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 Cutter vs. Mirrorshades: Rear
Continuing with the same battered sunglass lens:

Laser vs sunglasses – beam front overview

It’s now oriented with the back side of the lens toward the unfocused beam going into the laser head.

The front surface remains undamaged after two pulses at 500 ms 50% power:

Laser vs sunglasses – beam rear – front overview

The red disk in the middle of both wounds is new this time.

As seen from the rear, the first pulse shattered the rear glass layer:

Laser vs sunglasses – beam rear – A

The image is about 7 mm from side to side.

A chip of glass popped out of the upper part of the fracture, but the other pieces remained in place.

The distinct blue ring is 3 mm OD and marks the inner boundary of a purple disk surrounding the central burn. The disk appears only in reflected light (which is impossible to photograph with any setup I can manage), suggesting it comes from diffraction in a surprisingly uniform air layer blown between the glass and the plastic polarizing sheet.

Also seen from the rear, the second pulse produced a neater wound:

Laser vs sunglasses – beam rear – B

The blue ring is again 3 mm OD and the image is 7 mm across.

The central red spot probably comes from damage to the polarizing sheet.

The most surprising things, at least to me, didn’t happen:
- the glass lens didn’t disintegrate
- the laser beam didn’t punch completely through
Protip: Don’t depend on ordinary glasses, even fancy sunglasses, to protect your eyes from CO₂ laser beams.
2022-12-16
Laser Cutter vs. Mirrorshades: Front

Well, a shattered lens found beside the road on a walk:

Laser vs sunglasses – focused overview

The battered frame has enough information to suggest they were once rather fancy. At this point, all that matters is they have two glass layers separated by a dark plastic polarizing film, with a gold-ish metallized front glass surface.

I fired the two pulses (on the left side of the obvious crack) at the front of the lens, both at 100 ms / 70% power:

Laser vs sunglasses – overview

Neither pulse penetrated the lens.

The smaller zit was fired in the position shown in the first picture, with the focal point more-or-less at the top surface of the lens. As seen from the front:

Laser vs sunglasses – focused front

The outer part of the damaged area is about 0.5 mm in diameter. The heat around the damage seems to have cleared away all the schmutz on the lens; those things that look like scratches are oily smears and road dirt.

Seen from the rear:

Laser vs sunglasses – focused rear

The rear surface is blistered, but doesn’t have a hole, so I think the beam melted the glass and inflated a cavity along its path.

I then perched the lens in the unfocused beam path, with paper taped over the laser head opening to keep any fragments off the mirror and focus lens:

Laser vs sunglasses – beam front overview

The beam produced the larger scar and also blasted off a ring of crud around the wound, as seen from the front surface:

Laser vs sunglasses – beam front

The beam seems to have shattered a thin layer under the metallization, but didn’t do any deeper damage. The rear surface is undamaged and the paper didn’t have a scorch mark.

They’re not laser safety glasses, but at least they didn’t disintegrate.

Protip: do not lie on the laser platform and stare upward into the laser head, even while wearing fancy polarized mirrorshades.

2022-12-15
Bed Frame Feet

Quite some time ago I slipped felt pads under the feet holding the bed frame off the wood floor and recently noticed two of them perpetrating an escape. My first thought was a variation of the 3D printed Fuzzy Felt Feet holders under our power chairs, but the bed frame feet are much larger.

The holders are basically rings surrounding the feet and felt, which LightBurn makes easy enough:

Bed Frame Feet – LB layout

The Foot Retainer is 6 mm plywood, the Plate and Felt Retainer are 3 mm.

I fired a ranging shot to verify the sizes:

Bed Feet – clamping

Then do three more, apply wood glue, and deploy Too Many Clamps.

The fuzzy felt feet are about 5 mm thick, so the 3 mm plywood shouldn’t quite touch the floor. Alas, the fuzz squishes more than I expected, so I added the chipboard Felt Spacers for a millimeter more clearance:

Bed Feet – chipboard spacer

They’re glued to the Plate with the felt adhesive side stuck to them:

Bed Feet – fuzzy felt foot

The felt and chipboard compress under load so now it behaves as it should:

Bed Feet – installed

Gotta get better at gluing plywood together, though.

2022-12-14
Laser Cutter: Fire Extinguisher Brackets
A Genuine Kidde Fyre Freez CO₂ extinguisher that Came With The House™ finally found its ideal location:

Fyre Freez extinguisher – mounted

It was last refilled 65 years ago:

Fire Extinguisher Recharge Tag – 1957

I know it’s still good, because the label has its 4 lb 7 oz refilled gross weight stamped into it, which is exactly what it weighs today.

