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.

Category: Software

General-purpose computers doing something specific

ssh_agent vs. The New Hotness
A recent Manjaro update killed whatever magic held the passwords used for public-key ssh access from my desktop box, requiring me to remember the passords and type them correctly.

After considerable thrashing around doing what I thought I knew about ssh_agent (which, yes, was being autostarted to no avail), it seems that thread applies and the fix now requires creating /etc/profile.d/gcr-keyring.sh with this burst of line noise:
```
export SSH_AUTH_SOCK=$XDG_RUNTIME_DIR/gcr/ssh
```
Then tell systemd about it:
```
systemctl --user enable gcr-ssh-agent.socket
systemctl --user enable gcr-ssh-agent.service
```
Whereupon, after a reboot presumably causing systemd to make the right thing perform the right act at the right time, It Just Worked™.

I used to have some mild sysadmin mojo, but obviously if you don’t do it all the time, everything you think you know becomes wrong.

The WordPress AI did generate an image based on the above text and the prompt linux overlapping windows on monitor:

WP AI Image – linux overlapping windows on monitor

Which looks a lot like those stock photos filling otherwise empty space in spammy web pages, doesn’t it? In point of fact, the AI Feedback on Post had this to say:

While the AI-generated image may align with the content, consider using original or more contextually relevant visuals to maintain the professional look of the website.

Couldn’t have put it better myself. Thank you, AI image & text generators, for your help.
2024-05-28
Juki / Arrow Sewing Table Insert Filler

Mary’s Juki TL-2010Q sewing machine sits in an Arrow Gidget II sewing table with a clear acrylic insert filling the opening:

Juki TL-2000Q in Gidget II table

Before the insert arrived (it had month of leadtime), I hacked out a temporary cardboard insert:

Juki temporary table insert

Although it may not be obvious from the picture, unlike my cardboard insert, the acrylic insert does not fill the tabletop hole to the immediate right of the machine:

Custom Inserts are U-shaped, designed to fit around all 3 sides of your sewing machine

Shortly after the insert arrived I hacked a temporary filler, for which no pictures survive, to keep pins / tools / whatever from falling to their doom. This turned out to be a blessing in disguise, because she wanted the machine positioned an inch to the right of its intended spot to leave enough space for a finger to reach the bobbin hatch latch.

I then promised to replace the ugly cardboard filler with a less awful acrylic filler and finally got it done:

Juki TL-2000Q in Gidget II table – insert filler

The stack of cardboard prototypes show iterative fit-and-finish improvements, with the odd shape on the top serving to measure the machine’s 25 mm corner radius by comparison with known circles.

The insert filler is made from smoked gray acrylic, because I have yet to unpack the acrylic stockpile and may not, in fact, have any clear 6 mm acrylic, so we’ll regard this as a final prototype pending further developments. It did, however, confirm the laser survived the move, which was pretty much the whole point.

The end of the machine is not a straight line. Part of the iteration was measuring the curve’s chord height to calculate the circle’s radius, which turned out to be 760 mm:

Juki Insert Filler – end chord circle

With that in hand, a few Boolean operations produced the filler shape:

Juki Insert Filler

A pair of silicone bumper feet stuck to the side of the Juki hold the left edge of the filler at the proper level.

For the record, the smoked acrylic came from a fragment of a Genuine IBM Printer stand I’ve had in the scrap pile since The Good Old Days:

Etsy listing – Vintage IBM Printer Stand

The LightBurn layout as an SVG image:

2024-05-08
CD / DVD Data Destruction: Fixturing

Cutting an array of 120 mm holes in chipboard produces a fixture for wrecking CDs:

Laser-engraved CD fixture – loaded

In addition to the obvious cutouts, the fixture has four corner targets:

CD 5×3 Fixture

Which you use with LightBurn’s Print-and-Cut alignment:

Laser-engraved CD fixture – alignment

With fifteen Guilloche swirly patterns imported and snapped into the template and the template aligned to the fixture, Fire The Laser:

Laser-engraved CD fixture – legend

The whole process takes a bit under 25 minutes:

Laser-engraved CD fixture – complete

Which produces a stack of glittery proto-coasters:

Laser-engraved CD fixture – results

Although they’re all pretty-like, turning them into Real Coasters requires a cork base, MDF in the middle, wood glue, and adhesive sheets, all of which seems entirely too much like work.

