Software – The Smell of Molten Projects in the Morning

OMTech 60 W Laser: Plant Markers

While calibrating the laser’s scan offset, I also tried various fonts:

Offset cal - text - overview — Offset cal – text – overview

Putting two lines of the most-readable font inside an outline reverse-engineered from a few handwritten samples let me cut out a bunch of plant markers from white-on-black Trolase acrylic:

Plant Markers - cutting — Plant Markers – cutting

Which look downright dignified in real life:

Plant markers - African Violet — Plant markers – African Violet

Admittedly, sweet potato slips don’t require such extensive documentation:

Plant Markers - sweet potatoes — Plant Markers – sweet potatoes

Cutting the sheet flat on the honeycomb platform worked well, modulo Sadler’s warning about cutting acrylic, and a few smudges on the back of the markers will go unnoticed.

This was actually an excuse to use LightBurn’s Variable Text feature, so the tags contain formatting codes:

Plant Markers - Variable Text template — Plant Markers – Variable Text template

The codes give the position and format for text fields in a CSV file containing one line for each tag:

Austrocylindropuntia subulata,Eve’s Pin Cactus
Euphorbia,abyssiniaca
possibly G. Carinata,var. Verucosa
African Violet,Maui
Sansevieria trifasciata,Mother in law’s tongue
Plectranthus,'Mona Lavender'

The rules governing quoted strings and suchlike remain to be explored, but single quotes in the CSV file pass through unchanged.

Putting a tab at the point of the marker will prevent it from falling free when cut out, should you want to try raising the sheet above the platform to reduce the amount of crud accumulating on the back side.

Machine Shop, Home Ec, Software

Garden Cart Handle Pivot

For reasons not relevant here, I was tapped to replace the plastic parts attaching the handle to a garden cart:

Garden Cart - handle attachment — Garden Cart – handle attachment

The owner tried to contact the “manufacturer” to no avail; repair parts are simply not available, even if the name painted on the cart had a meaningful relationship to anything else.

Well, I can fix that:

Garden Cart - handle repair parts — Garden Cart – handle repair parts

Fortunately, another cart in the fleet provided the missing bits so I could reverse-engineer their measurements.

The solid model looks about like you’d expect:

Garden Cart Handle - show view — Garden Cart Handle – show view

Printing the two halves with those nice (yellow) bosses in place wasn’t feasible. They were exactly 1 inch in diameter, so I just parted two cookies from the end of a stout acetal rod after drilling a hole for the 2-¼ inch 5/16-18 bolt.

The two pieces took nigh onto three hours with five perimeters and 50% infill:

Garden Cart Handle - slicer preview — Garden Cart Handle – slicer preview

While delivering and installing the parts, I got volunteered to haul plants to cars with one of the carts during the upcoming Spring Plant Sale. That’ll teach me to stay in the Basement Shop …

The OpenSCAD source code as a GitHub Gist:

	// Garden Cart Handle Pivot
	// Ed Nisley KE4ZNU 2022-05

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

	/* [Hidden] */

	ThreadThick = 0.25;
	ThreadWidth = 0.40;

	HoleWindage = 0.2;

	Protrusion = 0.1; // make holes end cleanly

	inch = 25.4;

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

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


	//----------
	// Dimensions
	// Handle lies along X axis

	HandleOD = (7/8) * inch;

	BoltOD = (5/16) * inch;

	Washer = [BoltOD,1.0 * inch,2.0]; // just for Show

	Disk = [BoltOD,62.0,(3/16) * inch];

	ClampBase = [(1 + 7/8)inch,(1 + 1/8)inch,2.0];

	Kerf = 2.0;

	CornerRadius = 1.0;

	PivotOA = [Disk[OD],Disk[OD],HandleOD + 2ClampBase.z + 2Disk[LENGTH]];

	//----------------------
	// 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(d=(FixDia + HoleWindage),h=Height,$fn=Sides);
	}

	//----------------------
	// Set up parts

	module Handle() {
	translate([-2*PivotOA.x,0,0])
	rotate([0,90,0])
	PolyCyl(HandleOD,4*PivotOA.x,24);
	}

	module Bolt() {
	translate([0,0,-PivotOA.z])
	PolyCyl(BoltOD,2*PivotOA.z,12);
	}

	module Pivot() {
	difference() {
	union() {
	hull()
	for (i=[-1,1], j=[-1,1]) // rounded block
	translate([i(ClampBase.x/2 - CornerRadius),j(ClampBase.y/2 - CornerRadius),-PivotOA.z/2])
	cylinder(r=CornerRadius,h=PivotOA.z,$fn=4*8);
	for (k=[-1,1])
	translate([0,0,k*(PivotOA.z/2 - Disk[LENGTH]/2)])
	rotate(180/36)
	cylinder(d=Disk[OD],h=Disk[LENGTH],$fn=36,center=true);
	}

