OpenSCAD source code: MPCNC holder for diamond drag scribe using LM3UU linear bearings

Diamond Scribe - LM3UU bearings.scad

// Drag Knife Holder using LM12UU linear bearing
// Ed Nisley KE4ZNU - 2019-04-26
// 2019-05-09 LM3UU for diamond scribe
// 2019-05-28 taper end, single spring around shaft

Layout = "Build";                       // [Build, Show, Puck, Mount, Plate]

/* [Extrusion] */

ThreadThick = 0.25;       // [0.20, 0.25]
ThreadWidth = 0.40;       // [0.40, 0.40]

/* [Hidden] */

Protrusion = 0.1;        // [0.01, 0.1]

HoleWindage = 0.2;

inch = 25.4;

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

ID = 0;
OD = 1;
LENGTH = 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);
}

//- Dimensions

// Knife holder & suchlike

KnifeBody = [3.0,9.0,2.0];            // washer epoxied to diamond shaft, with epoxy fillet

Spring = [9.5,10.0,3*ThreadThick];   // compression spring around shaft, LENGTH = socket depth

WallThick = 4.0;                      // minimum thickness / width

Screw = [4.0,8.5,8.0];                // holding it all together, OD = washer

Insert = [4.0,6.0,10.0];              // brass insert

Bearing = [3.0,7.0,2*10.0 + WallThick];     // linear bearing body (pair + small gap)

// Basic shape of DW660 snout fitting into the holder
// Lip goes upward to lock into MPCNC mount

Snout = [44.6,50.0,9.6];                      // LENGTH = ID height
Lip = 4.0;                                    // height of lip at end of snout

Plate = [KnifeBody[ID],Snout[OD] - WallThick,WallThick];   // spring reaction plate

PuckOAL = max(Bearing[LENGTH],(Snout[LENGTH] + Lip));      // total height of DW660 fitting
echo(str("PuckOAL: ",PuckOAL));
Key = [Snout[ID],25.7,(Snout[LENGTH] + Lip)];               // rectangular key

NumScrews = 3;

ScrewBCD = 2.5*(Bearing[OD]/2 + Insert[OD]/2 + WallThick);

NumSides = 9*4;                         // cylinder facets (multiple of 3 for lathe trimming)

module DW660Puck() {

  translate([0,0,PuckOAL])
    rotate([180,0,0]) {
      cylinder(d=Snout[OD],h=Lip/2,$fn=NumSides);
      translate([0,0,Lip/2])
        cylinder(d1=Snout[OD],d2=Snout[ID],h=Lip/2,$fn=NumSides);
      cylinder(d=Snout[ID],h=(Snout[LENGTH] + Lip),$fn=NumSides);
      translate([0,0,(Snout[LENGTH] + Lip) - Protrusion])
        cylinder(d1=Snout[ID],d2=2*WallThick + Bearing[OD],h=PuckOAL - (Snout[LENGTH] + Lip),$fn=NumSides);
      intersection() {
        translate([0,0,0*Lip + Key.z/2])
          cube(Key,center=true);
        cylinder(d=Snout[OD],h=Lip + Key.z,$fn=NumSides);
      }
    }
}

module MountBase() {

  difference() {
    DW660Puck();

    translate([0,0,-Protrusion])                    // bearing
      PolyCyl(Bearing[OD],2*PuckOAL,NumSides);

    for (i=[0:NumScrews - 1])                       // clamp screws
      rotate(i*360/NumScrews)
        translate([ScrewBCD/2,0,-Protrusion])
          rotate(180/8)
            PolyCyl(Insert[OD],2*PuckOAL,8);
  }
}

module SpringPlate() {
  difference() {
    cylinder(d=Plate[OD],h=Plate[LENGTH],$fn=NumSides);

    translate([0,0,-Protrusion])                    // ample shaft clearance
      PolyCyl(1.5*KnifeBody[ID],2*PuckOAL,NumSides);

//   translate([0,0,Plate[LENGTH] - KnifeBody[LENGTH]])    //  flange, snug fit
//      PolyCyl(KnifeBody[OD],KnifeBody[LENGTH] + Protrusion,NumSides);

    translate([0,0,Plate[LENGTH] - Spring[LENGTH]])    //  spring retainer
      PolyCyl(Spring[OD],Spring[LENGTH] + Protrusion,NumSides);

    for (i=[0:NumScrews - 1])                       // clamp screws
      rotate(i*360/NumScrews)
        translate([ScrewBCD/2,0,-Protrusion])
          rotate(180/8)
          PolyCyl(Screw[ID],2*PuckOAL,8);
  }
}

//-----
// Build it

if (Layout == "Puck")
  DW660Puck();

if (Layout == "Plate")
  SpringPlate();

if (Layout == "Mount")
  MountBase();

if (Layout == "Show") {
  MountBase();
  translate([0,0,1.5*PuckOAL])
    rotate([180,0,0])
      SpringPlate();
}

if (Layout == "Build") {
  translate([0,Snout[OD]/2,PuckOAL])
    rotate([180,0,0])
      MountBase();
  translate([0,-Snout[OD]/2,0])
    SpringPlate();
}

More details on my blog at https://wp.me/poZKh-8f8