Ed Nisley's Blog: Shop notes, electronics, firmware, machinery, 3D printing, laser cuttery, and curiosities. Contents: 100% human thinking, 0% AI slop.
Category: Science
If you measure something often enough, it becomes science
Earlier this year, a pair of House Finches chose the a pine cone wreath hanging outside our front door for their nest.
One day a Starling attacked:
Starling Attack – IM_00052
Starling Attack – IM_00053
Starling Attack – IM_00054
There’s a Youtube video of the action following those pictures:
Ms. Finch suffered a peck to the head raising a few feathers into a small topknot, but seemed otherwise undamaged. The eggs survived unscathed and a month later they fledged a quartet of new finches:
House Finch chicks – pre-fledging – 2024-05-18
Yes, they’re surrounded by a ring of bird crap: finch chicks can aim and fire overboard, but they don’t have much range.
The same finch pair abandoned their second nest after a Brown-headed Cowbird added an egg and punctured both Finch eggs:
House Finch nest – Cowbird egg vs punctures
Their third attempt failed after four eggs when a Cowbird added a fifth:
House Finch nest – Cowbird egg with 4 finch eggs
A few days after that picture, something tore that nest apart and destroyed all the eggs:
House Finch nest – destruction with feathers
The scattered feathers suggest a major battle with severe injuries.
Three nesting attempts produced only four fledglings: a bad year for those two finches.
Morning KP provides considerable time to watch the goings-on in the back yard, including the wide variety of pollinators (formerly known as “bees”) in the stand of daisies just off the deck:
Daisy thumbnail – 348
I wondered if the flower heads tracked the sun or just sort of stood there, so I deployed the trail camera to take one picture every five minutes for a bit over 24 hours. Converting just under 500 images into a movie required this incantation:
The short answer: daisies don’t really track the sun, but they move more than I expected. The stalks carrying unopened flowers writhe all around, occasionally getting stuck on other stems and suddenly snapping free. I was particularly surprised at the number of bees going about their business just around midnight.
Which turned out to be entirely too stiff, which wasn’t surprising given that Trolase Thin is intended for signage stuck on flat or slightly curved surfaces.
Despite being “paper”, laser testing paper is also too stiff:
Laser test paper – outdoor labels – 2024-06-22
The wrinkles and cracks on the left end of the tags shows the plastic coating makes it basically impossible to shape / bend the paper enough to wrap around a plant stem, then push it through the hole (offscreen to the left). I was not surprised too much by this discovery.
Those two strips now hang outside the kitchen window (left end upward), where they’ll get enough sun and rain to keep a plant happy, and I’ll see how well the engraved / damaged plastic coating stands up to that sort of abuse.
The mounting block under the electronics box for the new UPP battery has a recess for an M5 tee nut:
UPP Battery Mount – Block 5 Show View
As with the Terry frame mounts, I glued the modified tee nut in place with JB Plastic Bonder urethane adhesive, did a test fit on the bike, discovered the whole affair had to sit about 10 mm forward, put the new frame measurement into the OpenSCAD code, and ran off a new block.
Which gave me the opportunity to perch the old block atop the bench vise with the tee nut aimed downward between the open jaws, run an M5 bolt into the nut, and give it a good thwack with a hammer:
UPP Battery Mount – M5 insert adhesive test
Although the urethane adhesive didn’t bond uniformly across the tee nut, it had enough grip to tear the PETG layers apart and pull chunks out of the block.
As with the tee nuts on the Terry bike, this one will be loaded to pull into the block, so it will never endure any force tending to pull things apart, but it’s nice to know how well JB Plastic Bonder works.
I chiseled the PETG and adhesive debris off the tee nut, cleaned it up, slathered more Bonder on the new block, and squished the nut in place. After I get the electronics box sorted out, the whole affair will never come apart again!
That’s the standard backlash test pattern shrunken down to a little over an inch wide, with the laser power reduced to the bare minimum. Despite that, the numerous holes show where the pattern concentrates enough energy to vaporize the paper.
The “paper” seems to be laminated between two black plastic sheets that smell terrible when engraved, so they’re probably some form of acrylic. The Amazon product description is, despite all the verbiage- remarkably uncommunicative of the actual materials involved.
The circular pattern is 10 mm diameter on the outside:
Laser test paper – miniature pattern detail
Those should be circles around the perimeter, but their distortion shows what happens when you try to move a hulking CO₂ laser head around a 1.5 mm diameter circle at 400 mm/s. Of course, the actual speed is nowhere near that fast along such tiny vectors.
The traces are about 0.2 mm wide, with obvious scorches where the beam starts and stops, which agrees reasonably well with previousmeasurements.
All in all, both the paper and the laser pattern look better than I expected, particularly as the results indicate the machine has no measurable backlash at all.
The intended cuts are the dark lines, each with a poorly defined scorch 2 mm on its left. Knowing that the nozzle is about 4 mm, this suggests the beam is off-center enough to juuuust kiss the nozzle and splash the outer part of the beam away.
Having recently spot-checked the alignment and not seen any odd behavior on another platform-spanning project, this was puzzling. Given that the laser recently survived a move from one Basement Shop to another, with plenty of jostling while standing on end, I suppose I should have been more careful.
The biggest clue was seeing the shadow lines only near the front-right corner and noting they got worse farther into the corner. This seemed like the “fourth-corner” alignment problem described by St. Sadler some years ago and covered in a more succinct recent video.
AFAICT, the problem boils down to the difficulty of precisely aligning the beam at the longest distance it travels in the front-right corner. Careful adjustment of Mirror 1, after getting everything else lined up properly, seems to be solution.
The beam is slightly off-center at Mirror 1 and only a millimeter high on Mirror 2 at either end of the gantry travel along the Y axis.
The beam position at the laser head entry upstream of Mirror 3 shows the problem:
Beam Alignment – Initial M3 entry – 2024-05-31
The targets are left- and right-rear, left- and right-front, with varying pulse lengths obviously underpowering the last and most distant shot.
Looks like a classic fourth-corner problem!
Tweaking Mirror 1 by about 1/8 turn of the adjusting screw to angle the beam vertically upward eventually put the beam dead-center at Mirror 3:
Beam Alignment – M3 adjustments – 2024-05-31
The bottom two targets are double pulses at the left- & right-rear and ‑front, so the beam is now well-centered.
A quick cross-check shows the beam remains centered on Mirror 2 at the front- and rear-end of the gantry travel, Mirror 3 is still OK, and the beam comes out of the center of the nozzle aperture:
Beam Alignment – M2 M3 exit final – 2024-05-31
Subsequent cutting proceeded perfectly all over the platform, so I think the alignment is now as good as it gets or, perhaps, as good as it needs to be.
The granular surface does not get along well with the 5× digital zoom required to fill the phone’s sensor, but you get the general idea:
Figaro TGS880 – element detail
The heater measured 30 Ω on the dot and the sensor was an open circuit on the 100 MΩ range. Connecting the heater to a 5 V supply dropped the sensor resistance to 800 kΩ @ 50 %RH and a warm breath punched it to about 2 MΩ. That’s with an ohmmeter because I haven’t yet unpacked the Electronics Bench, but seems far above the spec of 20-70 kΩ in air.
So it’s still a sensor, even if it’s not within spec.
The WordPress AI-generated image for this post is … SFnal:
Figaro TGS-880 Gas Sensor – AI generated image
My pictures apparently aren’t up to contemporary blog standards …
The Smell of Molten Projects in the Morning 