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-Cut Envelope Opener

As practice in using the laser to engrave a figure to a known depth, this seemed appropriate:

Envelope Opener – original

The black envelope opener on the right came in a long-ago surplus deal and worked really well, which I cannot say for the retail replacements I got a few years back.

The tan envelope opener on the left is an obvious case of IP theft, copying the size and shape using a scanned image:

Classic opener – knife blades – scan

The two blades seemed like good candidates, with the lower one winning the contest:

Kobalt 78010 Mini Utility Knife Blade mask

Although the pack of “mini utility knife blades” sports a Lowe’s Kobalt part number, they no longer carry that item. You can find plenty of identical blades elsewhere, so they’re not a rare collectible and I have plenty of backup.

Put the outline of the opener on a cut layer, put the blade on an engraving layer, orient appropriately, and make a mirror-image duplicate:

Envelope Opener – LB Layout

The original opener is a touch over 3 mm thick, so the settings engrave 0.25 mm into the surface to make a blade pocket, then cut the shapes from 1.5 mm TroCraft Eco:

Envelope Opener – cutting

After all the cutting was done, it looks about as you’d expect:

Envelope Opener – interior layout

Slather with yellow PVA wood glue and apply too many clamps:

Envelope Opener – clamping

Next time around, I’ll round off the edges before assembly, but that’s in the nature of fine tuning:

Envelope Opener – detail

The TroCraft sheet engraves so cleanly that, were I to go into mass production, I’d set up a fixture for grayscale engraving shaping the perimeters.

Obviously, this makes no economic sense, but it does produce a considerable amount of satisfaction, which is pretty much all that matters for such things.

2023-02-27
Lift Chair Foot Risers
The fuzzy felt feet on the lift chairs raised them enough to slide both floor lamp bases underneath with the backs in the upright state, but reclining the chair with the light more than halfway back along the side of the chair crunched the lamp base.

Rather than print taller fuzzy feet, which takes a long time, I knocked out two quartets of laser-cut risers:

Lift Chair Foot Riser – installed

They’re six layers of 3 mm MDF or plywood:

Lift Chair Foot Riser – assembled

The LightBurn layout makes one riser:

Lift Chair Feet Extenders – LB layout

The upper two discs become two rings and two pads, with the lower two disks forming the middle layers. The ring ID clears the chair foot and the pad OD fits into the existing printed fuzzy felt foot. The two cuts making that happen leave the thinnest imaginable ring of MDF in place.

The tiny circles cut holes for 11 mm snippets of 1.1 mm hard steel wire aligning the layers:

Lift Chair Foot Riser – locating pins

Assembly sequence:
- Tap two pins into a ring
- Butter the ring with yellow wood glue
- Slide the other ring over the pins
- Butter
- Slide a disk over the pins
- Drive a pin into a pad
- Butter
- Slide the other pad over the pin
- Butter
- Slide a disk over the pin atop the pads
- Butter one of the disks
- Slide the disks together over all three pins
- Tap all pins below their surface
Make two and clamp them together to ensure everything sticks firmly.

Repeat to make four risers

Install, recline, and enjoy not hearing a mysterious crunch from the lamp base.

The alert reader will note the 6 mm stack of two pads leaves a slight gap above the printed foot. Turns out the recess is 5 mm deep and I decided to just live with a 1 mm gap down there.
2023-02-16
Shoulder PT Pulley: Last 10% Manufacturing

Mary’s PT requires a Shoulder Pulley, so I got one that seemed better constructed than the cheapest Amazon crap. In particular, this view suggested the pulley ran on a bearing:

Slim Panda Shoulder Pulley – detail view

Which turned out to be the case, but, also as expected, the whole thing required a bit of finishing before being put in service.

