Ed Nisley's Blog: Shop notes, electronics, firmware, machinery, 3D printing, laser cuttery, and curiosities. Contents: 100% human thinking, 0% AI slop.
Tag: Improvements
Making the world a better place, one piece at a time
Having recently built a herd of Tiny T-Rexes from cardboard, I finally discovered they didn’t stand quite right because their feet don’t reach the ground.
The smaller orange outline is the original foot:
Tiny T-Rex – 100mm – foot comparison
The larger red outline came from a bit of node editing:
Tiny T-Rex – 100mm – reshaped foot
I tweaked the original body to include the realigned foot shape to ensure the feet don’t get pried apart, as we’re not bound by anatomical accuracy.
None of which matters for cardboard bonded with copious amounts of hot-melt glue, but I had smaller plans:
Acrylic Tiny Rexes
The center piece is 6 mm translucent gray acrylic from the longsuffering IBM Printer Stand, with armor from 3 mm yellow on the left and a mix of 3 mm green / 1.5 mm transparent green on the right, held together with 3M 300LSE adhesive sheet.
Scaling the spider layout to match the 6.8 mm dual-layer cardboard originally holding a monitor turned out well:
Cardboard Spider – garage right
The LightBurn nesting routine needed three equal-sized sheets for all the pieces, but I wanted a spider for each of the two garage door lights:
Cardboard Spider – garage left
So I grouped pairs of the abdomen shapes in the obvious (to me) arrangement, selected all but the body and legs, and LightBurn nested them on a single sheet:
Spider – Nested sheet 1
It easily nested the body and legs on a second sheet:
Spider – Nested sheet 2
However, I needed that second sheet for the second spider:
Cardboard Spider – sheet 1 cutting
So I manually arranged one big leg and one small leg to fit each end of the four narrow box flaps to get sixteen legs:
Cardboard Spider – leg cutting
The two bodies (the weird shape on Sheet 2) barely fit on two of the four small box-closing flaps, two spiders emerged from the pieces adorned with dollops of hot-melt glue, and the cardboard stockpile got the two remaining small flaps that will surely come in handy for something.
The eyes are fluorescent green acrylic sized for a press fit.
A revised sketch of the key dimensions shows a clearance hole for the 3 mm screw (to eliminate tapping the heatsink) and a reminder about how to locate the wire holes:
Bore a 19 mm ID recess 10 mm deep in the (1 inch OD × ¾ inch ID) aluminum tube and score the ID for improved epoxy griptivity:
Tour Easy Running Light – heatsink scoring
Knurl the ¾ inch rod to bring the OD to a slip fit in the shell:
Tour Easy Running Light – heatsink plug knurling
Take them ouside, hose down with brake cleaner to get rid of the cutting fluid, butter ’em up with epoxy, align in the lathe, and let ’em cure overnight:
Tour Easy Running Light – heatsink epoxy fixture
This time I managed to not cut off the rod, which dramatically simplifies boring the shell and facing the front end of the rod flush with the inside of the shell so the LED PCB sits flat in there:
Tour Easy Running Light – heatsink front ID
Clean up the shell OD and turn the back to 23 mm OD to fit the PVC tube from the failed taillight:
Tour Easy Running Light – heatsink shell OD
Crisp up the edge for a tidy fit:
Tour Easy Running Light – heatsink shell corner
Break / file all the corners, then bandsaw the rod and face the back end:
Tour Easy Running Light – heatsink rear facing
Set it up on the Sherline mill, find the center, and use manual jogging to poke the holes at the proper coordinates:
Tour Easy Running Light – heatsink Sherline setup
Take the finished heatsink outside again for more brake cleaner action.
The 3D printed circuit plate now sports two inserts:
Running Light Circuit Plate – two inserts – solid model
Epoxy the inserts in place, prepare two 1.6 mm = 1/16 inch steel wires, and chop the head off an M3 screw:
Tour Easy Running Light – heatsink with circuit plate
Stipulated: my center-finding hand is weak.
