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: Rants

And kvetching, too

Laser Cutter: Fourth Corner Fix Summary
A discussion on the LightBurn forum about a large-format machine with a misaligned beam prompted me to think through the whole “Fourth Corner” problem and come up with this summary based on my beam realignment adventure:
Here’s what I think is going on, referring to the 4×8 foot (!) machine in that discussion and lightly edited to improve readability & fix minor errors …

Mirror 1 alignment gets the beam parallel to the Y axis, averaged over the gantry travel between front and rear. The path length variation on your machine is four feet.

Mirror 2 alignment gets the beam parallel to the X axis, averaged over the laser head travel from left to right. The path length variation on your machine is eight feet.

When the laser head is in the left rear corner, the total path length is maybe a foot or two. When it’s in the front right corner, the total path length is upwards of twelve feet.

The “Fourth Corner” problem comes from a slight angular misalignment of Mirror 1, because you (and I and everybody) must set it with a maximum path length around four feet (Mirror 1 to Mirror 2 with the gantry at the front end of the machine). But with the laser head in the right front corner, the path length (Mirror 1 to Mirror 3) is three times longer, so the error due to a slightly mis-set angle at Mirror 1 is correspondingly larger.

A tiny tweak to Mirror 1 changes the spot position at Mirror 2 by very little, but moves the spot at Mirror 3 by much more due to the longer path length.

Tweaking Mirror 1 cannot compensate for a warped machine frame, but it will get the beam alignment as good as it can be made.

The next point of contention was my “middle of the mirror” suggestion. AFAICT, the spot burned into the target at each mirror marks only the useful part of the beam with stray energy in a halo around it. Centering the spot keeps that stray energy away from the mirror mounts, so it doesn’t cause unnecessary heating. This will be particularly important with a high-power laser.

Angular adjustment of each mirror puts the beam parallel to the axes, but cannot also center it on the mirrors. After it’s aligned, the path from the laser tube through the nozzle depends on the position of the tube relative to the nozzle: moving the tube up/down and front/back moves the beam position on the mirrors and through the nozzle, but (in an ideal world) doesn’t change the angular alignment.

So after aligning the beam parallel to the axes, you must move the laser tube, the mirrors (up/down left/right front/back), and maybe the laser head to center the beam in the mirrors and also in the nozzle. Because we don’t live in an ideal world, moving any of those pieces wrecks their angular alignment, so it’s an iterative process.

The goal is to reach this point:

Beam Alignment – Mirror 3 detail – 2023-09-16

Those are five separate pulses, one each at the four corners and center of the platform.

The beam then goes pretty much through the center of the laser head and lens:

Beam Alignment – Focus detail – 2023-09-16

Works for me, anyhow.
2024-11-13
Road Construction: Continual Damage

Having watched a tour bus jounce over the poor suffering street lamp base, I can easily understand how something similarly large killed the street signs:

Street Lamp Base – Overview

The black ring in the upper left formerly positioned a barrel over the lamp base:

Street Lamp Base – barrel ring

Something heavy shaved down those bolts:

Street Lamp Base – detail

The blue-and-white pull cord seems at risk of vanishing.

They’re now laying asphalt and the project continues apace.

2024-11-05
Road Construction: Collateral Damage

NYS DOT installed rows of street lamp foundations along both sides of Rt 376 as part of the intersection reconstruction that will eventually put a fourth traffic circle along Raymond Avenue. Until the intersection of Rombout House Lane with Rt 376 vanishes, this lamp base at the corner sits well within the turning radius of the heavy trucks entering & exiting the contractor’s material dump & equipment marshalling yard:

Street Lamp Base – A

The fluorescent paint appeared after something heavy ran over the base and bent two of the bolts that should secure the lamp post.

A few days and a few more passes killed those bolts dead:

Street Lamp Base – A – more destruction

The barrier barrel in the background sat atop the base for a few days, but obviously didn’t affect the outcome.

A few hundred feet south, a heavy metallic mass sheared off another pair of bolts and bent the survivors:

Street Lamp Base – B

Someone eventually moved the sheared bolt atop the base, so perhaps the damage has been noted where that note will have some effect.

The “bolts” are the threaded end of long rods embedded in the three or four feet of pre-cast concrete forming the lamp base. The concave concrete mass to the right in the first picture is residue from the poured concrete in the hole anchoring the base to the ground.

