Category: Software

General-purpose computers doing something specific

Quick-n-Easy Window Shade End Cap
While tracking down an air leak in a living room window, I noticed one of the cellular blinds was missing an end cap, so I scanned a pair of surviving caps:

Living Room shade end caps – level adjust

Blow out the contrast, save as a JPG.

Import into LightBurn:
- Trace the outlines into paths
- Use LightBurn’s shape optimization tool to dramatically reduce the number of nodes & smooth the outlines
- Overlay & align the shapes
- Export as an SVG file
Import into Inkscape:
- Put the paths on named layers
- Center around an alignment mark
- Save as an Inkscape SVG
Living Room shade end caps – Inkscape alignment

It is slightly tilted, but that doesn’t matter. You could devote more time to smoothing / reverse-engineering the shapes, but that doesn’t make much difference, either.

Inkscape exports the SVG coordinates with respect to the overall page origin in the lower left corner, so when OpenSCAD imports the SVG the paths end up far away from the origin. The trick is to put a 2 mm diameter circle at a known location, center the paths around it, then have OpenSCAD use the circle’s location to recenter the paths.

Because Inkscape uses the lower left corner of each shape as its origin, you must put the circle at (99,99) to have its center at (100,100). That is one of the many reasons you (well, I) can’t use Inkscape as a CAD program.

Import into OpenSCAD, recenter, and extrude the shapes:
```
CapCenter = [100,100];

PlateThick = 1.8;       // thickness of visible end cap

HolderTall = 10.0 + PlateThick;

union() {
  linear_extrude(height=PlateThick)
      translate(-CapCenter)
            import("Living Room shade end caps - Inkscape.svg",layer="Exterior");
  linear_extrude(height=HolderTall)
      translate(-CapCenter)
            import("Living Room shade end caps - Inkscape.svg",layer="Retainer");
}
```
Which produces a solid model:

Living Room shade end caps – solid model

Save the model as 3mf, import into PrusaSlicer, and slice:

Living Room shade end caps – PrusaSlicer preview

Making the retainer shape a little wider would be a good idea to get better infill, but it’s a slip fit into the blind (surely why it fell out long ago) and need not withstand any stress.

Print as usual:

Living Room shade end cap – on platform

And then It Just Works™:

Living Room shade end cap – installed

It’s sitting atop a bookcase while I finish tinkering with its window.

All that seems like a lot of fiddling around, but it uses each program to its best advantage and it’s surprisingly easy after the first few models.
2025-01-09
PrusaSlicer Scarf Joints

The release notes for PrusaSlicer 2.9 mention the addition of scarf joints on outer perimeters. Smooth joints seem like a Good Idea™, so I turned it on for comparison with a recent object:

Double Gear fidget toy – scarf vs normal

Those are flipped from the as-printed orientation: the orange ring builds upward, starting with two concentric threads on the platform.

The normal aligned joint is on the right above, with a closer look here:

Double Gear fidget toy – normal joInt

The scarf joint has a offset between layers:

Double Gear fidget toy – scarf joint

The PrusaSlicer visualization shows the effect, looking up from below the platform:

Double Gear fidget toy – scarf joint visualization

The blue PETG-CF parts have no visible seams anywhere with either setting, probably because the stuff swells slightly and obliterates any subtle differences.

Scarf joints don’t make much difference for a fidget toy, but should improve the outcome for more critical circular / spherical models.

2024-12-31
OMTech 60 W Laser: Manual Pulse Button

I want to put the HLP-200B Laser Power Meter at the tube’s exit, just upstream from Mirror 1, where it can measure the laser’s power output before the mirrors get into the act. Reaching the Pulse button on the machine console requires much longer arms than any normal human can deploy, plus a certain willingness to lean directly over a laser tube humming with 15 kV at one end.

