The Smell of Molten Projects in the Morning
Ed Nisley's Blog: Shop notes, electronics, firmware, machinery, 3D printing, laser cuttery, and curiosities. Contents: 100% human thinking, 0% AI slop.
This is what happens to an uncoated plywood coaster with fairly deep laser engraving after about half a year of use:
The poor thing went all potato chip:
I swapped it for one with polyurethane sealant, much like those fancier coasters with the same layout, and we’ll see if it survives longer …
Tuck a neatly laser-cut disk into a flimsy cardboard tube:
Put a big conical center in the tailstock:
Whereupon the tube remains nicely tubular on both ends and aligned along the chuck axis:
Which is why you save all that scrap material …
Yes, it’s the core from a toilet paper roll, which is way cheaper than burning through tumblers / mugs / shot glasses / whatever while figuring this stuff out.
The process of switching the laser cutter from “normal” operation to the Ortur YRC-1 rotary and back again requires a checklist:
Which looks like this:
The same thing as a PDF will be more printable or readable.
Previous posts cover what goes into making it work:
Home Offset and Focus DistanceNotes:
Rotary.lbset and Linear.lbset files live on a file server with daily backups. Such backups will come in handy when you inadvertently overwrite one of those files with the other one. Trust me on this.Rotary.lbset file does not have Rotary Mode enabled, because the KT332N does not home the Y axis in that mode. If your rotary lacks a home switch, then it doesn’t matter and you’re on your own.[Reset] button that allegedly does a power-on reset and reloads all the changed Machine Settings. This sometimes does not work as expected: power-cycling the controller is the only way to be sure.[Origin] at the foot of the pad’s base for more elbow room.Move window does not accept formulas, so you must divide the workpiece diameter by two. Using a focus stick to verify the ensuing nozzle-to-workpiece distance is a Good Idea™.Job Origin dot must be on the top row, because the KT332N does not go into regions with negative coordinates. With the chuck on the left and the [Origin] just to its right, the upper left dot locks the LightBurn selection to the physical limits.[Use Selection Origin] puts the Job Origin at the upper left (per the dot) of whatever you’ve selected, not everything on the LightBurn workspace. [User Origin] then locks the selection to the [Origin] set on the controller.As the saying goes, it works for me …
The standard jaws for the Ortur Rotary loom over small-diameter workpieces:
Some measuring and modeling produced petite 3D printed jaws:
Admittedly, those jaws aren’t doing much of anything, but they’re not nearly as much in the way. You (well, I) can screw them in closer to the center to overlap the chuck jaws or another hole outward for slightly larger cylinders.
The solid model looks about the same:
They build face-down with a little support under the screw recesses for a clean fit on the chuck:
Teeny jaws might be handy:
Screwing them in one hole outward lets them grip medium cylinders without sticking out from the chuck jaws:
The OpenSCAD code lets you pick which screw holes you want, but it does not error-check the perverse choices.
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,Chuck,ChuckJaw,Jaw] | |
| InnerScrew = 1; // [0:3] | |
| OuterScrew = 3; // [2:4] | |
| /* [Hidden] */ | |
| ID = 0; | |
| OD = 1; | |
| LENGTH = 2; | |
| HoleWindage = 0.2; | |
| Protrusion = 0.1; | |
| Gap = 5.0; | |
| NumSides = 8*3*4; | |
| $fn=NumSides; | |
| WallThick = 2.0; | |
| ScrewHead = [4.0 + HoleWindage,7.0 + HoleWindage,4.0]; | |
| ChuckOD = 66.0; | |
| ChuckThick = 10.0; | |
| ChuckBCR = [3.5,7.5,15.0,22.5,30.0]; // M4 tapped in chuck jaws | |
| ChuckJawOA = [ChuckOD/2,8.0 + HoleWindage,3.5]; | |
| JawBlock = [0,15.0,2*WallThick + ScrewHead[LENGTH]]; // .x will be variable | |
| JawRound = 1.0; // tip rounding | |
| //—– | |
| // Single chuck jaw with holes | |
| module ChuckJaw(Holes=true) { | |
| difference() { | |
| intersection() { | |
| cuboid(ChuckJawOA,anchor=BOTTOM+LEFT); | |
| cyl(ChuckJawOA.z,d=ChuckOD,anchor=BOTTOM); | |
| linear_extrude(h=ChuckJawOA.z) | |
| hexagon(od=ChuckOD,rounding=2.0,anchor=LEFT); | |
| } | |
| if (Holes) | |
| for (i = [0:len(ChuckBCR)-1]) | |
| right(ChuckBCR[i]) | |
| down(Protrusion) | |
| cyl(2*ChuckJawOA.z,d=ScrewHead[ID],anchor=BOTTOM); | |
| } | |
| } | |
| // Chuck layout | |
| module Chuck(Holes=true) { | |
