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.

Category: Machine Shop

Mechanical widgetry

Samsung Dishwasher: Upper Sprayer Disassembly

The Samsung dishwasher has an upper rack with a rotating sprayer that was thoroughly clogged with debris from its damaged screen filter:

Samsung dishwasher top nozzle – assembled

The whole assembly is readily available, although it seems any discrete part of the dishwasher costs about fifty bucks and this one wasn’t exactly broken.

It comes apart by rotating the lock ring (the one with right-angle ears sticking out on either side) 1/8 turn in the other direction from whichever way you think it should rotate. Hold the spray bar, shove the ears, and the spray arm will drop off:

Samsung dishwasher top nozzle – unlocked

The inside of the spray bar shows the locking details:

Samsung dishwasher top nozzle – sprayer

Now, here’s the tricky part.

The small ring under the locking ring, the one with two square nubbins pointing downward, snaps onto the pipe carrying the water. There’s a shallow notch around the pipe, the inside of the ring has a shallow lip, and the ring holds the whole affair onto the pipe.

Contrary to what I thought, the two nubbins do not latch onto anything. Apparently, they hold the ring in the proper position relative to the arm’s interior and that’s it.

The only way to reassemble the arm is to snap the small ring into place, with the lock ring above it, then install the arm and turn the lock ring 1/8 turn the other way. You (well, I) cannot snap the assembled arm into place, because the nubbins don’t provide enough oomph to seat the small ring on the pipe.

Unless I write that down, I will never remember it …

Protip: Needle nose tweezers are invaluable for picking crud out of the nozzles. Iterate on picking and flushing with water until nothing more comes out, then expect to repeat the process several times as more crud emerges from the depths of the plumbing.

Although it is apparently possible to disassemble the spray arm by unlatching all the snaps along the edge, I’d reserve that for a moment when lives depended on unclogging the nozzles.

2024-06-27
Laser Test Paper: Outdoor Testing

“Laser test paper” is, of course, intended for testing lasers, but I thought it might make a outdoor plant tag. A while ago I tried some Trolase Thins acrylic for that job:

Plant tags – Trolase Thin – prototypes

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.

For Science!

2024-06-26
Antique Desk Chair: Leg Rebuild

With the seat glued and the old caster sockets yanked, I carved a piece of plywood to fit the gap in one leg:

Wood desk chair – leg filler – bottom

After whittling the wood to kinda-sorta go in there, I pressed it against snippets of carbon paper (remember carbon paper?) to mark the contact points and carve them off:

Wood desk chair – leg filler – carbon paper fitting

This occupied most of a SquidWrench remote meeting, but eventually sank it flush with the leg:

Wood desk chair – leg filler – side

Now, that’s not the prettiest job you’ve ever seen, but it gets worse:

Wood desk chair – leg epoxy shaping

This time around, I tinted the epoxy with brown and black dye, which knocked the color back to something tolerable and increased the curing time well beyond the usual couple of hours. Fortunately, I wasn’t in a hurry and it was pretty much done by the next afternoon.

Whereupon I mixed up another bodacious batch of epoxy:

Wood desk chair – caster pin prep

The Kapton tape wrap kept (most of) the epoxy out of the end of the sockets. I buttered up the sockets just below their serrated heads and tapped them into the legs:

Wood desk chair – caster pin installed

Yeah, I wiped that down a little better before another overnight cure left the four pins firmly secured in their legs; the pins still rotate (albeit stiffly) in the sockets, although the casters really swivel on their pins.

A cast iron fitting of the kind they just don’t make any more holds the legs in place:

Wood desk chair – bottom plate

My screw collection lacks chonky wood screws, but I doubt anybody will ever notice that shiny crosspoint screw.

In any event, the plate holds the legs in tapered slots along the cast iron base that also guides the height adjusting leadscrew under the seat:

Wood desk chair – leg wedge shims

The wood dovetails in the legs were a bit worn / shrunken, so I shimmed them with two strips of 3.5 mil = 0.09 mm stainless steel tape on each side and tapped the legs into place with a plastic mallet. The steel is completely invisible from outside and the legs are magically solid, just like they should be.

As expected, the new casters clash horribly with the chair’s classic style:

Wood desk chair – repaired

Somewhat to my surprise, it’s now undergoing a field test at Mary’s desk, where it replaces a chair she never liked. The seat adjusts down enough to let her feet reach the floor (which most modern chairs do not) and the edge doesn’t press on the back of her legs. We fiddled with the backrest height / angle / tension and it feels surprisingly good.