Perusing the KT332N doc brings up a hint, blocked in red so you can make some sense of it:

KT332N Input bits

A few minutes with boxes.py produces a simple two-compartment box and a few minutes with LightBurn adds two holes:

Remote Switch Box – LightBurn layout

Another few minutes produces the box from Trocraft Eco, which is not quite thin enough for the switch (from my Box o’ Clicky Buttons) to snap into place, but a few dabs of hot melt glue hold it down:

Laser remote pulse button – installed

Double-sided foam tape sticks the box to the laser frame and the red-n-black cable snakes all the way across the back of the machine and through the electronics bay to the IN2 and GND terminals of the KT332N INPUT block:

Laser remote pulse button – Ruida KT332N wiring

With the laser head parked at a safe spot and all interlocks happy, it works:

Laser remote pulse button – demo

That is a re-enactment, because I lack sufficient dexterity to handle a phone with my left hand, poke the button with my right finger, and not damage anything important.

The general idea is to make it very difficult to inadvertently press that button: you must want to fire the laser with the tube compartment hatch up (it has no interlocks) and the control panel out of sight on the top-front of the machine.

Setting the power to 30% and putting the meter in harm’s way:

HLP-200B – Laser tube exit

Again, a reenactment based on actual events.

Five pulses later:

40.8 W
42.4
42.3
41.2
40.7
41.5 W avg
0.82 W std dev

For the record, those five pulses dumped about 5 × 42 W × 10 x ≅ 2000 W·s = 2 kJ into the meter, raising it from “chilly basement ambient” to “be careful where you hold it”, thus making the meter’s aluminum case the least-efficient handwarmer in existence.

The 30% PWM measurements at the center of the platform came out slightly lower: 38.5 W average with a sample standard deviation of 2.2 W.

The large standard deviations prevent firm conclusions, but, yeah, the power at the tube exit seems about right, before two mirrors and ≅800 mm of path length take their toll.

The LightBurn SVG layout as a GitHub Gist:

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view raw Remote Switch Box – LightBurn layout.svg hosted with ❤ by GitHub

2024-12-30
PrusaSlicer Flatpak: Adding an NFS Filesystem
PrusaSlicer V 2.9.0 for Linux arrives as a Flatpak, instead of the previous AppImage, which wouldn’t matter except that the Flatpak sandbox prohibits access to anything outside each user’s home directory. I long ago set up access to the fileserver in the basement through filesystems mounted on /mnt, which is now inaccessible.

Obviously, I’m not the first person to hit this issue, as some diligent searching turned up a hint leading to a description of Flatpak permissions, which eventually produced:
```
sudo flatpak override com.prusa3d.PrusaSlicer --filesystem="/mnt/bulkdata"
```
Overall, 2.9.0 seems significantly more sluggish and uglier than the 2.8.x series, but at least Prusa still supports Linux.

Just to show PrusaSlicer can fetch files from the server and to have some pictures enhancing this post’s negligible SEO, I built a couple of Gear Fidget Toys:

Double Gear fidget toy – on platform

Which pop off the platform ready to roll:

Double Gear fidget toy – finished

A trace of silicone grease eased between the pieces on a slip of paper makes the spinning action so smooth.

As usual, the multi-material version takes twice as long to build due to all the filament swapping. I think I must improve the MMU3’s spoolholders, because the MMU3 (very) occasionally fails to ram the filament into the extruder, seemingly due to the force required to pull filament from the recalcitrant spools.
2024-12-24
HLP-200B Laser Power Meter: Holder / Stand

The overall measurement process for the HLP-200B laser power meter requires more coordination than I can muster on a dependable basis, so a third hand seemed in order:

HLP-200B Power Meter – target setup

In actual use, a pair of finger-crushingly strong magnets laid on the base hold it firmly to the honeycomb.

Because a CO₂ laser beam is invisible, the only way to know where it hits is to char a bit of paper:

HLP-200B Power Meter – target detail

With that evidence, I can jog the platform up-and-down and the gantry front-and-back to center the beam on the paper target and, thus, on the sensor behind it. That process happens at each test position across the platform:

HLP-200B Power Meter – targets

The meter shuts down a mere six seconds after completing each measurement, which means I must keep the lid open, listen carefully, and react quickly. Firing the laser thus requires defeating the lid interlock specifically wired to prevent that from happening:

Laser lid interlock sensor

Rather than install a switch to bypass the interlock, I taped a steel cover harvested from defunct electronics over the sensor:

Laser lid interlock sensor – bypassed

Which has the useful side effect of preventing me from closing the lid with the interlock defeated.

