Tek Circuit Computer: Sawed Hairline Fixture

This is a fixture to hold a cursor for an Homage Tektronix Circuit Computer while a tiny circular saw blade cuts a narrow flat-bottomed trench:

Tek CC - sawed cursor - Sherline setup
Tek CC – sawed cursor – Sherline setup

Each of the 123 blocks is held to the Sherline tooling plate with a 10-32 SHCS in a little aluminum pin, with another threaded pin for the screw holding the fixture on the side. The minimal top clearance provided some of the motivation behind making those pins in the first place; there’s no room for the usual threaded stud sticking out of the block with a handful of washers under the nut.

The fixture has locating slots (scribbled with black Sharpie) to touch off the spindle axis and the saw blade at the XZ origin at the pivot hole center. Touching off the saw blade on the cursor surface sets Y=0, although only a few teeth will go ting, so the saw must be spinning.

I cut the first slot under manual control to a depth of 0.3 mm on a scrap cursor with a grotty engraved hairline:

Tek CC - first sawed cursor - detail
Tek CC – first sawed cursor – detail

It looks better than I expected with some red lacquer crayon scribbled into it:

Tek CC - first sawed cursor - vs scribed
Tek CC – first sawed cursor – vs scribed

A few variations of speed and depth seem inconclusive, although they look more consistent and much smoother than the diamond-drag engraved line with red fill:

Tek CC - sawed cursor test - magnified
Tek CC – sawed cursor test – magnified

The saw produces a ramp at the entry and exit which I don’t like at all, but the cut is, overall, an improvement on the diamond point.

The OpenSCAD source code as a GitHub Gist:

// Sawing fixtures for Tek Circuit Computer cursor hairline
// Ed Nisley KE4ZNU Jan 2021
// Rotated 90° and screwed to 123 blocks for sawing
Layout = "Show"; // [Show, Build, Cursor]
Gap = 4.0;
/* [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);
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,$fn=Sides);
}
//----------------------
// Dimensions
CursorHubOD = 1.0*inch; // must match SVG hub OD
CursorThick = 0.71; // including protective layers
HairlineMin = 48.4188; // extent of hairline
HairlineMax = 97.4250;
HairlineDepth = 0.20;
PocketDepth = 0.75*CursorThick; // half above surface for taping
PocketClear = 0.25; // E-Z insertion clearance
TableOC = [1.16*inch,1.16*inch]; // Sherline tooling plate grid
BlockOC = [(9/16)*inch,(9/16)*inch]; // 123 block hole grid
BlockOffset = [(3/8)*inch,(3/8)*inch]; // .. block edge to hole center
ScrewClear = 5.0; // … screw clearance
CursorOffset = [2*BlockOC.x,0,0]; // hub center relative to leftmost screw
FixtureGrid = [5*TableOC.x,0,0]; // size in Table grid units
Screws = [ // relative to leftmost screw
[0,0,0], // on table grid
CursorOffset, // on block grid
[FixtureGrid.x,0,0] // on table grid
];
echo(str("Screw centers: ",Screws));
CornerRad = 10.0; // corner radius
Fixture = [2*CornerRad + FixtureGrid.x,2*CornerRad + CursorHubOD,5.0];
echo(str("Fixture plate: ",Fixture));
//----------------------
// Import SVG of cursor outline
// Requires our CursorHubOD to match actual cut outline
// Hub center at origin
module CursorSVG(t=CursorThick,ofs=0.0) {
hr = CursorHubOD/2;
translate([-hr,-hr,0])
linear_extrude(height=t,convexity=3)
offset(r=ofs)
import(
file="/mnt/bulkdata/Project Files/Tektronix Circuit Computer/Firmware/TekCC-Cursor-Mark.svg",
center=false);
}
//----------------------
// Show-n-Tell cursor
module Cursor() {
difference() {
CursorSVG(CursorThick,0.0);
translate([0,0,-Protrusion])
rotate(180/6)
PolyCyl(ScrewClear,CursorThick + 2*Protrusion,6);
}
}
//----------------------
// Sawing fixture for cursor hairline
// Plate center at origin
module Fixture() {
difference() {
hull() // basic plate shape
for (i=[-1,1], j=[-1,1])
translate([i*(Fixture.x/2 - CornerRad),j*(Fixture.y/2 - CornerRad),0])
cylinder(r=CornerRad,h=Fixture.z,$fn=24);
translate([0,0,Fixture.z - ThreadThick/2 + Protrusion/2]) // will be Z=0 index
cube([2*Fixture.x,ThreadWidth,ThreadThick + Protrusion],center=true);
translate(-FixtureGrid/2) {
translate(CursorOffset + [0,0,Fixture.z - 2*PocketDepth])
difference() {
CursorSVG(2*PocketDepth + Protrusion,PocketClear);
CursorSVG(PocketDepth + Protrusion,-PocketClear);
}
translate([CursorOffset.x,0,Fixture.z - ThreadThick/2 + Protrusion/2]) // will be front X=0 index
cube([ThreadWidth,2*Fixture.y,ThreadThick + Protrusion],center=true);
translate([CursorOffset.x,Fixture.y/2 - ThreadThick/2 + Protrusion/2,0]) // will be top X=0 index
cube([ThreadWidth,ThreadThick + Protrusion,2*Fixture.z],center=true);
translate([CursorOffset.x + HairlineMin,0,Fixture.z - ThreadThick/2 + Protrusion/2]) // hairline min
cube([ThreadWidth,2*Fixture.y,ThreadThick + Protrusion],center=true);
translate([CursorOffset.x + HairlineMax,0,Fixture.z - ThreadThick/2 + Protrusion/2]) // hairline min
cube([ThreadWidth,2*Fixture.y,ThreadThick + Protrusion],center=true);
/*
# translate(CursorOffset + [0,0,Fixture.z - 2*ThreadThick]) { // alignment pips
for (x=[-20.0,130.0], y=[-30.0,0.0,30.0])
translate([x,y,0])
cylinder(d=4*ThreadWidth,h=1,$fn=6);
# for (x=[-30.0,130.0,150.0])
translate([x,0,0])
cylinder(d=4*ThreadWidth,h=1,$fn=6);
*/
for (pt=Screws)
translate(pt + [0,0,-Protrusion])
rotate(180/6)
PolyCyl(ScrewClear,Fixture.z + 2*Protrusion,6);
}
}
}
//----------------------
// Build it
if (Layout == "Cursor") {
Cursor();
}
if (Layout == "Show") {
rotate([0*90,0,0]) {
Fixture();
color("Green",0.3)
translate(-FixtureGrid/2 + CursorOffset + [0,0,Fixture.z + Gap])
Cursor();
}
}
if (Layout == "Build"){
// rotate(90)
Fixture();
}