Aligning the LED heatsink with those wire holes is a pain:
Solder the LED in place atop some heatsink compound
Push the lens holder (without the lens!) over the LED
Insert holder + LED into the heatsink
Rotate to put one LED terminal between the wire holes in the heatsink
Rotate to align the recesses in the PCB with the wire holes in the heatsink
Match-mark the holes on the lens holder with a transfer punch
Grab the holder in the Sherline vise
Align & drill wire holes in the holder
Solder wires to the LED PCB, aimed inward atop the LED leads
With the LED & lens holder prepared & set aside, butter the circuit plate parts with JB PlasticBonder, align the plate perpendicular to the heatsink using V-blocks / 123 blocks / whatever, and let it cure overnight.
The lens allows plenty of room to run the wires from the PCB around the LED inside the holder to the holes:
Tour Easy Running Light – 1W LED lens fit
So do that:
Dab PlasticBonder on the bottom of the lens holder
Stick the LED to the holder (still with no lens!)
Thread the LED wires through the holes in the holder, the LED PCB, and into the heatsink
Dab PlasticBonder on the bottom of the PCB
Ease the holder + LED into the heatsink while pulling the wires through the holes
Finally install the lens in the holder
Clamp the whole mess lenthwise with padding atop the lens to prevent scratches
I transferred the circuitry from the failed taillight to the new one, atop refreshed double-sided foam tape:
Tour Easy Running Light – Arduino side
With hot-melt glue securing the 2 Ω current-sense resistor to the circuit plate:
Tour Easy Running Light – regulator side
Slide the PVC case over the circuit plate, secure the end cap with a 25 mm screw, and reinstall on the bike:
While building up another taillight for Mary’s Tour Easy (about which, more later) and based on previous experience, I wondered if the 1 W red LED’s thermal pad was soldered to the circuit board as it should be.
Lo and behold, the solder paste was reflowed, likely while tinning the six solder pads:
Tour Easy Running Light – 1W LED PCB solder
But not with the LED in place:
Tour Easy Running Light – 1W LED base glue
What looks like melted solder is really an adhesive layer, much like the craft adhesive sheet I use to stick things together. Presumably, they just glue the LEDs to the PCB / heatsink, solder its two leads by hand, and call it done.
Checking an LED marked “Dead” on the backside of its heatsink shows the amount of solder paste varies, but the LED wasn’t there when it melted:
1W LED – base glue and PCB solder
This not being the first time, I cleaned the adhesive off the center pad and the LED, removed the solder, applied a dab of heatsink grease, and soldered the LED in place.
Which looked like this on the previous taillight:
1W LED – thermal grease
Might be a bit too much grease, but it’s certainly a better heat conductor than adhesive.
Perhaps surprisingly, the whole process is odorless. This is in the basement where ugly doesn’t count for much.
The leakage comes through the air vent holes at the top of each leg socket:
Worm Bin Vent Cover – vent
Unsurprisingly, the “worm tea” (it ain’t water!) dripping from the bottom of the compost tray goes directly through the vent holes and down the leg. It’s not clear to me what they expected.
A simple 3D printed black TPU cap atop the leg socket should prevent most of the leakage:
Worm Bin Vent Cover – installed
The odd pattern comes from Concentric infill around the notch, even though Concentric infill seems better suited to round things and fat extrusion threads with a 0.8 mm nozzle than straight lines. The weird stuff on the vertical side is a reflection of the basement and phone flash from the smooth TPU layer edges.
The tray with the worms and compost sits atop the strut between the socket and the body, with the cap allowing room for the screen keeping the worms out of the sump.
Ribs on the underside of the cap hold it above the leg socket to let the air through:
Worm Bin Vent Covers – solid model
Although five caps fit the MK4’s platform, I printed one or two at a time while tweaking improving the design:
Worm Bin Vent Covers – PrusaSlicer preview
This design is for the original Can-O-Worms shown in the second picture and may not quite fit the new version. We’ll know more when we empty the bottom tray.
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The living room windows suffer from all the thermal problems you might expect in a late-1960s house, despite the slightly more recent storm panes, so I’ve been adding insulating film during the cold season. This works surprisingly well, although the tape holding the film tends to lose its grip in the angle between the (real, not pretend!) mullions and the window sill.
This year I added triangular fillers to ease the corner:
LR Window Film – mullion filler
They’re Desk Signs from boxes.py, with the bottoms angled by 2.5° to compensate for the slightly misaligned sill and a small cutout clearing the paint accumulation in the corner:
LR Window mullion filler – LightBurn layout
A strip of tape down each side of the mullion and across the filler anchors the film, producing a slightly baggy fit. Next year I’ll use only one strip down the middle.