The holder is just slightly larger than the meter’s handle and some clamps produced a snug fit while the glue cured:

HLP-200B Power Meter – holder gluing

The holder keeps the meter sensor at the same position vertically and within about a millimeter horizontally. The laser beam seems to be around 5 mm in diameter (the scorches above come from the hottest central part), so the beam should hit the same position on the sensor during successive measurements, making them far more repeatable than my waving it around by hand.

The LightBurn SVG layout as a GitHub Gist:

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view raw HLP-200B Laser Power Meter – holder.svg hosted with ❤ by GitHub

2024-12-23
HQ Sixteen: Chin Light

Setting the Handi-Quilter HQ Sixteen handlebars at a useful angle aimed the main PCB’s white LEDs at the front of the arm, rather than down at the needle:

HQ Sixteen Chin Light – off

Having caused the problem, I must fix it:

HQ Sixteen Chin Light – results

The light comes from a small chip-on-board LED affixed under the chin of the machine arm with heatsink tape:

HQ Sixteen Chin Light – detail

Yes, the pool of warm white COB LED light clashes horribly with the cool white 5 mm LEDs lighting the background (not to mention wintry daylight from the windows), but it’s sufficiently OK.

I intended to run the wiring inside the machine arm, but all the pre-existing holes I wanted to use were oiling access points or blocked by whirling shafts inside, so the wire runs along the outside:

HQ Sixteen Chin Light – wiring

The Handi-Quilter control & lighting goes through the bare gray ribbon cable to the handlebars, so I’m not too far down the stylin’ scale. The next version of the machine has round external cables, but this machine is what it is.

I mounted the 12 VDC supply to the back panel of the machine’s power box with five 3 mm holes:

HQ Sixteen Chin Light – power supply

A bag of right-angle barrel connectors will arrive shortly.

The exposed wiring at the top (the white wires carry switched 120 VAC from the PCB inside the box) seemed … unaesthetic, so I conjured a cover from the vasty digital deep:

Power Supply Cover – solid model

Which fit neatly into place on the first try:

HQ Sixteen Chin Light – supply cover fit test

That’s a trial fit, because I am not pulling the machine apart again until there’s more work to do inside.

The blurry rocker switch below the Chin Light supply controls the machine power: turn it on and everything lights up as it should.

The OpenSCAD source code as a GitHub Gist:

2024-12-18

HQ Sixteen: Grip Angle Caps

The stock Handi-Quilter HQ Sixteen has serviceable black rubber caps covering the holes for the grips:

HQ Sixteen - original front handlebar mount — HQ Sixteen – original front handlebar mount

Because we live in the future, I can do better than that:

HQ Sixteen - grip cap left — HQ Sixteen – grip cap left

In truth, the plastic grip plug now sticks up into the hole just beyond the top setscrews, leaving not enough room for the black plugs, so I had to make new covers.

They’re a multi-material print using white PETG to kinda-sorta match the machine and blue PETG-CF to match the other plastic parts. The colors in the solid model just distinguish the two materials:

Handlebar Grip Mount - plug caps - solid model — Handlebar Grip Mount – plug caps – solid model

The white covers have recesses exactly fitting the text:

Handlebar Grip Mount - cap text recess - solid model — Handlebar Grip Mount – cap text recess – solid model

In some cases that’s not needed, but I’m unsure how PrusaSlicer knows what I intend and chopping the text out was easy, so that’s how I did it.

I did not realize applying a transformation, like translate() or BOSL2’s syntactic sugar left(), to both the cover and the text implicitly joins them into a single “object”, so the slicer can’t distinguish them as separate materials. As a result, the OpenSCAD code must move the pieces separately:

if (Layout == "Covers") {
     left(Plug[OD]) GripCover(LEFT,"Cover");
     left(Plug[OD]) GripCover(LEFT,"Text");

     right(Plug[OD]) GripCover(RIGHT,"Cover");
     right(Plug[OD]) GripCover(RIGHT,"Text");
}

Which is awkward, but not insurmountable.