| cyl(ChuckThick,d=ChuckOD,anchor=TOP) position(TOP) | |
| for (a = [0:120:360]) | |
| zrot(a) | |
| ChuckJaw(Holes); | |
| } | |
| // Gripping jaw | |
| module Jaw(Screws=[1,3]) { | |
| HoleOC = ChuckBCR[Screws[1]] – ChuckBCR[Screws[0]]; | |
| JawOAL = HoleOC + ScrewHead[OD] + 2*WallThick + (JawBlock.y/2)/cos(30); | |
| difference() { | |
| left(JawOAL/2) | |
| intersection() { | |
| cuboid(JawBlock + [JawOAL,0,0],anchor=BOTTOM+LEFT); | |
| linear_extrude(h=JawBlock.z) | |
| hexagon(od=ChuckOD,rounding=JawRound,anchor=LEFT); | |
| right(JawOAL) | |
| linear_extrude(h=JawBlock.z) | |
| hexagon(od=ChuckOD,rounding=JawRound,anchor=RIGHT); | |
| } | |
| right(0*JawOAL/2) | |
| for (i=[-1,1]) | |
| right(i*HoleOC/2) { | |
| down(Protrusion) | |
| cyl(JawBlock.z,d=ScrewHead[ID],anchor=BOTTOM); | |
| up(2*WallThick) | |
| cyl(JawBlock.z,d=ScrewHead[OD],anchor=BOTTOM); | |
| } | |
| down(Protrusion) | |
| cuboid([JawOAL,ChuckJawOA.y,WallThick + Protrusion],anchor=BOTTOM); | |
| } | |
| } | |
| //—– | |
| // Build things | |
| if (Style == "Chuck") { | |
| Chuck(); | |
| } | |
| if (Style == "Show") { | |
| xrot(180) | |
| yrot(90) { | |
| color("Gray",0.8) | |
| Chuck(); | |
| up(ChuckJawOA.z – WallThick) | |
| for (a = [0:120:360]) | |
| zrot(a) | |
| right((ChuckBCR[InnerScrew] + ChuckBCR[OuterScrew])/2) | |
| Jaw(Screws=[InnerScrew,OuterScrew]); | |
| } | |
| } | |
| if (Style == "ChuckJaw") | |
| ChuckJaw(); | |
| if (Style == "Jaw") { | |
| Jaw(Screws=[InnerScrew,OuterScrew]); | |
| } | |
| if (Style == "Build") | |
| for (j=[-1:1]) | |
| fwd(j*(JawBlock.y + Gap)) | |
| up(JawBlock.z) xrot(180) | |
| Jaw(Screws=[InnerScrew,OuterScrew]); | |
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™:
The general idea:
Focus Distance puts the laser head at the proper height for a focused spot on the padThe solid model:
Features of note:
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:
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 :
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:
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:
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:
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 = 8*3*4; | |
| $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(); | |
Along the same lines as the foam feet under the 3018XL plotter, the MK4 now has a bit of vibration isolation:
I’d stuck four exercise mat tabs (scraps of a flooring project) under the feet, but the loading was much too high:
It was really an excuse for some non-critical cutting with the 3 inch lens in the laser cutter:
The foam cut nicely, albeit with a 1.3 mm kerf, and the chipboard & plywood seemed about the same. They’re 30 mm square and, should they flatten out, I have enough foam scraps for a larger set.
Unlike the 3018 feet, my deflicted ears can’t tell the difference with these place, so I assume a standard MK4 squash-ball foot upgrade isn’t worth the filament.
The manual accompanying my OMTech 60 W CO₂ laser clearly states it has a 1.5 inch focus lens:
Which I had always assumed was the case, even though a short lens like that would typically be used for fine engraving due to its smaller spot size. One could argue the carton should have included a 1.5 inch lens in addition to whatever was in “its optics”, but it didn’t.
It has a 2 inch lens, as I confirmed while switching to a 3 inch lens to get more clearance over the Ortur rotary than the stock lens allows:
The bottom of the lens (its planar surface) sits inside the nozzle at (about) the same level as the joint just above the assist air fitting:
That’s the proper focus distance for the 3 inch lens, with the lens 3 inch = 3 × 25.4 = 76.2 mm above the platform. There’s obviously some room for quibbling about the optical center of the lens vs. the lower surface and so forth and so on, but a ramp test shows it’s Close Enough™:
Which adds an inch of clearance, enough to prevent obvious collisions:
Changing the lens requires removing the air fitting, during which operation I also moved the clamp holding the focus pen. Because that changed where the switch trips, the Focus Distance also changed:
The clearance under the nozzle depends only on the lens:
I’ve been using step gauges for manual focusing with the 2 inch lens:
I figured a rod would be more appropriate for the 3 inch lens and, hey, now that I have a rotary, I can engrave it:
Through no fault of mine at the lathe, that stick is exactly 43.9 mm long, but “44 mm” fit better.
The Smell of Molten Projects in the Morning 