M2 – Page 21 – The Smell of Molten Projects in the Morning

Step2 Garden Seat: Replacement Seat

A pair of Step2 rolling garden seats (they have a new version) served in Mary’s gardens long enough to give their seat panels precarious cracks:

Step2 Seat - OEM seat — Step2 Seat – OEM seat

The underside was giving way, too:

Step2 Seat - cracks — Step2 Seat – cracks

We agreed the new seat could be much simpler, although it must still hinge upward, so I conjured a pair of hinges from the vasty digital deep:

Rolling Cart Hinges - solid model - bottom — Rolling Cart Hinges – solid model – bottom

The woodpile disgorged a slab of 1/4 inch = 6 mm plywood (used in a defunct project) of just about the right size and we agreed a few holes wouldn’t be a problem for its projected ahem use case:

Step2 Seat - assembled — Step2 Seat – assembled

The screw holes on the hinge tops will let me run machine screws all the way through, should that be necessary. So far, a quartet of self-tapping sheet metal (!) screws are holding firm.

Rolling Cart Hinges - solid model - top — Rolling Cart Hinges – solid model – top

A closer look at the hinges in real life:

Step2 Seat - top view — Step2 Seat – top view

The solid model now caps the holes; I can drill them out should the need arise.

From the bottom:

Step2 Seat - bottom view — Step2 Seat – bottom view

Three coats of white exterior paint make it blindingly bright in the sun, although we expect a week or two in the garden will knock the shine right off:

Step2 Seat - painted — Step2 Seat – painted

After the first coat, I conjured a drying rack from a bamboo skewer, a cardboard flap, and some hot-melt glue:

Step2 Seat - drying fixture — Step2 Seat – drying fixture

Three small scars on the seat bottom were deemed acceptable.

The OpenSCAD source code as a GitHub Gist:

	// Hinge brackets for rolling garden stool
	// Ed Nisley – KE4ZNU – 2019-06

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

	Support = true;

	/* [Hidden] */

	ThreadThick = 0.20;
	ThreadWidth = 0.40;

	HoleWindage = 0.2;

	Protrusion = 0.1; // make holes end cleanly

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

	//———————-
	// Dimensions

	SeatThick = 6.0; // seat panel above cart body

	HingePin = [11.5,12.0,7.0]; // ID = tip OD = base

	HingeOffset = 8.0; // hinge axis above cart body (larger than radius!)
	HingeBolster = [5.0,24.0,SeatThick]; // backing block below hinge

	Block = [25.0,HingeOffset + 30.0,23.0]; // Z = above cart body

	Screw = [3.8,11.0,2.5]; // self-tapping #8 OD=head LENGTH=head thickness
	ScrewOC = 15.0; // spacing > greater than head OD
	ScrewOffset = Block.y/2 – (ScrewOC/2 + Screw[OD]/2 + HingeOffset); // space for head behind hinge

	BlockRadius = 7.0; // corner rounding

	//———————-
	// 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 block shape
	// X axis collinear with hinge axes, hinge base at X=0

	module HingeBlock() {

	PinSides = 3*4;
	PinSupport = [HingePin[LENGTH] – 2ThreadWidth,0.6HingeOffset,HingePin[OD]]; // pre-rotated

