The New Hotness

A few months of inactivity left the CNC-3018XL table parked in its homed position where the gentle-but-inexorable pressure of the switch lever displaced the foam holding the plastic actuator tab on the X-axis bearing enough that it would no longer operate reliably:

3018 CNC - Y axis endstop — 3018 CNC – Y axis endstop

Putting foam tape in a highly leveraged position produces the same poor results as in finance.

The fix requires reorienting the switch so a solid block on the bearing can push directly on the actuator lever:

CNC-3018 X Home Switch - bottom view — CNC-3018 X Home Switch – bottom view

The block must curve around the bearing to give the tape enough surface area for a good grip:

CNC-3018 X Home Switch - oblique view — CNC-3018 X Home Switch – oblique view

The solid model for the new X-axis mount looks about like you’d expect:

CNC-3018 X Home Switch Mount - solid model — CNC-3018 X Home Switch Mount – solid model

I increased the home switch pulloff to 2 mm, although it’s not clear that will make any difference in the current orientation.

The OpenSCAD source code as a GitHub Gist:

	// 3018-Pro Mount for Makerbot Endstop PCB
	// Ed Nisley KE4ZNU – 2019-07 (using OEM machine axes)
	// 2022-02-02 rotate X block (after renaming axes to match new layout)

	/* [Build Options] */

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

	/* [Hidden] */

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

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

	Protrusion = 0.01; // [0.01, 0.1]

	HoleWindage = 0.2;

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

	//- Shapes

	// Basic PCB with hole for switch pins
	// origin at switch actuator corner, as seen looking at component side

	SwitchClear = [15.0,5.0,2.0]; // clearance around switch pins
	SwitchOffset = [12.5,9.0,0.0]; // center of switch pins from actuator corner

	PCB = [26.0,16.4,2*SwitchClear.z]; // switch PCB beyond connector, pin height

	//XBlock = [PCB.x + 10.0,PCB.y,20.0];
	XBlock = [PCB.x,PCB.y,10.0];
	XBearing = [10.0,26.5,28.5];
	XPin = [10.0,20.0,10.0];

	module XMount() {

	if (false) // side-push switch tended to slip
	difference() {
	translate([-10.0,0,0])
	cube(XBlock,center=false);
	translate([0,-Protrusion,10.0])
	cube(XBlock + [0,2*Protrusion,0],center=false);
	translate(SwitchOffset + [0,0,10.0 – SwitchClear.z/2])
	cube(SwitchClear + [0,0,Protrusion],center=true);
	}
	else {
	difference() {
	cube(XBlock,center=false);
	translate(SwitchOffset + [0,0,XBlock.z – SwitchClear.z/2])
	cube(SwitchClear + [0,0,Protrusion],center=true);
	}

	translate([1.25*XBlock.x,0,0])
	difference() {
	cube(XPin + [0,0,XBearing[OD]/4],center=false);
	translate([-Protrusion,XPin.y/2,XPin.z + XBearing[OD]/2])
	rotate([0,90,0])
	cylinder(d=XBearing[OD],h=XPin.x + 2*Protrusion,center=false);
	translate([-Protrusion,-XPin.y/2,XPin.z])
	cube(XPin + [2*Protrusion,0,0],center=false);
	}
	}
	}

	YBlock = [PCB.x,PCB.y,5.0];

	module YMount() {

	difference() {
	cube(YBlock,center=false);
	translate(SwitchOffset + [0,0,YBlock.z – SwitchClear.z/2])
	cube(SwitchClear + [0,0,Protrusion],center=true);
	}

	}

	ZBlock = [PCB.x,PCB.y,6.0];
	ZPin = [20.0,10.0,5.5];


	module ZMount() {

	difference() {
	cube(ZBlock,center=false);
	translate(SwitchOffset + [0,0,ZBlock.z – SwitchClear.z/2])
	cube(SwitchClear + [0,0,Protrusion],center=true);
	}

	translate([1.25*ZBlock.x,0,0])
	difference() {
	cube(ZPin,center=false);
	translate([ZPin.x/2,-Protrusion,4.0])
	cube(ZPin + [0,2*Protrusion,0],center=false);
	}
	}

	//- Build things

	if (Layout == "Show") {
	translate([0,XBlock.y,0])
	YMount();
	translate([0,-XBlock.y/2])
	XMount();
	translate([0,-(ZBlock.y + XBlock.y)])
	ZMount();
	}

view raw Home Switch Mounts.scad hosted with ❤ by GitHub

The New Hotness

CNC-3018XL: Improved X-Axis Home Switch Mount