Export the model as a 3mf file, import it into PrusaSlicer, and you get separate objects for the cover and the text. Assign different materials and slice to produce a multi-material result, with the Wipe Tower in the background:

Handlebar Grip Mount - cap first layer - PrusaSlicer — Handlebar Grip Mount – cap first layer – PrusaSlicer

They must print face down to merge the two colors into a single flat surface with a nubbly texture from the steel sheet’s coating.

Disks of adhesive sheet will eventually stick them atop the plugs, but for now they’re just dropped into the holes.

The OpenSCAD source code as a GitHub Gist:

	// Handiquilter HQ Sixteen front handlebar grip angle mount
	// Ed Nisley – KE4ZNU
	// 2024-11-29

	include <BOSL2/std.scad>

	Layout = "Show"; // [Show,Build,Plug,Block,Covers,Cover]

	Material = "All"; // [All,Cover,Text]

	// Angle w.r.t. base
	GripAngle = 20; // [10:30]

	// Plug glued, not screwed
	PlugGlue = true;

	// Square nuts, not inserts
	SquareNuts = true;

	// Additional length of bottom
	AddLength = 0; // [0:20]

	// Separation in Show display
	Gap = 5; // [0:20]

	/* [Hidden] */

	HoleWindage = 0.1;
	Protrusion = 0.1;
	NumSides = 234;

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

	Grip = [19.7,22.4,20.0]; // (7/8)*INCH = 22.2 mm + roughness, LENGTH=OEM insertion depth
	GripRadius = Grip[OD]/2; // used everywhere

	Plug = [15.0,Grip[OD],45.0]; // inserts into handlebar base
	PlugRim = [Plug[ID],25.0,10.0]; // … sits against handlebar base

	BaseScrewPositions = [[11.0,12.0],[27.0,29.0]]; // setscrew offsets from rim top: side,rear

	BaseCutout = [Plug[OD]/2,Plug[ID],10]; // cable cutout into base
	BaseCutoutOffset = 18.0; // … centerline position w.r.t. rim

	WallThick = 7.0; // should at least fit insert length

	SupportSag = 0.4; // vertical sag over support structure

	MidLength = AddLength + 3.0; // total length allowing for grip tube stop

	TopOD = PlugRim[OD] + 2*WallThick;
	BotOD = Grip[OD] + 2*WallThick;

	BaseScrew = [4.0,4.8 + HoleWindage,1.0]; // HQ 10-32 screws, LENGTH=capture dent

	Insert = [5.4,6.0,6.0]; // M4 inserts in plug rim
	//Insert = [4.0,5.0,5.0]; // M4 inserts in plug rim
	Screw = [3.5,4.0,1]; // M4 screws through angle block to inserts
	ScrewHeadOD = 7.4 + 0.4; // M4 BHCS head + comfort
	SquareNut = [4.0,7.0,3.0 + 0.4]; // M4 square nut LENGTH + inset allowance
	NutInset = GripRadius – sqrt(pow(GripRadius,2) – pow(SquareNut[OD],2)/4);

	PinOD = 1.2; // plug reinforcing pins
	NumPins = 5;

	CoverThick = [3.5,9.5]; // low and high sides of grip covers
	CoverAngle = atan((CoverThick[1] – CoverThick[0])/Plug[OD]);

	LogoText = ["Sew","Fine"];
	LogoFont = "Fira Sans Condensed:style=SemiBold";
	LogoSize = 7.5;
	LogoColor = "Red";
	LogoThick = 0.8;

	//———-
	// Simulator for aluminum plug replacing handlebar in base

	module BasePlug() {

	difference() {
	union() {
	tube(Plug[LENGTH],(Plug[OD] – HoleWindage)/2,Plug[ID]/2,anchor=DOWN);
	tube(PlugRim[LENGTH],PlugRim[OD]/2,PlugRim[ID]/2,anchor=DOWN);
	}

	up(BaseCutoutOffset + PlugRim[LENGTH])
	left(Plug[OD]/4)
	resize(BaseCutout)
	yrot(90) zrot(180/8)
	cylinder(d=1,h=1,$fn=8,center=true);

