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: MK4

Prusa Mk 4 3D printer with MMU3 feeder

Prusa MK4 Bling

While figuring out an X Axis homing problem (about which, more later), I printed a bunch of add-ons for the Prusa MK4, all from printables.com.

Stipulated: Using something other than black PETG and PETG-CF would make them more like bling.

The heatsink fan gets a scoop inlet to keep fingers and tools farther from the blades:

Prusa MK4 – fan cover – fan duct

The small upward duct on the right side directs the exhaust air away from the platform. This is apparently critical for very high-temperature plastics like ABS and PC, but I did have one print fail due to excessively cold breezes on the platform.

I made three different ducts in case I break one:

Prusa MK4 – fan ducts on platform

The aluminum extrusions now have dust covers:

Prusa MK4 – Extrusion cover – front

There’s also an angled heater cable connector cover, with a matching cover on the electronics box routing the cable rearward to dress it away from the hulking extruder cable:

Prusa MK4 – Extrusion cover – rear

And the Z axis stepper mounts have tidy dust covers:

Prusa MK4 – Z axis motor cover

None of which are necessary, but they’re all easy to print while thinking of other things.

2024-11-20

Wire Plant Stand Feet

A pair of plant stands from a friend’s collection ended up in Mary’s care and cried out for feet to keep their welded steel wire legs from scratching the floor:

Admittedly, it’s not the prettiest stand you can imagine, but the sentimental value outweighs all other considerations.

The feet are shrink-wrapped around the legs with enough curviness to look good:

Wire plant stand feet - show side view — Wire plant stand feet – show side view

With a drain hole in the bottom to prevent water from rusting the wires any more than they already are:

Wire plant stand feet - show bottom view — Wire plant stand feet – show bottom view

I briefly considered a flat bottom at the proper angle to sit on the floor, but came to my senses; it would never sit at the proper angle.

The end results snapped into place:

Wire plant stand feet - indoor detail — Wire plant stand feet – indoor detail

Of course the other stand, at first glance identical to the one above, has a different wire size and slightly different geometry, which I only discovered after printing another trio of feet. Changing the appropriate constants in the OpenSCAD program and waiting an hour produced a better outcome:

Wire plant stand feet - outdoor stand — Wire plant stand feet – outdoor stand

Living in the future is good, all things considered.

The OpenSCAD code as a GitHub Gist:

	// Wire plant stand feet
	// Ed Nisley KE4ZNU
	// 2024-11-06

	Layout = "Show"; // [Show,Build,Leg,LegPair,FootShell,Foot,Section]

	/* [Hidden] */

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

	TOP = 0;
	BOT = 1;

	FootLength = 30.0; // vertical foot length

	LegRings = // [255.0,350.0,300.0]; // top dia, bottom dia, vertical height
	[260.0,312.0,300.0];

	WireOD = //4.6 + 0.4; // oversize to handle bent legs
	5.7 + 1.0;

	DrainOD = 4.0; // drain hole in the bottom

	LegWidth = // [65.0,9.7]; // outer width at top & bottom
	[95.0, 12.0];

	LegAngle = atan((LegWidth[TOP] – LegWidth[BOT])/(2*LegRings[LENGTH]));

	StandAngle = atan((LegRings[TOP] – LegRings[BOT])/(2*LegRings[LENGTH]));

	WallThick = 3.0;

	FootWidth = 2*[WallThick,WallThick] +
	[LegWidth[BOT] + LegWidth[TOP]*FootLength/LegRings[LENGTH],LegWidth[BOT]];
	echo(FootWidth=FootWidth);

	NumSides = 234;

	Protrusion = 0.1;

