The Smell of Molten Projects in the Morning

Ed Nisley's Blog: Shop notes, electronics, firmware, machinery, 3D printing, laser cuttery, and curiosities. Contents: 100% human thinking, 0% AI slop.

Tag: M2

Using and tweaking a Makergear M2 3D printer

  • Makergear M2 V4 Nozzle: Silicone Refresh

    Makergear M2 V4 Nozzle: Silicone Refresh

    After a year and a half, the silicone coat I’d applied to the M2’s nozzle had pretty much worn away, so I peeled off the remnants, buffed up the brass, and mushed on another coat:

    Makergear M2 V4 Nozzle - High-temp silicone coat
    Makergear M2 V4 Nozzle – High-temp silicone coat

    The coverage isn’t even, particularly in the direction I can neither see nor reach with the hot end still in the printer, but it’s way less hassle than recalibrating the Z=0 position. The very thin layer over the brass around the nozzle will vanish immediately on the skirt surrounding the first part.

    I should definitely recoat the nozzle more often, because PETG doesn’t stick to silicone nearly as well as it does to brass: a nice new coat makes the PETG burned-snot problem Just Go Away.

  • Bathroom Door Retainer: Bigger and Stronger

    Bathroom Door Retainer: Bigger and Stronger

    After three years, the retainer holding the front bathroom door open against winds blowing through the house on stormy days finally fractured, right at the top of the towel rack where you’d expect it:

    Bathroom Door Retainer - fractured
    Bathroom Door Retainer – fractured

    I was all set to add reinforcing pins and whatnot, then came to my senses and just made the whole thing a few millimeters larger:

    Bathroom Door Retainer - stronger
    Bathroom Door Retainer – stronger

    Customer feedback indicates white blends better with the background.

    I made a few minor tweaks to the original design, including slightly larger bumps to hold it against the towel bar that, regrettably, put corresponding gouges into the bar. Who knew they used such soft plastic back in the day?

    The OpenSCAD source code as a GitHub Gist:

    // Bathroom Door Retainer
    // Ed Nisley KE4ZNU – May 2017
    // 2020-07 beef up, particularly at top of bar
    Layout = "Show"; // [Show, Build]
    //——-
    //- Extrusion parameters must match reality!
    /* [Hidden] */
    ThreadThick = 0.20;
    ThreadWidth = 0.40;
    HoleWindage = 0.2;
    Protrusion = 0.1; // make holes end cleanly
    function IntegerMultiple(Size,Unit) = Unit * ceil(Size / Unit);
    //——-
    // Dimensions
    /* [Dimensions] */
    TowelBarSide = 20.5; // towel bar across flat side
    TowelBarAngle = 45; // rotation of top flat from horizontal
    BumpOD = 2.0; // retaining ball
    DoorOffset = 14.0; // from towel bar to door
    DoorThick = 37.0;
    WallThick = 8.0; // minimum wall thickness
    PlateThick = 4.0; // … slab
    RetainerDepth = 15.0; // thickness of retaining notch
    NumSides = 6*4;
    CornerRad = WallThick;
    BarClipOD = TowelBarSide*sqrt(2) + 2*WallThick;
    BarClipRad = BarClipOD/2;
    OAH = RetainerDepth + PlateThick;
    module LatchPlan() {
    union() {
    linear_extrude(height=OAH,convexity=4)
    difference() {
    union() {
    circle(d=BarClipOD,$fn=NumSides);
    hull()
    for (i=[0,1], j=[0,1])
    translate([i*(BarClipRad + DoorOffset + DoorThick + WallThick – CornerRad),j*(BarClipRad – CornerRad)])
    circle(r=CornerRad,$fn=4*4);
    }
    rotate(TowelBarAngle) // towel bar shape
    square(size=TowelBarSide,center=true);
    translate([0,-TowelBarSide/sqrt(2)]) // make access slot
    rotate(-TowelBarAngle)
    square(size=[2*TowelBarSide,TowelBarSide],center=false);
    }
    for (a=[0:180:360])
    rotate(a + TowelBarAngle)
    translate([TowelBarSide/2,0,OAH/2])
    rotate([90,0,45])
    sphere(d=BumpOD,$fn=4*3);
    }
    }
    module Latch() {
    difference() {
    LatchPlan();
    translate([BarClipRad + DoorOffset,-BarClipRad/2,-Protrusion])
    cube([DoorThick,BarClipOD,RetainerDepth + Protrusion],center=false);
    }
    }
    //——-
    // Build it!
    if (Layout == "Show") {
    Latch();
    }
    if (Layout == "Build") {
    translate([0,0,OAH])
    rotate([180,0,0])
    Latch();
    }

    Done!

