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
Nearly everybody with a floor-standing laser cutter eventually decides it’s much too low for comfort:
OMTech Laser – leg risers
Those are the 5 inch sections of a furniture riser set (the 3 inch sections are visible at the left rear of the picture, ready for deployment). With the legs extended to their full length, they put the laser’s honeycomb platform about 30 inches from the floor, so the complete set will raise it to 33-ish inches.
I went full-frontal Archimedes by levering each end of the cabinet up an inch at a time using one of those maple shelves atop an increasingly tall fulcrum made of various planks, then lowering the ever-lengthening legs atop stacks of plywood. Eventually I could roll a floor jack under the end beam to simplify the rest of the lift.
Protip: lock the casters to prevent movement.
More height makes reaching inside the machine much more comfortable!
At least for me. Mary says it’s now much too high for her …
The OMTech laser arrived with a 120 VAC fan blowing air out of the electronics bay on the right side of the cabinet. It runs continuously, because the stepper drivers remain active even when idle, and gave off an annoyingly high-pitched whirrrrr.
The Big Box o’ Fans produced a 24 V tangential blower which (felt like it) moved about the same amount of air with a quieter and lower-pitched hmmmmmm, so I made an adapter to fit it into the original cabinet opening:
OMTech laser – improved electronics fan – mounting
Yeah, it’s hot-melt glued to a stacked pair of laser-cut cardboard plates. Fight me.
The black cardboard makes it rather low-key from the outside:
OMTech laser – improved electronics fan – grille
I reused the original grille, mostly because otherwise I’d have to put it somewhere else.
The anemometer suggests 5 m/s airflow an inch from the grille. Rounding downward from the 25×35 mm opening says it’s pulling 9 CFM from a compartment with a little over a cubic foot of free volume, which sounds enough good to me. For whatever it’s worth, this airflow calculation disagrees with all of the specs and my handwaving calculation in that old blog post.
The cabinet hatch has slits distributing the incoming air over all the active ingredients (somewhat visible inside behind the flash glare):
The OMTech 60 W laser gets its air assist from an aquarium-style air pump in the right rear of the cabinet:
OMTech 60W laser – Z motor – air pump
Since that picture, I’ve sealed the slots for the Z-axis belt tensioner pulleys.
The pump is connected directly to the AC line at the main barrier block (blue and brown on leftmost two terminals):
OMTech 60W laser – AC barrier strip
Even though the pump has very flexy rubber feet, it’s annoyingly noisy and should be off when the laser beam is off.
The knockoff RuiDa KT332N controller (possibly by Ryxon, based on a LightBurn forum thread, but without a visible name anywhere on the hardware or in the manual) has an Aux.Air output terminal:
KT332N Controller – output wiring plug- glued
Yes, the controller is mounted that way inside the electronics bay.
Chipping away the hot-melt glue over the terminals lets you pry the terminal block out of the controller:
KT332N Controller – output wiring plug
The KT332N manual describes the Aux.Air pin 2 function:
Dedicated output. When auxiliary air control is enabled, this port outputs a control signal to control the valve or other relay to release auxiliary air. This port is multiplexed with pen control signal. When auxiliary air control is disabled, this port is assigned as pen control. The output type is open collector. The output can be set to be synchronized with laser or synchronized with work.
Section 4.6 — General and dedicated output
The word “pen” does not occur anywhere else in the manual, so I have no idea what it might mean. Perhaps the controller can also become a pen plotter?
A configuration screen (Menu → Para Setting → Auxi.Air) gives the options:
KT332N Controller – Air Assist Config screen
Section 9.2 of the manual describes the choices, although not quite in the same words:
Blowing method：The way of the air is blown during processing. Can be configured to output fire, process gas, and manual gas.
Blow on delay：Delay time after turning on air blowing
Blow off delay：Delay time before turning off the blow
Section 7.2 gives the electrical parameters:
All output signals of this controller are output based on opto-coupler isolation technology and OC gate output. Its maximum driving capacity is 300mA, which can directly drive 6V / 24V relays, light-emitting indicators, buzzer alarm devices, etc.
