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

  • Clover MCI-900 Mini Iron Holder

    Mary flattens seam allowances and prepares appliqué pieces with a Clover MCI-900 Mini Iron. The stand resembles the wire gadgets that came with soldering irons, back in the day:

    Clover MCI-900 Mini Iron - Clover holder
    Clover MCI-900 Mini Iron – Clover holder

    That stand may be suitable on a workbench, but it’s perilously unstable on an ironing board. After fiddling around for a while and becoming increasingly frustrated with it, she asked for a secure holder that wouldn’t fall over and perhaps had a heat shield around the hot end.

    I ran off a quick prototype to verify my measurements and provide a basis for further discussion:

    Clover MCI-900 Mini Iron - Level holder
    Clover MCI-900 Mini Iron – Level holder

    I proposed screwing that holder to a rectangle of leftover countertop extending under the hot end, with a U-shaped heat shield extending upward to keep fingers and fabric away from the blade. She decided the countertop might be entirely too heavy and the heat shield might be too confining, so she suggested just angling the iron upward and adding a flat platform to stabilize it.

    Her wish being my command:

    Clover MCI-900 Mini Iron - Angled holder
    Clover MCI-900 Mini Iron – Angled holder

    I’m still not convinced that having the hot end up in the air is a Good Thing, but she thinks it’s worth trying as-is. A pair of 10-32 screw holes under each end will let it mount to a base board, should that becomes necessary.

    I’ll stick a foam sheet under the platform so it doesn’t slide around. The cord normally dangles downward off the side of the ironing board or work table, so the iron won’t get up and walk away, but it might pull the whole affair toward the edge.

    Because OpenSCAD now includes a text() function, engraving her name in the platform turned out to be no big deal:

    Clover Mini Iron Holder - model
    Clover Mini Iron Holder – model

    I should fill the letters with JB Weld epoxy darkened with laser printer toner (who knew?) to make them stand out. They’re more conspicuous in person than in the picture, so maybe it doesn’t matter.

    The slots holding the iron have a semicircular bottom and straight-wall sides, created by extruding hulled 2D shapes, arranging them along the iron’s central axis, and tilting the “iron” at the appropriate angle:

    Clover Mini Iron Holder - solid model showing iron
    Clover Mini Iron Holder – solid model showing iron

    That’s a 10° tilt, chosen because it looked right. The model recomputes itself around the key dimensions, so we can raise / lower the iron, change the angle, and so forth and so on, as needed.

    Assuming that a hot end sticking out in mid-air isn’t too awful, this one looks like a keeper.

    The OpenSCAD source code:

    // Clover MCI-900 Mini Iron holder
    // Ed Nisley KE4ZNU - August 2015
    
    Layout = "Holder";					// Iron Holder
    
    //- Extrusion parameters - must match reality!
    
    ThreadThick = 0.25;
    ThreadWidth = 0.40;
    
    function IntegerMultiple(Size,Unit) = Unit * ceil(Size / Unit);
    
    Protrusion = 0.1;
    
    HoleWindage = 0.2;
    
    inch = 25.4;
    
    Tap10_32 = 0.159 * inch;
    Clear10_32 = 0.190 * inch;
    Head10_32 = 0.373 * inch;
    Head10_32Thick = 0.110 * inch;
    Nut10_32Dia = 0.433 * inch;
    Nut10_32Thick = 0.130 * inch;
    Washer10_32OD = 0.381 * inch;
    Washer10_32ID = 0.204 * inch;
    
    //------
    // Dimensions
    
    CornerRadius = 4.0;
    
    CenterHeight = 25;							// center at cord inlet on body
    
    BodyLength = 110;							// cord inlet to body curve at front flange
    
    Incline = 10;								// central angle slope
    
    FrontOD = 29;
    FrontBlock = [20,1.5*FrontOD + 2*CornerRadius,FrontOD/2 + CenterHeight + BodyLength*sin(Incline)];
    
    CordOD = 10;
    CordLen = 10;
    
    RearOD = 22;
    RearBlock = [15 + CordLen,1.5*RearOD + 2*CornerRadius,RearOD/2 + CenterHeight];
    
    PlateWidth = 2*FrontBlock[1];
    
    TextDepth = 3*ThreadThick;
    
    ScrewOC = BodyLength - FrontBlock[0]/2;
    ScrewDepth = CenterHeight - FrontOD/2 - 5;
    
    echo(str("Screw OC: ",ScrewOC));
    
