Category: Machine Shop

Mechanical widgetry

Smithsonian’s Apollo 11 Command Module

An old friend asked for a copy of the Smithsonian’s Apollo 11 Command Module. I started with a tiny 1:80 version to check feasibility:

Apollo 11 CM – 1-80 scale

It’s obviously not printable in one piece without a ton of support, so I chopped off the heatsink and printed the parts separately in the obvious orientation:

Apollo 11 CM – 1-80 scale – split – Slic3r preview

And glued them back together:

Apollo 11 CM – clamping

That worked well enough, even without locating pins, to give me confidence that it’d come out all right.

There’s plenty of gimcrackery surrounding the upper airlock:

Apollo 11 CM – 1-40 scale – top – Slic3r preview

Most of which simply vanished at 1:80 scale:

Apollo 11 CM – 1-80 scale – top detail

I made another cut just below the top of the capsule and ran off a 1:40 scale version that came out somewhat better, but it was still ugly:

Apollo 11 CM – 1-40 scale – mortar detail

Much to my astonishment, the grab rail over the side hatch, between the two parachute motars, came out well every time.

The giant 1:20 scale version would require something over 24 hours of printing, so I went with 1:30 in three pieces:

Apollo 11 CM – 1-30 scale – sections

The top had pretty good detail:

Apollo 11 CM – 1-30 scale – top section – 1

Another view:

Apollo 11 CM – 1-30 scale – top section – 2

Gluing the parts together made it ready for cleanup / finishing / painting:

Apollo 11 CM – 1-30 scale – assembled

Which he’s better at than I ever will be…

Natural PETG probably isn’t the right plastic for that kind of model, but it’s what I had on hand.

Enjoy!

2016-09-07
Cast Iron Pan Electrolysis Stripping

Our cast iron pans need seasoning, so I decided to start with full-metal-jacket electrolysis stripping, rather than soaking them in oven cleaner / smogging the kitchen with the self-cleaning oven / actually doing any work. The electrolysis setup involves the big battery charger and a bucket of sodium carbonate solution:

Cast iron pan electrolysis – setup

Although the charger has a 40 A capacity, the small pan bubbles along merrily at a self-limited 7 A:

Cast iron pan electrolysis – bucket

The anode is a big sheet of steel that was once an EMI shield in a big PC case. The side facing the pan corroded very quickly, but the outside remains in good shape and I think it’ll suffice for the medium and large pans.

After two hours, only the crustiest bits of the crust remained:

Cast iron pan electrolysis – 2 hours

Those flakes fell right off after a few pokes from my demolition scraper; definite anticlimax, that.

Another hour in the tank cleaned the handle and removed a few other spots; it now sports a layer of flash rust that’ll require another pass after I strip the other two pans…

2016-09-05

Miniblind Cord Caps

After smashing one of the cord pulls between the sash and the frame:

The glittery PETG looks surprisingly good in the sunlight that will eventually change it into dullness. The black flecks come from optical effects in the plastic, not the usual burned PETG snot.

The solid model is basically a hull around two “spheres”, truncated on top & bottom:

Miniblind cord cap - solid model — Miniblind cord cap – solid model

The interior has a taper to accommodate the knot, but they’re chunky little gadgets:

Miniblind cord cap - solid model - bottom — Miniblind cord cap – solid model – bottom

I thought the facets came out nicely, even if they’re mostly invisible in the picture.

Each pull should build separately to improve the surface finish, so I arranged five copies in sequence from front to back:

Miniblind cord cap - 5 sequential - Slic3r preview — Miniblind cord cap – 5 sequential – Slic3r preview

If you’re using an M2, the fans hanging off the front of the filament drive housing might come a bit too close for comfort, so rotate ’em upward and out of the way.

If you remove the interior features and flip ’em upside down, they’d work well in Spiral Vase mode. You’d have to manually drill the top hole, though, because a hole through the model produces two shells.

The OpenSCAD source code as a GitHub Gist:

	// Cap for miniblind cord
	// Ed Nisley KE4ZNU – August 2016

	//- Extrusion parameters – must match reality!

