MK4 – Page 11 – The Smell of Molten Projects in the Morning

3D Printed Smashed Glass Coasters: Optimization

A pair of 3D printed smashed glass coasters for a friend:

Printed Coasters - in use — Printed Coasters – in use

The black PETG coaster under the French Press:

Printed Coasters - black PETG finished — Printed Coasters – black PETG finished

The white PETG coaster under the mug:

Printed Coasters - white PETG finished — Printed Coasters – white PETG finished

They’re considerably improved from the first attempt:

Smashed glass printed coaster - front view — Smashed glass printed coaster – front view

More details to follow …

2025-10-14

Baseboard Radiator Sleds

Cleaning the baseboard radiator fins before moving the houseplants back to their winter abode by the living room window made sense, so I took the trim covers off and vacuumed a remarkable accumulation of fuzz off the top and out from between the fins. The covers had an equally remarkable accumulation of sawdust along their bottom edge, apparently deposited when the previous owners had the floor sanded before they moved in a decade ago.

If you happen to live in a house with baseboard radiators, I’m guessing you never looked inside, because nobody (else) does.

Anyhow, the radiator fins should rest on plastic carriers atop the bent-metal struts also supporting the trim covers, so that they slide noiselessly when the copper pipe expands & contracts during the heating cycle. Over the last six decades, however, the plastic deteriorated and most of the carriers were either missing or broken to the point of uselessness:

Baseboard Radiator Sled - old vs new — Baseboard Radiator Sled – old vs new

The shapes on the bottom are replacements made with a 3D printed base (“sled”) and a chipboard wrap around the radiator preventing the fins from contacting the strut:

Baseboard Radiator Sled - OpenSCAD show — Baseboard Radiator Sled – OpenSCAD show

Although it was tempting to 3D print the whole thing, because plastic, I figured there was little point in finesse: chipboard would work just as well, was much faster to produce, and I need not orient the shapes to keep the printed threads in the right direction.

The Prusa MK4 platform was just big enough for the number of sleds I needed:

Baseboard Radiator Sled - printed — Baseboard Radiator Sled – printed

The sleds along the left and right edges lost traction as the printing progressed, but everything came out all right.

The OpenSCAD program also produces 2D SVG shapes for the chipboard wraps and adhesive rectangles sticking them to the sleds:

Baseboard Radiator Sled - OpenSCAD SVGs — Baseboard Radiator Sled – OpenSCAD SVGs

Import those into LightBurn, duplicate using the Grid Array, Fire The Laser, then assemble:

Baseboard Radiator Sled - assembly — Baseboard Radiator Sled – assembly

The slits encourage the chipboard to bend in the right direction at the right place, so I didn’t need any fancy tooling to get a decent result.

A few rather unpleasant hours crawling around on the floor got the struts bent back into shape and the sleds installed under the fins:

Baseboard Radiator Sled - installed — Baseboard Radiator Sled – installed

Protip: Gloves aren’t just a good idea, they’re essential.

The trim cover presses the angled chipboard where it should go against the fins. The covers carry shadows of the plastic carriers, suggesting the clearance was tighter than it should have been and thermal cycling put more stress on the plastic than expected. We’ll never know.

Although I’ll make more for the other baseboards as the occasion arises, I hope to never see these again …

The OpenSCAD source code as a GitHub Gist:

	// Baseboard radiator sled
	// Ed Nisley – KE4ZNU
	// 2025-10-11

	include <BOSL2/std.scad>

	Layout = "Sled"; // [Show,Build3D,Build2D,Sled,Wrap,Glue]

	/* [Hidden] */

	HoleWindage = 0.2;
	Protrusion = 0.1;

	Gap = 5.0;

	Radiator = [25.0,62.0,50.0]; // X = support base, YZ = radiator element

	SledBase = [Radiator.x + 10.0,Radiator.y,1.0]; // support under wrap
	Runner = [SledBase.x – 2.0,3.0,1.6]; // bars contacting radiator support

	GlueOA = [SledBase.x,SledBase.y] – [2.0,2.0]; // glue sheet

	Wrap = [SledBase.x,Radiator.y + 1.0,Radiator.z + 1.0]; // chipboard wrap around radiator
	WrapFlat = [Wrap.x,Wrap.y + 2*Wrap.z];
	WrapThick = 1.2;
	WrapSlit = 0.4;

	//—–
	// Sled base

	module Sled() {

	cuboid(SledBase,rounding=2.0,edges="Z",anchor=BOTTOM)
	position(TOP)
	for (j=[-1,1])
	fwd(j*SledBase.y/3)
	cuboid(Runner,rounding=Runner.z/2,edges="Z",anchor=BOTTOM);

