MK4 – The Smell of Molten Projects in the Morning

Ortur YRC-1: Autofocus Pad

Ruida laser controllers do not allow the platform to rise above the U=0 origin set by the autofocus pen = switch. While this isn’t a problem for flat surfaces, focusing on the exact top of a horizontal cylinder, particularly a small rod, may be overly difficult.

So a focusing pad seems like a Good Idea™:

Ortur Rotary Focus Pad - focus pen positioning — Ortur Rotary Focus Pad – focus pen positioning

The general idea:

Align a flat horizontal surface with the rotary chuck’s axis
Do the autofocus operation with a well-defined landing zone under the pen
The Focus Distance puts the laser head at the proper height for a focused spot on the pad
Jogging the head upward (= platform downward) by the workpiece radius puts the focused spot exactly at the right height
Remove the focus pad
Install the workpiece
Fire The Laser

The solid model:

Ortur Rotary Focus Pad - solid model — Ortur Rotary Focus Pad – solid model

Features of note:

The chuck jaws fit into the recesses on the left end for a firm grip with good alignment
The lengthwise notch lies on the rotary axis parallel to the laser’s X axis
The crosswise notch is juuust rightward of the chuck jaws, marking the leftmost end of whatever you’re engraving

Because I added a home switch to the Ortur YRC-1 case, Jaw 1 automagically ends up on top after homing, thus automagically making the focus pad horizontal. Getting that right required fine-tuning the rotary’s home switch trip point, which turned out to be easier to do using the Home Offset configuration value after I replaced the cam I thought would work:

Ortur Chuck Rotary home switch - pulley cam — Ortur Chuck Rotary home switch – pulley cam

Instead, a simple M4 setscrew (standing proud of the pulley surface in one of the tapped holes for the real setscrew securing the pulley to the shaft) trips the switch much more repeatably :

Ortur Rotary Focus Pad - home trip setscrew — Ortur Rotary Focus Pad – home trip setscrew

The setscrew on the right sits flush with the surface to prevent the switch roller from falling into the hole. The real setscrew underneath it locks the pulley to the shaft’s flat.

With that in place, a quick binary search settled on a Y axis Home Offset = 1.75 mm to put the pad level with the top of the rotary’s case, which is Level Enough™ due to my tweaking the machine’s foot elevations after jacking the whole machine up on risers:

Ortur Rotary Focus Pad - home offset adjustment — Ortur Rotary Focus Pad – home offset adjustment

The Home Offset value:

The speed and acceleration values are much lower than used with the linear Y axis, because apparently Ruida computes the corresponding step values using the workpiece diameter in the Rotary section. Small diameters produce impossibly fast motions, which suggests they expect you to set the optimum values based on back-calculations from the object diameter; ain’t nobody got time for that.

Anyhow.

After autofocusing, the red-dot pointer now indicates the laser spot position, so jog the X axis and drag the gantry to put the spot on the axis mark:

Ortur Rotary Focus Pad - gantry positioning — Ortur Rotary Focus Pad – gantry positioning

The orange rim on the red-dot pointer cuts down the beam intensity to make a smaller dot and provides easier position tweaks.

Then jog the X axis to put the dot at the transverse mark just beyond the chuck jaws:

Ortur Rotary Focus Pad - red dot at origin — Ortur Rotary Focus Pad – red dot at origin

Hit the Ruida Origin button to set that as the user origin, so you can reference the LightBurn design to the hardware position.

Move the platform down by the workpiece radius, jog the nozzle along the X axis to get it out of the way, remove the focus pad, install the workpiece, and you’re good to go. The checklist visible beyond the bubble level shows it’s not quite that simple, but we’re getting there.

