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

Snowflake Coasters: Kerf Compensation

A flurry of snowflake coasters:

Snowflake Coaster – assortment

The two on the left are the original snowflakes with interchanged innards and, perforce, no kerf compensation.

The upper-left coaster has a wood flake surrounded by acrylic, which makes a sharp clack when you set a glass down on it. The wood surrounds emit a much more pleasing clunk.

The next two have 0.1 mm compensation applied to their acrylic snowflakes, which produces snug fit (original on the left, compensated on the right):

Snowflake Coasters – kerf corr 0.0 vs 0.1 mm

Applying 0.2 mm compensation makes the flakes impossible to push in, so the true compensation is somewhere just over 0.1 mm. I think you could optimize for a specific wood and acrylic combination, but, as with 3D printing, any change requires something different.

The little arrowhead shapes tend to get lost, so collecting them on a strip of tape while you’re hunting in the chip tray helps:

Snowflake Coasters – plywood cutouts

The dark flake on the right got a coat of walnut stain, as did the two darker coasters in the first picture. It looks better in person than in the photo, although Mary still thinks the lighter wood sets off the white acrylic just fine.

The two large (120 mm OD) coasters fit my 20 ounce mugs, with the Nanook Memorial Coaster in the lower right.

2023-01-05
Ersatz Library Card

The rather battered library card on the bottom has been rattling around on Mary’s keyring since late in the last millennium:

Library card tags – front

I made the one on the top as a replacement, because Mary wanted one, but the library no longer issues keyring cards these days.

The front surface was laid out in The GIMP, inkjet-printed on good paper, cold laminated, laser-cut with LightBurn’s Print-and-Cut process, then affixed to the acrylic tag with really good double-sided tape:

Adriance Card – LightBurn PnC layout

I cut and applied the tape after cutting the tag, but the next time around I’ll apply the tape to the stock and cut both together to improve the edge alignment.

The rear surface data is engraved directly into the same Trolase laminated acrylic I used for the plant tags:

Library card tags – rear

The smaller text uses dot mode and the bars & number are engraved:

Library card tag – detail

In retrospect, it’s painfully obvious the engraving passes should run parallel to the bars, rather than perpendicular to them.

The barcode uses Codabar encoding generated with a Codabar font. I scaled the graphic block slightly larger than the original in the hope of making it more readable.

I determined the start and stop characters by trial and error; for this card, they’re A and B. Which could, perhaps, stand for Arlington Branch, but might equally well be coincidence.

It worked perfectly on the first scan at the library counter and apparently went entirely unnoticed. I trust duplicating a library card does not constitute a federal offense.

For what should be obvious reasons, however, I’m not posting the LightBurn layout.

2023-01-04
Sears / Kenmore Vacuum: Design Tweakage

Despite cogent reasons for not buying another Sears vacuum cleaner, the brand currently represents a local maximum of the desirability curve: cheap, readily available, works well enough, and, surprisingly, bags for the defunct Progressive (whatever that meant) vacuum seem to fit just fine.

But the new one does come with some annoyances, starting with trendy dark gray engraved / molded control markings:

Sears Vacuum – power and cord controls

Quick: from the other end of the vacuum hose, which one must you stomp to turn it off?

Well, I can fix that:

Sears Vacuum – marked power switch

After the Progressive’s bizarre and overly complex tool fittings, the new unit has tools that slip-fit onto a classic steel tube, which means I can throw all those adapters into a box of 3D printing examples for use in the unlikely event I ever do another show-n-tell presentation.

It also has a simple rotating suction control ring at the handle:

Sears Vacuum – marked suction vent control

Which, as you can tell from the fluorescent tape, featured the same embossed and unreadably small dark gray markings.

Because that ring and its glaring tape is invisible from the user’s end of the handle, I eventually duct-taped the ring in position to prevent another inadvertent loss-of-suction accident.

If we ever need reduced suction on a regular basis, I’ll conjure a better ring from the vasty digital deep:

Sears Vacuum – suction vent doodle

I obviously no longer form deep emotional attachments to these things …

2023-01-03
Seasonal Snowflake Coasters
The rattlecan chipboard coasters having passed their Best Used By dates, I figured a more durable seasonal version was in order:

Snowflake Coasters – overview

I laid out the design with the intent of cutting an acrylic snowflake with a bit of compensation to fit snugly into a plywood background:

Snowflake Coaster – LB layout

At the last moment I realized I could just cut two of the patterns on the left, swap the snowflakes, and get two coasters with very little scrap:

Snowflake Coasters – detail

Mary thinks the gap between the snowflake and the background looks OK. I’m not convinced, but studying the results suggests applying enough kerf compensation to close the largest gaps would results in the rest of the flake not fitting into its socket. Plus, of course, you’d have more scrap.

