MK4 – Page 4 – The Smell of Molten Projects in the Morning

Prusa MK4 Camera Mount

Combining the Articulating Raspberry Pi Camera Mount with the Standardized Links and a few more bits & pieces from Printables made this happen:

Prusa MK4 - RPi camera installed — Prusa MK4 – RPi camera installed

The camera will benefit from better lighting, but it has a great view of the proceedings and gets the job done:

RPi Camera Mount - image — RPi Camera Mount – image

The Standardized Link holes clear an M6 bolt, but the Thumb Remix models use M5×25 hex-head screws (the doc says M4) and they work fine. I printed the (turn-able) bolt knobs in blue PETG-CF to distinguish them from the (fixed) nut knobs, which really don’t need knurling.

The camera ball mount has a threaded socket for the original plastic screws, but the stem isn’t quite thick enough for an M5 insert. Heat-setting an M4 brass insert into the hole and epoxying an M4×25 hex-head screw into one of the Remix knobs worked fine.

One Snap Fit Cable Management Clip holds the ribbon cable to a link. I think the RPi can fit under the platform inside the MK4 frame, with another clip or two routing the cable below the mount and frame. Adding another layer to the foam foot pads may improve the clearance.

The mount attaches to the MK4 frame with a 3030 adapter and a 45° link on the top. If I were in the mood, I’d make the 3030 adapter link longer for enough clearance beyond the M4 socket-head cap screws to get a ball-end hex wrench in there.

The small figure on the platform is a Articulated Grim Reaper done in black and white as an MMU3 test.

Now I can keep an eye on the proceedings from the Comfy Chair …

2026-05-15

Prusa MK4 Headbed Insulation

Over the winter, my Prusa MK4 printer occasionally coughed up a MINTEMP error when its platform heater cannot maintain the 90 °C called for by PETG. I finally added a cardboard insulating layer under the PCB heater:

Prusa MK4 Headbed - cardboard insulation — Prusa MK4 Headbed – cardboard insulation

Yes, the blue tool layer rectangle marking the centers of the corner cutouts is offset 2.5 mm to the left:

Heatbed Insulation - LightBurn layout — Heatbed Insulation – LightBurn layout

The layout is not symmetric, because Prusa wanted to prevent you from installing the PCB incorrectly, so I needed three tries to get it right.

The alert reader will note the lack of the front-corner chamfers in the picture letting your fingers get under the corners to remove the steel sheet. I cut ’em off with a utility knife and you get the benefit of hindsight.

Whether this minimal insulation will solve the problem shall remain unknown until the coldest days of next winter, but eliminating drafts around the thermistor taped to the bottom of the PCB can’t possibly be a Bad Thing™.

The LightBurn layout exported to an SVG image as a GitHub Gist:

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view raw Heatbed Insulation – LightBurn layout.svg hosted with ❤ by GitHub

2026-05-14

Work Sharp Precision Sharpener: Clamp Support

Another Work Sharp Precision Adjust sharpener improvement from Printables:

WorkSharp - clamp support — WorkSharp – clamp support

Although the blade clamp is a snug fit in its socket, it has enough ~~stick-out~~ cantilever to move slightly even under minimal force from the diamond tools.

I added a thin cardboard shim, cut with a utility knife (!) and stuck on with a craft adhesive sheet, as the block was about half a millimeter upward with the clamp turned this-a-way and half a millimeter downward the other way. Your mileage / setup will certainly differ.

I like the sharpener, but it’s much fiddlier than I expected.

2026-05-05

Window Mount for Bamboo Bee Tunnel Nests

Mary suggested converting wild bamboo up the hill into tunnel nests (per a xerces.org paper) for native bees buzzing around flowers in the yard, so:

Bee Tunnel Nest - downspout installation — Bee Tunnel Nest – downspout installation

I hung bundles of larger tubes in trees out back, in hopes of attracting huge carpenter bees.