The OpenSCAD source code as a GitHub Gist:

	// Ortur Rotary Focus Pad
	// Ed Nisley – KE4ZNU
	// 2026-01-04

	include <BOSL2/std.scad>

	Style = "Show"; // [Build,Show]

	/* [Hidden] */


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

	HoleWindage = 0.2;
	Protrusion = 0.1;

	NumSides = 834;
	$fn=NumSides;

	// Magic numbers to fit Ortur jaws

	PadOAL = 60.0; // clear assist air fitting
	PadIR = 7.0; // jaw tip 35 mm above this point
	JawOAL = 14.0; // clear large jaws

	Reticle = [0.7,0.7,PadOAL];
	OriginOffset = 28.0; // X origin from chuck plate


	//—–
	// Pad to give autofocus probe a flat landing zone

	module FocusPad() {

	difference() {
	linear_extrude(PadOAL)
	hexagon(ir=PadIR,realign=true,rounding=3.0);

	up(JawOAL) {
	cube(PadOAL,anchor=BOTTOM+LEFT);
	cube(Reticle,spin=45,anchor=BOTTOM);
	}
	up(OriginOffset)
	cube(Reticle,spin=45,orient=FRONT,anchor=CENTER);

	for (a=[0:120:360])
	rotate(a)
	down(Protrusion)
	linear_extrude(JawOAL + 2*Protrusion)
	right(PadIR + 15 – 2) // eyeball fit
	hexagon(or=15,rounding=0.5);
	}

	}

	//—–
	// Build things

	if (Style == "Show")
	yrot(90)
	zrot(180)
	FocusPad();

	if (Style == "Build")
	FocusPad();

view raw Ortur Rotary Focus Pad.scad hosted with ❤ by GitHub

2026-01-08

Silica Gel Beads: Regeneration Damage

The silica gel beads I’ve been using in the PolyDryer boxes start out a uniform yellow / light brown:

Polydryer Box desiccant tray - top view — Polydryer Box desiccant tray – top view

The humidity indicating chemical seems to be methyl violet, described as changing from yellow to green when saturated, which has never happened here. For example, these beads, retrieved from random corners of the workbench, have been sitting in 40-ish %RH basement air for weeks:

Silica gel beads - 36pctRH ambient — Silica gel beads – 36pctRH ambient

The fragment just left of center looks greenish, but the rest are, at best, various shades of brown. This may be due to the (relatively) low humidity in the basement, but putting them under a damp sponge for a few hours didn’t change their color.

The most recent regeneration session started with an open cast-iron pan on an induction cooktop:

Silica gel beads - drying — Silica gel beads – drying

The variety of browns comes from various amounts of adsorbed water in the PolyDryer boxes, but AFAICT there really isn’t much correlation between the humidity level and the amount of adsorbed water.

The drying process went like this:

650 g at start
50% power for 2 hr → 200 °F
Covered the pan & turned it off overnight
623 g at start
50% power for 2 hr → 220 °F
612 g
50% power for 1 hr → 236 °F
610 g
30% power for 30 min → 205 °F
35% power for 30 min → 200 °F
609 g

So about four hours at 50% power would get all but the laser few grams of water out of the silica gel.

After all that, the beads looked about the same in a white bowl for cooling:

Silica gel beads - damaged indicator dye — Silica gel beads – damaged indicator dye

Each regeneration cycle leaves more dark brown beads in the mix, which may be due to poor temperature control, and they do not return to their original yellow / pale brown shade.

Apparently cooking silica gel beads over 120 °C = 250 °F (various sources give various temperatures) can damage their structure or the methyl violet indicator; for sure some of those beads have been abused.

Unsurprisingly, the bead temperature rises as they dry out. Although the induction cooktop has a temperature control, we’ve found the setting doesn’t match the pan temperature and the overall control is poor. I could set the gas oven to 200 °F, but I’m certain it doesn’t control the temperature all that closely, either.

The original jug held 2 pounds = 907 g of beads. Add the 609 g from this session to the 350 g of allegedly dry beads in seven of the PolyDryer boxes: my regeneration hand is weak.

2026-01-07

PolyDryer Humidity: December

The measurements:

	2025-12-29
Filament	%RH	Weight – g	Wt gain – g	Gain %
PETG White	18	53.8	3.8	7.6%
PETG Black	18	53.8	3.8	7.6%
PETG Orange	22	52.3	2.3	4.6%
PETG Natural	22	53.4	3.4	6.8%
PETG-CF Blue	18	54.1	4.1	8.2%
PETG-CF Gray	23	54.1	4.1	8.2%
PETG-CF Black	18	53.8	3.8	7.6%
PETG Blue	10	52.9	2.9	5.8%
TPU Clear	18	54.4	4.4	8.8%
TPU Black	18	55.1	5.1	10.2%

I used to think there was some correlation between the indicated humidity and the amount of water adsorbed by the silica gel, with the humidity rising as the gel absorbed more water. That is obviously not the case.

