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.

Tag: Improvements

Making the world a better place, one piece at a time

Expedient Caster Wrench

Cranked down as far as it would go, a new adjustable height workbench in Mary’s sewing room turned out to be just slightly higher than the other work surfaces adjoining it, so I replaced its 3 inch casters with 2 inch versions:

Sewing bench – 2 vs 3 inch casters

The bench arrived as a kit and included the 17 mm flat wrench required to snug the hex head on the 3/8-16 threaded stem atop the 3 inch caster against the bottom of the bench foot. The 2 inch caster also has a threaded stem, but of course it has a 14 mm hex head.

I traced around a 14 mm open-end wrench on a scrap of aluminum and introduced the outline to Tiny Bandsaw:

Improvised 14 mm caster wrench – rough cut

A little belt sander action cleaned up the outside, some hand filing matched the wrench to the hex, and it came out OK, even before I scrubbed the dirt off its white-ish pebble-finish coating:

Improvised 14 mm caster wrench – finished

The bare steel wrench arrived with the bench and has 13 and 17 mm openings. I briefly considered embiggening the 13 mm end, but came to my senses.

Aluminum isn’t a particularly good metal for wrench duty, but this one had to apply maybe 1/3 of a turn to each of four stems, stopping when snug, and it performed just fine. It’s now sleeping in the wrench drawer, dreaming of another job that may never arrive.

The smaller casters lowered the bench by about an inch, whereupon cranking the surface up a bit less than half an inch aligned it perfectly.

2022-03-07
Work Glove Security Tags

Having worn my work glove collection to exhaustion, the fanciest two pairs in a new selection came with elaborate security tags:

Elaborate Security Tag dissection

Finding a standard tag inside inside the fancy shell shouldn’t come as any surprise, but I’m surprised the retail loss ratio for a pair of $20 gloves can support that much hardware.

I went through the self-checkout area and didn’t do anything special, so either those lanes don’t have tag scanners or the tags are security theater.

2022-03-03
Gidget II Sewing Table: Temporary Juki Insert

Mary’s new sewing table just arrived, but the laser-cut acrylic insert fitting around her Juki sewing machine is still a month or two away. Until then, a simple cardboard replacement must suffice to fill the gap:

Juki temporary table insert

The rectangle just to the left of the needle is a hatch for bobbin changes. Sheer faith and an interference fit between layers of Kapton tape holds it in place with surprising force.

I wanted to tape the cardboard edges to the machine and the table to smooth out the transitions, but her Supreme Slider slippery sheet may solve the problem without adhesives:

Juki temporary table insert – Super Slider

The “insert” is a 1/4 inch thick double-layer corrugated cardboard sheet, utility-knifed from a huge box. She layers cardboard under the wood chips in her Vassar Farms garden paths to discourage the weeds; this seemed like a perfectly reasonable diversion.

2022-03-02
CNC-3018XL X-Axis Recalibration
Plotting the backlash / calibration target on both the CNC-3018XL and the MPCNC quickly showed, contrary to what I expected, the MPCNC was dead-on accurate, albeit with some wobbulation and a trace of backlash:

MPCNC – Backlash test – detail

Although it looks ug-u-lee, the (lower speed) drag knife cuts come out nice and, because the entry and exit moves match the main cut, the minimal backlash wasn’t a problem.

Turns out only the X axis on the 3018XL had a problem:

Cal Target – 400 step-mm – merged

Apparently the longer leadscrew I installed as part of the “XL” conversion has a small thread pitch error: about 1 mm short in every 250 mm of travel. I don’t have any (definite, non-handwavy) method to measure the pitch directly, other than by running the follower nut and measuring the results, but it’s consistently short.

Quite some time ago (after blowing up the OEM controller board), I set up the Protoneer CNC board in 1:8 microstep mode, making the GRBL $100 setting a nice, round 400 step/mm for a two-start leadscrew with 2 mm pitch and 4 mm lead:
```
400 step/mm = (200 step/rev * 8 µstep/step) / 4 mm 
```
After a few more measurements suggesting the leadscrew actually traveled 249.2 mm, the correct value will be:
```
401.28 step/mm = 400 step/mm × 250 mm / 249.2 mm
```
To verify I understood the problem and solution, I set $100 to a few integer values around the goal:

Cal Target – stacked – 399-402 step-mm

The top image shows the leftmost line at the 10 mm mark on the scale, because it’s easier for me to match the ink line with an engraved line, rather than the non-line at the end of the ruler.

