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
Seen with the shock cord in place, it’s obvious that combining moderately high temperature with steady compression sufficed to bend the PETG enough to pop those tabs loose from the vent.
So the OpenSCAD model now produces a stiffening ring to be laser-cut from acrylic:
The whole snout builds as a single unit in the obvious orientation:
Clothes Dryer Vent Filter Snout – V2 – slicer
Because the part of the snout with the tabs is 7 mm tall, I glued a 4 mm acrylic ring to a 3 mm ring, with both of them glued to the snout:
Clothes Dryer Vent Filter Snout – acrylic gluing
That’s “natural” PETG, which I expected to be somewhat more transparent, but it’s definitely not a dealbreaker.
Mary will sew up another cheesecloth filter and we’ll see what happens to this setup.
As the saying goes, “Experience is what you get when you don’t get what you want.”
Fortunately, living in the future makes it easy to iterate on the design & implementation until experience produces what should have been obvious at the start.
The OMTech 60 W laser has a 24 V + 5 V power supply for the stepper motors and, I had always assumed, the feeble LED strip light on the gantry:
OMTech 60W laser – OEM lighting
The stepper motor driver settings, plus a few amps for the controller and suchlike, added up to something over 12 A, far more than the 24 V supply’s 6 A spec should produce. When I added the COB strip lights around the platform, I dropped a 24 V wall wart into the electronics bay to avoid abusing that poor supply:
OMTech 60W laser – COB LED strips
For reasons to be described later, it’s now time to upgrade that 24 V power supply to a 15 A supply that’s been on the shelf for far too long. However, it does not have a 5 V output, so it’s also time to figure out how much 5 V power the laser really needs.
A quick measurement suggested the 5 V output delivered 20 mA to something. After convincing myself the multimeter was working and that the gantry LED strip was still lit, I finally tracked the wire pair to the red-dot pointer:
OMTech red dot pointer – polarizing filter installed
Yeah, a whole dual-output power supply for one red-dot laser module.
Conveniently, the KT332N controller has several 5 V outputs and the LIMIT terminal block even has a GND terminal on the other end:
KT332N Limit Terminals – OEM
Prying off the hot melt glue, extracting the red-dot pointer wiring from the raceway, crimping ferrules on a couple of jumpers, and deploying a pair of Wago connectors:
KT332N Limit Terminals – red dot wiring
I am still not accustomed to the color code:
Black = signal
Brown = power
Blue = GND
But it’s like that and that’s the way it is.
The red dot lit right up, the gantry LED strip obviously uses 24 V power, and I must shoehorn a slightly larger 24 V supply into the space currently occupied by the old supply.
The labels now snuggle closer to the shaft and (barely) fit on smaller gears:
Mini-lathe stacked change gears – 28T – solid model
The stacked B-C gears for the jack shaft work as before, with both labels on the top gear:
Mini-lathe stacked change gears – 28-50T – solid model
The admittedly flimsy motivation for all this was to make a 28 tooth gear to cut a 0.9 mm pitch, thus filling an obvious hole in the gear table.
My collection of gears could do 21-60-81-50, but the 81 T gear collides with the screw holding the 21 T gear. Rearranging it to 21-50-81-60 showed the B-C gears exceeded the space available.
Because it’s all ratios and a 28 T gear is 4/3 bigger than 21 T, reducing the rest of the train by 3/4 should work. In fact, it produced a reasonable 28-80-81-50 chain:
Mini-lathe change gears – 28T installed
The fact that I do not anticipate ever needing to cut a 0.9 mm pitch has nothing whatsoever to do with it; that gear will surely come in handy for something.
While I was at it, I made a 27 T gear, because 27 = 21 × 9/7:
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I intended to single-point a few turns on an 8 mm axle to ease running an M8-1.25 die over it, thus making a thread for a nut securing a wheel (about which, more later). This required selecting the change gears for a 1.25 mm thread pitch, the installation of which proved sufficiently awkward to give me the opportunity to discover a washer spacing the banjo just a little farther outward would improve the gear alignment:
Mini-lathe change gear banjo – shim detail
The overview shows how moving the whole banjo just a bit leftward better aligned black Gear B with respect to orange Gear A:
Mini-lathe change gear banjo – shim overview
From A to D, a 1.25 mm pitch uses 42 40 45 60 tooth gears. The 42 tooth gear supplies the magic required to convince a hard-inch 16 TPI leadscrew to produce good-enough metric pitches.
