The Smell of Molten Projects in the Morning
Ed Nisley's Blog: Shop notes, electronics, firmware, machinery, 3D printing, laser cuttery, and curiosities. Contents: 100% human thinking, 0% AI slop.
They might be Art
After more-or-less constant use under a cup in the bathroom, a Snowflake Coaster has reached the end of its life:
The acrylic flake is fine, but the wood has mildewed:
It’s second from the left in the bottom row:
All except the pair in the left column had a coat or two of rattlecan clear, which suggests wood-ish coasters need something much more durable, along the lines of clearcoat epoxy. No surprise there!
Ordinary potatoes are photosensitive and turn green & bitter when exposed to light, so Mary stores them in a paper bag in the pantry. I recently re-found the cupcake / bread box previously used for battery storage and we decided it would make a great potato storage box:
It does look like a little garage with a roll-up door, doesn’t it?
The engraving on the top came from the New Garden Encyclopedia:
The larger spud definitely has The Stink Eye! Also: tusks!
Threshold the scanned image, edit out a few blemishes, and engrave it atop the box:
The result looks rather pallid, but this is not the place for fancy wood finishes.
The alert reader will note a purple sweet potato parked in there, but it’s close to the spirit of the thing.
Paper sheets must lay flat in storage, but it’s impossible to extract a single sheet from a tall pile. So I converted some moving boxes into stackable trays, each holding about a ream of paper:
The starting point is a stackable Universal Box from boxes.py, with one end reshaped to become a tray. One Home Depot Large moving box provides enough 4.0 mm cardboard to make four trays, with one side of the box left over for future projects:
The gray rectangle in the middle is the LightBurn workspace grid representing the 700×500 mm laser platform:
Contrary to the screenshot, I move all the layouts off to the side leaving the platform grid clear. The blue rectangles around the layouts represent the various box flaps / sides, so I can:
Ctrl-D to duplicate itP to put the duplicate at the middle of the platform gridCopious application of hot melt glue gloms all the pieces together.
I added support beams under the cardboard bottom plate:
A 2 mm arch in the top of those strips puts a camber into the sheet to counteract the natural sag from carrying five pounds of paper. The four trays at the far left lack that camber and cry out for a Mulligan.
Some day the Basement Shop™ won’t smell like a campfire.
The LightBurn SVG layout as a GitHub Gist:
With various iterations of the Letter sheet fixture in place, I made some layered paper “art” using metallic paper:
That’s the Pyrotechnics quilt block pattern.
This is the RGBY Subpixel pattern:
The dotted rectangle in the lower left corner is the (turned off) front light in my low-budget light box and the glare in the upper left comes from the overhead basement LED strip lights.
AFAICT, “metallic paper” consists of shiny aluminum film bonded to heavy paper / cardstock, with transparent colored film bonded atop the aluminum. The sheet is, of course, highly reflective, which looks dark unless it’s reflecting a bright surface, like the well-lit Sewing Room ceiling:
I made the bright Pyrotechnics block in the upper left with art paper that looks bright & cheerful in any lighting:
That’s the difference between specular reflectors and Lambertian reflectors.
I cut the metallic paper face-down in the fixture:
Although I’m underwhelmed by the metallic-layered-paper results, the stuff does make spectacular chaff:
I should give our neighbor’s two-year-old lad a gift box …
Making 200×200 mm layered paper “pictures” involved cutting the square blanks from 8½×11 Letter sheets, putting those blanks in a fixture to hold them flat, then cutting the layer patterns:
That worked well enough, but it occurred to me that I should cut the patterns directly into the Letter sheet, with a couple of tabs on each edge holding the square to the sheet so it didn’t fall free.
A cardboard prototype showed this would actually work, at least after I fixed the tab width to keep them from just evaporating:
The top and bottom strips of tape hold cardboard bars that flatten the slightly curled metallic paper. The tape on the sides holds the cardboard flat to the knife bars across the laser platform.
A few adjustments later, I had an MDF version:
Which fits atop the bars even better:
Cutting colored paper definitely makes for cheerful chaff!
The two bar magnets hold the fixture in place on the steel platform rim. The aluminum knife bars stand slightly proud of the steel, so there’s a 1.4 mm chipboard shim glued under the fixture to put it flat on the bars.
