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.

Author: Ed

Laser Printer vs. Laser Cutter: Alignment & Scale

The setup for cutting the Tektronix Circuit Computer decks looks like this:

Tek CC – Bottom Deck cutting setup

Four neodymium bar magnets hold the corners flat against the honeycomb and the neo disk magnet pins the center down, thus ensuring the red alignment laser meets the cutting beam at its focal point on the surface.

The triangular shapes mark the OD of the perimeter (177.8 mm) plus twice the cut margin on each side (2×2 mm), with the tick mark in the upper right ensuring I slap every deck down in the proper orientation. Aligning the two right marks to the edge of the honeycomb frame (with a straightedge for some offset) aims the deck’s 0° index along the cutter’s X axis.

The cut pattern origin is, naturally enough, the center point of the deck, so aligning the red dot to the center cross should put the OD cut at the place all around the perimeter. For confirmation, I fire the laser (“A single ping, Comrade.”) and verify the hole is in the middle of the cross.

Before cutting the deck, the laser also marks the corner shapes, so this may come as some surprise:

Tek CC Middle Deck Corner Targets

The laser printer (a venerable HP LaserJet 1200) produced the dark triangles and the laser cutter (a new OMTech 60 W) burned the light brown marks. The picture is a composite of the four corners, with the blank center removed to concentrate on what’s important.

The scrawls give the edge-to-edge distances in both inches (because that was the scale at hand) and converted to millimeters (because that’s how it’s laid out), with the L suffix for the laser marks.

What’s of interest is that you can’t overlay the two sets of marks by a combination of scaling and rotation with the centers (not shown) of the two patterns pinned together.

The laser measurements differ from the ideal 181.8 mm by 0.1 mm vertically and 0.4 mm horizontally. This may require dinking with the scale factors in the firmware, which I recall having weird values.

The LaserJet is definitely not a precise instrument, off by 0.4 mm vertically and a millimeter horizontally, with considerable variation. I think this comes down to unrealistic expectations for toner stuck to a flexible sheet wrapped around rollers and heated enough to melt dust into the fibers.

More study is indicated …

2022-06-13
Memory Is the First Thing to Go

An email from Amazon arrived a few days ago:

Purchase Reminder – not found

I suppose we’re even, because I have no recollection of setting a Purchase Reminder on anything at any time.

By default, my email client does not display remote content in messages, which chops out the cute pictures, as well as killing all the cruft and tracking widgetry infesting commercial email these days.

2022-06-11
Pine Pollen Season

When the driveway runs yellow in the rain, it’s pine pollen season:

Pine Pollen Season – Driveway Flow

Our robot vacuum snuffles up quite a collection of dust:

Pine Pollen Season – vac filter B

Peeling a layer of the usual fuzz off the filter reveals the pollen:

Pine Pollen Season – vac filter A

This, too, shall pass and my eyes will rejoice.

2022-06-10
CR2032 Lithium Cell Lifetime

The Dell Optiplex 9010 acting as a file server woke up dead after I plugged it in after returning from a road trip. Its ID sticker shows a manufacturing date almost exactly nine years ago and the problem was exactly what you might expect:

Optiplex CR2032

I’d never measured 100 mV on a CR2032 before.

Because the Optiplex runs headless in the basement, diagnosis required hauling it upstairs, booting it with a display & keyboard, whacking the date into the current decade, then resetting a few other vital bits.

The electrolytic caps looked to be in fine shape, though.

2022-06-09
Sunbeam 3035 Clothes Iron: Rusted Spring

Some weeks ago the Sunbeam clothes iron Mary uses for her quilting projects stopped retracting its cord and a few days ago the entire compartment holding the cord spool simply fell off:

Sunbeam 3035 Iron – detached cord compartment

One plastic stud and two thin plastic tabs held the compartment onto the rest of the iron. How they lasted this long I do not know, but they are neither replaceable nor fixable.