	//—– Set up pieces

	module Leg() {

	hull()
	for (k = [0,1])
	translate([0,0,k*LegRings[LENGTH]])
	sphere(d=WireOD,$fn=NumSides);
	}

	module LegPair() {

	for (i = [-1,1])
	translate([i*(LegWidth[BOT] – WireOD)/2,0,0])
	rotate([0,i*LegAngle,0])
	rotate(180/NumSides)
	Leg();
	hull() // simulate weld for flat bottom
	for (i = [-1,1])
	translate([i*(LegWidth[BOT] – WireOD)/2,0,0])
	rotate([0,i*LegAngle,0])
	rotate(180/NumSides)
	sphere(d=WireOD,$fn=NumSides);
	}

	module FootShell() {

	difference() {
	hull() {
	for (i = [-1,1]) {
	translate([i*((FootWidth[BOT] – WireOD)/2 – WallThick),0,0])
	rotate(180/NumSides)
	sphere(d=(WireOD + 2*WallThick),$fn=NumSides);

	translate([i*((FootWidth[TOP] – WireOD)/2 – WallThick),0,FootLength – WireOD/2])
	rotate(180/NumSides)
	sphere(d=(WireOD + 2*WallThick),$fn=NumSides);
	}
	}
	translate([0,0,FootLength + FootLength/2])
	cube([2FootWidth[TOP],10WallThick,FootLength],center=true);
	rotate(180/NumSides)
	cylinder(d=DrainOD,h=4*FootLength,center=true,$fn=NumSides);
	}
	}

	module Foot() {

	difference() {

	FootShell();
	hull()
	LegPair();

	}

	}

	//—– Build it

	if (Layout == "Leg")
	Leg();

	if (Layout == "LegPair")
	LegPair();

	if (Layout == "FootShell")
	FootShell();

	if (Layout == "Foot")
	Foot();

	if (Layout == "Section")
	difference() {
	Foot();
	cube([FootWidth[TOP],(WireOD + 2WallThick),2FootLength],center=false);
	}

	if (Layout == "Show") {
	rotate([StandAngle,0,0]) {
	Foot();
	color("Green",0.5)
	LegPair();
	}
	}

	if (Layout == "Build")
	translate([0,0,FootLength])
	rotate([0*(90-StandAngle),180,0])
	Foot();

view raw Wire plant stand feet.scad hosted with ❤ by GitHub

2024-11-08

Doorbell Button Skulls
With only days to spare, I decorated the doorbell button:

Doorbell button skulls – installed

Yeah, I jammed Sharpies in the eye sockets, but they look exactly the way they should. The middle skull is in the middle of the actuator in the hope that’s where it’ll get pushed.

The solid model comes directly from the seasonally appropriate teapot lid handle with a rectangle to suit the doorbell button actuator:

Doorbell Button Skulls – solid model

Perforce, the OpenSCAD code has eyeballometric magic numbers:
```
// Doorbell Button Enhancement
// Ed Nisley - KE4ZNU
// 2024-10-28

Button = [5.0,13.0,40.0];    // button width, boss depth, button height

union() {
    rotate([0,0,65])
    translate([-121,-105])      // totally eyeballometric
        import("stackofskulls - 50mm.obj",convexity=10);

        translate([0,Button.y/2,Button.z/2])
            cube(Button,center=true);
}
```
The rectangular slab goes all the way down to the platform because I couldn’t be bothered with support or a little wedge.

I’m sure it will survive exactly as long as it must.

Dunno how many little ones will venture up the driveway, though:

Halloween mailbox decorations
2024-10-31
Gizo Spider Footpads
Given a 3% failure rate for the tiny footprint of Gizo spider legs, I added 5 mm pads to each foot:

Gizo Spider – footpads

A few rounds of successive approximation and one copypasta hit the right spots:
```
// Gizo spider footpads
// Ed Nisley - KE4ZNU
// 2024-10-26

pts = [
[24,-23],[28.5,-7],[29.5,14.5],[20,28],
[-24,-23],[-28.5,-7],[-29.5,14.5],[-20,28]
];

translate([14,0,2.8])
  import("/mnt/bulkdata/Project Files/Prusa Mk4/Models/Gizo Spider/GizoSpider.stl");

linear_extrude(height=0.2)
  for (pt = pts)
    translate(pt)
      circle(d=5,$fn=2*3*4);
```
Which was enough to stick the legs firmly to the build platform:

Gizo spider – white leg towers

Talk about blank looks:

Gizo spider – black on platform

White filament is particularly susceptible to charred globbing:

Gizo spider – white char inclusion

Which was, fortunately, completely hidden inside the shell.

