Author: Ed

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

HQ Sixteen: Stylus Laser Ball Mount

My version of a mount for the HQ Sixteen’s “stylus laser” clamps a 1 inch polypropylene ball between two plates:

HQ Sixteen - Stylus Laser - ball clamp test fit — HQ Sixteen – Stylus Laser – ball clamp test fit

The plates have a sphere subtracted from them and a kerf sliced across the sphere’s equator for clamping room:

HQ Sixteen - Stylus Laser Mount - solid model — HQ Sixteen – Stylus Laser Mount – solid model

Given that this is a relatively low-stress situation, I embedded BOSL2 nuts to produce threads in the plate rather than use brass inserts.

The side plates start as simple rectangles:

HQ Sixteen - Stylus Laser Mount - solid model - mount sides — HQ Sixteen – Stylus Laser Mount – solid model – mount sides

Subtracting the electronics pod shape from those slabs matches them exactly to the curvalicious corner:

HQ Sixteen - Stylus Laser Mount - solid model - mount shaping — HQ Sixteen – Stylus Laser Mount – solid model – mount shaping

The weird angle comes from tilting the mount to aim the laser in roughly the right direction when perpendicular to the plates:

HQ Sixteen - Stylus Laser Mount - solid model - show — HQ Sixteen – Stylus Laser Mount – solid model – show

That angle can be 0° to 30°, although 25° seems about right. The slab sides neither stick out the top nor leave gaps in the corner over that range, after some cut-and-try ~~tinkering~~ sizing.

One of the M3 screws just did not want to go into its hole:

HQ Sixteen - Stylus Laser - threadless M3 screw — HQ Sixteen – Stylus Laser – threadless M3 screw

A bad day in the screw factory, I suppose.

The OpenSCAD source code as a GitHub Gist:

	// Handiquilter HQ Sixteen Stylus Laser Mount
	// Ed Nisley – KE4ZNU
	// 2025-02-23

	include <BOSL2/std.scad>
	include <BOSL2/threading.scad>

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

	/* [Hidden] */

	PodWidth = 110.0; // overall width of pod
	PodScrewClear = 50.0; // clear distance between pod screws
	PodRecenter = [0,0]; // pod trace upper corner to origin if not done in Inkscape

	BaseAngle = -25; // laser neutral angle

	BallOD = 25.4 + 0.2; // bearing ball + easy fit clearance
	BallOffset = [70.0,0,-35.0]; // upper corner to ball center

	LaserOD = 12.2; // laser module
	LaserLength = 38.0;

	Kerf = 1.0; // clamp gap
	Plate = [35.0,35.0,8.0 + Kerf]; // basic mount plate

	WallThick = 5.0; // upright walls: plate to pod

	WasherOD = 7.0;

	ScrewPitch = 0.5;
	ScrewNomOD = 3.0;
	ScrewNomID = ScrewNomOD – ScrewPitch;

	ScrewOC = Plate – [WasherOD,WasherOD,0];

	Gap = 5.0; // build spacing

	//———-
	// HQ Sixteen electronics pod

	module Pod() {

	xrot(90)
	down(PodWidth/2)
	linear_extrude(height=PodWidth,convexity=5)
	translate(PodRecenter)
	import("HQ Sixteeen – pod profile.svg",
	layer="Pod Profile");
	}

	module LaserPointer() {
	cylinder(d=LaserOD,h=LaserLength,center=true);
	}

	module Ball() {

	union() {
	sphere(d=BallOD,$fn=4*12);
	down(0.25*LaserLength)
	LaserPointer();
	}
	}

	module Mount() {

	union() {
	difference() {
	union() {
	cuboid(Plate,anchor=CENTER);
	for (j=[-1,1])
	translate([-(BallOffset.x – Plate.x)/2,j*(Plate.y + WallThick)/2,Kerf/2])
	cuboid([BallOffset.x,WallThick,-0.75*BallOffset.z],anchor=BOTTOM);
	}
	cuboid([4Plate.x,4Plate.y,Kerf],anchor=CENTER);
	Ball();
	for (i=[-1,1], j=[-1,1])
	translate([iScrewOC.x/2,jScrewOC.y/2,0])
	cylinder(d=1.2ScrewNomOD,h=2Plate.z,anchor=CENTER,$fn=6);

	yrot(-BaseAngle)
	translate(-BallOffset)
	Pod();

	}


	for (i=[-1,1], j=[-1,1])
	translate([iScrewOC.x/2,jScrewOC.y/2,Kerf/2])
	// flat size root dia height pitch
	threaded_nut(1.5*ScrewNomOD,ScrewNomID,(Plate.z – Kerf)/2,ScrewPitch,$slop=0.10,
	bevel=false,ibevel=false,anchor=BOTTOM);
	}
	}

