Category: Machine Shop

Mechanical widgetry

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
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
HQ Sixteen: Wheel Base Leveling

Trying out the Track Lock Blocks brought a long-standing puzzle to the surface: the left front wheel rode about a millimeter above its track, with the other three wheels carrying the weight of the machine. Neither that wheel nor the diagonally opposite wheel on the right rear worked well with the Blocks, because the machine rocked on the other two wheels.

I initially thought the carriage rail under the machine was warped, but some poking and prodding showed the left front wheel rode higher than the others from front to back across the entire length of the table.

So I loosened the screws holding the front wheel base plate to the machine and jacked up the front of the machine to get the wheels off their tracks:

HQ Sixteen – track lock – jacking machine

Then I jammed two strips of chipboard into the left side of the gap:

HQ Sixteen – front wheel base plate shim

I planned to use one long strip across the entire wheel base plate, but the screw holding the machine casting to the plate blocks the way, so it now has two shorter strips. Tightening the screws clamped the chipboard in place.

The chipboard tilted the base plate and lowered the left wheel, with the right wheel surely moving slightly upward. Lowering the machine showed both front wheels now carry roughly the same load and the Track Lock Blocks now work the way I expected.

After doing that, I found the recommended procedure in the official HQ Sixteen Service and Troubleshooting manual:

HQ Sixteen – Wheel base shim procedure

The only “planed surface” around here is on the surface plate in the Basement Shop, two flights of stairs away, and I am not carrying either object to meet the other.

In any event, I think the chipboard serves the same purpose as a simple washer, with advantage of a much larger bearing surface, so I’ll call it Good Enough until something else causes me to take the wheel base plate off.

2025-02-19

HQ Sixteen: Track Lock Blocks

Mary’s practice quilts on the HQ Sixteen suggest locking the machine’s wheels will simplify sewing a line parallel to the long edge of a quilt parallel to the table, but contemporary “Channel Locks” fit newer machines with larger wheels than on this one.

Duplicating those rings in a smaller size seemed both difficult and not obviously functional, so I built a pair of blocks to capture the wheel on its track:

HQ Sixteen - track lock - engaged — HQ Sixteen – track lock – engaged

The wheel sits in a recess holding it just barely above the track surface, so the (considerable) weight of the machine holds the block in place.

Because lines on quilts have precise placement and Mary has quilting rulers within reach, the block measures exactly two inches from the point where it first touches the wheel to the center of the recess:

HQ Sixteen - track lock - setup — HQ Sixteen – track lock – setup

She can then lay a ruler on the quilt, roll the machine front or back two inches, slide a block against each wheel, then roll the machine up a slight incline until the wheel drops into the recess:

HQ Sixteen - track lock block - solid model — HQ Sixteen – track lock block – solid model

The spacing looks like this:

HQ Sixteen - track lock block - solid model - show view — HQ Sixteen – track lock block – solid model – show view

The usual 3D printing process puts 0.2 mm steps along the ramp, but they’re almost imperceptible while rolling the machine:

HQ Sixteen - track lock block - PrusaSlicer preview — HQ Sixteen – track lock block – PrusaSlicer preview

The ramp slope is all of 1:20 = 2.5°, so pulling / pushing the machine requires very little oomph.

I put thin cloth tape (approximately friction tape, but with real adhesive) on the bottom of the block by the simple expedient of sticking it to the block and scissoring off the excess. A little compliance between the block and the track prevents the hard plastic shapes from sliding more easily than I’d like. If your tape is thicker than mine, knock a little off the WheelZ value.