	union() {
	translate([Protrusion,Block.y/2 – HingeOffset,HingeOffset])
	rotate([0,-90,0])
	rotate(180/PinSides)
	cylinder(d=HingePin[OD],h=HingePin[LENGTH] + Protrusion,$fn=PinSides);
	difference() {
	hull() {
	translate([Block.x – BlockRadius,-(Block.y/2 – BlockRadius),Block.z – BlockRadius])
	rotate(180/PinSides)
	sphere(r=BlockRadius/cos(180/PinSides),$fn=PinSides);
	translate([0,-(Block.y/2 – BlockRadius),Block.z – BlockRadius])
	rotate([0,90,0]) rotate(180/PinSides)
	cylinder(r=BlockRadius/cos(180/PinSides),h=Block.x/2,$fn=PinSides);
	translate([Block.x – BlockRadius,(Block.y/2 – BlockRadius),Block.z – BlockRadius])
	sphere(r=BlockRadius/cos(180/PinSides),$fn=PinSides);
	translate([0,(Block.y/2 – BlockRadius),Block.z – BlockRadius])
	rotate([0,90,0]) rotate(180/PinSides)
	cylinder(r=BlockRadius/cos(180/PinSides),h=Block.x/2,$fn=PinSides);
	translate([0,-Block.y/2,0])
	cube([Block.x,Block.y – HingeOffset,Block.z/2],center=false);
	translate([0,Block.y/2 – HingeOffset,HingeOffset])
	rotate([0,90,0]) rotate(180/PinSides)
	cylinder(r=HingeOffset/cos(180/PinSides),h=Block.x,$fn=PinSides);
	}
	translate([Block.x/2 + HingeBolster.x,0,(SeatThick – Protrusion)/2])
	cube([Block.x,2*Block.y,SeatThick + Protrusion],center=true);
	translate([0,-HingeBolster.y,(SeatThick – Protrusion)/2])
	cube([3*Block.x,Block.y,SeatThick + Protrusion],center=true);
	for (j=[-1,1])
	translate([Block.x/2,jScrewOC/2 + ScrewOffset,-4ThreadThick])
	rotate(180/8)
	PolyCyl(Screw[ID],Block.z,8);
	}
	}

	if (Support) { // totally ad-hoc
	color("Yellow") render(convexity=4)
	difference() {
	translate([-(PinSupport.x/2 + 2*ThreadWidth),Block.y/2 – PinSupport.y/2,HingeOffset])
	cube(PinSupport,center=true);
	translate([Protrusion,Block.y/2 – HingeOffset,HingeOffset])
	rotate([0,-90,0])
	rotate(180/PinSides)
	cylinder(d=HingePin[OD] + 2ThreadThick,h=2HingePin[LENGTH],$fn=PinSides);
	for (i=[-1:1])
	translate([i4ThreadWidth – HingePin[LENGTH]/2,
	Block.y/2 – (PinSupport.y + 1*ThreadThick),
	HingeOffset])
	cube([2ThreadWidth,2PinSupport.y,2*PinSupport.z],center=true);
	}
	}
	}

	module Blocks(Hand = "Left") {
	if (Hand == "Left")
	HingeBlock();
	else
	mirror([1,0,0])
	HingeBlock();
	}

	//- Build it

	if (Layout == "Block")
	HingeBlock();

	if (Layout == "Show") {
	translate([1.5*HingePin[LENGTH],0,0])
	Blocks("Left");
	translate([-1.5*HingePin[LENGTH],0,0])
	Blocks("Right");
	}

	if (Layout == "Build") {
	translate([0,-Block.z/2,Block.y/2])
	rotate([-90,0,0]) {
	translate([1.5*HingePin[LENGTH],0,0])
	Blocks("Left");
	translate([-1.5*HingePin[LENGTH],0,0])
	Blocks("Right");
	}

	}

view raw Rolling Cart Hinges.scad hosted with ❤ by GitHub

This original doodle gives the key dimensions, apart from the rounded rear edge required so the seat can pivot vertically upward:

Cart Hinge - dimension doodle — Cart Hinge – dimension doodle

The second seat looks just like this one, so life is good …

2019-07-19

Drag Knife Blade Ejector Handle

The LM12UU drag knife holder buries the blade ejector pin deep inside the machinery:

Drag Knife - LM12UU ground shaft - assembled — Drag Knife – LM12UU ground shaft – assembled

So a handle with a pin makes sense:

It’s a variant Sherline tommy bar handle, so there’s not much to say about it.

The dark butt end comes from the traces of the black filament I used for the previous part. Even after flushing half a meter of orange through the hot end, you’ll still see some contamination, even with the same type of plastic. Doesn’t make much difference here, though.

2019-07-16

Threaded Brass Inserts: Test to Destruction

With an outmoded LM12UU linear bearing drag knife mount on hand, I threaded an M4 screw into each brass insert, lined it up on a hole in a homebrew (by a long-gone machinist, not me) steel bench block, and applied pressure with the drill press until the insert tore out:

Brass Insert Retention test - A B — Brass Insert Retention test – A B

The retina-burn orange ring is printed in PETG with my usual slicer settings: three perimeter threads, three top and bottom layers, and 15% 3D honeycomb infill. That combination is strong enough and stiff enough for essentially everything I do around here.

