M2 – Page 28 – The Smell of Molten Projects in the Morning

Propane Tank QD Fitting Adapter, PETG Edition

Smoking bacon during the winter months brought the third tank into play, requiring the POL-to-QD adapter I’d had in the drawer for just such an occasion. Not much to my surprise, the old PLA fitting adapter snapped along the layers near the outside end of the triangular snout:

So I ran off the two orange ones in PETG with six perimeter layers and 50% infill density:

Propane QD Adapter Tool - Slic3r — Propane QD Adapter Tool – Slic3r

Those should last roughly forever …

The OpenSCAD source code as a GitHub Gist:

	// Propane tank QD connector adapter tool
	// Ed Nisley KE4ZNU November 2012
	// 2018-04-08 toss MCAD includes overboard

	//- Extrusion parameters must match reality!
	// Print with about half a dozen perimeter threads and 50% infill

	ThreadThick = 0.25;
	ThreadWidth = 2.0 * ThreadThick;

	HoleWindage = 0.2;

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

	Protrusion = 0.1; // make holes end cleanly

	inch = 25.4;

	//———————-
	// Dimensions

	WrenchSize = (5/8) * inch; // across the flats
	WrenchThick = 10;

	NoseDia = 8.6;
	NoseLength = 9.0;

	LockDia = 12.5;
	LockRingLength = 1.0;
	LockTaperLength = 1.5;

	TriDia = 15.1;
	TriWide = 12.2; // from OD across center to triangle side
	TriOffset = TriWide – TriDia/2; // from center to triangle side
	TriLength = 9.8;

	NeckDia = TriDia;
	NeckLength = 4.0;

	//———————-
	// 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);
	}

	/*
	module ShowPegGrid(Space = 10.0,Size = 1.0) {

	Range = floor(50 / Space);

	for (x=[-Range:Range])
	for (y=[-Range:Range])
	translate([xSpace,ySpace,Size/2])
	%cube(Size,center=true);
	}
	*/

	//——————-
	// Build it…

	$fn = 4*6;

	//ShowPegGrid();

	union() {

	translate([0,0,(WrenchThick + NeckLength + TriLength – LockTaperLength – LockRingLength + Protrusion)])
	cylinder(r1=NoseDia/2,r2=LockDia/2,h=LockTaperLength);

	translate([0,0,(WrenchThick + NeckLength + TriLength – LockRingLength)])
	cylinder(r=LockDia/2,h=LockRingLength);



	difference() {
	union() {

	translate([0,0,WrenchThick/2])
	cube([WrenchSize,WrenchSize,WrenchThick],center=true);

	cylinder(r=TriDia/2,h=(WrenchThick + NeckLength +TriLength));

	cylinder(r=NoseDia/2,h=(WrenchThick + NeckLength + TriLength + NoseLength));
	}

	for (a=[-1:1]) {
	rotate(a*120)
	translate([(TriOffset + WrenchSize/2),0,(WrenchThick + NeckLength + TriLength/2 + Protrusion/2)])
	cube([WrenchSize,WrenchSize,(TriLength + Protrusion)],center=true);
	}
	}
	}

view raw Propane QD Adapter Tool.scad hosted with ❤ by GitHub

2018-04-17

MPCNC: Linear Bearing Pen Holder

The simplest way to push a pen (or similar thing) downward with constant force may be to hold it in a linear bearing with a weight on it, so I gimmicked up a proof-of-concept. The general idea is to mount the pen so its axis coincides with the DW660 spindle, so as to have the nib trace the same path:

DW660 Pen Holder - unweighted — DW660 Pen Holder – unweighted

The puck mimics the shape of the DW660 snout closely enough to satisfy the MPCNC’s tool holder:

DW660 Pen Holder - Slic3r — DW660 Pen Holder – Slic3r

The pen holder suffers from thin walls constrained by the 10 mm (-ish) pen OD and the 12 mm linear bearing ID, to the extent the slight infill variations produced by the tapered pen outline change the OD. A flock of 16 mm bearings, en route around the planet even as I type, should provide more meat.

In any event, 3D printing isn’t noted for its perfect surface finish, so I applied an epoxy layer and rotated the holder as it cured:

DW660 Pen Holder - epoxy coating — DW660 Pen Holder – epoxy coating

After letting it cure overnight, I ran a lathe tool along the length to knock down the high spots and set the OD to 11.9+ mm. Although the result turns out to be a surprisingly nice fit in the bearing, there’s no way epoxy can sustain the surface load required for the usual precision steel-on-steel fit.