	Handle();
	Bolt();
	cube([2ClampBase.x,2ClampBase.y,Kerf],center=true); // slice through center
	}
	}





	//----------
	// Build them

	if (Layout == "Show") {
	rotate([90,-45,0]) {
	Pivot();
	color("Green")
	translate([2*PivotOA.x - PivotOA.x/2,0,0])
	Handle();
	color("Red")
	Bolt();
	color("Yellow")
	for (k=[-1,1])
	translate([0,0,k*(PivotOA.z/2 + Washer[LENGTH])])
	rotate(180/36)
	cylinder(d=Washer[OD],h=Washer[LENGTH],$fn=36,center=true);
	}
	}

	if (Layout == "Build") {
	Offset = 5.0;
	intersection() {
	translate([-(PivotOA.x/2 + Offset),0,PivotOA.z/2])
	Pivot();
	translate([-2PivotOA.x,-2PivotOA.y,0])
	cube([4PivotOA.x,4PivotOA.y,PivotOA.z/2],center=false);
	}
	intersection() {
	translate([(PivotOA.x/2 + Offset),0,PivotOA.z/2])
	rotate([180,0,0])
	Pivot();
	translate([-2PivotOA.x,-2PivotOA.y,0])
	cube([4PivotOA.x,4PivotOA.y,PivotOA.z/2],center=false);
	}
	}

view raw Garden Cart Handle.scad hosted with ❤ by GitHub

Home Ec, Machine Shop, Software

Laser-cut Cutworm Collars

Mary, having had considerable trouble with cutworms in her gardens, routinely deploys cardboard collars around new plants:

Cutworm Collars - assembled — Cutworm Collars – assembled

It seems cutworms trundle around until they find an edible plant, chew through the stem and topple the plant, then trundle off without taking another bite. A small cardboard barrier prevents them from sensing the plant: apparently, motivation to climb a short wall hasn’t yet evolved.

Up to this point, Mary applied scissors to tissue boxes, but I proposed an alternative with an adjustable fit to any plant:

A splayed cardboard box rarely lays flat, a condition enforced by a few MDF stops used as clamps.

Come to find out no two tissue boxes have identical dimensions, even boxes from the same brand / retailer, so lay out duplicates of the collar template to match your stockpile.

That was fun!

The SVG image as a GitHub Gist:

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view raw Cutworm Collar.svg hosted with ❤ by GitHub

Machine Shop, Software

OMTech 60 W Laser: Adjustable Honeycomb Stops

When you (well, I) get fussy about angular alignment on the laser cutter’s honeycomb platform, an adjustable stop or two may come in handy:

Laser Honeycomb - Adjustable Pins — Laser Honeycomb – Adjustable Pins

That’s a serving suggestion based on a true story, because I really wasn’t all that fussy about precise engraving alignment on those signs.

A more typical situation on a smaller scale:

Laser Honeycomb - Adjustable Pins - engraving — Laser Honeycomb – Adjustable Pins – engraving

The scrap of MDF with three holes provides angular alignment for the little two-color acrylic test coupon, so you can tuck successive squares into the corner, hammer them with slightly different patterns, then compare the results.

The stops are an off-center hole (the ±3 text gives the offset) in an MDF disk with an acetal post:

Laser Honeycomb - Adjustable Pins - detail — Laser Honeycomb – Adjustable Pins – detail

The 3 mm SHCS provides a convenient way to turn the post and disk, so the threading isn’t critical. Sufficiently snug threading will let you turn the screw counterclockwise without loosening it, but that surely depends on how tightly the 8 mm section fits into the honeycomb. The larger top section is 9mm, cleaned up from the rod’s nominal 3/8 inch OD, for a jam fit into the 8.8 mm + 0.1 mm kerf hole.

The SVG images as a GitHub Gist:

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view raw Eccentric honeycomb stops.svg hosted with ❤ by GitHub

The ±5 mm offset disk may be more useful with larger items and now you know where those three holes came from.

Machine Shop, Software

OMTech 60 W Laser: Laser Power Indicator

Although the OMTech laser controls the laser power supply with a key-lock switch, there’s little visible difference between the OFF and ON positions. Having occasionally mistaken it in both directions, this seemed like a useful addition:

Laser Power Lock Indicator - installed — Laser Power Lock Indicator – installed

The strip of black duct tape below the lock muffles the rattle of the triangle hatch key against the metal cabinet.

