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Posts Tagged Thing-O-Matic

Helmet Mirror Mount: Elevation Set Screw Slide

The elevation tension adjustment on both our bike helmet mirror mounts have become a bit sloppy. That’s no surprise, because I expected the tiny set screw in the tiny square hole near the top to eventually wear a depression in the ABS plastic arc upon which it bears:

Helmet mirror mount - 3D model - Fit layout

Helmet mirror mount – 3D model – Fit layout

The only surprise was that it took four years. That’s far longer than all of the commercial mirror and their mounts lasted; this one’s definitely a keeper.

So I got to do something I planned pretty much from the beginning of the project: cut a snippet of phosphor bronze spring stock to go between the Elevation mount and the arc, then bend the ends bent inward so they don’t slash an errant fingertip:

Helmet mirror mount - elevation slide

Helmet mirror mount – elevation slide

Slipped in place, the ends look like they stick out anyway, but they’re really just about flush:

Helmet mirror mount - El slide in place

Helmet mirror mount – El slide in place

Tightening the set screw pushes the strip against the arc, where it provides enough resistance to prevent slipping and enough smoothness for easy adjustment.

While I had the mounts up on the repair stand, I unscrewed the mirror shaft and snugged up the Azimuth pivot screw by a micro-smidgen to tighten that motion.

Four years ago, those ABS parts popped off the much-hacked Thing-O-Matic’s platform. The M2 produces somewhat better-looking results, but that yellow plastic has a certain charm…

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CNC Workshop 2015: Practical Solid Modeling with OpenSCAD

HP Plotter Pen Polygon

HP Plotter Pen Polygon

This afternoon at the CNC Workshop, I’ll be bootstrapping folks into creating 3D-printable solid models with Openscad.

The presentation in PDF form:

Practical Solid Modeling for 3D Printing with OpenSCAD – CNC Workshop 2015

The OpenSCAD source code for the exercises, in case you don’t want to type along:

Practical Solid Modeling for 3D Printing with OpenSCAD – Models.zip.odt

When you download that file, you’ll get something ending in .zip.odt. Rename it to remove the .odt extension, because it’s really a ZIP file; WordPress doesn’t allow users to uploads ZIP files.

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Search Engine Optimization: Replacement Shelf Bracket Whirlpool Freezer

If I were selling those brackets, I’d be rich:

Search Engine Optimization - Freezer Shelf Bracket

Search Engine Optimization – Freezer Shelf Bracket

Now, that looks like Search Engine Optimization it is to die for! Google will give you a different set of pictures, but I own that all-important top row.

Alas, anybody can just print their own…

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Large Spool Adapter: Right-angle Version

Mary recently learned that large spools of thread have a cross-wound lay that should feed over the end, not from the side as do ordinary stack-wound spools. So I built a right-angle adapter that fits over the not-quite-vertical spool pin on the sewing machine and aims directly at the thread tensioner:

Large spool adapter - on sewing machine

Large spool adapter – on sewing machine

The solid model shows off the fluted rod that passes through the spool:

Large Spool Adapter - solid model - mount

Large Spool Adapter – solid model – mount

It’s more impressive from the other end:

Large Spool Adapter - solid model - spool end

Large Spool Adapter – solid model – spool end

The first pass at the rod had six flutes, but that seemed unreasonably fine; now it has four. The round base on the rod provides more griptivity to the platform while building and has enough space for the two alignment pins that position it in the middle of the dome:

Large Spool Adapter - solid model - alignment holes

Large Spool Adapter – solid model – alignment holes

The dome gets glued to the rod base plate:

Large spool adapter - clamped

Large spool adapter – clamped

The spool pin hole is a snug fit around the pin on the sewing machine, because otherwise it would tend to rotate until the spool pointed to the rear of the machine. The fluted rod is a snug friction fit inside the (cardboard) spool. Some useful dimensions:

  • Spool pin (on Model 158): 5 mm OD, 40 mm tall
  • Large spool cores: 16 mm ID, 27 mm OD, 70 mm long

I had all manner of elaborate plans to make an expanding fluted rod, but came to my senses and built the simple version first. If that rod isn’t quite big enough, I can build another adapter, just like this one, only slightly larger. The source code includes a 0.5 mm taper, which may suffice.

