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.

Category: Machine Shop

Mechanical widgetry

Gelatin Capsule Filler Plate
Being a guy of a certain age with a diagnosis of Low Bone Density, I must increase my calcium intake. Rather than add a few hundred calories a day of calcium-rich food that my waistline does not need, I’ll see what adding 600 mg of calcium citrate can do.

Being a guy of a certain type, I prefer to fill my own capsules, which of course involves Quality Shop Time:

Gelatin 000 Capsule Fill Plate – cutting

Quite some years ago, for reasons not relevant here, I acquired several of what were called “manual capsule filling machines” from the usual online sources. During the ensuing years, such devices have fallen under the purview of the DEA and vanished from the import market, leaving (AFAICT) one USA-ian supplier.

The key difference between “machines” for different capsule sizes is the plate holding the capsule bodies:

Gelatin 000 Capsule Fill Plate – installed

A complete machine includes three other capsule-size-related parts:
- A plate holding the caps
- A plate with conical holes used to shake caps & bodies into their respective plates
- A guide plate helping mate caps with bodies
In normal use, you put the “shake plate” on the body or cap plate, dump a pile into it, and shake until most of the caps / bodies fall into the holes. Then you manually insert the rest, invert any that fell in backwards, and generally mess around until they’re all properly oriented in their sockets. After filling the capsules, you put the cap + guide plates atop the bodies, press down firmly, and (ideally) produce 100 filled and sealed capsules.

It turns out Size 000 capsules are sufficiently chonky that I have no trouble capping the bodies by hand without those other parts, so making just the body plate seemed Good Enough™. The story might be different for Size 1 capsules.

The external dimensions and screw holes match the original plate, so this one fits the same base:

Gelatin 000 capsule plate – LB layout

Make one plate and four spacing clips from 6 (-ish) mm acrylic.

If you can think of anything to do with 100 3/8 inch cylinders of 1/4 inch acrylic, clue me in.

Size 000 bodies are close enough to 3/8 inch that I cleaned up the holes with a step drill for a nicer fit. Perhaps making the plate from 3 mm acrylic would produce better results.

Four springs around the screws in the corners support the plate to allow pressing the caps in place. I adjusted the screws to put the top of the plate at exactly the height of the bodies above the blue base place, producing a smooth surface for scraping suspicious white powder into the bodies:

Gelatin 000 Capsule Fill Plate – filled

Iterate filling and tamping until the capsule contents are firm-but-not-overstuffed, then press the plate downward and secure it with the spacer clips:

Gelatin 000 Capsule Fill Plate – capped

The clips hold the plate at the proper distance to let the caps slip over the bodies and lock in place. This is tedious, but much faster than doing the entire process on individual capsules one-by-one.

With the caps locked in place, flip the whole thing above a bowl, remove the clips, press the plate against the base, and 100 finished capsules shower into the bowl.

You could build a complete filler without having the blue base plate & springs, but I’ll leave that project to your imagination.

The LightBurn layout as a GitHub Gist:

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No, I am not making one for you. :grin:
2023-09-20
Solar-Flattening Fiskars Cutting Mats

Fiskars cutting mats must lie flat on the table to be of any use, but they’re remarkably sensitive to warping due to localized temperature variations; a hot cup of tea can wreak a remarkable amount of damage. Suggestions from the InterWebs generally involve a clothes iron, temperature tweaks, overnight cooling, and unpredictable results.

Given that the mats are large polypropylene sheets, I figured applying moderate heat to the entire mat while it’s compressed between two flat plates would work better:

Fiskars cutting mat – solar flattening

That’s one of Mary’s 36×24 mats atop an MDF sheet (with pictures of wood laminated to both sides), under a 7/32 inch = 5.6 mm sheet of non-tempered glass, with a maple shelf supporting the last two inches of the unwarped edge, all sitting on the driveway in full sun.

The first attempt started too late in the afternoon for good heating and, after a few hours, had only slightly reduced the warp. Laying it out the next morning got the mat up to about 110 °F = 43 °C around noon and the warp was completely gone by evening.