A plastic pen in a plastic holder weighs 8.3 g, which isn’t quite enough to put any force on the paper. Copper weighs 9 g/cm³ = 9 mg/mm³ and 10 AWG wire is 2.54 mm OD = 5 mm², so it’s 45 mg/mm: to get 20 g, chop off 450 mm of wire.

I chopped off a bit more than that, straightened it, annealed it, and wound it around a random contestant from the Bucket o’ Sticks with an OD just over the pen OD:

DW660 Pen Holder - copper weight forming — DW660 Pen Holder – copper weight forming

The helix is 13.5 mm down the middle of the turns and 14 turns long (trimmed of the tail going into the chuck and fudging the tail sticking out as a partial turn), so it’s 593 mm long and should weigh 26.7 g. It actually weighs 27.6 g: close enough.

Which is enough to overcome stiction due to the holder’s surface roughness, but the mediocre epoxy-on-balls fit allows the pen point to wander a bit too much for good results.

The prospect of poking precise holes into 16 mm drill rod seems daunting, but, based on what I see here, it will produce much better results: rapid prototyping FTW!

The OpenSCAD source code as a GitHub Gist:

	// MPCNC Pen Holder for DW660 Mount
	// Ed Nisley KE4ZNU – 2018-03-05

	Layout = "Build"; // Build, Show
	// Puck, MountBase, BuildBase
	// Pen, PenAdapter, BuildAdapter

	/* [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

	WallThick = 3.0; // minimum thickness / width

	Screw = [3.0,7.0,25.0]; // holding it all together, OD = washer

	Insert = [3.0,4.4,4.5]; // brass insert

	Bearing = [12.0,21.0,30.0]; // LM12UU bearing body, ID = rod OD

	PenTravel = 5.0; // vertical pen travel allowance

	NumSides = 8*4; // cylinder facets

	//—–
	// Define shapes

	//– Sakura Micron fiber-point pen

	ExpRP = 0.30; // expand critical sections (by radius)

	//– pen locates in holder against end of outer body

	PenOutline = [
	[0,0], // 0 fiber pen tip
	[0.6/2,0.0],[0.6/2,0.9], // 1 … cylinder
	[1.5/2,0.9],[1.5/2,5.3], // 3 tip surround
	[4.7/2,5.8], // 5 chamfer
	[4.9/2,12.3], // 6 nose
	// [8.0/2,12.3],[8.0/2,13.1], // 7 latch ring
	// [8.05/2,13.1],[8.25/2,30.5], // 9 actual inner body
	[8.4/2 + ExpRP,12.3],[8.4/2 + ExpRP,30.5], // 7 inner body – clear latch ring
	[9.5/2 + ExpRP,30.9], // 9 outer body – location surface!
	[9.8/2 + ExpRP,60.0], // 10 outer body – length > Body
	[7.5/2,60.0], // 11 arbitrary length, much longer than bearing
	[7.5/2,59.0], // 12 end of reservoir
	[0,59.0] // 13 fake reservoir
	];

	PenNose = PenOutline[6][1];
	PenLocate = PenOutline[9][1];

	// 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
	Key = [Snout[ID],25.7,Snout[LENGTH] + Lip]; // rectangular key

	module DW660Puck() {

	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=Lip + Snout[LENGTH],$fn=NumSides);
	intersection() {
	translate([0,0,0*Lip + Key.z/2])
	cube(Key,center=true);
	cylinder(d=Snout[OD],h=Lip + Key.z,$fn=NumSides);
	}

	}

	module MountBase() {

	difference() {
	DW660Puck();
	translate([0,0,-Protrusion])
	PolyCyl(Bearing[OD],2*Bearing[LENGTH],NumSides);
	}
	}

	//– Sakura drawing pen body & polygon shape

	module Pen() {
	rotate_extrude($fn=NumSides)
	polygon(points=PenOutline);
	polygon(points=PenOutline);
	}

	//– Pen holder

	AdapterRing = [Bearing[ID],Bearing[OD],4.0];
	AdapterOAL = Bearing[LENGTH] + PenTravel + AdapterRing[LENGTH];

	module PenAdapter() {

	difference() {
	union() {
	PolyCyl(Bearing[ID],AdapterOAL,NumSides);
	translate([0,0,AdapterOAL – AdapterRing[LENGTH]])
	cylinder(d=AdapterRing[OD],h=AdapterRing[LENGTH],$fn=NumSides);
	}
	translate([0,0,-(PenNose + Protrusion)])
	Pen();
	}

