Ed Nisley's Blog: Shop notes, electronics, firmware, machinery, 3D printing, laser cuttery, and curiosities. Contents: 100% human thinking, 0% AI slop.
The auto-rewind spindles for PolyDryer boxes fit a variety of spools, but recessed hubs like this require a pair of washers to center the spindles:
Filament spool washers – recessed hub
They’re laser-cut, although you could print them easily enough:
Filament spool washers – recessed hub – installed
The size for that particular spool:
OD = 80 mm
Flange side ID = 51 mm
Nut side ID = 43
Thickness = ¼ inch, near enough
Other spools required a 3 mm shim on the flange side to sit centered in the PolyDryer boxes. Those are basically identical what you see above, with a 72 mm OD matching the flange.
The PETG-CF filament arrived on cardboard spools, which are apparently the new hotness:
Filament spool washers – printed
The 56 mm spool ID requires adapters on both sides, with the flange side getting a 4 mm shim:
Filament spool washers – printed shim – flange side
That skootches the spool over against the 1 mm shim on the nut side:
Filament spool washers – printed – nut side
It would be possible to modify the auto-rewind spindle diameters to suit, if you were a dab hand with Fusion360, but the variety of hubs around here tells me a set of cheap adapters & shims makes more sense.
You should not assume anything will fit the spools you have, no matter how much they resemble what you see above.
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Their rubbery port covers work best with 6 mm OD PTFE tubes, but let the MMU3’s 4 mm tubes slide into / out of the boxes under normal filament extrusion / retraction forces, so I conjured an adapter for PC4-M10 pneumatic fittings:
PolyDryer PC4 Fitting – installed
A pair of M3 screws hold the adapter plate in place, with an EVA foam gasket sealing against the cover:
PolyDryer PC4 Fitting – interior view
The PC4-M10 fittings let the 4 mm tubing slide right through, so the adapter has a 0.5 mm bottom sheet to block the tube, with a small hole for the filament:
PC4 Fitting Plates – bottom – solid model
You could use PC4-M6 fittings to block the tubing, but the 2 mm lumen on the fittings I have barely pass 1.75 mm nominal filament. Comments found elsewhere suggest identical PC4-M6 fittings have smaller lumens that snag the filament as it moves in one direction or the other.
The two blind holes get heat-staked 4×4mm M3 brass inserts.
The top has a threaded hole for the fitting:
PC4 Fitting Plates – top – solid model
Despite what the description says, the thread is not an M10 metric straight thread: it is a tapered pipe thread used for gas- and liquid-tight fittings. Considerable measurement & searching suggested a ⅛BSP-28 thread, because:
British Standard Pipe threads are used everywhere in the world except the USA
Both my metric tap sets have a ⅛BSP-28 tap along with all their hard-metric straight taps
The thread is painfully close to ⅛NPT-27, which would probably work in a pinch if it was the only tap you had.
Those PC4-M6 fittings might sport 1/16BSP-28 threads, but you’re on your own.
Further searching suggests nobody uses the corresponding tapered female pipe threads and everybody goes with a straight internal thread, so I conjured a stumpy threaded rod using the BOSL2 library and removed it from the adapter plate:
The 9.7 mm diameter is the ⅛BSP-28 “major diameter”, rather than its “gauge diameter”, simply because it produced a good fit. The beveled top guides the fitting into the hole, but I still managed to cross-thread one.
The OpenSCAD code also produces SVG files to laser-cut the foam gasket and a drill template:
PolyDryer PC4 Fitting – drill template
The holes were step-drilled to ⅛ inch (which has a historic relation to the ⅛BSP-28 size, because iron pipe) for a generous fit around the M3 screws.
That was way more complicated than I expected and I’m really glad to live in the future where this is a 3D printer project, not a metalworking project involving an actual tap in, say, steel.
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The switch on the Anker LC-40 flashlight serving as a running light on my Tour Easy became slightly intermittent before I replaced it with a 1 W amber LED, but it was still good enough to become the troubleshooting flashlight in the tray next to the Prusa Mk 4 printer. Eventually, of course, it failed completely and Something Had To Be Done.
Although I knew an exact replacement switch had to be available from the usual sources, I could not come up with a set of keywords capable of pulling them out of the chaff.
Which turned into a multi-dimensional search over cap geometry, TPU extrusion speeds & feeds, and various impossible-to-directly-measure sizes:
Anker LC-40 Flashlight – TPU cap iterations
The squarish block over on the left is PrusaSlicer’s version of a support structure wrapped around the first cap version; if human lives depended on it, I could surely extract the cap, but it would take a while.