The insert on the left came out of its hole carrying its layer of epoxy: the epoxy-to-hole bond failed first. Despite that, punching it out required enough force to convince me it wasn’t going anywhere on its own.

The column of plastic around the insert standing up from the top fits into the central hole (hidden in the picture) in the bench block. Basically, the edge of the hole applied enough shear force to the plastic to break the infill before the epoxy tore free, with me applying enough grunt to the drill press quill handle to suggest I should get a real arbor press if I’m going to keep doing this.

The third insert maintained a similar grip, as seen from the left:

Brass Insert Retention test - C left — Brass Insert Retention test – C left

And the right:

Brass Insert Retention test - C right — Brass Insert Retention test – C right

The perimeter threads around the hole tore away from the infill, with the surface shearing as the plastic column punched through.

Bottom line: a dab of epoxy anchors an insert far better than the 3D printed structure around it can support!

2019-07-12

MPCNC Collet Pen Holder: LM12UU Edition

Encouraged by the smooth running of the LM12UU drag knife mount, I chopped off another length of 12 mm shaft:

LM12UU Collet Pen Holder - sawing shaft — LM12UU Collet Pen Holder – sawing shaft

The MicroMark Cut-off saw was barely up to the task; I must do something about its craptastic “vise”. In any event, the wet rags kept the shaft plenty cool and the ShopVac hose directly behind the motor sucked away all of the flying grit.

The reason I used an abrasive wheel: the shaft is case-hardened and the outer millimeter or two is hard enough to repel a carbide cutter:

LM12UU Collet Pen Holder - drilling shaft — LM12UU Collet Pen Holder – drilling shaft

Fortunately, the middle remains soft enough to drill a hole for the collet pen holder, which I turned down to a uniform 8 mm (-ish) diameter:

LM12UU Collet Pen Holder - turning collet body — LM12UU Collet Pen Holder – turning collet body

Slather JB Kwik epoxy along the threads, insert into the shaft, wipe off the excess, and it almost looks like a Real Product:

LM12UU Collet Pen Holder - finished body — LM12UU Collet Pen Holder – finished body

The far end of the shaft recesses the collet a few millimeters to retain the spring around the pen body, which will also require a knurled ring around the outside so you (well, I) can tighten the collet around the pen tip.

Start the ring by center-drilling an absurdly long aluminum rod in the steady rest:

M12UU Collet Pen Holder - center drilling — M12UU Collet Pen Holder – center drilling

Although it’s not obvious, I cleaned up the OD before applying the knurling tool:

LM12UU Collet Pen Holder - knurling — LM12UU Collet Pen Holder – knurling

For some unknown reason, it seemed like a Good Idea to knurl without the steady rest, perhaps to avoid deepening the ring where the jaws slide, but Tiny Lathe™ definitely wasn’t up to the challenge. The knurling wheels aren’t quite concentric on their bores and their shafts have plenty of play, so I got to watch the big live center and tailstock wobbulate as the rod turned.

With the steady rest back in place, drill out the rod to match the shaft’s 12 mm OD:

All my “metric” drilling uses hard-inch drills approximating the metric dimensions, of course, because USA.

Clean up the ring face, file a chamfer on the edge, and part it off:

LM12UU Collet Pen Holder - parting ring — LM12UU Collet Pen Holder – parting ring

Turn some PVC pipe to a suitable length, slit one side so it can collapse to match the ring OD, wrap shimstock to protect those lovely knurls, and face off all the ugly:

LM12UU Collet Pen Holder - knurled ring facing — LM12UU Collet Pen Holder – knurled ring facing

Tweak the drag knife’s solid model for a different spring from the collection and up the hole OD in the plate to clear the largest pen cartridge in the current collection:

Collet Holder - LM12UU - solid model — Collet Holder – LM12UU – solid model

Convince all the parts to fly in formation, then measure the spring rate:

LM12UU Collet Pen Holder - spring rate test — LM12UU Collet Pen Holder – spring rate test

Which works out to be 128 g + 54 g/mm:

LM12UU Collet Pen Holder - test plot - overview — LM12UU Collet Pen Holder – test plot – overview

I forgot the knurled ring must clear the screws and, ideally, the nyloc nuts. Which it does, after I carefully aligned each nut with a flat exactly tangent to the ring. Whew!