In addition to the usual hassle, the main reason the process took so long is doing having to do it twice. After I swapped Gear C and Gear B on the jockey shaft in the middle, the leadscrew produced the correct 1.25 mm motion for one turn of the chuck:
It’s ordinary laser-grade 3 mm plywood with another wood inlay, sanded flat and covered with polyurethane sealer.
The key attraction: not fiddling with tiny veneer bits.
Cut the recesses in one pass with enough energy to make them at least as deep as the veneer thickness:
Marquetry test – plywood cutting
Press the veneer onto aluminum tape, taking care to avoid wrinkles and folds, and cut away everything that doesn’t go into those recesses:
Marquetry test – veneer cutting
Which looks gnarly when you’re done:
Marquetry test – veneer on tape
I cut the aluminum tape to fit within the corner targets around the plywood layout, thus simplifyingmaking possible aligning the positive veneer shapes with the negative plywood shapes while being unable to see either of them.
Slather wood glue over the plywood, make sure even the tiniest recesses are filled, align the aluminum, clamp the two firmly together, wait for a few days while the glue cures in that airless space, then peel off the aluminum:
Marquetry test – peeled
Which looked so awful I thought that was a disaster, not least because the veneer stood proud of the plywood, so it remained on the back of the bench for far too long.
Eventually, having deployed the sander for another project, I sanded the veneer flush with the plywood to reveal the nearly perfect results in the lead picture. There’s a bit of smoke stain left in the grain, but the tiniest recesses have at least some veneer fill and the surface is entirely smooth.
The overlaid circles worked out:
Marquetry test – detail 1
The darkest block and the smaller lines are badly smoke-stained veneer, as they have wood grain visible under magnification. I think those may not have fully entered their recesses and we’re seeing a very thin veneer layer soaked with soot-filled wood glue.
Another view:
Marquetry test – detail 2
The checkerboard squares worked well;
Marquetry test – squares 1
To my astonishment, even the 0.5 mm squares have some veneer inside, as do the 0.5×1.0 mm rectangles on the left:
Marquetry test – squares 2
Not knowing any better, there’s no kerf offset on any of the figures and they’re separated by about the 0.2 mm width of the focused spot.
Aligning the veneer to the recesses was tricky and I was not at all sure it had happened. I think larger shapes would be much easier and might give off a confirming squish as they meet their sockets.
Gotta try that again without the benefit of beginner’s luck.
Those of long memory will recall our vermiculture setup in the basement that turns kitchen scraps into plant food. We accumulate scraps in plastic milk jugs, which jugs get recycled after they become grody.
I finally made a decorative coaster to keep the sometimes-wet jug off the counter:
Printed Fragment Coaster 165mm – in use
This used several of the larger smashed glass fragments from the collection:
Fragments 165mm square – scan sample
They all fit inside a 165 mm square, with the conformal perimeter disguising the outline:
Run a bead of epoxy around the edge of each recess
Fill in the center with a thin layer
Squish the metallized paper reflector in place starting from one end to ease the bubbles out
Cover the reflector with another layer of epoxy
Lay the glass fragment down starting at one end
Press gently down to get all the bubbles out
Cover the glass with more epoxy
I dripped enough epoxy on each fragment to form a meniscus without having it go over the rim:
Printed Fragment Coaster 165mm – epoxy meniscus
The Basement Shop temperature is just over 60 °F, so I put a heating pad in a huge ziplock bag, laid an aluminum sheet atop it as a heat spreader, put some waxed paper on the aluminum just in case, then did the filling described above:
Printed Fragment Coaster 165mm – warming setup
A cardboard box on top helped the heating pad keep the coaster at a uniform 85 °F, slightly warmer than the epoxy instructions recommend, but it cured overnight with a wonderfully shiny surface.
The white PETG filament started out at 39 %RH and 50 g of silica gel dragged it down to 23 %RH after a three days: still unusually high.
The beads weighed 54.6 g, a weight gain of 9 %, which is about as much as they’ll take. I replaced them with 50 g of new-from-the-bottle beads and the meter dropped to 14 %RH overnight.
Running the tiny fan for another day made no difference:
Polydryer Box desiccant tray – fan
Thereby confirming my suspicion that air circulation inside the box isn’t nearly as much of a problem as I expected.
So filament need not arrive bone-dry and, with enough surface area exposed to the air, silica gel beads can adsorb their limit of water vapor in a day or two.
The Smell of Molten Projects in the Morning 