	//———-
	// Build things

	if (Layout == "Pod")
	Pod();

	if (Layout == "Mount")
	Mount();


	if (Layout == "Show") {
	yrot(BaseAngle) {
	color("SteelBlue")
	Mount();
	color("Magenta",0.5)
	Ball();
	color("Red")
	yrot(180)
	cylinder(d=2,h=-2*BallOffset.z,$fn=12);

	}
	translate(-BallOffset)
	color("Silver",0.8)
	Pod();
	}

	if (Layout == "Build") {
	left(Plate.x/2 + Gap/2)
	intersection() {
	cuboid([4Plate.x,4Plate.y,-BallOffset.z],anchor=DOWN);
	down(Kerf/2)
	Mount();
	}

	right(Plate.x/2 + Gap/2)
	intersection() {
	cuboid([4Plate.x,4Plate.y,Plate.z/2],anchor=DOWN);
	up(Plate.z/2)
	Mount();
	}
	}

view raw HQ Sixteen – Stylus Laser Mount.scad hosted with ❤ by GitHub

2025-02-27

HQ Sixteen: Electronics Pod Solid Model
The HQ Sixteen came with a small red-dot laser pointer attached to a threaded pin:

HQ Sixteen – Stylus Laser Mount – OEM version

The pin can go into either of a pair of threaded holes in the machine castings or the laser + clamp can, as in the picture, attach to a spool pin.

With a “pantograph” pattern laid along the rear of the table, you can stitch that design (at full size, hence “pantograph” seems aspirational) by guiding the red dot along the lines. The laser’s flimsy clamp mount seems prone to move at the worst possible moment, so neither of us liked the idea.

Mary is good at free-motion quilting and says she’s unlikely to use the laser, but I figured staying slightly ahead of the curve would be a Good Idea. Bonus: 3D printing.

The general idea is to tuck a (similar) red-dot laser module under the overhang of the electronics pod, with a ball mount for easy aiming and stable setting, something like this:

HQ Sixteen – Stylus Laser Mount – solid model – show

Fitting the mount into that curved corner requires a model of the electronics pod, so I held a pad of paper against the pod and traced the outline:

HQ Sixteen – pod profile trace

Scan it, import the image into Inkscape, fit lines and curves around the shape:

HQ Sixteen – pod outline – Inkscape

I only needed the top of the pod, so the bottom is truncated from the actual 250 mm height.

Save the SVG, import into OpenSCAD, extrude to match the pod’s 110 mm width:
```
module Pod() {

    xrot(90)
    down(PodWidth/2)
        linear_extrude(height=PodWidth,convexity=5)
            translate(PodRecenter)
                import("HQ Sixteeen - pod profile.svg",
                        layer="Pod Profile");
}
```
The model origin is where the upper lip meets the slightly sloped top surface in the middle of the extrusion, because that’s the only easy-to-locate feature:

HQ Sixteen – Stylus Laser Mount – electronics pod – solid model

Something Has Changed in the Inkscape SVG → OpenSCAD model chain, because the parts of an Inkscape drawing lying outside the page boundary are no longer cropped from the OpenSCAD model. Now, simply putting a feature at the Inkscape origin at the lower-left corner of the document’s Page produces a complete OpenSCAD 2D shape with that feature at the 3D coordinate origin.

For reference:
- Inkscape v1.4
- OpenSCAD 2025-02-11 via AppImage
The Inkscape layout with the entire shape off the page:

HQ Sixteeen – pod profile – Inkscape origin

The 2D imported shape in OpenSCAD with a matching origin:

HQ Sixteeen – pod profile – Inkscape origin

I do not know what changed or if, in fact, my misunderstanding of how things worked required the previous workaround, but this is much better. The OpenSCAD code includes a [0,0] offset value, should you need it.

More on the mount tomorrow …
2025-02-26
OMTech 60 W Laser: Engraving Wobbulation
Continuing the experiments on Y axis wobbling produced this shaky engraving:

Engraving – 100mm-s 0.25mm interval 9pct

The rectangle is 30×10 mm, with lines spaced 0.25 mm apart to simplify estimating distances (although I also have a measuring magnifier) and run at 100 mm/s to simplify converting distance to time. The lines alternate in direction, beginning with a left-to-right line at the bottom (which is bar-straight from the initial positioning move). The wobbles occur at the start of each line.

A closer look with blown contrast:

Engraving – 100mm-s 0.25mm interval 9pct – detail

The maximum error in the Y axis direction looks like 0.12 mm and damps out after 3 cycles. Each cycle covers 2.8 mm = 28 ms = 35 Hz.

The LightBurn Preview shows a 1.5 mm overscan distance and extrapolating the wobbulations leftward suggests the gantry starts the scan line with an overshoot due to the Y axis motion. The cycle-to-cycle damping is about 50%, so the initial overshoot (invisible in the overscan region) might be 0.25 mm, agreeing reasonably well with the 0.2 mm seen while cutting small squares.

