The Smell of Molten Projects in the Morning
Ed Nisley's Blog: shop notes, electronics, firmware, machinery, 3D printing, and curiosities
Using and tweaking a Makerbot Thing-O-Matic 3D printer
After nine years, it’s come to this:
The Thing-O-Matic got me started in 3D printing (and blogging!), provided an education in many useful subjects, and has long since outlived its usefulness.
A view from happier times:
Its components will live on in other projects.
One of those bittersweet moments, fer shure …
The recesses in cheap 1/4-inch shank nut drivers aren’t much deeper than the nuts, which means a screw sticking out of the nut by more than a few threads defeats the entire purpose.
Well, I can fix that:
That’s a 5.5 mm socket for M3×0.5 machine screw nuts, getting a screw clearance hole drilled into it with a #28 drill (0.1405 inch = 3.5 mm). The sockets are allegedly “forged and hardened”, but an ordinary HSS drill bit cuts like they’re butter, so I’m thinking somebody skipped the hardening step.
Turns out I had a lot of nuts to remove from black oxide M3 socket head cap screws, making a brief pause in the action totally worthwhile.
Almost exactly three years later, it’s time to tighten the helmet mirror mount screws:
That’s a 0.035 inch = 35 mil hex wrench, of which Eks reminds me “Any time your design requires a tiny [obscene gerund] wrench, you’re doing it wrong”.
The sequence goes like this:
Going strong after seven years!
These herringbone gears were part of updating my old Thing-O-Matic:
But, as the saying goes, that’s not a herringbone gear. This is a herringbone gear:
We always read the signage:
They’re parked in front of the National Museum of Industrial History in Bethlehem, PA.
Ex post facto notes from the third Squidwrench Electronics Workshop.
Exhibit various 50 Ω resistors, including my all-time favorite, a 600 W 3 GHz dummy load:
… down to a 1/8 Ω metal film resistor.
The dummy load’s N connector triggered a regrettable digression into RF, belatedly squelched because I wasn’t prepared to extemporize on AC concepts like reactance which we haven’t covered yet.
Discussion of resistor applications, power handling, power derating with temperature, etc:
Why you generally won’t find 50 Ω load resistors in Raspberry Pi circuits. Cartridge heaters for 3D printers, not aluminum power resistors, although everyone agrees they look great:
Discussion of voltage vs. current sources, why voltage sources want low internal resistances and current sources want high resistances. Bungled discussion of current sources by putting diodes in parallel; they should go in series to show how added voltage doesn’t change current (much!) in sources driven from higher voltages through higher resistances:
Use Siglent SDM3045X DMM in diode test mode to measure forward drop of power / signal / colored LEDs, discuss voltage variation with color / photon energy. Measure 1.000 mA test current for all forward voltages.
Compute series resistor (500 Ω) to convert adjustable power supply (the digital tattoo box, a lesson in itself) into reasonable current source; roughly 10 V → 20 mA. Find suitable resistor (560 Ω) in SqWr junk box parts assortment, digression into color band reading.
Wire circuit with meters to measure diode current (series!) and voltage (parallel!), measure same hulking power diode (after discovering insulating washers now in full effect) as before in 1 mA steps to 10 mA, then 15 and 20 mA, tabulate & plot results:
Discover warm resistor, compute power at 20 mA, introduce cautionary tales.
Lesson learned about never returning parts to inventory, with 560 Ω resistor appearing in diode drawer. Cautionary tales about having benchtop can of used parts as front-end cache for inventory backing store.
Another intense day of bench work!
These white ABS fairing plates held the Zzipper fairing on my Tour Easy ‘bent since 2011:
Over the course of those six years I’ve ridden about 6 × 2500 = 15000 miles, maybe more, maybe less. I can ride at 15 mph for a while, but 12 mph seems a more reasonable overall estimate, making for a bit over 1000 hours. Figure the bike spends that much time sitting outdoors at the far end of the ride and you’re looking at what 2000+ hours of sunlight does to ABS.
In addition to discoloration, the plates have become brittle, as shown in the chips in third one down, and permanently deformed due to the pressure of the nylon bolts compressing the black foam against the fairing.
A closer look at the top plate:
My 3D print quality has improved a lot since then.
New plates of a different design are, as NASA puts it, “in work”.
The pix come from the new LiDE 120 scanner. It does a good job with the color, but has (for good reason) an essentially zero depth of field: if it’s not on the glass, it’s out of focus.
This ABS slab emerged from the Thing-O-Matic in early 2012:
The Zire would power on whenever the switches clicked or that little joystick moved, which happened regularly enough to be annoying.
Mary made a small case that matched the other pouches I carry around:
She made the case to fit an HP48 calculator, but it was close enough for the Zire.
Time passed, the Zire died, I started carrying a Kindle Fire in another pocket, but the ABS slab provided a convenient stiffener between some Geek Scratch Paper and the various pencils / pens / markers / screwdrivers / flashlight filling the available space.
Unfortunately, minus the backup of an electronic slab, the protector finally failed along an obvious stress riser:
I cut a similar rectangle from a sheet of unknown flexy plastic, rounded the corners, clipped the pencils & whatnot to it, and maybe it’ll survive for a while.
The Smell of Molten Projects in the Morning 