Category: Machine Shop

Mechanical widgetry

Human Lumbar Vertebrae
Having once again reawakened a back injury from long ago, I figured these were good for some comic relief:

L4 L5 vertebrae – assembled

The full-scale L4-L5 vertebrae are from Printables and the ¾ scale L5 is from somewhere I cannot recall. A mother lode of anatomical models is on Thingiverse if you want some 3D printing challenges.

The L4-L5 pair are part of an extensive human anatomic model locating all the pieces at their proper coordinates, so these two hovered about 800 mm above the XY plane. I ran them through the Grid:Tool mesh editor to center them at the XY origin, then put the bottom-most point at Z=0.

Rotating them individually in PrusaSlicer and painting only the most essential support got them to this state:

L4 L5 vertebrae – PrusaSlicer

Each one take about three hours, so I ran them individually to reduce surface blemishes and maximize the likelihood of happy outcomes. Worked like a champ.

The retina-burn orange disk is not anatomically correct, because the InterWebz apparently does not have a model for spinal cartilage:

L4 L5 vertebrae – assembled – disk detail

Instead, it’s a rounded cylinder resized into an oval, with its top and bottom surfaces formed by subtracting the vertebrae:

L4 L5 vertebrae disk – solid model

The OpenSCAD code doing the heavy lifting:
```
// Disk between L4 and L5 vertebrae
// Ed Nisley - KE4ZNU
// 2025-03-07

Layout = "Show";    // [Show,Build]

include <BOSL2/std.scad>

module Disk() {
  color("Red")
    difference() {
      translate([9,-18,36])
        rotate(110)
        resize([33,45])
        cyl(d=50,h=14,$fn=48,rounding=7,anchor=BOTTOM);
      import("../Spine/human-spinal-column-including-cervical-thoracic-and-lumbar-vertebra-model_files/L4 L5 vertebrae stacked.stl",
        convexity=10);
    }
}

if (Layout == "Show") {
  Disk();

  color("White",0.3)
      import("../Spine/human-spinal-column-including-cervical-thoracic-and-lumbar-vertebra-model_files/L4 L5 vertebrae stacked.stl",
        convexity=10);

}

if (Layout == "Build") {
  Disk();

}
```
All of the magic numbers come from eyeballometric measurement & successive approximation.

The Build layout left the disk floating in space, whereupon I used PrusaSlicer to reorient it edge-downward on the platform with painted-on support for minimal distortion:

L4 L5 vertebrae disk – PrusaSlicer

Two dots of E6000+ adhesive hold everything together.

All in all, it was a useful distraction. I’ve been vertically polarized for the last five days and it’s good to be … back.
2025-03-11
HQ Sixteen: Crud on the Tracks

Having devoted considerable effort to smoothing the HQ Sixteen’s path across the table, with commensurate improvement, Mary reported the machine suddenly developed a severe hitch in its left-to-right git-along. Given that she is moving fifty pounds of machine with fingertip pressure, anything interrupting its progress is a problem.

We found a spot where the machine abruptly and repeatably stopped rolling, but none of the four wheels had a visible problem and both tracks were smooth. The stitch regulator wheel sat directly above a table surface joint on the track base, but lifting it didn’t change the glitch. Rolling the machine while lifting the rear wheels off the track, which is significantly more difficult than it may seem, still encountered the bump.

Rolling while lifting the front wheels went smoothly, so something was wrong with one of the front wheels. I put the machine back at the worst spot, marked the bottom of both wheel rims, lifted-and-rotated the left wheel half a turn, and found the glitch happened with the right wheel’s mark downward.

I lifted the machine off the carriage, took the carriage to the Basement Shop, and discovered what we could not see in situ:

HQ Sixteen – wheel crud – detail

For scale, the wheels are 8 mm across the flanges.

That thing looks like this up close:

HQ Sixteen – wheel crud – detail

The fibers were almost invisible in my palm as I carried it upstairs to show it off.

Apparently, a few millimeters of plastic fiber dropped from space directly onto the track and got mashed into the wheel as it rolled along. Given the vast expanses of fabric & batting going into projects on a long-arm sewing machine, that crud could have come from anywhere.