	}

	//—–
	// Build it

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

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

	if (Layout == "Pen")
	Pen();

	if (Layout == "PenAdapter")
	PenAdapter();

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

	if (Layout == "BuildBase" \|\| Layout == "Build")
	translate([0,-Snout[OD]/2,0])
	MountBase();

	if (Layout == "BuildAdapter" \|\| Layout == "Build")
	translate([0,Snout[OD]/2,AdapterOAL])
	rotate([180,0,0])
	PenAdapter();

view raw Pen Holder – DW660 Mount.scad hosted with ❤ by GitHub

2018-04-04

MPCNC: USB Camera Mount With Lock Screw

It turned out the previous version of the USB camera mount lacked sufficient griptivity to hold the ball’s position against even moderate bumps, so the upper “half” is now tall enough to hold a lock screw directly over the ball:

MPCNC - USB Camera mount - lock screw - Slic3r — MPCNC – USB Camera mount – lock screw – Slic3r

It doesn’t look much different:

MPCNC - USB Camera Mount - lock screw — MPCNC – USB Camera Mount – lock screw

A view from the other side:

USB Camera - lock screw mount — USB Camera – lock screw mount

The previous iterations used Genuine 3M foam tape, which seemed too flexy for comfort. This one sits on a bed of hot melt glue and is absolutely rigid. We’ll see how long it survives.

Tightening the cap screw requires needle-nose pliers, because the whole affair has no room for a hex key.

The OpenSCAD source code as a GitHub Gist:

	// MPCNC USB Camera Mount
	// Ed Nisley KE4ZNU – 2018-02-22

	Layout = "Build"; // Build, Show

	/* [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

	WallThick = 3.0; // minimum thickness / width

	CameraStalk = [6.0 + 1.0,10.0 + HoleWindage,4.0]; // stalk OD, ball OD, stalk length
	CameraAngle = -5; // stalk tilt, negative = downward

	Screw = [3.0,7.0,25.0]; // holding it all together, OD = washer

	Insert = [3.0,4.4,4.5]; // brass insert
	Pusher = Insert[LENGTH] / 2; // plastic locking snippet

	UpperThick = IntegerMultiple(CameraStalk[OD]/2 + Insert[LENGTH] + Pusher + WallThick,ThreadThick);
	LowerThick = Screw[LENGTH] – UpperThick;

	MountBlock = [24.0,20.0,LowerThick + UpperThick];

	echo(str("Block: ",MountBlock));

	NumSides = 6*4;

	//—–
	// Define shapes

	// Camera mount, enlongated for E-Z differencing
	// Origin at center of ball, stalk along +X

	module Camera() {

	union() {
	sphere(d=CameraStalk[OD],$fn=NumSides);
	rotate([0,90 – CameraAngle,0])
	PolyCyl(CameraStalk[ID],3*CameraStalk[LENGTH],NumSides);
	}
	}

	// Mount block with all the cutouts
	// Ball centerline on XY plane = block split line

	module Mount(Half="All") {

	Rounding = 2.0; // corner radius

	ZShift = // block shift to remove unwanted half
	(Half == "Upper") ? -MountBlock.z/2 – 0*UpperThick :
	(Half == "Lower") ? MountBlock.z/2 + 0*LowerThick :
	2*MountBlock.z; // … want both halves, remove none

	difference() {
	hull()
	for (i=[-1,1], j=[-1,1]) {
	translate([i(MountBlock.x/2 – Rounding),j(MountBlock.y/2 – Rounding),(UpperThick – Rounding)])
	sphere(r=Rounding,$fn=3*4);
	translate([i(MountBlock.x/2 – Rounding),j(MountBlock.y/2 – Rounding),-(LowerThick – Rounding)])
	sphere(r=Rounding,$fn=3*4);
	}

	for (j=[-1,1])
	translate([-MountBlock.x/4,j*MountBlock.y/4,-(LowerThick + Protrusion)]) {
	PolyCyl(Insert[OD],Insert[LENGTH] + Protrusion,6);
	PolyCyl(Insert[ID],2*MountBlock.z,6);
	}

	translate([MountBlock.x/2 – (CameraStalk[OD]/2 + CameraStalk[LENGTH]),0,0]) {
	Camera();
	translate([0,0,UpperThick – (Insert[LENGTH] + WallThick)])
	PolyCyl(Insert[OD],Insert[LENGTH] + WallThick,6);
	PolyCyl(Insert[ID],2*UpperThick,6);
	}

	translate([0,0,ZShift])
	cube([2MountBlock.x,2MountBlock.y,MountBlock.z],center=true);
	}