The remaining debris samples occured while discovering:
An extruder temperature of 230 °C, not 250 °C, works well
A conical shape of the lip around the open end to eliminate the support structure
TPU doesn’t bridge well, so the closed end must be down
Length of the central pillar to barely touch the switch stem when released
Cap length and wall thickness so the TPU shell can collapse enough to actuate and release the switch stem
Because I expected this would be an easy job, I used snap ring pliers to unscrew and rescrew the threaded retaining ring holding the switch PCB in place. Because the pliers didn’t have a stable grip on the ring, the threads eventually became just a bit goobered.
This was not a problem, because I have a(nother) 3D printer:
Anker LC-40 Flashlight Retainer – show view
The gray thing on the right is a simple pin wrench fitting both the original and the replacement retaining rings, so I can orient the rings properly while unscrewing & rescrewing:
Anker LC-40 Flashlight – pin wrench in place
The threads have a 0.75 mm pitch and, while it’s possible to print screw threads, even a tedious 0.1 mm layer height would define each turn of the thread with only 7-½ layers.
This was not a problem, because I have a mini-lathe:
Anker LC-40 Flashlight – thread cutting
The yellow & green things on the left of those solid models are the fixture holding a retaining ring for threading and the washer applying pressure to keep the ring in place:
Anker LC-40 Flashlight – lathe fixture – detail
The alert reader will note that washer lacks holes for the alignment pins I added after seeing the washer sit not quite concentric on the fixture. I could call it continuous product improvement, although I doubt I’ll print another one.
Setting up the lathe involved finding the proper set of change gears, including the vital 42-50 stacked gear I made a while ago to print metric threads on a hard-inch lathe:
Anker LC-40 Flashlight – lathe change gear train
Although you’re supposed to measure the thread spacing on a skim pass, I find it’s easier to just measure the carriage movement for one spindle rotation:
Anker LC-40 Flashlight – lathe gear check
A few passes produced a fine retaining ring:
Anker LC-40 Flashlight – OEM vs lathe-cut threads
Sporting much nicer looking threads than the goobered original:
Anker LC-40 Flashlight – OEM vs lathe-cut threads
The original switch had a stabilizing ring around the body to prevent it from wobbling under the original rubber cap.
This was not a problem, because I have a laser cutter:
Anker LC-40 Flashlight – new switch in stabilizer
Those came from a scrap of fluorescent acrylic.
The wave washer behind the acrylic stabilizer improves the contact between the PCB trace around the rim and the flashlight tailcap, with the current passing through the body to the “light engine” up front. The retaining ring provides enough pressure to compress the wave washer, which is why it’s so easily goobered without a close-fitting pin wrench.
With everything assembled in reverse order, the flashlight worked pretty much as it did back when it was new:
Anker LC-40 Flashlight – TPU cap installed
However, after describing this during a recent SquidWrench meeting, I discovered that adding “latching” to my keywords surfaced a bodacious assortment of flashlight switches, so (a few days later) I removed the not-quite-right switch and replaced it with an identical twin of the OEM switch requiring just a little lead forming to fit the PCB.
Even better, using the 3D printed pin wrench to screw the original retaining ring into the flashlight’s aluminum threads a few times re-formed (unrelated to recent electrolytic capacitor reforming) its goobered threads well enough to fit and work perfectly again.
So I have:
… reassembled the flashlight with more-or-less original components
… a repair tool kit ready when another LC-40 fails
… re-learned the lesson that any time spent making a fixture or a special tool is not deducted from one’s allotment
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Last week a wind gust blew my Tour Easy over while resting on its kickstand at Mary’s garden; I rarely depend on the kickstand for that very reason, but some days are like that. Anyhow, the mount for the Sony AS30V helmet camera did exactly what it should by releasing the camera, rather than grinding it into the ground.
I was still using that helmet, albeit with a better mirror mount, but it was getting rather crusty and the hook-n-loop straps were definitely sun-faded, so I built a better mount with an adapter plate matching a new-old-stock helmet from the stash:
Sony AS30V Helmet mount – side view
The white slab atop the helmet curves to match the helmet contour, with the ridge fitting into the vent slot:
AS30 helmet mount – solid model – show view
OK, the helmet isn’t orange, but you get the idea. The sphere has a 153 mm radius, calculated from the Official Sony helmet mount’s bottom curve, minus a ring shaping the central groove:
AS30 helmet mount – solid model – tab ring
This upside-down view shows the interesting parts:
AS30 helmet mount – solid model
The flat side sticks to the camera’s holder with a custom-cut sheet of craft adhesive shaped like this:
AS30 helmet mount – glue
The overall outline of those things comes from a scan of the bottom of the Sony camera holder, passed through Inkscape and LightBurn to generate the curves:
AS30 Baseplate scan
The large notches in the sides pass hook-n-loop straps intended to break away when the helmet hits the ground again. The front tunnel (of two, because symmetry) passes a cable tie preventing the camera from parting company with the mount during normal riding and holding the yellow latch in the Locked position:
Sony AS30V Helmet mount – rear view
It is just barely possible to slide the cable tie over the front of the camera to release the latch.