As we now realize just how much trouble can come from a tiny bit of crud, finding the next hitch in the git-along will be easier.

2025-03-10
Subpixel Zoo: Capturing the Specimens
A Hacker News discussion led to the Subpixel Zoo, which led to thinking the patterns might make interesting layered “art”. After fetching the *.webp images and figuring out how to persuade Thunar to display them, the next step was converting them into paths suitable for laser cutting.

Although the images are algorithmically generated in a common layout, figuring out how to get the outlines as paths seemed to require a journey into the depths of the Pygame library and that would turn into a major digression.

Instead, start with one of the webp images:

sq_RGBY

The deliberate blurring apparently simulates what you see in real life.

Import the image into LightBurn, which converts it to grayscale under the plausible assumption you’re going to engrave the image on something. Then:
- Create a rounded rectangle overlaying the lower-left-most subpixel to good eyeballometric accuracy
- Turn it into a four-element rectangular array, twiddling the center-to-center spacing to match the subpixel layout
- Duplicate those four upward in another array to create a subpixel block, as marked in the upper-left corner of the original image
- Slam another array across the bottom row and upward, twiddling the spacing to match the subpixel block spacing along both axes
Which eventually looks like this:

SubPixels – LightBurn vector overlay

I made the final array absurdly large, cropped it with a square to match the template I used for the layered paper patterns, resized the result to be 170 mm on a side, then dropped the square into the middle of the template:

Subpixel Zoo – Quattron RGBY – LightBurn black mask layer

One gotcha: crop the subpixels on a Fill layer so LightBurn will close the truncated edges, then put them on a Line layer for cutting. The doc explains why, although it’s not obvious at first, as is the fact that you must delete the group of shapes outside the square before it looks like anything happened during the cut operation.

The resulting layout contains all the subpixel rectangles, so it’s what you want for the top black mask layer. Duplicate the pattern and delete the subpixels corresponding to each color, until you have one template for each of the Red / Green / Blue layers:

Subpixel Zoo – Quattron RGBY – LightBurn layers

The blank over on the right is the Yellow layer, which does get a quartet of layer ID holes cut in the lower right corner.

Then it’s just a matter of cutting the blanks, locating the fixture on the platform, dropping the appropriate color sheet in place, cutting it, then assembling the stack in the gluing fixture:

Subpixel Zoo – Quattron RGBY

It’s kinda cute, in a techie way.

I did a bunch of layouts, just to see what they looked like:

Subpixel Zoo – 8×8 layouts

In person, the RGBY patterns look bright and the RGB patterns seem dull by comparison. I’m using cardstock paper, rather than fancy art paper, which surely makes all the difference.
2025-03-07
Trivial Laser Projects

A nubbly knob on the M4 screws securing the honeycomb to the laser’s platform:

Honeycomb screw knob

Leveling feet for the HQ Sixteen long-arm machine’s table for the high side of the floor:

HQ Sixteen – table leg leveler – short

And 12 mm taller on the low side:

HQ Sixteen – table leg leveler – tall

Both of those “projects”, which may be too grand a term, went from “I need a thing” to having one in hand over the course of a few minutes yesterday. Neither required a great deal of thought, having previously worked out the proper speed / power settings to cut 3 mm MDF and 1 mm cork.

Other folks may lead you to believe lasers are all about fancy artwork and elaborate finished products. Being the type of guy who mostly fixes things, I’d say lasers are all about making small and generally simple parts, when and where they’re needed, to solve a problem nobody else has.

Perhaps I should devote more attention to using fancy wood with a hand-rubbed wax finish, but MDF fills my simple needs.

With a laser and a 3D printer, shop tools have definitely improved since the Bad Old Days!

2025-03-06

HQ Sixteen: Table Leveling Blocks

The Handi-Quilter HQ Sixteen rides on two tracks along the 11 foot length of the table, with an unsupported 8 foot span between the legs on each end:

HQ Sixteen - remounted handlebars in use — HQ Sixteen – remounted handlebars in use

Contemporary versions of the table have support struts in the middle that our OG version lacks and, as a result, our table had a distinct sag in the middle. During the course of aligning the table top into a plane surface with tapered wood shims, I discovered the floor was half an inch out of level between the table legs.