  • Makergear M2 Extruder Motor Debugging

    Makergear M2 Extruder Motor Debugging

    While sorting out an extrusion problem on the Makergear forum, I suggested marking the motor shaft and the filament drive shaft to see if the motor pinion inside the gearbox had worn out: if the motor turns and the filament gear doesn’t, then it’s dead inside.

    For future reference, you mark the motor shaft thusly:

    Makergear M2 - filament drive motor - rear shaft
    Makergear M2 – filament drive motor – rear shaft

    Two marks on the filament drive gear tell you if the shaft is turning and if the gear is slipping on the shaft:

    Makergear M2 - filament drive gear
    Makergear M2 – filament drive gear

    A closeup of an earlier, much coarser, drive gear:

    M2 - Filament Drive Gear
    M2 – Filament Drive Gear

    It all worked out well in the end!

  • Garden Soaker Hose Repairs In Use

    Garden Soaker Hose Repairs In Use

    Just for completeness, here’s what the various soaker hose clamps look like in the garden, as solid models only let you visualize the ideal situation:

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

    This one prevents a puddle in the path to the right:

    Soaker hose repairs in situ - clamp
    Soaker hose repairs in situ – clamp

    Bending the hoses around the end of a bed puts them on edge, with this clamp suppressing a shin-soaking spray to the left:

    Soaker hose repairs in situ - end-on clamp
    Soaker hose repairs in situ – end-on clamp

    The clamp at the connector closes a leak around the crimped brass fitting, with the other two preventing gouges from direct sprays into the path along the bottom of the picture:

    Soaker hose repairs in situ - clamps and connector fix
    Soaker hose repairs in situ – clamps and connector fix

    All in all, a definite UI improvement!

    As far as I can tell, we have the only soaker hose repairs & spritz stoppers in existence. Hooray for 3D printing!

  • Solid Modeling: Support Puzzle

    Solid Modeling: Support Puzzle

    I’ve been putting this type of support structure inside screw holes & suchlike for years:

    Browning Hi-Power Magazine Block - solid model - Generic 1 - support detail
    Browning Hi-Power Magazine Block – solid model – Generic 1 – support detail

    It’s basically a group of small rectangles rotated around the hole’s axis and about one thread thickness shorter than the overhanging interior.

    I’ve found that incorporating exactly the right support structure eliminates Slic3r’s weird growths, eases removal, and generally works better all around.

    So doing this for the baseplate of the Glass Tile frame came naturally:

    Glass Tile Frame - octagonal support
    Glass Tile Frame – octagonal support

    This OpenSCAD snippet plunks one of those asterisks in each of four screw holes:

      if (Support)
        color("Yellow")
          for (i=[-1,1], j=[-1,1])
            translate([i*InsertOC.x/2,j*InsertOC.y/2,0])
              for (a=[0:45:135])
                  rotate(a)
                    translate([0,0,(Screw[LENGTH] - ThreadThick)/2])
                      cube([Screw[OD] - 2*ThreadWidth,2*ThreadWidth,Screw[LENGTH] - ThreadThick],center=true);

    The “cubes” overlap in the middle, with no completely coincident faces or common edges, so it’s 2-manifold. Slic3r, however, produces a weird time estimate whenever the model includes those structures:

    Slic3r - NaN time estimate
    Slic3r – NaN time estimate

    NaN stands for Not A Number and means something horrible has happened in the G-Code generation. Fortunately, the G-Code worked perfectly and produced the desired result, but I’m always uneasy when Something Seems Wrong.

    Messing around with the code produced a slightly different support structure:

    Glass Tile Frame - quad support
    Glass Tile Frame – quad support

    The one thread thick square on the bottom helps glue the structure to the platform and four ribs work just as well as eight in the octagonal hole:

      Fin = [Screw[OD]/2 - 1.5*ThreadWidth,2*ThreadWidth,ScrewRecess - ThreadThick];
      if (Inserts && SupportInserts)
        color("Yellow")
          for (i=[-1,1], j=[-1,1])
            translate([i*InsertOC.x/2,j*InsertOC.y/2,0]) {
              rotate(180/8)
                cylinder(d=6*ThreadWidth,h=ThreadThick,$fn=8);
              for (a=[0:90:360])
                  rotate(a)
                    translate([Fin.x/2 + ThreadWidth/2,0,(ScrewRecess - ThreadThick)/2])
                      cube(Fin,center=true);
            }

    Which changed the NaN time estimates into actual numbers.

