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Z-axis Zeroing:

Accurately setting the Zero point of all the Axis' on your ShopBot is a requirement for cutting consistent parts, but it's particularly important for the Z-axis.

Testing the ZZero plate

ZZeroing Software

The ShopBot Control software includes a program to zero your Z-axis using contact with a metal plate. This program is named "ZZero.sbp" and is installed in the "C:\sbparts" folder. It can be called as a file using the FP command, run as a custom cut by typing "C2" or selecting it from the Custom menu. It can also be called from one of the buttons in the Control Software toolbar.


In the current Control software the settings for the ZZeroing routine are saved in a file named "my_variables.sbc" that can be found in the "C:\sbparts\custom" folder. It can be edited manually using the ShopBot Editor or any text editor, or by running the ShopBot Setup Virtual Tool "TS".

ZZeroing Hardware Connections

Zeroing the Z-axis only requires a contact plate that is connected to one of the input switches, and a good ground connection with the bit or cutter. Usually a flat piece of aluminum is used as the contact plate, but a piece of printed circuit board or any other electrically-conductive material will work. One end of a thin wire is connected to the plate and the other end of the wire is connected to one of the input switch connections. By default input switch #1 is used, but if there's a conflict you can connect it to any other input switch IF you follow these rules:

  • The emergency stop switch uses input #4..that can't be used by anything other than emergency circuits
  • If you have a PRS tool, the proximity switches use inputs #2 and #3 so you can use inputs 1,5,6,7, or 8
  • If you have an earlier tool, the proximity switches use input #3 so you can use inputs 1,2,5,6,7, or 8

'NOTE: If you change the input switch connection to something other than input #1, you MUST change the value for&my_ZzeroInputin your "C:\sbparts\custom\my_variables.sbc" file from&my_ZzeroInput = 1to the new input switch number.'

Testing the ZZero Plate

The other part of the zeroing connection is the ground connection running through the bit, completing the input switch circuit. Generally this connection is good but it runs through your router or spindle' bearings so there's the potential for a poor connection. Always test the connection before running a Zeroing program by touching the plate to the bit

Testing the ZZero plate
Testing the ZZero plate

and making sure that the indicator light on the correct input switch (#1 by default) turns on when contact is made.

The #1 Input switch indicator
The #1 Input switch indicator

If not, an alligator clip with a wire connected to a good ground on the tool's frame can be clipped to the bit for a more direct connection.

Running the ZZero program

Once you're sure that your ZZero plate is working the way it's supposed to it's time to use it. Put the Z-zero plate on either your material or the table top, depending on how the file was created, so that the plate is under the bit in your router or spindle.

ZZero plate under bit
ZZero plate under bit

Start the Zzero program using one of the methods listed above and the bit will move downward until it contacts the plate. Once contact has been made, the bit will lift and then descend again at a slower speed to make contact again....don't remove the Z-zero plate until this contact has been made.

Bit contacting ZZero plate
Bit contacting ZZero plate

After this second contact, the bit lifts once again and the Z axis zero point is reset...you're ready to cut!

Watch a video of the process

External References

ShopBot Training/Tutorial Video

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