	}

	//—–
	// Glue sheet
	// Export as SVG for laser cutting

	module Glue() {

	rect(GlueOA,rounding=2.0);

	}

	//—–
	// Radiator wrap
	// Export as SVG for laser cutting

	module Wrap() {

	difference() {
	rect(WrapFlat,rounding=2.0);
	for (j=[-1,1])
	fwd(j*Wrap.y/2)
	rect([Wrap.x/2,WrapSlit]);
	}

	}

	//—–
	// Build things

	if (Layout == "Sled")
	Sled();

	if (Layout == "Glue")
	Glue();

	if (Layout == "Wrap")
	Wrap();


	if (Layout == "Show") {
	xrot(180)
	Sled();
	color("Yellow",0.6)
	Glue();
	up(1)
	color("Brown") {
	cuboid([Wrap.x,Wrap.y,WrapThick],anchor=BOTTOM);
	for (j=[-1,1])
	fwd(j*Wrap.y/2)
	cuboid([Wrap.x,WrapThick,Wrap.z],anchor=BOTTOM);
	}
	}

	if (Layout == "Build3D") {
	Sled();
	}

	if (Layout == "Build2D") {
	left(GlueOA.x/2 + Gap/2)
	Glue();
	right(Wrap.x/2 + Gap/2)
	Wrap();
	}

view raw Baseboard Radiator Sled.scad hosted with ❤ by GitHub

2025-10-13

Dryer Vent Filter Snout

The first step in adding a filter bag to the dryer vent requires a convenient way to attach it. Because we live in the future, a couple of hours of 3D printing produced something that might work:

It’s made of TPU, which is bendy enough to ease two tabs into the two outermost slots you can see and a corresponding pair of tabs into slots on the wall side.

The solid model shows the part snapped inside the vent:

Clothes Dryer Vent Filter Snout - OpenSCAD show — Clothes Dryer Vent Filter Snout – OpenSCAD show

The flared bottom takes something like three hours to print (TPU likes slooow extrusion), so I did the top ring first to verify the tab fit:

Clothes Dryer Vent Filter Snout - OpenSCAD build — Clothes Dryer Vent Filter Snout – OpenSCAD build

Both parts come from hull() surfaces wrapped around quartets of thin circles at the proper positions; the difference() of two slightly different hulls produces thin shells.

A thin layer of JB PlasticBonder urethane adhesive, which bonds TPU like glue, holds the two parts together. I used the tan variant and, while it’s not a perfect match, it definitely looks better than black. Not that it matters in this case.

Mary will sew up a bag with a drawstring holding it to the snout. If everything survives the performance tests, printing the whole snout in one four-hour job will both make sense and eliminate an uneven joint that’s sure to be a lint-catcher.

The OpenSCAD source code as a GitHub Gist:

	// Clothes dryer vent filter snout
	// Ed Nisley – KE4ZNU
	// 2025-10-07

	include <BOSL2/std.scad>

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

	/* [Hidden] */

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

	HoleWindage = 0.2;
	Protrusion = 0.1;

	NumSides = 432*4;
	$fn=NumSides;

	Gap = 5.0;

	// Centers of corner rounding circles

	InnerWidth = 3.0; // wall inside snout
	InnerRadius = 6.0; // inner corner rounding

	RR = [130.0/2 – InnerRadius,91.0/2 – InnerRadius]; // right rear corner
	RF = [112.0/2 – InnerRadius,-(91.0/2 – InnerRadius)]; // right front corner

	CornerCtrs = [[RR.x,RR.y],[RF.x,RF.y],[-RF.x,RF.y],[-RR.x,RR.y]]; // clockwise from RR

	InsertHeight = 7.0; // overall height inside the snout

	TabOC = [73.0,91.0]; // tabs locking into snout

	TabCtrs = [[TabOC.x/2,TabOC.y/2],[TabOC.x/2,-TabOC.y/2],[-TabOC.x/2,-TabOC.y/2],[-TabOC.x/2,TabOC.y/2]];
	TabRadius = 5.0;
	TabHeight = 3.0;

	TaperHeight = 20.0; // Taper holding filter bag
	TaperRadius = 10.0; // outward to capture bag string
	TaperWidth = 2.0; // wall width

	TaperCtrs = CornerCtrs + [[0,-(TaperRadius – InnerWidth)],[0,0],[0,0],[0,-(TaperRadius – InnerWidth)]];

	//—–
	// Clear inside vent opening as 2D shape

	module Opening() {
	hull()
	for (p = CornerCtrs)
	translate(p)
	circle(r=InnerRadius);