There ought to be an easier way …

2023-11-09
Guilloche Generator: Now With Layers & Colors

Tweaking the GCMC Guilloche generator to define colors for the SVG layers produces a pattern ready for LightBurn:

Guilloche – SVG layer colors

The blue layer runs at 300 mm/s at 10% PWM to carve trenches all over the CD / DVD surface, which should render it unreadable:

Laser cut CDs – Guilloche patterns

The laser runs much faster than a drag knife or a diamond engraving tool!

The reddish layer uses Dot mode to draw the legend around the hub:

Laser-engraved CD – legend detail

The characters are 1.5 mm top-to-bottom, with dots just under 0.2 mm diameter on 0.2 mm centers.

Stipulated: there’s no real point to annotating a CD that you’re wrecking, but the code was already there, so why not?

So the overall workflow involves generating an SVG image, importing it into LightBurn with those layers set up with the appropriate cut parameters, using the Three-Point Circle Center Finder tool to align the pattern with the CD, then Fire The Laser. Alignment stops on the laser platform eliminate the need to realign every pattern, so it boils down to running the generator script enough times, importing a batch of patterns, then snapping each one into place and cutting it.

They’re kinda pretty, in the usual techie way:

Laser cut CDs – Guilloche patterns

I have a lot of scrap discs, some ideas of optimizing the process, and a general notion what to do with the prettier results.

The GCMC source code and Bash driver script as a GitHub Gist:

2023-11-08
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

Under-shelf Kitchen Light Bracket

Quite a while ago I’d added another LED strip to the under-cabinet light array, because the little cutting boards & suchlike on a wire shelf blocked the light, but fastened it in place with ugly wire ties.

Finally I found a Round Tuit on the desk for brackets mounting the strip directly to the shelf:

Kitchen Light Bracket - shelf blocks - solid model — Kitchen Light Bracket – shelf blocks – solid model

Ram a pair of brass inserts in the holes, screw the strip in place, snap the brackets between the wires, and it’s much better:

Kitchen Light Bracket - installed — Kitchen Light Bracket – installed

Stipulated: those wire ends look awful. Fortunately, they’re normally hidden by the cutting boards and suchlike on the shelf.

Although it looks precarious, the rounded sides (seem to) have enough grip on the wires to hold the LED strip in place. We’ll see how well that works in practice, but the idea was to avoid anything sticking up above the wires to collide with the stuff on the shelf.

The blocks emerge from a chunk of code glommed onto the original OpenSCAD program:

ShelfWireDia = 3.2;
ShelfWireOC = 1*inch;
StrutWireDia = 6.3;

ShelfBlock = [ShelfWireOC,LEDEndBlock.y,(0.8*ShelfWireDia + StrutWireDia/2)/cos(180/8)];
echo(ShelfBlock=ShelfBlock);

LEDHoleOffset = [ShelfBlock.x/2 - (6.0 + ShelfWireDia/2),6.0];  // from Y+ and X±
LEDHoleDia = 3.0;

ID = 0;
OD = 1;

M3Insert = [3.0,4.0,4.2];   // short M3 knurled insert

<<< snippage >>>

module ShelfBlocks(Side=1) {

  difference() {
    translate([0,ShelfBlock.y/2,ShelfBlock.z/2])
      cube(ShelfBlock,center=true);
   translate([Side*LEDHoleOffset.x,ShelfBlock.y - LEDHoleOffset.y,-Protrusion])
      rotate(180/8)
        PolyCyl(M3Insert[OD],M3Insert[LENGTH] + 2*ThreadThick,8);
    translate([-2*ShelfBlock.x,-StrutWireDia/4,0])
      rotate([0,90,0]) rotate(180/8)
        PolyCyl(StrutWireDia,4*ShelfBlock.x,8);
    for (i=[-1,1])
      translate([i*ShelfWireOC/2,-ShelfBlock.y,(StrutWireDia/2 + ShelfWireDia/2)/cos(180/8)])
        rotate([-90,0,0]) // rotate(180/8)
          PolyCyl(ShelfWireDia,3*ShelfBlock.y,8);
  }
}

<<< snippage >>>

if (Layout == "ShelfBlocks")
  for (i=[-1,1])
    translate([i*(ShelfBlock.x/2 + 3.0),0,0])
      ShelfBlocks(i);

Should’a done that years ago …

2023-10-26

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