Tag: Laser Cutter

OMTech Laser: Focus Pen Pretravel Tweakage & Autofocus Calibration
The focus “pen” = switch on the OMTech laser stuck out far below the nozzle:

Laser cut plywood flames – C

The nozzle is 18.5 (-ish) mm above the surface with the laser beam focused to a tight spot. The brass (-ish) tip of the pen flew about 5 mm above the material, requiring considerable attention to the placement of magnets, clamps, and similar accoutrements around the material on the platform.

Having dismantled the pen while replacing its wiring, this seemed like a good time to figure out how to get more clearance under its tip.

Removing the pen nose shows the tip on its 3 mm screw inside the spring pushing the tip downward:

OMTech focus pen – soft spring – installed

I replaced the original spring (on the bottom) with a softer spring, mostly because the tip exerted what seemed like entirely too much force on the material. That makes no difference for acrylic & plywood, but anything squishier required deploying the focus gauge after I remembered the problem.

The other end of the screw is impossible to photograph in situ, but the tapered head seats in a recess leaving several millimeters of air below the proximity sensor. I made a little steel slug to reduce the pretravel by filling that gap:

OMTech focus pen – pretravel filler

The spigot on the slug (turned from 7/32 inch steel rod) aligns it with the screw head, with high-viscosity cyanoacrylate adhesive holding it in place:

OMTech focus pen – pretravel filler – installed

The surface finish of my slug matches their tapering, so I figure it’s about right.

A setscrew near the top of the pen clamps the proximity sensor with a few millimeters of adjustment:

OMTech laser focus pen – detail

The slug reduces the pretravel to nearly zero with the sensor at the bottom of its range.

The brass tip had been twisted onto the screw as far as it would go, so I cut a few millimeters off the screw to put the tip closer to the pen nose:

OMTech focus pen – minimal stickout

Even with reduced pretravel, the tip nearly vanished into the pen body before tripping the sensor, so I unscrewed it two turns = 1.4 mm.

With the pen back in the machine and plugged in, measure the switch travel with a step gauge:

OMTech focus pen – revised stickout

Protip: Measure the as-cut height of those steps, then either shim the bottom of the gauge with tape of a suitable thickness or add that much to the layout and cut another set.

With a good step gauge in hand:
- Slide it underneath to just touch the tip
- Note the measurement = A
- Slide it further until the switch trips (red LED on)
- Note the measurement = B
Figure B-A, round up to the next millimeter, then set that value as the Home Offset for whatever axis moves the platform. My tweaked pen had 2.5 mm of travel, so I used 3.0 mm:

Settings – Home Offset

Adjust the pen position to put the tip more than the Home Offset below the nozzle (I picked 5 mm) to ensure the switch will trip before the nozzle contacts the platform, then do an Autofocus.

Measure the distance from the nozzle to the platform (mine was 5.5 mm), subtract that from 18.5 mm (the known focused distance for my laser head, as above), and set that as the Focus Distance:

Settings – Focus Distance

Another Autofocus should then put the nozzle exactly 18.5 mm (or whatever your machine needs) off the platform / material.

This shows the pen now flies 5 mm below the nozzle:

OMTech focus pen – normal vs nozzle

The step gauge shows it’s 13.5 mm above the platform, much better than the previous 5 mm.

The switch trips juuuust before the nozzle hits the material:

OMTech focus pen – tripped vs nozzle

I should lower the pen a millimeter, but that’s in the nature of fine tuning.

Happy Dance!
2025-12-24
OMTech Laser: Focus Pen Wiring Repair
This happened while focusing the laser before cutting the cardboard fixture for the chuck rotary:

OMTech focus pen – failed operation

The autofocus “pen” = switch did not operate when the rising platform pushed the cardboard against its tip, so the controller continued raising the platform. Seconds later, the platform rammed the cardboard against the laser head and I slapped the Big Red Button.

Those indentations match the focus pen and the nozzle:

OMTech laser focus pen-switch

Yeah, the platform shoved that pen straight up through its clamp until both punched through the cardboard.

The pen has a red LED (barely visible through the opening around the cable when you’re looking down into it) that did not light up when I manually triggered the switch: either the switch was dead or it wasn’t getting 24 V power.

Having spent considerable time diagnosing similar problems on the LightBurn forum, I was pretty sure the PVC-insulated wire connecting the pen to the controller had failed somewhere in the drag chain.