AFAICT, I’d been reading the chart wrong:

Instead of the adsorption being a function of the equilibrium humidity, it’s the other way around. With the humidity held constant (by adding water vapor), the silica gel will adsorb thus-and-so percentage of its weight and equilibrate at that humidity. If the filament was an infinite reservoir of dampness, then the equilibrium humidity would indicate how much the silica gel had coped with.

At least I think that’s how it goes. I have been wrong before.

Anyhow, IMO the right way to proceed is to just replace the silica gel every month and be done with it.

Also true: the humidity meters aren’t particularly accurate at the low humidity values in those boxes.

2026-01-06

Ortur YRC-1: Conical Tailstock Centers

A conical (a.k.a. bullnose) center in the tailstock simplifies supporting cylindrical objects:

Ortur Chuck Rotary conical center - installed — Ortur Chuck Rotary conical center – installed

The spring-loaded tailstock bearing has a 5 mm bore. The bullnose rests against a small spacer on its 5 mm shaft to hold it away from the bearing’s mounting screws with some bearing spring compression. I turned the spacer from aluminum rod because lathe work is satisfying, but a printed spacer would work fine.

The bullnose is a cone with steps encouraging the cylinder to sit properly:

Ortur Rotary Conical Center - 10-50mm — Ortur Rotary Conical Center – 10-50mm

With both ends centered, the cylinder sits concentric with the chuck axis:

Ortur Chuck Rotary home switch - jaw position — Ortur Chuck Rotary home switch – jaw position

The chuck grabs the OD and the bullnose supports the ID, so removing crud from both ends is in order.

The bullnose won’t work for a solid rod, so a negative cone = cup center may come in handy:

Ortur Chuck Rotary cup center - installed — Ortur Chuck Rotary cup center – installed

Stipulated: A CO₂ laser will bounce right off a solid aluminum rod. Imagine I chucked up a wood dowel, OK?

A cup center is what remains afteryoinking a bullnose out of a cylinder:

Ortur Rotary Conical Centers - cup — Ortur Rotary Conical Centers – cup

Looks like I did exactly that:

Somewhat surprisingly, the two parts nest perfectly:

Ortur Chuck Rotary conical centers - nested — Ortur Chuck Rotary conical centers – nested

That’s without the shaft installed on the cup, so they won’t sit quite so neatly on the shelf.

Aligning the rotary axis along the laser’s X axis and setting the focus requires attention to detail, but a decent tailstock center makes that effort meaningful.

The OpenSCAD code as a GitHub Gist:

	// Ortur Rotary Conical centers
	// Ed Nisley – KE4ZNU
	// 2025-12-27

	include <BOSL2/std.scad>

	Style = "Bullnose"; // [Build,Cone,Bullnose,Cup,Cone]

	MinDia = 10.0;
	MaxDia = 50.0;

	/* [Hidden] */

	LayerThick = 0.2; // should match slicer thickness

	Ramp = 1.0;

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

	HoleWindage = 0.2;
	Protrusion = 0.1;

	NumSides = 834;
	$fn=NumSides;

	Gap = 5.0;

	WallThick = 2.0;

	TailBearing = [5.0,7.0,10.0]; // tailstock shaft, LENGTH = insert depth

	StepHeight = 2*LayerThick;

	NumSteps = (((MaxDia – MinDia)/2) / Ramp);
	ConeOAH = NumSteps * (Ramp + StepHeight);

	//—–
	// Bullnose shape

	module Bullnose() {

	difference() {
	union()
	for (i = [0:NumSteps – 1])
	up(i*(Ramp + StepHeight)) hull()
	cyl(StepHeight + Protrusion,r=(MaxDia/2 – i*Ramp),anchor=BOTTOM) position(TOP)
	cyl(Ramp,r1=(MaxDia/2 – iRamp),r2=(MaxDia/2 – (i+1)Ramp),anchor=BOTTOM);
	}