Torchiere Lamp Shade 2

Three and a half years later, the shade on the living room’s other torchiere lamp crumbled at a touch:

Torchiere Lamp Shade 2 - crumbled
Torchiere Lamp Shade 2 – crumbled

Because I live in the future and had solved this problem in the past, eight hours of print time produced a second shade:

Torchiere Lamp Shade 2 - on platform
Torchiere Lamp Shade 2 – on platform

I sliced the same STL file with PrusaSlicer to get G-Code incorporating whatever configuration changes I’ve made to the M2 over the years and include any slicing algorithm improvements; the OpenSCAD code remains unchanged.

The as-printed shade had pretty much the same crystalline aspect as the first one:

Torchiere Lamp Shade 2 - no epoxy
Torchiere Lamp Shade 2 – no epoxy

Smoothing a layer of white-tinted epoxy over the interior while spinning it slowly in the mini-lathe calmed it down enough for our simple needs, although the picture I tried to take didn’t show much difference.

That was easy …

Photo Backdrop: Wingnut Upgrade

You’re supposed to secure the photo backdrop’s top crossbar to the uprights by fiddling with a wingnut, which you must do while reaching over your head. Emart apparently realized this operation was fraught with peril, because the package contains four wingnuts. After setting it up once, I replaced the wingnuts with finger-friendly knobs containing acorn nuts:

Photo Backdrop - thumbscrew vs printed knob
Photo Backdrop – thumbscrew vs printed knob

The upright pole ends in an M10×1.5 stud, which fits the biggest acorn nuts in the Warehouse Wing.

The knobs come from Thingiverse, although the OpenSCAD program required a bit of rework to make it compatible with the current version. Fiddling around with the Customizer parameters produced a Good Enough knob:

M10x1.5 Acorn Nut knob - solid model
M10x1.5 Acorn Nut knob – solid model

I pulled the acorn nut into the knob using the upright pole hardware to keep it aligned. Spin the wingnut on the stud “backwards”, add the washer, push the nut slightly into the knob to get it started, then thread it onto the stud:

Photo Backdrop - knob nut seating - 1
Photo Backdrop – knob nut seating – 1

Turn the knob to pull the nut inward until the stud hits the inside of the nut:

Photo Backdrop - knob nut seating - 2
Photo Backdrop – knob nut seating – 2

Unthread the nut a bit, run the wingnut out to meet the bottom of the knob, and repeat the operation until the nut bottoms out inside the knob:

Photo Backdrop - knob nut seated
Photo Backdrop – knob nut seated

Toss the wingnuts into the Warehouse Wing against later use.

Bonus project: on the other end of the upright, you’ll find it impossible to actually lock the leg carrier against the pole:

Photo Backdrop - tripod leg lock
Photo Backdrop – tripod leg lock

The plastic fitting is … generously … sized around the 25 mm OD upright pole and requires more compression than I could produce with my puny fingers. It turns out the 18 mm OD leg tube exactly fills the space available inside the fitting, so you (well, I) must squash the steel tube in order to close the fitting on the pole.

