Category: Machine Shop

Mechanical widgetry

Laser Cutter: Rotary Stepper Driver

Having picked up a small rotary intended for Ortur diode laser machines during Black Friday, I knew using it with my OMTech 60 W CO₂ laser wasn’t going to be plug-n-play. The usual connection for a rotary in a CO₂ laser is directly into the stepper motor driver for the Y axis, so the stepper motor in the rotary must handle the same current as the Y axis motor. The OMTech laser has NEMA 23 steppers set for 3.5 A, which would quickly fry the NEMA 17 stepper in the Ortur rotary.

So the general idea was to run the rotary from another stepper driver set for an amp or so. A separate driver would also let me choose microstep settings more suitable for a rotary.

A simple SPDT switch enables the appropriate driver:

Laser Rotary Enable doodle

NB: Leaving the ENA pins of a stepper driver disconnected enables the motor output and passing current through them disables the motor; why that function was not labeled DISABLE remains a mystery.

So the switch looks bassakwards, but it connects the -ENA pin of the disabled driver to GND / common, with its +ENA pin tied to the supply.

Translating that doodle into hardware required drilling holes in what passes for the laser’s front panel:

Laser Rotary – control switch

The new driver stands up in bottom of the electronics bay:

Laser Rotary – R driver – detail

The loose wire over on the left is a remnant of the discovery that the KT332N controller’s General output bits do not behave as expected. While you (well, I) can set their state through the display’s MENU → DIAGNOSES screen, the controller unilaterally slams them low = active while running a job. To be fair, the manual does say “General output, reserved”, but I had to find out the hard way.

The +ENA terminal comes from the +5V supply, along with the other + terminals. The -ENA terminal goes off to the switch, along with two wires from the existing Y axis stepper driver:

Laser Rotary – Y driver wiring

The 1.8 kΩ resistor sticks out of a ferrule doubled up in the 24V terminal feeding the driver and connects to a wire into the +ENA terminal. Two wires from the switch connect to the -ENA and GND terminals, join the -ENA wire from the rotary driver, and crawl through the machine to the front panel.

The new power supply on the far right completes the electronics bay installation:

Laser Rotary – electronics bay

Obviously, the wiring situation is completely out of control.

Up top, though, it looks like it grew there:

Laser Rotary – on platform

Now, to figure out the settings …

2025-12-18

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 bolts holding the panel to the machine frame
Ease it forward a bit
Tuck 6 mm acrylic scraps behind all four corners
Snug the bolts 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.

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

Laser Cutter: OEM 24 V Power Supply Annoyances
In the process of replacing the laser cutter’s OEM 24 V 6 A power supply with a 15 A supply, one of the two screws holding it in place remained stuck in the underlying sheet metal plate:

Laser OEM 24V Power Suppy – installed

You can’t see either of the screws from that position, but they’re in the upper-left and lower-right corners. The offending screw is, of course, on the top, tucked between the top of the supply and the wire raceway. The bottom screw came out easily and I could maneuver the supply out of the way.

Vigorous persuasion involving a bent-nose pliers and muttering got the screw out and revealed the problem:

Laser OEM 24V Power Suppy – stripped screw

The reason why the screwdriver didn’t get much traction in the head also became obvious:

Laser OEM 24V Power Suppy – goobered screw head

Folks on the LightBurn forum seem astonished when they discover their fresh-from-the-factory has loose screws, missing screws, and occasionally the wrong screws.

I always wondered where the switch pointed to by the conspicuous label might be:

Laser OEM 24V Power Suppy – voltage label

Unlike most supplies, it’s inside the case:

Laser OEM 24V Power Suppy – voltage switch

After you spot it, you can also find it just below the tip of the arrow in the previous picture. I suppose putting it inside the case prevents it from being inadvertently flipped, but somebody had to dismantle All. The. Supplies. to flip that switch for the USA-ian market.

The dataplate also became visible:

Laser OEM 24V Power Suppy – dataplate

You’ll recall the 5 V 2 A output was dedicated to the red-dot pointer drawing about 20 mA.

In contrast, the 24 V 6 A output handled:
- X axis stepper driver: 3.5 A peak
- Y axis stepper driver: 3.5 A peak
- U axis stepper driver: 5.1 A peak
- KT332N controller &c: 1 or 2 A
- Gantry LED strip: 0.25 A
The stepper drivers are set to drop the motor current by half when they’re idle, which means their load would be only around 6 A. That’s as delivered to the motor windings, with the power supply’s average current being lower by roughly the ratio between the motor’s rated voltage and the power supply voltage. The instantaneous peak current, however, is the sum of all those currents.

