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

Makergear M2 Platform Flatness Puzzle

The first layer of a short TPU chain (about which, more later) came out vanishingly thin in the middle and much too thick on the ends:

Makergear M2 – TPU first layer

So: let the platform cool, scrape off the wreckage, set the nozzle for Z=2.0 mm, and measure the actual gap at various spots across the platform.

Those results are the top set of measurements:

Makergear M2 – BuildTak flatness check

The bottom set of measurements came from a similar test a few days later, after pulling the BuildTak plate off, doing nothing other than scrutinizing it, reinstalling it, and successfully printing several TPU chains of varying design, none of which had any first-layer problems. The platform is slightly too high along the +Y and -Y edges (rear and front), with no bow worth mentioning.

My measurements are, perforce, done with a cold platform, for obvious reasons, and the TPU prints at 50 °C. I have the uneasy feeling the heater / BuildTak magnetic base can bow upward in the middle while it heats, then flatten out after a while at a stable temperature. The good news: it’s not permanently bent.

More study is needed, including thinwall boxes after letting the platform soak at 50 °C for varying times.

2026-05-19
Prusa MK4 Camera Mount

Combining the Articulating Raspberry Pi Camera Mount with the Standardized Links and a few more bits & pieces from Printables made this happen:

Prusa MK4 – RPi camera installed

The camera will benefit from better lighting, but it has a great view of the proceedings and gets the job done:

RPi Camera Mount – image

The Standardized Link holes clear an M6 bolt, but the Thumb Remix models use M5×25 hex-head screws (the doc says M4) and they work fine. I printed the (turn-able) bolt knobs in blue PETG-CF to distinguish them from the (fixed) nut knobs, which really don’t need knurling.

The camera ball mount has a threaded socket for the original plastic screws, but the stem isn’t quite thick enough for an M5 insert. Heat-setting an M4 brass insert into the hole and epoxying an M4×25 hex-head screw into one of the Remix knobs worked fine.

One Snap Fit Cable Management Clip holds the ribbon cable to a link. I think the RPi can fit under the platform inside the MK4 frame, with another clip or two routing the cable below the mount and frame. Adding another layer to the foam foot pads may improve the clearance.

The mount attaches to the MK4 frame with a 3030 adapter and a 45° link on the top. If I were in the mood, I’d make the 3030 adapter link longer for enough clearance beyond the M4 socket-head cap screws to get a ball-end hex wrench in there.

The small figure on the platform is a Articulated Grim Reaper done in black and white as an MMU3 test.

Now I can keep an eye on the proceedings from the Comfy Chair …

2026-05-15
Prusa MK4 Headbed Insulation

Over the winter, my Prusa MK4 printer occasionally coughed up a MINTEMP error when its platform heater cannot maintain the 90 °C called for by PETG. I finally added a cardboard insulating layer under the PCB heater:

Prusa MK4 Headbed – cardboard insulation

Yes, the blue tool layer rectangle marking the centers of the corner cutouts is offset 2.5 mm to the left:

Heatbed Insulation – LightBurn layout

The layout is not symmetric, because Prusa wanted to prevent you from installing the PCB incorrectly, so I needed three tries to get it right.

The alert reader will note the lack of the front-corner chamfers in the picture letting your fingers get under the corners to remove the steel sheet. I cut ’em off with a utility knife and you get the benefit of hindsight.

Whether this minimal insulation will solve the problem shall remain unknown until the coldest days of next winter, but eliminating drafts around the thermistor taped to the bottom of the PCB can’t possibly be a Bad Thing™.

The LightBurn layout exported to an SVG image as a GitHub Gist:

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view raw Heatbed Insulation – LightBurn layout.svg hosted with ❤ by GitHub

2026-05-14
House Sparrow vs. House Wren vs. Entrance Reducer

A friend gave Mary a small-bird birdhouse, which immediately attracted the attention of a pair of House Wrens:

Bird House entrance reducer – wren exiting

The vertical black bar is a DIY Birdsaver cord.

The entrance hole was 1-½ inch ⌀, a bit larger than the 1 inch ⌀ preferred by wrens and entirely suitable for the pair of House Sparrrows who also took an interest in the property:

Bird House – sparrow inside

This led to considerable discussion and displays of outright hostility:

Bird House entrance reducer – wren vs sparrow

Sparrows and wrens disagree on nestbuilding materials, with the wrens hauling twigs into the box and sparrows hauling them back out again.

