Machine Shop

CNC 3018-Pro: Home Switches

The CNC 3018-Pro doesn’t absolutely need home switches, but (in principle) they let you install a workholding fixture at a known position, home the axes, pick a preset coordinate system for the fixture, and not have to touch off the axes before making parts.

Having used Makerbot-style endstop switch PCBs for the MPCNC, this was straightforward:

3018 CNC - Endstop switches - overview
3018 CNC – Endstop switches – overview

The X and Z axis switches simply press against the appropriate moving parts:

3018 CNC - X and Z Endstops
3018 CNC – X and Z Endstops

The little tab stuck on the tool clamp provides a bit of clearance around the upper part of the X axis assembly.

The Y axis switch needed a slightly tapered tab to extend the bearing holder:

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

It’s made from a random scrap of clear plastic, hand-filed to suit, and stuck on the bearing to trigger the switch in exactly the right spot.

You can find elaborate switch mounts on Thingiverse, but I’ve become a big fan of genuine 3M outdoor-rated foam tape for this sort of thing: aggressive stickiness, no deterioration, possible-but-not-easy removal.

The switches need +5 V power, so add a small hack to the CAMTool V3.3 control board to let the connectors plug right in:

3018 CNC CAMTool - Endstop power mod - installed
3018 CNC CAMTool – Endstop power mod – installed

The solid models borrow their central depression around the switch terminals from the MPCNC blocks:

3018 Home Switch Mounts - Slic3r preview
3018 Home Switch Mounts – Slic3r preview

The OpenSCAD source code as a GitHub Gist:

// 3018-Pro Mount for Makerbot Endstop PCB
// Ed Nisley KE4ZNU - 2019-07
/* [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,PCB.y,5.0];
module XMount() {
difference() {
cube(XBlock,center=false);
translate(SwitchOffset + [0,0,XBlock.z - SwitchClear.z/2])
cube(SwitchClear + [0,0,Protrusion],center=true);
}
}
YBlock = [PCB.x + 10.0,PCB.y,20.0];
module YMount() {
difference() {
translate([-10.0,0,0])
cube(YBlock,center=false);
translate([0,-Protrusion,10.0])
cube(YBlock + [0,2*Protrusion,0],center=false);
translate(SwitchOffset + [0,0,10.0 - 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([0,-ZBlock.y,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,YBlock.y,0])
XMount();
translate([0,-YBlock.y/2])
YMount();
translate([0,-(ZBlock.y + YBlock.y)])
ZMount();
}
view raw Home Switch Mounts.scad hosted with ❤ by GitHub

The dimension doodles:

3018 Home Switch Mounts - Dimension Doodles
3018 Home Switch Mounts – Dimension Doodles