The opening is 10 mm smaller than the Letter sheet to support it all around. The recess is 1 mm larger than the sheet to allow for slight size variations, with an MDF ring flattening the sheet:
The four targets in the corners correspond to targets in the LightBurn template suitable for Print and Cut alignment:
The alert reader will note the fixture targets on the MDF fixture sit juuuust slightly to the right of where they are in the template. It turns out the targets cannot be grouped with anything else (or even each other), because when you select a target on the template for Print and Cut the center of the selection must match the location of the physical target on the fixture.
However, it’s convenient to have the rest of the template grouped into a single lump, so it’s painfully easy to select and move only the template while leaving the targets behind. It seems while setting up to mark & cut the template, I managed to click-n-drag the group a few millimeters to the left.
I eventually used Print and Cut to align the template and target with the corners of that MDF frame, re-engrave the targets at the correct locations, and scribble over the misplaced targets. If I don’t tell anybody, they’ll never know.
The LightBurn SVG layout as a GitHub Gist:
Having herded all the denizens of the Subpixel Zoo into one LightBurn workspace, framing them seemed appropriate:
We had some 18×24 inch frames which fit a standard construction paper size. The paper colors aren’t nearly as vivid as a real artist would want, but they’ll suffice for my simple needs.
Lay out a template and decide 180 mm blocks fill the frame:
Offse the blocks 2 mm outward for cutting clearance and make a fixture:
The outer rectangle matches a blank sheet of corrugated cardboard cut by hand to fit the platform. The inner rectangle marks a line around the 18×24 inch position of the paper, giving me a mark within which I can center the paper well enough by eyeballometric approximation.
Cutting the blocks and marking the lines produces the template:
It’s held in place by four finger-crushingly strong magnets. If I ever do this again, I’ll throttle back on the power for the corner targets, because the laser cannot reach the top speed marking the outline, so it cut through the top layer of cardboard at the targets.
The layers for the 8×8 versions have 170 mm blocks with all the colors properly separated:
Embiggen the blocks to 180×180 mm, rotate them to their new orientation, then snap them into copies of the new template:
I can only envision these things in the landscape orientation that will fit the laser platform, but you could build them in their final portrait orientation and rotate the result.
I put the template pattern in the middle of the LightBurn workspace and use Print and Cut to align the fixture with the corner targets. Then it’s just a sequence of laying a sheet of paper on the fixture, selecting the corresponding layout, hitting P to snap the layout to the center of the workspace, and Firing The Laser.
It’s not nearly as pretty as Mary’s quilts, but now I have a wall decoration of my very own.
A Hacker News discussion led to the Subpixel Zoo, which led to thinking the patterns might make interesting layered “art”. After fetching the *.webp images and figuring out how to persuade Thunar to display them, the next step was converting them into paths suitable for laser cutting.
Although the images are algorithmically generated in a common layout, figuring out how to get the outlines as paths seemed to require a journey into the depths of the Pygame library and that would turn into a major digression.
Instead, start with one of the webp images:
The deliberate blurring apparently simulates what you see in real life.
Import the image into LightBurn, which converts it to grayscale under the plausible assumption you’re going to engrave the image on something. Then:
Which eventually looks like this:
I made the final array absurdly large, cropped it with a square to match the template I used for the layered paper patterns, resized the result to be 170 mm on a side, then dropped the square into the middle of the template:
One gotcha: crop the subpixels on a Fill layer so LightBurn will close the truncated edges, then put them on a Line layer for cutting. The doc explains why, although it’s not obvious at first, as is the fact that you must delete the group of shapes outside the square before it looks like anything happened during the cut operation.
The resulting layout contains all the subpixel rectangles, so it’s what you want for the top black mask layer. Duplicate the pattern and delete the subpixels corresponding to each color, until you have one template for each of the Red / Green / Blue layers:
The blank over on the right is the Yellow layer, which does get a quartet of layer ID holes cut in the lower right corner.
Then it’s just a matter of cutting the blanks, locating the fixture on the platform, dropping the appropriate color sheet in place, cutting it, then assembling the stack in the gluing fixture:
It’s kinda cute, in a techie way.
I did a bunch of layouts, just to see what they looked like:
In person, the RGBY patterns look bright and the RGB patterns seem dull by comparison. I’m using cardstock paper, rather than fancy art paper, which surely makes all the difference.
The Smell of Molten Projects in the Morning 