A four foot deep trench along the row of lamps holds electrical conduit between them for the wiring that will eventually surface through the conduit covered by the duct tape. The white-and-blue cord hauls the pull tape from one base to the next to pull the conductors through the conduit.

Replacing those cast-in-place bases won’t be a trivial (pronounced “inexpensive”) operation and I suspect a powerful motivation to just un-bend the wounded bolts and pretend they’re not severely weakened. I doubt a base with just two bolts will pass final inspection, but maybe the inspector won’t look inside the lamp pole covers.

Nah, that sort of thing never happens …

2024-10-10
Water Shutoff Valves: Autopsy

After a bit more than half a century, the rubber washer in the cold water shutoff valve for the kitchen sink had fossilized:

Sink shutoff – cold washer

The hot water washer was in much worse condition:

Sink shutoff – hot washer

The shutoff valve for the hose bib in the front of the house, mounted knob-downward, has been dripping quietly for many many years before I replaced it:

Hose valve shutoff – knob corrosion

I’d turned the valve off to no avail, so this was no surprise:

Hose valve shutoff – washer

While it is theoretically possible to replace those washers, even the professionals know better than to disturb a sleeping valve:

Dishwasher valve doubling

The tandem valve was likely installed half a decade ago, along with the dishwasher it services. Perhaps the washer inside remains soft.

2024-08-23
As If Your Life Depended On It

Spotted on a scissors lift outside a grocery store being remodeled:

Skyjack scissors lift warning labels

The SkyJack instruction manual explains the symbols, although some of the Quick Start instructions remain baffling.

We had great fun making up captions to suit the pictures …

2024-08-20
Bathroom Faucets: User Interface FAIL

The sink faucet in our motel room worked the way you’d expect:

Grohe sink faucet

It pivots left-right to adjust the temperature and lifts to control the flow, which is Off when the handle is parallel to the sink countertop.

Evidently, everybody assumes that’s the way the identical faucet handle works in the shower, despite the helpful label:

Grohe shower faucet

Did you notice the minuscule red dot below-and-left of the handle or the corresponding blue dot just to its right? Absent the label, those provide all the hints you’ll get as to how the handle operates.

The faucet body & plumbing were loose in the wall, as though many previous people had given it a firm yank to get water out of it.

I’m 3.5 diopters nearsighted and can’t see those little dots. Mary is 2 diopters farsighted and can’t see the label or the dots.

What did they think would happen with different valves having identical affordance?

2024-08-19
Home Depot Glacier Bay Kitchen Faucet: Round 2

The kitchen faucet worked its way loose again. Attempting to shut off the water revealed a pair of leaky valves under the sink, so I shut off the house water in the basement, cut the valve pipes below the solder drips, and installed a pair of push-connect shutoffs:

Kitchen faucet shutoff valve – push connection

I loves me some good push-connect fitting action, which is new news to me. Back in the Bad Old Days™, I’d be under the sink with a propane torch, trying to solder a pair of wet pipes and failing miserably.

With that out of the way and the faucet dismantled for the first time (by my hands, anyway), the threads holding the base to the spout column may have been damaged during factory assembly:

HD Glacier Bay kitchen faucet – damaged threads

I thought the gunk was thread lock compound, but it’s shredded plastic from the base fitting threads. The corresponding female threads inside the spout column are undamaged, so I think somebody tried screwing it together with the threads misaligned, backed off, then muscled it together.

It’s worth noting there are no keys or stops fixing the correct orientation of any of these parts. In particular, the trim ring bearing the small Front label (facing you in the picture) has no fixed orientation: whoever assembles the faucet in the factory must position it correctly on the fly as the base screws into the column and jams tight.

So I cleaned up the damaged threads as best I could, flipped the threaded brass tube end-for-end to put the cleanest part into the base, and reassembled everything with careful attention to starting the threads correctly:

HD Glacier Bay kitchen faucet – flipped brass tube

Tightening the base fitting into the column is much easier with everything on the kitchen counter, although centering the label on the molded opening required several tries.

Protip: a pair of grippy gloves and rubber sheets help a lot.

I want to find out how secure the original design, properly tightened and aligned, will be, so I did not apply any threadlocker.

2024-08-16