	ThreadThick = 0.25;
	ThreadWidth = 0.40;

	Protrusion = 0.1;

	HoleWindage = 0.2;

	//——
	// Dimensions

	OD1 = 0;
	OD2 = 1;
	LENGTH = 2;

	Cap = [9.0,16.0,25.0];

	Cord = [2.5,7.0,Cap[LENGTH] – 5];

	NumSides = 8;

	//———————-
	//- Build it

	difference() {

	hull() { // overall shape
	translate([0,0,Cap[LENGTH] – Cap[OD1]/2])
	sphere(d=Cap[OD1],$fn=NumSides);
	translate([0,0,0.5*Cap[OD2]/2])
	sphere(d=Cap[OD2],$fn=2*NumSides); // round the bottom just a bit
	}

	translate([0,0,-Cap[LENGTH]/2]) // trim bottom
	cube([2Cap[OD2],2Cap[OD2],Cap[LENGTH]],center=true);

	translate([0,0,Cap[LENGTH] + 0.8*Cap[OD1]]) // trim top (arbitrarily)
	cube([2Cap[OD1],2Cap[OD1],2*Cap[OD1]],center=true);

	translate([0,0,-Protrusion])
	cylinder(d=Cord[OD1],h=(Cap[LENGTH] + 2*Protrusion),$fn=NumSides);

	translate([0,0,-Protrusion])
	cylinder(d1=Cord[OD2],d2=Cord[OD1],h=(Cord[LENGTH] + Protrusion),$fn=NumSides);
	}

view raw Miniblind cord cap.scad hosted with ❤ by GitHub

2016-09-03

Kenmore Progressive Vacuum Tool Adapters: First Failure

I picked up a horsehair dust brush from eBay as a lightweight substitute for the Electrolux aluminum ball, discovered that an adapter I’d already made fit perfectly, did the happy dance, and printed one for the brush. That worked perfectly for half a year, whereupon:

Dust Brush Adapter - broken parts — Dust Brush Adapter – broken parts

It broke about where I expected, along the layer lines at the cross section where the snout joins the fitting. You can see the three perimeter shells I hoped would strengthen the part:

Dust Brush Adapter - layer separation — Dust Brush Adapter – layer separation

That has the usual 15% 3D Honeycomb infill, although there’s not a lot area for infill.

There’s obviously a stress concentration there and making the wall somewhat thicker (to get more plastic-to-plastic area) might suffice. I’m not convinced the layer bonding would be good enough, even with more wall area, to resist the stress; that’s pretty much a textbook example of how & where 3D printed parts fail.

That cross section should look like this:

Dust Brush Adapter - Snout infill - Slic3r preview — Dust Brush Adapter – Snout infill – Slic3r preview

Anyhow, I buttered the snout’s broken end with JB Kwik epoxy, aligned the parts, and clamped them overnight:

Dust Brush Adapter - clamping — Dust Brush Adapter – clamping

The source code now has a separate solid model for the dust brush featuring a slightly shorter snout; if when the epoxy fails, we’ll see how that changes the results. I could add ribs and suchlike along the outside, none of which seem worth the effort right now. Fairing the joint between those two straight sections would achieve the same end, with even more effort, because OpenSCAD.

The OpenSCAD source code as a GitHub Gist:

	// Kenmore vacuum cleaner nozzle adapters
	// Ed Nisley KE4ZNU August 2016

	// Layout options

	Layout = "DustBrush"; // MaleFitting CoilWand FloorBrush CreviceTool ScrubbyTool LuxBrush DustBrush

	//- Extrusion parameters must match reality!
	// Print with +1 shells and 3 solid layers

	ThreadThick = 0.25;
	ThreadWidth = 0.40;

	HoleWindage = 0.2;

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

	Protrusion = 0.1; // make holes end cleanly

	//———————-
	// Dimensions

	ID1 = 0; // for tapered tubes
	ID2 = 1;
	OD1 = 2;
	OD2 = 3;
	LENGTH = 4;

	OEMTube = [35.0,35.0,41.7,40.5,30.0]; // main fitting tube
	EndStop = [OEMTube[ID1],OEMTube[ID2],47.5,47.5,6.5]; // flange at end of main tube

	FittingOAL = OEMTube[LENGTH] + EndStop[LENGTH];

