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.

Tag: M2

Using and tweaking a Makergear M2 3D printer

Makergear M2: New Nozzle

A second clog in the M2’s hot end prompted me to dismantle the hot end:

Makergear M2 V4 hot end – eroded silicone coat

That’s what half a year of use does to a nice, shiny coat of high-temperature silicone rubber.

This being the first time I’ve dismantled the hot end, here’s what lies inside:

Makergear M2 V4 hot end – tapered inner guide

The tighter you make the nozzle, the closer the fit inside the hot end, and the more heat gets transferred to the plastic. The bright ring just to the right of the plastic drool shows where it fits into the brass nozzle.

Peeling the remaining silicone off the nozzle, scraping off the black PETG around the tip, and scraping the gunk out left the inside a bit scuffed:

Makergear 0.35 mm nozzle – interior

The orifice still looks good and is still as close to 0.35 mm as I can measure eyeballometrically:

Makergear 0.35 mm nozzle – exterior

Despite what it looks like, that’s actually a very thin PETG layer.

Having a spare nozzle on the shelf, I decided to install it and leave the old nozzle as a backup. I’ve probably wrecked the snug seal required to keep the plastic out of the hot end.

A fresh coat of silicone, reset the position with the platform at Z=0, and it’s back in action:

Makergear M2 V4 hot end – Z zero set

The PETG remnants show I didn’t get the nozzle quite tight enough on the first attempt, but it’s all good now. The rubbery fiberglass insulator will conceal the mess.

Protip: Always remove the hot end from the printer and clamp it securely before unscrewing the nozzle, because the very thin heat break (over on the right in the second picture) will snap under less torque than you need to break the nozzle free.

You should unscrew the nozzle with the hot end warm enough to soften whatever plastic you’re using, lest it have glued everything inside into a solid lump.

2020-12-10

Drive Wheelchair Brake Knob

The bent-steel brake levers on our Drive Blue Streak wheelchair present themselves edge-on to the rider:

There are good mechanical reasons for shaping and orienting the steel like that, but the handle concentrates the considerable force required to push the brake tab into the rubberoid tire on your (well, my) palms. After a couple of weeks, I decided I didn’t need two more sore spots and conjured a palm-filling knob from the vasty digital deep:

Wheelchair Brake Knob - installed — Wheelchair Brake Knob – installed

Bonus part: the little octagon near the wheel prevents the leg rest (seen in the first picture) from smashing into the end of the brake tab and chipping the lovely blue powder coat. The brown fuzzy felt foot seemed like a good idea at the time, but isn’t strictly necessary.

A cylindrical handle on Thingiverse apparently fits on the bare steel underneath the rubberish “cushion”, but cutting a perfectly good, albeit uncomfortable, cushion off seemed like a step in the wrong direction. My knob thus descends from a doodle of the OEM dimensions:

Drive Wheelchair Brake Handle - dimensions — Drive Wheelchair Brake Handle – dimensions

The knob builds in two halves adjoining the bonus octagon, which stands on edge to eliminate support inside its slot:

Wheelchair Brake Mods - solid model - build layout — Wheelchair Brake Mods – solid model – build layout

You (probably) need two of all those shapes, a job your slicer is ready to perform. At three hours for each knob, I just printed the same G-Code twice.

You can customize the knob width to fit your palm, with the other two dimensions fitting themselves around the cushion. Mary and I settled on a knob size that fits both our hands reasonably well, so it’s probably not critical.

I tried building the knob halves without support for the first prototype, but the sloped upper surface produced awful bridging:

Wheelchair Brake Knob - unsupported interior — Wheelchair Brake Knob – unsupported interior

It’s easy enough to design a customized support structure:

Wheelchair Brake Mods - cross section — Wheelchair Brake Mods – cross section

I oriented the knob to put the split on the narrow sides of the brake handle in order to not have a seam facing my palm:

Wheelchair Brake Knob - rear half installed — Wheelchair Brake Knob – rear half installed

The quartet of M3×20 mm socket-head cap screws thread into brass inserts epoxied into the rear half. I recessed their heads deeply into the front half and avoided thinking too hard about plugs matching the surface curvature:

Wheelchair Brake Knob - front view — Wheelchair Brake Knob – front view

The low-vertex-count polygonal shape is a stylin’ thing and produces a nice feel during a firm shove, at least to my paws. Although I’d rather not need a wheelchair at all, setting the brakes now seems authoritative instead of annoying.

