Ed Nisley's Blog: Shop notes, electronics, firmware, machinery, 3D printing, laser cuttery, and curiosities. Contents: 100% human thinking, 0% AI slop.
We deployed low-effort vole trap boxes a few weeks ago, only to discover no voles checked in, most likely due to wintertime gardens consisting of bare earth. I had weighted the boxes with convenient rocks that pretty much crushed them flat during rainstorms.
So I converted a few dozen square feet of cardboard into better-looking boxes and transferred the traps:
Vole Finger Box – large
That one has a rat trap inside.
Smaller boxes hold mouse traps:
Vole Finger Box – small
Two pairs of 4 mm holes on the bottom flanges fit some spare irrigation pipe holddowns to, yes, hold them down, with those rotten planks keeping their lids in place.
They’re lightly customized “Electronics Boxes” held together by hot-melt glue. The jawbreaker URLs will get you started:
Our Young Engineer recently rebuilt the cover of a “vintage” drawing kit, with fabric pockets for protractors & scales and real leather hinges, thereby raising a long-procrastinated project to the top of my to-do list:
TEC Drawing Set – top old
I know my father used it when he took drafting after high school in 1929. His penmanship and drawing ability were up to par well before that.
The inside sports a TEC logo:
TEC Drawing Set – open old
Some searching revealed it’s a No. 718 Drafting Set from the Technical Supply Company of Scranton and appeared in their 1913 catalog:
TEC Brand Catalog p68
The printing on the inside of the flap differs, but the logo has TEC in the middle.
My father did not attend college and, in the teeth of The Great Depression, $26.50 was certainly too spendy for his family:
CPI Calculator – 1929 to 2025
When the catalog was printed in 1913, No. 718 cost the equivalent of $862.82. Nowadays, similar sets once again cost about twenty bucks on eBay, which tells you something about economics.
In retrospect, I should have used two leather snaps, but three would be excessive.
I folded the Kraft-Tex flat across a steel scale to make the first folds around the base, then finger-crimped folds at the top of the base with subsequent crisping around the scale:
TEC Drawing Set – open new
The underside of the original case seemed stable:
TEC Drawing Set – case bottom
This may be sacrilege, but I saw no point in peeling the bottom just to cover it up,so I stuck the Kraft-Tex in place with a rectangle of adhesive sheet.
It doesn’t look the same, but it still gives me a warm feeling.
It still has the tiny wrench needed to adjust all its screws:
TEC Drawing Set – wrench
It’s on 0.1 inch graph paper and is 40 mil = 1 mm thick, should you want to make your own. The blades taper down to essentially a knife edge, which is why it’s made from hard blue steel.
I remember being fascinated by that little pig when I was a pup.
Putting some scraps to good use, I stuck a cushion in the anvil for the next time I punch down a leather snap:
Having herded all the denizens of the Subpixel Zoo into one LightBurn workspace, framing them seemed appropriate:
SubPixel Zoo – wall hanging
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:
SubPixels – LightBurn 18×24 template
Offse the blocks 2 mm outward for cutting clearance and make a fixture:
SubPixels – LightBurn 18×24 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:
SubPixel Zoo – laser fixture and chaff
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.
Embiggen the blocks to 180×180 mm, rotate them to their new orientation, then snap them into copies of the new template:
SubPixels – LightBurn 18×24 layers
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.
I’m finallyassembling the shelves for the last of the boxes cluttering the basement floor. Because the top of the wire shelf grid sits 4 mm below the top of the shelf rails, surely for some good reason, that pale strip is a 6 mm shim raising the grid just enough to let the boxes slide easily off without having to lift them over the rail.
It’s a pair of 3 mm thick MDF strips stuck together with tapeless sticky (a thin adhesive layer on backing paper), with the same adhesive holding the shim to the rail while I lay them down and plunk the shelf grid on top:
Wire Shelf Shim – side view
I made two sets of shims to fit the support rod spacing, with lengths carefully chosen to match two stacks from my Big Box o’ MDF Cutoffs, all 10 mm wide to fit the shelf rails:
Wire Shelf Shim – laser cutting
Admittedly, not all of the neatly rounded corners came through, due to slight variations in MDF sizing / Print-and-Cut alignment / whatever, but it’s a nearly zero waste way to turn stock into strips.