A closer look at the business end:

LM12UU Collet Pen Holder - test plot - detail — LM12UU Collet Pen Holder – test plot – detail

The shaft has 5 mm of travel, far more than enough for the MPCNC’s platform. Plotting at -1 mm applies 180 g of downforce; the test pattern shown above varies the depth from 0.0 mm in steps of -0.1 mm; anything beyond -0.2 mm gets plenty of ink.

Now I have a pen holder, a diamond scribe, and a drag knife with (almost) exactly the same “tool offset” from the alignment camera, thereby eliminating an opportunity to screw up.

The OpenSCAD source code as a GitHub Gist:

	// Collet pen cartridge holder using LM12UU linear bearing
	// Ed Nisley KE4ZNU – 2019-04-26
	// 2019-06 Adapted from LM12UU drag knife holder

	Layout = "Build"; // [Build, Show, Puck, Mount, Plate]

	/* [Extrusion] */

	ThreadThick = 0.25; // [0.20, 0.25]
	ThreadWidth = 0.40; // [0.40]

	/* [Hidden] */

	Protrusion = 0.1; // [0.01, 0.1]

	HoleWindage = 0.2;

	inch = 25.4;

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

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

	//- Adjust hole diameter to make the size come out right

	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);
	}

	//- Dimensions

	// Basic shape of DW660 snout fitting into the holder
	// Lip goes upward to lock into MPCNC mount

	Snout = [44.6,50.0,9.6]; // LENGTH = ID height
	Lip = 4.0; // height of lip at end of snout

	// Holder & suchlike

	Spring = [8.8,10.0,3*ThreadThick]; // compression spring loading knife blade

	PenShaft = 4.5; // hole to pass pen cartridge

	WallThick = 4.0; // minimum thickness / width

	Screw = [4.0,8.5,25.0]; // thread ID, washer OD, length

	Insert = [4.0,6.0,10.0]; // brass insert

	Bearing = [12.0,21.0,30.0]; // linear bearing body

	Plate = [PenShaft,Snout[OD] – WallThick,WallThick]; // spring reaction plate

	echo(str("Plate: ",Plate));

	SpringSeat = [0.56,7.2,2*ThreadThick]; // wire = ID, coil = OD, seat depth = length

	PuckOAL = max(Bearing[LENGTH],(Snout[LENGTH] + Lip)); // total height of DW660 fitting
	echo(str("PuckOAL: ",PuckOAL));
	Key = [Snout[ID],25.7,(Snout[LENGTH] + Lip)]; // rectangular key

	NumScrews = 3;

	//ScrewBCD = 2.0*(Bearing[OD]/2 + Insert[OD]/2 + WallThick);
	ScrewBCD = (Snout[ID] + Bearing[OD])/2;
	echo(str("Screw BCD: ",ScrewBCD));

	NumSides = 9*4; // cylinder facets (multiple of 3 for lathe trimming)

	module DW660Puck() {

	translate([0,0,PuckOAL])
	rotate([180,0,0]) {
	cylinder(d=Snout[OD],h=Lip/2,$fn=NumSides);
	translate([0,0,Lip/2])
	cylinder(d1=Snout[OD],d2=Snout[ID],h=Lip/2,$fn=NumSides);
	cylinder(d=Snout[ID],h=(Snout[LENGTH] + Lip),$fn=NumSides);
	translate([0,0,(Snout[LENGTH] + Lip) – Protrusion])
	cylinder(d1=Snout[ID],d2=2*WallThick + Bearing[OD],h=PuckOAL – (Snout[LENGTH] + Lip),$fn=NumSides);
	intersection() {
	translate([0,0,0*Lip + Key.z/2])
	cube(Key,center=true);
	cylinder(d=Snout[OD],h=Lip + Key.z,$fn=NumSides);
	}
	}
	}

	module MountBase() {

	difference() {
	DW660Puck();

	translate([0,0,-Protrusion]) // bearing
	PolyCyl(Bearing[OD],2*PuckOAL,NumSides);