	$fn = 12*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);
	}


	//——————-
	// Male fitting on end of Kenmore tools
	// This slides into the end of the handle or wand and latches firmly in place

	module MaleFitting() {

	Latch = [40,11.5,5.0]; // rectangle latch opening
	EntryAngle = 45; // latch entry ramp
	EntrySides = 16;
	EntryHeight = 15.0; // lower edge on inside of fitting

	KeyRadius = 1.0;

	translate([0,0,6.5])
	difference() {
	union() {
	cylinder(d1=OEMTube[OD1],d2=OEMTube[OD2],h=OEMTube[LENGTH]); // main tube

	hull() // insertion guide
	for (i=[-(6.0/2 – KeyRadius),(6.0/2 – KeyRadius)],
	j=[-(28.0/2 – KeyRadius),(28.0/2 – KeyRadius)],
	k=[-(26.0/2 – KeyRadius),(26.0/2 – KeyRadius)])
	translate([(i – (OEMTube[ID1]/2 + OEMTube[OD1]/2)/2 + 6.0/2),j,(k + 26.0/2 – 1.0)])
	sphere(r=KeyRadius,$fn=8);

	translate([0,0,-EndStop[LENGTH]]) // wand tube butts against this
	cylinder(d=EndStop[OD1],h=EndStop[LENGTH] + Protrusion);
	}

	translate([0,0,-OEMTube[LENGTH]]) // main bore
	cylinder(d=OEMTube[ID1],h=2OEMTube[LENGTH] + 2Protrusion);

	translate([0,-11.5/2,23.0 – 5.0]) // latch opening
	cube(Latch);

	translate([OEMTube[ID1]/2 + EntryHeight/tan(90-EntryAngle),0,0]) // latch ramp
	translate([(Latch[1]/cos(180/EntrySides))cos(EntryAngle)/2,0,(Latch[1]/cos(180/EntrySides))sin(EntryAngle)/2])
	rotate([0,-EntryAngle,0])
	intersection() {
	rotate(180/EntrySides)
	PolyCyl(Latch[1],Latch[0],EntrySides);
	translate([-(2*Latch[0])/2,0,-Protrusion])
	cube(2*Latch[0],center=true);
	}
	}
	}

	//——————-
	// Refrigerator evaporator coil wand

	module CoilWand() {

	union() {
	translate([0,0,50.0])
	rotate([180,0,0])
	difference() {
	cylinder(d1=EndStop[OD1],d2=42.0,h=50.0);
	translate([0,0,-Protrusion])
	cylinder(d1=35.0,d2=35.8,h=100);
	}
	translate([0,0,50.0 – Protrusion])
	MaleFitting();
	}
	}


	//——————-
	// Samsung floor brush

	module FloorBrush() {

	union() {
	translate([0,0,60.0])
	rotate([180,0,0])
	difference() {
	union() {
	cylinder(d1=EndStop[OD1],d2=32.4,h=10.0);
	translate([0,0,10.0 – Protrusion])
	cylinder(d1=32.4,d2=30.7,h=50.0 + Protrusion);
	}
	translate([0,0,-Protrusion])
	cylinder(d1=28.0,d2=24.0,h=100);
	}
	translate([0,0,60.0 – Protrusion])
	MaleFitting();
	}
	}


	//——————-
	// Crevice tool

	module CreviceTool() {

	union() {
	translate([0,0,60.0])
	rotate([180,0,0])
	difference() {
	union() {
	cylinder(d1=EndStop[OD1],d2=32.0,h=10.0);
	translate([0,0,10.0 – Protrusion])
	cylinder(d1=32.0,d2=30.4,h=50.0 + Protrusion);
	}
	translate([0,0,-Protrusion])
	cylinder(d1=28.0,d2=24.0,h=100);
	}
	translate([0,0,60.0 – Protrusion])
	MaleFitting();
	}
	}

	//——————-
	// Mystery brush

	module ScrubbyTool() {

	union() {
	translate([0,0,60.0])
	rotate([180,0,0])
	difference() {
	union() {
	cylinder(d1=EndStop[OD1],d2=31.8,h=10.0);
	translate([0,0,10.0 – Protrusion])
	cylinder(d1=31.8,d2=31.0,h=50.0 + Protrusion);
	}
	translate([0,0,-Protrusion])
	cylinder(d1=26.0,d2=24.0,h=100);
	}
	translate([0,0,60.0 – Protrusion])
	MaleFitting();
	}
	}