3D printed mounts hold smaller bundles on the windows to let us keep an eye on the proceedings:

Bee Tunnel Nest Mount - installed-] — Bee Tunnel Nest Mount – installed

Which look better when not seen though two layers of glass in desperate need of Spring Cleaning:

The tabs provide a bit of pressure to hold the mounts in place, although I don’t know if they have enough springiness or will survive contact with the elements:

Bee Tunnel Nest Mount - tab section - solid model — Bee Tunnel Nest Mount – tab section – solid model

The key advantage of not building bigger bee motels: these little bundles don’t need annual cleaning / maintenance and will eventually fall apart.

If the bees find them suitable, more power to ’em!

And I realized the cut-off ends fit in the rotary. Witticisms engraved on bamboo could become the New Hotness:

Stipulated: I’m barely half-right about being a wit …

The OpenSCAD source code as a GitHub Gist:

	// Bee Tunnel Nest Mount
	// Ed Nisley – KE4ZNU
	// 2026-04-26

	include <BOSL2/std.scad>

	Layout = "Show"; // [Build,Show,Window,Bundle,Tabs]

	BundleOD = 35.0;
	BundleOffset = 0.0;

	SlotDepth = 18.0;
	SlotGap = 1.2;


	/* [Hidden] */

	HoleWindage = 0.2;
	Protrusion = 0.01;
	NumSides = 324;

	Clearance = 0.3;

	//$fn=NumSides;

	WallThick = 2.0;

	MountHeight = 1.5*BundleOD;
	MountWidth = 1.5*BundleOD + BundleOffset;

	ClipOA = [SlotDepth + WallThick,SlotGap + 2*WallThick,MountHeight];

	BundleCtr = [-WallThick/2,ClipOA.y + MountWidth/2 + BundleOffset/2,MountHeight/2];

	TabOA = [0.7SlotDepth,5.0,0.7WallThick];
	TabOffset = 0.2*SlotDepth;
	TabOC = MountHeight/2;

	TabClearance = [4*Clearance,0,Clearance];

	//—–
	// Define things

	module BundleMount() {

	difference() {
	cuboid([WallThick,MountWidth + ClipOA.y,MountHeight],
	rounding=3.0,edges=[TOP+BACK,BOTTOM+BACK],anchor=FRONT+RIGHT);
	back(BundleCtr.y)
	xcyl(3*WallThick,d=BundleOD);
	for (j=[-1,1],k=[-1,1])
	translate([BundleCtr.x,jBundleOD/2 + BundleCtr.y,kBundleOD/2])
	xcyl(3*WallThick,d=3.0,$fn=6);
	}

	}

	module WindowMount() {

	difference() {
	cuboid(ClipOA,rounding=3.0,edges=[TOP+LEFT,BOTTOM+LEFT],
	anchor=FRONT+RIGHT);
	left(WallThick) back(WallThick)
	cuboid([2SlotDepth,SlotGap,2MountHeight],anchor=FRONT+RIGHT);
	for (k=[-1,1])
	translate([-(ClipOA.x – TabOffset),-Protrusion,k*TabOC/2])
	cuboid([TabOA.x + TabClearance.x,WallThick + 2Protrusion,TabOA.y + 2TabClearance.z],anchor=FRONT+LEFT);
	}

	}

	module Tabs() {

	for (j=[-1,1])
	fwd(j*TabOC/2)
	cuboid(TabOA,anchor=BOTTOM+LEFT) position(LEFT+TOP)
	prismoid(size1=[3*SlotGap,TabOA.y],size2=[0,TabOA.y/2],
	h=(WallThick – TabOA.z) + SlotGap/3,anchor=BOTTOM+LEFT);

	}

	module Assembly() {

	union() {
	BundleMount();
	WindowMount();
	left(ClipOA.x – TabOffset – TabClearance.x)
	xrot(-90)
	Tabs();
	}
	}


	//—–
	// Build things

	if (Layout == "Bundle") {
	BundleMount();
	}

	if (Layout == "Window") {
	WindowMount();
	}

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


	if (Layout == "Show") {
	Assembly();
	}

	if (Layout == "Build") {
	yrot(90)
	Assembly();
	}

view raw Bee Tunnel Nest Mount.scad hosted with ❤ by GitHub

2026-04-30

PolyDryer Humidity: April-ish

After about five weeks:

	2026-04-16
Filament	%RH	Weight – g	Wt gain – g	Gain %
PETG White	14	–	–	–
PETG Black	14	–	–	–
PETG Orange	22	52.5	2.5	5.0%
PETG Natural	15	–	–	–
PETG-CF Blue	23	55.4	5.4	10.8%
PETG-CF Gray	18	–	–	–
PETG-CF Black	14	–	–	–
PETG Blue	10	–	–	–
TPU Clear	14	–	–	–
TPU Black	14	–	–	–

Most of the PolyDryer boxes had the same humidity as before, so I didn’t disturb them. When the humidity starts to rise, then we’ll see what’s going on in there.

