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: Laser Cutter

Laser-safe PSA “Vinyl”: Proof of Concept

Mary’s ResMed AirSense 11 saves the data from every overnight breath she takes on an SD card, which she uploads to OSCAR once a week. I figured she needed an SD card to USB adapter / card reader of her very own:

PU PSA Vinyl test – installed

The lurid green letters aren’t backlit, they’re cut from a PVC-free “vinyl” (really, polyurethane) sheet with adhesive on the back.

N.B.: Laser-cutting real vinyl, made from PVC, releases enough chlorine gas to corrode the guts of your machine and, with poor fume extraction, rot your lungs along with it.

The LightBurn layout is pretty much what you’d expect, with the letter inside the outline of the USB dingus on a tool layer to get the size right:

PU PSA Vinyl test – LB layout

The red layer is a “kiss cut” through the vinyl (remember: polyurethane) that leaves the backing paper mostly undamaged:

PU PSA Vinyl test – dot mode cut detail

The cut uses Dot Mode, with the laser firing at 10% power for 2 ms, spaced every 0.1 mm along the cut. I found 0.1 mm spacing produced a more-or-less continuous cut in the PETG sheet for the Tek Circuit Computer cursor hairline, but this picture shows it’s definitely running in pulsed mode. In any event, Dot Mode is the only way a 60 W CO₂ laser can make a kiss cut, as a normal vector cut can’t run fast enough to prevent cutting all the way through the backing paper, even at 10% power, around those letters.

The edges of the letters are slightly melted with a raised border, although they look pretty good if you’re not peering at them through a microscope.

I cut the rectangular outline with scissors, peeled the waste vinyl away, and weeded the ‘a’ with tweezers:

PU PSA Vinyl test – weeded

Stick a snippet of transfer tape on top:

PU PSA Vinyl test – transfer tape

In theory, the transfer tape sticks more firmly to the cut letters than the letters adhere to their backing paper, so peeling off the tape also peels the letters off the backing paper.

Which did not go well:

PU PSA Vinyl test – transfer tape – peeling

The two adhesions obviously require a delicate balance to work properly and I would be unsurprised to learn different transfer tapes behave differently on each type of vinyl sheet, with no way to know the results without trying every possible combination.

A few retries got the “r” back in position on the transfer tape, but a bit of kink remains in the “M”.

A third adhesion balance occurs between the transfer tape and the USB card reader, where the tape must stick to the letters slightly less than the letters stick to the reader. Burnishing the tape + letters to the reader encouraged the letters to stick and the tape pulled off without dislodging them.

We deemed the result good enough for the purpose and the process taught me a few lessons along the way. Next time, maybe it’ll work out better.

2023-03-14
Please Close The Gate Signs: MDF Weathering

With the new signs in place, the old ones paused briefly for a photo op on their way to the trash:

Please Close The Gate – weathered MDF

That’s eight months of weathering on MDF covered with indoor urethane sealant and it’s not as awful as I expected: the MDF didn’t actually disintegrate, it just collected some mold / mildew / crud.

A closer look:

Please Close The Gate – weathered MDF – detail

The black paint survived surprisingly well.

I hadn’t paid ~~much~~ any attention to the edges, so they got covered with random amounts of black paint and urethane. It seems that’s where the disintegration starts:

Please Close The Gate – weathered MDF – side view

MDF definitely isn’t the right material for an outdoor sign and I knew that going in, but it’s cheap and readily available, which makes up for a lot.

For comparison, they looked nice right after installation:

Please Close The Gate – fresh painted

Ya learn something new every year around here!

2023-03-09
Please Close The Gate Signs: Paint Masking FAIL
A warm day let me shoot the engraved signs for the Vassar Community Garden gates with rattlecan black:

Please Close The Gate – masking tape peeled

The full sheet of orange acrylic arrived with plastic protective film on both sides, which I planned to use for paint masking. Alas, one side also had a wrinkle running its length that ended up on two signs, so I replaced that film with blue masking tape.

As fate would have it, the first side of the first sign I peeled had masking tape and produced what you see above.

Things went bad in a hurry. The paint had no adhesion whatsoever to the plastic film and fell off in flakes as I peeled the film away:

Please Close The Gate – plastic peeled

I assumed the flakes would just fall off the signs, perhaps with a little persuasion, so I peeled and weeded all the signs before cleaning them up.

Although the paint was fully dry, when the molecularly smooth surface of each paint flake touched the molecularly smooth surface of the newly exposed acrylic, the two instantly and permanently fused together.

