The New Hotness

As part of entombing the endstop PCBs in epoxy, I tweaked the switch mounts to (optionally) eliminate the screw holes and (definitely) rationalize the spacings:

MPCNC MB Endstop Mount - No screws — MPCNC MB Endstop Mount – No screws

The sectioned view shows the cable tie slot neatly centered between the bottom of the switch terminal pit and the EMT rail, now with plenty of meat above the cable tie latch recess. The guide ramp on the other side has a more-better position & angle, too.

A trial fit before dabbing on the epoxy:

MPCNC - Endstop Mount for epoxy coating - trial fit — MPCNC – Endstop Mount for epoxy coating – trial fit

The 3M black foam tape works wonderfully well!

After the epoxy cures, it’s all good:

MPCNC - Epoxy-coated Endstop - Installed — MPCNC – Epoxy-coated Endstop – Installed

The OpenSCAD source code as a GitHub Gist:

	// MPCNC Endstop Mount for Makerbot PCB on EMT tubing
	// Ed Nisley KE4ZNU – 2017-12-04

	/* [Build Options] */

	Layout = "Show"; // [Build, Show, Block]

	Holes = false; // holes for switch screws

	Section = true; // show internal details

	/* [Extrusion] */

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

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

	/* [Hidden] */

	Protrusion = 0.01; // [0.01, 0.1]

	HoleWindage = 0.2;

	ID = 0;
	OD = 1;
	LENGTH = 2;

	/* [Sizes] */

	RailOD = 23.5; // actual rail OD

	SwitchHeight = 8.0; // switch PCB distance from rail OD

	Strap = [5.5,50,2.0]; // nylon strap securing block to rail
	StrapHead = [8.2,3.0,5.5]; // recess for strap ratchet head

	Screw = [2.0,3.6,7.0]; // thread dia, head OD, screw length

	HoleOffset = [2.5,19.0/2]; // PCB mounting holes from PCB edge, rail center

	SwitchClear = [6.0,15,3.0]; // clearance around switch pins
	SwitchOffset = [6.0,0]; // XY center of switch from holes

	StrapHeight = (SwitchHeight – SwitchClear[2])/2; // strap center from rail

	Block = [16.4,26.0,RailOD/2 + SwitchHeight]; // basic block shape

	//- 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);
	}

	//- Shapes

	// Main block constructed centered on XY with Z=0 at top of rail

	module PCBBlock() {
	difference() {
	translate([-Block[0]/2,-Block[1]/2,-RailOD/2])
	cube(Block,center=false);

	translate([(SwitchOffset[0] + HoleOffset[0] – Block[0]/2),
	SwitchOffset[1],
	(SwitchHeight – SwitchClear[2]/2 + Protrusion/2)])
	cube(SwitchClear + [0,0,Protrusion],center=true);

	if (Holes)
	for (j=[-1,1])
	translate([HoleOffset[0] – Block[0]/2,j*HoleOffset[1],(Block[2]/2 – Screw[LENGTH])])
	rotate(180/6)
	if (true) // true = loose fit
	PolyCyl(Screw[ID],Screw[LENGTH] + Protrusion,6);
	else
	cylinder(d=Screw[ID],h=Screw[LENGTH] + Protrusion,$fn=6);

	translate([0,0,StrapHeight])
	cube(Strap,center=true);

	translate([0, // strap head recess
	(Block[1]/2 – StrapHead[1]/2 + Protrusion),
	StrapHeight – Strap[2]/2 + StrapHead[2]/2])
	cube(StrapHead + [0,Protrusion,0],center=true);

	StrapAngle = atan((StrapHeight + RailOD/4)/Strap[2]); // a reasonable angle
	echo(str("Strap Angle: ",StrapAngle));
	translate([0,-(Block[1]/2 – Strap[2]/(2*sin(StrapAngle))),StrapHeight])
	rotate([StrapAngle,0,0])
	translate([0,-Strap[1]/2,0])
	cube(Strap,center=true);

	if (Section)
	translate([Block[0]/2,0,0])
	cube(Block + [0,2Protrusion,2Block[2]],center=true);
	}
	}

	module Mount() {

	difference() {
	translate([0,0,RailOD/2])
	PCBBlock();
	rotate([0,90,0])
	cylinder(d=RailOD,h=3*Block[0],center=true);
	}

	}

	//- Build things

	if (Layout == "Show") {
	Mount();
	color("Yellow",0.5)
	rotate([0,90,0])
	cylinder(d=RailOD,h=3*Block[0],center=true);
	}

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

	if (Layout == "Build")
	translate([0,0,Block[2]])
	rotate([180,0,0])
	Mount();

view raw MPCNC MB Endstop Mount.scad hosted with ❤ by GitHub

The New Hotness

MPCNC: Re-Improved Endstop Switch Mount