The camera rides upside-down to protect the lens from scuffs and scrapes. Fortunately, there’s a setting to invert the picture.
For completeness, the front view:
Sony AS30V Helmet mount – front view
The furry patch covers the microphone pores to kill (most of) the wind noise.
The sharp ventral angle matches the helmet’s midline ridge in the back, but obviously isn’t needed over the vent hole in the front. I decided to not bother making a comprehensive model of the hole, not least because I didn’t really know the camera’s exact front-to-back location.
The OpenSCAD source code and baseplate shape as a GitHub Gist:
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A bird box from long ago emerged from the heap and took its place in an upstairs window:
Bird Box window mount – installed
That big open back held an acrylic sheet letting us watch wrens raise their family; snugging it against the window makes that sheet superfluous. We’re hoping to lure the Wreath Finches from their preferred spot by the front door, but we’re open to any birds in need of a nesting spot.
The aluminum angle formerly securing the box to various wood window frames wasn’t going to work here, so I conjured a pair of rotating T-nuts to fit the track in the plastic window frame:
Bird Box window mount – nuts
They’re made from a 5/16-18 T-nut and two layers of 3 mm plywood, all glommed together with E6000-Plus adhesive because it did not scamper out of the way when I opened the Adhesives Cabinet.
Some doodling convinced me a pair of quarter-circles welded back-to-back, minus cutouts for the metal T-nuts, would suffice:
Bird Box window mount – nuts
The radius must be a little less than the width of the opening into the channel (20 mm) and the diameter must be a little more than the width of the channel behind that opening (32-ish mm), so I picked 17 mm. The metal T-nut flange is just over 20 mm, but the spike cutouts (omitted from the LightBurn layout) let it slip through the opening.
A random block of wood positions the box away from the frame enough to clear the outermost flange carrying the screen. Drilling oversize ⅜ inch holes countersunk the top of the T-nut into the block and eliminated excessive alignment fussiness.
Slicing 20 mm off the bolts fit them into the space available, with a pair of stainless washers covering the gaps.
A doodle with measurements you won’t need, but surely handy for mounting something else around here:
An email discussion suggested the Champion hose nozzle might, once upon a time, have had a washer between the conical and cylindrical sections.
So I made one:
Champion hose nozzle – rubber washer
The details:
OD = ½ inch
ID = 9/32 inch
2.5 mm stamp pad rubber
It sealed perfectly, but, just before shutting off, the washer vibrated in the water flow and gave off an ear-shattering (even to my deflicted hearing) howl.
Perhaps a stiffer and thinner washer with a slightly larger OD would work better.
A quick check of similar nozzles in the Box o’ Hydraulics shows none of them feel like they have a compliant washer in there, but any sufficiently old rubber will have long since fossilized.
This seems like a good job for a 3D printed washer with a conical face, made from slightly squishy TPU plastic to ease it past the nozzle’s internal threads. All I need is the ability to print TPU …
Control Button Caps – solid model – show view assembled
The current version of the labels isn’t much to look at:
HQ Sixteen control caps – new caps
The OpenSCAD code produces an SVG outline of the faceplate, surrounded by four alignment targets:
Control Button Caps – face view
Import the SVG into Inkscape and tart it up:
Control Button Caps – Inkscape
The alert reader will note the labels are swapped left-for-right.
The black characters on the left get printed on heavy white paper and laminated; feel free to add artistic embellishments. You must delete the cyan-ish shapes showing the faceplate and switch openings, which just show where the characters will end up, but you must print the four corner targets for alignment.
The red and orange shapes on the right define the outlines for laser-cutting the laminated paper and adhesive sheet after you import the Inkscape SVG file into LightBurn. The Inkscape colors will automagically put the shapes on separate LightBurn layers, with the cyan-ish shapes going onto non-cutting Tool Layer T2.
Set the cutting speed & feed to match your machine, lay the laminated labels on the platform, use Print and Cut to align two diagonal corner targets with the corresponding printed targets, then Fire. The. Laser.
The orange shapes have half a millimeter inset to leave a slight non-sticky margin around the edges:
HQ Sixteen control caps – adhesive layer
Although those shapes have the same four targets, you align the adhesive by hand and eye. Cut them out, peel one side, stick adhesive to the label, peel the other side, stick adhesive to the faceplate, and you’re done.
The Smell of Molten Projects in the Morning 