Two snippets of foam tape hold the knob to the lock cylinder, making an admittedly tenuous connection, but the knob fits around the outside of the switch housing with minimal clearance and ~~doesn’t~~ shouldn’t suffer any torque or pulling, so it might work.

The solid model looks about like you’d expect:

Laser Power Lock Indicator - solid model — Laser Power Lock Indicator – solid model

Unfortunately, it has no good orientation for printing, so I let PrusaSlicer generate support material inside the knob:

Laser Power Lock Indicator - Support structures — Laser Power Lock Indicator – Support structures

Suffice it to say: removing all that plastic did not go well.

I eventually grabbed the knob in the lathe and bored the interior out to its more-or-less proper dimensions, figuring nobody would ever notice the carnage, and it worked reasonably well. In the unlikely event I need another pointer, I’ll add a support spider to hold up the interior with minimal contact and less plastic.

Yeah, the laser really needs a stack light showing its condition and safety status …

The OpenSCAD source code as a GitHub Gist:

	// Indicator for OMTech laser power lock
	// Ed Nisley KE4ZNU 2022-04-09

	KnobOD = 35.0;
	KnobHeight = 22.0;
	KnobTaper = 4.0;

	PointerLength = 45.0;
	PointerThick = 3.0;

	TipOD = 2.0;

	/* [Hidden] */

	//------

	Protrusion = 0.1; // make holes end cleanly
	HoleWindage = 0.2;

	module PolyCyl(Dia,Height,ForceSides=0) { // based on nophead's polyholes
	Sides = (ForceSides != 0) ? ForceSides : (ceil(Dia) + 2);
	FixDia = Dia / cos(180/Sides);
	cylinder(d=(FixDia + HoleWindage),h=Height,$fn=Sides);
	}



	//----------
	// Create part
	// Plenty of magic numbers from actual measurements

	module Pointer() {

	difference() {
	union() {
	linear_extrude(height=PointerThick)
	hull() {
	circle(d=KnobOD,$fn=24);
	translate([PointerLength - TipOD/2,0])
	circle(d=TipOD,$fn=12);
	}

	cylinder(d=KnobOD,h=KnobHeight - KnobTaper,$fn=24);
	translate([0,0,KnobHeight - KnobTaper - Protrusion])
	cylinder(d1=KnobOD,d2=KnobOD - 3.0,h=KnobTaper + Protrusion,$fn=24);
	}

	translate([0,0,-Protrusion]) {
	PolyCyl(29.0,14.0 + Protrusion,24);
	PolyCyl(24.0,14.0 + 5.0 + Protrusion,24); // leaves clearance under pointer
	}

	translate([0,0,KnobHeight])
	cube([12.0,2.0,2*KnobHeight],center=true);

	}
	}

	//----------
	// Build it

	Pointer();

view raw Laser Power Lock Indicator.scad hosted with ❤ by GitHub

And doodles giving the dimensions of the key lock, not all of which can be true at the same time:

Laser Power Lock Indicator - Dimension Doodles — Laser Power Lock Indicator – Dimension Doodles

Machine Shop, Software

OMTech 60 W Laser: COB LED Shades

Adding LED strips around the interior of the laser platform definitely improved the visibility of things on the honeycomb platform:

OMTech 60W laser - COB LED strips — OMTech 60W laser – COB LED strips

However, all that upward-directed light goes directly into my glare-sensitive eyeballs, so I added shades above the strips:

COB LED Shade - installed — COB LED Shade – installed

They’re cut from corrugated cardboard because I have an essentially infinite supply and I’m still working out speeds and intensities. Eventually they’ll become something like black acrylic.

The brackets emerged from the vasty digital deep through the miracle of 3D printing:

COB LED Shade Brackets - slice preview — COB LED Shade Brackets – slice preview

They’re stuck to the laser cabinet and the cardboard with double-sided duct tape. If you’re careful, they will line up along one edge of the tape, roll over neatly to stick their other face, then a single razor knife cut can separate each pair of neighbors.

The underside sports an aluminized mylar strip to redirect the wasted light in a more useful direction:

COB LED Shade - aluminized Mylar reflector — COB LED Shade – aluminized Mylar reflector

The tapeless sticky shipped with the laser holds the reflector in place, while its 20 mm width sets the 21 mm shade dimension. Although you want a reasonably smooth layer, it need not be mirror-flat.

