Finding Zero on the Z axis.

**KHK** · 12-13-2010, 10:12 AM

A few ideas;
Router first idea, make a fixture to hold a dial indicator.(HF #623 @ $11.99 or HF #93295 @ $28.99) Place the fixture on the CNC table for the torch height.
If the router bit is placed all the way into the router and the router is placed all the way into the CNC holder this could work. Make a chart for different bits.

Router second idea, make a fixture to hold a limit switch. The switch would have to be adjustable for different bits. Place the fixture on the CNC table for torch height.
Wire the switch into the Z limit on the CNCs PCB. If the router bit is placed all the way into the router and the router is placed all the way into the CNC holder this could work.
Make a chart for different bits so the switch can be pre set for the router and router bit. Instead of wiring into the Z limit you could use an Ohm meter to find the zero.

Router third idea, (this is what I do), I have a 2in x 2in piece of brass shim stock,(0.010) with a wire soldered to it. I place it on the work and connect that wire to a 12 volt battery.
Connect another wire to the router bit and have a 12 volt light bulb between the second wire and the unused battery connector. When the bit touches the shim stock you have a reference point. The problem with this is that if the router is driven down to hard the shim stock will dent. I have tried an Ohm meter instead of the battery and it is not to consistent, the battery is the best.

I use the third idea with the plasma cutter but don’t use the shim stock. You must be sure that the metal to cut is clean and the tip of the plasma torch is also clean.

**Gadget** · 12-13-2010, 02:37 PM

I have successfully added a probe to my CNC table (I'm using EMC2). One wire clips to the tool, the other is connected to the touch plate. I've added a couple of custom GUI buttons and the code needed for each button but have not been able to link the code to the buttons yet. However, I can manually add the GCode (copy and paste) and have the Z lower till it touches the probe plate (.250" thick plate) and stop. Then I touch off Z to .250.
If anyone is building a CNC table and wants to use the free EMC2 program I will be able to help with the initial setup as well as adding a probe.
Dan

**Gadget** · 12-13-2010, 07:11 PM

I have successfully programmed three custom buttons in EMC using the MDI commands.
The first button will lower Z to touch the tool to the touch plate and stop.
The second sets the Z offset to .250 (the thickness of the touch plate)
The third raises Z to 1"
Just put the touch plate on the work surface, put the tool over the plate and click, click, click you are done. I just have to remember to remove the probe before starting the router or plasma cutter. Yes it will work on the plasma cutter as well.
In the future I will write a CPL ladder to combine the three moves into one button click but for now this will work very well. This is really cool stuff.