Remove the wingnut + screw to free the end of the leg, stick an inch of the leg into the bench vise’s soft jaws, and mash gently to about 16 mm across the holes; it’ll expand slightly in the other direction. Reassemble in reverse order and discover the thumbscrew now squeezes the fitting exactly as it should.

There might be more finishing to do when we actually hang a quilt from the stand, but at least it’s now usable.

Sheesh and similar remarks.

Photo Backdrop Clamp Pad Embiggening

We got a photo backdrop stand to hold Mary’s show-n-tell quilts during her quilting club meetings, but the clamps intended to hold the backdrop from the top bar don’t work quite the way one might expect. These photos snagged from the listing shows their intended use:

Emart Photo Backdrop - clamp examples
Emart Photo Backdrop – clamp examples

The clamp closes on the top bar with the jaws about 15 mm apart, so you must wrap the backdrop around the bar, thereby concealing the top few inches of whatever you intended to show. This doesn’t matter for a preprinted generic backdrop or a green screen, but quilt borders have interesting detail.

The clamps need thicker jaws, which I promptly conjured from the vasty digital deep:

Spring Clamp Pads - PS preview
Spring Clamp Pads – PS preview

The original jaws fit neatly into those recesses, atop a snippet of carpet tape to prevent them from wandering off:

Spring Clamp pads - detail
Spring Clamp pads – detail

They’re thick enough to meet in the middle and make the clamp’s serrated round-ish opening fit around the bar:

Spring Clamp pads - compared
Spring Clamp pads – compared

With a quilt in place, the clamps slide freely along the bar:

Spring Clamp pads - fit test
Spring Clamp pads – fit test

That’s a recreation based on actual events, mostly because erecting the stand wasn’t going to happen for one photo.

To level set your expectations, the “Convenient Carry Bag” is more of a wrap than a bag, without enough fabric to completely surround its contents:

Emart photo backdrop bag
Emart photo backdrop bag

I put all the clamps / hooks / doodads in a quart Ziploc baggie, which seemed like a better idea than letting them rattle around loose inside the wrap. The flimsy pair (!) of hook-n-loop straps don’t reach across the gap and, even extended with a few inches of double-sided Velcro, lack enough mojo to hold it closed against all the contents.

It’ll suffice for our simple needs, but …

The OpenSCAD source code as a GitHub Gist:

// Clamp pads for Emart photo backdrop clamps
// Ed Nisley KE4ZNU Jan 2021
/* [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);
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,$fn=Sides);
}
//----------------------
// Dimensions
OEMpad = [24.0,16.0,3.0]; // original pad
Pad = [35.0,25.0,8.0 + OEMpad.z]; // pad extension
PadOffset = [0,-3.0,0];
CornerRad = 3.0; // corner rounding
Gap = 3.0;
//----------------------
// Shape the pad
module BigPad() {
difference() {
hull()
for (i=[-1,1],j=[-1,1],k=[-1,1])
translate([i*(Pad.x/2 - CornerRad),j*(Pad.y/2 - CornerRad),k*(Pad.z/2 - CornerRad) + Pad.z/2])
sphere(r=CornerRad,$fn=6);
translate(PadOffset + [0,0,Pad.z - (OEMpad.z + Protrusion)/2])
cube(OEMpad + [HoleWindage,HoleWindage,Protrusion],center=true);
}
}
//----------------------
// Build a pair
translate([0,(Pad.y + Gap)/2,0])
BigPad();
translate([0,-(Pad.y + Gap)/2,0])
rotate(180)
BigPad();

Tek Circuit Computer: 3D Printed Cursor Milling Fixture

The original Tektronix Circuit Computer cursor was probably die-cut from a larger sheet carrying pre-printed hairlines:

Tek CC - genuine - detail
Tek CC – genuine – detail

Machining a punch-and-die setup lies well beyond my capabilities, particularly given the ahem anticipated volume, so milling seems the only practical way to produce a few cursors.

Attaching a cursor blank to a fixture with sticky tape showed that the general idea worked reasonably well:

Tek CC - Cursor blank on fixture
Tek CC – Cursor blank on fixture

However, the tape didn’t have quite enough griptivity to hold the edges completely flat against milling forces (a downcut bit might have worked better) and I found myself chasing the cutter with a screwdriver to hold the cursor in place. Worse, the tape’s powerful attraction to swarf made it a single-use item.

Some tinkering showed a single screw in the (pre-drilled) pivot hole, without adhesive underneath, lacked enough oomph to keep the far end of the cursor in place, which meant I had to think about how to hold it down with real clamps.