The results above come from these settings:
- Layer speed: 100 mm/s
- Line interval: 0.25 mm
- Y acceleration: 2000 mm/s²
- Y start speed: 20 mm/s
I then made single-variable changes to the Engraving Parameters settings:

Line shift speed
- 500 mm/s
- 10 mm/s
Y Acceleration
- 200 mm/s²
Y start speed
- 30 mm/s
Today I Learned: The Y Start Speed (in mm/s) for engraving is capped by the Y Axis Jumpoff Speed (in mm/s², so perhaps the maximum change in speed), which is, in turn, capped at 80 mm/s.

Each of the variations produced a result visually indistinguishable from the image you see above: the error magnitude and oscillation frequency were identical.
One possible reason: None of those settings have any effect, because LightBurn doesn’t do whatever the Ruida controller defines as Engraving. However, changing both the Y start speed and the Jumpoff speed should have made at least a little change to the results and did not.

Another possible reason: Each 0.25 mm Y axis change requires 20.8 motor steps (either 20 or 21 at 12 µm/step), so the fancy tweaks lack space to take effect, the motor thumps 20-ish steps, and the gantry shakes the same way every time.

The closer you look, the worse it gets …
2025-02-25
Ooma Telo2: Speaker2 Failure

After not quite six years, the replacement speaker I hacked into our Ooma Telo2 VOIP gadget failed:

Ooma Telo 2 – replacement speaker installed

Quite by coincidence, a few days earlier a friend reported the speaker in her Ooma Telo2 had failed. This seems to be a common failure mode, with the rest of the gadget continuing to work fine.

The failed speaker showed continuity through its coil and, in fact, still had the same 8 Ω DC resistance as an identical speaker pulled from the Drawer o’ Small Speakers. It did not, however, make a sound when connected to a signal generator, where the new speaker squeaked happily.

So it seems the speaker failed by a mechanical jam, rather than an electrical / wiring failure. It’s not as though we play thrash metal music through the thing, but apparently the magnet disintegrated:

Samsung speaker magnet disintegration

Yes, the coil gap is full of nicely oriented magnetic particles:

Samsung speaker magnet disintegration – detail

If Samsung (or whoever built the speaker) used a poorly sealed neodymium magnet, then it would crumble exactly as shown.

I wonder if that’s how the original speaker failed.

Installing the identical replacement speaker involved more hot melt glue and, as expected, restored the Telo2 to normal operation:

Ooma Telo – second speaker installed

I can do that repair eight more times …

2025-02-24
OMTech 60 W Laser: Speed vs. Corner Radius Wobbulation

Experimenting with little squares showed the Y axis has a definite wobble:

Subpixel Zoo – Quattron RGBY Shifted – detail

Which suggested a simple test:

Cornering – overview

I adjusted the laser power to compensate for the speed, with the result being a line burned into white cardboard. The lines are a bit under 0.2 mm wide, roughly the width of the focused spot.

The controller settings for the X and Y axes:

KT332N – X Y Axis Parameters – 2025-02-18

The acceleration values may be affected by the limits in this section:

KT332N – Cut Engraving Parameters – 2025-02-18

Assuming the Y axis acceleration is 3000 mm/s², the RepRap calculator shows the Y axis speeds within the 30 mm distance along the vertical sides:

RepRap Accel Calculator – 3000mm-s2 30mm

Extracting the useful bits and lining them up for comparison:

Cornering – detail

The first column in the test results shows perfectly square corners have no problem at any speed, because the controller decelerates to nearly a stop before changing direction.

Rounding the corner to 0.5 mm introduces a distinct wobble in the Y axis that doesn’t change much, probably because the controller still decelerates as it approaches the corner.

The 1 mm radius corners show a distinct overshoot at all speeds. The peak overshoot doesn’t change much between 250 and 500 mm/s, because the RepRap calculator shows the machine barely reaches 250 mm/s by the middle of the side, so 500 mm/s isn’t any faster.

The first overshoot is about 0.2 mm, the first undershoot is a little over 0.1 mm, and the rest are barely visible.

The 2 and 4 mm radius corners have barely visible wobbles. Whether that is due to the head not flexing as much due to the lower acceleration around the larger radius I cannot say.

The machine may not follow the simple RepRap acceleration profile when approaching a corner, let alone a rounded corner.

I think attempting to reduce the overshoot by fiddling with the belt tension / hardware fasteners / whatever will be unavailing. The laser head runs on a linear rail along the gantry with plenty of unbalanced mass hanging off the bottom:

OMTech 60W beam alignment – head X plane

Moving the beam 0.2 mm on the platform by pivoting around the rail 6 inch = 150 mm above amounts to only 0.08°, far less than anything I can measure while adjusting the mechanics.

Slowing down doesn’t help nearly as much as I expected and rounding the corners makes it worse.

Word has it that much spendier machines behave better, which is both comforting and unhelpful.

2025-02-21