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

Slotted Beetles

Continuing the theme of slot resizing & overall scaling:

Beetle Collection

The original model has 3.0 mm slots and arrived in CorelDraw format requiring a bank shot off InkScape to create an SVG file suitable for LightBurn. After the usual cleanup & optimization, I applied global rescaling to match the available material.

The smallest beetles use 1.9 mm chipboard:

Beetle – 1.9mm chipboard

Everything is held together by ordinary wood glue, squeezed together for a few moments until the two parts no longer slide around.

One layer of 3.9 mm corrugated cardboard:

Beetle – 1x cardboard

The fancy gold & hologram decorations come from what’s surely non-laser-safe PSA vinyl sheets, cut by offsetting the top layer shapes inward a reasonable amount. The eyes come from random colored paper or painted chipboard.

Two layers of cardboard add up to 8 mm:

Beetle – 2x cardboard

That’s purple paper left over from the layered paper quilt blocks and, obviously, my glue stick hand is weak.

Three layers of cardboard makes each part half an inch thick:

Beetle – 3x cardboard

That bad boy needs black stripes on yellow in the universal “Fear me! I am a seriously dangerous creature!” danger marking.

The layers are laid out with crossed corrugations to make the part less bendy, which is more necessary for the relatively slender legs.

It’s two feet long and chewed up the better part of two Home Depot Extra Large moving boxes:

Beetle – LightBurn layout – 3x cardboard

The gridded rectangle represents the 700×500 mm laser platform.

The little ones are kinda cute and not too threatening:

Beetle Collection – 1.9mm

Yes, that is one of the Goldbug Variations.

2024-07-22
Slotted Elephants

Continuing the theme of slot resizing for various materials:

Elephants – 3.8 and 1.5 mm

The DXF pattern imports directly into LightBurn and requires the usual joining / closing / optimization before all the slots resize in unison. Doing the resize changed the slots from the original 3.0 mm to the 3.9 mm required to convert a cardboard moving box into a pachyderm.

The leg sections turned out to be a bit too thin for corrugated cardboard, so the corrugations came loose from the surface sheets, although the tail looked much more realistic. Stipulated: corrugated cardboard is the wrong material, but I really didn’t need a big MDF elephant looming over everything else.

The smaller elephants, both in 1.5 mm thick materials, come from a global resize applied through the LightBurn Numeric Edit toolbar:

LightBurn Numeric Edit – percent resize

The ratio makes the slots become the new size, with the entire rest of the design scaled around them. This works if you don’t much care about the overall size, but is rare in actual practice where you need a model “that big” with the slots fitting “that material”.

But the pieces just slid together:

Elephants – 1.5 mm detail

I put dots of cyanoacrylate in the acrylic joints, although the vapors scarred the surface enough to remind me why that’s the wrong adhesive for the job when you care about surface quality. Dots of wood glue hold the chipboard elephant together, with a quick shot of clear rattlecan paint to knock down the smell of the charred edges; I’d say the color came out about right.

All in all, they worked out rather well.

2024-07-19
Laser Test Paper Beam Alignment Targets

Having failed at making flexible plant tags, I figured using laser test paper to make laser test targets might work:

Test paper – target patterns – 2024-07-03

They descend from my original dot-mode laser beam targets:

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

The dots just barely punch through the back side (open in a new tab & zoom for more dots):

Test paper – target patterns back side- 2024-07-03

The plastic coating chars and buckles with each pulse, but remains in place:

Test paper – 2 shot – uncleaned – 2024-07-03

Wiping the surface removes the loose coating / ash / debris to expose the underlying charred paper core:

Test paper – 2 shot – wiped – 2024-07-03

Those are two pulses marking the ends of each axis, so the machine remains well aligned after the fourth-quarter tweak.

A single pulse shows the beam has a nice round shape with well-defined edges:

Test paper – 1 shot – wiped – 2024-07-03

In principle, the beam should be more intense toward the middle, but I suspect that’s beyond the paper’s ability to resolve the energy; the beam either burns through the coating or it doesn’t. In all those targets, the back surface of the paper remains undamaged.

Manila paper targets seem to have better energy resolution and take much less time to produce:

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

The black test paper will certainly come in handy for something, though.

2024-07-17
Clothes Washer Hose Bumpers

For obvious reasons, the water hoses tend to thump against the wall and the sheet-metal back of the clothes washer, so I added foam disks to mute the noise:

Clothes washer hose bumpers

They’re closed-cell polyethylene foam, laser-cut from a sheet about 15 mm thick. The cut is a yawning 2 mm wide near the top, but it pretty much doesn’t matter in this application.