	for (i=[0:NumScrews – 1]) // clamp screws
	rotate(i*360/NumScrews)
	translate([ScrewBCD/2,0,-Protrusion])
	rotate(180/8)
	PolyCyl(Insert[OD],2*PuckOAL,8);
	}
	}

	module SpringPlate() {
	difference() {
	cylinder(d=Plate[OD],h=Plate[LENGTH],$fn=NumSides);

	translate([0,0,-Protrusion]) // pen cartridge hole
	PolyCyl(PenShaft,2*Plate[LENGTH],NumSides);

	translate([0,0,Plate[LENGTH] – Spring[LENGTH]]) // spring retaining recess
	PolyCyl(Spring[OD],Spring[LENGTH] + Protrusion,NumSides);

	for (i=[0:NumScrews – 1]) // clamp screws
	rotate(i*360/NumScrews)
	translate([ScrewBCD/2,0,-Protrusion])
	rotate(180/8)
	PolyCyl(Screw[ID],2*PuckOAL,8);

	if (false)
	for (i=[0:NumScrews – 1]) // coil positioning recess
	rotate(i*360/NumScrews)
	translate([ScrewBCD/2,0,-Protrusion])
	rotate(180/8)
	PolyCyl(SpringSeat[OD],SpringSeat[LENGTH] + Protrusion,8);

	}
	}

	//—–
	// Build it

	if (Layout == "Puck")
	DW660Puck();

	if (Layout == "Plate")
	SpringPlate();

	if (Layout == "Mount")
	MountBase();

	if (Layout == "Show") {
	MountBase();
	translate([0,0,1.6*PuckOAL])
	rotate([180,0,0])
	SpringPlate();
	}

	if (Layout == "Build") {
	translate([0,Snout[OD]/2,PuckOAL])
	rotate([180,0,0])
	MountBase();
	translate([0,-Snout[OD]/2,0])
	SpringPlate();
	}

view raw Collet Holder – LM12UU.scad hosted with ❤ by GitHub

2019-07-11

MPCNC Diamond Engraver: LM3UU Bearings, Second Pass

Having a single spring and a fixed upper plate works much better than the first version:

Diamond Scribe - LM3UU Rev 2 - overview — Diamond Scribe – LM3UU Rev 2 – overview

The (lubricated!) nyloc nuts under the plate provide a little friction and stabilize the whole affair.

The solid model has the same stylin’ tapered snout as the LM12UU drag knife mount:

Diamond Scribe - LM3UU bearings — Diamond Scribe – LM3UU bearings

The spring seats in the plate recess, with the 3 mm shank passing through the hole as the tool holder presses the tip against the workpiece.

I diamond-filed a broken carbide end mill to make a slotting tool:

Diamond Scribe - LM3UU - Rev 2 - carbide notch tool — Diamond Scribe – LM3UU – Rev 2 – carbide notch tool

Lacking any better method (“a tiny clip spreader tool”), I rammed the Jesus clip the length of the shank with a (loose-fitting) chuck in the tailstock:

Diamond Scribe - LM3UU - Rev 2 - clip installation — Diamond Scribe – LM3UU – Rev 2 – clip installation

Even without nyloc nuts, the first test worked fine:

Diamond Scribe - LM3UU - Rev 2 - first light — Diamond Scribe – LM3UU – Rev 2 – first light

The 53 g/mm spring rate may be too low for serious engraving, but it suffices for subtle Guilloché patterns on scrap platters.

The OpenSCAD source code as a GitHub Gist:

	// Drag Knife Holder using LM12UU linear bearing
	// Ed Nisley KE4ZNU – 2019-04-26
	// 2019-05-09 LM3UU for diamond scribe
	// 2019-05-28 taper end, single spring around shaft

	Layout = "Build"; // [Build, Show, Puck, Mount, Plate]

	/* [Extrusion] */

	ThreadThick = 0.25; // [0.20, 0.25]
	ThreadWidth = 0.40; // [0.40, 0.40]

	/* [Hidden] */

	Protrusion = 0.1; // [0.01, 0.1]

	HoleWindage = 0.2;

	inch = 25.4;