	}

	module Cone() {

	difference() {
	Bullnose();
	down(Protrusion)
	cyl(TailBearing[LENGTH] + Protrusion,d=TailBearing[ID],circum=true,anchor=BOTTOM);
	}

	}

	module Cup() {

	difference() {
	cyl(ConeOAH + TailBearing[LENGTH],d=MaxDia + 2*WallThick,anchor=BOTTOM);
	up(ConeOAH + TailBearing[LENGTH] + Protrusion)
	yrot(180)
	Bullnose();
	down(Protrusion)
	cyl(TailBearing[LENGTH] + 2*Protrusion,d=TailBearing[ID],circum=true,anchor=BOTTOM);
	}


	}


	//—–
	// Build things

	if (Style == "Bullnose")
	Bullnose();

	if (Style == "Cone")
	Cone();

	if (Style == "Cup")
	Cup();

	if (Style == "Build") {
	right(MaxDia/2 + Gap)
	Cone();
	left(MaxDia/2 + WallThick + Gap)
	Cup();
	}

view raw Ortur Rotary Conical Centers.scad hosted with ❤ by GitHub

2025-12-30

Ortur YRC-1: Adding a Home Switch

Stipulated: A chuck rotary doesn’t need a home switch.

With that in mind, a home switch seemed like it might come in handy and this is the simplest workable design:

Ortur Chuck Rotary home switch - installed — Ortur Chuck Rotary home switch – installed

The cover mimics the size & shape of the Ortur cover, minus the stylin’ rounding & chamfering along the edges:

Ortur Rotary Belt Cover - exterior - solid model — Ortur Rotary Belt Cover – exterior – solid model

It has a certain Cybertruck aspect, doesn’t it?

Two beads of hot melt glue hold the switch flush along the cover’s inside surface:

Ortur Chuck Rotary home switch - case exterior — Ortur Chuck Rotary home switch – case exterior

One might argue for a tidy cover over those terminals.

While contemplating the layout by holding the switch here & there, seeing the switch roller neatly centered on the pulley hub told me the Lords of Cosmic Jest favored this plan:

Ortur Chuck Rotary home switch - case interior — Ortur Chuck Rotary home switch – case interior

A simple cam lifts the roller:

That’s obviously laser-cut acrylic sitting on double-sided tape. Some finicky repositioning put the #1 chuck jaw on top after homing:

A more permanent adhesive under the cam may be in order.

Update: The switch triggers more reliably with a simple setscrew standing proud of the pulley hub:

Wiring the normally open switch contacts in parallel with the existing Y axis home switch lets both the gantry and the rotary trigger the controller. The front-panel switch ensures only one of those two can move:

Laser Rotary - control switch — Laser Rotary – control switch

With all that in place and the switch flipped, the chuck rotates happily and homes properly with the controller in normal linear mode.

Spoiler: A Ruida-ish KT332N controller ignores the Y-axis Home enable setting with Rotary mode enabled, because everybody knows a rotary has no need for a home switch.

The OpenSCAD code as a GitHub Gist:

	// Ortur Rotary belt cover
	// Ed Nisley – KE4ZNU
	// 2025-12-23

	include <BOSL2/std.scad>

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

	/* [Hidden] */

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

	HoleWindage = 0.2;
	Protrusion = 0.1;

	NumSides = 234;
	$fn=NumSides;

	Gap = 5.0;

	WallThick = 1.6; // OEM wall

	CoverOA = [81.5,50.5,23.0]; // open side down
	CoverRadius = 4.0;
	CoverTrimZ = 6.0;
	CoverTrimAngle = 45;

	BreakX = (CoverOA.z – CoverTrimZ)/tan(CoverTrimAngle);

	ScrewOC = [51.0,38.0];
	ScrewHoleID = 3.5;
	ScrewHeadRecess = [ScrewHoleID,7.0,1.8];
	ScrewOffset = 8.0; // cover edge to hole centerline

	SwitchOA = [21.0,20.0,6.5]; // X = body + roller, excludes terminals
	SwitchOffset = [0,0,17.0]; // nominal end = roller at centerline