There were a lot of flakes:

Please Close The Gate – plastic peeled – detail

Removal techniques that did not work:
- Vacuuming with a brush
- Gentle rubbing with a soft cloth
- Firm rubbing after spraying with acrylic cleaner
- Scraping with a plastic razor blade
So I deployed a P220 grit sanding block and wrecked the glossy surface of both sides of all six signs. I briefly considered trying to recover the finish by sanding them all up through about 2000 grit, then came to my senses: my sanding arm is weak.

Careful examination of the last picture shows several places around edges of the circle where the plastic film melted into a blob that blocked the paint, rather than vaporizing. I used enough power to engrave only about 0.3 mm deep (because they’re engraved on both sides), but the transition wasn’t fast enough for a clean edge.

They don’t look as nice as I’d like, but they’re good enough for the purpose:

Please Close The Gate – installed

The acrylic sheet is more see-through than I expected, at least when backlit by bright sunlight.

Please Close The Gate – seethrough

Next: we discover what happens to UV-stabilized orange acrylic and black outdoor paint over the course of a year in garden sunshine.
2023-03-08
Refresh Tears Eye Lube Storage Boxes

A recent Squidwrench meeting provided the opportunity to make a couple of racks for an assortment of Refresh Tears / Liquigel bottles:

Refresh eye lube – storage cases

I used chipboard to find out if the cross plates would stiffen the floppy 1.1 mm sheets enough for this light duty. Indeed, the overall structure becomes a nice rigid box, even though the feet and corners can’t withstand much abuse.

The finger joints use the default settings, which produce a lot of fingers along the edges. This turns out to be a Good Thing, as it gave the yellow wood glue plenty of opportunities to bond the sheets together.

Combining the default 5° slope with nine bottles along each level wastes a tremendous amount of vertical space. The adjacent racks hold three much larger cans per level, so roughly the same space doesn’t look like much. In retrospect, a 3° slope should work for smaller bottles.

And, yes, the squash on the lower shelf store nicely and become yummy meals all winter long.

The overstuffed URL generating the patterns:

http://festi.info/boxes.py/CanStorage?FingerJoint_angle=90.0&FingerJoint_style=rectangular&FingerJoint_surroundingspaces=0.0&FingerJoint_bottom_lip=0.0&FingerJoint_edge_width=1.0&FingerJoint_extra_length=0.0&FingerJoint_finger=2.0&FingerJoint_play=0.0&FingerJoint_space=2.0&FingerJoint_width=1.0&Stackable_angle=60&Stackable_bottom_stabilizers=0.0&Stackable_height=2.0&Stackable_holedistance=1.0&Stackable_width=4.0&fillHoles_bar_length=50&fillHoles_fill_pattern=no+fill&fillHoles_hole_max_radius=3.0&fillHoles_hole_min_radius=0.5&fillHoles_hole_style=round&fillHoles_max_random=1000&fillHoles_space_between_holes=4.0&fillHoles_space_to_border=4.0&top_edge=%C5%A0&bottom_edge=%C5%A1&canDiameter=30&canHeight=75&canNum=18&chuteAngle=5.0&thickness=1.15&format=lbrn2&tabs=0.0&qr_code=0&debug=0&labels=0&reference=0&inner_corners=corner&burn=0.04&language=en

And the eyeburning QR code:

Refresh Eye Lube – chipboard QR code

2023-03-02
Bobbin Storage Trays

Long ago, I gave Mary a box of 100 empty bobbins for her Kenmore 158 sewing machine, with the intent she would never again have to unwind a bobbin to put new thread on it. This worked so well I did the same thing for her Juki, with the result she needed somewhere to store all those filled bobbins.

Her work table has a shallow drawer, so we tried this out:

Bobbin Storage Case – installed

They’re a matched set cut from 1.5 mm TroCraft Eco:

Bobbin Storage Case – cutting overview

Watching all those little rectangles fall out just never gets old:

Bobbin Storage Case – cutting detail

I ran off a test tray in ordinary chipboard that works just as well, but lacks the pleasant appearance and feel of the TroCraft. Clear 1.5 mm acrylic would probably work, at the cost of requring a much neater glue job where the dividers meet the walls.

The spacing is a bit tight to pluck a bobbin from its slot between two others, but now she has enough space to arrange them as needed, with empty spaces around the most-used colors. I offered to carpet the drawer with bobbin trays, but she suggested waiting until these fill up.