Back in the day, shortly after the Thing-O-Matic started producing dependable results, one of the very first things I made was a simple adapter to mount large spools on the pin in the most obvious way:

Large spool adapter - old TOM version

Large spool adapter – old TOM version

Now we all know better than that, my OpenSCAD-fu has grown stronger, and the M2 produces precise results. Life is good!

The OpenSCAD source code:

// Large thread spool adapter
// Ed Nisley - KE4ZNU - August 2014

Layout = "Show";			// Build Show Spindle Spool

Gap = 10.0;					// between pieces in Show

//- Extrusion parameters must match reality!
//  Print with 4 shells and 3 solid layers

ThreadThick = 0.20;
ThreadWidth = 0.40;

HoleWindage = 0.2;			// extra clearance

Protrusion = 0.1;			// make holes end cleanly

AlignPinOD = 1.70;			// assembly alignment pins: filament dia

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

//----------------------
// Dimensions

LEN = 0;											// subscripts for cylindrical objects
ID = 1;
OD = 2;

Spindle = [40.0,5.0,14.0];							// spool spindle on sewing machine
Spool = [70.0,16.0,27.0];							// spool core

Taper = 0.50;										// spool diameter increase at base

CottonRoll = [65.0,Spool[OD],45.0];					// thread on spool

Mount = [Spindle[LEN],(Spindle[ID] + 4*ThreadWidth),1.0*Spool[ID]];

Flutes = 4;
Flange = [2.0,Spool[OD],Spool[OD]];

ScrewHole = [10.0,4.0 - 0.7,5.0];					// retaining screw

PinOC = Spool[ID]/4;								// alignment pin spacing

//----------------------
// 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) {

  RangeX = floor(100 / Space);
  RangeY = floor(125 / Space);

	for (x=[-RangeX:RangeX])
	  for (y=[-RangeY:RangeY])
		translate([x*Space,y*Space,Size/2])
		  %cube(Size,center=true);

}

//- Locating pin hole with glue recess
//  Default length is two pin diameters on each side of the split

module LocatingPin(Dia=AlignPinOD,Len=0.0) {
	
	PinLen = (Len != 0.0) ? Len : (4*Dia);
	
	translate([0,0,-ThreadThick])
		PolyCyl((Dia + 2*ThreadWidth),2*ThreadThick,4);

	translate([0,0,-2*ThreadThick])
		PolyCyl((Dia + 1*ThreadWidth),4*ThreadThick,4);
		
	translate([0,0,-(Len/2 + ThreadThick)])
		PolyCyl(Dia,(Len + 2*ThreadThick),4);

}

//----------------------
// Spindle 

module SpindleMount() {

	render(convexity=4)
	difference() {
		union() {
			resize([0,0,Mount[OD]])							// spool backing plate
				translate([0,CottonRoll[OD]/2,0])
					sphere(d=CottonRoll[OD],center=true);
			translate([0,CottonRoll[OD]/4,0])				// mounting post
				rotate([90,0,0])
					cylinder(d=Mount[OD],h=CottonRoll[OD]/2,center=true);
		}
		
		translate([0,(2*Mount[LEN] - Protrusion),Mount[OD]/4])				// punch spindle hole
			rotate([90,0,0])
//				PolyCyl(Spindle[ID],2*Mount[LEN],6);
				cylinder(d=Spindle[ID],h=2*Mount[LEN],$fn=6);
				
		for (i=[-1,1]) {									// punch alignment pin holes
			translate([i*PinOC,CottonRoll[OD]/2,0])
					LocatingPin(Len=Mount[OD]/3);
		}
				
		translate([0,0,-CottonRoll[OD]])					// remove half toward spool
			cube(2*CottonRoll[OD],center=true);
	}

}

//----------------------
// Spool holder

module SpoolMount() {	

	difference() {
	
		union() {
				
			translate([0,0,(Flange[LEN] - Protrusion)])
				difference() {
					cylinder(d1=(Spool[ID] + Taper),d2=Spool[ID],h=Spool[LEN],$fn=2*Flutes);						// fit spool ID
					
					for (a=[0 : 360/Flutes : 360-1])						// create flutes
						rotate(a + 180/Flutes)
							translate([Spool[ID]/2,0,-Protrusion])
								rotate(180/16)
								cylinder(r=Spool[ID]/4,h=(Spool[LEN] + 2*Protrusion),$fn=16);
								
					translate([0,0,(Spool[LEN] - ScrewHole[LEN])])			// punch screw hole
						PolyCyl(ScrewHole[ID],(ScrewHole[LEN] + Protrusion),6);

