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
Long years ago, the Bakelite (or some such) lid on our rarely used teapot disintegrated, whereupon I replaced it with an aluminum sheet and metal knob. Admittedly, a metal knob was not the brightest idea I ever had, but it sufficed for a few uses over the intervening decades.
Mary hosted this month’s quilting bee and, after having someone else bring a larger teapot for the occasion, suggested I Make. A. Better. Knob. After a bit of searching, this statue seemed appropriate for the season:
Skull teapot knob
It’s printed with PETG filament that should easily withstand the no-more-than-boiling-water temperatures found atop a teapot.
I imported the original model into PrusaSlicer, shrank it to 50 mm tall and simplified the mesh, exported it as an OBJ file, imported it into OpenSCAD, mashed it together with a 1/4-20 threaded_nut from BOSL2, added the finger protector, and got a suitable model:
Teapot Knob – solid model bottom view
The as-printed threads were a bit snug with $slop=0, but running the screw in with a dot of silicone grease to ease the way worked fine.
I should rebuild the whole lid in PETG-CF sometime.
The Ruida KT332N controller on my OMTech laser cutter has two settings affecting the final position of the U axis (which controls the platform’s position) after pushing the Focus button on the machine console:
KT332N Laser Controller display
After turning the machine on or pressing the Reset button, the U axis does not automatically home and reports its position as 1000 mm. This allows manual control in either direction with the U↑ and U↓ buttons.
Pushing the Focus button (then confirming the action by pressing the Ent⏎ button) causes the controller to raise the platform until the focus “pen” (which is really a switch) trips, presumably on the material you intend to cut / engrave. This picture shows the pen and its attachment to the laser nozzle:
OMTech laser focus pen-switch
The pen’s position in its clamp has no relation to the laser beam focal point below the nozzle: loosening either of the clamp screws lets you move the pen vertically. You must tell the controller how much to move the platform after the switch trips to properly set the focus, which means you must measure that distance. More on that later.
The vertical position of the platform when the “pen” switch trips is its Home position. The controller then lowers the platform by the distance in the Home Offset setting and defines that position as U = 0.0 mm.
The Home Offset can be zero:
KT332N Home Offset Setting
In which case the platform does not move after the switch trips:
Focus step gauge – 3 mm
The step gauge shows the nozzle is 3.0 mm above the material (the first step is 2 mm, because a 1 mm acrylic tab is crazy talk) when the switch trips. Although you can’t quite see the switch plunger through the gauge, it has about 5 mm of travel before tripping, which means it’s firmly pressed against the material and you must not move the nozzle in X or Y to avoid scraping the plunger across the material.
Setting Home Offset to 15.0 mm lowers the platform by 15 mm after the switch trips, putting the nozzle 18 mm above the material:
Focus step gauge – 18 mm
You can (and I have) set the Home Offset so the platform lowers by exactly enough to put the focused beam at the top of the material: push the Focus button and the machine automatically focuses on the material and sets U=0.0 mm at that level.
Unfortunately, the controller will subsequently not move the platform above that position, corresponding to U axis coordinates below zero. That means you (well, I) cannot move the platform upward to put the focus point into the material, as is sometimes required for a good cut through thicker material.
The Focus Distance setting defines an additional distance from wherever the Home Offset leaves the platform:
KT332N Focus Distance Setting
It’s not 15 mm, because I was fiddling with the focus.
That value will position the platform 16 mm below the switch trip point. Because Home Offset = 0.0 sets the U axis coordinate to zero at the trip point, the U axis will be at 16 mm when the platform stops moving.
The key difference is that the controller will now allow the platform to move upward, with decreasing U axis coordinates, until it reaches the switch trip position at U=0. The last 5 mm of travel will occur with the switch actuator pressing against the material, so it’s pretty much useless for actual cutting or engraving.
So I think the way to go involves setting:
Home Offset to the 5-ish mm required for full switch release
Focus Distance to the remaining 10-ish mm with the focal point on the material surface
I hadn’t done that before, because I hadn’t thought this through.
The Home Offset depends only on the switch travel before it actuates and won’t change when (not if) the pen position changes with respect to the nozzle.
The Focus Distance defines the additional travel for proper focus at the material surface, so that’s where all the variations due to pen position will go. Unfortunately, that distance cannot be directly measured, because it corresponds to the difference between two positions.
