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

CD/DVD Data Destruction: Mariner’s Compass Coasters
Snap all the Mariner’s Compass inset layers together into a single LightBurn layout:

Mariners Compass – stacked insets – LB layout

Scale it to 120 mm OD, delete the innermost circles under 15 mm diameter, then go wreck yourself some CDs and DVDs:

Mariners Compass Coaster – CD DVD tests

Those were test pieces to figure out speeds and powers starting from the polycarbonate settings used for the Guilloché DVD now serving as a coaster atop the laser.

When you’re looking to destroy the surface, then pretty doesn’t matter, but they come out surprisingly nice in a techie sort of way:

Mariners Compass Coaster – CD clear side test

That’s burned into the clear side of the CD before I figured out how to control the power at the starting points.

This CD-R came out a nice silver, with the tracks burned into the data / label side:

Mariners Compass Coaster – CD-R test

The polycarb tends to scorch & discolor at the starting point of each polygon, where the laser dwells momentarily after lighting up. Avoiding that requires setting the minimum layer power 1% below the Ruida controller’s minimum firing power. In this case, running the layer at 7% minimum with the controller set to fire at 8% completely eliminates the scorches.

The maximum power is about 10% for the clear side. The data side requires only 10% for lightly coated CD-R / CD-RW and maybe 25% for the heavily inked labels of pressed CDs (like the Dell reinstallation CD in the first picture). It helps to start with a vast supply of unwanted discs.

Suiting action to words:

Mariners Compass Coaster – CD data side finished

That’s a CD-R wrecked on the data side, stuck to an MDF disk with a cheap craft adhesive sheet and a cork disk wood-glued to the bottom. Carefully hidden here, the central hole sports a 15 mm chipboard disk contrasting horribly with the CD; it cannot be more than 1 mm thick to avoid having it stick up beyond the plastic surface and chipboard is what I have in that thickness.

The advantages of wrecking the data side:
- Leaving the clear side smooth, so crud won’t accumulate / grow in the grooves
- Absolutely, positively, utterly destroying the data track
The advantages of wrecking the clear side:
- Maybe breaking the seal formed by condensation under the mug / glass / cup
- Leaving the data side intact, so the coating won’t disintegrate and peel off the adhesive
In either case, however, I’m sure the data is gone.
2023-10-27
Laser-Cut Specialty Wipes

For reasons not relevant here, Mary asked for a bunch of small cloth wipes cut to a particular size. A few minutes with LightBurn for rectangle-drawing and array-fiddling produces a useful result:

Laser-cut wipes – cutting

The part about peeling away what you don’t want just never gets old:

Laser-cut wipes – on honeycomb

It turns out this is even faster than rotary cutter action, because you need not worry about the old T-shirt sliding around while you’re slashing away at it. Bonus: a free 2 mm radius on all the corners!

Let the pieces air out for a day on the patio and they’re ready for use.

2023-10-25
Tiled Einstein Coasters

When life gives you a sheet of tiled einsteins:

Einstein tiling

You can make coasters:

Einstein tiled coasters

They’re rattlecan colored chipboard atop MDF atop cork, with the tiles cut from half a dozen sheets of einsteins. The lighter colors suffered from ineffective tape masking during cutting, producing more smudging than I’d like, but overall they look pretty good.

I was surprised at how dull the black surround turned out and how good the gray appears: rapid prototyping & iteration in full effect.

Unlike the layered paper version, these require a great deal of fiddly handwork.

I hope the MDF will prevent the premature warping afflicting the chipboard-on-cork coasters. Perhaps shooting the assembled coasters with a clearcoat would help, although you do want coasters to be a bit absorbent, lest they stick to wet cups / mugs / glasses in humid weather.

2023-10-24
Layered Paper: Einsteins

Go to the source and bring back a suitable number of tiled einsteins:

Einstein tiling

Import the bitmap into LightBurn, fiddle with the tracing until it lays down two lines along each border, apply a 1 mm inset to all the tiles, then scale & crop & delete to fit a 170 mm square:

Einsteins – LB paper – top layer

Cut one of those sheets, tape it to a sheet of white paper, fire up a calculator, generate a random number, write the first digit in the upper-left tile, and iterate to fill in all the tiles.

Duplicate that layout and delete all the tiles marked with a zero to get the next layer.