I don’t trust the IR thermometer’s temperature measurements on glass, but the surrounding MDF and driveway were plenty hot.

The next sunny day flattened the warp out of 24×18 inch mat on my desk, so success wasn’t a fluke.

We noticed that the larger mat is now uniformly smaller by about 3/16 inch along the 36 inch width and 1/4 inch over the 24 inch height. It was a tag sale find with unknown provenance and, due to the warp, Mary had been using her other large mat for layout, so we don’t know if this one arrived a little short or if my technique both flattened and shrank it.

The smaller mat seems unaffected by its similar treatment, so your mileage may vary.

In any event, a flat mat is much more useful than a warped mat, so we’ll call the operation a success.

2023-09-19
Coaster Cork Alignment Fixture

Having stuck many cork bottoms to many coasters and aligning nearly all of them pretty close, I finally made a fixture to get it right from now on:

Coaster cork fixture – test fit

A plywood disk anchors four arcs cut from a remnant of acrylic mirror left over from the card-suit coasters, using strips of adhesive sheet cut 1 mm smaller than the arcs:

Coaster cork fixture – adhesive sheets

Stick an arc in place, lay the cork inside the arc, and stick the rest of the arcs around the cork:

Coaster cork fixture – cork fit

Squish the arcs in place overnight with Too Many Clamps™:

Coaster cork fixture – clamping

In use, peel the paper off the cork, lay it in place, ease the coaster atop it, press firmly, remove the perfectly aligned coaster, then put a stack of them in the overnight clamp to solidify the PSA bond.

Should’a done this long ago …

2023-09-18
Back-painted Mirror Coasters
Having established that scribbling Sharpies on laser-cut acrylic is a Bad Idea™ due to stress cracking, I made some acrylic mirror coasters with rattlecan spraypaint on the back:

Back-painted mirror coasters

The colors, which look much more obvious in person, are gray, black, and blue. There should be a diamond to round out the playing card theme, but only three fit neatly on the remaining slab of mirror.

A slide show giving a closer look:
Back-painted mirror coaster – gray detail
Back-painted mirror coaster – black detail
Back-painted mirror coaster – blue detail
In person, all of the gritty edges and imperfections vanish, because they’re all well below eyeballometric resolution: you can see them, but only if you look hard.

Those are at 500 mm/s and 15% PWM, which is too fast for fine details due to the HV power supply’s bandwidth limitations. However, the tube doesn’t fire reliably below about 10% and tends to sprinkle speckles over the surface, so there’s not much leeway to slow down.

All in all, the outcome is Good Enough™.
2023-09-15
Craptastic Kitchen Scale: Shattered

So it turns out the surface of the craptastic kitchen scale really was tempered glass:

Kitchen scale – shattered glass

That’s after an inadvertent drop edgewise onto the concrete patio.

Stipulated: given what I’ve already done to / for the thing, the usual warranties do not apply.

The frame around the NP-BX1 lithium batteries held the glass fragments together surprisingly well:

Kitchen scale – shattered glass – detail

Of course, harvesting the good stuff resulted in a pile of fragments, but the carcass cleaned up nicely and, after grafting a temporary top made from scrap acrylic it still worked:

Kitchen scale – temporary surface

I expected to just cut a slab of 6 mm acrylic to match the original 5 mm glass, but for reasons probably related to dielectric constants, the touch controls do not work through that much acrylic. In fact, they don’t work through anything other than the 1.5 mm acrylic shown above, which seems a bit too flimsy for normal use.

The original glass had a design screened on the back surface and covered with paint, which I can certainly mimic, but right now I’m unsure how much effort to put into the thing.

2023-09-14
Tour Easy: DPC-18 Display Controls

The Bafang 500C display I installed on Mary’s Tour Easy recumbent has assist level buttons along its left edge:

Bafang display – clamp bushing

This required her to take her left hand off the handlebar to fiddle with the assist level and, as it turned out, used her thumb in position causing some distress. Given that changing the assist level happens a lot as we ride, it was time for a change.