	up(PlugRim[LENGTH])
	right(PlugRim[OD]/2 – 1.0)
	cube([2.0,1.0,1.0],center=true);

	for (i = [0:NumPins – 1])
	zrot(i*360/NumPins + 180/NumPins)
	down(Protrusion)
	right((Plug[OD] + Plug[ID])/4)
	zrot(180/6)
	cylinder(d=PinOD,h=2*PlugRim[LENGTH],$fn=6);


	for (k = [0:1]) // recesses in plug to capture base setscrews
	for (a = [0:1])
	up(PlugRim[LENGTH] + BaseScrewPositions[k][a])
	zrot(a*90)
	right(Plug[OD]/2)
	yrot(90) zrot(180/8)
	cylinder(d=BaseScrew[OD],h=2*BaseScrew[LENGTH],$fn=8,center=true);

	if (!PlugGlue)
	for (a = [0:1]) // inserts for angle block screws
	up(PlugRim[LENGTH]/2)
	zrot(a*90)
	yrot(90) zrot(180/8)
	cylinder(d=Insert[OD],h=2*PlugRim[OD],$fn=8,center=true);

	}
	}

	//———-
	// Block fitting against handlebar base with handlebar angle

	module AngleBlock() {

	difference() {
	hull() {
	up((TopOD/2)*sin(GripAngle))
	xrot(GripAngle)
	cylinder(d=TopOD,h=PlugRim[LENGTH],$fn=NumSides);
	for (a = [1:2:GripAngle+1])
	up((TopOD/2)*sin(a-1))
	hull() {
	xrot(a)
	cylinder(d=TopOD,h=0.1,$fn=NumSides);
	xrot(a-1)
	cylinder(d=TopOD,h=0.1,$fn=NumSides);
	}

	down(Grip[LENGTH] + MidLength)
	cylinder(d=(Grip[OD] + 2*WallThick),h=0.1,$fn=NumSides);
	}

	up((TopOD/2)*sin(GripAngle))
	xrot(GripAngle)
	down(SupportSag)
	cylinder(d=(PlugRim[OD] + HoleWindage),
	h=PlugRim[LENGTH] + SupportSag + Protrusion,
	$fn=NumSides);

	up((TopOD/2)*sin(GripAngle))
	sphere(d=PlugRim[ID],$fn=NumSides);

	cylinder(d=PlugRim[ID],h=(TopOD/2)*sin(GripAngle),$fn=NumSides);

	down(MidLength + Protrusion)
	cylinder(d=(Grip[ID] – 2.0),h=(MidLength + 2*Protrusion),$fn=NumSides);

	down(Grip[LENGTH] + MidLength + Protrusion)
	cylinder(d=(Grip[OD] + HoleWindage),h=(Grip[LENGTH] + Protrusion),$fn=NumSides);

	up((TopOD/2)*sin(GripAngle))
	xrot(GripAngle)
	up(PlugRim[LENGTH])
	right(PlugRim[OD]/2 + 0.9)
	cube([2.0,1.0,1.0],center=true);

	if (!PlugGlue) {
	for (a = [0:1])
	up((TopOD/2)*sin(GripAngle))
	xrot(GripAngle)
	up(PlugRim[LENGTH]/2)
	zrot(a*90)
	yrot(90) zrot(180/8)
	cylinder(d=Screw[OD],h=3*PlugRim[OD],$fn=8,center=true);
	for (a = [0:3])
	up((TopOD/2)*sin(GripAngle))
	xrot(GripAngle)
	up(PlugRim[LENGTH]/2)
	zrot(a*90)
	right(TopOD/2 – 2.0)
	yrot(90) zrot(180/8)
	cylinder(d=ScrewHeadOD,h=TopOD,$fn=8,center=false);
	}

	if (SquareNuts) {
	for (a = [0:1])
	for (k = [1,3])
	down(k*Grip[LENGTH]/4 + MidLength)
	zrot(a*90)
	right(BotOD/2)
	yrot(90) zrot(180/8)

	cylinder(d=SquareNut[ID],h=BotOD,$fn=8,center=true);
	for (a = [0:1])
	for (k = [1,3])
	down(k*Grip[LENGTH]/4 + MidLength)
	zrot(a*90)
	right(GripRadius + SquareNut[LENGTH]/2 – NutInset/2)
	yrot(90)
	cube([SquareNut[OD],SquareNut[OD],SquareNut[LENGTH] + NutInset],center=true);
	}
	else {
	for (a = [0:1])
	for (k = [1,3])
	down(k*Grip[LENGTH]/4 + MidLength)
	zrot(a*90)
	right(BotOD/2)
	yrot(90) zrot(180/8)
	cylinder(d=Insert[OD],h=BotOD,$fn=8,center=true);