The OpenSCAD source code as a GitHub gist:

	// Pride wheelchair brake lever mods
	// Ed Nisley KE4ZNU 2020-11

	/* [Layout options] */

	Layout = "Build"; // [Build, Show, Fit, TabCap, Handle, Knob, Support]

	// Hold up the knob's inside
	Support = true;

	/* [Extrusion parameters] */

	/* [Hidden] */

	ThreadThick = 0.25;
	ThreadWidth = 0.40;

	HoleWindage = 0.2;

	function IntegerMultiple(Size,Unit) = Unit * ceil(Size / Unit);
	function IntegerLessMultiple(Size,Unit) = Unit * floor(Size / Unit);

	Protrusion = 0.1; // make holes end cleanly

	inch = 25.4;

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

	//———————-
	// Useful routines

	module PolyCyl(Dia,Height,ForceSides=0) { // based on nophead's polyholes

	Sides = (ForceSides != 0) ? ForceSides : (ceil(Dia) + 2);

	FixDia = Dia / cos(180/Sides);

	cylinder(r=(FixDia + HoleWindage)/2,h=Height,$fn=Sides);
	}



	//* [Basic dimensions] */

	WallThick = 4.0; // min wall thickness

	Screw = [3.0,5.5,20.0]; // thread, head, length under head
	Insert = [3.0,4.1,8.0]; // thread, knurl, length

	//———————-
	// Brake tab cap

	BrakeTab = [15,21,3.1]; // length to wheel, width, thickness
	BrakeTabSagitta = 8.0; // height of curved endcap

	CapOAL = [BrakeTab.y + 2WallThick,BrakeTab.y + 2WallThick,BrakeTab.z + 2*WallThick];

	module TabCap() {

	difference() {
	rotate(180/8)
	cylinder(d=CapOAL.y,h=CapOAL.z,center=true,$fn=8);
	translate([BrakeTab.x/2,0,0])
	cube(BrakeTab,center=true);
	rotate(180/8)
	cylinder(d=BrakeTab.y/cos(180/8),h=BrakeTab.z,center=true,$fn=8);
	}
	}

	//———————-
	// Brake lever handle
	// Soft covering with rounded sides that we square off for simplicity

	HandleRibs = [15,34,14]; // ignoring slight taper from end
	HandleCore = [50.0,24.0,12.0]; // straight section of lever to top of ribs
	HandleTipWidth = 30.0; // ignoring actual sector height

	module Handle() {

	union() {
	hull() {
	rotate(180/8)
	cylinder(d=HandleTipWidth/cos(180/8),h=HandleCore.z,center=true,$fn=8);
	translate([-HandleCore.x/2,0,0])
	cube(HandleCore,center=true);
	}
	translate([-(3*HandleCore.x/2 – Protrusion),0,0]) // extend base for ball trimming
	cube(HandleCore,center=true);
	translate([-HandleRibs.x/2,0,0])
	cube(HandleRibs,center=true);
	}

	}

	//———————-
	// Support structure for handle cavity inside knob
	// Totally ad-hoc tweakage
	// Remember it's lying on its side to match the handle

	NumRibs = 2 + 1; // must be odd
	RibSpace = floor(HandleCore.z/(NumRibs + 1));

	module KnobSupport() {

	color("Yellow") { // support overlaps in the middle
	render(convexity=3)
	intersection() {
	for (k=[-1,1])
	translate([0,k*ThreadThick,0]) // shrink inward to break adhesion
	Handle();

	translate([(HandleCore.x – HandleRibs.x)/2 – HandleCore.x – Protrusion,0,0])
	cube([HandleCore.x – HandleRibs.x,HandleRibs.y,HandleCore.z],center=true);

	union()
	for (k=[-floor(NumRibs/2):floor(NumRibs/2)])
	translate([0,0,k* RibSpace])
	cube([2HandleCore.x,HandleRibs.y,2ThreadWidth],center=true);
	}

	translate([(HandleCore.x – HandleRibs.x)/2 – HandleCore.x,0,0])
	cube([HandleCore.x – HandleRibs.x,4ThreadWidth,NumRibsRibSpace],center=true);
	}
	}