    BuildSize = [200,250,200];					// largest possible thing
    
    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);
    }
    
    // Trim bottom from child object
    
    module TrimBottom(BlockSize=BuildSize,Slice=CornerRadius) {
    	
    	intersection() {
    		translate([0,0,BlockSize[2]/2])
    			cube(BlockSize,center=true);
    		translate([0,0,-Slice])
    			children();
    	}
    }
    
    // Build a rounded block-like thing
    
    module RoundBlock(Size=[20,25,30],Radius=CornerRadius,Center=false) {
    	
    	HS = Size/2 - [Radius,Radius,Radius];
    	translate([0,0,Center ? 0 : (HS[2] + Radius)])
    	hull() {
    		for (i=[-1,1], j=[-1,1], k=[-1,1]) {
    			translate([i*HS[0],j*HS[1],k*HS[2]])
    				sphere(r=Radius,$fn=4*4);
    		}
    	}
    }
    
    // Create a channel to hold something
    // This will eventually be subtracted from a block
    // The offsets are specialized for this application...
    
    module Channel(Dia,Length) {
    	
    	rotate([0,90,0])
    		linear_extrude(height=Length)
    			rotate(90)
    				hull() {
    					for (i=[-1,1])
    						translate([i*Dia,2*Dia])
    							circle(d=Dia/8);
    					circle(d=Dia,$fn=8*4);
    				}
    }
    
    // Iron-shaped series of channels to be removed from blocks
    
    module IronCutout() {
    
    	union() {
    		translate([-2*CordLen,0,0])
    			Channel(CordOD,2*CordLen + Protrusion);
    		Channel(RearOD,RearBlock[0] + Protrusion);
    		translate([BodyLength - FrontBlock[0]/2 - FrontBlock[0],0,0])
    			Channel(FrontOD,2*FrontBlock[0]);
    
    	}
    	
    }
    
    //- Build it
    
    if (Layout == "Iron")
    	IronCutout();
    
    if (Layout == "Holder")
    	difference() {
    		union() {
    			translate([(BodyLength + CordLen)/2 - CordLen,0,0])
    				TrimBottom()
    					RoundBlock(Size=[(CordLen + BodyLength),PlateWidth,CornerRadius]);
    
    			translate([(RearBlock[0]/2 - CordLen),0,0])
    				TrimBottom()
    					RoundBlock(Size=RearBlock);
    
    			translate([BodyLength - FrontBlock[0]/2,0,0]) {
    				TrimBottom()
    					RoundBlock(Size=FrontBlock);
    			}
    		}
    		
    		translate([0,0,CenterHeight])
    			rotate([0,-Incline,0])
    				IronCutout();
    		
    		translate([0,0,-Protrusion])
    			PolyCyl(Tap10_32,ScrewDepth + Protrusion,6);
    			
    		translate([ScrewOC,0,-Protrusion])
    			PolyCyl(Tap10_32,ScrewDepth + Protrusion,6);
    
    		translate([(RearBlock[0] - CordLen) + BodyLength/2 - FrontBlock[0],0,CornerRadius - TextDepth]) {
    			
    			translate([0,10,0])
    				linear_extrude(height=TextDepth + Protrusion,convexity=1)		// rendering glitches for convexity > 1
    					text("Mary",font="Ubuntu:style=Bold Italic",halign="center",valign="center");
    					
    			translate([0,-10,0])
    				linear_extrude(height=TextDepth + Protrusion,convexity=1)		// rendering glitches for convexity > 1
    				text("Nisley",font="Ubuntu:style=Bold Italic",halign="center",valign="center");
    		}
    		
    	}
    

    The M2 buzzed away for four hours on that puppy, with the first 2½ hours devoted to building the platform. That’s the downside of applying Hilbert Curve infill to two big flat surfaces, but the texture looks really good.

  • M2 Motor Mount: Better-looking Cable Cap

    An objection was raised to my original cable strain relief technique with the PETG motor mount:

    M2 Motor Mount - PETG installed - cable brace
    M2 Motor Mount – PETG installed – cable brace

    The proffered replacement had a difficult-to-print orientation:

    M2 Motor Mount - Cable Cap - original STL orientation
    M2 Motor Mount – Cable Cap – original STL orientation

    Which Meshlab’s Manipulators Tool rotated by 90°:

    M2 Motor Mount - Cable Cap
    M2 Motor Mount – Cable Cap

    And that printed without any drama (or support), at least after I sliced it to use a single perimeter thread that could cope with the arch:

    M2 Motor Mount - Cable Cap - on platform
    M2 Motor Mount – Cable Cap – on platform

    Then a few pretty cable ties wrapped everything up in a decorative package:

    M2 Motor Mount - Cable Cap - installed
    M2 Motor Mount – Cable Cap – installed

    And that’s that…

    Memo to Self: Bang on the ␛ key to get out of whatever mode the Manipulators Tool gets wedged into.

