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.

Tag: Improvements

Making the world a better place, one piece at a time

Laser Cutter: Beamline Realignment
Although the most recent mirror alignment exercise put the laser beam parallel to the axes and centered in the aperture perpendicular to the beam, a target directly on Mirror 2 showed the beam was badly off-center:

Beam Alignment – 2M detail – 2023-09-16

Because that target is sitting flat on the mirror, the beam appears wider than it is tall. The horizontal graticule divisions are 1.4 mm apart to allow direct measurements: the spot is really circular and 3 mm in diameter.

Poking around inside the cabinet reminded me that all of the mirrors sat with their adjustments jammed at one end of their range, rather than being more-or-less centered.

Mirror 2, in particular, was up against all three limits. The slots behind these two screws allow the mount to slide along the X axis:

OMTech CO2 Mirror 2 mount – X screws

Seen from the front of the cabinet, those same two screws set the mirror position in the Z axis:

OMTech CO2 Mirror 2 mount – Y Z screws

As you may imagine, using those two screws to secure the mirror at a specific location in both X and Z at the same time is … challenging.

The two screws directly under the mirror set its position along the Y axis and allow a slight rotation around Z to fine-tune the alignment of the perpendicular aperture used for mirror alignment; unlike the other two axes, the mirror wasn’t jammed against the end of the slots.

Moving the laser beam horizontally toward the center of Mirror 2 requires one or more of:
- Moving Mirror 2 farther away from the center of the cabinet, but it is already at that end of the X axis slots above
- Moving the laser tube toward the back of the cabinet, which also requires moving Mirror 1, which is almost at the end of its adjustment range.
- Moving Mirror 1 closer to the laser tube, which its adjustment slots do not permit
Mirror 1 sits on a pedestal with a slotted base allowing adjustments along the Y axis:

OMTech 60W laser beam test – mirror 1

The pedestal could move a few millimeters to the rear, but the screw on the far side is even closer to its limit.

Moving the laser beam spot upward on the mirror requires:
- Lowering the mirror, which is obviously impossible given the position of the Z axis slots around the adjusting screws
- Raising the laser tube
Mirror 3, inside the laser head on the gantry, was also sitting at the lowest possible point in its adjustment range:

OMTech CO2 Mirror 3 mount – Z screws

All of which suggested I should resign myself to adjusting the beamline:
- Raise the laser tube by 5 mm
- Move Mirror 1 closer to the laser tube by about 10 mm
Raising the tube gets both Mirror 2 and Mirror 3 off their Z axis adjustment limit, but requires raising Mirror 1.

Moving Mirror 1 gets Mirror 2 off its X axis adjustment limit.

Nothing changes the position of Mirror 2 on its Y axis screws, but that adjustment will help fine-tune the beamline into Mirror 3.

So I cut some 5 mm plywood spacers and nerved myself.
2023-10-03
Cheap Rechargeable Kitchen Scale: FAIL

While pondering what to do with the shattered kitchen scale, I got a bottom-dollar replacement touting its rechargeable lithium battery. After giving it the obligatory charge-before-using, I put it in service. Five days later, its battery was dead flat discharged.

So I gutted it to extract the battery:

Cheap digital scale – lithium cell

It’s a cute little thing, isn’t it?

Much to my surprise, the obligatory battery rundown test showed it matches its 0.74 W·hr label:

Kitchen Scale – Charge1

We all know where this is going, right?

Crunche a connector on the battery, another on the scale, and make up a suitable current tap for a meter:

Cheap digital scale – current measurement setup

Which looked like this:

Cheap digital scale – active current

That’s about what I found for the craptastic scale running from a pair of CR2032 primary cells, so it’s not out of line.

Turn off the scale and measure the idle current:

Cheap digital scale – inactive current

Do you think I got a dud?

For all I know, the little microcontroller under the epoxy blob is running a continuous attack on my WiFi network, with the intent of siphoning off all my sensitive bits. Ya never know.

Dividing the battery’s 200 mA·hr rating by 4 mA says it really should be dead in 50 hours, which is close enough to five days: diagnosis confirmed!

Rather than fight, I switched to a battery with more capacity:

Cheap digital scale – NP-BX1 replacement

It’s long past its prime, but ought to last for a month, which is about as long as the shattered scale survived on a similar battery.

Sheesh & similar remarks.

2023-09-27
Moonlander Elevators

What else would you call things that raise the back of a Moonlander keyboard:

Moonlander elevators – installed

The Moonlander comes with two adjustable struts, one for each keyboard half, which should hold the things at whatever angle you like. I put wood blocks underneath for better support, but finally gave up and laid out a quartet of elevators on scrap 3 mm acrylic:

Moonlander elevators – laser cutting

The upper hole is 30 mm from the base and that’s the only one I needed, so they’re even easier to make than they look.

Done!

2023-09-26
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
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
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