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: Oddities

Who’d’a thunk it?

Tiny Cylinder Test Object
A discussion on the M2 forums prompted this test object:

Tiny Cylinder – 0.9×9.0 mm

Sliced with Slic3r for PETG at 1 mm/s, with fans in full effect. It sits amid a 5 mm brim, inside a skirt that uses 15 mm of filament, giving it a Washington Monument aspect.

The challenge was to print a 0.7x9.0 cylinder, which doesn’t work well with a 0.35 mm nozzle. Instead, I went with 0.9 mm diameter. The result measures 1.1 mm over all the obvious bumps, so it’s surprisingly close. The “nail head” at the bottom most likely comes from the hot end depressurizing as it suddenly transitions from 15 mm/s in the brim to 1 mm/s for the cylinder.

Fairly obviously, you can’t print something like that at full speed (50 mm/s was claimed for a Rep 2 and I don’t believe that for an instant). Indeed, it’s such a pathological model that Slic3r’s minimum layer time and small perimeter settings had no effect; I had to manually set the extrusion speed to 1 mm/s in order to make it work. Plus adding that brim, because I knew it wouldn’t stand by itself.

Other than that, printing it was no big deal.

A picture from that M2 forum discussion suggests you can go crazy with this stuff:

20 mm, 40 mm, 60 mm and 120 mm

The OpenSCAD source code for my version:
```
cylinder(d=0.9,h=9,$fn=8);
```
There, now, that wasn’t so hard, was it?
2015-11-04
Murder Mystery

The stains appeared black-red under the cold LED light and my first thought went along the lines of “Somebody dragged a corpse out of the kitchen!”:

Restaurant back door

The dumpsters sit off the sidewalk behind me on the left, so, most likely, they just have a bit of trouble maneuvering overstuffed trash cans and grease tanks around the door. At least, that’s what we hoped.

Notice how the door hinges the wrong way? Perhaps the architect never anticipated moving waste from the kitchen to the dumpsters.

The food was OK (we did not order the Chef’s Special Long Pig), but their overly loud “background music” reverberated far too long inside a cavernous room with hard walls. We gave it 2/10: would not eat there again.

This has absolutely nothing to do with stabbing guides.

2015-10-31
Stabbing Guides

Many of my solid models have holes for alignment pins made from filament snippets that let me glue the pieces together with near-perfect registration:

Alignment Hole and Pin

A reader who designs oil-field equipment for a living pointed out that, in his world, they’re called “stabbing guides”:

Stabbing_Point_on_Leg_1

He specifies steel plate and welding instructions:

Stabbing_Guide_Type_3

Stabbing guides for large modules may rise 25 feet above the deck plates…

After they install all the little bits on a “part” like this:

Generator Module – during assembly

It fits neatly atop the stabbing guides and gets welded to a somewhat larger structure:

Generator Module – installed

No sissy plastic for him!

My puny pins don’t qualify as stabbing guides, but forgive me if I sneak the term in every now and then…

Thanks, Tom!

2015-10-27
0D3 Voltage Regulator Tube

A quartet of ceramic octal tube sockets arrived from halfway around the planet and matched up nicely with the business end of a 0D3 voltage regulator tube from the Hollow State Electronics box:

0D3 voltage regulator tube in socket

If the 1-48 on the side of the tube base (facing away in the picture) means anything, then General Electric built it in January 1948.

The pinout view in the datasheet assumes you’re looking at the bottom of the socket, which makes perfect sense given the hand-wired chassis construction techniques of the day:

0D3 Voltage Regulator Tube – pinout

So the view is backwards when seen from the top, not that you’d ever need it:

Ceramic octal tube socket – 0D3 pinout

The internal jumper across pins 3-7 allows you to disconnect the downstream circuit when the regulator isn’t in the socket, which is a Very Good Idea with a shunt regulator.

Not having a 200 V power supply ready to hand, but having recently restocked the 9 V alkaline battery box, this actually worked:

0D3 voltage regulator test setup

That’s 16 x 9-ish V = 150 V across the battery terminals, plus a 50 V adjustable bench power supply coming in on clip leads from the upper right, with current shown on a digital panel meter across a 1 Ω sense resistor. The classic 1.5 kΩ carbon resistor emerged from from a coffee can of parts that Came With The House™ and seemed appropriate for the occasion.

The tube conducts a few milliamps through a small plasma filament discharge at 150 V. The current ramps up to about 10 mA as the supply voltage increases to 180 V, whereupon the tube fires and the current jumps to 30 mA (which is less than the spec, but I ran the power supply in constant-current mode to avoid whoopsies).

Reducing the current to 10 mA slightly reduces the area involved in the plasma discharge, but the tube still produces a nice display through the mica spacer / insulator atop the plate:

0D3 voltage regulator – 10 mA current

That isn’t quite in focus, but should give you the general idea.

I didn’t measure the operating voltages across the tube, mostly because I didn’t want more cheap clip leads cluttering the bench.

It’d make a very low intensity nightlight that dissipates a watt or two. Boosting the current to the absolute maximum 40 mA would brighten it up a bit, but dissipating 6 W in the tube probably won’t do it any good.

This obviously calls for an Arduino monitoring the tube current with a Hall-effect sensor and regulating it with a hulking MOSFET…

2015-10-22
Documentation Always Lags the Hardware

Found at the last rest area in Massachusetts on I-90 westbound:

Gas Pump Instructions

I suppose you just poke buttons until something happens…

2015-10-21
Forester Load Capacity

You never realize how big automobile tires are, until you see them out of context:

Forester loaded with Sienna snows

The Sienna spends its days commuting near what used to be the engineering glory of Rt 128, and snow season is comin’ on strong. We hauled the snows out and the summer tires back on our way to a brief vacation on Cape Cod.

I have no illusions that the two ratcheting straps on each pair of tires + wheels will hold them in place during an actual crash, but at least they’re not rattling around. The tiedown points next to the hatch have a 20 kg load limit, which is pretty close to the weight of a single tire + wheel. The rear seat anchors aren’t rated as tiedown points, but, hey, if they can hold the seat up during a crash, they’re good enough for me.

We’ve always packed lightly and, these days, we bring no more than absolutely necessary. Those tires sure didn’t leave room for much else…

2015-10-19
A Mystery Block of Electronics

Back in the day, this surely represented an achievement in high-density electronics packaging:

Electronics Block – 1

A view from the other corner suggests the layout wasn’t quite right:

Electronics Block – 2

It has no identification, the transistors have house numbers, and the PCB looks like a prototype. As nearly as I can tell from the capacitor date codes, it dates back to the mid-1960s.

Two pairs of electrically isolated and thermally bonded transistors suggest an analog Class-AB driver + amplifier or a pair of digital flipflops, but there’s no way to tell.

Judging from the ugly solder and dislodged via rings, somebody had to apply extensive modifications after initial assembly; it trailed half a dozen red wires soldered to vias and components.

One hopes it eventually worked…

2015-10-16