Now that the whole thing has settled into place, I measured the shim thicknesses and made tidy blocks to replace them:

HQ Sixteen - table shims - finished — HQ Sixteen – table shims – finished

The OpenSCAD code has an array with the thickness and the number of blocks:

SHIM_THICK = 0;
SHIM_COUNT = 1;

Shims = [
    [3.5,1],
    [5.0,3],
    [6.0,2],
    [6.5,1],
    [7.0,1]
];

Yes, I call them “blocks” here and wrote “shims” in the code. A foolish consistency, etc.

The model is a chamfered block with a chunk removed to leave a tongue of the appropriate thickness:

HQ Sixteen - table shims - solid model - single — HQ Sixteen – table shims – solid model

Building them with the label against the platform produces a nice nubbly surface:

HQ Sixteen - table shims - solid model — HQ Sixteen – table shims – PrusaSlicer – bottom

The labels print first and look lonely out there by themselves:

HQ Sixteen - table shims - legends — HQ Sixteen – table shims – legends

The rest of the first layer fills in around the labels:

HQ Sixteen - table shims - first layer — HQ Sixteen – table shims – first layer

Putting the labels on the bottom makes the wipe tower only two layers tall and eliminates filament changes above those layers. Those eight blocks still took a little over three hours, because there’s a lot of perimeter wrapped around not much interior.

Having had the foresight to draw a sketch showing where each block would go, I slid one next to its wood shim, yanked the shim out, and declared victory:

HQ Sixteen - table shims - installed — HQ Sixteen – table shims – installed

The tension rod welded under the table rail prevents even more sag, but the struts under the new version of the table show other folks were unhappy with the sag of this one. Another leg or two seems appropriate.

With the table leveled and the surface aligned, the HQ Sixteen glides easily in all directions. The result isn’t perfect and Mary keeps the anchor block at hand, but the machine now displays much less enthusiasm for rolling toward the middle of the table.

The OpenSCAD source code as a GitHub Gist:

	// HQ Sixteen – table shims
	// Ed Nisley – KE4ZNU
	// 2025-02-27

	include <BOSL2/std.scad>

	Layout = "Show"; // [Show,Build]

	/* [Hidden] */

	SHIM_THICK = 0;
	SHIM_COUNT = 1;

	Shims = [
	[3.5,1],
	[5.0,3],
	[6.0,2],
	[6.5,1],
	[7.0,1]
	];

	Block = [40.0,20.0,15.0]; // overall shim size
	Grip = 10.0; // … handle length

	BlockRadius = 1.0; // corner rounding / chamfer

	LabelThick = 0.4;
	LabelSize = 5.5;
	LabelFont = "Arial:style:Bold";
	LabelColor = "Red";

	Protrusion = 0.1;
	Gap = 5.0;

	//———-
	// Define shim shape

	module ShimBlock(Height = Shims[0][SHIM_THICK],Part="All") {

	if (Part == "Block" \|\| Part == "All")
	difference() {
	left(Grip)
	cuboid(Block,anchor=BOTTOM + LEFT,chamfer=BlockRadius);
	up(Height)
	cube(Block + 2*[Protrusion,Protrusion,0],anchor=BOTTOM + LEFT);

	left(Grip/2 – BlockRadius/2) fwd(Block.y/2 – LabelThick) up(Block.z/2)
	xrot(90) zrot(-90)
	linear_extrude(height=LabelThick + Protrusion,convexity=20)
	text(text=format_fixed(Height,1),size=LabelSize,spacing=1.00,
	font=LabelFont,halign="center",valign="center");
	}

	if (Part == "Text" \|\| Part == "All")
	color(LabelColor)
	left(Grip/2 – BlockRadius/2) fwd(Block.y/2 – LabelThick) up(Block.z/2)
	xrot(90) zrot(-90)
	linear_extrude(height=LabelThick,convexity=20)
	text(text=format_fixed(Height,1),size=LabelSize,spacing=1.00,
	font=LabelFont,halign="center",valign="center");