The black line in the split is a snippet of the usual outdoor-rated foam tape, which probably won’t stick well to PE foam. If these fall apart, a cable tie around their waist should suffice.

The nice clip in the foreground is one of two intended to corral the drain hose. It’d be nice if LG included a few clips for the water hoses, but no matter where they were, the hoses would want to go elsewhere.

2024-07-10
Acrylic Grid Bathtub Soap Tray

Although the house has a shower stall, I want to fix the cracks in its floor before we use it, so we’ve been taking showers in one of the bathtubs. As is always the case, the soap tray / grab handle is positioned for someone reclining in the tub, making it both too low and too awkward for either of us.

Normally, I’d just stick a soap tray on the wall and be done with it, but the tub wall is covered with small tiles that defeat sticky cups; more permanent adhesives are not under discussion.

So I dropped a TrayInsert grid into a NotesHolder box, stuck them to the existing fixture with snippets of (regrettably black) outdoor-rated foam tape, and there it is:

Acrylic grid bathtub soap tray

You’ll surely not have 3.2 mm acrylic for the grid and 2.5 mm acrylic for the box, but those two linkies have the jawbreaker URLs required to regenerate exactly what I built using the incomparable boxes.py site and you can tweak them as needed.

The general concept had it stick out a bit from the fixture handle to let soap gunk drip into the tub, not down the wall, and to have an easily removable grid for cleaning. I doodled all manner of clever hooks to engage the ceramic handle before coming to my senses; this is a prototype, it may not solve the problem very well at all, so let’s find out if it works before making it better.

The WordPress AI urges me to remind you of the safety issues surrounding DIY projects. IMO, should you need such reminders, they won’t do you any good and you must immediately stop reading this blog.

Fair enough?

2024-07-09
Samsung Microwave Light Improvements

After replacing the gas / humidity sensor in the Samsung microwave, replacing the pair of 40 W (!) halogen bulbs with G8 LED bulbs didn’t pose much of a challenge:

Samsung microwave light – LED-ified reflectorized

Those are not the best bulbs for the application, as they’re allegedly equivalent to 20-25 W halogens, but I had some on hand from a previous relamping project and they seemed promising.

G8 halogens have a flattened section just above the pins that these G8 LED bulbs lack:

G8 halogen vs LED bulb – front view

It’s more obvious from the side:

G8 halogen vs LED bulb – side view

The curvature of the soft silicone LED body magnifies the components to look like they fill all the available space, but a little deft X-acto knife work flensed the body down to fit the microwave’s ceramic socket without exposing any of the electrical innards.

Because the LEDs dissipate only 3 W and barely get warm, I replaced the original translucent glass diffuser panels with (yes, laser-cut) clear 3 mm acrylic, then tucked a strip of aluminized mylar above the bulb to bounce some of the light from the upper chips down where it would do more good. I think it’s possible to melt the acrylic with a stovetop mishap, but we don’t make those kinds of recipes.

They’re not daylight shining on the stove, but they’re much brighter than the halogens at maybe 10% of the power.

2024-07-08
LightBurn Slot Resizing

LightBurn includes a Slot & Tab Resizer tool that automagically finds and resizes joints to adapt a design for whatever material thickness you might be using. To judge from the LightBurn forum threads, it doesn’t deal well with random designs fetched from the Interwebs, which suggests those designs were either never intended for laser cuttery or just badly laid out.

So I fetched a sheep from a typical sketchy source and attempted to resize its slots:

Sheep DXF import – slot resize problem

The tool looks for rectangular shapes within the Tolerance of the Old Material Thickness width, then marks their narrow ends with red highlights and their length with blue. Obviously, not all of the slots we humans see count as slots.

A closer look at one of the body shapes with a slightly larger Tolerance shows some of the problems:

Sheep DXF import – body

Using the Node Editor tool reveals two stray nodes near the bottom of the second slot from the left:

Sheep DXF import – slots

Zooming in and blowing out the contrast:

Sheep DXF import – slot bottom

Manually deleting those nodes doesn’t solve the problem, because two more errant nodes lurk at the top of the slot:

Sheep DXF import – slot top

You probably didn’t notice those at first glance, either. Those nodes may be very close together, but they still confuse the issue.

Rather than tracking down and deleting / adjusting those nodes one by one, you can apply the Optimize Shapes tool to squash the superfluous nodes into straight lines:

Sheep DXF import – optimized

Don’t smooth the shapes or fit them to arcs at this point, because both of those operations will round off the corners.

That may still leave a few nodes requiring manual intervention, as on the face shape:

Sheep DXF import – optimized leftover

But at least the problem becomes tractable:

Sheep and dinosaur flock

As the Bard put it, all’s well that ends well.

2024-07-03