Extensive testing showed the pads pushed the error rate below 1.5%:

Gizo spider pile

As before, dots of hot melt glue hold the eyes in place.

All’s well that ends well: just in time, too.
2024-10-30
Cart Coin Handle vs. Reality

This failed pretty much the way I expected:

Cart Coin – broken handle

The “carbon fiber” part of PETG-CF consists of very very short fibers, unlike the longer fibers in real carbon fiber materials, so the strength is nowhere near what you might expect from the marketing. I knew this going in and the break wasn’t surprising.

Round cart coins continue to work exactly like US quarters.

2024-10-29
Humidifier Lid Hinges
The humidifier that Came With The House™ had a lid with two broken plastic hinges that I figured I could never replace, but while cleaning out the fuzz for the upcoming season I found one missing piece stuck inside the lid. Given a hint, I glued it back in place:

Humidifier Hinge – outlined

There’s a strip of duct tape around the outside holding the fragment in place while the adhesive cured.

A manual curve fit to the image in Inkscape produced the red outline, which gets saved as a plain SVG and fed into OpenSCAD to create a solid model:

Humidifier Hinge – solid model

The cylinder doesn’t exactly fit the end of the hinge, but it’s close enough. The straightforward OpenSCAD code making that happen:
```
// Humidfier Hinge Replacement
// Ed Nisley KE4ZNU
// 2024-10-20

HingeThick = 10.0;
PinLength = 10.0;

ScrewOD = 2.0;

NumSides = 2*3*4;
Protrusion = 0.1;

difference() {
    union() {
        translate([0,0,HingeThick])
            cylinder(d=6.0,h=PinLength,$fn=NumSides);

        linear_extrude(height=10.0,convexity=5)
            translate([-3.1,-8.0])
                import("Humidifier Hinge - ouline.svg");
    }

    cylinder(d=ScrewOD,h=4*(HingeThick + PinLength),center=true,$fn=8);
}
```
The pin has a hole for a M2 screw, but contemplation of the broken pieces suggested the pin wasn’t the weakest link, which later experience confirmed.

Figuring I’d need only one hinge, I made a spare for fitting:

Humidifier hinge – on platform

The unmodified part fit just about perfectly, whereupon a completely ad-hoc fixture involving a pair of laser-cut MDF slabs, a craft stick epoxy mixer, and more duct tape held it in place while the adhesive cured:

Humidifier hinge – fixturing

The hinge pin turned out to be half a millimeter too long, which is easily fixed, and it worked fine:

Humidifier hinge – installed

That’s more duct tape wrapped around the perimeter to hold the pieces in place, should it break again.

Which, I regret to report, occurred on the way up the stairs from the Basement Shop™ when the lid slipped from my grasp, fell away from the rest of the humidifer’s top panel, and jammed open:

Humidifier hinge – break

The PETG-CF part held together, the adhesive remained bonded to both pieces, but the original plastic fractured just below the joint. A closer look from the other side shows the break:

Humidifier hinge – break detail

The other hinge broke about where it did before.

So the humidifier remains in service with the lid in status quo ante and a small bag inside holding the fragments for the next return to the shop.

Drat!
2024-10-28
Gizo Spiders: Leg Splice

This being the season for decorative spiders, two more appeared:

Gizo spider assortment

Wedding photographers have trouble getting the proper exposure for both the bride and the groom, too.

Only one of the 32 legs came loose from the platform:

Gizo spider – failed leg

The upper part of the leg captured the loose segment and glommed it into a blob:

Gizo spider – failed leg – detail

Fortunately, one of the clearance test pieces was an isolated leg and joint, so I amputated the grisly mess, matched the cut in the test piece, and hot-melt-glued the pieces together:

Gizo spider – spliced leg

Not quite perfect, but good enough for the purpose.

Given the 3% failure rate, I think the legs show such small contact areas really do justify a brim. Adding a brim to the main body would mess up the joints, but I think PrusaSlicer can add brims to specific parts. More study is needed.

Orange eyes for the win!

2024-10-21