	}




	//———-
	// Build them all

	if (Layout == "Show")
	ShimBlock();

	if (Layout == "Build") {
	for (j=[0:len(Shims)-1])
	back(j*(Block.z + Gap))
	for (i=[0:(Shims[j][SHIM_COUNT] – 1)])
	right(i*(Block.x + Gap))
	up(Block.y/2) xrot(90)
	ShimBlock(Shims[j][SHIM_THICK],Part="Block");
	for (j=[0:len(Shims)-1])
	back(j*(Block.z + Gap))
	for (i=[0:(Shims[j][SHIM_COUNT] – 1)])
	right(i*(Block.x + Gap))
	up(Block.y/2) xrot(90)
	ShimBlock(Shims[j][SHIM_THICK],Part="Text");
	}

view raw HQ Sixteen – table shims.scad hosted with ❤ by GitHub

2025-03-04

HQ Sixteen: Ball-mounted Stylus Laser
Installing the new ball-mount laser stylus on the HQ Sixteen’s electronics pod required nothing more than two strips of good foam tape:

HQ Sixteen – Stylus Laser – installed – overview

In actual use, you would:
- Lay down a “pantograph” pattern on a paper strip along the rear track under the machine’s carriage
- Position the needle at the appropriate spot on the quilt
- Aim the laser at the corresponding point on the pattern
- Start the machine!
- Move the laser spot along the pattern while the machine stitches that pattern in the quilt
Mary thinks free-motion quilting is easier and I’m not in a position to argue the point.

Anyhow, the key feature of my ball mount is that it’s completely out of the way:

HQ Sixteen – Stylus Laser – installed – front

Which looks comfortingly like the original solid model:

HQ Sixteen – Stylus Laser Mount – solid model – show

Minus the vivid red death ray and pew! pew! pew!

Power comes from a barrel jack in the back intended for the original stylus laser; all small lasers, unless otherwise noted, run from 5 VDC. The jack is 3.5×1.3 mm, but the Drawer o’ Weird Barrel Plugs disgorged a matching right-angle plug. Unsurprisingly, such things are readily available these days.

Splice the laser leads to the plug and cover the evidence with a braided loom + heatshrink tubing:

HQ Sixteen – Stylus Laser – installed – rear

I considered a switch, but the anticipated low duty cycle suggested just unplugging it, so that’s that.

And It Just Worked™.

The backstory begins There and continues to now.
2025-03-03
HQ Sixteen: Stylus Laser Ball Drilling
With the ball mount in hand:

HQ Sixteen – Stylus Laser – ball clamp test fit

The next step is to drill a 12 mm hole for the red-dot laser module right through the middle of the 1 inch = 25.4 mm polypropylene ball.

I decided to use a more-or-less standard laser module, rather than the Genuine Handi-Quilter laser, because:
- Cheap & readily available
- Identical spares on hand
- Two decades of red laser diode progress
Start by conjuring a lathe chuck fixture for a 1 inch ball from my OpenSCAD model and printing it in PETG-CF:

HQ Sixteen – Stylus Laser – center drilling

Run a few drills through the ball up to 15/32 inch = 0.469 inch = 11.9 mm:

HQ Sixteen – Stylus Laser – final drilling

Which looks terrifying and was no big deal.

The laser module didn’t quite fit until I peeled off the label, as setting up a boring bar seemed like too much hassle for too little gain. The ball is slick polypropylene and the laser module is chromed plastic, which means there’s not much friction involved and a stiff fit is a Good Thing™.

I did not realize the hazy white patches barely visible inside the ball were voids / bubbles:

HQ Sixteen – Stylus Laser – drilled ball

Next time I’ll (try to) orient the patches toward the tailstock in hopes of simply drilling through them to leave solid plastic around the rim.

Ramming the laser in place makes it look like it grew there;

HQ Sixteen – Stylus Laser – laser test fit

The alert reader will note the lens projects a line, due to my not ordering any dot modules back when I got a bunch of these things. After all, who wants a plain dot when you can light up a line or even a crosshair?

Next, wire it up and stick it on the machine …
2025-02-28