  • 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…

  • Lip Balm Holder

    A bit of tinkering with the OpenSCAD code that produced the DeoxIT bottle holder delivered a place for the cylindrical objects we use just before cycling:

    Lip Balm Holder
    Lip Balm Holder

    The tubes are 1.5 diameters tall, minus a skosh, so the cylinders stand neatly inside and don’t want to fall over. I added about 1 mm clearance and you could taper the cylinder openings for E-Z insertion, although we can eke out a miserable existence with this thing as-is.

    It works exactly as you’d expect:

    Lip Balm Holder - in action
    Lip Balm Holder – in action

    That big stick in the middle is actually skin sunscreen, not lip balm; let’s not get all pedantic. The intent is to keep those cylinders from rolling off the shelf and falling into awkward locations, which this will do.

    The OpenSCAD source code is strictly from empirical:

    // Lip Balm Tube Holder
    // Ed Nisley KE4ZNU - July 2015
    
    //- Extrusion parameters - must match reality!
    
    ThreadThick = 0.25;
    ThreadWidth = 0.40;
    
    function IntegerMultiple(Size,Unit) = Unit * ceil(Size / Unit);
    
    Protrusion = 0.1;
    
    HoleWindage = 0.2;
    
    //------
    // Dimensions
    
    Tubes = [18,26];			// tube diameters plus clearance
    
    WallThick = 2.0;
    
    Plate = [1.5*(Tubes[1] + 2*Tubes[0]),2.5*Tubes[1],IntegerMultiple(2.0,ThreadThick)];
    PlateRound = 5.0;
    
    NumSides = 8*4;
    
    //- Build it
    
    	hull() {
    		for (i=[-1,1], j=[-1,1]) {
    			translate([i*(Plate[0]/2 - PlateRound),j*(Plate[1]/2 - PlateRound),0])
    				cylinder(r=PlateRound,h=Plate[2],$fn=NumSides);
    		}
    	}
    
    	translate([0,0,Plate[2]/2])
    		rotate(180/NumSides)
    			difference() {
    				cylinder(d=(Tubes[1] + 2*WallThick),h=1.5*Tubes[1],$fn=NumSides);
    				cylinder(d=Tubes[1],h=1.5*Tubes[1] + Protrusion,$fn=NumSides);
    			}
    
    	for (i=[-1,1])
    		translate([i*((Tubes[1] + Tubes[0])/2 + 1.0*WallThick),0,Plate[2]/2])
    			rotate(180/NumSides)
    				difference() {
    					cylinder(d=(Tubes[0] + 2*WallThick),h=1.5*Tubes[0],$fn=NumSides);
    					cylinder(d=Tubes[0],h=1.5*Tubes[0] + Protrusion,$fn=NumSides);
    			}
    
  • Victoreen 710-104 Ionization Chamber: Shield Support

    Although I’d thought of a Mu-metal shield, copper foil tape should be easier and safer to shape into a simple shield. The general idea is to line the interior with copper tape, solder the joints together, cover with Kapton tape to reduce the likelihood of shorts, then stick it in place with some connector pin-and-socket combinations. Putting the tape on the outside would be much easier, but that would surround the circuitry with a layer of plastic that probably carries enough charge to throw things off.

    Anyhow, the hexagonal circuit board model now sports a hexagonal cap to support the shield:

    Victoreen 710-104 Ionization Chamber Fittings - Show with shield
    Victoreen 710-104 Ionization Chamber Fittings – Show with shield

    The ad-hoc openings fit various switches, wires, & twiddlepots:

    Victoreen 710-104 Ionization Chamber Fittings - Shield
    Victoreen 710-104 Ionization Chamber Fittings – Shield

    Ya gotta start somewhere.

