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.
Having recently shotgunned Amazon’s selection of colored art paper, this becomes possible:
It’s the same geometry as the plain white layered version, with somewhat more attention to detail, and consists of a dozen layers glued and stacked on an assembly fixture.
The quilt-block version uses simple layering:
No commercial potential, but I like the effect.
Spotted during Autumn Window Cleaning:
That’s the compression spring inside the curtain rod over the kitchen sink, intended to push the ends against the cabinets on either side. The screw slides along the outer rod and when tightened, backstops the spring against the inner rod.
The end of the spring is apparently intended to twist and jam inside the inner half of the rod, but that seemed so … unesthetic.
Being in the midst of setting up a Windows 11 box for the laser cutter, I used it as an excuse to fiddle with the RDP configuration to get LightBurn running in full screen mode on the monitor atop my desk; more about all that later.
The little pusher block is a hull around a pair of circles the same diameter as the smaller dimension of the inner rod, spaced apart enough to match its width, then laser-cut from a scrap of 1/4 inch acrylic:
Which assembles as you’d expect:
The spring seems much happier pushing against the block, doesn’t it?
Admittedly, this was completely unnecessary, but if you think of it as a side effect of the Win 11 thing, it makes at least a little sense.
Three months of outdoor exposure suggest that laser test paper can survive use as a plant tag for one growing season, at least when it remains flat:
The two upper tags demonstrated the paper has no flexibility worth mentioning, so it cannot become a tag wrapped around a stem.
The two lower labels spent their time tucked into a window frame where they got plenty of sun & rain without the benefit of a backing plate. Looks good to me!
Contrary to my expectation, the craft adhesive sheet behind this label survived intact, although the label itself took some damage, perhaps from the more direct sunlight out on the deck:
In any event, they look Good Enough™ for our simple needs and next year’s plants will be properly labeled.
A discussion about engraving leaves on the LightBurn forum prompted an experiment with a seasonally appropriate motif:
Those ran at 500 mm/s with 8 to 10% power, respectively the fastest speed & lowest power for my 60 W CO₂ laser.
The mmmm material has obvious irregularities and doesn’t lie flat:
A closer look:
The line interval is an absurdly large 0.5 mm to keep the leaf from falling apart, as the laser burns almost completely through despite the low power.
I thought about scattering a bunch of these along the driveway, but came to my senses just in time …
The humidifier that Came With The House™ had a lid with two broken plastic hinges that I figured I could never replace, but while cleaning out the fuzz for the upcoming season I found one missing piece stuck inside the lid. Given a hint, I glued it back in place:
There’s a strip of duct tape around the outside holding the fragment in place while the adhesive cured.
A manual curve fit to the image in Inkscape produced the red outline, which gets saved as a plain SVG and fed into OpenSCAD to create a solid model:
The cylinder doesn’t exactly fit the end of the hinge, but it’s close enough. The straightforward OpenSCAD code making that happen:
// Humidfier Hinge Replacement
// Ed Nisley KE4ZNU
// 2024-10-20
HingeThick = 10.0;
PinLength = 10.0;
ScrewOD = 2.0;
NumSides = 2*3*4;
Protrusion = 0.1;
difference() {
union() {
translate([0,0,HingeThick])
cylinder(d=6.0,h=PinLength,$fn=NumSides);
linear_extrude(height=10.0,convexity=5)
translate([-3.1,-8.0])
import("Humidifier Hinge - ouline.svg");
}
cylinder(d=ScrewOD,h=4*(HingeThick + PinLength),center=true,$fn=8);
}
The pin has a hole for a M2 screw, but contemplation of the broken pieces suggested the pin wasn’t the weakest link, which later experience confirmed.
Figuring I’d need only one hinge, I made a spare for fitting:
The unmodified part fit just about perfectly, whereupon a completely ad-hoc fixture involving a pair of laser-cut MDF slabs, a craft stick epoxy mixer, and more duct tape held it in place while the adhesive cured:
The hinge pin turned out to be half a millimeter too long, which is easily fixed, and it worked fine:
That’s more duct tape wrapped around the perimeter to hold the pieces in place, should it break again.
Which, I regret to report, occurred on the way up the stairs from the Basement Shop™ when the lid slipped from my grasp, fell away from the rest of the humidifer’s top panel, and jammed open:
The PETG-CF part held together, the adhesive remained bonded to both pieces, but the original plastic fractured just below the joint. A closer look from the other side shows the break:
The other hinge broke about where it did before.
So the humidifier remains in service with the lid in status quo ante and a small bag inside holding the fragments for the next return to the shop.
