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: Laser Cutter

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
Laser Cut Plywood: Flame vs. Assist Air Flow

While cutting some oak plywood, I managed to get some interesting (to me, anyhow) pictures of how the assist air interacts with the laser kerf:

Laser cut plywood flames – C

The air flow is about 12 l/min from the pump in the bottom of the laser cabinet and is pushing most of the fumes through the kerf, where they ignite and burn merrily.

The plywood is up on magnetic punk spikes to give the fumes plenty of room to disperse without making too much of a mess on the bottom surface. Unfortunately, the flame can blowtorch the cut parts after they fall through onto the honeycomb.

Another view shows some smoke doesn’t make it through the kerf:

Laser cut plywood flames – B

The bulk of the flame seems to trail behind the beam as it cuts through the wood, which isn’t surprising:

Laser cut plywood flames – A

Just like acrylic flame, it’s kinda pretty, but should serve as another reminder why you must never, ever run your laser unattended.

2023-09-29
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
Laser Cutter: Backlash Test

A backlash test found on the LightBurn forum puts the machine through a series of difficult maneuvers:

Backlash test

That’s burned on the back of a paperboard box at 400 mm/s @ 15%/10% power, which is slightly too intense for the smaller patterns.

The key point is that the machine has no detectable trace of backlash, with all the opposing lines matching up and equal spacing regardless of the approach direction.

Whew!

The acceleration may be a little too high, as seen on some recent beam alignment targets:

Print-and-Cut – perimeter matching

The larger targets on the right let the machine reach a speed closer to the nominal 400 mm/s around the arc, so the cut along the tape tab after the right-angle turn comes out a bit wobbly; the smaller targets are fine. The red lines are just under 0.5 mm wide and the wobble is on the same order, so it’s pretty close to being OK.

2023-09-25
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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view raw Gelatin 000 capsule plate – LB layout.svg hosted with ❤ by GitHub

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
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