You gotta admire something with that kind of durability and repairability.

A good refinishing job would definitely improve its appearance, but that’s well beyond my abilities.

2024-06-25
Samsung Dishwasher Screen Filter Fix

The Screen Filter (DD81-02011A) in our Samsung dishwasher (DW80K7050US) turned out to have a mold defect from the factory that’s been sitting there since the previous owners had it installed back in 2018:

Samsung dishwasher screen filter – gap

The mesh apparently didn’t quite make it into the molded plastic, so that little gap has been letting debris in the wash water circulate through the spray bars and clog the orifices.

While replacements are readily available, they seem rather pricey for what they are and this seemed like an easy repair:

Samsung dishwasher screen filter – glued

That’s a bead of EVA hot melt glue that will probably withstand the 163 °F = 73 °C “sanitize” cycle we haven’t had any occasion to use and seems no more toxic than anything else around here.

Protip: if your dishwasher has a filter, it’s likely clogged with a nasty accumulation of gunk, too …

2024-06-24
M5 Tee Nut: Test To Destruction

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!

2024-06-20
Antique Desk Chair Woodwork

A wood desk chair that I’ve known since I was a pup finally got some much-needed attention, although not a restoration. By and large, I’m finally sorting out that corner of the basement and needed to put the chair’s parts back together so I can work on something else.

The wood seat consists of several slabs glued along keyed joints, one of which had fractured into a rough mess. Amazingly, the two sides fit perfectly together, albeit with the bottom no longer a planar surface, and glued up just like they should:

Wood desk chair – seat clamping

The chair isn’t up to contemporary office standards, but it has a seat elevation screw, a backrest with adjustable angle & elevation, and even a backrest tension setting:

Wood desk chair – ironwork

It was the cutting edge of desk chair technology:

Wood desk chair – patented

I vaguely recall it rolled on long-vanished steel-wheeled casters. Somewhat less long ago, one of the legs broke enough to lose its caster socket (about which, more later), so I set about yanking the three remaining sockets:

Wood desk chair – caster socket removal

During that struggle, another leg revealed a neat woodwork joint:

Wood desk chair – leg joint

It’s easy to remove a caster socket when you can bash it from the top!

Gluing that piece back in place required Too Many Clamps™ aligning it with the leg:

Wood desk chair – leg clamping

But the end result looks pretty good:

Wood desk chair – leg glued

They did a nice job of matching the wood grain; I hadn’t noticed that joint while attacking the socket.

Pending restoring the broken leg’s socket, the soon-to-arrive new casters will clash horribly with the chair’s woodwork. At least it’ll roll again and its new plastic wheels won’t scar the floors.

2024-06-19
Laser-marked Hole Drilling Spots

While setting up to drill holes in the aluminum base for the running light buck converter, I wondered if laser-marking the spots directly from the solid model would work better than my usual fumbling around.

The solid model:

Running Light – power box – bottom view

Export projections of the pieces from OpenSCAD as an SVG file:

Running Light – power box – Projection view

Import into LightBurn, set up for a very fast, very light cut and Fire The Laser:

Laser-marked hole spots – masking tape

That’s in ordinary masking tape on a hard-anodized sheet of aluminum from the pile, which looked better than I expected.

The same aluminum covered with blue tape:

Laser-marked hole spots – blue tape – hard anodize

Which looks much better in person than it does in the photo.

On a soft aluminum sheet from the Basement Warehouse Zone:

Laser-marked hole spots – blue tape – sheet aluminum

The dark outline is a comfort mark hand-drawn around a chipboard test piece to verify the layout fit between random holes drilled in the sheet during its previous life.

A closer look at a corner hole:

Laser-marked hole spots – blue tape – hard anodize – detail 1

And the center hole:

Laser-marked hole spots – blue tape – hard anodize – detail 2

The holes appeared in the right places after center-punching by eye, but the fragility of those four little tape leaves around the center point must be experienced to be believed.

And, yes, those are deliberately low-polygon approximations to a circle, because I’m a low-poly kind of guy.

I really need an optical center punch if I do more such silliness. The box with those HP plotter digitizing sights recently came to hand, so I suppose I should make something.

2024-06-12