So I replaced the 500C with a DPC-18 display like the one on my bike, with the key advantage of putting the buttons on the handgrip:

Tour Easy Bafang Controls – DPC-18 buttons

She preferred a higher position for the buttons than I do, with the PTT button for the Baofeng amateur radio below the housing.

After a few iterations, the throttle moved from the right handgrip to the right end of the handlebar crosspiece on a lengthened version of the mount I conjured for Tee’s Terry Symmetry upright bike:

Tour Easy Bafang DPC-18 – throttle mount

That location requires a bit of dexterity, but let us move the twist-grip shifter upward on the handgrip where it is more comfortable. She rarely uses the throttle, so we’ll try this for a while.

The DPC-18 has an awkward portrait-mode display with an incredible amount of wasted space, with the side detriment of displacing the blue Camelbak hose. After a few iterations, we settled on a receptacle to catch the mouthpiece without requiring any fancy snaps / clips / fasteners:

Tour Easy Bafang Controls – Camelbak nozzle catcher

The solid model descends from the Zzipper fairing mounts on that same aluminum bar, with the bottle simply jammed into the big hole:

Zzipper Fairing – Camelbak nozzle catcher – show layout

There being no real forces on the holder, I omitted the aluminum load-spreading plate across the top and just epoxied four threaded brass inserts into the bottom part.

Early reports suggest a happier thumb and no problems stashing the hose, so it’s all good.

2023-09-13
Laser Cutter: Print-and-Cut Alignment Accuracy

Up to this point I’ve been making mirror alignment targets entirely on the laser cutter to ensure accurate alignment:

OMTech 60W laser – beam alignment – focus detail – 2022-03-22

While that works fine, using Dot Mode takes basically forever to chew its way through any nontrivial number of targets.

Now that I have more familiarity with LightBurn’s Print-and-Cut feature, I tried printing the graticules, aligning the sheet, then laser-cutting just the perimeters:

Laser Beam Alignment Targets – cut tabs – smoothed

The smaller targets fit neatly into the hole perpendicular to the beam:

OMTech CO2 Mirror 2 mount – Y Z screws

The larger ones sit flush on the mirrors at 45° to the beam, so stretching the horizontal scale by 1.414 = √2 makes each tick mark correspond to 1 mm of perpendicular beam offset.

All of which worked surprisingly well, with some caveats.

The first gotcha: ordinary consumer-grade inkjet printers do not have CNC accuracy. The corner targets are on 150 mm horizontal centers and 240 mm vertical centers in the LightBurn layout, but my Epson ET-3830 printer put them on 150×241.3 mm centers. This isn’t unexpected, particularly for laser printers, but it means you must use LightBurn’s scaled version of the P-n-Cut alignment.

I used the upper-right and lower-left targets for the P-n-Cut alignment step, confirming the positioning with a laser pulse putting a tiny hole in the paper:

Print-and-Cut – target accuracy

The lines are 0.5 mm wide and the inner circle is 2 mm in diameter, so my alignment at the upper right is as good as it’s gonna get and the lower left is off by maybe 0.3 mm. While it may be possible to be more accurate, I think half a millimeter is a reasonable error budget for targeting accuracy.

The laser-perforated circles should overlay the inner printed circles after LightBurn applies the P-n-C corrections. That they obviously do not indicates the effect of the small target errors. In any event, the maximum error seems to be 1 mm, which gives you an idea of just how precise P-n-C might be.

The perimeter laser cuts are off by about the same amount & direction as the dotted circle in the adjacent target:

Print-and-Cut – perimeter matching

Overall, errors around 1 mm seem possible with careful attention to detail, but expecting anything better than a few millimeters is probably unreasonable, particularly for layouts larger than a Letter size page.

Works for me, though!

The LightBurn SVG layout as a GitHub Gist:

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2023-09-12