Section 7.2 — Output
I wired an AC solid state relay (surely a counterfeit Fotek) in series with the pump’s AC Line wire:
KT332N Controller – Air Assist SSR installed
It’s firmly stuck to the bottom of the electronics bay with heatsink tape, not that it gets particularly warm switching a few dozen watts of pump.
Because the output pin is active low, the SSR + input comes from a ferrule jammed into the 24 V supply pin on the controller, along with the original ferrule holding three other wires:
KT332N Controller – Air Assist SSR wiring
With all that in place, I turned it on and … the air pump did not turn on when I ran the next job. I could manually turn the pump on with the front panel Aux Air button, but it shut off as soon as I ran a file.
The “enable” setting referred to in Section 4.6 appears in the Vendor Parameters:
Enable the auxiliary air control : If you want to use the Wind signal of the output port to control the fan switch in layers, you must enable this parameter. Otherwise, the Wind signal outputs other signals.
Section 9.1 — Vendor Parameters
The Vendor Settings are protected by a password I don’t know do not appear in the section of settings I assumed they would be in, based on the manual’s wording. It seems an external program connected to the controller by USB or the network provides the only way to access these settings.
Fortunately, LightBurn exposes the Vendor settings after you click through a warning dialog:
LightBurn Vendor Config – Air Assist Enable
And then It Just Works™.
The “Blow when laser” option turns on the pump whenever the laser power supply is producing a beam, so it switches on and off at a furious pace. This is not the option you are looking for.
The OMTech 60 W laser arrived with an LED strip light under the gantry:
OMTech 60W laser – OEM lighting
That works reasonably well, if only because the pool of light travels with the gantry, but it’s always behind the area where you’re (well, I’m) setting up the Thing To Be Cut. An overhead can lamp with a warm-white CFL bulb contributes the yellowish foreground lighting, although I cast a big shadow when leaning into the cutter.
Adding three COB LED strips along the sides definitely improved the situation:
OMTech 60W laser – COB LED strips
The glare will require shades along their top, but that’s in the nature of fine tuning.
I got 24 V COB LEDs to match the cutter’s power supply and reduce the overall current along the strips, but upon further inspection the OEM power supply seems under-specified for its job. The XY stepper drivers each draw 3.5 A peak, the Z (they call it U) axis driver is set for 5.1 A peak, and the knockoff RuiDa controller also runs at 24 V with an unspecified current.
Rather than stress the OEM supply, some rummaging in the Big Box o’ Wall Warts produced the 24 V 2 A power brick shown in the first picture. The previous owner had cut off the no-doubt specialized connector, so I had no qualms about splicing in a 5.1 mm coaxial power plug.
On the other end, I amputated the AC line plug, crimped on a pair of ferrules, and inserted them into the AC power barrier strip inside the electronics bay:
OMTech 60W laser – LED power supply
Yes, that little smudge in the middle of the brick is an Genuine Embossed Apple logo, so you know it’s gotta be good.
The canonical beam alignment target seems to involve tape stuck on the mirror bracket:
OMTech 60W laser beam test – tape target
With a full-power beam burned through it:
OMTech 60W laser beam test – mirror 1
The roll of “white masking tape” supplied by OMTech turned out to be knockoff tapeless sticky adhesive film. After sticking a length to the mirror bracket, the white backing tape peels right off, leaving the adhesive film stuck to the bracket. Well, my tapeless sticky roll was running low, so this roll won’t go to waste.
A laser cutter can make intricate paper doodads, so I conjured better targets from the Vasty Digital Deep:
OMTech 60W laser – beam alignment – 2022-03-22
They’re burned into an ordinary manila file folder in “dot mode”: 2 ms pulses at 30% power separated by 0.25 mm. The 1 mm graticule locates the beam relative to the center, which is pretty close to the actual center of the opening, because the outer 17 mm cut fits neatly into the 17.5 mm hole. The label tells you where it goes and which line should point up.
Your mileage will vary, but the general idea is to have a disk held in place by actual masking tape:
OMTech 60W laser beam test – mirror 1
Admittedly, orienting the graticule requires a bit of dexterity, but getting it pretty close is pretty easy.