The PETG Orange meter continues to misbehave and has been glitching from 22% to 30%. The indicator card shows the humidity is around 10% inside and the relatively low weight gain suggests there’s not much water to be adsorbed.

The PETG-CF Blue spool is new and, once again, shows filament does not arrive bone-dry in the factory wrapper.

Those two boxes now have alumina beads.

Dehydrating the jar of wet silica gel on the induction cooktop (set for 405 °F) sweated it down from 532 g to 503 g over the course of four hours, with nearly all of that change in the first two hours.

Obligatory photo from a while ago, because it looks pretty much the same now:

Silica gel beads - drying — Silica gel beads – drying

2026-04-20

Gridfininty Tape Dispenser

A Gridfinity Tape Dispenser holds a roll of book repair tape:

Gridfinity Tape Dispenser - overview — Gridfinity Tape Dispenser – overview

The perspective makes the dispenser look chonkier than it really is.

A wrap of black silicone tape around the spool embiggens it for a snug fit inside the tape core. A casual inspection of other tapes suggest enlarging the spool by a few percent would help, but it’s Good Enough™ as-is.

The two end thumbscrews fasten the 4×1 Gridfinity baseplate to the dispenser; both from Gridfinity Refined:

Gridfinity Tape Dispenser - baseplate — Gridfinity Tape Dispenser – baseplate

If I had my wits about me, I’d have used a nicely contrasting color for the baseplate, but it is what it is.

Although they’re called “thumbscrews”, the slot is sized for a US quarter (or cart coin).

An OpenSCAD one-liner produces an SVG model of the baseplate:

projection(cut=true) import("Grid 4x1.stl");

Import SVG into LightBurn, delete the magnet pockets, and Fire The Laser on some EVA foam:

Gridfinity Tape Dispenser - foam base — Gridfinity Tape Dispenser – foam base

A layer of 3M 300LSE tape holds the foam in place, because neither side sticks well to the goo on a craft adhesive sheet due to their low surface energy. I stuck an oversize rectangle to the foam with the thin adhesive side before cutting, which required a second pass at higher speed.

The thumbscrews also close off the holes in the dispenser bottom through which I poured 275 g = 10 oz of sand for better traction. Steel shot is reputed to be Even Better, although most of the BBs are in the long-arm weight.

The dispenser model includes a printed serrated blade which works as poorly as the author suggested. A length snapped from an ancient Strombecker 4-I (“four eye”) blade in the Box o’ Big X-Acto Blades fits perfectly, works wonderfully well, and is sufficiently inconspicuous to warrant the warning label. An X-Acto #26 Whittling Blade would probably snap down equally well.

2026-04-13

LED Garage Light: Desk Lamp Upcycling

One of the heatsink panels from the defunct LED garage light now casts a uniform warm-white glow on my desk:

LED Garage Light - desk light — LED Garage Light – desk light

A PCB intended as a lithium battery charger serves as a constant-current supply:

LED Garage Light - constant current driver — LED Garage Light – constant current driver

The three trimpots, from left to right:

Constant-voltage limit adjustment
Full-charge current setpoint (irrelevant here)
Constant-current limit adjustment

The as-received trimpot settings will be wildly inappropriate for a nominal 10 W COB LED array, so:

Connect the output to about 10 Ω of power resistors
… with an ammeter in series
Connect the input to a 12 VDC / 1-ish A wall wart
Adjust the output voltage to 10 V
Adjust the output current to 900 mA

As long as the voltage limit is over about 10 V, it will (likely) never matter, as the LED forward drop doesn’t vary much with temperature. Setting it to something sensible keeps it out of the way.