The well-stuffed URL specifying the tray:

http://festi.info/boxes.py/TypeTray?FingerJoint_angle=90.0&FingerJoint_style=rectangular&FingerJoint_surroundingspaces=0.5&FingerJoint_bottom_lip=0.0&FingerJoint_edge_width=1.0&FingerJoint_extra_length=0.0&FingerJoint_finger=2.0&FingerJoint_play=0.0&FingerJoint_space=2.0&FingerJoint_width=1.0&Stackable_angle=60&Stackable_bottom_stabilizers=0.0&Stackable_height=2.0&Stackable_holedistance=2.0&Stackable_width=4.0&Hinge_grip_percentage=0&Hinge_outset=0&Hinge_pinwidth=0.5&Hinge_style=outset&Hinge_axle=2.0&Hinge_grip_length=0&Hinge_hingestrength=1&CabinetHinge_bore=3.2&CabinetHinge_eyes_per_hinge=5&CabinetHinge_hinges=2&CabinetHinge_style=inside&CabinetHinge_eye=1.5&CabinetHinge_play=0.05&CabinetHinge_spacing=2.0&Lid_angle=90.0&Lid_hole_width=0&Lid_second_pin=0&Lid_second_pin=1&Lid_spring=both&Lid_style=rectangular&Lid_surroundingspaces=2.0&Lid_bottom_lip=0.0&Lid_edge_width=1.0&Lid_extra_length=0.0&Lid_finger=3.0&Lid_play=0.05&Lid_space=2.0&Lid_width=1.0&Click_angle=5.0&Click_bottom_radius=0.1&Click_depth=3.0&RoundedTriangleEdge_height=50.0&RoundedTriangleEdge_r_hole=2.0&RoundedTriangleEdge_radius=30.0&RoundedTriangleEdge_outset=1.0&Mounting_d_head=6.5&Mounting_d_shaft=3.0&Mounting_margin=0.125&Mounting_num=2&Mounting_side=back&Mounting_style=straight+edge%2C+within&HandleEdge_height=20.0&HandleEdge_hole_height=75.0&HandleEdge_hole_width=40%3A40&HandleEdge_on_sides=0&HandleEdge_on_sides=1&HandleEdge_radius=10.0&HandleEdge_outset=1.0&sx=21*7&sy=12*7&h=20.0&hi=10.0&outside=0&bottom_edge=s&top_edge=S&back_height=0.0&radius=0.0&gripheight=30&gripwidth=00&handle=0&thickness=1.65&format=lbrn2&tabs=0&debug=0&labels=0&reference=00&inner_corners=corner&burn=0.04

Which can now be specified as the biggest QR code I’ve ever seen:

Bobbin Tray – TroCraft Eco QR code

That makes my eyes hurt …

2023-03-01
Laser-Cut Envelope Opener

As practice in using the laser to engrave a figure to a known depth, this seemed appropriate:

Envelope Opener – original

The black envelope opener on the right came in a long-ago surplus deal and worked really well, which I cannot say for the retail replacements I got a few years back.

The tan envelope opener on the left is an obvious case of IP theft, copying the size and shape using a scanned image:

Classic opener – knife blades – scan

The two blades seemed like good candidates, with the lower one winning the contest:

Kobalt 78010 Mini Utility Knife Blade mask

Although the pack of “mini utility knife blades” sports a Lowe’s Kobalt part number, they no longer carry that item. You can find plenty of identical blades elsewhere, so they’re not a rare collectible and I have plenty of backup.

Put the outline of the opener on a cut layer, put the blade on an engraving layer, orient appropriately, and make a mirror-image duplicate:

Envelope Opener – LB Layout

The original opener is a touch over 3 mm thick, so the settings engrave 0.25 mm into the surface to make a blade pocket, then cut the shapes from 1.5 mm TroCraft Eco:

Envelope Opener – cutting

After all the cutting was done, it looks about as you’d expect:

Envelope Opener – interior layout

Slather with yellow PVA wood glue and apply too many clamps:

Envelope Opener – clamping

Next time around, I’ll round off the edges before assembly, but that’s in the nature of fine tuning:

Envelope Opener – detail

The TroCraft sheet engraves so cleanly that, were I to go into mass production, I’d set up a fixture for grayscale engraving shaping the perimeters.

Obviously, this makes no economic sense, but it does produce a considerable amount of satisfaction, which is pretty much all that matters for such things.

2023-02-27
OMTech 60 W Laser Power Supplies
A LightBurn forum discussion about laser power supplies prompted me to finally organize my pictures.

Without looking at the captions, match each of the following pictures with its description:
- a failed ZYE MYJG60W-Y-1 (came with OMTech laser)
- an unbranded MYJG60W replacement from OMTech
- a Cloudray M60 (bought as a backup)
HV Power Supply – ZYE MYJG60W-Y-1 – failed

HV Power Supply – unbranded MYJG60W

HV Power Supply – Cloudray M60

That was easy, wasn’t it?

As I said in the forum:

My guess is there’s only one ZYE factory (or a dozen clones) producing all the power supplies, then applying whatever sticker the order calls for on the case before dropping it in the carton.

Perhaps Cloudray buys more quality control than the anonymous “brands”, but I wouldn’t lay much money on finding more than two QC bins at the end of the assembly line: either it runs or it doesn’t.
2023-02-23