As before, the sole & lugs on Mary’s new Specialized cycling shoes requires too much torque to release the cleat, so I once again carved off everything that got in the way:
Cycling shoe sole carving
A field test prompted a little more carving, but you get the general idea.
This surely affects the shoes’ lateral stability, but getting her feet out of the cleats when & where needed outweighs everything else.
As expected, the adhesive foam strips I used on the bathtub soap tray didn’t survive continued exposure to hot soapy water, so Version 2 includes hooks securing it to the ceramic soap tray and a few other tweaks:
Bathtub Soap Tray – V2 – LightBurn layout
The view from the top:
Soap Tray V2 – top
The hooks are more visible from the bottom, as is the 10 AWG copper wire preventing the whole affair from rotating around the ceramic handle from the weight of the soap bar:
Soap Tray V2 – bottom
Ignore the usual crud you’ll find on your ceramic soap tray, too.
It’s not particularly elegant, what with being cardboard, but it’s a proof of concept that will determine the final size.
The top layer is a ring around the lamp pedestal for a bit of stabilization protecting the four M3 screws holding the base to the lamp. Those screws sit on a 60 mm square, offset 1 mm to the front of the lamp:
NisLite Baseplate – LightBurn layout
Which explains why I typically make the first few versions of anything out of cardboard.
For the record, those inserts look like this:
Converted Ottlite – brass inserts
A pair of very flat-head M3 screws hold the front inserts in place through holes match-drilled in the remains of the bosses I’d long ago epoxied in place. I pressed the rear inserts in place by misusing the drill press, as the lamp is much too tall for the heat setter.
Then comes the iron base weight:
Converted Ottlite – iron weight
And then the steel outer plate:
Converted Ottlite – steel cover plate
The new base plate gets a ring around its perimeter for clearance under the four pan head M3 screws into the inserts.
If the cardboard base is stable enough, we’ll do an acrylic version in cheerful primary colors.
The LightBurn layout in SVG format as a GitHub Gist:
The general idea of a light box is (wait for it) a uniform background in a box full of bright light:
Light Box – overview
Obviously, this is a low-budget light box, but it makes perfect sense if you already have an essentially unlimited supply of moving boxes, 11×17 inch plotter paper, and a couple of photo / video lights lying around.
A two-layer cardboard ring glued to the top keeps the light from sliding off the box and stiffens the gaping hole letting the light shine through.
You’d normally use a fabric background to get rid of those ugly gaps around the edges and a larger box would be better, so this is along the lines of a proof-of-concept.
In this day and age, you’d normally use a phone camera:
Light Box – gears overview – DOF
The lens on my Pixel 6a has a fixed focal length (around 4.4 mm = 27 mm equivalent) and a fixed f/1.8 (-ish) aperture, producing a razor-thin depth of field at the rear of the front gears. Note the fuzzy gears in the background, all of three inches away, and the slightly fuzzy front edge of the front gears. The camera’s digital zoom doesn’t help matters in the least, despite the AI-powered interpolation.
Keeping things close together helps, although the far end of the wipe towers and the rear of the gears lose detail:
Light Box – gears stacked
Looking from above also helps a little, but a top viewing port would reduce the skewed perspective:
Light Box – gears detail – DOF
Shallow DOF keeps your attention on the foreground, which is why real photographers use it for portraits:
Light Box – gears standing – DOF
The camera, an ancient Sony DSC-H5 with a zoom lens going down to f/8, still does nice work through a 2× macro adapter lens:
Light Box – gear detail – top light
The DOF is still narrow, but at least the entire front gear is in focus.
Adding a front light picks out the knurling:
Light Box – gears detail – front light
The results definitely look better than before, but it’ll take a bit of getting used to traipsing to the Basement Laboratory for every photo …
The flat robot vacuum assigned to clean the floors around here would occasionally get stuck under the leg of my Husky workbench-as-desk and fail to complete its mission. Living in the future makes solving that problem a matter of minutes:
Husky workbench caster feet – installed
The upper rim captures the locked-in-place wheel in a 35×25 mm recess atop the middle 45×35 mm slab, with a 2.5 mm cork layer on the bottom. Laser-cut, of course, glued with ordinary yellow wood glue, and clamped for about half of a Squidwrench remote meeting.
Raising the desk by 5.5 mm gives the Flat One juuust enough clearance to scuttle under there:
The Smell of Molten Projects in the Morning 