    The OpenSCAD source code:

    // Victoreen 710-104 Ionization Chamber Fittings
    // Ed Nisley KE4ZNU July 2015
    
    Layout = "Show";
    					// Show - assembled parts
    					// Build - print can parts + shield
    					// BuildShield - print just the shield
    					// CanCap - PCB insulator for 6-32 mounting studs
    					// CanBase - surrounding foot for ionization chamber
    					// CanLid - generic surround for either end of chamber
    					// PCB - template for cutting PCB sheet
    					// PCBBase - holder for PCB atop CanCap
    					// Shield - electrostatic shield shell
    
    //- Extrusion parameters must match reality!
    //  Print with 2 shells and 3 solid layers
    
    ThreadThick = 0.25;
    ThreadWidth = 0.40;
    
    HoleWindage = 0.2;
    
    Protrusion = 0.1;			// make holes end cleanly
    
    AlignPinOD = 1.75;			// assembly alignment pins = filament dia
    
    inch = 25.4;
    
    function IntegerMultiple(Size,Unit) = Unit * ceil(Size / Unit);
    
    //- Screw sizes
    
    Tap4_40 = 0.089 * inch;
    Clear4_40 = 0.110 * inch;
    Head4_40 = 0.211 * inch;
    Head4_40Thick = 0.065 * inch;
    Nut4_40Dia = 0.228 * inch;
    Nut4_40Thick = 0.086 * inch;
    Washer4_40OD = 0.270 * inch;
    Washer4_40ID = 0.123 * inch;
    
    //----------------------
    // Dimensions
    
    OD = 0;											// name the subscripts
    LENGTH = 1;
    
    Chamber = [91.0 + HoleWindage,38];				// Victoreen ionization chamber dimensions
    
    Stud = [										// stud welded to ionization chamber lid
    	[6.5,IntegerMultiple(0.8,ThreadThick)],		// flat head -- generous clearance
    	[4.0,9.5],									// 6-32 screw -- ditto
    ];
    NumStuds = 3;
    StudSides = 6;									// for hole around stud
    
    BCD = 2.75 * inch;								// mounting stud bolt circle diameter
    
    PlateThick = 3.0;								// layer atop and below chamber ends
    RimHeight = 4.0;								// extending up along chamber perimeter
    WallHeight = RimHeight + PlateThick;
    WallThick = 5.0;								// thick enough to be sturdy & printable
    CapSides = 8*6;									// must be multiple of 4 & 3 to make symmetries work out right
    
    PCBFlatsOD = 85.0;								// hex dia across flats + clearance
    PCBClearance = ThreadWidth;						// clearance on each flat
    PCBThick = 1.1;
    PCBActual = [PCBFlatsOD/cos(30),PCBThick];
    PCBCutter = [(PCBFlatsOD + 2*PCBClearance)/cos(30),PCBThick - ThreadThick];		// OD = tip-to-tip dia with clearance
    
    echo(str("Actual PCB across flats: ",PCBFlatsOD));
    echo(str(" ... tip-to-tip dia: ",PCBActual[OD]));
    echo(str(" ... thickness: ",PCBActual[LENGTH]));
    
    HolderHeight = 11.0 + PCBCutter[LENGTH];		// thick enough for PCB to clear studs
    HolderShelf = 2.0;								// shelf under PCB edge
    PinAngle = 15;									// alignment pin angle on either side of holder screw
    
    echo(str("PCB holder across flats: ",PCBCutter[OD]*cos(30)));
    echo(str(" ... height: ",HolderHeight));
    
    ShieldInset = 1.0;								// shield inset from actual PCB flat
    ShieldWall = 2.0;								// wall thickness
    Shield = [(PCBFlatsOD - 2*ShieldInset)/ cos(30),35.0];		// electrostatic shield shell shape
    
    //----------------------
    // 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);
    }
    
    //- 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])
    		PolyCyl(Dia,Len,4);
    
    }
    
    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 CanLid() {
    
    	difference() {
    		cylinder(d=Chamber[OD] + 2*WallThick,h=WallHeight,$fn=CapSides);
    		translate([0,0,PlateThick])
    			PolyCyl(Chamber[OD],Chamber[1],CapSides);
    	}
    