				}
			cylinder(d=Flange[OD],h=Flange[LEN]);							// base flange
		}
		
		for (i=[-1,1])												// punch alignment pin holes
			translate([0,i*PinOC,0])								//  ... orients solid flange up
					LocatingPin(Len=Flange[LEN]);	
	}

}


ShowPegGrid();

if (Layout == "Spindle") {
	SpindleMount();
}
if (Layout == "Spool") {
	SpoolMount();
}

if (Layout == "Show") {
	translate([0,Mount[OD]/4,2.0]) {
		rotate([90,0,0])
			SpindleMount();
		translate([0,Gap,CottonRoll[OD]/2])
			rotate([-90,0,0]) rotate(90)
				SpoolMount();
	}
	color("Orange") {
		translate([0,0,2])
			cylinder(d=Spindle[ID],h=Spindle[LEN],$fn=6);
		cylinder(d=Spindle[OD],h=2.0,$fn=18);
	}
		
}

if (Layout == "Build") {
	translate([-5,0,0])
		rotate(90)
			SpindleMount();
	translate([Flange[OD]/2,0,0])
			SpoolMount();
}

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Fit Test Blocks for 3D Printers: OpenSCAD Version

During one of my recent presentations, somebody asked about the accuracy of 3D printed parts, which reminded me of another member of Coasterman’s Essential Calibration Set: the perimeter width/thickness test block. Back in the day, calibrating the extruder meant getting the actual ratio of the thread width to its thickness to match the ideal value you told Skeinforge to use; being a bit off meant that the final dimensions weren’t quite right.

But when I got it right, the Thing-O-Matic printed a test block with considerable success, despite the horrible retraction zittage:

Perimeter Calibration Block - yellow 1.10 rpm 0.33 0.66 mm

Perimeter Calibration Block – yellow 1.10 rpm 0.33 0.66 mm

Alas, feeding the STL to Slic3r showed that it was grossly non-manifold, and none of the automated repair programs produced good results. Turns out it’s an STL created from a Sketchup model, no surprise there, and the newer slicers seem less tolerant of crappy models.

Sooo, here’s a new version built with OpenSCAD:

Fit Test Blocks - build view

Fit Test Blocks – build view

You get three blocks-and-plugs at once, arranged in all the useful orientations, so you can test all the fits at the same time. They come off the platform about like you’d expect:

Fit test blocks

Fit test blocks

I tweaked the code to make the plugs longer than you see there; the short ones were mighty tough to pry out of those slots.

I ran the plugs across a fine file to clean the sides, without removing any base material, and the plugs fit into the slots with a firm push. I’d do exactly the same thing for a CNC milled part from the Sherline, plus breaking the edges & corners.

The plugs doesn’t fit exactly flush in the recesses for the two models on the right side of that first image, because the edges and corners aren’t beveled to match each other. It’s pretty close and, if it had to fit exactly, you could make it work with a few more licks of the file. The left one, printed with the slot on the top surface, fits exactly as flush as the one from the Thing-O-Matic.

Of course, there’s a cheat: the model allows 0.1 mm of internal clearance on all sides of the plug:

Fit Test Block - show view

Fit Test Block – show view

The outside dimensions of all the blocks and plugs are dead on, within ±0.1 mm of nominal. You’d want to knock off the slight flange at the base and bevel the corners a bit, but unless it must fit inside something else, each object comes off the platform ready to use.

Feel free to dial that clearance up or down to suit your printer’s tolerances.

The OpenSCAD source code:

// Fit test block based on Coasterman's perimeter-wt.stl
//	http://www.thingiverse.com/thing:5573
//	http://www.thingiverse.com/download:17277
// Ed Nisley - KE4ZNU - May 2014

Layout = "Show";

//- Extrusion parameters must match reality!
//  Print with 2 shells and 3 solid layers

ThreadThick = 0.20;
ThreadWidth = 0.40;

Protrusion = 0.1;			// make holes end cleanly

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

//----------------------
// Dimensions

Clearance = 0.1;

PlugSize = [10.0,10.0,25.0];
BlockSize = [25.0,13.0,20.0];

PlugOffset = 10.0;