The middle trimpot apparently sets a voltage for a comparator to light an LED when the battery current drops below that level as it reaches full charge.

Although the regulator touts its high efficiency, it does run hot and a heatsink seemed in order:

LED Garage Light - heatsink — LED Garage Light – heatsink

Stipulated: the fins run the wrong way and it’s sitting in the updraft from the main heatsink. It’s Good Enough™.

The switch on the top comes from the collection of flashlight tailcap switches and controls the 12 V input power. It’s buried up to its button in a generous dollop of JB Kwik epoxy, which seemed the least awful way to get that done.

The solid model looks about like you’d expect:

LED Lamp Driver case - switch housing - show solid model — LED Lamp Driver case – switch housing – show solid model

The OpenSCAD code exports the (transparent) lid as an SVG so I can import it into LightBurn and laser-cut some thin acrylic. Two tape snippets hold the lid in place pending more power-on hours, after which I’ll apply a few dots of cyanoacrylate adhesive and call it done.

The case builds in two pieces that glue together to avoid absurd support structures:

LED Lamp Driver case - switch housing - build solid model — LED Lamp Driver case – switch housing – build solid model

A 3D printed adapter goes between the desk lamp arm and the lamp heatsink bolt:

LED Lamp Driver case - arm adapter - solid model — LED Lamp Driver case – arm adapter – solid model

The OpenSCAD source code files for the case and adapter arm as a GitHub Gist:

	// LED Lamp arm adapter
	// Ed Nisley – KE4ZNU
	// 2026-03-18

	include <BOSL2/std.scad>

	Layout = "Adapter"; // [Show,Build,ArmClamp,SinkClamp,Adapter]

	/* [Hidden] */


	HoleWindage = 0.2;
	Protrusion = 0.01;
	Gap = 5.0;

	$fn=534;

	HoleOC = 45.0;

	ArmRad = 7.5;
	ArmWidth = 11.3;

	SinkOD = 11.5;
	SinkThick = 3.2;
	SinkOC = 20.0;

	ClampThick = 5.0; // outside sink, watch thinning due to hull()


	// Define things

	// Screw & bushings in lamp arm bracket
	// … over-long bushings to prevent coincident surfaces

	module ArmClamp() {

	BushingThick = 1.5;
	BushingOD = 9.0;

	union() {
	ycyl(ArmWidth,d=4.0 + HoleWindage); // central M4 screw
	for (j=[-1,1]) {
	back(j*(ArmWidth – BushingThick + Protrusion)/2)
	ycyl(BushingThick + Protrusion,d=BushingOD);
	back(j*(ArmWidth + 10)/2)
	cuboid([2ArmRad,10,2ArmRad]);
	}
	}
	}

	module SinkClamp() {

	union() {
	ycyl(2*SinkOC,d=6.0 + HoleWindage); // central M6 screw
	for (j=[-1,1])
	back(j*SinkOC/2) {
	ycyl(SinkThick + Protrusion,d=SinkOD);
	cuboid([SinkOD,SinkThick + Protrusion,2*SinkOD]);
	}
	}
	}

	module Adapter() {

	difference() {
	hull() {
	right(HoleOC)
	ycyl(ArmWidth,r=ArmRad);
	ycyl(SinkOC + SinkThick + 2*ClampThick,d=SinkOD);
	}
	right(HoleOC)
	ArmClamp();
	SinkClamp();
	}

	}

	// Build it

	if (Layout == "ArmClamp")
	ArmClamp();

	if (Layout == "SinkClamp")
	SinkClamp();

	if (Layout == "Adapter")
	Adapter();

	if (Layout == "Build")
	up(SinkOD/2)
	yrot(-atan((ArmRad – SinkOD/2)/HoleOC))
	Adapter();

view raw LED Lamp arm adapter.scad hosted with ❤ by GitHub

	// LED Constant-current driver case
	// Ed Nisley – KE4ZNU
	// 2026-03-15

	include <BOSL2/std.scad>

	Layout = "Show"; // [Show,Build,Case,Lid,LidSVG,Switch]

	/* [Hidden] */

	ThreadThick = 0.2;
	HoleWindage = 0.2;
	Protrusion = 0.01;
	Gap = 5.0;