    One key difference may be the small hole in the middle. The four ribs (not two!) now overlap by one thread width around the hole, so they’re not quite coincident and Slic3r produces a tidy model:

    Glass Tile Frame - quad support - Slic3r
    Glass Tile Frame – quad support – Slic3r

    The hole eliminates a smear of infill from the center, which may have something to do with the improvement.

    In any event, I have an improved copypasta recipe for the next screw holes in need of support, even if I don’t understand why it’s better.

  • Glass Tiles: Matrix for SK6812 PCBs

    Glass Tiles: Matrix for SK6812 PCBs

    Tweaking the glass tile frame for press-fit SK6812 PCBs in the bottom of the array cells:

    Glass Tile Frame - cell array - openscad
    Glass Tile Frame – cell array – openscad

    Which looks like this with the LEDs and brass inserts installed:

    Glass Tile - 2x2 array - interior
    Glass Tile – 2×2 array – interior

    The base holds an Arduino Nano with room for wiring under the cell array:

    Glass Tile Frame - base - openscad
    Glass Tile Frame – base – openscad

    Which looks like this after it’s all wired up:

    Glass Tile - 2x2 array - wiring
    Glass Tile – 2×2 array – wiring

    The weird colors showing through the inserts are from the LEDs. The red thing in the upper left is a silicone insulation snippet. Yes, that’s hot-melt glue holding the Arduino Nano in place and preventing the PCBs from getting frisky.

    Soak a handful of glass tiles overnight in paint stripper:

    Glass Tiles - paint stripper soak
    Glass Tiles – paint stripper soak

    Whereupon the adhesive slides right off with the gentle application of a razor scraper. Rinse carefully, dry thoroughly, and snap into place.

    Tighten the four M3 SHCS and it’s all good:

    Glass Tile - 2x2 array - operating
    Glass Tile – 2×2 array – operating

    So far, I’ve had two people tell me they don’t know what it is, but they want one:

    Glass Tile - various versions
    Glass Tile – various versions

    The OpenSCAD Customizer lets you set the array size:

    Glass Tile Frame - 3x3 - press-fit SK6812 LEDs
    Glass Tile Frame – 3×3 – press-fit SK6812 LEDs

    However, just because you can do something doesn’t mean you should:

    Glass Tile Frame - 6x6 cell array - openscad
    Glass Tile Frame – 6×6 cell array – openscad

    Something like this might be interesting:

    Glass Tile Frame - 2x6 cell array - openscad
    Glass Tile Frame – 2×6 cell array – openscad

    In round numbers, printing the frame takes about an hour per cell, so a 2×2 array takes three hours and 3×3 array runs around seven hours. A 6×6 frame is just not happening.

    The OpenSCAD source code as a GitHub Gist:

    // Illuminated Tile Grid
    // Ed Nisley – KE4ZNU
    // 2020-05
    /* [Configuration] */
    Layout = "Build"; // [Cell,CellArray,MCU,Base,Show,Build]
    Shape = "Square"; // [Square, Pyramid, Cone]
    Cells = [2,2];
    CellDepth = 15.0;
    Inserts = true;
    SupportInserts = true;
    /* [Hidden] */
    ThreadThick = 0.25;
    ThreadWidth = 0.40;
    HoleWindage = 0.2;
    function IntegerMultiple(Size,Unit) = Unit * ceil(Size / Unit);
    Protrusion = 0.1; // make holes end cleanly
    ID = 0;
    OD = 1;
    LENGTH = 2;
    Tile = [25.0 + 0.1,25.0 + 0.1,4.0];
    WallThick = 4*ThreadWidth;
    FloorThick = 3.0;
    Flange = [2*ThreadWidth,2*ThreadWidth,0]; // ridge supporting tile
    Separator = [3*ThreadWidth,3*ThreadWidth,Tile.z – 1]; // between tiles
    Screw = [3.0,6.0,3.5]; // M3 SHCS, OD=head, LENGTH=head
    Insert = [3.0,4.2,8.0]; // threaded brass insert
    ScrewRecess = Screw[LENGTH] + 4*ThreadThick;
    LEDPCB = [9.6,9.6,2.9]; // round SK6812, squared-off sides
    LED = [5.0 + 2*HoleWindage,5.0 + 2*HoleWindage,1.3];
    LEDOffset = [0.0,0.0,0.0]; // if offset from PCB center
    CellOAL = [Tile.x,Tile.y,0] + Separator + [0,0,CellDepth] + [0,0,FloorThick];
    ArrayOAL = [Cells.x*CellOAL.x,Cells.y*CellOAL.y,CellOAL.z]; // just the LED cells
    BlockOAL = ArrayOAL + [2*WallThick,2*WallThick,0]; // LED cells + exterior wall
    echo(str("Block OAL: ",BlockOAL));
    InsertOC = ArrayOAL – [Insert[OD],Insert[OD],0] – [WallThick,WallThick,0];
    echo(str("Insert OC: ",InsertOC));
    TapeThick = 1.0;
    Arduino = [44.0,18.0,8.0 + TapeThick]; // Arduino Nano to top of USB Mini-B plug
    USBPlug = [15.0,11.0,9.0]; // USB Mini-B plug insulator
    USBOffset = [0,0,5.0]; // offset from PCB base
    WiringSpace = 3.5;
    WiringBay = [(Cells.x – 1)*CellOAL.x + LEDPCB.x,(Cells.y – 1)*CellOAL.y + LEDPCB.x,WiringSpace];
    PlateOAL = [BlockOAL.x,BlockOAL.y,FloorThick + Arduino.z + WiringSpace]; // allow wiring above Arduino
    echo(str("Base Plate: ",PlateOAL));
    echo(str("Screw length: ",(PlateOAL.z – ScrewRecess) + Insert.z/2," to ",(PlateOAL.z – ScrewRecess) + Insert.z));
    LegendRecess = 1*ThreadThick;
    //————————
    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,$fn=Sides);
    }
    //———————–
    // Base and optics in single tile
    module LEDCone() {
    hull() {
    translate([0,0,CellDepth + Tile.z/2])
    cube(Tile – 2*[Flange.x,Flange.y,0],center=true);
    if (Shape == "Square") {
    translate([0,0,LEDPCB.z/2])
    cube([Tile.x,Tile.y,LEDPCB.z] – 2*[Flange.x,Flange.y,0],center=true);
    }
    else if (Shape == "Pyramid") {
    translate([0,0,LEDPCB.z/2])
    cube(LEDPCB,center=true);
    }
    else if (Shape == "Cone") {
    translate([0,0,LEDPCB.z/2])
    cylinder(d=1.0*LEDPCB.x,h=LED.z,center=true);
    }
    else {
    echo(str("Whoopsie! Invalid Shape: ",Shape));
    cube(5);
    }
    }
    }
    // One complete LED cell
    module LEDCell() {
    difference() {
    translate([0,0,CellOAL.z/2])
    cube(CellOAL + [Protrusion,Protrusion,0],center=true); // force overlapping adjacent sides!
    translate([0,0,CellOAL.z – Separator.z + Tile.z/2])
    cube(Tile,center=true);
    translate([0,0,LEDPCB.z])
    LEDCone();
    // cube([LED.x,LED.y,CellOAL.z],center=true);
    translate(-LEDOffset + [0,0,-CellOAL.z/2])
    rotate(180/8)
    PolyCyl(LEDPCB.x,CellOAL.z,8);
    }
    }
    // The whole array of cells
    module CellArray() {
    difference() {