//----------------------
// Useful routines

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

  RangeX = floor(100 / Space);
  RangeY = floor(125 / Space);

	for (x=[-RangeX:RangeX])
	  for (y=[-RangeY:RangeY])
		translate([x*Space,y*Space,Size/2])
		  %cube(Size,center=true);

}

module Block() {
	difference() {
		translate([0,0,BlockSize[2]/2])
			cube(BlockSize,center=true);
		translate([0,PlugSize[1] - PlugSize[1]/2 - BlockSize[1]/2,-PlugOffset])
			Plug(Clearance);
	}
}

module Plug(Clear = 0.0) {
	minkowski() {
		translate([0,0,PlugSize[2]/2])
			cube(PlugSize,center=true);
		if (Clear > 0.0)
			cube(Clear,center=true);
	}
}

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

ShowPegGrid();

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

if (Layout == "Plug")
	Plug();

if (Layout == "Show") {
	Block();
	translate([0,PlugSize[1] - PlugSize[1]/2 - BlockSize[1]/2,-PlugOffset])
		Plug();
}

if (Layout == "Build") {
	Block();
	translate([0,-15,0])
		Plug();

	translate([-30,0,0]) {
		translate([0,-BlockSize[1]/2,BlockSize[1]/2])
			rotate([-90,0,0])
				Block();
		translate([-PlugSize[2]/2,-15,PlugSize[0]/2])
			rotate([0,90,0])
				Plug();
	}

	translate([30,0,0]) {
		translate([0,0,BlockSize[2]])
			rotate([180,0,180])
				Block();
		translate([-PlugSize[2]/2,-15,PlugSize[1]/2])
			rotate([90,0,90])
				Plug();
	}

}

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Boneheads Raven Skull: Extruder Contamination, Continued

The Boneheads Raven Skull demo came out reasonably well, albeit in a reduced size, on the Squidwrench Frank-o-Squid:

TOM286 - Raven Skull on platform

TOM286 – Raven Skull on platform

So I ran off a full-size version on the M2 for comparison:

Raven Skull - on M2 platform

Raven Skull – on M2 platform

The extruder apparently contained a gobbet of black PLA, left over from the Pink Panther Woman, that managed to hang on inside until the very tip of the beak:

Raven Skull - beak contamination

Raven Skull – beak contamination

Close inspection found two black strands closer to the base of the printed parts:

Raven Skull - black contamination

Raven Skull – black contamination

The rear of the skull joins the front just behind the eye sockets, where the solid bottom layers make a visible contrast with the air behind the perimeter threads elsewhere. Refraction darkens some of the threads, but the two black patches stand out clearly.

If it weren’t natural PLA, those flaws wouldn’t be nearly so noticeable.

Were I doing this stuff for a living, I might dedicate a hot end (or an entire extruder) to each color and be done with it.

All in all, the printed quality is about as good as I could expect from a glorified glue gun.

The extreme slowdown while printing the tip of the beak pushed Pronterface’s remaining time estimate over the edge:

Boneheads - Raven - Pronterface time estimate

Boneheads – Raven – Pronterface time estimate

I’m not sure what the correct value should be …

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Pink Panther Woman: Extruder Contamination

The Pink Panther Woman is my reference standard (*) for smooth perimeters and zitless filament retraction:

Pink Panther Woman - left

Pink Panther Woman – left

That’s vastly improved since the Thing-O-Matic’s last attempt:

PPW - outie zits

PPW – outie zits

Done in natural PLA, as it seems the previous version also walked off:

Pink Panther Woman - natural PLA

Pink Panther Woman – natural PLA

The attentive reader will note an odd red stripe on the left leg of the black PLA version. Here’s a closer look:

Pink Panther Woman - black with red contamination - detail

Pink Panther Woman – black with red contamination – detailPink Panther Woman – black with red contamination – detail

I had recently changed from red to black PLA and, as usual, purged the extruder with a few hundred millimeters of black filament, until it emerged pure black. Alas, I forgot to wipe the outside of the nozzle:

Pink Panther Woman - black - contaminated nozzle

Pink Panther Woman – black – contaminated nozzle

That red blob produced the red tab on the neck, as you can see if you look carefully at the first picture.

There are very few visible imperfections in either object: the state of DIY 3D printing is pretty good.

(*) Does anyone know of similar male figures suitable for this purpose? That torso seems to be about the extent of Thingiverse’s offerings.

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