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In Feb - 2016 I added a micro switch to my Shapeoko 2 CNC router.

This switch and some gcode allowed me to:

  1. Home the spindle
  2. Pause for a bit change
  3. Re-zero a different size bit.
  4. then - return to a preset zero on x,y.

Mainly focused on making a switch that would allow me to duplicate the z-zero process no matter how many end mills I changed during a job. for instance, Using a .1/4" end mill for roughing, and a .125" end mill for finish.

This micro switch literally change and enhanced my bit changes and the overall quality of the work completed on my CNC router.

See this instructable https://www.instructables.com/id/Automated-Z-Axis-...

While this switch provided some good accuracy, I noticed after 1 year some .1mm change or +/- 0.15mm accuracy

So I invented a new switch / sensor using a slide, aluminum plate, hall effect transistor and a self made circuit board.

The accuracy is fantastic.

These are actual readings from 5 cycles with the same end mill.

  1. [PRB: --788.00, -1568.00, -132.720:1]
  2. [PRB: --788.00, -1568.00, -132.720:1]
  3. [PRB: --788.00, -1568.00, -132.720:1]
  4. [PRB: --788.00, -1568.00, -132.720:1]
  5. [PRB: --788.00, -1568.00, -132.720:1]

The last number -132.720 is that actual distance traveled from the home position on Z.

It shows that after homing Z at the top of the axis, it tripped the switch at exactly the same point.

Once the distance from that point to the top of the table is set, your all done. (This is explained in the previous video)

Step 1: The Switch

Bill of Materials, prices at time of publishing.

Deltron Linear Motion Slide 0.75" Travel 15 lb Load Capacity 1.56" Long - Amazon

10 pcs New A3144 A3144E OH3144E 3144 Hall Effect Sensor - Amazon - $6.49

uxcell 7Pcs 9 Pole 5mm Pitch PCB Mount Screw Terminal Block 8A 250V - Amazon - $7.63

E-Projects 4.7k Ohm Resistors, 1/4 Watt, 5% (Choose Quantity) - Quantity of 10 - $5.70

PCB - for wiring circuit. - Amazon 5.90 - Note - I made mine with my router.

Other Items -

3mm LED - RED

Referring to my old instructable will help with the g-code.

The assembly should be straightforward and remember that you should approach the switch slowly.

Step 2: PCB - DXF

Attached is the DXF file for the PCB of the switch.

I milled this board to make / solder the components to.

I did not upload a schematic as this is a very simple PCB.

Also left a 5mm hole for mounting to any extrusion.

Good luck and Keep making things.

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More by WPLaw:Z-Zero Switch Automated Z-Axis Zero on Tool Change with Shapeoko 2 or X-Carve. 
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