    union() {
    translate([CellOAL.x/2 – Cells.x*CellOAL.x/2,CellOAL.y/2 – Cells.y*CellOAL.y/2,0])
    for (i=[0:Cells.x – 1], j=[0:Cells.y – 1])
    translate([i*CellOAL.x,j*CellOAL.y,0])
    LEDCell();
    if (Inserts) // bosses
    for (i=[-1,1], j=[-1,1])
    translate([i*InsertOC.x/2,j*InsertOC.y/2,0])
    rotate(180/8)
    cylinder(d=Insert[OD] + 2*WallThick,h=Insert[LENGTH],$fn=8);
    }
    if (Inserts) // holes
    for (i=[-1,1], j=[-1,1])
    translate([i*InsertOC.x/2,j*InsertOC.y/2,-Protrusion])
    rotate(180/8)
    PolyCyl(Insert[OD],Insert[LENGTH] + FloorThick + Protrusion,8);
    }
    difference() {
    translate([0,0,CellOAL.z/2])
    cube(BlockOAL,center=true);
    translate([0,0,CellOAL.z])
    cube(ArrayOAL + [0,0,2*CellOAL.z],center=true);
    }
    }
    // Arduino bounding box
    // Origin at center bottom of PCB
    module Controller() {
    union() {
    translate([0,0,Arduino.z/2])
    cube(Arduino,center=true);
    translate([Arduino.x/2 – Protrusion,-USBPlug.y/2,USBOffset.z + TapeThick – USBPlug.z/2])
    cube(USBPlug + [Protrusion,0,0],center=false);
    }
    }
    // Baseplate
    module BasePlate() {
    difference() {
    translate([0,0,PlateOAL.z/2])
    cube(PlateOAL,center=true);
    translate([PlateOAL.x/2 – Arduino.x/2 – 2*WallThick,0,FloorThick])
    Controller();
    translate([PlateOAL.x/2 – Arduino.x/2 – 2*WallThick,0,FloorThick + PlateOAL.z/2])
    cube([Arduino.x – 2*2.0,WiringBay.y,PlateOAL.z],center=true); // cutouts beside MCU
    translate([0,0,PlateOAL.z – WiringBay.z + PlateOAL.z/2 – Protrusion])
    cube([PlateOAL.x – 2*WallThick,WiringBay.y,PlateOAL.z],center=true); // cutout above MCU
    translate([0,0,PlateOAL.z – WiringBay.z + PlateOAL.z/2 – Protrusion])
    cube([WiringBay.x,PlateOAL.y – 2*WallThick,PlateOAL.z],center=true); // cutout above MCU
    if (Inserts)
    for (i=[-1,1], j=[-1,1])
    translate([i*InsertOC.x/2,j*InsertOC.y/2,-Protrusion])
    rotate(180/8) {
    PolyCyl(Screw[ID],2*PlateOAL.z,8);
    PolyCyl(Screw[OD],ScrewRecess + Protrusion,8);
    }
    cube([45,17.0,2*LegendRecess],center=true);
    }
    linear_extrude(height=2*LegendRecess) {
    translate([0,1])
    rotate(-0*90) mirror([1,0,0])
    text(text="Ed Nisley",size=6,font="Arial:style:Bold",halign="center");
    translate([0,-6.5])
    rotate(-0*90) mirror([1,0,0])
    text(text="softsolder.com",size=4.5,font="Arial:style:Bold",halign="center");
    }
    Fin = [Screw[OD]/2 – 1.5*ThreadWidth,2*ThreadWidth,ScrewRecess – ThreadThick];
    if (Inserts && SupportInserts)
    color("Yellow")
    for (i=[-1,1], j=[-1,1])
    translate([i*InsertOC.x/2,j*InsertOC.y/2,0]) {
    rotate(180/8)
    cylinder(d=6*ThreadWidth,h=ThreadThick,$fn=8);
    for (a=[0:90:360])
    rotate(a)
    translate([Fin.x/2 + ThreadWidth/2,0,(ScrewRecess – ThreadThick)/2])
    cube(Fin,center=true);
    }
    }
    //———————–
    // Build things
    if (Layout == "Cell")
    LEDCell();
    else if (Layout == "CellArray")
    CellArray();
    else if (Layout == "MCU")
    Controller();
    else if (Layout == "Base")
    BasePlate();
    else if (Layout == "Show") {
    translate([0,0,3*PlateOAL.z])
    CellArray();
    BasePlate();
    translate([PlateOAL.x/2 – Arduino.x/2 – 2*WallThick,0,FloorThick])
    color("Orange",0.3)
    Controller();
    }
    else if (Layout == "Build") union() {
    translate([0,0.6*BlockOAL.y,0])
    CellArray();
    translate([0,-0.6*BlockOAL.x,0])
    rotate(90)
    BasePlate();
    }