Set the laser to fire a single 10 ms pulse when you press the front-panel button, thereby toasting a spot at the most intense part of the beam:
OMTech 60W laser beam test – mirror 1 fired
Repeat to record the beam position at all three mirrors:
OMTech 60W laser beam test – mirror 3 fired
The focal point target serves to verify the focused beam size and its alignment with respect to the aiming laser spot:
OMTech 60W laser beam test – focus point
That target came from a scrap of cardboard while I was figuring out how to make the things.
All in all, OMTech did a pretty good job of aligning the beam, although the red laser dot needed a nudge. Now I have a record of where the beam was before I mess with clean the mirrors and lenses.
The OMTech laser cutter has six access hatches, each with one or two latches. These are not locks, although you do need a triangular “key” to turn the latch plug:
OMTech laser – latch – cylinder point up
Being that type of guy, I want all the latches to have the same plug orientation when they’re closed, so that I can hold the key one way, poke it into any latch without thinking too hard, and have it fit onto the plug:
OMTech laser – latch key – latched position
A quarter-turn clockwise (remember clocks with hands?) then releases the latch:
OMTech laser – latch key – unlatched position
Inside the hatch, the closed position corresponds to a tongue capturing a flange around the cabinet opening (not shown):
OMTech laser – latch – latched position
After the quarter-turn, the tongue releases the flange:
OMTech laser – latch – unlatched position
So, we’re not talking high security here.
As delivered, the plugs had more-or-less random orientations when they were closed and some required a counterclockwise quarter-turn to release.
It turns out the latches aren’t a complete unit that simply drops into a hole in the hatch:
OMTech laser – latch parts
I sympathize with whoever must assemble ten handfuls of parts into ten latches on a production line and I also understand why orienting the plug wasn’t on that person’s to-do / QC checklist. I further understand why two cylinders lacked the big toothed washer under the nut; it’s not essential to the function and nobody will ever miss it.
The plug has a triangle on one end (for the key) and a square on the other (for the tongue), with one triangle point aligned to a side of the square:
OMTech laser – latch plug
To my way of thinking, that point must be upward, as shown in the first picture, when the latch is secured.
The cylinder can fit into the square(-ish) hatch hole in four possible ways, but its symmetry allows only two unique orientations. It must look like this in order to put that point upward when the plug is maximally counterclockwise (my finger is pointing upward):
OMTech laser – latch cylinder
So I devoted a pleasant half-hour to reducing the latch entropy.
The screw attaching the tongue to the plug also controls the friction of that spring against the plug as you (well, I) turn it. All the screws now sport a dab of Loctite to ensure the tension remains mostly constant (at least for a while), as do the two large nuts lacking corresponding toothed washers.
The “key” has no marking to indicate its “point-up” orientation, so I stuck a snippet of label on one side, with a jaunty red highlight marking the point. Something better will surely occur to me, but it’s no longer in the critical path.
The best place for the OMTech laser cutter seems to be snuggled at base of the chimney, venting into the long-disused fireplace through the steel plate adapting a long-gone wood stove to the opening:
Duct fan installed
The short run of flexible tubing allows some give-and-take at the cutter’s vent outlet. The elbow on the duct fan’s output terminates in a blast gate to cut off the draft blowing up (or down!) the flue with the fan off.
The cutter arrived with a huge high-speed axial blower screwed to its output baffle:
OMTech 60W laser – OEM vent fan
The noise from that fan had to be heard to be believed.
The cylindrical exhaust duct attached directly to the motor with four screws, only two of which matched holes in the baffle plate:
OMTech 60W laser – modified vent
A trial fit revealed the assembly rattled something awful: those two screws let the duct vibrate against the baffle. Match-drilling two more holes into the baffle let me mount the duct with three screws and, in combination with the foam gasket, it is now solid and quiet.
A quick check shows the duct fan draws 10 to 11 m/s through the baffle at full throttle, roughly 400 CFM. That’s pretty close to the flow measured through a long pipe and, with only 6 ft³ of stink inside the laser’s cabinet, ought to exhaust the fumes just fine.
The Smell of Molten Projects in the Morning 