It’s intended to hang from a strap trapped between an interior door and its frame. The strap was intended to attach to the block (a.k.a. “Thickened base”) through a breathtakingly awkward pair of low-end carabiners:

Slim Panda Shoulder Pulley – carabiners

Which I immediately replaced with a simple, silent, sufficiently strong black nylon cable tie:

Shoulder PT Pulley – block hardware

Rather than let the metal block clunk against the door, it now sports a pair of cork-surfaced bumper plates:

Shoulder PT Pulley – side plates installed

A doodle of the block dimensions:

Shoulder Pulley – dimension doodle

Which turned into a simple LightBurn layout:

Shoulder PT Pulley Side Plates – LB layout

The blue construction lines represent the actual block & pulley, with the red cut lines offset 2 mm to the outside to ensure the metal stays within the bumpers. It’s possible to pick the block up and whack the pulley against the door, so don’t do that.

Cut out two pieces of 3 mm MDF, two pieces from a cork coaster (covered with blue tape and cut with the paper backing up), peel-n-stick the cork to the MDF, put double-sided foam tape on the block, peel-n-stick the bumpers, then hang on the attic door.

Now it works the way it should!

The LightBurn SVG layout as a GitHub Gist:

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2023-02-07
Ersatz Library Card: Fixed

Sharper eyes than mine pointed out I misspelled Poughkeepsie, so I took advantage of the opportunity to make the whole thing look better:

Library card tag – revised front

It turns out the low-surface-energy tape stuck like glue to the acrylic tag (because that’s what it’s designed for) and peeled right off the laminating film on the printed paper. So I stuck some ordinary adhesive film to the back of the new paper label, left its protective paper on the other side, cold laminated the film+paper, laser-cut the outline, peeled off the back side of the laminating film with the protective paper, and stuck the new adhesive to the LSE tape still on the tag.

I have no idea how well this will work out in the long term, what with two adhesive layers bonded to each other, but this whole thing is in the nature of an experiment.

2023-01-19
Holly Coaster: Improved Mirror Setup

Other than demonstrating that it’s possible to laser-engrave a 3 mm deep pocket in a ¼ inch thick piece of scrap paneling, the process didn’t have much to recommend it:

Holly Coaster – mirror flaws

So I re-did the layout to put the 3 mm mirror in 3 mm thick plywood:

Holly Coaster – overview

The coaster has a self-adhesive cork pad on the bottom, which required an intermediate adhesive layer holding the aluminized Mylar reflector on the bottom of the mirror to brighten the colored areas.

The LightBurn layout shows all the pieces:

Holly Mirror Coaster – LB layout

The plywood cuts with the good side down, although “good” is certainly a judgement call with B/BB grade plywood. I cover the good side with blue painter’s tape to reduce scorch marks. In a real application, you’d do some sanding and finishing, probably before cutting; in this case, I want to see what happens to bare wood in coaster duty.

Engrave and cut the mirror with the backing upward:

Holly Coaster – removing mirror layer

The tracer rounds may be burning aluminum.

I colored the engraved areas with fat-tip permanent markers, despite knowing the alcohol will crack the acrylic. In real life, you’d use spray paint, probably with laser-cut tape masks.

The adhesive layer extends 2 mm beyond the mirror perimeter to stick onto the bottom face of the plywood:

Holly Coaster – adhesive placement

Peeling off the paper reveals the adhesive tape stuck to the back side of the mirror:

Holly Coaster – adhesive exposed

Apply the similarly embiggened aluminized Mylar to the adhesive:

Holly Coaster – mylar placed

Cutting the holly shape directly from the original foot-square adhesive sheet lets me tuck smaller shapes into the remaining uncut areas. In a production environment, however, joining the Mylar and adhesive (perhaps using pre-cut squares), then cutting them as one sheet would definitely simplify the process.

Then peel-n-stick a cork disk (thus explaining why the plywood is exactly 4 inch OD) on the bottom:

Holly Coaster – edge view

I’ve been aligning the cork by feel, which explains the half-millimeter overhang along the right side. Inexplicably, I have yet to justify an alignment fixture.

The LightBurn SVG layout as a GitHub Gist:

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2023-01-09
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