Which, of course, meant conjuring a fixture from the vasty digital deep. The solid model includes the baseplate, two cutting templates, and a clamping fixture for engraving the cursor hairline:

Cursor Fixture - build layout
Cursor Fixture – build layout

The perimeter of the Clamp template on the far left is 0.5 mm inside the cursor perimeter. Needing only one Clamp, I could trace it on a piece of acrylic, bandsaw it pretty close, introduce it to Mr Belt Sander for final shaping, and finally drill the hole:

Tek CC Cursor Fixture - clamp drilling
Tek CC Cursor Fixture – clamp drilling

The Rough template is 1.0 mm outside the cursor perimeter, so I can trace those outlines on a PET sheet:

Tek CC Cursor Fixture - Rough template layout
Tek CC Cursor Fixture – Rough template layout

Then cut the patterns with a scissors, stack ’em up, and tape the edges to keep them aligned:

TekCC Cursor Fixture - Rough template
TekCC Cursor Fixture – Rough template

Align the stack by feel, apply the Clamp to hold them in place, and secure the stack with a Sherline clamp:

Tek CC Cursor Fixture - outline rear clamp
Tek CC Cursor Fixture – outline rear clamp

The alert reader will note it’s no longer possible to machine the entire perimeter in one pass; more on that in a while.

The baseplate pretty much fills the entire Sherline tooling plate. It sports several alignment pips at known offsets from the origin at the center of the pivot hole:

Tek CC Cursor Fixture - touch-off point
Tek CC Cursor Fixture – touch-off point

Dropping the laser alignment dot into a convenient pip, then touching off X and Y to the known offset sets the origin without measuring anything. Four screws in the corners align the plate well enough to not worry about angular tweakage.

The OpenSCAD source code as a GitHub Gist:

// Machining fixtures for Tek Circuit Computer cursor
// Ed Nisley KE4ZNU Jan 2021
Layout = "Show"; // [Show, Build, Cursor, Clamp, Rough, Engrave]
/* [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);
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,$fn=Sides);
}
//----------------------
// Dimensions
CursorHubOD = 1.0*inch; // original Tek CC was hard inch!
CursorTipWidth = (9.0/16.0)*inch;
CursorTipRadius = (1.0/16.0)*inch;
CursorThick = 0.5; // plastic sheet thickness
CutterOD = 3.175; // milling cutter dia
CutterDepth = 2.0; // … depth of cut
CutterLip = 0.5; // … clearance under edge
ScribeOD = 3.0; // diamond scribe shank
StudOC = [1.16*inch,1.16*inch]; // Sherline tooling plate grid
StudClear = 5.0; // … screw clearance
StudWasher = 11.0; // … washer OD
CursorOffset = [-2*StudOC.x,0,0]; // hub center relative to fixture center
// must have even multiples of stud spacing to put studs along centerlines
BasePlateStuds = [6*StudOC.x,2*StudOC.y]; // fixture screws
echo(str("Stud spacing: ",StudOC));
CornerRad = 10.0; // corner radius
BasePlate = [2*StudWasher + BasePlateStuds.x,2*StudWasher + BasePlateStuds.y,5.0];
echo(str("Base Plate: ",BasePlate));
EngravePlate = [5*StudOC.x,1.5*StudOC.y,BasePlate.z];
echo(str("Engrave Plate: ",EngravePlate));
TemplateThick = 6*ThreadThick;
LegendThick = 2*ThreadThick;
Gap = 3.0;
//----------------------
// Import SVG of cursor outline
// Requires our hub OD to match reality
// Hub center at origin
module CursorSVG(t=CursorThick,od=0) {
hr = CursorHubOD/2;
translate([-hr,-hr,0])
linear_extrude(height=t,convexity=3)
offset(r=od/2)
import(file="/mnt/bulkdata/Project Files/Tektronix Circuit Computer/Firmware/TekCC-Cursor-Mark.svg",center=false);
}
//----------------------
// Milling fixture for cursor blanks
module Fixture() {
difference() {
hull() // basic plate shape
for (i=[-1,1], j=[-1,1])
translate([i*(BasePlate.x/2 - CornerRad),j*(BasePlate.y/2 - CornerRad),0])
cylinder(r=CornerRad,h=BasePlate.z,$fn=24);
translate(CursorOffset + [0,0,BasePlate.z - CutterDepth])
difference() {
CursorSVG(CutterDepth + Protrusion,1.5*CutterOD);
CursorSVG(CutterDepth + Protrusion,-CutterLip);
}
translate(CursorOffset + [0,0,BasePlate.z - 2*ThreadThick]) { // alignment pips
for (x=[-20.0,130.0], y=[-30.0,0.0,30.0])
translate([x,y,0])
cylinder(d=4*ThreadWidth,h=1,$fn=6);
for (x=[-30.0,130.0,150.0])
translate([x,0,0])
cylinder(d=4*ThreadWidth,h=1,$fn=6);
}
for (i=[-1,1], j=[-1,1]) // mounting stud holes
translate([i*BasePlateStuds.x/2,j*BasePlateStuds.y/2,-Protrusion])
rotate(180/6)
PolyCyl(StudClear,BasePlate.z + 2*Protrusion,6);
translate(CursorOffset + [0,0,-Protrusion]) // hub clamp hole
rotate(180/6)
PolyCyl(StudClear,BasePlate.z + 2*Protrusion,6);
translate([2*StudOC.x,0,-Protrusion]) // tip clamp hole
rotate(180/6)
PolyCyl(StudClear,BasePlate.z + 2*Protrusion,6);
for (i=[-2:2], j=[-1,1]) // side clamp holes
translate([i*StudOC.x,j*StudOC.y,-Protrusion])
rotate(180/6)
PolyCyl(StudClear,BasePlate.z + 2*Protrusion,6);
}
}
//----------------------
// Show-n-Tell cursor
module Cursor() {
difference() {
CursorSVG(CursorThick,0.0);
translate([0,0,-Protrusion])
rotate(180/6)
PolyCyl(StudClear,TemplateThick + 2*Protrusion,6);
}
}
//----------------------
// Template for rough-cutting blanks
module Rough() {
bb = [40,12,LegendThick];
difference() {
CursorSVG(TemplateThick,1.0);
translate([0,0,-Protrusion])
rotate(180/6)
PolyCyl(StudClear,TemplateThick + 2*Protrusion,6);
difference() {
translate([bb.x/2 + CursorHubOD/2,0,TemplateThick - bb.z/2 + Protrusion])
cube(bb + [0,0,Protrusion],center=true);
translate([bb.x/2 + CursorHubOD/2,0,TemplateThick - bb.z])
linear_extrude(height=bb.z,convexity=10)
text(text="Rough",size=7,spacing=1.00,font="DejaVu Sans:style:Bold",halign="center",valign="center");
}
}
}
//----------------------
// Template for aluminium clamping plate
module Clamp() {
bb = [40,12,LegendThick];
difference() {
CursorSVG(TemplateThick,-1.0);
translate([0,0,-Protrusion])
rotate(180/6)
PolyCyl(StudClear,TemplateThick + 2*Protrusion,6);
difference() {
translate([bb.x/2 + CursorHubOD/2,0,TemplateThick - bb.z/2 + Protrusion])
cube(bb + [0,0,Protrusion],center=true);
translate([bb.x/2 + CursorHubOD/2,0,TemplateThick - bb.z])
linear_extrude(height=bb.z,convexity=10)
text(text="Clamp",size=7,spacing=1.00,font="DejaVu Sans:style:Bold",halign="center",valign="center");
}
}
}
//----------------------
// Engraving clamp
module Engrave() {
difference() {
hull() // clamp outline
for (i=[-1,1], j=[-1,1])
translate([i*(EngravePlate.x/2 - CornerRad),j*(EngravePlate.y/2 - CornerRad),0])
cylinder(r=CornerRad,h=EngravePlate.z,$fn=24);
translate(CursorOffset + [0,0,-Protrusion])
CursorSVG(CursorThick + Protrusion,0.5); // pocket for blank cursor
translate(CursorOffset + [0,0,-Protrusion])
rotate(180/6)
PolyCyl(StudClear,EngravePlate.z + 2*Protrusion,6);
translate([2*StudOC.x,0,-Protrusion])
rotate(180/6)
PolyCyl(StudClear,EngravePlate.z + 2*Protrusion,6);
hull() {
for (i=[-1,1])
translate([i*1.5*StudOC.x,0,-Protrusion])
PolyCyl(2*ScribeOD,EngravePlate.z + 2*Protrusion,8);
}
}
}
//----------------------
// Build it
if (Layout == "Cursor") {
Cursor();
}
if (Layout == "Clamp") {
Clamp();
}
if (Layout == "Rough") {
Rough();
}
if (Layout == "Engrave") {
Engrave();
}
if (Layout == "Show") {
Fixture();
color("Green",0.3)
translate(CursorOffset + [0,0,BasePlate.z + Protrusion])
Cursor();
color("Orange")
translate(CursorOffset + [0,0,BasePlate.z + 10])
Rough();
color("Brown")
translate(CursorOffset + [0,0,BasePlate.z + 20])
Clamp();
color("Gold")
translate(0*CursorOffset + [0,0,BasePlate.z + 40])
Engrave();
}
if (Layout == "Build"){
rotate(90) {
Fixture();
translate([0,-((BasePlate.y + EngravePlate.y)/2 + Gap),EngravePlate.z])
rotate([180,0,0])
Engrave();
translate(CursorOffset + [0,(BasePlate.y + CursorHubOD)/2 + Gap,0])
Rough();
translate(CursorOffset + [0,(BasePlate.y + 3*CursorHubOD)/2 + 2*Gap,0])
Clamp();
}
}
view raw Cursor Fixture.scad hosted with ❤ by GitHub

The original doodle with some notions and dimensions that didn’t survive contact with reality:

Cursor Fixture doodle
Cursor Fixture doodle

I have no idea why the Sherline tooling plate has a 10-32 screw grid on 1.16 inch = 29.46 mm centers, but there they are.