	//———————-
	// Brake handle knob
	// Largely built with magic numbers
	// Includes support because it's not really optional

	KnobOD = 55.0;
	KnobOffset = HandleRibs.x/1;

	KnobSides = 243;

	module Knob() {

	difference() {
	hull() {
	resize([0,HandleRibs.y + 4*WallThick,HandleCore.x + HandleTipWidth/2 + WallThick])
	sphere(d=KnobOD,$fn=KnobSides);
	}

	translate([0,0,KnobOffset])
	rotate([0,-90,0])
	Handle();

	for (i=[-1,1],k=[-1,1])
	translate([iKnobOD/4,0,kKnobOD/4]) {
	rotate([90,0,0])
	PolyCyl(Insert[OD],1.5*Insert[LENGTH],6);
	translate([0,-Screw[LENGTH]/2,0])
	rotate([-90,0,0])
	PolyCyl(Screw[ID],KnobOD,6);
	translate([0,Screw[LENGTH] – Insert[LENGTH],0])
	rotate([-90,0,0])
	PolyCyl(Screw[OD],KnobOD,6);
	}
	}

	if (Support)
	translate([0,0,KnobOffset])
	rotate([0,-90,0])
	KnobSupport();

	}

	//———————-
	// Lash it together

	if (Layout == "TabCap") {
	TabCap();
	}

	if (Layout == "Handle") {
	Handle();
	}

	if (Layout == "Support") {
	KnobSupport();
	}

	if (Layout == "Knob") {
	Knob();
	}

	if (Layout == "Show") {
	translate([60,0,0])
	TabCap();
	Knob();
	}

	if (Layout == "Fit") {
	translate([60,0,0])
	difference() {
	TabCap();
	translate([0,0,CapOAL.z/2])
	cube(CapOAL,center=true);
	}
	difference() {
	Knob();
	translate([KnobOD + KnobOD/4,0*KnobOD,0])
	cube(2*KnobOD,center=true);
	translate([-KnobOD,-KnobOD,0])
	cube(2*KnobOD,center=true);
	}
	}

	if (Layout == "Build") {
	translate([KnobOD/2,0,(CapOAL.y*cos(180/8))/2])
	rotate([0,-90,90])
	TabCap();

	for (j=[-1,1])
	translate([0,-j0.75HandleCore.x,0])
	difference() {
	rotate([j*90,0,0])
	Knob();
	translate([0,0,-KnobOD])
	cube(2*KnobOD,center=true);
	}

	}

view raw Wheelchair Brake Mods.scad hosted with ❤ by GitHub

A doodle with dimensions of other parts:

Drive Wheelchair - brake footrest tab dimensions — Drive Wheelchair – brake footrest tab dimensions

The angled tab on the middle left is for the leg rest release latch, but I decided not to silk-purse-ize the thing.

2020-12-08

Astable Multivibrator: Dressed-up LED Spider

Adding a bit of trim to the bottom of the LED spider makes it look better and helps keep the strut wires in place:

Astable Multivibrator – Alkaline – Radome trim

It’s obviously impossible to build like that, so it’s split across the middle of the strut:

Astable Multivibrator – Alkaline – Radome trim

Glue it together with black adhesive and a couple of clamps:

LED Spider – glue clamping

The aluminum fixtures (jigs?) are epoxied around snippets of strut wire aligning the spider parts:

LED Spider – gluing fixture

Those grossly oversized holes came pre-drilled in an otherwise suitable aluminum rod from the Little Tray o’ Cutoffs. I faced off the ends, chopped the rod in two, recessed the new ends, and declared victory. Might need better ones at some point, but they’ll do for now.

Next step: wire up an astable with a yellow LED to go with the green and blue boosted LEDs.

2020-11-26
Kenmore Progressive Vacuum Cleaner vs. Dust Brush Adapters

Contemporary vacuum cleaner dust brush heads have bristles in some combination of [long | short] with [flexy | stiff]. The long + flexy combination results in the bristles jamming the inlet and the short + stiff combo seems unsuited for complex surfaces. Shaking the Amazonian dice brought a different combination:

Vacuum cleaner dust brush assortment – with adapters

That’s the new one on the bottom and, contrary to what you might think from the picture, it is not identical to the one just above it.