    }
    
    module CanCap() {
    
    	difference() {
    		CanLid();
    
    		translate([0,0,-Protrusion])											// central cutout
    			rotate(180/6)
    				cylinder(d=BCD,h=Chamber[LENGTH],$fn=6);						//  ... reasonable size
    
    		for (i=[0:(NumStuds - 1)])												// stud clearance holes
    			rotate(i*360/NumStuds)
    				translate([BCD/2,0,0])
    					rotate(180/StudSides) {
    						translate([0,0,(PlateThick - (Stud[0][LENGTH] + 2*ThreadThick))])
    							PolyCyl(Stud[0][OD],2*Stud[0][LENGTH],StudSides);
    						translate([0,0,-Protrusion])
    							PolyCyl(Stud[1][OD],2*Stud[1][LENGTH],StudSides);
    					}
    
    		for (i=[0:(NumStuds - 1)], j=[-1,1])									// PCB holder alignment pins
    			rotate(i*360/NumStuds + j*PinAngle + 60)
    				translate([Chamber[OD]/2,0,0])
    					rotate(180/4 - j*PinAngle)
    						LocatingPin(Len=2*PlateThick - 2*ThreadThick);
    	}
    
    }
    
    module CanBase() {
    
    	difference() {
    		CanLid();
    		translate([0,0,-Protrusion])
    			PolyCyl(Chamber[OD] - 2*5.0,Chamber[1],CapSides);
    	}
    }
    
    module PCBTemplate() {
    
    	difference() {
    		cylinder(d=PCBActual[OD],h=max(PCBActual[LENGTH],3.0),$fn=6);		// actual PCB size, overly thick
    		translate([0,0,-Protrusion])
    			cylinder(d=10,h=10*PCBActual[LENGTH],$fn=12);
    	}
    }
    
    module PCBBase() {
    
    	difference() {
    		cylinder(d=Chamber[OD] + 2*WallThick,h=HolderHeight,$fn=CapSides);		// outer rim
    
    		rotate(30) {
    			translate([0,0,-Protrusion])										// central hex
    				cylinder(d=(PCBActual[OD] - HolderShelf/cos(30)),h=2*HolderHeight,$fn=6);
    
    			translate([0,0,HolderHeight - PCBCutter[LENGTH]])					// hex PCB recess
    				cylinder(d=PCBCutter[OD],h=HolderHeight,$fn=6);
    
    			for (i=[0:NumStuds - 1])											// PCB retaining screws
    				rotate(i*120 + 30)
    					translate([(PCBCutter[OD]*cos(30)/2 + Clear4_40/2 + ThreadWidth),0,-Protrusion])
    						rotate(180/6)
    							PolyCyl(Tap4_40,2*HolderHeight,6);
    
    			for (i=[0:(NumStuds - 1)], j=[-1,1])								// PCB holder alignment pins
    				rotate(i*360/NumStuds + j*PinAngle + 30)
    					translate([Chamber[OD]/2,0,0])
    						rotate(180/4 - j*PinAngle)
    							LocatingPin(Len=PlateThick);
    		}
    
    		for (i=[0:NumStuds - 1])												// segment isolation
    			rotate(i*120 - 30)
    				translate([0,0,-Protrusion]) {
    					linear_extrude(height=2*HolderHeight)
    						polygon([[0,0],[Chamber[OD],0],[Chamber[OD]*cos(60),Chamber[OD]*sin(60)]]);
    				}
    	}
    }
    
    //-- Electrostatic shield
    //		the cutouts are completely ad-hoc
    
    module ShieldShell() {
    
    CutHeight = 7.0;
    
    	difference() {
    		cylinder(d=Shield[OD],h=Shield[LENGTH],$fn=6);
    		translate([0,0,-ShieldWall])
    			cylinder(d=(Shield[OD] - 2*ShieldWall/cos(30)),h=Shield[LENGTH],$fn=6);
    
    		translate([Shield[OD]/4 - 20/2,Shield[OD]/2,(CutHeight - Protrusion)/2])
    			rotate(90)
    				cube([Shield[OD],20,CutHeight + Protrusion],center=true);
    
    		translate([-Shield[OD]/4 + 5/2,Shield[OD]/2,(CutHeight - Protrusion)/2])
    			rotate(90)
    				cube([Shield[OD],5,CutHeight + Protrusion],center=true);
    
    		translate([-Shield[OD]/2,0,(CutHeight - Protrusion)/2])
    				cube([Shield[OD],5,CutHeight + Protrusion],center=true);
    