When you see badly rusted screws in an electrical device, you know the story cannot end well:

Sunbeam 3035 Iron – cord connections

And, indeed, it hasn’t:

Sunbeam 3035 Iron – retraction spring rust

This being a steam iron, it has a water tank that gets filled through an awkward port with a sliding cover. Mary is as conscientious a person as you’ll ever meet, but the occasional spill has certainly happened and it is painfully obvious the iron’s designers anticipated no such events.

The coil spring had rusted into a solid mass:

Sunbeam 3035 Iron – spring rust – detail

I removed the spring, soaked it in Evapo-Rust for a few hours, then cleaned and oiled it:

Sunbeam 3035 Iron – relaxed spring

Rewinding and reinstalling the spring showed it has lost its mojo and cannot retract more than a few feet of cord.

She’s in the middle of a quilting project and will replace the iron with whatever cheapnified piece of crap might be available these days. Similar irons have reviews reporting they begin spitting rust after a few months, which suggests the plastic tank or stainless steel hardware in this one have been cost-reduced with no regard for fitness-for-use.

2022-06-03
Laser Imaging: Glass vs. Titanium Dioxide

A stack of glass shelves has long awaited this fate:

Glass engraving – front overview

As with the paving tile, the image came from a grayscale photo run through a halftone filter. The leftmost four images were burned through a titanium dioxide layer poured / spread over the glass surface. The rightmost two were burned directly into the glass, serving as a reminder that glass absorbs infrared radiation. The power levels varied from 15% to 60%, although I wasn’t taking notes, with a 400 mm/s scan speed.

It looks much the same when viewed from the rear:

Glass engraving – back overview

Although the process is often described as blasting chips out of the glass, there’s definitely melting going on. A closer look at the middle image in the top row, with darker gray patches from titanium fused into the glass:

Glass engraving – partial TiO2 fusion

Some pits have only a tiny dot of titanium, almost invisible against the glare from the glass around the rim:

Glass engraving – plain detail

A very close look shows damaged glass, with titanium in some of the pits:

Glass engraving – TiO2 detail

Higher laser power fuses more titanium into contiguous areas that appear much darker, as in the middle bottom image:

Glass engraving – full TiO2 fusion

This is loosely based on commentary in two LightBurn forum threads about variations on what’s known as the Norton White Tile Method, with more examples on the V1 Engineering forum. Just applying TiO₂ seems less awful than various paints / primers / whatever, with the additional benefit of eliminating the overhead of spraying / cleaning up.

The secret seems to be having enough power to chip the glass and decompose the TiO₂ into darker titanium, while not blasting the result entirely off the surface. Fairly obviously, this will require more experimentation than I’ve done so far.

Minimal assist air protects the laser focus lens from the debris and plenty of ventilation air carries the abrasive result out of the cabinet.

Not something I foresee doing a lot of, but at least I know what happens.

2022-06-02
Laser Imaging: Paving Tile vs. Titanium Dioxide

Dump enough titanium dioxide powder into denatured alcohol to make a thin slurry, bloosh it onto a reasonably clean paving / floor / whatever tile, spread it out with a chip brush, let the alcohol evaporate, then try a few images with various laser power settings scanned at 400 mm/s:

Paving tile – TiO2 prep and engrave

Wash off the TiO₂ powder to leave the fused titanium behind:

Paving tile – TiO2 images

A closer look at the middle eye:

Paving tile – TiO2 images – detail

The small granules spread across the surface are glass chips that probably improve traction, so this must have been a paving or floor tile intended for wet areas. A small stack of whole tiles and fragments Came With The House™, they’ve come in handy over the years, and that’s all we know.

The darkest image was at 40% power (maybe 24 W) and the lightest at 15%, although my notes are a bit fuzzy, and it started as a grayscale image dithered into on/off dots.

Obviously, my imaging hand is weak, but it does verify that TiO₂ powder will produce some sort of image without all the bother and solvents associated with paints / primers and the removal thereof.

2022-06-01