	//——————-
	// eBay horsehair dusting brush

	module DustBrush() {

	union() {
	translate([0,0,40.0])
	rotate([180,0,0])
	difference() {
	union() {
	cylinder(d1=EndStop[OD1],d2=31.8,h=10.0);
	translate([0,0,10.0 – Protrusion])
	cylinder(d1=31.6,d2=31.8,h=30.0 + Protrusion);
	}
	translate([0,0,-Protrusion])
	cylinder(d1=26.0,d2=24.0,h=100);
	}
	translate([0,0,40.0 – Protrusion])
	MaleFitting();
	}
	}


	//——————-
	// Electrolux brush ball

	module LuxBrush() {

	union() {
	translate([0,0,30.0])
	rotate([180,0,0])
	difference() {
	union() {
	cylinder(d1=EndStop[OD1],d2=30.8,h=10.0);
	translate([0,0,10.0 – Protrusion])
	cylinder(d1=30.8,d2=30.0,h=20.0 + Protrusion);
	}
	translate([0,0,-Protrusion])
	cylinder(d1=25.0,d2=23.0,h=30 + 2*Protrusion);
	}
	translate([0,0,30.0 – Protrusion])
	MaleFitting();
	}
	}



	//———————-
	// Build it!

	if (Layout == "MaleFitting")
	MaleFitting();

	if (Layout == "CoilWand")
	CoilWand();

	if (Layout == "FloorBrush")
	FloorBrush();

	if (Layout == "CreviceTool")
	CreviceTool();

	if (Layout == "DustBrush")
	DustBrush();

	if (Layout == "ScrubbyTool")
	ScrubbyTool();

	if (Layout == "LuxBrush")
	LuxBrush();

view raw Kenmore Wand Bushings.scad hosted with ❤ by GitHub

2016-08-24

Kenmore Model 158: Needle Lights, Now With Moah LEDs

The first pass at retrofitting SMD LEDs to light the needle area in Mary’s Model 158 sewing machine worked well enough:

Kenmore 158 Needle Light – heatsink

However, she wanted more light on the right side of the needle, so now she has it:

Needle LEDs – front

That’s without any LEDs along the front and back of the arm, hence the dark pool beyond the sewing machine’s base.

Those are the same 5050 warm white LEDs I used on the other side:

Needle LEDs – lower right

Seen without the glare:

Needle LEDs – bottom

They’re mounted on a 32 mil brass strip from the shimstock stash, carefully hand-bent and twisted to match the curvature of the arm, and held in place with JB Kwik steel-filled epoxy for good heat conduction to the aluminum arm. One can argue with the epoxy oozing out from under the brass, but it’s invisible from above.

No construction photos, alas, because I made this in a white-hot frenzy one afternoon and managed to not take any pix during the entire session. Call it working in the flow, OK?

All four SMD LEDs sit in epoxy blobs that isolate them from the brass strip, with 26 AWG solid wire “bus bars” soldered to the top of their terminals and a length of that lovely PTFE-insulated miniature coax leading off into the endcap. More epoxy encloses all the wiring & connections to provide a surprisingly smooth surface that shouldn’t snag the fabric.

The power supply uses an 18 W 120 VAC to 12 VDC brick intended for small LED installations:

Needle LEDs power supply – exterior

The AC comes from the same zip cord that formerly supplied the original 15 W incandescent bulb in the endcap, so the new lights behave the same way: push the power button to turn on the machine and the LEDs pop on just like they should. I put quick-disconnect terminals in the AC line to make it removable, although those need some sort of insulated plug to cover the exposed blades inside their housing.

Inside the black box, a small boost supply steps the voltage up to just under the nominal operating level of 21 VDC:

Needle LEDs power supply – interior

You can just see the adjusting screw hole in front of the AC brick in the overall view.

The DC output exits in the middle of the far side, through a coax jack epoxied to the base.

As before, all six LEDs run in parallel at (for now) 18.5 VDC and maybe 50 mA each, for a total of 300 mA, and seem fearsomely bright even at that. We can now tune for best light as needed.

This is a major major major improvement over the previous tangle of wires stuck on the outside of the machine, with all the wiring internal to the arm and the power supply out of sight under the sewing table.