    	}
    
    }
    
    //----------------------
    // Build it
    
    ShowPegGrid();
    
    if (Layout == "CanLid") {
    	CanLid();
    }
    
    if (Layout == "CanCap") {
    	CanCap();
    }
    
    if (Layout == "CanBase") {
    	CanBase();
    }
    
    if (Layout == "PCBBase") {
    	PCBBase();
    }
    
    if (Layout == "PCB") {
    	PCBTemplate();
    }
    
    if (Layout == "Shield") {
    	ShieldShell();
    }
    
    if (Layout == "Show") {
    	CanBase();
    	color("Orange",0.5)
    		translate([0,0,PlateThick + Protrusion])
    			cylinder(d=Chamber[OD],h=Chamber[LENGTH],$fn=CapSides);
    	translate([0,0,(2*PlateThick + Chamber[LENGTH] + 2*Protrusion)])
    		rotate([180,0,0])
    			CanCap();
    	translate([0,0,(2*PlateThick + Chamber[LENGTH] + 5.0)])
    		PCBBase();
    	color("Green",0.5)
    		translate([0,0,(2*PlateThick + Chamber[LENGTH] + 7.0 + HolderHeight)])
    			rotate(30)
    				PCBTemplate();
    	translate([0,0,(2*PlateThick + Chamber[LENGTH] + 15.0 + HolderHeight)])
    		rotate(30)
    			ShieldShell();}
    
    if (Layout == "Build") {
    
    	translate([-0.50*Chamber[OD],-0.60*Chamber[OD],0])
    		CanCap();
    
    	translate([0.55*Chamber[OD],-0.60*Chamber[OD],0])
    		rotate(30)
    			translate([0,0,Shield[LENGTH]])
    				rotate([0,180,0])
    					ShieldShell();
    
    	translate([-0.25*Chamber[OD],0.60*Chamber[OD],0])
    		CanBase();
    	translate([0.25*Chamber[OD],0.60*Chamber[OD],0])
    		PCBBase();
    }
    
    if (Layout == "BuildShield") {
    
    	translate([0,0,Shield[LENGTH]])
    		rotate([0,180,0])
    				ShieldShell();
    
    }
    
  • Victoreen 710-104 Ionization Chamber: Circuit Fixture

    The general idea is to put the electrometer circuitry directly atop the Victoreen 710-104 ionization chamber, so as to minimize the distance from the center collector electrode to the electrometer input. After a few false starts, this looked promising:

    Victoreen 710-104 Ionization Chamber Fittings - Show layout
    Victoreen 710-104 Ionization Chamber Fittings – Show layout

    The hexagonal circuit board fits the can so nicely that I’ll run with it, despite the over-the-top twee factor. Because it’s so hard to freehand a hex, I printed the green object as a tracing template, despite having the Slic3r preview show the parts just barely fitting on the M2 platform:

    Victoreen 710-104 Ionization Chamber Fittings - Build layout
    Victoreen 710-104 Ionization Chamber Fittings – Build layout

    Fortunately, my configuration hand is strong:

    Victoreen 710-104 Fittings - on M2 platform
    Victoreen 710-104 Fittings – on M2 platform

    The skirt measures 0.25±0.05 around the entire perimeter, with a slight positive bias (platform too low) along the left side and a corresponding negative bias on the right. Both sides look just fine to me.

    A pair of alignment pegs hold each board support in place while gluing:

    Victoreen 710-104 Fittings - clamping
    Victoreen 710-104 Fittings – clamping

    Next time around, I’ll glue the supports with the circuit board template laid in place to ensure the edges have the proper orientation, but they came out surprisingly close just by matching the outer perimeters. Of course, I probably bandsawed / belt sanded the carefully traced hex just slightly off-kilter.

    The outer perimeter has 48 sides. Making it a multiple of three means each board support has the same pattern of sides and all will be interchangeable. Making it a multiple of four means each quadrant has the same pattern of sides and the ring looks pleasingly symmetrical. The factor-of-three is most important: you want interchangeable supports. Trust me on this.

    The bottom ring keeps the solder dimple that seals the can base off the desk, but I also stuck a quartet of rubber feet on the can for better traction.