Each shelf needs 14 shims = 28 strips and I’m here to tell you if I had to bandsaw 140 little strips for each of three sets of shelves, well, I:
Probably wouldn’t ever get around to making them
Definitely would grumble about lifting those boxes, forever
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:
sq_RGBY
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:
Create a rounded rectangle overlaying the lower-left-most subpixel to good eyeballometric accuracy
Turn it into a four-element rectangular array, twiddling the center-to-center spacing to match the subpixel layout
Duplicate those four upward in another array to create a subpixel block, as marked in the upper-left corner of the original image
Slam another array across the bottom row and upward, twiddling the spacing to match the subpixel block spacing along both axes
Which eventually looks like this:
SubPixels – LightBurn vector overlay
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:
Subpixel Zoo – Quattron RGBY – LightBurn black mask layer
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:
Subpixel Zoo – Quattron RGBY – LightBurn 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:
Subpixel Zoo – Quattron RGBY
It’s kinda cute, in a techie way.
I did a bunch of layouts, just to see what they looked like:
Subpixel Zoo – 8×8 layouts
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.
Both of those “projects”, which may be too grand a term, went from “I need a thing” to having one in hand over the course of a few minutes yesterday. Neither required a great deal of thought, having previously worked out the proper speed / power settings to cut 3 mm MDF and 1 mm cork.
Other folks may lead you to believe lasers are all about fancy artwork and elaborate finished products. Being the type of guy who mostly fixes things, I’d say lasers are all about making small and generally simple parts, when and where they’re needed, to solve a problem nobody else has.
Perhaps I should devote more attention to using fancy wood with a hand-rubbed wax finish, but MDF fills my simple needs.
With a laser and a 3D printer, shop tools have definitely improved since the Bad Old Days!
The rectangle is 30×10 mm, with lines spaced 0.25 mm apart to simplify estimating distances (although I also have a measuring magnifier) and run at 100 mm/s to simplify converting distance to time. The lines alternate in direction, beginning with a left-to-right line at the bottom (which is bar-straight from the initial positioning move). The wobbles occur at the start of each line.
A closer look with blown contrast:
Engraving – 100mm-s 0.25mm interval 9pct – detail
The maximum error in the Y axis direction looks like 0.12 mm and damps out after 3 cycles. Each cycle covers 2.8 mm = 28 ms = 35 Hz.
The LightBurn Preview shows a 1.5 mm overscan distance and extrapolating the wobbulations leftward suggests the gantry starts the scan line with an overshoot due to the Y axis motion. The cycle-to-cycle damping is about 50%, so the initial overshoot (invisible in the overscan region) might be 0.25 mm, agreeing reasonably well with the 0.2 mm seen while cutting small squares.
The results above come from these settings:
Layer speed: 100 mm/s
Line interval: 0.25 mm
Y acceleration: 2000 mm/s²
Y start speed: 20 mm/s
I then made single-variable changes to the Engraving Parameters settings:
Line shift speed
500 mm/s
10 mm/s
Y Acceleration
200 mm/s²
Y start speed
30 mm/s
Today I Learned: The Y Start Speed (in mm/s) for engraving is capped by the Y Axis Jumpoff Speed (in mm/s², so perhaps the maximum change in speed), which is, in turn, capped at 80 mm/s.
Each of the variations produced a result visually indistinguishable from the image you see above: the error magnitude and oscillation frequency were identical.
One possible reason: None of those settings have any effect, because LightBurn doesn’t do whatever the Ruida controller defines as Engraving. However, changing both the Y start speed and the Jumpoff speedshould have made at least a little change to the results and did not.
Another possible reason: Each 0.25 mm Y axis change requires 20.8 motor steps (either 20 or 21 at 12 µm/step), so the fancy tweaks lack space to take effect, the motor thumps 20-ish steps, and the gantry shakes the same way every time.
The Smell of Molten Projects in the Morning 