After an hour, the arm above the four LEDs runs 13 °C above ambient and the endcap over the two LED heatsink is 6 °C over ambient. The AC supply runs at 104 °C and its plastic case offers no provision for heatsinking. All in all, things are warm and not hazardous.

I haven’t retrofit this machine with LED strips along the front & back of the arm, as those may not be needed with the intense needle lighting; the NisLite desk lamp may suffice for area illumination.

2016-08-23
FG085 Function Generator

The topic of function generators came up at Squidwrench a while ago (Sophi was tinkering with LCD shutters) and I finally picked up one of those JYE Tech FG085 DDS function generators to see how they work:

FG085 Fn Gen – in case

Short answer: adequate, if you’re not too fussy.

The board arrived with a bizarre solder defect. It seems a solder stalk yanked one terminal off a ceramic SMD caps:

FG085 – Solder stalk – C26

The schematic and adjacent parts suggested the victim was a 10 uF cap, so I replaced it with one from my stash that worked fine.

However, after soldering enough of the switches to do something useful, the board wouldn’t power up. With a bit of poking around, I discovered the power jack had +15 V from the wall wart, but the center terminals on the DPDT power switch that should have been connected to the jack showed maybe 0.3 V. Jumpering around the failed via and a short trace on the bottom surface let the board power up correctly:

FG085 – Jumpered power trace

If you’re building one of these, solder one pin of each switch, push all the switch caps in place, shove the faceplate over all of them, tape it to the PCB, make sure all the switches are push-able, then solder the remainder of the switch pins. If you do them one by one, you’re certain to end up with a few mis-aligned switches that will either prevent the faceplate from sliding over them or wedge firmly against the side of their assigned hole. Just sayin’.

It lives in a case from Thingiverse:

FG085enclosure – 1268379

I tweaked the dimensions slightly to fit the (slightly larger, possibly new, maybe tolerance-eased) front panel, but the bottom mounting screw hole spacing depends on the front panel size, not a specific set of dimensions, leading me to relocate those holes by abrasive adjustment. I didn’t bother with the lid (which doesn’t clear the BNC jack anyway) or the printed plastic feet (having a supply of silicone rubber feet).

The fancy vent gridwork along the sides printed surprisingly well, even in PETG. I’d have gone with larger slots, although I doubt the thing really needs vents in the first place.

The DDS sine wave output is rough, to say the least:

FG085 Fn Gen – 60 kHz sine

The spectrum shows oodles of harmonic content:

FG085 Fn Gen – 60 kHz sine – spectrum

A closer look:

FG085 Fn Gen – 60 kHz sine – spectrum – detail

Stepping back a bit shows harmonics of (and around) the 2.5 MHz DDS sampling frequency:

FG085 Fn Gen – 60 kHz sine – spectrum – 10 MHz

For comparison, my old Fordham FG-801 analog function generator has nice smooth harmonics:

FG-801 Fn Gen – 60 kHz sine – spectrum

Closer in:

FG-801 Fn Gen – 60 kHz sine – spectrum – detail

Of course, that crusty old analog dial doesn’t provide nearly the set-ability of a nice digital display.

2016-08-19
External Li-Ion Pack: More Sawing

Two of the external Li-Ion battery packs I’m using with the bike radios seemed to fail quickly after being charged, so I sawed them open to check the state of the cells. This time I used the fine-tooth cutoff blades, rather than a coarse slitting saw:

Li-Ion pack – sawing case

As before, a 2 mm depth-of-cut, done 0.25 mm per pass after the first millimeter, seems about right. I didn’t saw the front of the case near the jack, which proved to be a mistake; the interlocked case halves need cutting.

No cell trouble found, which leads me to suspect an intermittent short in the battery-to-radio cable that trips the battery protection circuit. The spare cables went into hiding during the shop cleanout, so I can’t swap in a known-good cable just yet; of course, the existing cable behaves perfectly on the bench. The suspect cable is now on my bike and, if the problem follows the cable, further surgery will be in order.

For the record, the insides look like this:

Li-Ion pack – interior

The cell label seems to show a 2004 date code:

Li-Ion pack – cell label

Given that I got them on closeout in early 2010, it definitely isn’t 2014.

Unlike some of the other cheap batteries around here, they’ve been spectacularly successful!

2016-08-17