	}

	//—–
	// Build it

	if (Layout == "Show")
	Mount("All");

	if (Layout == "Build") {
	translate([0,0.75*MountBlock.y,UpperThick])
	rotate([180,0,0])
	Mount("Upper");
	translate([0,-0.75*MountBlock.y,LowerThick])
	rotate([0,0,0])
	Mount("Lower");}

view raw USB Camera Mount.scad hosted with ❤ by GitHub

2018-03-28

Baofeng BL-5 Pack Rebuild

The 18650 cell protection PCBs with 8205 ICs arrived and seemed small enough to simply tuck into the gap between the rounded cells in the second Baofeng BL-5 pack:

Baofeng BL-5 - new protection PCB - wiring 1 — Baofeng BL-5 – new protection PCB – wiring 1

For whatever it might be worth, you’re looking at the only Baofeng battery pack containing an actual 10 kΩ thermistor, harvested from the benchtop Tray of Doom:

Baofeng BL-5 pack - thermistor — Baofeng BL-5 pack – thermistor

Unfortunately, the components on the PCB stuck up a bit too far from the cell surface and held the lid just slightly proud of the case. Applying pressure to lithium cells being a Bad Idea, I rearranged the layout by flipping the cells over, tucking the PCB components between the cells, and connecting everything with nickel tape instead of insulated wires:

Baofeng BL-5 - new protection PCB - wiring 2 — Baofeng BL-5 – new protection PCB – wiring 2

The snippets of manila paper and Kapton tape hold things apart and together, as needed. Looks ugly, fits better.

Pop it in the charger to reset the protection PCB lockout and it’s all good again.

2018-03-26

Baofeng BL-5 Battery Pack Base Dimensions

My original idea for the APRS + voice gadget was a snap-in battery pack replacement holding the circuit boards and connected to an external battery pack. A trio of dead Wouxun radios, plus the ready availability of 18650 lithium cells, suggested putting two cells in the backpack, along with the circuitry, and skipping the external pack.

Here’s the base of a Baofeng BL-5 pack overlaid with a 1 mm grid:

Baofeng BL-5 - Base with mm grid overlay — Baofeng BL-5 – Base with mm grid overlay

The grid is parallel to the case body and centered left-to-right, with a Y grid line set at the front face of the pack, where it’s also flush with the lid surface. You can read off the coordinates of all the points, feed them into your CAD model, and maybe, with a bit of care, get something 3D-print-able.

Haven’t used it yet, but it’s bound to come in handy at some point.

2018-03-25

MPCNC: Raspberry Pi Screw-down Case

Directly from 0110-M-P’s Thingiverse thing, because a Raspberry Pi in a 75 mm VESA mount case will work for me:

The hole fits a 25 mm fan, but the thing runs cool enough it should survive without forced air; think of it as a contingency. Mounting the case on standoffs seems like a Good Idea, however, as the bottom plate includes many vent slots for Good Circulation.

The top plate builds upside-down, so I had Slic3r add teeny support plugs inside the recessed screw holes. I think button-head screws would fit neatly in the recesses, but we’re obviously not in this for the looks.

The tiny white stud is a Reset switch hot-melt glued into the slot. I plan to just turn off the AC power after shutting the RPi down, so a power-on will suffice as a reset.

2018-03-11

MPCNC: Power Supply Brick Mount

A laptop-style power brick supplies 24 V for the MPCNC’s stepper motors, but I didn’t want it wandering around on the Basement Laboratory floor and getting in trouble, so a pair of brackets seemed in order:

Power Supply Brick Mount - trial fit — Power Supply Brick Mount – trial fit

They build flat on their backs to avoid support material:

Power Supply Brick Mount - Slic3r — Power Supply Brick Mount – Slic3r

The nicely rounded corners produce a very thin line of plastic on the first layer, so the model now has thicker base plates to improve the situation. A set of mouse ears would keep the tips pasted to the glass.