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

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

	//- Adjust hole diameter to make the size come out right

	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);
	}

	//- Dimensions

	// Knife holder & suchlike

	KnifeBody = [3.0,9.0,2.0]; // washer epoxied to diamond shaft, with epoxy fillet

	Spring = [9.5,10.0,3*ThreadThick]; // compression spring around shaft, LENGTH = socket depth

	WallThick = 4.0; // minimum thickness / width

	Screw = [4.0,8.5,8.0]; // holding it all together, OD = washer

	Insert = [4.0,6.0,10.0]; // brass insert

	Bearing = [3.0,7.0,2*10.0 + WallThick]; // linear bearing body (pair + small gap)

	// Basic shape of DW660 snout fitting into the holder
	// Lip goes upward to lock into MPCNC mount

	Snout = [44.6,50.0,9.6]; // LENGTH = ID height
	Lip = 4.0; // height of lip at end of snout

	Plate = [KnifeBody[ID],Snout[OD] – WallThick,WallThick]; // spring reaction plate

	PuckOAL = max(Bearing[LENGTH],(Snout[LENGTH] + Lip)); // total height of DW660 fitting
	echo(str("PuckOAL: ",PuckOAL));
	Key = [Snout[ID],25.7,(Snout[LENGTH] + Lip)]; // rectangular key

	NumScrews = 3;

	ScrewBCD = 2.5*(Bearing[OD]/2 + Insert[OD]/2 + WallThick);

	NumSides = 9*4; // cylinder facets (multiple of 3 for lathe trimming)

	module DW660Puck() {

	translate([0,0,PuckOAL])
	rotate([180,0,0]) {
	cylinder(d=Snout[OD],h=Lip/2,$fn=NumSides);
	translate([0,0,Lip/2])
	cylinder(d1=Snout[OD],d2=Snout[ID],h=Lip/2,$fn=NumSides);
	cylinder(d=Snout[ID],h=(Snout[LENGTH] + Lip),$fn=NumSides);
	translate([0,0,(Snout[LENGTH] + Lip) – Protrusion])
	cylinder(d1=Snout[ID],d2=2*WallThick + Bearing[OD],h=PuckOAL – (Snout[LENGTH] + Lip),$fn=NumSides);
	intersection() {
	translate([0,0,0*Lip + Key.z/2])
	cube(Key,center=true);
	cylinder(d=Snout[OD],h=Lip + Key.z,$fn=NumSides);
	}
	}
	}

	module MountBase() {

	difference() {
	DW660Puck();

	translate([0,0,-Protrusion]) // bearing
	PolyCyl(Bearing[OD],2*PuckOAL,NumSides);

	for (i=[0:NumScrews – 1]) // clamp screws
	rotate(i*360/NumScrews)
	translate([ScrewBCD/2,0,-Protrusion])
	rotate(180/8)
	PolyCyl(Insert[OD],2*PuckOAL,8);
	}
	}

	module SpringPlate() {
	difference() {
	cylinder(d=Plate[OD],h=Plate[LENGTH],$fn=NumSides);

	translate([0,0,-Protrusion]) // ample shaft clearance
	PolyCyl(1.5KnifeBody[ID],2PuckOAL,NumSides);

	// translate([0,0,Plate[LENGTH] – KnifeBody[LENGTH]]) // flange, snug fit
	// PolyCyl(KnifeBody[OD],KnifeBody[LENGTH] + Protrusion,NumSides);

	translate([0,0,Plate[LENGTH] – Spring[LENGTH]]) // spring retainer
	PolyCyl(Spring[OD],Spring[LENGTH] + Protrusion,NumSides);

	for (i=[0:NumScrews – 1]) // clamp screws
	rotate(i*360/NumScrews)
	translate([ScrewBCD/2,0,-Protrusion])
	rotate(180/8)
	PolyCyl(Screw[ID],2*PuckOAL,8);
	}
	}

	//—–
	// Build it

	if (Layout == "Puck")
	DW660Puck();

	if (Layout == "Plate")
	SpringPlate();

	if (Layout == "Mount")
	MountBase();

	if (Layout == "Show") {
	MountBase();
	translate([0,0,1.5*PuckOAL])
	rotate([180,0,0])
	SpringPlate();
	}

	if (Layout == "Build") {
	translate([0,Snout[OD]/2,PuckOAL])
	rotate([180,0,0])
	MountBase();
	translate([0,-Snout[OD]/2,0])
	SpringPlate();
	}

view raw Diamond Scribe – LM3UU bearings.scad hosted with ❤ by GitHub

2019-06-28

Garden Soaker Hose Connector Repair

Two of Mary’s garden soaker hoses failed their pre-installation checks with leaks from around their connectors. The problem seemed to be a break in the hose inside the connector, with water spewing out of the connector around the hose. Having previously fixed a gash in another hose, I figured I might have some success at fixing these leaks.