Embiggening the small dagger-shaped pieces around the center would be an improvement. Perhaps cutting those as a separate operation after arranging them in a corner would work.

Protip: Align the grain in those daggers with the rest of the plywood, because It Will Be Very Obvious if you don’t.

Applying a nice wood stain / finish to the plywood, perhaps before cutting it out, would certainly improve the result.

Invisible on the bottom: self-adhesive cork disks eliminating the need to glue the pieces to something else. I had thought of a blank plywood or MDF disk, but came to my senses just in time.

The original SVG fell with a blizzard from one of the many SVG snowflake generators out there. Because LightBurn uses only the stroke centerlines of SVG images and ignores the stroke width, it required some tweakage before becoming a coaster.

After saving an SVG flake from the blizzard, fire up Inkscape:
- Import the SVG file
- Center it in whatever page you’re using
- Ungroup the flake from the frame (if it has one)
- Delete the frame to leave only the flake
- Select the flake
- Invoke Path → Stroke to Path
- Save as an SVG image under a new file name
Then fire up LightBurn:
- Import the tweaked SVG file
- Assign a layer with line (rather than fill) parameters
- Ungroup to separate the flake’s strokes
- Weld the strokes together to remove the overlaps
- Wrap a coaster outline around it
- Resize the flake as needed
- Set layer parameters as needed
- Duplicate the flake
- Embiggen as needed
- Unleash the laser!
The LightBurn SVG layout as a GitHub Gist:

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view raw Snowflake Coaster – LB Layout.svg hosted with ❤ by GitHub
2022-12-29
Splined Neck Cozy Pattern

Mary made a neck cozy based on a Craftsy description using a pattern I’d extracted from the low-res photo and rescaled to the proper size. The perimeter came out grittier than I like, but the laser had no trouble chopping it from a sheet of paper, and she cut smoothly around the lumps:

Neck Cozy mask – right

It looks better on her, but you get the general idea:

Neck Cozy – rev 1 finished

After some experience, however, she wanted to lengthen the top and bottom seams to improve the way it draped, which meant I had to modify the extracted pattern. The original pattern in the Craftsy photo was hand-drawn (which is perfectly fine) and the two halves were of two different sizes; we decided to work with the left half and produce a symmetric result.

Rather than fiddle with the bitmap, I drew a rectangle around the outside of the left pattern mask, converted it to a path, moved the nodes to key locations, then fiddled with the control points to lay the splines along the perimeter:

Neck Cozy pattern – LB splines

Removing the bitmap makes the splines much more obvious and shows the much smoother perimeter:

Neck Cozy pattern – LB extended splines

Adding a few nodes to change the splined shape is much simpler than fiddling with the bitmap, particularly when tweaking their position as directed by someone who knows how the fabric will eventually take shape.

Add fiducial marks and a label, duplicate the shape, mirror it to get the other half, and fire the laser:

Neck Cozy pattern – as cut right

Fabric cutting isn’t in my wheelhouse, but I made the offer …

The LightBurn layout as a GitHub Gist:

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2022-12-27
More Laser-Cut Shop Wipes

A filled box of worn-out clothing produced more shop wipes:

Laser-cut Shop Wipes – assortment

The last few pieces were a bit finicky, but provided good on-the-fly practice with linear arrays:

Shop Wipe – LightBurn setup

This trick never grows old:

Laser-cut Shop Wipes – as-cut

I washed those neat stacks (in their very own load!), which didn’t turn out well:

Laser-cut Shop Wipes – washed

They’ll get used no matter what they look like!

2022-12-23
Ed’s Fireball Cocoa: Magnetic Stirring

An addition to my morning cocoa makes it mmmm turn out better:

Cocoa magnetic stirring – magnet

Start with an ounce of milk, dump in the rest of the ingredients, spin up the stirrer, and slowly add the 8 oz of milk that just reached the end of its 70 seconds in the microwave:

Cocoa magnetic stirring – vortex

The green LED to the left of the speed knob runs from the PWM signal driving the motor, so it flickers visibly and interacts with the camera shutter.

Let it whir for a few minutes until all the cocoa bombs vanish and it’s ready for another 33 seconds in the microwave.

The most recent batch of cocoa arrived in an exceedingly vacuum-packed mylar bag, to the extent the bag resembled a brick and the solid cocoa within fractured into big chunks. Bashing the chunks with a fork got tedious enough to remind me of the stirrer I got to mix titanium dioxide for the yet-to-be-tried glass engraving.

Back in the day, the teflon shell molded on the magnet had a rib around its middle to make it pivot neatly on a point contact. This one is flat and dislikes spinning on the slightly concave cup bottom.

Protip: fish the stirrer out before sipping the cocoa, lest it become a tiny cow magnet.

2022-12-22