  • Garden Hose Valve Wrench: Reinforced

    Garden Hose Valve Wrench: Reinforced

    After five gardening seasons, my simple 3D printed wrench broke:

    Hose Valve Knob - fractured
    Hose Valve Knob – fractured

    Although Jason’s comment suggesting carbon-fiber reinforcing rods didn’t prompt me to lay in a stock, ordinary music wire should serve the same purpose:

    Hose Valve Knob - cut pins
    Hose Valve Knob – cut pins

    The pins are 1.6 mm diameter and 20 mm long, chopped off with hardened diagonal cutters. Next time, I must (remember to) grind the ends flat.

    The solid model needs holes in appropriate spots:

    Hose Valve Knob - Reinforced - Slic3r
    Hose Valve Knob – Reinforced – Slic3r

    Yes, I’m going to put round pins in square holes, without drilling the holes to the proper diameter: no epoxy, no adhesive, just 20 mm of pure friction.

    The drill press aligns the pins:

    Hose Valve Knob - pin ready
    Hose Valve Knob – pin ready

    And rams them about halfway down:

    Hose Valve Knob - pin midway
    Hose Valve Knob – pin midway

    Close the chuck jaws and shove them flush with the surface:

    Hose Valve Knob - pins installed
    Hose Valve Knob – pins installed

    You can see the pins and their solid plastic shells through the wrench stem:

    Hose Valve Knob - assembled
    Hose Valve Knob – assembled

    Early testing shows the reinforced wrench works just as well as the previous version, even on some new valves sporting different handles, with an equally sloppy fit for all. No surprise: I just poked holes in the existing model and left all the other dimensions alone.

    The OpenSCAD source code as a GitHub Gist:

    // Hose connector knob
    // Ed Nisley KE4ZNU – June 2015
    // 2020-05 add reinforcing rods
    Layout = "Build"; // [Knob, Stem, Show, Build]
    RodHoles = true;
    //- Extrusion parameters – must match reality!
    /* [Hidden] */
    ThreadThick = 0.25;
    ThreadWidth = 0.40;
    function IntegerMultiple(Size,Unit) = Unit * ceil(Size / Unit);
    Protrusion = 0.1;
    HoleWindage = 0.2;
    //——
    // Dimensions
    /* [Dimensions] */
    RodOD = 1.6;
    RodAngle = 35;
    /* [Hidden] */
    StemOD = 30.0; // max OD for valve-to-valve clearance
    BossOD = 16.0; // single-ended handle boss
    SlotWidth = 13.0;
    SlotHeight = 10.0;
    StemInset = 10.0;
    StemLength = StemInset + SlotHeight + 25.0;
    StemSides = 2*4;
    Align = 0*180/StemSides; // 1* produces thinner jaw ends
    KnobOD1 = 70; // maximum dia without chamfer
    KnobOD2 = 60; // top dia
    KnobSides = 4*4;
    DomeHeight = 12; // dome shape above lobes
    KnobHeight = DomeHeight + 2*SlotHeight;
    DomeOD = KnobOD2 + (KnobOD1 – KnobOD2)*(DomeHeight/KnobHeight);
    DomeArcRad = (pow(KnobHeight,2) + pow(DomeOD,2)/4) / (2*DomeHeight);
    RodBCD = (StemOD + BossOD)/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,$fn=Sides);
    }
    //– Stem for valve handles
    module Stem() {
    difference() {
    rotate(Align)
    cylinder(d=StemOD,h=StemLength,$fn=StemSides);
    translate([0,0,SlotHeight/2 – Protrusion/2])
    cube([2*StemOD,SlotWidth,(SlotHeight + Protrusion)],center=true);
    translate([0,0,-Protrusion])
    cylinder(d=BossOD,h=SlotHeight,$fn=2*StemSides);
    if (RodHoles)
    for (i=[-1:1])
    rotate(i*RodAngle + 90)
    for (j=[-1,1])
    translate([j*RodBCD/2,0,-Protrusion])
    rotate(180/4)
    PolyCyl(RodOD,2*SlotHeight,4);
    }
    }
    //– Hand-friendly knob
    module KnobCap() {
    difference() {
    scale([1.0,0.75,1.0])
    rotate(180/KnobSides)
    intersection() {
    translate([0,0,(KnobHeight-DomeArcRad)])
    sphere(r=DomeArcRad,$fa=180/KnobSides);
    cylinder(r1=KnobOD1/2,r2=KnobOD2/2,h=KnobHeight,$fn=KnobSides);
    cylinder(r1=KnobOD2/2,r2=KnobOD1/2,h=KnobHeight,$fn=KnobSides);
    }
    translate([0,0,-Protrusion])
    rotate(Align)
    cylinder(d=(StemOD + 2*ThreadWidth),h=(StemInset + Protrusion),$fn=StemSides);
    }
    }
    //- Build it
    if (Layout == "Knob")
    KnobCap();
    if (Layout == "Stem")
    Stem();
    if (Layout == "Build") {
    translate([-KnobOD1/2,0,0])
    KnobCap();
    translate([StemOD/2,0,StemLength])
    rotate([180,0,0])
    Stem();
    }
    if (Layout == "Show") {
    translate([0,0,0])
    Stem();
    translate([0,0,StemLength – StemInset])
    KnobCap();
    }