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Tool Length Probing

This guide covers using a Tool Length Probe with the Probing Wizard to automatically calculate the length of an installed tool to determine and apply the tool offset needed to maintain the project Z axis zero point.

Using a probe to do this isn't strictly necessary for basic CNC work – you can manually re-zero your Z axis zero after changing a tool, but probing can perform that process automatically, and more quickly.

A tool length probe is especially helpful when a project's Z Axis Zero Point is set to Top and has been machined away during previous operations, and can aid in project recovery when the spindle, router, or tool has slipped and been re-secured, but potentially in a different position.

To follow this guide, you'll need a CNC machine with a tool length probe located within the travel area of the machine. The probes may be built into the machine or may need to be installed as a separate accessory. Refer to and follow your CNC manufacturer's instructions when installing a tool length probe.

How Tool Length Probing Works

Tool length probes vary in type, location, and material, but typically work the same: your CNC will jog/move the tool over the position of a probe in your CNC's work area, then lower the tool until it makes contact with the probe, sending a signal to the machine's controller to calculate and establish the new tool Z axis zero point.

Enabling the Tool Length Probe

Open Custom GCode Window

Open the Custom GCode window in the Device Settings window to define the parameters of your tool length probe by selecting either:

• CNC Tools → Device Settings → Custom GCode tab
• Main Toolbar → → Custom GCode tab

CNC Tools Menu

Main Toolbar

Toggle On Has Tool Length Probe

In the Custom GCode Options column on the right-hand side of the same Device Settings window, scroll down until the Tool Management section is visible and enable Has Tool Length Probe.

Save Changes

Click the OK button to save your changes and close the Device Settings window.

Setting Up a Tool Length Probe

Set the position and motion parameters of your tool probes in the Probe Configuration window. If you have already defined your probing settings, you can skip ahead to Start Tool Length Probing.

Warning

Make sure that before you start probing for tool length that the spindle or router collet is tight and the tool secure. The spindle or router must be off and not rotating.

1. Find the X and Y Axis Tool Length Probe Location

Use the Jogging controls in the Move Window to position the tool until it is centered directly over the Tool Length Probe location and note it's X and Y axis machine coordinates.

1. Close the Probing Wizard if open
2. Select the Move Window
3. Use the jogging buttons to move and roughly center the tool above the probe location
4. Note the machine X and Y Axis coordinates in the Move Window, labeled Tool Position (M)

2. Open Probe Configuration Window

Open the Probe Configuration window to define the parameters of your tool length probe by selecting either:

• CNC Tools → Probe Settings
• CNC Tools → Probing Wizard → Manage Probe Configuration → Tool Length Probe
• Move Tab → Probing → Manage Probe Configuration → Tool Length Probe

CNC Tools Menu

Move Tab/Window

3. Update Settings

Click in the image below to jump directly to information on that section, or scroll down for information on each option.

Position X and Position Y

Position X is the location in machine coordinates of the tool length probe along the X axis (left/right).

Position Y is the location in machine coordinates of the tool length probe along the Y axis (towards/away).

Search Z

Search Z is the maximum distance the tool will move downward when seeking the tool length probe. Set the Search Z distance to the length of the Z axis travel. Refer to your CNC manufacturer documentation for your machine's values.

Probing Recommendations

Faster probe speeds may lead to damaged tooling, probes, and may lead to CNC operator injuries.

Start probing slowly (200 mm/min or less) to ensure that accurate contact is made. Pay attention during the probing process to make sure that your machine responds instantaneously on contact and that deflection does not occur. If long probing times are encountered, faster probing speeds can be explored in 50 mm/min increments.

Go To Speed

• Enter the speed at which the tool will move to the Tool Length Probe.

Fast Probe Feed and Precise Probe Feed

• Fast Probe Feed is the initial speed at which the tool will search for the tool length probe, under 200 mm/min to start.
• Precise Probe Feed is the lower speed at which the tool will search for the probe after initial contact. This movement will be a very short distance and should be kept to a fairly low speed for accuracy.

Precise Probe Distance and Backoff Distance

• Precise probe distance is the distance the tool will slowly move towards the probing engagement point, set to 3.5 mm by default.
• Backoff distance is the length of movement the tool will slowly back away from the probing engagement point, set to 1.5 mm by default.

Z Lift Offset

By default, the Tool Length Probe Wizard will move the tool to the top of the Z axis until it reaches machine Z=0. The value entered in the Z Lift Offset field will become the new pre-probing destination/height of the tool before tool length probing.

4. Save Settings

Select OK to save the settings. Select Yes if prompted, to overwrite the previous Tool Length Probe Custom GCode entry in Device Settings. The Probe Settings window will close when saved.

Executing Tool Length Probing

Warning

Make sure that before you start probing for tool length that the spindle or router collet is tight and the tool secure. The spindle or router must be off and not rotating.

1. Ensure Spindle or Router is Powered Off

Always power off your CNC router or ensure that the spindle is not rotating before executing the probing process. An active spindle or router tool can damage the tool length probe, the tool, and machine and can lead to personal injury.

2. Install Desired Tool

Install the desired tool into the CNC router or spindle, ensuring that the collet has been tightened enough to securely hold the tool.

If the CNC router or tool is not securely installed, the Tool Length Probing process may fail or the tool may move, leading to inaccurate results.

3. Open Probing Wizard

Open the Probing Wizard by selecting CNC Tools → Probing Wizard, or by clicking the Probing button in the Move window.

CNC Tools Menu

Move Tab/Window

4. Select Tool Length Probe

Click on Tool Length Probe to open the Tool Length Probe window.

5. Start Tool Length Probing

PINCH DANGER

Keep fingers and hands away from the probing puck and/or tool during the probing process.

The CNC machine will keep moving the tool towards the puck or probe sensor until the machine is powered off, stopped by a hardware Emergency Stop, or successfully completes contact with the puck or probe.

Select Execute Tool Length Probe.

6. Monitor Probing Process

Once executed, the Probe Wizard will automatically:

1. Move the tool to the user-defined probe location along the X and Y axes using the Go To Speed
2. Home the Z Axis
3. Move the tool down the user-defined Search Z distance at the Fast probe feed speed on the Z axis until the probing switch or sensor is triggered
4. Move the tool up away from the probe
5. Approach the probe again, this time at the slower Precise probe feed speed until the probing switch or sensor is triggered
6. Set the new tool length and the new Z Axis zero point

7. Tool Length Probing Complete

You are now ready to run the operations in your project that use the tool you installed. Check the operations listed in the Operations window and turn on related operations that match your installed tool and turn off the remaining entries that do not match. Remember to run the Tool Length Probe again after each additional tool change within your project.

Related Topics

XYZ Probe Block

Place a machined block over the material stock or in a known position within the work area and set the Z Axis zero point.

Tool Length Probe

Establish tool length offsets when changing tooling in multi-operation jobs without changing the work Z axis zero point.

• Add Tabs
• Safety and Warnings
• Project Setup Wizard
• MillMage User Interface Guide

← Back to Probing Overview

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