The OpenSCAD source code as a GitHub Gist:

	// Power Supply Brick brackets
	// Ed Nisley KE4ZNU 2018-02-26

	Layout = "Show";

	//– Extrusion parameters

	ThreadThick = 0.25;
	ThreadWidth = 0.4;

	HoleWindage = 0.3; // enlarge hole dia by this amount

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

	Protrusion = 0.1; // make holes look good and joints intersect properly

	//– Useful sizes

	inch = 25.4;

	Tap10_32 = 0.159 * inch;
	Clear10_32 = 0.190 * inch;
	Head10_32 = 0.373 * inch;
	Head10_32Thick = 0.110 * inch;
	Nut10_32Dia = 0.433 * inch;
	Nut10_32Thick = 0.130 * inch;

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

	//– Bracket Dimensions

	Brick = [170.0,66.0,40.0]; // overall size, add details in module

	Socket = [30.0,24.0]; // IEC power socket
	Cable = [6.0,15.0]; // DC output cable ID=wire OD=strain relief

	WallThick = 3.0; // default wall thickness
	BaseThick = 4.0;

	Screw = [5.1,10.0,3.0]; // screw size, more-or-less 10-32, OD & LENGTH for head

	NumSides = 3*4;

	//———————-
	// 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);
	}

	//———————-
	// Models



	module BrickMount(End="Both") {

	difference() {
	union() {
	hull() // main block
	for (i=[-1,1], j=[-1,1], k=[0,1])
	translate([i*(Brick.x/2 + WallThick – WallThick),
	j*(Brick.y/2 + WallThick – WallThick),
	k*(Brick.z + WallThick – WallThick)])
	sphere(r=WallThick,$fn=NumSides);
	hull() // screw flanges
	for (i=[-1,1], j=[-1,1])
	translate([i*(Brick.x/2 + WallThick – BaseThick),
	j(Brick.y/2 + WallThick + 2Screw[OD] – BaseThick),
	0])
	sphere(r=BaseThick,$fn=NumSides);
	}
	for (i=[-1,1], j=[-1,1]) // remove screw holes
	translate([i*(Brick.x/2 + WallThick – Screw[OD]),
	j*(Brick.y/2 + WallThick + Screw[OD]),
	-Protrusion])
	rotate(180/6)
	PolyCyl(Screw[ID],2*WallThick,6);

	translate([0,0,Brick.z/2]) // remove center part to leave ends
	cube([(Brick.x + 2WallThick – 4Screw[OD]),2Brick.y,2Brick.z],center=true);

	if (End == "Socket")
	translate([Brick.x/2,0,Brick.z/2]) // remove cable end to leave socket
	cube([(Brick.x + 2WallThick – 4Screw[OD]),2Brick.y,2Brick.z],center=true);

	if (End == "Cable")
	translate([-Brick.x/2,0,Brick.z/2]) // remove socket end to leave cable
	cube([(Brick.x + 2WallThick – 4Screw[OD]),2Brick.y,2Brick.z],center=true);

	translate([0,0,Brick.z/2 – Protrusion/2]) // remove power supply brick from interior
	cube(Brick + [0,0,Protrusion],center=true);
	translate([0,0,-Brick.z]) // remove below XY plane
	cube(2*Brick,center=true);

	translate([0,0,Brick.z/2]) // remove AC socket
	rotate([0,-90,0])
	rotate(90)
	linear_extrude(height=Brick.x,convexity=2)
	square(Socket,center=true);

	translate([0,0,Brick.z/2]) // remove DC cable
	rotate([0,90,0])
	rotate(180/8)
	PolyCyl(Cable[OD],Brick.x,8);
	translate([Brick.x/2,0,Brick.z/4 – Protrusion/2]) // … and wire slot
	cube([Brick.x,Cable[ID],Brick.z/2 + Protrusion],center=true);
	}

	}

	//———————-
	// Build it

	if (Layout == "Show")
	BrickMount("Both");

	if (Layout == "Build") {
	translate([5,0,Brick.x/2 + WallThick])
	rotate([0,90,0])
	BrickMount("Cable");
	translate([-5,0,Brick.x/2 + WallThick])
	rotate([0,-90,0])
	BrickMount("Socket");
	}

view raw Power Supply Brick Mount.scad hosted with ❤ by GitHub

2018-03-09

Tag: M2

Propane Tank QD Fitting Adapter, PETG Edition

MPCNC: Linear Bearing Pen Holder

MPCNC: USB Camera Mount With Lock Screw

Baofeng BL-5 Pack Rebuild

Baofeng BL-5 Battery Pack Base Dimensions

MPCNC: Raspberry Pi Screw-down Case

MPCNC: Power Supply Brick Mount