The other images show the results for $100 set to 399, 400, 401, and 402 step/mm, respectively. The results last two results bracket the desired 250 mm outcome, with 401 step/mm being Close Enough™. GRBL accepts a floating point step/mm value, so I set $100 to 401.28, but I was unable to convince myself the result came out consistently different than 401.00.

Plotting both the tick marks (green) and the knife path (red) on the 3018XL, then cutting the bare paper on the MPCNC, showed the two machines now agree on where the knife should fall. The outer end of the tick marks extends 1 mm beyond the cut line to ensure small misalignments do not produce an obvious white gap around the edge of the deck.

The Y axis continues to match:

Tek CC – 2022-02-14 – Y detail

And now the X axis looks just as good:

Tek CC – 2022-02-14 – X detail

The drag knife corners are rounded, as you’d expect. The cut seems slightly offset from a small origin touch-off error, but the scales now match.
2022-03-01

ShopVac Nozzle Caddy

Shortly after acquiring the Greatest ShopVac, I zip-tied half a foot of cardboard tube to the handle to corral the nozzle and keep the ungainly hose from sprawling across the floor. While disembowling the Ottlite into a mini-lathe light, the plastic trim joining the baseplate to the vertical tube cried out to become a nozzle caddy:

It was exactly the right size and shape (by my admittedly slack standards) to hold the nozzle, plus being destined for the trash, so all it needed was a pair of clamp brackets conjured from the vasty digital deep:

ShopVac Nozzle Caddy - solid model — ShopVac Nozzle Caddy – solid model

The bosses fit into a tapered slot along what was the rear side, with a pair of 4 mm holes at each end for screws into threaded brass inserts epoxied into the brackets:

ShopVac Nozzle Caddy - clamps mounted — ShopVac Nozzle Caddy – clamps mounted

They obviously descend from the many clamp mounts I’ve made for everything from garden hoses to bike running lights. A pair of 4 mm SHCS squish the clamp around the handle, with a strip of electrical tape improving plastic-to-metal griptivity:

ShopVac Nozzle Caddy - side view — ShopVac Nozzle Caddy – side view

The clearance just barely allows a nylock nut atop a washer and you’ll want to trim those 40 mm screws to an exact fit, but it came out pretty well.

The original dimension doodle with some modeling ideas that didn’t survive more thinking:

ShopVac Nozzle Caddy - Dimension Doodle 1 — ShopVac Nozzle Caddy – Dimension Doodle 1

A more detailed doodle with brass inserts instead of the nylock nuts and an aluminum spreader plate that was obviously not necessary:

ShopVac Nozzle Caddy - Dimension Doodle 2 — ShopVac Nozzle Caddy – Dimension Doodle 2

In retrospect, the inserts would make more sense.

The angle doodles convinced me not to bother modeling either the slot’s taper along its length or its mold draft.

Kinda looks like it grew there and makes one wonder why they don’t include a caddy as a standard option.

The OpenSCAD source code as a GitHub Gist:

	// ShopVac Nozzle Caddy
	// Ed Nisley KE4ZNU 2022-02

	Layout = "Show"; // [Handle,Block,Show,Build]

	HandleOD = 20.0;

	//- Extrusion parameters must match reality!

	/* [Hidden] */

	ThreadThick = 0.25;
	ThreadWidth = 0.40;

	HoleWindage = 0.2;

	Protrusion = 0.1; // make holes end cleanly

	inch = 25.4;

	function IntegerMultiple(Size,Unit) = Unit * ceil(Size / Unit);

	ID = 0;
	OD = 1;
	LENGTH = 2;

	//———-
	// Dimensions
	// Handle lies along X axis

	Handle = [200,HandleOD,HandleOD]; // X = longer than anything else

	WallThick = 5.0; // Thinnest printed wall

	Screw = [4.0,7.0,25.0]; // M4 socket head cap screw
	Washer = [4.5,9.0,0.8]; // M4 washer
	Insert = [4.0,5.9,10.0]; // M4 brass insert

	Block = [15.0,Handle.y + 4WallThick + 2Screw[ID],HandleOD + 2*WallThick]; // overall clamp block
	echo(str("Block: ",Block));