    Here’s what it looks like with the two A23 12 V bias batteries in their holders, affixed to the can with foam tape:

    Victoreen 710-104 Fittings - assembled
    Victoreen 710-104 Fittings – assembled

    The OpenSCAD source code includes a few more tweaks:

    // Victoreen 710-104 Ionization Chamber Fittings
    // Ed Nisley KE4ZNU July 2015
    
    Layout = "Show";
    					// Show - assembled parts
    					// Build - print them out!
    					// CanCap - PCB insulator for 6-32 mounting studs
    					// CanBase - surrounding foot for ionization chamber
    					// CanLid - generic surround for either end of chamber
    					// PCB - template for cutting PCB sheet
    					// PCBBase - holder for PCB atop CanCap
    
    BuildTemplate = false;			// true to build PCB template along with everything else
    
    //- Extrusion parameters must match reality!
    //  Print with 2 shells and 3 solid layers
    
    ThreadThick = 0.25;
    ThreadWidth = 0.40;
    
    HoleWindage = 0.2;
    
    Protrusion = 0.1;			// make holes end cleanly
    
    AlignPinOD = 1.75;			// assembly alignment pins = filament dia
    
    inch = 25.4;
    
    function IntegerMultiple(Size,Unit) = Unit * ceil(Size / Unit);
    
    //- Screw sizes
    
    Tap4_40 = 0.089 * inch;
    Clear4_40 = 0.110 * inch;
    Head4_40 = 0.211 * inch;
    Head4_40Thick = 0.065 * inch;
    Nut4_40Dia = 0.228 * inch;
    Nut4_40Thick = 0.086 * inch;
    Washer4_40OD = 0.270 * inch;
    Washer4_40ID = 0.123 * inch;
    
    
    //----------------------
    // Dimensions
    
    OD = 0;											// name the subscripts
    LENGTH = 1;
    
    Chamber = [91.0 + HoleWindage,38];				// Victoreen ionization chamber dimensions
    
    Stud = [										// stud welded to ionization chamber lid
    	[6.5,IntegerMultiple(0.8,ThreadThick)],		// flat head -- generous clearance
    	[4.0,9.5],									// 6-32 screw -- ditto
    ];
    NumStuds = 3;
    StudSides = 6;									// for hole around stud
    
    BCD = 2.75 * inch;								// mounting stud bolt circle diameter
    
    PlateThick = 3.0;								// layer atop and below chamber ends
    RimHeight = 4.0;								// extending up along chamber perimeter
    WallHeight = RimHeight + PlateThick;
    WallThick = 5.0;								// thick enough to be sturdy & printable
    CapSides = 8*6;									// must be multiple of 4 & 3 to make symmetries work out right
    
    PCBFlatsOD = 85.0 + 2*ThreadWidth;				// hex dia across flats + clearance
    PCBThick = 1.1;
    PCB = [PCBFlatsOD / cos(30),PCBThick - ThreadThick];		// OD = tip-to-tip dia
    
    echo(str("Actual PCB across flats: ",PCBFlatsOD - 2*ThreadWidth));
    echo(str(" ... tip-to-tip dia: ",(PCBFlatsOD - 2*ThreadWidth)/cos(30)));
    echo(str(" ... thickness: ",PCBThick));
    
    HolderHeight = 11.0 + PCB[LENGTH];				// thick enough for PCB to clear studs
    HolderShelf = 2.0;								// shelf under PCB edge
    
    echo(str("PCB holder height: ",HolderHeight));
    echo(str(" ... across flats: ",PCBFlatsOD));
    
    //----------------------
    // 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);
    }
    
    //- 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])
    		PolyCyl(Dia,Len,4);
    
    }
    
    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 CanLid() {
    	
    	difference() {
    		cylinder(d=Chamber[OD] + 2*WallThick,h=WallHeight,$fn=CapSides);
    		translate([0,0,PlateThick])
    			PolyCyl(Chamber[OD],Chamber[1],CapSides);
    	}
    	
    }
    
    module CanCap() {
    
    	difference() {
    		CanLid();
    		
    		translate([0,0,-Protrusion])											// central cutout
    //			cylinder(d=(BCD - 2*5.0),h=Chamber[LENGTH],$fn=CapSides);
    			rotate(180/6)
    				cylinder(d=BCD,h=Chamber[LENGTH],$fn=6);
    			
    		for (i=[0:(NumStuds - 1)])												// stud clearance holes
    			rotate(i*360/NumStuds)
    				translate([BCD/2,0,0])
    					rotate(180/StudSides) {
    						translate([0,0,(PlateThick - (Stud[0][LENGTH] + 2*ThreadThick))])
    							PolyCyl(Stud[0][OD],2*Stud[0][LENGTH],StudSides);
    						translate([0,0,-Protrusion])
    							PolyCyl(Stud[1][OD],2*Stud[1][LENGTH],StudSides);
    					}
    					
    		for (i=[0:(NumStuds - 1)], j=[-1,1])									// PCB holder alignment pins
    			rotate(i*360/NumStuds + j*15 + 60)
    				translate([Chamber[OD]/2,0,0])
    					rotate(180/4)
    						LocatingPin(Len=2*PlateThick - 2*ThreadThick);
    	}
    