The general idea is to squish enough silicone rubber inside the connector to seal around the hose, then clamp the hose and connector snugly enough to hold the rubber in place:

Soaker Hose Connector Clamp - Show view — Soaker Hose Connector Clamp – Show view

The enlarged recess fits around the brass connector shell, which is squashed loosely around the hose and from which the leaking water emerges. Of course, because this is a different hose, the previous model didn’t quite fit and I had to doodle up new geometry:

Soaker Hose Connector repair - Dimension doodle — Soaker Hose Connector repair – Dimension doodle

As before, I bandsawed aluminum backing plates to ensure the plastic didn’t get all bendy in the middle:

The hose clamp (!) around the connector on the far right ensures a split in the brass shell doesn’t get any larger.

They’ll spend the rest of their lives under the garden mulch, where nobody will ever see those bulky lumps. Life is good!

The OpenSCAD source code as a GitHub Gist:

	// Rubber Soaker Hose End Connector Clamp
	// Helps hold silicone rubber in connector
	// Ed Nisley KE4ZNU June 2019

	Layout = "Build"; // [Hose,Connector,Block,Show,Build]

	//- Extrusion parameters must match reality!

	/* [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);

	//———-
	// Dimensions
	// Hose lies along X axis

	Hose = [200,26.5,11.6]; // X=very long, Y=width, Z=overall height

	RimThick = 10.3; // outer sections
	RimOD = RimThick;
	RimFlatRecess = 1.0; // recess to front flat surface

	OuterOC = Hose.y – RimOD; // outer tube centers

	RecessM = 0.8; // back recess chord
	RecessC = OuterOC;
	RecessR = (pow(RecessM,2) + pow(RecessC,2)/4) / (2*RecessM);

	RidgeM = 1.6; // front ridge chord
	RidgeC = 7.5;
	RidgeR = (pow(RidgeM,2) + pow(RidgeC,2)/4) / (2*RidgeM);

	HoseSides = 12*4;

	Connector = [5.0,33.0,13.0]; // oval brass: X=snout Y=width Z=dia

	Block = [20.0,50.0,4.0 + Hose.z]; // overall splice block size
	echo(str("Block: ",Block));

	Kerf = 0.5; // cut through middle to apply compression

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

	// 8-32 stainless screws
	Screw = [4.1,8.0,3.0]; // OD = head LENGTH = head thickness
	Washer = [4.4,9.5,1.0];
	Nut = [4.1,9.7,6.0];

	CornerRadius = Washer[OD]/2;

	ScrewOC = Block.y – 2*CornerRadius;

	echo(str("Screw OC: x=",ScrewOC.x," y=",ScrewOC.y));

	//———————-
	// 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);
	}

	// Hose shape
	// This includes magic numbers measured from reality

	module HoseProfile() {

	rotate([0,-90,0])
	translate([0,0,-Hose.x/2])
	linear_extrude(height=Hose.x,convexity=4)
	difference() {
	union() {
	for (j=[-1,1]) // outer channels
	translate([0,j*OuterOC/2])
	circle(d=RimOD,$fn=HoseSides);
	translate([-RimOD/4,0]) // rear flat fill
	square([RimOD/2,OuterOC],center=true);
	translate([(RimOD/4 – RimFlatRecess),0]) // front flat fill
	square([RimOD/2,OuterOC],center=true);
	intersection() {
	translate([Hose.z/2,0])
	square([Hose.z,OuterOC],center=true);
	translate([-RidgeR + RimOD/2 – RimFlatRecess + RidgeM,0])
	circle(r=RidgeR,$fn=HoseSides);
	}
	}
	translate([-(RecessR + RimOD/2 – RecessM),0])
	circle(r=RecessR,$fn=2*HoseSides);
	}
	}

