Ed Nisley's Blog: Shop notes, electronics, firmware, machinery, 3D printing, laser cuttery, and curiosities. Contents: 100% human thinking, 0% AI slop.
Category: Software
General-purpose computers doing something specific
While swapping chuck jaws I realized I didn’t have to pile them on a shop rag atop the lathe headstock, no matter how neatly cut those rags might be:
Lathe chuck jaw holder – installed
It’s three layers of MDF cut to hold all six jaws from the 4 inch 3 jaw chuck, stuck together with wood glue.
You really need only four sockets: one empty for the jaw you just removed, then work your way around the chuck. But, hey, MDF is cheap and I usually remove all three at once anyway.
When it starts walking away, it’ll sprout silicone feet.
Mary’s ResMed AirSense 11 saves the data from every overnight breath she takes on an SD card, which she uploads to OSCAR once a week. I figured she needed an SD card to USB adapter / card reader of her very own:
The LightBurn layout is pretty much what you’d expect, with the letter inside the outline of the USB dingus on a tool layer to get the size right:
PU PSA Vinyl test – LB layout
The red layer is a “kiss cut” through the vinyl (remember: polyurethane) that leaves the backing paper mostly undamaged:
PU PSA Vinyl test – dot mode cut detail
The cut uses Dot Mode, with the laser firing at 10% power for 2 ms, spaced every 0.1 mm along the cut. I found 0.1 mm spacing produced a more-or-less continuous cut in the PETG sheet for the Tek Circuit Computer cursor hairline, but this picture shows it’s definitely running in pulsed mode. In any event, Dot Mode is the only way a 60 W CO₂ laser can make a kiss cut, as a normal vector cut can’t run fast enough to prevent cutting all the way through the backing paper, even at 10% power, around those letters.
The edges of the letters are slightly melted with a raised border, although they look pretty good if you’re not peering at them through a microscope.
I cut the rectangular outline with scissors, peeled the waste vinyl away, and weeded the ‘a’ with tweezers:
PU PSA Vinyl test – weeded
Stick a snippet of transfer tape on top:
PU PSA Vinyl test – transfer tape
In theory, the transfer tape sticks more firmly to the cut letters than the letters adhere to their backing paper, so peeling off the tape also peels the letters off the backing paper.
Which did not go well:
PU PSA Vinyl test – transfer tape – peeling
The two adhesions obviously require a delicate balance to work properly and I would be unsurprised to learn different transfer tapes behave differently on each type of vinyl sheet, with no way to know the results without trying every possible combination.
A few retries got the “r” back in position on the transfer tape, but a bit of kink remains in the “M”.
A third adhesion balance occurs between the transfer tape and the USB card reader, where the tape must stick to the letters slightly less than the letters stick to the reader. Burnishing the tape + letters to the reader encouraged the letters to stick and the tape pulled off without dislodging them.
We deemed the result good enough for the purpose and the process taught me a few lessons along the way. Next time, maybe it’ll work out better.
A recent Squidwrench meeting provided the opportunity to make a couple of racks for an assortment of Refresh Tears / Liquigel bottles:
Refresh eye lube – storage cases
I used chipboard to find out if the cross plates would stiffen the floppy 1.1 mm sheets enough for this light duty. Indeed, the overall structure becomes a nice rigid box, even though the feet and corners can’t withstand much abuse.
The finger joints use the default settings, which produce a lot of fingers along the edges. This turns out to be a Good Thing, as it gave the yellow wood glue plenty of opportunities to bond the sheets together.
Combining the default 5° slope with nine bottles along each level wastes a tremendous amount of vertical space. The adjacent racks hold three much larger cans per level, so roughly the same space doesn’t look like much. In retrospect, a 3° slope should work for smaller bottles.
And, yes, the squash on the lower shelf store nicely and become yummy meals all winter long.
Long ago, I gave Mary a box of 100 empty bobbins for her Kenmore 158 sewing machine, with the intent she would never again have to unwind a bobbin to put new thread on it. This worked so well I did the same thing for her Juki, with the result she needed somewhere to store all those filled bobbins.
Her work table has a shallow drawer, so we tried this out:
Watching all those little rectangles fall out just never gets old:
Bobbin Storage Case – cutting detail
I ran off a test tray in ordinary chipboard that works just as well, but lacks the pleasant appearance and feel of the TroCraft. Clear 1.5 mm acrylic would probably work, at the cost of requring a much neater glue job where the dividers meet the walls.
The spacing is a bit tight to pluck a bobbin from its slot between two others, but now she has enough space to arrange them as needed, with empty spaces around the most-used colors. I offered to carpet the drawer with bobbin trays, but she suggested waiting until these fill up.
As practice in using the laser to engrave a figure to a known depth, this seemed appropriate:
Envelope Opener – original
The black envelope opener on the right came in a long-ago surplus deal and worked really well, which I cannot say for the retail replacements I got a few years back.
The tan envelope opener on the left is an obvious case of IP theft, copying the size and shape using a scanned image:
Classic opener – knife blades – scan
The two blades seemed like good candidates, with the lower one winning the contest:
Kobalt 78010 Mini Utility Knife Blade mask
Although the pack of “mini utility knife blades” sports a Lowe’s Kobalt part number, they no longer carry that item. You can find plenty of identical blades elsewhere, so they’re not a rare collectible and I have plenty of backup.
Put the outline of the opener on a cut layer, put the blade on an engraving layer, orient appropriately, and make a mirror-image duplicate:
Envelope Opener – LB Layout
The original opener is a touch over 3 mm thick, so the settings engrave 0.25 mm into the surface to make a blade pocket, then cut the shapes from 1.5 mm TroCraft Eco:
Envelope Opener – cutting
After all the cutting was done, it looks about as you’d expect:
Envelope Opener – interior layout
Slather with yellow PVA wood glue and apply too many clamps:
Envelope Opener – clamping
Next time around, I’ll round off the edges before assembly, but that’s in the nature of fine tuning:
Envelope Opener – detail
The TroCraft sheet engraves so cleanly that, were I to go into mass production, I’d set up a fixture for grayscale engraving shaping the perimeters.
Obviously, this makes no economic sense, but it does produce a considerable amount of satisfaction, which is pretty much all that matters for such things.
The outline traces a scanned image of my father’s tag, fitting a few hand-laid splines around the curves:
John Q Public – WWII dog tag – spline curves
I generated a random serial number based on my father’s draftee status (he was in his early 30s during his South Sea Island tour) and state of residence; my apologies to anyone carrying it for real. His blood type was A and (I think) the religion code marks him as “Brethren”, a common group in my ancestry.
Given the outline, various plastics, and a laser, other effects become possible:
The Smell of Molten Projects in the Morning 