	}
	}

	}

	//———-
	// Chip fitting against handlebar base matching top angle
	// Text will be invisible until sliced

	module GripCover(loc=LEFT,matl="Cover") {

	if (matl == "Text" \|\| matl == "All")
	color(LogoColor)
	down(matl == "All" ? 0.01 : 0.0)
	text3d(LogoText[loc == LEFT ? 0 : 1],LogoThick,LogoSize,LogoFont,
	orient=DOWN,anchor=TOP,atype="ycenter");

	if (matl == "Cover" \|\| matl == "All")
	difference() {
	intersection() {
	yrot(loc == RIGHT ? -CoverAngle : CoverAngle)
	cylinder(d=Plug[OD],h=(CoverThick[0] + CoverThick[1]),anchor=CENTER);
	cube(2*Plug[OD],anchor=BOTTOM);
	}
	text3d(LogoText[loc == LEFT ? 0 : 1],LogoThick,LogoSize,LogoFont,
	orient=DOWN,anchor=TOP,atype="ycenter");
	}

	}


	//———-
	// Build things

	if (Layout == "Cover") {
	GripCover(LEFT,Material);
	}

	if (Layout == "Covers") {
	left(Plug[OD]) GripCover(LEFT,"Cover");
	left(Plug[OD]) GripCover(LEFT,"Text");

	right(Plug[OD]) GripCover(RIGHT,"Cover");
	right(Plug[OD]) GripCover(RIGHT,"Text");
	}

	if (Layout == "Plug")
	BasePlug();

	if (Layout == "Block")
	AngleBlock();

	if (Layout == "Show") {

	up((TopOD/2)*sin(GripAngle) + Protrusion)
	xrot(GripAngle)
	up(Plug[LENGTH] + CoverThick[1] + Gap)
	yrot(180 + CoverAngle)
	GripCover(RIGHT,"All");

	up((TopOD/2)*sin(GripAngle) + Protrusion)
	xrot(GripAngle)
	up(Gap)
	color("Lime",0.75)
	BasePlug();
	render()
	difference() {
	AngleBlock();
	back(50) right(50)
	cube(100,center=true);
	}

	color("Silver",0.5)
	down(MidLength + Gap)
	tube(3*Grip[LENGTH],GripRadius,Grip[ID]/2,anchor=TOP);

	}

	if (Layout == "Build") {
	mirror_copy([1,0,0]) {
	right(BotOD) {
	up((TopOD/2)sin(GripAngle) + PlugRim[LENGTH]cos(GripAngle) + Protrusion)
	xrot(180 – GripAngle)
	AngleBlock();
	back(1.5*max(TopOD,BotOD))
	BasePlug();
	}
	}

	fwd(60) {
	left(Plug[OD]) GripCover(LEFT,"Cover");
	right(Plug[OD]) GripCover(RIGHT,"Cover");
	}

	fwd(60) {
	left(Plug[OD]) GripCover(LEFT,"Text");
	right(Plug[OD]) GripCover(RIGHT,"Text");
	}

	}

view raw Handlebar Grip Mount.scad hosted with ❤ by GitHub

2024-12-17

40.8	W
42.4
42.3
41.2
40.7
41.5	W avg
0.82	W std dev

Category: Software

Quick-n-Easy Window Shade End Cap

PrusaSlicer Scarf Joints

OMTech 60 W Laser: Manual Pulse Button

PrusaSlicer Flatpak: Adding an NFS Filesystem

HLP-200B Laser Power Meter: Holder / Stand

HQ Sixteen: Chin Light

HQ Sixteen: Grip Angle Caps