	// Outside shape of splice Block
	// Z centered on hose rim circles, not overall thickness through center ridge

	module SpliceBlock() {
	difference() {
	hull()
	for (i=[-1,1], j=[-1,1]) // rounded block
	translate([i(Block.x/2 – CornerRadius),j(Block.y/2 – CornerRadius),-Block.z/2])
	cylinder(r=CornerRadius,h=Block.z,$fn=4*8);
	for (j=[-1,1]) // screw holes
	translate([0,
	j*ScrewOC/2,
	-(Block.z/2 + Protrusion)])
	PolyCyl(Screw[ID],Block.z + 2*Protrusion,6);
	cube([2Block.x,2Block.y,Kerf],center=true); // slice through center
	}
	}

	// Splice block less hose

	module ShapedBlock() {
	difference() {
	SpliceBlock();
	HoseProfile();
	Connector();
	}
	}

	// Brass connector end

	module Connector() {
	translate([-(Block.x/2 + Protrusion),0,0])
	rotate([0,90,0])
	linear_extrude(height=Connector.x + Protrusion)
	hull()
	for (i = [-1,1])
	translate([0,i*(Connector.y – Connector.z)/2])
	circle(d=Connector.z);
	}


	//———-
	// Build them

	if (Layout == "Hose")
	HoseProfile();

	if (Layout == "Block")
	SpliceBlock();

	if (Layout == "Connector")
	Connector();

	if (Layout == "Show") {
	ShapedBlock();
	color("Green",0.25)
	HoseProfile();
	}

	if (Layout == "Build") {
	SliceOffset = 0;
	intersection() {
	translate([SliceOffset,0,Block.z/4])
	cube([4Block.x,4Block.y,Block.z/2],center=true);
	union() {
	translate([0,0.6*Block.y,Block.z/2])
	ShapedBlock();
	translate([0,-0.6*Block.y,Block.z/2])
	rotate([0,180,0])
	ShapedBlock();
	}
	}
	}

view raw Soaker Hose Connector Clamp.scad hosted with ❤ by GitHub

2019-06-27

Kitchen Blender Base Spacer

We don’t use the blender much, so the most recent bearing replacement continues to work. I never got around to re-making the overly long shaft spacer from the first bearing replacement, which I compensated for with a spacer kludge cut from a random chunk of bendy plastic sheet.

Which we put up with For. Eleven. Years.

The blender recently emerged from hiding and, with my solid modeling-fu cranked up to a dangerous chattering whine, I conjured a real spacer:

Blender base spacer - Slic3r preview — Blender base spacer – Slic3r preview

It pretty much disappears into the blender base, which is the whole point of the operation:

Blender base spacer - installed — Blender base spacer – installed

When the bearings fail again, I promise to make a proper shaft spacer and toss this bodge.

The OpenSCAD code as a GitHub Gist:

	// Kitchen blender base adapter
	// Ed Nisley KE4ZNU June 2019

	//- Extrusion parameters must match reality!

	/* [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;

	//———-
	// Just build it

	Spacer = [48.0,66.0,1.8]; // LENGTH raises blade holder
	Aligner = [Spacer[ID],52.0,Spacer[LENGTH] + 3.0]; // LENGTH locks into base ring

	NumSides = 434;

	//———-
	// Just build it

	difference() {
	union() {
	cylinder(d=Spacer[OD],h=IntegerMultiple(Spacer[LENGTH],ThreadThick),$fn=NumSides);
	cylinder(d=Aligner[OD],h=Aligner[LENGTH],$fn=NumSides);
	}
	translate([0,0,-Protrusion])
	cylinder(d=Spacer[ID],h=10*Aligner[LENGTH],$fn=NumSides);
	}

view raw Blender base spacer.scad hosted with ❤ by GitHub

Not that it really deserves so much attention …

2019-06-21

Tag: M2

Step2 Garden Seat: Replacement Seat

Drag Knife Blade Ejector Handle

Threaded Brass Inserts: Test to Destruction

MPCNC Collet Pen Holder: LM12UU Edition

MPCNC Diamond Engraver: LM3UU Bearings, Second Pass

Garden Soaker Hose Connector Repair

Kitchen Blender Base Spacer