Category: Machine Shop

Mechanical widgetry

Miniblind Roller Repair

The rod along the left side of our miniblinds turns a shaft spanning the length of the housing which pulls-and-releases three pairs of cords tilting the blades, with one roller for each pair. The cords loop over, pass under, and are secured to a tab on the roller with metal ferrules, thusly:

Miniblind roller – intact

One day, the middle section of all the blades on one miniblind stopped tilting, prompting this discovery:

Miniblind roller – broken tab

The correct solution is, of course, to replace the entire miniblind, but our 1955 window frames don’t match up well with contemporary miniblind hardware and I was unwilling to reinvent that particular wheel for this occasion.

So I laid the cords in place, put the broken tab atop them, and held the mess together with a strip of the obligatory Kapton tape:

Miniblind roller – repositioned tab

Easing some epoxy under the tab and soaking the cords atop the tape held everything together in approximately the original layout:

Miniblind roller – epoxy backfill

Two days after I reinstalled the miniblind, a second roller broke and was restored by a similar treatment. While I had the thing ~~on the bench~~ clamped in the bench vise, I preemptively slobbered epoxy on the intact roller in the hope of reinforcing it.

So far, so good!

2018-09-19

Fireball Island Figures

A cousin asked if my 3D printer could replace some figures gone missing from their old Fireball Island game board, a classic apparently coming out in a new & improved version.

Fortunately, solid models exist on Thingiverse:

Fireball Island figure - Thingiverse 536867 — Fireball Island figure – Thingiverse 536867

Unfortunately, the left arm requires support, which Slic3r supplies with great exuberance:

Fireball Island figure - Slic3r support — Fireball Island figure – Slic3r support

The vast tower on the figure’s right side (our left) seemed completely unnecessary, not to mention I have no enthusiasm for the peril inherent in chopping away so much plastic, so I replaced it with a simple in-model pillar:

The pillar leans from an adhesion-enhancing lily pad and ends one layer below the left hand, with all dimensions and angles chosen on the fly to make the answer come out right.

Works like a champ:

Fireball Island Figures - orange - on platform — Fireball Island Figures – orange – on platform

The dark band down the middle comes from the Pixel’s shutter.

They emerged with some PETG hair, the removal of which I left as an end-user experience.

I mailed a small box containing figures printed in my (limited!) palette of four colors, some spares Just In Case™, and a few QC rejects showing the necessity of lily pads.

Game on!

The OpenSCAD source code as a GitHub Gist:

	// Adding support under Fireball Island figure arm

	import("/mnt/bulkdata/Project Files/Thing-O-Matic/Fireball Island/Fireball Island figure – 100k.stl", convexity=5);

	translate([6.5,-4.0,0]) {
	intersection(){
	translate([-10/2,-10/2,0])
	cube([10,10,11.6],center=false);
	rotate([0,-5.0,0])
	rotate(180/6)
	cylinder(d=4.0,h=30,$fn=6,center=true);
	}

	translate([8/4,0,0])
	rotate(180/6)
	cylinder(d=8,h=0.2,$fn=6);
	}

view raw Figure Support Mods.scad hosted with ❤ by GitHub

2018-09-11

Bike Helmet Mirror Mount Tightening
Almost exactly three years later, it’s time to tighten the helmet mirror mount screws:

Helmet mirror mount – bottom view – setscrew

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:
- Loosen that tiny setscrew
- Unscrew & remove the mirror boom
- Remove brass screw & azimuth pivot
- Tighten screw in elevation pivot
- Tighten tiny setscrew on elevation arc
- Reinstall & tighten azimuth pivot
- Reinstall mirror boom
- Tighten tiny setscrew
Going strong after seven years!
2018-08-30
Tour Easy Daytime Running Light: First Fracture

A wind gust pushed Mary’s bike over with the daytime running light on the downward side:

Fairing Flashlight Mount – Fracture

Frankly, it’s better to have a cheap and easily replaceable plastic widget break, instead of something expensive and hard to find.

Because we live in the future, a replacement part was just a few hours away:

M2 – Nozzle Z Offset Recal – DRL Clamp

Well, a few hours after installing a replacement thermistor and recalibrating the M2, but nested repairs happen every now and again.

To the road!

2018-08-27
Shapely Fire Hydrant

A Sigelock Spartan hydrant spotted in Franklin PA:

Sigelock Spartan fire hydrant – Franklin PA

It’s certainly the shapeliest hydrant I’ve ever seen.

Of course, you need a special tool to remove the main cap, after which some internal lockwork releases the side caps, after which you can spin the valve stem recessed under the top cover. One hopes all those little bits continue sliding and releasing after a few decades, but … the status quo apparently isn’t all that good, either.

2018-08-25
Makergear M2: Nozzle Z Offset Recalibration

After a few days of downtime, an Official Makergear Thermistor arrived and is now installed amid a dab of heatsink compound:

M2 – Thermistor with heatsink compound

With the hot end set a bit higher than usual, position the platform at Z=0, lower the nozzle to be flat on the platform, tighten the lock screw, then run off a set of large calibration squares:

M2 – Nozzle Z Offset Recal – first test

The scrambled square in the front left says the Z=0 nozzle position came out just a bit too far above the platform and, indeed, the measurements (upper left numbers) say it’s off by 0.15-ish mm:

M2 Nozzle and Platform Re-Cal Measurements

Probably a little PETG stuck to the nozzle; I hate adjusting things when they’re burning hot.

The walls are also thin by a smidge, but the first order of business is to reset the Z offset with M206 Z=-2.15. With that in hand, the second set of squares came out at 3.00 to 3.08 mm (lower left numbers), which I defined to be Close Enough.

The 0.08 mm variation across the platform isn’t enough to worry about.

The first skirt threads were too thick and not solidly bonded together, but the second skirt came out normally, with a thickness from 0.21 through 0.30, which is also Good Enough.

The three-thread walls were still 1.15 mm, rather than 1.20 mm, so the EM should go from 0.95 to 0.95*1.20/1.15 = 1.05.

Next, a set of single-thread thinwall boxes to verify the Z offset and recheck the Extrusion Multiplier:

M2 – Nozzle Z Offset Recal – thinwall test

They’re dead on 3.00 mm tall, varying by not enough to worry about.

Their single-thread walls are 0.38 mm, not the intended 0.40, which suggests the EM should become 0.95*0.40/0.35 = 1.00.

It turns out the filament diameter at this part of the roll is scant of 1.75 mm, maybe 1.73 mm, so I decided to not fiddle with the EM.

The first production part came out fine:

M2 – Nozzle Z Offset Recal – DRL Clamp

The flange around the bottom of the arch support grid (in the middle) is intentional; it’s not an overstuffed first layer. The clamp sections rise from the platform just like they grew there.

So the M2 is back in operation and I have a spare thermistor on the shelf!

2018-08-24
M2 DIY Thermistor Rebuild: Autopsy

Not much to my surprise, my hack-job thermistor rebuild went bad:

M2 – thermistor – assembly 2

Having nothing to lose, I heated the brass tube over a butane flame to wreck the epoxy, which blew out with a satisfactory bang and filled the Basement Laboratory with The Big Stink.

Much to my surprise, the active ingredient still worked:

M2 DIY thermistor corpse

The multimeter reported absolutely no intermittent dropouts for as long as I was willing to watch the trace while doing other things:

DIY Thermistor Autopsy – Resistance Trend

So it must be my crappy soldering technique.

A brace of real M2 thermistors will arrive shortly …

2018-08-23