	}


	//—–
	// Insert ring locking into vent snout

	module Ring() {

	difference() {
	union() {
	linear_extrude(h=InsertHeight)
	offset(delta=InnerWidth)
	hull()
	for (p = CornerCtrs)
	translate(p)
	circle(r=InnerRadius);
	up(InsertHeight – TabHeight)
	linear_extrude(h=TabHeight)
	for (p = TabCtrs)
	translate(p)
	circle(r=TabRadius);
	}
	down(Protrusion)
	linear_extrude(h=2*InsertHeight)
	Opening();
	}

	}

	//—–
	// Taper glued to ring

	module Taper() {

	difference() {
	hull() {
	up(TaperHeight)
	linear_extrude(h=Protrusion)
	offset(delta=InnerWidth)
	hull()
	for (p = CornerCtrs)
	translate(p)
	circle(r=InnerRadius);
	linear_extrude(h=Protrusion)
	offset(delta=TaperRadius)
	hull()
	for (p = TaperCtrs)
	translate(p)
	circle(r=TaperRadius);
	}
	hull() {
	up(TaperHeight)
	linear_extrude(h=2*Protrusion)
	offset(delta=InnerWidth)
	hull()
	for (p = CornerCtrs)
	translate(p)
	circle(r=InnerRadius – InnerWidth);
	down(Protrusion)
	linear_extrude(h=2*Protrusion)
	offset(delta=TaperRadius – TaperWidth)
	hull()
	for (p = TaperCtrs)
	translate(p)
	circle(r=TaperRadius);
	}
	}
	}

	//—–
	// Build things

	if (Layout == "Ring")
	Ring();

	if (Layout == "Taper")
	Taper();

	if (Layout == "Show") {
	up(TaperHeight)
	Ring();
	Taper();
	}

	if (Layout == "Build") {
	back(55)
	up(InsertHeight)
	yrot(180)
	Ring();
	fwd(55)
	up(TaperHeight)
	yrot(180)
	Taper();
	}

view raw Clothes Dryer Vent Filter Snout.scad hosted with ❤ by GitHub

2025-10-10

Polydryer Humidity: October

Another month of data from all those Polydryer boxes:

	7 Oct 2025			8 Oct
Filament	%RH	Weight – g	Wt gain – g	%RH
PETG White	28	26.6	1.6	19
PETG Black	25	26.6	1.6	20
PETG Orange	29	26.6	1.6	21
PETG Blue	23	26.7	1.7	15
PETG-CF Blue	26	26.6	1.6	23
PETG-CF Black	23	26.4	1.4	20
PETG-CF Gray	30	26.5	1.5	26
TPU	28	26.3	1.3	27
Empty 1 → White	35	26.7	1.7	37
Empty 2	36	27.1	2.1	24

The “PETG White” spool in the top line is nearly empty, so I loaded a new spool into the “Empty 1” box.

The “Empty 1” 35% value on 7 Oct matches the other empty box, the desiccant having pulled the humidity down from the 51% basement level. The weight of the water pulled out seems low compared to “Empty 2”, as they both started with a fresh batch of basement air while changing the desiccant in September.

They’re again filled with 25 g of alumina beads, although I’m beginning to think silica gel does a better job.

A picture of the boxes, thus avoiding WordPress reminding me pictures improve SEO:

PolyDryer PC4 Fitting - Prusa MMU3 setup — PolyDryer PC4 Fitting – Prusa MMU3 setup

2025-10-09

Polydryer Humidity: Another Month of Data

The 25 g of silica gel in each Polydryer box produced these results after a month:

	8 Sept 2025			11 Sept	23 Sept
Filament	%RH	Wt – g	Wt gain – g	%RH	%RH
PETG White	25	27.6	2.6	15	21
PETG Black	22	27.3	2.3	15	20
PETG Orange	21	27.2	2.2	21	23
PETG Blue	19	27.3	2.3	14	15
PETG-CF Blue	24	27.4	2.4	21	22
PETG-CF Black	21	27.3	2.3	15	19
PETG-CF Gray	27	27.1	2.1	24	26
TPU	25	27.4	2.4	22	24
Empty 1	51	no gel	n/a	27	30
Empty 2	35	27.9	2.9	19	28

The humidity levels seem higher than before, with a bit under 10% weight gain.

The two “Empty” boxes show the difference between ambient basement humidity and letting 25 g of silica gel work on the box for a month. Comparing the latter’s weight gain with the other boxes shows occupying (much of) the interior with (relatively) dry filament reduces the desiccant’s workload.