Makergear M2: Initial PrusaSlicer Configuration

After replacing the nozzle and the filament drive body on the M2, I figured I might as well throw all the balls in the air and switch to PrusaSlicer for all my slicing needs. It’s built from the Slic3r project, gaining features used by Prusa’s printers / filaments and a considerably improved UI, with a full-time paid staff working on it:

PrusaSlicer screenshot
PrusaSlicer screenshot

Of course, I immediately turned on Expert mode.

CAUTION: My heavily customized start_gcode will crash your M2, because you haven’t relocated the Z-axis switch, haven’t calibrated Z=0 at the platform surface, and don’t put the XY=0 origin in the center of the platform.

You have been warned: consider this as a serving suggestion, not a finished product.

Because everything I design looks more-or-less like a bracket, I absolutely don’t care about surface finish, and I’m content to use only a few colors of PETG from a single supplier, a single Slic3r configuration has sufficed for nearly everything I print. A few manual tweaks for specific models, perhaps to change the number of perimeters or the infill percentage, handle the remaining cases.

With all that in mind, here’s the current result of File → Export → Export Config as a GitHub Gist:

# generated by PrusaSlicer 2.2.0+linux-x64 on 2021-01-01 at 13:33:03 UTC
avoid_crossing_perimeters = 0
bed_custom_model =
bed_custom_texture =
bed_shape = -100x-125,100x-125,100x125,-100x125
bed_temperature = 90
before_layer_gcode =
between_objects_gcode =
bottom_fill_pattern = hilbertcurve
bottom_solid_layers = 3
bottom_solid_min_thickness = 0
bridge_acceleration = 0
bridge_angle = 0
bridge_fan_speed = 100
bridge_flow_ratio = 1
bridge_speed = 50
brim_width = 0
clip_multipart_objects = 1
colorprint_heights =
complete_objects = 0
cooling = 1
cooling_tube_length = 5
cooling_tube_retraction = 91.5
default_acceleration = 0
default_filament_profile = ""
default_print_profile =
deretract_speed = 0
disable_fan_first_layers = 6
dont_support_bridges = 1
draft_shield = 0
duplicate_distance = 6
elefant_foot_compensation = 0
end_filament_gcode = "; Filament-specific end gcode \n;END gcode for filament\n"
end_gcode = ;-- PrusaSlicer End G-Code for M2 starts --\n; Ed Nisley KE4NZU - 15 November 2013\nG1 Z160 F2000 ; lower bed\nG1 X135 Y100 F30000 ; nozzle to right, bed front\nM104 S0 ; drop extruder temperature\nM140 S0 ; drop bed temperature\nM106 S0 ; bed fan off\nM84 ; disable motors\n;-- PrusaSlicer End G-Code ends --\n\n
ensure_vertical_shell_thickness = 1
external_perimeter_extrusion_width = 0
external_perimeter_speed = 50%
external_perimeters_first = 0
extra_loading_move = -2
extra_perimeters = 1
extruder_clearance_height = 20
extruder_clearance_radius = 20
extruder_colour = ""
extruder_offset = 0x0
extrusion_axis = E
extrusion_multiplier = 0.95
extrusion_width = 0.4
fan_always_on = 0
fan_below_layer_time = 15
filament_colour = #29B2B2
filament_cooling_final_speed = 3.4
filament_cooling_initial_speed = 2.2
filament_cooling_moves = 4
filament_cost = 25
filament_density = 0.95
filament_deretract_speed = nil
filament_diameter = 1.72
filament_load_time = 0
filament_loading_speed = 28
filament_loading_speed_start = 3
filament_max_volumetric_speed = 0
filament_minimal_purge_on_wipe_tower = 15
filament_notes = ""
filament_ramming_parameters = "120 100 6.6 6.8 7.2 7.6 7.9 8.2 8.7 9.4 9.9 10.0| 0.05 6.6 0.45 6.8 0.95 7.8 1.45 8.3 1.95 9.7 2.45 10 2.95 7.6 3.45 7.6 3.95 7.6 4.45 7.6 4.95 7.6"
filament_retract_before_travel = nil
filament_retract_before_wipe = nil
filament_retract_layer_change = nil
filament_retract_length = nil
filament_retract_lift = nil
filament_retract_lift_above = nil
filament_retract_lift_below = nil
filament_retract_restart_extra = nil
filament_retract_speed = nil
filament_settings_id = "M2 Esun PETG"
filament_soluble = 0
filament_toolchange_delay = 0
filament_type = PET
filament_unload_time = 0
filament_unloading_speed = 90
filament_unloading_speed_start = 100
filament_vendor = (Unknown)
filament_wipe = nil
fill_angle = 45
fill_density = 25%
fill_pattern = 3dhoneycomb
first_layer_acceleration = 0
first_layer_bed_temperature = 90
first_layer_extrusion_width = 0
first_layer_height = 0.25
first_layer_speed = 15
first_layer_temperature = 250
gap_fill_speed = 25
gcode_comments = 0
gcode_flavor = marlin
gcode_label_objects = 0
high_current_on_filament_swap = 0
host_type = octoprint
infill_acceleration = 0
infill_every_layers = 1
infill_extruder = 1
infill_extrusion_width = 0
infill_first = 1
infill_only_where_needed = 0
infill_overlap = 15%
infill_speed = 60
interface_shells = 0
layer_gcode =
layer_height = 0.25
machine_max_acceleration_e = 10000,5000
machine_max_acceleration_extruding = 10000,1250
machine_max_acceleration_retracting = 10000,1250
machine_max_acceleration_x = 2500,1000