In particular, the black plastic housing came from a different mold (the seam lines are now top-and-bottom) and required a new adapter for the Kenmore Progressive vacuum cleaner’s complicated wand / hose inlet, with a 3/4 inch PVC pipe reinforcement inside.

Early reports indicate it works fine, so I’ll declare a temporary victory in the war on entropy.

I’m still using the same OpenSCAD source code with minute tweaks to suit the as-measured tapers.

2020-10-04

Raspberry Pi HQ Camera Mount

As far as I can tell, Raspberry Pi cases are a solved problem, so 3D printing an intricate widget to stick a Pi on the back of an HQ camera seems unnecessary unless you really, really like solid modeling, which, admittedly, can be a thing. All you really need is a simple adapter between the camera PCB and the case of your choice:

HQ Camera Backplate - OpenSCAD model — HQ Camera Backplate – OpenSCAD model

A quartet of 6 mm M2.5 nylon spacers mount the adapter to the camera PCB:

RPi HQ Camera - nylon standoffs — RPi HQ Camera – nylon standoffs

The plate has recesses to put the screw heads below the surface. I used nylon screws, but it doesn’t really matter.

The case has all the right openings, slots in the bottom for a pair of screws, and costs six bucks. A pair of M3 brass inserts epoxied into the plate capture the screws:

RPi HQ Camera - case adapter plate - screws — RPi HQ Camera – case adapter plate – screws

Thick washers punched from an old credit card go under the screws to compensate for the case’s silicone bump feet. I suppose Doing the Right Thing would involve 3D printed spacers matching the cross-shaped case cutouts.

Not everyone agrees with my choice of retina-burn orange PETG:

RPi HQ Camera - 16 mm lens - case adapter plate — RPi HQ Camera – 16 mm lens – case adapter plate

Yes, that’s a C-mount TV lens lurking in the background, about which more later.

The OpenSCAD source code as a GitHub Gist:

	// Raspberry Pi HQ Camera Backplate
	// Ed Nisley KE4ZNU 2020-09

	//– Extrusion parameters

	/* [Hidden] */

	ThreadThick = 0.25;
	ThreadWidth = 0.40;

	HoleWindage = 0.2;

	function IntegerMultiple(Size,Unit) = Unit * ceil(Size / Unit);
	function IntegerLessMultiple(Size,Unit) = Unit * floor(Size / Unit);

	Protrusion = 0.1; // make holes end cleanly

	inch = 25.4;

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

	//- Basic dimensions

	CamPCB = [39.0,39.0,1.5]; // Overall PCB size, plus a bit
	CornerRound = 3.0; // … has rounded corners

	CamScrewOC = [30.0,30.0,0]; // … mounting screw layout
	CamScrew = [2.5,5.0,2.2]; // … LENGTH = head thickness

	Standoff = [2.5,5.5,6.0]; // nylon standoffs

	Insert = [3.0,4.0,4.0];

	WallThick = IntegerMultiple(2.0,ThreadWidth);
	PlateThick = Insert[LENGTH];

	CamBox = [CamPCB.x + 2*WallThick,
	CamPCB.y + 2*WallThick,
	Standoff.z + PlateThick + CamPCB.z + 1.0];

	PiPlate = [90.0,60.0,PlateThick];
	PiPlateOffset = [0.0,(PiPlate.y – CamBox.y)/2,0];

	PiSlotOC = [0.0,40.0];
	PiSlotOffset = [3.5,3.5];

	NumSides = 234;

	TextDepth = 2*ThreadThick;

	//———————-
	// Useful routines

	module PolyCyl(Dia,Height,ForceSides=0) { // based on nophead's polyholes

	Sides = (ForceSides != 0) ? ForceSides : (ceil(Dia) + 2);