    }
    
    module CanBase() {
    	
    	difference() {
    		CanLid();
    		translate([0,0,-Protrusion])
    			PolyCyl(Chamber[OD] - 2*5.0,Chamber[1],CapSides);
    	}
    }
    
    module PCBTemplate() {
    	
    	difference() {
    		cylinder(d=((PCBFlatsOD - 2*ThreadWidth)/cos(30)),h=max(PCB[LENGTH],3.0),$fn=6);		// actual PCB size, overly thick
    		translate([0,0,-Protrusion])
    			cylinder(d=10,h=10*PCB[LENGTH],$fn=12);
    	}
    }
    
    module PCBBase() {
    
    	difference() {
    		cylinder(d=Chamber[OD] + 2*WallThick,h=HolderHeight,$fn=CapSides);
    		
    		rotate(30) {
    			translate([0,0,-Protrusion])										// central hex
    				cylinder(d=(PCBFlatsOD - 2*HolderShelf)/cos(30),h=2*HolderHeight,$fn=6);	
    				
    			translate([0,0,HolderHeight - PCB[LENGTH]])							// hex PCB recess
    				cylinder(d=PCB[OD],h=HolderHeight,$fn=6);
    				
    			for (i=[0:NumStuds - 1])											// PCB retaining screws
    				rotate(i*120 + 30)
    					translate([(PCBFlatsOD/2 + Clear4_40/2 + ThreadWidth),0,-Protrusion])
    						rotate(180/6)
    							PolyCyl(Tap4_40,2*HolderHeight,6);
    							
    			for (i=[0:(NumStuds - 1)], j=[-1,1])								// PCB holder alignment pins
    				rotate(i*360/NumStuds + j*15 + 30)
    					translate([Chamber[OD]/2,0,0])
    						rotate(180/4)
    							LocatingPin(Len=PlateThick);
    		}
    		
    		for (i=[0:NumStuds - 1])												// segment isolation
    			rotate(i*120 - 30)
    				translate([0,0,-Protrusion]) {
    					linear_extrude(height=2*HolderHeight)
    						polygon([[0,0],[Chamber[OD],0],[Chamber[OD]*cos(60),Chamber[OD]*sin(60)]]);
    				}
    	}
    	
    
    }
    
    
    //----------------------
    // Build it
    
    ShowPegGrid();
    
    if (Layout == "CanLid") {
    	CanLid();
    }
    
    if (Layout == "CanCap") {
    	CanCap();
    }
    
    if (Layout == "CanBase") {
    	CanBase();
    }
    
    if (Layout == "PCBBase") {
    	PCBBase();
    }
    
    if (Layout == "PCB") {
    	PCBTemplate();
    }
    
    if (Layout == "Show") {
    	CanBase();
    	color("Orange",0.5)
    		translate([0,0,PlateThick + Protrusion])
    			cylinder(d=Chamber[OD],h=Chamber[LENGTH],$fn=CapSides);
    	translate([0,0,(2*PlateThick + Chamber[LENGTH] + 2*Protrusion)])
    		rotate([180,0,0])
    			CanCap();
    	translate([0,0,(2*PlateThick + Chamber[LENGTH] + 5.0)])
    		PCBBase();
    	color("Green",0.5)
    		translate([0,0,(2*PlateThick + Chamber[LENGTH] + 7.0 + HolderHeight)])
    			rotate(30)
    				PCBTemplate();
    }
    
    if (Layout == "Build") {
    	
    	if (BuildTemplate) {
    		translate([-0.50*Chamber[OD],-0.60*Chamber[OD],0])
    			CanCap();
    			
    		translate([0.55*Chamber[OD],-0.60*Chamber[OD],0])
    			rotate(30)
    				PCBTemplate();
    	}
    	else {
    		translate([-0.25*Chamber[OD],-0.60*Chamber[OD],0])
    			CanCap();
    	}
    		
    	translate([-0.25*Chamber[OD],0.60*Chamber[OD],0])
    		CanBase();
    	translate([0.25*Chamber[OD],0.60*Chamber[OD],0])
    		PCBBase();
    }
    
  • 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.