The OpenSCAD code can produce shapes to laser-cut an adhesive sheet, although stacking a foam sheet will definitely require height adjustment :

HQ Sixteen - track lock block - glue sheet — HQ Sixteen – track lock block – glue sheet

The OpenSCAD source code as a GitHub Gist:

	// HQ Sixteen – wheel track lock block
	// Ed Nisley – KE4ZNU
	// 2025-02-14

	include <BOSL2/std.scad>

	Layout = "Show"; // [Show,Build,Glue,Track,Block,Wheel]

	/* [Hidden] */

	ID = 0;
	OD = 1;
	LENGTH = 2;

	Protrusion = 0.1;
	Windage = 0.1;

	WallThick = 5.0; // minimum wall thickness

	RailOD = 5.5; // rounded top of rail
	RailHeight = RailOD; // … flange to top
	RailBase = [100,2*15.7 + RailOD,3]; // … Y = flange width, arbitrary X & Z

	WheelOD = 38.0; // rail roller
	WheelMinor = 6.2; // … rail recess
	WheelWidth = 8.3 + 2*Windage; // … outer sides
	WheelZ = RailHeight + (WheelOD – WheelMinor)/2; // axle centerline wrt rail flange

	LockOC = 2.0*INCH; // engagement to lock recess

	GripLength = 20.0;

	BlockOA = [GripLength + WheelOD/2 + LockOC,WheelWidth + 2WallThick,2RailHeight];
	BlockRadius = 2.0;

	$fn = 1234; // smooth outer perimeters

	//———-
	// Construct the pieces

	module Track(Len = 2*BlockOA.x) {

	zrot(90) back(Len/2) down(RailBase.z) xrot(90)
	linear_extrude(height=Len,convexity=5)
	rect([RailBase.y,RailBase.z],anchor=FRONT)
	attach(BACK,FRONT) rect([RailOD,RailHeight – RailOD/2])
	attach(BACK) circle(d=RailOD);
	}

	module Wheel(Len = WheelWidth) {

	xrot(90)
	difference() {
	cylinder(d=WheelOD,h=Len,center=true);
	torus(r_maj=WheelOD/2,d_min=WheelMinor);
	}
	}

	module Block() {

	difference() {
	left(GripLength + WheelOD/2)
	cuboid(BlockOA,anchor=LEFT + BOTTOM,rounding=BlockRadius,except=BOTTOM);
	Track();
	up(WheelZ) xrot(90)
	cylinder(d=WheelOD,h=WheelWidth,center=true);
	right(LockOC)
	up(WheelZ – WheelOD/2) yrot(atan((RailHeight – WheelMinor/2)/LockOC))
	cuboid([LockOC,WheelWidth,BlockOA.z],anchor=RIGHT+BOTTOM);
	}
	}


	//———-
	// Show & build the results

	if (Layout == "Block" \|\| Layout == "Build")
	Block();

	if (Layout == "Track")
	Track();

	if (Layout == "Wheel")
	Wheel();

	if (Layout == "Glue")
	projection(cut=true)
	Block();

	if (Layout == "Show") {

	color("SteelBlue")
	Block();
	for (i=[0,1])
	right(i*LockOC)
	color("Silver",0.7)
	up(WheelZ) Wheel();
	color("White",0.5)
	Track();
	}

view raw HQ Sixteen – track lock block.scad hosted with ❤ by GitHub

2025-02-18

Drive Wheelchair Foot Rest Lubrication

After few days in the Drive Blue Streak wheelchair, I finally lubricated the foot rest pivots:

Drive wheelchair foot rest lubrication

The complex molded rests gripped their metal tubes so tightly as be nearly immovable, but one drop of Kroil at the four obvious spots let them turn much more easily.

The flange overlapping the upright tube along the bottom of the picture hits the short protrusion and holds the rest parallel to the floor. A screw at the plastic cap near the top keeps the rests from working their way too far from the upright tube.

I can make it to the Basement Shop™ and back, paying careful attention to detail.

2025-02-17

Category: Machine Shop

HQ Sixteen: Stylus Laser Ball Mount

HQ Sixteen: Electronics Pod Solid Model

OMTech 60 W Laser: Engraving Wobbulation

OMTech 60 W Laser: Speed vs. Corner Radius Wobbulation

HQ Sixteen: Wheel Base Leveling

HQ Sixteen: Track Lock Blocks

Drive Wheelchair Foot Rest Lubrication