Walter Smith Welding Supplies may still be in business, perhaps in Poughkeepsie, but their former 18 Downs St location in Kingston has become Noble Gas Solutions:

Noble Gas Solutions – 18 Downs St Kingston – 2019

Back then, you could call Smith Welding at a four digit phone number in Kingston: 5061. Nowadays, you must call Noble Gas with three more digits: 338-5061. As Charles Stross observed, something like 70% of the future is already in place, because infrastructure is so tenacious.

Heck, just look at that Quonset hut!

Keep calm and extinguish on:

Fyre Freez extinguisher – step 4

Two thoughts spring to mind:
- Most kitchen fires start waist-high (it’s the late 1950s: where else would she be?)
- She’s gonna lose skin on that metal tank
Seems to me a Fyre Freez will get cold enough to freeze skin while discharging, but I admit to not having actually tried it.

Anyhow, given the overall basement decor, the brackets have the right general style:

Fyre Freez extinguisher – bracket detail

Here’s hoping its future will be as dull as its past …
2022-12-13
Encounter With A Cash-for-House Scammer

This conversation started during the few hours when I had to turn off my phone’s incoming-call whitelist filter:

Cash Home Sale SMS

Seems to me a cash-for-house buyer who believes anything the seller says about the property is both new to the “real estate” biz and not destined for a long career. Obviously, the whole exchange attempts to increase my engagement and make me agree with everything going on.

Now, should you happen to be moving to the Mid-Hudson Valley and need a really nice shop with an attached house, let me know: we can work out a better deal.

Protip: if you’re in a position to stack seven thousand Benjamins on our kitchen table, don’t get between us and and the horizon.

There is a reason all my calls and texts go through a whitelist filter.

2022-12-12
Drug Fact Sheet: Overdose

For reasons not relevant here, a new medication has entered the house, accompanied by its Drug Fact Sheet (blurred because you do not have a Need To Know):

Drug Fact Sheet

The background squares are a scant one foot across.

The other side of the sheet is equally dense.

One should review this with each refill to check for new or changed information. Of course, there are no change bars or similar hints.

It might kill ya or cure ya, but you’ll never figure it out from that torrent of verbiage: just like software EULAs, nobody can possibly read and comprehend that stuff.

2022-12-09
Sears / Kenmore Progressive Vacuum Cleaner: Motor FAIL

After seven years, our Sears / Kenmore Progressive vacuum cleaner gave off a horrible screech and an intense smell of electrical death, prompting me to tear it apart.

It’s easy to find the two front screws holding the top in place, although you’ll need either a bendy or offset screwdriver to remove them:

Sears Progressive Vacuum – front case screws

Pull up hard on the cord retraction plunger to remove it, revealing the two rear screws:

Sears Progressive Vacuum – rear case screws

Extract the wires and motor control PCB from their niches:

Sears Progressive Vacuum – motor assembly overview

Prying the latch in the middle of the rear panel (over on the right) releases the motor assembly, which you can then wiggle-n-jiggle upward and out:

Sears Progressive Vacuum – extracting motor assembly

Disconnect the wires, peel off various foam bits, and extract the motor from its carapace. Measure the blower diameter and cut a suitable plywood clamp for the bench vise:

Sears Progressive Vacuum – custom motor clamp

I loves me some good laser cutter action, even when the plywood crate the laser came in doesn’t have much to recommend it:

Sears Progressive Vacuum – failed plywood clamp

I vaguely recall reading the purple tinge comes from the bromine vapor used to dis-insect the wood during manufacturing, before shipping it halfway around the planet.

One area of the commutator looks like it’s in bad shape:

Sears Progressive Vacuum – as-found commutator

Clean the commutator bars in the desperate hope it’s just random crud, even though that seems unlikely, then connect a widowmaker cord to the motor terminals:

Sears Progressive Vacuum – widowmaker line cord

Use a Variac to spin the motor at a (relatively) low speed while watching the brushes and commutator:

Sears Progressive Vacuum – commutator sparking

Now, that is not a nominal outcome.

The cleaned commutator again shows signs of distress:

Sears Progressive Vacuum – scarred commutator

Indeed, measuring the resistance across the line cord terminals shows a shorted winding: 0.0 Ω with the brushes aligned on the bars just antispinward of the scars.

So the motor is definitely, irretrievably dead.

Extracting the brushes shows the arcs have eroded their spinward edges:

Sears Progressive Vacuum – eroded motor brushes

The dark smudge on the windings seems due to internal problems, rather than just the arcs, because the wiring crossing between the commutator and the smudge remains clean:

Sears Progressive Vacuum – charred motor windings

One can buy a used motor assembly on eBay for about $40, with no assurance it doesn’t also have a shorted winding.

Dang, now I gotta make more adapters for whatever vacuum comes next …

2022-12-08