Now it’s really bright in there:

COB LED Shade - overview — COB LED Shade – overview

While I had my head under the hood, I stuck a fourth strip of COB LEDs on the lip along the rear edge of the opening; it’s bright enough to cast the shadow just forward of the laser head despite the OEM under-gantry LED strip. Because the rear strip is aimed downward, it didn’t need a shade.

The perforated cardboard sheet on the left is a spike plate: more about that later.

The SVG drawings as a GitHub Gist:

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view raw COB LED Shades.svg hosted with ❤ by GitHub

The OpenSCAD source code as a GitHub Gist:

	// Bracket for COB LED shade
	// Ed Nisley KE4ZNU 2022-03-24

	BaseLength = 20.0;

	/* [Hidden] */

	ThreadThick = 0.25;
	ThreadWidth = 0.40;

	HoleWindage = 0.2;

	Protrusion = 0.1; // make holes end cleanly

	WebThick = 4*ThreadWidth;
	BasePlate = [BaseLength,5*WebThick,WebThick];


	//----------
	// Create parts

	module Bracket() {

	R = BaseLength/3;
	N = 36;

	union() {
	rotate([90,0,0])
	translate([0,0,-WebThick/2])
	linear_extrude(height=WebThick,convexity=2)
	difference() {
	intersection() {
	union () {
	square(2*R,center=false);
	translate([0,2*R])
	rotate(180/N)
	circle(r=R,$fn=N);
	translate([2*R,0])
	rotate(180/N)
	circle(r=R,$fn=N);
	}
	square(3*R,center=false);
	}
	translate([2Rcos(180/N),2Rcos(180/N)])
	rotate(180/N)
	circle(r=R,$fn=N);
	}
	rotate([0,-90,0])
	translate([0,-BasePlate.y/2,-BasePlate.z])
	cube(BasePlate,center=false);
	translate([0,-BasePlate.y/2,0])
	cube(BasePlate,center=false);
	}
	}

	//----------
	// Build them

	Bracket();

view raw COB LED Shade brackets.scad hosted with ❤ by GitHub

Electronics Workbench, Machine Shop, Software

B4-size Light Pad: Stabilizing the USB Connector

What used to be a “light box” had become a “light pad” powered through a USB Micro-B connector on the side. Unfortunately, the pad’s 5 mm thickness allows for very little mechanical reinforcement around the USB jack, while providing infinite opportunity to apply bending force. Over the course of the last half-dozen years (during which the price has dropped dramatically, despite recent events), the slightest motion flickered the LEDs.

So I squished the jack’s metal shell back into shape, found a short right-angle USB cable, and conjured a reinforcing fixture from the vasty digital deep:

The plate fits under the light pad, where a strip of super-sticky duct tape holds it in place:

LitUp Light Pad USB jack reinforcement - bottom — LitUp Light Pad USB jack reinforcement – bottom

The USB plug fits between the two blocks with hot-melt glue holding it in place and filling the gap between the plug and the pad.

I’d like to say it’s more elegant than the cable redirection for my tablet, but anything involving black electrical tape and hot-melt glue just isn’t in the running for elegant:

LitUp Light Pad USB jack reinforcement - top — LitUp Light Pad USB jack reinforcement – top

On the other paw, that socket ought to last pretty nearly forever, which counts for a whole lot more around here.

The retina-burn orange tape patches on the connector eliminate all the fumbling inherent to an asymmetric connector with invisible surface features. The USB wall wart on the other end of the cable sports similar markings.

The OpenSCAD source code as a GitHub Gist:

	// Bracket to protect USB jack on LitUp LED Pad
	// Ed Nisley KE4ZNU 2022-03-28

	Protrusion = 0.1; // make holes end cleanly

	Pad = [10.0,30.0,1.2];
	Plug = [8.0,10.5 + 0.5,8.0];

	BasePlate = [Pad.x + Plug.x,Pad.y,Pad.z];


	//----------
	// Create parts

	module Stiffener() {

	difference() {
	union() {
	translate([-Pad.x,-BasePlate.y/2,0])
	cube(BasePlate,center=false);
	translate([0,-Pad.y/2,0])
	cube([Plug.x,Pad.y,Plug.z],center=false);
	}
	translate([-Protrusion,-Plug.y/2,-Protrusion])
	cube(Plug + [2*Protrusion,0,Plug.z],center=false);
	}

	}

	//----------
	// Build them

	Stiffener();

view raw LitUp LED Light Pad.scad hosted with ❤ by GitHub

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