	FixDia = Dia / cos(180/Sides);

	cylinder(r=(FixDia + HoleWindage)/2,h=Height,$fn=Sides);
	}


	//———————-
	// Build it

	difference() {

	union() {
	hull() // camera enclosure
	for (i=[-1,1], j=[-1,1])
	translate([i(CamBox.x/2 – CornerRound),j(CamBox.y/2 – CornerRound),0])
	cylinder(r=CornerRound,h=CamBox.z,$fn=NumSides);
	translate(PiPlateOffset)
	hull()
	for (i=[-1,1], j=[-1,1]) // Pi case plate
	translate([i(PiPlate.x/2 – CornerRound),j(PiPlate.y/2 – CornerRound),0])
	cylinder(r=CornerRound,h=PiPlate.z,$fn=NumSides);
	}

	hull() // camera PCB space
	for (i=[-1,1], j=[-1,1])
	translate([i(CamPCB.x/2 – CornerRound),j(CamPCB.y/2 – CornerRound),PlateThick])
	cylinder(r=CornerRound,h=CamBox.z,$fn=NumSides);

	translate([0,-CamBox.y/2,PlateThick + CamBox.z/2])
	cube([CamScrewOC.x – Standoff[OD],CamBox.y,CamBox.z],center=true);

	for (i=[-1,1], j=[-1,1]) // camera screws with head recesses
	translate([iCamScrewOC.x/2,jCamScrewOC.y/2,-Protrusion]) {
	PolyCyl(CamScrew[ID],2*CamBox.z,6);
	PolyCyl(CamScrew[OD],CamScrew[LENGTH] + Protrusion,6);
	}

	for (j=[-1,1]) // Pi case screw inserts
	translate([0,j*PiSlotOC.y/2 + PiSlotOffset.y,-Protrusion] + PiPlateOffset)
	PolyCyl(Insert[OD],2*PiPlate.z,6);

	translate([-PiPlate.x/2 + (PiPlate.x – CamBox.x)/4,0,PlateThick – TextDepth/2] + PiPlateOffset)
	cube([15.0,30.0,TextDepth + Protrusion],center=true);
	}

	translate([-PiPlate.x/2 + (PiPlate.x – CamBox.x)/4 + 3,0,PlateThick – TextDepth – Protrusion] + PiPlateOffset)
	linear_extrude(height=TextDepth + Protrusion,convexity=2)
	rotate(-90)
	text("Ed Nisley",font="Arial:style=Bold",halign="center",valign="center",size=4,spacing=1.05);

	translate([-PiPlate.x/2 + (PiPlate.x – CamBox.x)/4 – 3,0,PlateThick – TextDepth – Protrusion] + PiPlateOffset)
	linear_extrude(height=TextDepth + Protrusion,convexity=2)
	rotate(-90)
	text("KE4ZNU",font="Arial:style=Bold",halign="center",valign="center",size=4,spacing=1.05);

view raw HQ Camera Backplate.scad hosted with ❤ by GitHub

2020-09-29

Bike Helmet Mirror: Brasswork Clamp

A bit of Quality Shop Time produced a slight improvement to the clamp holding the mirror to the stalk:

Helmet Mirror Ball Mount – mirror joint brasswork

The general idea is to hold the wave washer (it’s mashed under the flat washer, honest) above those bumps on the plate holding the mirror and stalk balls. It’s a few millimeters from the end of a ¼ inch brass rod, drilled for the M3 screw, and reduced to 4.5 mm with a parting tool to clear the bumps.

While I was at it, I made two spare mirrors, just to have ’em around:

Helmet Mirror Ball Mount – new vs old

The new ball mount looks downright svelte compared to the old Az-El mount, doesn’t it?

I should replace the steel clamp plates with a stainless-steel doodad of some sort to eliminate the unsightly rust, but that’s definitely in the nature of fine tuning.

2020-09-24
More AAA-to-AA Alkaline Adapters

Having a handful of not-dead-yet AAA alkalines and a bunch of LED blinkies built for AA alkalines, a pair of adapters seemed in order:

AAA-to-AA Alkaline Adapters – installed

The blinkies need a somewhat wider base than they’d get from a pair of AAA alkalines, so it’s not quite as dumb as it may seem.

In any event, the positive terminal comes from a brass rod:

AAA-to-AA Alkaline Adapters – brass terminal

Nobody will ever see the fancy Hilbert Curve infill around the brass:

AAA-to-AA Alkaline Adapters – end view

In this application, they’ll go from not-dead-yet to oh-it’s-dead faster than AA cells, so I can watch how the blinkies work with lower voltages.

2020-09-23