	//—–
	// Overall cover shape

	module CoverBlock() {

	cuboid([CoverOA.x,CoverOA.y,CoverTrimZ],anchor=BOTTOM) position(TOP+LEFT)
	prismoid(size1=[CoverOA.x,CoverOA.y],size2=[CoverOA.x – BreakX,CoverOA.y],
	height=CoverOA.z – CoverTrimZ,shift=[-BreakX/2,0],anchor=BOTTOM+LEFT);
	}

	// Cover shell

	module CoverShell() {

	difference() {
	CoverBlock();
	down(Protrusion)
	resize(CoverOA – [2WallThick,2WallThick,WallThick – Protrusion])
	CoverBlock();
	}
	}

	// The complete cover

	module Cover() {

	difference() {
	union() {
	CoverShell();
	left((CoverOA.x – ScrewOC.x)/2 – ScrewOffset)
	for (i = [-1,1], j=[-1,1])
	translate([iScrewOC.x/2,jScrewOC.y/2,0])
	cyl(CoverOA.z,d=ScrewHoleID + 2*WallThick,anchor=BOTTOM);
	}
	left((CoverOA.x – ScrewOC.x)/2 – ScrewOffset) down(Protrusion)
	for (i = [-1,1], j=[-1,1])
	translate([iScrewOC.x/2,jScrewOC.y/2,0]) {
	cyl(CoverOA.z + 2*Protrusion,d=ScrewHoleID + HoleWindage,anchor=BOTTOM);
	up(CoverOA.z – ScrewHeadRecess[LENGTH])
	cyl(ScrewHeadRecess[LENGTH] + 2*Protrusion,
	d1=ScrewHeadRecess[ID] + HoleWindage,d2=ScrewHeadRecess[OD] + HoleWindage,
	anchor=BOTTOM);

	}
	translate(SwitchOffset) left(CoverOA.x/2 – WallThick – Protrusion)
	cuboid(SwitchOA,anchor=RIGHT+FWD);
	}

	}


	//—–
	// Build things


	if (Layout == "Block") {
	CoverBlock();
	}

	if (Layout == "Shell") {
	CoverShell();
	}

	if (Layout == "Show") {
	Cover();
	}

	if (Layout == "Build") {
	up(CoverOA.z)
	xrot(180)
	Cover();

	}

view raw Ortur Rotary Belt Cover.scad hosted with ❤ by GitHub

2025-12-29

Garden Step2 Seat: Hinge Replacement

As fate would have it, the Step2 rolling garden seat took an untimely fall while standing in the garage and broke both its hinges:

Garden Step2 Seat - broken hinge — Garden Step2 Seat – broken hinge

It’s been out in the garden for maybe six years, so those chunks of plastic are fully depreciated.

Two hours after loading the solid model into PrusaSlicer:

Garden Step2 Seat - new hinges installed — Garden Step2 Seat – new hinges installed

The SiLite tray is well-weathered, but remains structurally sound: still ready for service in the D-Hall breakfast line on the morning after the Apocalypse.

Living in the future works out pretty well.

2025-12-22

Laser Cutter: New 24 V Power Supply

Unlike the OEM 24 V supply in the laser, the “new” supply from my heap does not have mounting flanges; it’s intended to be attached to a mounting plate from the back side. It turns out the laser does have a mounting plate with All The Things screwed onto it, but there is no way I am going to disconnect all the wiring just to drill four more holes in that plate.

So I made a pair of brackets to screw into the back of the supply and then into suitable holes in the mounting plate:

Laser 24V Power Supply Mount - solid model — Laser 24V Power Supply Mount – solid model

Which look like this in real life:

Laser 24V Power Suppy - mounts installed — Laser 24V Power Suppy – mounts installed

Those M4 rivnuts just beg for 6 mm holes in the mounting plate.

However, it turns out that their unsquished length exceeds the distance behind the panel, which means there’s no way to install them flush to the panel with the proper backside squish.