The beads in the “Empty 2” box were definitely darker after soaking up an entire box full of 50 %RH air:

Polydryer - 37%RH meter - empty — Polydryer – 37%RH meter – empty

The meter reads 37%, rather than 35%, due to being out of the box for a few minutes.

They’re the darker swirl in the pan of beads:

Silica Gel regeneration - starting bead colors — Silica Gel regeneration – starting bead colors

That’s an accumulation of beads from a few months, not just what you see in the table.

I used an induction cooktop to heat the cast-iron pan. Some fiddling with the cooktop’s constant-temperature mode got the beads to 200 °F with a 460 °F setting in about an hour. Setting the cooktop to 50% in constant-power mode worked better, as the beads reached 220 °F in an hour and 230 °F after another hour.

The bead weights at various stages:

Start = 531 g
+1 hr at constant temperature = 491 g
+ 1 hr at 50% constant power = 483 g
+ 1 hr ditto = 480 g

The 41 g weight loss is 8.5% of the dry weight, roughly what you’d expect from the humidity readings.

After reloading the meters with 25 g of alumina beads, the 11 Sept humidity readings are slightly lower and the 23 Sept readings are roughly comparable.

2025-09-26

Fitbit Charge 5 Charging Stand

My Fitbit Charge 5 has become fussy about its exact position while snapped to its magnetic charger, so I thought elevating it above the usual clutter might improve its disposition:

FitBit Charge 5 stand - installed — FitBit Charge 5 stand – installed

The Charge 5 now snaps firmly onto its charger, the two power pins make solid contact, and it charges just like it used to.

The solid model comes from Printables, modified to have a neodymium ring magnet screwed into its base:

Fitbit Charge 5 stand - solid model section — Fitbit Charge 5 stand – solid model section

Which looks about like you’d expect;

FitBit Charge 5 stand - added magnet — FitBit Charge 5 stand – added magnet

A layer of cork covers the bottom and it sits neatly atop the USB charger.

The OpenSCAD source code punches the recesses and produces the bottom outline so LightBurn can cut the cork:

// FitBit Charge 5 Stand - base magnet
// Ed Nisley - KE4ZNU
// 2025-09-05

include <BOSL2/std.scad>

Layout = "Build";       // [Build, Base, Section]

module Stand() {
  difference() {
    left(38/2) back(65/2)
      import("Fitbit Charge 5 Stand.stl",convexity=10);

      down(0.05)
        cylinder(d=12.5,h=5.05,$fn=12);
      up(5.2)
        cylinder(d=3.0,h=10.0,$fn=6);
  }
}

//-----
// Build things

if (Layout == "Build")
  Stand();

if (Layout == "Base")
  projection(cut = false)
    Stand();

if (Layout == "Section")
  difference() {
    Stand();
    down(0.05) fwd(50)
      cube(100,center=false);
}

2025-09-24

Smashed Glass: 3D Printed Coaster Epoxy Fill

After positioning the smashed glass fragments atop reflective metalized paper in the 3D printed coaster base, I poured epoxy over everything and, after popping some bubbles, left it to cure:

Smashed glass printed coaster - detail — Smashed glass printed coaster – detail

I sprayed the white-ish fragments (on the left) with satin-finish clear rattlecan “paint” in the hopes it would keep epoxy out of the cracks between the glass cuboids and leave the highly reflective air gaps. While it did a reasonable job of sealing, it bonded poorly with the epoxy and produced a dull surface finish.

The unsprayed fragments (on the right) turned out better, although the one in the upper right has a thin air bubble / layer on top. The unsealed cracks between the cuboids show well against the reflective layers, so I think spraying the fragments isn’t worth the effort.

The printed base has a 1 mm tall rim to retain the epoxy:

Printed Coaster Layout - solid model — Printed Coaster Layout – solid model

I mixed enough epoxy to fill half the volume of a disk with the same overall OD and depth (V = h × π × d²/4), which turned out to be barely enough produce a level surface at the rim. There didn’t seem that much epoxy left on the various measuring / mixing cups, but next time I’ll round upward.

Many of the bubbles emerged from below the metalized paper, as well as between the glass and paper, so next time:

Set up a level platform with a sacrificial cover
Omit the adhesive sheet under the metallized paper
Pour a little epoxy into the recesses
Squish the metallized paper into place
Pour more epoxy to cover the paper
Gently squish the glass fragments into place
Ease more epoxy around the fragments
Chivvy the bubbles away
Fill to the rim

The top isn’t exactly flat and has some dull areas, so at some point I want to make it flat with 220 grit sandpaper, work up to some 3000 grit paper I’ve been saving for a special occasion, then finish it off with Novus polish. Which seems like enough hassle to keep the coaster under my sippy cup for a while.

2025-08-27