The New Hotness

Although putting a Z-axis height probe in a rigid pen holder worked well enough, it’d be handy to have a probe with a stud suitable for clamping in the DW660 spindle (with the power off!):

MPCNC - Z probe - DW660 - 0.25 collet — MPCNC – Z probe – DW660 – 0.25 collet

Inside, it uses the same pushbutton and pogo pin as the pen holder design, with a similar brass tube around the pogo pin.

There’s a conspicuous lack of good wire management; we all know where those wires will snap. In practice, you’d secure it to the DW660 power cord, way up on top, to eliminate most of the flexing. Still, it wants better strain relief than its gets from those heatstink tubes.

The solid model looks like a weaving shuttle:

MPCNC - Autolevel probe - collet - Slic3r preview — MPCNC – Autolevel probe – collet – Slic3r preview

It’s sitting upside-down in a 5 mm brim for more platform adhesion.

The next one will have a 1/8 inch stud to fit the DW660’s other collet and shorten the top by 3/8 inch, because I want the rod inserted three diameters for stability. The bottom can’t get much shorter, because the pogo pin determines the switch-to-tip distance. Maybe a simple membrane switch will work well enough?

You can see the depression in the glass sheet pretty clearly in a bCNC Autolevel scan on 30 mm centers (clicky for more dots):

bCNC - Probe Array - 600x390 30 mm OC - ISO2 — bCNC – Probe Array – 600×390 30 mm OC – ISO2

The OpenSCAD source code as a GitHub Gist:

	// MPCNC Z Axis Height Probe for router collet
	// Ed Nisley KE4ZNU – 2018-02-14

	Layout = "Build"; // Build, Show

	Section = false;

	/* [Extrusion] */

	ThreadThick = 0.25; // [0.20, 0.25]
	ThreadWidth = 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);
	}

	/* [Switch] */

	SwitchBody = [7.8,6.8,7.0]; // PCB mount hardware extends infinitely to +Y
	SwitchButton = [3.5,5.0,1.0]; // OD allows some clearance
	SwitchClear = 5.0; // room for pad atop probe rod

	SwitchZ = SwitchBody.z + SwitchButton.z + SwitchClear;

	Sleeve = [1.5,2.5,15.0]; // tube around pogo pin

	ShankOD = 0.25 * inch; // rod into tool collet

	/* [Hidden] */

	WallThick = 3.0; // basic wall & floor thickness

	ProbeBody = [Sleeve[OD],
	2*WallThick + sqrt(pow(SwitchBody.x,2) + pow(SwitchBody.y,2)),
	3*ShankOD + SwitchZ + Sleeve[LENGTH]];

	echo(str("Probe Body: ",ProbeBody));

	NumSides = 2*4;

	//—–
	// Define shapes

	module Switch() {
	union() {
	translate([0,0,SwitchBody.z/2])
	cube(SwitchBody,center=true);
	translate([0,ProbeBody[OD]/2 – SwitchBody.y/2,(SwitchBody.z + SwitchButton.z)/2])
	cube([SwitchBody.x,ProbeBody[OD],SwitchBody.z + SwitchButton[LENGTH]],center=true);
	translate([0,0,SwitchBody.z])
	PolyCyl(SwitchButton[OD],SwitchButton[LENGTH] + SwitchClear,6);
	}
	}

	module ProbeHolder() {

	difference() {
	hull() {
	PolyCyl(Sleeve[OD] + 6*ThreadWidth,Protrusion,NumSides);
	translate([0,0,Sleeve.z])
	rotate(180/8)
	PolyCyl(ProbeBody[OD],SwitchZ,NumSides);
	translate([0,0,Sleeve.z + SwitchZ + 3*ShankOD – Protrusion])
	PolyCyl(ShankOD + 10*ThreadWidth,Protrusion,NumSides);
	}
	translate([0,0,SwitchZ + Sleeve[LENGTH]])
	rotate([0,180,0])
	Switch();
	translate([0,0,-Protrusion])
	PolyCyl(Sleeve[OD],Sleeve[LENGTH] + 2*Protrusion,NumSides);
	translate([0,0,Sleeve.z + SwitchZ – Protrusion])
	PolyCyl(ShankOD,3ShankOD + 2Protrusion,NumSides);
	if (Section)
	translate([ProbeBody[OD]/2,0,ProbeBody[LENGTH]/2])
	cube([ProbeBody[OD],2ProbeBody[OD],ProbeBody[LENGTH] + 2Protrusion],center=true);
	}

	}

	//—–
	// Build it

	if (Layout == "Show")
	ProbeHolder();

	if (Layout == "Build") {
	translate([0,0,ProbeBody.z])
	rotate([0,180,0])
	ProbeHolder();
	}

view raw Z Axis Height Probe – collet.scad hosted with ❤ by GitHub

The New Hotness

MPCNC – Autolevel Probe, Collet Edition