So:

Loosen the four nuts holding the panel to the bolts welded to the machine frame
Ease it forward a bit
Tuck 6 mm acrylic scraps behind all four corners
Snug the nuts again to hold the plate against the acrylic with plenty of room behind it

The OpenSCAD code generates a simpleminded drill template:

Laser 24V Power Suppy - drill template — Laser 24V Power Suppy – drill template

Press a scrap of rubber firmly against the plate to dampen vibrations and thwack each hole with an automatic center punch set to stun. Deploy a succession of drills up through 6 mm, catching most of the swarf in tape strips:

Laser 24V Power Suppy - drill chip catchers — Laser 24V Power Suppy – drill chip catchers

Squish the rivnuts in place:

Laser 24V Power Suppy - rivnuts in place — Laser 24V Power Suppy – rivnuts in place

The small, vaguely tapped hole on the lower right was the “good” screw for the OEM power supply; the “bad” screw hole is invisible to the upper left, just under the raceway.

Remove the plastic spacers, snug the nuts holding the plate again, install the power supply, and it looks like it grew there:

Laser 24V Power Suppy - installed — Laser 24V Power Suppy – installed

The wires and Wago connectors scrunched underneath aren’t anything to be proud of, but longer wires didn’t seem likely to improve the outcome.

The OpenSCAD source code as a GitHub Gist:

	// Mount for 24 V laser power supply
	// Ed Nisley – KE4ZNU
	// 2025-12-07

	include <BOSL2/std.scad>

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

	/* [Hidden] */

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

	HoleWindage = 0.2;
	Protrusion = 0.1;

	NumSides = 234;
	$fn=NumSides;

	Gap = 5.0;

	Rivnut = [4.0,6.0,9.0]; // body + head OD
	RivnutHead = [6.0,10.0,1.0]; // flat head

	WallThick = 6.0; // a bit more than half rivnut head OD

	SupplyCase = [50.0,215.0,112.0]; // power supply case size
	SupplyOC = [25.0,150.0,0]; // power supply mounting screw centers
	SupplyOffset = -1.0; // the screws are not centered on the case!
	SupplyScrew = [4.0,9.0,4.0]; // … LENGTH outside supply case

	MountOC = SupplyCase.x + 2*WallThick;
	MountScrewLength = 8.0; // … head-to-baseplate
	MountRadius = 0.5;

	BlockOA = [MountOC + 2WallThick, 2WallThick, MountScrewLength];

	GuideOD = 2.0;

	//—–
	// Single mounting block

	module MountBlock() {

	difference() {
	cuboid(BlockOA,chamfer=MountRadius,except=BOTTOM,anchor=BOTTOM);

	for (i = [-1,1]) {
	right(i*MountOC/2) {
	cyl(2*RivnutHead[LENGTH],d=RivnutHead[OD],circum=true,anchor=CENTER);
	cyl(2*BlockOA.z,d=Rivnut[ID] + HoleWindage,circum=true,anchor=BOTTOM);
	}
	right(i*SupplyOC.x/2 + SupplyOffset) {
	down(SupplyScrew[LENGTH])
	cyl(BlockOA.z,d=SupplyScrew[OD] + HoleWindage,circum=true,anchor=BOTTOM);
	cyl(2*BlockOA.z,d=SupplyScrew[ID] + HoleWindage,circum=true,anchor=BOTTOM);
	}
	}

	}
	}


	//—–
	// Guide holes in a 2D layout

	module DrillGuide() {
	difference() {
	square([BlockOA.x,SupplyOC.y + BlockOA.y],center=true);

	for (j=[-1,1])
	fwd(j*SupplyOC.y/2)
	for (i = [-1,1]) {
	right(i*MountOC/2) {
	circle(d=GuideOD);
	}
	}
	}
	}


	//—–
	// Build things

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

	if (Layout == "Guide")
	DrillGuide();

	if (Layout == "Show") {
	for (j=[-1,1])
	fwd(j*SupplyOC.y/2)
	MountBlock();
	color("Gray",0.5)
	up(BlockOA.z)
	cuboid(SupplyCase,anchor=BOTTOM);
	}

	if (Layout == "Build") {
	for (j=[-1,1])
	fwd(j*(BlockOA.y/2 + Gap/2))
	up(BlockOA.z) zflip()
	MountBlock();
	}

view raw Laser 24V Power Supply Mount.scad hosted with ❤ by GitHub

2025-12-17