Drat!
A few ramp tests with various Focus Distance + Home Offset settings as noted:
The bottom test was at 15 mm, which (contrary to previous estimates) seems to center the narrow band round 0.0 mm. Given the depth of field, a millimeter one way or the other likely doesn’t matter, particularly given the mmm lack of flatness in many materials.
The controller settings making it happen:
What they mean:
Home Offset = distance to retract after the autofocus “pen” = switch activates so the tip of the pen clears the materialFocus Distance = distance beyond Home Offset to put the focal point at the surface of the material (or wherever you want)Enable Homing = makes autofocus work at the push of a buttonHoming Speed = how fast the platform moves while focusingGetting the focus right really makes the laser cut like it should!
After figuring out the Ruida focus settings, a focus ramp fixture seemed like a good thing to have around:
The solid model shows a bit more detail:
Centering the autofocus “pen” = switch on the peg in the back puts the beam dead-center in the fixture, with the notches as comfort marks. The top of the peg is flush with the center notch, so the machine should be properly focused at that level after a focus operation.
Obviously, your laser has a different pen location, as will this one the next time I fiddle with anything around the nozzle.
The general idea is to tape a target to the ramp, with some attention to flattening the paper (tape the edges in critical spots as needed) & putting its zero at the center marks, align the fixture to the laser path along the X axis & secure it with a few magnets, then burn a single line at low power along the length of the scale:
The mark will be thinnest in the region with the best focus, which should be centered around the 0.0 mark in the middle. In that photo, the thinnest section runs from about -2.0 to +1.0, although (at least for me) it does take some squinting to be sure.
The ramp has a 1:10 = 5.71° slope to spread 1 mm of vertical focus across 10 mm of horizontal distance. If you’re being finicky, you should rescale the targets to correct the 0.5% cosine error, but IMO it’s irrelevant for this purpose.
A few more tests varying the focus distance by a millimeter:
AFAICT, setting the controller’s Focus Distance to 16 mm is about right. That puts the focal point 18 mm below the nozzle, as shown in the earlier post, and is pretty much what I’ve been using all along.
The OpenSCAD code as a GitHub Gist, along with a simplified target layout in SVG format:
| // Laser Cutter Focus Ramp Fixture | |
| // Ed Nisley KE4ZNU | |
| // 2024-10-10 | |
| FocusPenOffset = [-19,23,0]; | |
| FocusPenOD = 10.0; | |
| RampHeight = 16.0; | |
| RampScale = 10; | |
| RampLength = RampScale * RampHeight; | |
| Magnet = [5.0,60.0,10.0]; | |
| NumSides = 3*4; | |
| Protrusion = 0.1; | |
| RampAngle = atan(RampHeight/RampLength); | |
| echo(RampAngle=RampAngle); | |
| Slot = [(RampLength + 2*5.0),10.0,8*RampHeight]; // very tall to cut through everything | |
| Body = [(Slot.x + 2*10.0),30.0,3*RampHeight]; // extend Z to reach baseplate | |
| FocusPillarHeight = (RampHeight/2) + Body.z/3; // match Z at center of body | |
| BasePlate = [(Body.x + 2*Magnet.x + 2*5.0),max(Magnet.y,FocusPenOffset.y + 2*5.0),3.0]; | |
| BaseRound = 5.0; | |
| //—– Build it | |
| difference() { | |
| union() { | |
| translate(FocusPenOffset) | |
| cylinder(d=FocusPenOD,h=FocusPillarHeight,$fn=NumSides); | |
| difference() { | |
| union() { | |
| rotate([0,RampAngle,0]) | |
| cube(Body,center=true); | |
| linear_extrude(height=BasePlate.z) | |
| hull() | |
| for (i=[-1,1], j=[-1,1]) | |
| translate([i*(BasePlate.x/2 – BaseRound),j*(BasePlate.y/2 – BaseRound)]) | |
| circle(r=BaseRound,$fn=NumSides); | |
| } | |
| cube(Slot,center=true); | |
| translate([0,0,FocusPillarHeight]) { | |
| cube([0.5,2*Body.y,1.0],center=true); | |
| rotate([0,RampAngle,0]) | |
| cube([2*Slot.x,0.5,1.0],center=true); | |
| } | |
| } | |
| } | |
| translate([0,0,-Body.z]) | |
| cube(2*[BasePlate.x,BasePlate.y,Body.z],center=true); | |
| } |
Contrary to what you might think, the targets are not laser cut, although you could use the crosshairs for LightBurn’s Print and Cut alignment.
The Smell of Molten Projects in the Morning 