Because wrens have better PR agents than sparrows, I intervened by taking the box apart:

Bird House – nest base sticks

Although I realize that’s a lot of work for a small bird, I dumped the contents off the patio and set about reducing the entrance hole:

Bird House – interior cleared

Because birds aren’t too fussy about looks, I sawed off half an inch of 1 inch (ID) CPVC pipe and glued it in the hole:

Bird House entrance reducer – interior glue

The outside looks marginally better:

Bird House entrance reducer – exterior glue

The sparrows continued to approach the hole at full throttle, deploying landing gear and speed brakes at the last possible moment:

Bird House entrance reducer – sparrow approach

But they no longer fit through the hole and eventually gave up trying. The wrens resumed hauling twigs, although we’re not certain they’ll finish the project, as birds tend to build several partial nests before selecting the final one.

We hope this will end on a happier note than last year’s Wreath Robins.

2026-05-13
Book Repair Tape vs. Serrated Cutter: Nope

An end-of-life roll of parchment paper contributed its serrated cutter bar as raw material for the Gridfinity Tape Dispenser:

Gridfinity Tape Dispenser – razor vs serrated blades

Those teeth look exactly like a tape cutter should look:

Gridfinity Tape Dispenser – serrated blade

It turns out that book repair tape bounces right off the pointy-but-not-keen edges, to the extent the tape did not cut at all, no matter how hard I tugged at any angle. Perhaps filing one side to make the teeth thinner would improve the results; given the cutter’s provenance it seems like putting lipstick on a pig.

The original razor blade continues to work fine, so I dropped the serrated cutter into the hollow under the tape roll against future need.

Book repair tape is tough stuff!

2026-05-12
Tour Easy: Bike Rack Tray Holder

Mary starts her garden plants at home, then hauls the trays to the garden in a plastic drawer strapped to the rack on her Tour Easy to avoid crushing the plants in the packs. I finally learned enough to make an adapter mating the drawer to the rack:

Bike Rack Tray Holder – in use

It’s made from four layers of laser-cut cardboard glued together with crossed corrugations for stiffness. I intended make a final version from glued-up plywood sheets, but it works surprisingly well as-is and I may just make another when this one wears out.

The rear view:

Bike Rack Tray Holder – rear view

The front has a cutout for the battery powering the rear camera, with the base height allowing enough meat above the battery:

Bike Rack Tray Holder – overview

The upright posts cradling the drawer may be too skinny for durability, which is why this is a prototype. The inner edges of the posts angle outward by a few millimeters to match the drawer’s mold draft.

Four feet locate the holder on the rack rails just ahead of the Ortlieb pack clips:

Bike Rack Tray Holder – rail detail

The rails are 8 mm ⌀ and the cutouts are 9 mm, because a little tolerance goes a long way. Similarly the tab widths just fit the available spaces beside the rail.

The two flat plates support the drawer and space the uprights to match the Ortlieb clips. I intended to mortise the plates into the uprights, but hot melt glue is wonderful stuff and the joint may outlast the cardboard. In retrospect, the outer edges of the plates should align with the inner sides of the uprights for maximum tidiness.

You don’t have that drawer and likely not the racks, so a picture of the LightBurn layout will give you the general idea for your hardware:

Bike Rack Tray Holder – LightBurn layout

Cut four copies of the uprights in two different orientations, glue them together, then do the obvious thing with the plates.

2026-05-11
Metric Micrometer: Percussive Adjustment

This metric micrometer has resided in my tool chest just short of forever:

Metric micrometer – detail

During that entire time, it read 0.025 mm too high: when the spindle was on the anvil, as shown, the thimble sat 2-½ divisions above the index line. Not off by much, but an annoying bit of mental arithmetic every time.

It doesn’t get a lot of use, because I rarely need more precision / accuracy than my digital calipers provide, but measuring those teeny USB wire strands finally forced me to adjust the poor thing.

A cap unscrews from the end of the thimble, revealing the setscrew locking the thimble to the spindle:

Metric micrometer – overview

Unfortunately, loosening the setscrew (with a 2 mm hex wrench) didn’t release the thimble:

Metric micrometer – thimble setscrew

After steeping the joint in Kroil penetrating oil for while, I stood the thimble on the bench block and gently tapped the spindle with a punch, just enough to break it free:

Metric micrometer – spindle adjustment

Then it was a matter of screwing the thimble back onto the frame until the spindle contacted the anvil, continuing to screw the thimble until the 0 line matched the index line, and tightening the setscrew. There was some slippage as the Kroil worked its way further into the joint, but a firm grip on both got the job done.

That should hold it for the rest of forever.

Speaking of forever, the 3D printed repair part for my caliper is now fifteen years old:

Caliper Part – Installed

I’ve been doing this for quite a while …

2026-05-08