Update Yup, the 24 V wire was broken:

OMTech focus pen – failed 24V wire

Another discussion there showed how to dismantle the pen, so I (turned off the power and) cut the cable a few inches from the top of the pen body.

The pen body has three parts screwed together with generous application of threadlock. After demonstrating I lack enough grip strength to break the bonds, I deployed a pair of lathe chucks designed for a death grip on cylindrical objects:

OMTech focus pen – double chuck setup

The tip came off readily enough:

OMTech focus pen – nose unscrewed

The upper joint was more reluctant, to the extent I needed witness marks to show progress:

OMTech focus pen – unscrewing witness marks

Dripping Kroil into the slightly loosened joint while twisting it back and forth eventually separated the parts:

OMTech focus pen – body unscrewed

I persuaded the last chunks of threadlock out with a stout pin (in a pin vise), eventually letting me screw the pen body together without a struggle.

Contrary to what I originally thought, the switch is a proximity sensor triggered by the reshaped head of an M3 socket-head screw also holding the brass-colored tip. Wiring it to a bench power supply verified proper operation, with the open-collector (actually, open-drain) output going low with any ferrous metal closer than about 3 mm to the sensor tip.

Which put the fault somewhere along the wiring from the controller through both drag chains to the pen, as expected.

Unlinking the X axis drag chain involved a pair of small screwdrivers prying the side plates off their pivots in the next link:

OMTech focus pen – drag chain unlinked

The slightly enlarged opening let me pull enough of the cable through to verify I needed more elbow room, so I dismounted the entire drag chain:

OMTech focus pen – X axis drag chain unmounted

The Y axis drag chain was short enough to pull the cable out without drama.

I guesstimated the overall length from laser head to controller, cut a six conductor 26 AWG silicone ribbon cable generously longer than half of that, peeled it down the middle, then put a JST SM connector where the sections meet at the end of the gantry:

OMTech focus pen – gantry wiring

Obviously, those connector halves went on before snaking the other end of the cable sections through their drag chains. I paid considerable attention to keeping the ribbons flat and untwisted throughout their lengths, in hope they’d flex easily as the chain bends.

AFAICT there was no good way to use the old wire to pull the new wire through the chain, so running flexy silicone ribbon cable through a drag chain required tweezers, patience, and persistence. I had to realign the existing wires & tubes at various points so they didn’t twine around each other and block the path.

Another JST SM connector at the laser head allows removing / installing the pen as needed:

OMTech focus pen – reinstalled

The connector pins and sensor wire colors:
1. GND = blue = common = marked cable conductor
2. OUT = black = sensor output
3. 24V = brown = power
Wiring the new cable to the controller’s 24 V / GND / LmtU- terminals showed it now worked perfectly.

Reducing the vertical offset between the tip of the pen and the tip of the nozzle was then straightforward …
2025-12-23
Laser Cutter: Ortur YRC-1 Re-Wiring

Although the Ortur YRC-1 chuck rotary comes with a long cable, the connector doesn’t match anything in my heap, so an adapter of some sort was in order. The box includes three different adapters for various machines, none of which I have, but which served as raw material.

One of the adapters put the motor winding pairs together, which seemed like a Good Idea™:

Ortur Chuck Rotary – cable routing

That view has the stepper motor flipped 180° from its normal orientation; the motor cable connector normally points downward from the bottom.

The rotary has no strain relief for the cable, so I stuck a cable clip on its left side (in the normal orientation):

Ortur Chuck Rotary – cable clip

That arrangement captures the adapter, immobilizes the wiring at the motor, and puts all the strain on the more easily replaced cable, which is now a length of flexy 24 AWG silicone ribbon cable.

I don’t have a connector matching the Ortur adapter, but JST SM pins seemed about the right size:

Ortur Chuck Rotary – cable pins

Entombing that mess with a squirt of hot melt glue should keep them out of trouble.

You can see my matching JST SM connectors on the right end of the ribbon cable :

Laser Rotary – on platform

A cable clip stuck to the front cross member of the machine frame (just beyond the angled magnet) holds the unplugged end out of harm’s way when the rotary isn’t present.

The ribbon cable burrows through the guts of the machine to the A/B terminals of the smaller stepper driver in the electronics bay:

Laser Rotary – R driver – detail

Flipping the front-panel switch to enable the rotary driver / disable the Y axis driver enthusiastically spins the chuck when the controller thinks I’m jogging the Y axis:

Laser Rotary – control switch

Making it do something useful requires more pondering.

2025-12-19
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 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

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