	WallThick = 1.8;

	TapeThick = 1.5;

	DriverOA = [48.5,13.5 + TapeThick,23.5]; // PCB forward Y, pots along top to rear

	SinkOA = [31.5,12.0,15.5]; // fins forward
	SinkOffset = [(DriverOA.x – SinkOA.x)/2,0,2.0]; // from lower left front corner of PCB

	AdjPots = [14,24,34]; // screwdriver adjust offsets
	AdjOD = 3.0; // … access hole dia

	CaseOA = DriverOA + [2WallThick,2WallThick,2*WallThick];
	echo(CaseOA=CaseOA);

	LidOA = [CaseOA.x – WallThick,CaseOA.z – WallThick,1.0];
	Cables = [8.0,3.0 + WallThick/2,LidOA.z];

	SwitchWireOC = DriverOA.x – 6.0;
	SwitchCapBase = [DriverOA.x + WallThick,DriverOA.y + WallThick];
	SwitchCapTop = [DriverOA.x,12.0];
	SwitchCavity = [25.0,10.5,5.5];

	// Define things

	module Lid() {

	difference() {
	cuboid(LidOA,anchor=BOTTOM+FWD+LEFT);
	for (i = AdjPots)
	translate([i,LidOA.y – AdjOD/2 – WallThick/2,-Protrusion])
	cyl(LidOA.z + 2*Protrusion,d=AdjOD,anchor=BOTTOM,$fn=8,spin=180/8);
	translate([LidOA.x/2,-Protrusion,-Protrusion])
	cuboid(Cables + [0,Protrusion,2*Protrusion],rounding=1.0,edges=[BACK+LEFT,BACK+RIGHT],anchor=BOTTOM+FWD);
	}

	}

	module SwitchBox() {

	difference() {
	prismoid(SwitchCapBase,SwitchCapTop,SwitchCavity.z,anchor=BOTTOM);
	down(Protrusion)
	cuboid(SwitchCavity + [0,0,2*Protrusion],anchor=BOTTOM);
	hull()
	for (i=[-1,1])
	right(i*SwitchWireOC/2)
	zcyl(CaseOA.z,d=3.0,$fn=8,spin=180/8);


	}

	}

	module Case() {

	difference() {
	cuboid(CaseOA,chamfer=WallThick/2,anchor=BOTTOM+FWD+LEFT);

	translate([WallThick,WallThick + Protrusion,WallThick])
	cuboid(DriverOA + [0,WallThick + Protrusion,0],anchor=BOTTOM+FWD+LEFT);
	translate(SinkOffset + [WallThick,WallThick + 2*Protrusion,WallThick])
	cuboid(SinkOA,anchor=BOTTOM+BACK+LEFT);

	for (i=[-1,1])
	translate([i*SwitchWireOC/2 + CaseOA.x/2,CaseOA.y/2,CaseOA.z/2])
	zcyl(CaseOA.z,d=2.0,anchor=BOTTOM,$fn=8,spin=180/8);

	translate([WallThick/2,(CaseOA.y + LidOA.z),WallThick/2])
	xrot(90)
	scale([1,1,2])
	Lid();
	}

	}

	// Build it

	if (Layout == "Switch")
	SwitchBox();

	if (Layout == "Case")
	Case();

	if (Layout == "Lid")
	Lid();

	if (Layout == "LidSVG")
	projection(cut=true)
	Lid();


	if (Layout == "Show") {
	Case();
	translate(SinkOffset + [WallThick,WallThick + 2*Protrusion,WallThick])
	color("Gray",0.7)
	cuboid(SinkOA,anchor=BOTTOM+BACK+LEFT);

	translate([CaseOA.x/2,CaseOA.y/2,CaseOA.z])
	SwitchBox();

	translate([WallThick/2,CaseOA.y,WallThick/2])
	xrot(90)
	color("Gray",0.7)
	Lid();
	}

	if (Layout == "Build") {
	fwd(Gap)
	xrot(90)
	Case();

	translate([CaseOA.x/2,(Gap + CaseOA.y/2),0])
	SwitchBox();
	}

view raw LED Lamp Driver case.scad hosted with ❤ by GitHub

2026-04-03