	Bosses = [[Block.x,9.5,13.0],[Block.x,15.0,9.0]];

	ScrewOC = Handle.y + 2*WallThick + Screw[ID];

	Kerf = 1.0; // cut through middle to apply compression

	Gap = 1.25;

	CornerRadius = Washer[OD]/2;

	//———————-
	// Useful routines

	module PolyCyl(Dia,Height,ForceSides=0) { // based on nophead's polyholes
	Sides = (ForceSides != 0) ? ForceSides : (ceil(Dia) + 2);
	FixDia = Dia / cos(180/Sides);
	cylinder(d=(FixDia + HoleWindage),h=Height,$fn=Sides);
	}

	// Shopvac handle

	module Handle() {

	rotate([0,90,0])
	translate([0,0,-Handle.x/2])
	rotate(180/(4*8))
	PolyCyl(Handle.y,Handle.x,4*8);
	}



	// Clamp block

	module ClampBlock(BossID=0) {

	difference() {
	union() {
	hull()
	for (i=[-1,1], j=[-1,1]) // rounded block
	translate([i(Block.x/2 – CornerRadius),j(Block.y/2 – CornerRadius),-Block.z/2])
	cylinder(r=CornerRadius,h=Block.z,$fn=8);
	translate([0,0,-(Block.z/2 + Bosses[BossID].z/2 – Protrusion)])
	cube(Bosses[BossID],center=true);
	}

	for (j = [-1,1]) // screw holes
	translate([0,j*ScrewOC/2,-(Block.z/2 + Protrusion)])
	rotate(180/6)
	PolyCyl(Screw[ID],Block.z + 2*Protrusion,6);

	cube([2Block.x,2Block.y,Kerf],center=true);

	Handle();

	translate([0,0,-Block.z])
	rotate(180/6)
	PolyCyl(Screw[ID],Block.z,6);

	translate([0,0,-(Handle.z/2 + Insert[LENGTH])])
	rotate(180/6)
	PolyCyl(Insert[OD],Handle.y,6);
	}
	}

	// Splice block less handle bore

	module ShapedBlock() {
	difference() {
	ClampBlock();
	Handle();
	}
	}




	//———-
	// Build them

	if (Layout == "Handle")
	Handle();

	if (Layout == "Block")
	ClampBlock(BossID=0);

	if (Layout == "Show") {
	color("Green",0.25)
	Handle();
	xofs = -((len(Bosses) – 1)/2 * Gap*Block.x);
	for (i=[0:len(Bosses) – 1])
	translate([xofs + iGapBlock.x,0,0])
	ClampBlock(i);
	}

	if (Layout == "Build") {
	yofs = -((len(Bosses) – 1)/2 * Gap*Block.y);
	for (j=[0:len(Bosses) – 1])
	translate([0,yofs + jGapBlock.y,0])
	translate([0,0,Block.x/2])
	rotate([0,90,0])
	ClampBlock(j);
	}

view raw ShopVac Nozzle Caddy.scad hosted with ❤ by GitHub

2022-02-25

Fluorescent Shop Light Ballast Caps

It never ceases to amaze me that these capacitors appear in the AC power line circuits inside old-school fluorescent shop lights:

Shop light ballast cap

It really is a capacitor:

Shop light ballast cap A – test

Its sibling from the other end of the fixture had more ESR:

Shop light ballast cap B – test

Both were likely within spec, whatever that means.

I have no idea what’s lurking inside the tidy LED tubes now living in that same fixture, of course.

2022-02-24
Underwriter’s Knot

Found inside a fluorescent desk lamp being salvaged for possible use as an LED task lamp:

Fluorescent Desk Lamp – Underwriters Knot

It’s one of the few Underwriter’s Knots I’ve ever seen in the wild. Many recent (i.e., built in the last half-century) lamps pass the cords through a plastic clamp or depend on simple bushings, with some just ignoring the problem.

This anonymous lamp sports the usual Made in China sticker, but also features a genuine-looking UL sticker complete with elaborate holograms, so it may well have been sold by a reputable company. IIRC, it came from a trash can in a Vassar College hallway, back when in-person meetings were a thing; perhaps Vassar required known-good electrical hardware.

2022-02-11