addition to the usual break maybe ten feet up, and bounced a piece off the other tree:
NHR Crash – utility pole
I didn’t know you could shatter a cast aluminum alloy wheel, but the missing half of the outer face was lying amid the rather scrambled stone wall along driveway.
We’re reasonably sure we know the cause. Feel free to draw your own conclusions.
After the flatbed hauled away the car and everybody left, I harvested a few pounds of interesting debris from the lawn:
NHR Crash – tempered glass
It’s tempered glass from the driver-side windows, shattered into small chunks and barely hanging together in those sheets. Laminated windshield glass is entirely different stuff.
The smaller chunks glitter like jewels:
NHR Crash – tempered glass fragments
Obviously, the window had a bit of tint.
The smallest chunk, seen from its flat surface, shows the cuboid fragments:
NHR Crash – tempered glass fragment – front
A side view shows more complexity:
NHR Crash – tempered glass fragment – side
Tempering prevents a glass sheet from shattering into long knife-blade shards. Although the edges of the fragments are not keen, we are dealing with broken glass: they are sharp.
Broken tempered glass also sheds razor-edged flakes perfectly shaped to penetrate bike tires, although most roadside glass comes from ordinary beverage bottles. The tiniest flakes can make a mess of your eyes, so exercise at least some rudimentary shop safety practices.
Those slabs ought to be good for something, even if they fall apart at the slightest touch …
The Smell of Molten Projects in the Morning 