machine_max_acceleration_y = 2500,1000
machine_max_acceleration_z = 2500,200
machine_max_feedrate_e = 10000,5000
machine_max_feedrate_x = 450,200
machine_max_feedrate_y = 450,200
machine_max_feedrate_z = 100,30
machine_max_jerk_e = 100,50
machine_max_jerk_x = 25,10
machine_max_jerk_y = 25,10
machine_max_jerk_z = 10,5
machine_min_extruding_rate = 0,0
machine_min_travel_rate = 0,0
max_fan_speed = 100
max_layer_height = 0
max_print_height = 200
max_print_speed = 80
max_volumetric_speed = 0
min_fan_speed = 100
min_layer_height = 0.1
min_print_speed = 10
min_skirt_length = 25
notes =
nozzle_diameter = 0.35
only_retract_when_crossing_perimeters = 1
ooze_prevention = 0
output_filename_format = [input_filename_base].gcode
overhangs = 1
parking_pos_retraction = 92
perimeter_acceleration = 0
perimeter_extruder = 1
perimeter_extrusion_width = 0
perimeter_speed = 50
perimeters = 3
post_process =
print_host =
print_settings_id = M2 Default
printer_model =
printer_notes =
printer_settings_id = M2 Default
printer_technology = FFF
printer_variant =
printer_vendor =
printhost_apikey =
printhost_cafile =
raft_layers = 0
remaining_times = 0
resolution = 0.01
retract_before_travel = 3
retract_before_wipe = 0%
retract_layer_change = 0
retract_length = 1
retract_length_toolchange = 10
retract_lift = 0
retract_lift_above = 0
retract_lift_below = 0
retract_restart_extra = 0
retract_restart_extra_toolchange = 0
retract_speed = 60
seam_position = nearest
serial_port =
serial_speed = 250000
silent_mode = 1
single_extruder_multi_material = 0
single_extruder_multi_material_priming = 1
skirt_distance = 3
skirt_height = 1
skirts = 3
slice_closing_radius = 0.049
slowdown_below_layer_time = 5
small_perimeter_speed = 25%
solid_infill_below_area = 70
solid_infill_every_layers = 0
solid_infill_extruder = 1
solid_infill_extrusion_width = 0
solid_infill_speed = 75%
spiral_vase = 0
standby_temperature_delta = -5
start_filament_gcode = "; Filament gcode\n"
start_gcode = ;-- PrusaSlicer Start G-Code for M2 starts --\n; Ed Nisley KE4NZU\n; Makergear V4 hot end\n; Origin at platform center, set by MANUAL_X_HOME_POS compiled constants\n; Z-min switch at platform, must move nozzle to X=135 to clear\nG90 ; absolute coordinates\nG21 ; millimeters\nM83 ; relative extrusion distance\nM104 S[first_layer_temperature] ; start extruder heating\nM140 S[first_layer_bed_temperature] ; start bed heating\nM17 ; enable steppers\nG4 P500 ; ... wait for power up\nG92 Z0 ; set Z to zero, wherever it might be now\nG0 Z10 F1000 ; move platform downward to clear nozzle; may crash at bottom\nG28 Y ; home Y to clear plate, offset from compiled constant\nG28 X ; home X, offset from M206 X, offset from compiled constant\nG0 X135 Y0 F15000 ; move off platform to right side, center Y\nG28 Z ; home Z to platform switch, offset from M206 Z measured\nG0 Z2.0 F1000 ; get air under switch\nG0 Y-126 F10000 ; set up for priming, zig around corner\nG0 X0 ; center X\nG0 Y-124.5 ; just over platform edge\nG0 Z0 F500 ; exactly at platform\nM190 S[first_layer_bed_temperature] ; wait for bed to finish heating\nM109 S[first_layer_temperature] ; set extruder temperature and wait\nG1 E20 F300 ; prime to get pressure, generate blob on edge\nG0 Y-123 F5000 ; shear off blob\nG0 X15 F15000 ; jerk away from blob, move over surface\nG4 P500 ; pause to attach\nG1 X45 F500 ; slowly smear snot to clear nozzle\nG1 Z1.0 F2000 ; clear bed for travel\n;-- PrusaSlicer Start G-Code ends --\n
support_material = 0
support_material_angle = 0
support_material_auto = 1
support_material_buildplate_only = 0
support_material_contact_distance = 0.2
support_material_enforce_layers = 0
support_material_extruder = 1
support_material_extrusion_width = 0.31
support_material_interface_contact_loops = 0
support_material_interface_extruder = 1
support_material_interface_layers = 3
support_material_interface_spacing = 0
support_material_interface_speed = 100%
support_material_pattern = rectilinear
support_material_spacing = 2.5
support_material_speed = 60
support_material_synchronize_layers = 0
support_material_threshold = 0
support_material_with_sheath = 1
support_material_xy_spacing = 50%
temperature = 250
thin_walls = 1
threads = 4
thumbnails =
toolchange_gcode =
top_fill_pattern = hilbertcurve
top_infill_extrusion_width = 0
top_solid_infill_speed = 50%
top_solid_layers = 3
top_solid_min_thickness = 0
travel_speed = 300
use_firmware_retraction = 0
use_relative_e_distances = 0
use_volumetric_e = 0
variable_layer_height = 1
wipe = 0
wipe_into_infill = 0
wipe_into_objects = 0
wipe_tower = 0
wipe_tower_bridging = 10
wipe_tower_no_sparse_layers = 0
wipe_tower_rotation_angle = 0
wipe_tower_width = 60
wipe_tower_x = 180
wipe_tower_y = 140
wiping_volumes_extruders = 70,70
wiping_volumes_matrix = 0
xy_size_compensation = 0
z_offset = 0