At some point I must measure all that, but for now I want to shoehorn a bigger supply in there to take care of the additional load of the rotary stepper driver, plus the existing platform lighting and improved electronics bay blower.
2025-12-15
Dryer Vent Filter Snout: More Warping

I have unfairly maligned the TPU snout, because the PETG snout failed the same way:

Clothes Dryer Vent Filter Snout – warped PETG

Seen with the shock cord in place, it’s obvious that combining moderately high temperature with steady compression sufficed to bend the PETG enough to pop those tabs loose from the vent.

So the OpenSCAD model now produces a stiffening ring to be laser-cut from acrylic:

Clothes Dryer Vent Filter Snout – OpenSCAD stiffener

The whole snout builds as a single unit in the obvious orientation:

Clothes Dryer Vent Filter Snout – V2 – slicer

Because the part of the snout with the tabs is 7 mm tall, I glued a 4 mm acrylic ring to a 3 mm ring, with both of them glued to the snout:

Clothes Dryer Vent Filter Snout – acrylic gluing

That’s “natural” PETG, which I expected to be somewhat more transparent, but it’s definitely not a dealbreaker.

Mary will sew up another cheesecloth filter and we’ll see what happens to this setup.

As the saying goes, “Experience is what you get when you don’t get what you want.”

Fortunately, living in the future makes it easy to iterate on the design & implementation until experience produces what should have been obvious at the start.

2025-12-11
Bob Yak Trailer: Triple-New Grenade Pin Straps

It turned out those window screen splines lasted a dozen years until this happened:

Bob YAK trailer – splitting screen spline

Some rummaging in the Big Box o’ String produced the spool of 1000 pound test Kevlar cord most recently applied to the seat back on Mary’s bike, so this happened:

Bob YAK trailer – Kevlar cords

Having re-confirmed that frayed Kevlar cannot be melted into a blob, another UV-stabilized cable tie at each end will control those tufts.

Those cords should last forever …

2025-12-10
OMTech 60 W Laser: Revised Red-Dot Pointer Power
The OMTech 60 W laser has a 24 V + 5 V power supply for the stepper motors and, I had always assumed, the feeble LED strip light on the gantry:

OMTech 60W laser – OEM lighting

The stepper motor driver settings, plus a few amps for the controller and suchlike, added up to something over 12 A, far more than the 24 V supply’s 6 A spec should produce. When I added the COB strip lights around the platform, I dropped a 24 V wall wart into the electronics bay to avoid abusing that poor supply:

OMTech 60W laser – COB LED strips

For reasons to be described later, it’s now time to upgrade that 24 V power supply to a 15 A supply that’s been on the shelf for far too long. However, it does not have a 5 V output, so it’s also time to figure out how much 5 V power the laser really needs.

A quick measurement suggested the 5 V output delivered 20 mA to something. After convincing myself the multimeter was working and that the gantry LED strip was still lit, I finally tracked the wire pair to the red-dot pointer:

OMTech red dot pointer – polarizing filter installed

Yeah, a whole dual-output power supply for one red-dot laser module.

Conveniently, the KT332N controller has several 5 V outputs and the LIMIT terminal block even has a GND terminal on the other end:

KT332N Limit Terminals – OEM

Prying off the hot melt glue, extracting the red-dot pointer wiring from the raceway, crimping ferrules on a couple of jumpers, and deploying a pair of Wago connectors:

KT332N Limit Terminals – red dot wiring

I am still not accustomed to the color code:
- Black = signal
- Brown = power
- Blue = GND
But it’s like that and that’s the way it is.

The red dot lit right up, the gantry LED strip obviously uses 24 V power, and I must shoehorn a slightly larger 24 V supply into the space currently occupied by the old supply.
2025-12-09
Smashed Glass Coaster: Rivers of Crack

Looking at that big smashed-glass coaster from a different angle showed interesting patterns:

Printed Fragment Coaster – 165mm – long cracks

Although the larger fragments were still holding together when I laid them in their recesses, they apparently consist of several sub-fragments with larger continuous cracks letting the epoxy flow / ooze inside.

Now that I know what to look for, the original picture also shows them, albeit less distinctly:

Printed Fragment Coaster 165mm – overview

They’re not obvious in the scanned image of the fragments, although I could convince myself I see some:

Fragments 165mm square – scan sample

The many smaller fragments I’ve been turning into coasters probably separated from similar large chunks along such cracks, which is why I’ve never seen rivers of crack before.

Apologies if you arrived here expecting a tirade concerning the drug trade … :grin:

2025-12-08