Iterate for all ten layers:

Einsteins – LB paper cuts

Set up the fixture, do the Print-and-Cut alignment, then cut all the layers with different colors:

Layered Paper cutting fixture – in use

Assemble the layers with some stick adhesive:

Layered Paper – Einsteins

Frame it and admire:

Layered Paper – Einsteins

It’s way busier than the quilt blocks, but I like it.

2023-10-23
Layered Paper: Mariner’s Compass Insets

Given the geometry of the Mariner’s Compass block:

Mariners Compass – top level shapes – LB layout

Applying increasing insets to that top level produces a beveled result:

Layered Paper – Mariners Compass – offsets – detail

Seen from a distance, you need oblique light to make any sense of it:

Layered Paper – Mariners Compass – offsets

It’s made from random sketch paper, rather than cardstock, and we all know how much the paper matters.

2023-10-20
Layered Paper: Cutting & Assembly Fixtures

Time spent making a fixture is never wasted time:

Layered Paper cutting fixture – in use

The general idea: securely hold a piece of paper flat while cutting it, so that it cannot move or warp, while letting the cut pieces fall out without snagging on anything underneath. The sheet holder I made a while ago worked reasonably well, but those thin metal blades tend to warp while cutting small patterns in restricted areas and the pieces definitely don’t fall free.

The simple fixture I use while assembling the paper layers consists of four rivnuts poking through a chipboard upper layer, with a craft paper layer around the rivnut washers on the bottom:

Layered Paper – alignment fixture

The cutting fixture uses a similar layout around a hole for freely falling chips:

Layered Paper cutting fixture – installed

Next time, I’ll remove those three bars across the hole, because the MDF doesn’t need any support. Nearly all the chips fell out, so the fixture worked as intended.

I trimmed the flange off the rivnuts so they would sit flat on the MDF:

Layered Paper cutting fixture – trimming rivnut flange

That’s the kind of job chuck stops really simplify.

The cutting fixture requires pre-cutting paper into 200 mm squares with four 5 mm corner holes, which can be done three-abreast on the platform bars, then putting each sheet in the fixture to cut the shapes. That’s not much of a disadvantage compared to messing up an unsupported sheet.

The cutting fixture has crosshair targets to align a LightBurn template using Print-and-Cut, thus eliminating the need to precisely locate the fixture on the platform. The finger-crushingly strong neodymium bar magnets do a fine job of holding the MDF in place on the steel platform.

The small cutout rectangle in the lower right corner frames the sheet number, done in binary code with 0 = 1 mm circle and 1 = 2 mm circle:

Layered Paper cutting fixture – layer binary code

That’s the underside view of a completed stack with the 5 mm lower-right fixture hole on the left and the code for layer 11 = 0b1011 reading backwards. The small 0 holes have two lobes showing the Print-and-Cut alignment was off by maybe 0.3 mm; the off-center hole was in the blank sheet.

Obviously, cutting tiny circles with a big laser at 300 mm/s doesn’t produce perfect results. You can see small wiggles in larger shapes:

Layered Paper cutting fixture – cut wobbles

Unless you’re trying hard to find a problem, you’ll never notice them.

2023-10-19
Layered Paper: Chimney Swallows Block

The Chimney Swallows block from page 128 of Beyer’s book:

Chimney Swallows – Beyer 128

The tool (blue & orange) and top cut (red) layers:

Chimney Swallows – LB layout

The long radial blue tool lines simplified selecting them when mirroring / duplicating the cut polygons around their symmetries. The orange tool circles aligned various midpoints / vertices / features during construction.

The inward curve along the outer edge started as a triangle with a node at about the middle of the curve. Deleting that node left the remaining two sides overlapped, but dragging one of them to match the curve worked OK. There’s probably a better way.

That curve defines the outer edges of the shapes along it, so I drew polygons from the corner intersections and dragged the outer edge to match the curve at high zoom.

The shape remains selected after dragging the side, which meant I could immediately apply a 1 mm inset to create the cut lines.

To my surprise, the swallow bodies are straight-sided polygons!

After taking advantage of all the symmetries, knock out the shapes defining each layer:

Chimney Swallows – LB paper cuts

The swallows look like F-117 Nighthawks to me:

Layered Paper – Chimney Swallows – Beyer 128

Maybe I have the colors wrong:

Layered Paper – Chimney Swallows – Beyer 128

Fly away!

2023-10-18