MTD Snowthrower: Replacement Throttle Knob

The throttle knob on our MTD snowthrower (a.k.a. snowblower) cracked apart around its metal shaft when I pulled it upward. A temporary fix involving duct tape and cable ties sufficed to start the engine, although the usual intense vibration shook the knob loose somewhere along the driveway during the next hour.

Update: Found it!

Although I have no photographic evidence, I did make a few quick measurements:

Throttle Knob Dimension Doodles
Throttle Knob Dimension Doodles

It fits an MTD model E6A4E, but I suspect nearly all their engines have identical throttle shafts:

Snowthrower Throttle Knob - stem end - solid model
Snowthrower Throttle Knob – stem end – solid model

The only practical way to build the thing has it standing on the shaft end, surrounded by a brim to improve adhesion, so I added (actually, subtracted) a pair of holes for music-wire reinforcements:

Snowthrower throttle knob - reinforcing wires
Snowthrower throttle knob – reinforcing wires

It definitely has a stylin’ look, next to the original choke control knob:

Snowthrower throttle knob - installed
Snowthrower throttle knob – installed

I omitted the finger grip grooves for obvious reasons.

The slot-and-hole came out slightly smaller than the metal shaft and, rather than wait for epoxy to cure, I deployed a 230 W soldering gun (not a piddly temperature-controlled iron suitable for electronics) on the shaft and melted it into the knob.

More snow may arrive this week and I printed another knob just in case …

The OpenSCAD source code as a GitHub Gist:

// MTD Snowthrower Throttle Knob
// Ed Nisley KE4ZNU 2020-12-18
/* [Options] */
Layout = "Show"; // [Build, Show]
// Extrusion parameters
/* [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
Throttle = [17.0,1.85,6.5]; // blade insertion, thickness, width
PaddleSize = [25,30,9];
PaddleRound = 4.0;
PaddleThick = 8.5;
StemDia = 13.0;
StemLength = 20.0;
PinDia = 1.6;
PinLength = PaddleSize.x + StemLength/2;
echo(str("Pin: ",PinLength," x ",PinDia," mm"));
//----------------------
// 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,
$fn=Sides);
}
//----------------------
// Pieces
module Paddle() {
difference() {
hull() {
translate([PaddleSize.x/2,0,0]) {
for (i=[-1,1], j=[-1,1])
translate([i*(PaddleSize.x - PaddleRound)/2,j*(PaddleSize.y - PaddleRound)/2,0])
sphere(d=PaddleRound,$fn=12);
rotate([0,90,0]) rotate(180/12)
cylinder(d=PaddleThick,h=PaddleSize.x,,center=true,$fn=12);
}
translate([-StemLength,0,0])
rotate([0,90,0]) rotate(180/12)
cylinder(d=StemDia,h=Throttle.x,center=false,$fn=12);
}
translate([-StemLength,0,0])
cube([2*Throttle.x,Throttle.y,Throttle.z],center=true);
translate([-(StemLength + Protrusion),0,0])
rotate([0,90,0]) rotate(0*180/6)
PolyCyl(2*Throttle.y,Throttle.x,6);
for (j=[-1,1])
translate([-StemLength/2,j*PaddleSize.y/6,0])
rotate([0,90,0]) rotate(180/4)
PolyCyl(PinDia,PinLength,4);
}
}
//----------------------
// Build it
if (Layout == "Show")
Paddle();
if (Layout == "Build") {
translate([0,0,StemLength])
rotate([0,-90,0])
Paddle();
}