How to Change Tool in CNC Machine

Tool magazine and the Automatic Tool Changer are the most commonly used parts in high-speed CNC vertical machining centers. When machining different materials, changing the machining processes, or the tool is damaged, the CNC cutting tool often needs to be replaced. How to change tool in CNC machine and how does the cycle work? Here we focus on these two problems and introduce some points.

How Does a CNC Tool Changer Work

When the CNC machine is running, there is a sensor on the tool changer carousel tells the machine that the tool changer is in its full reach retracted park position, if the sensor does is not true during any operations of the machine, you’ll get a fault in the machine, the tool changer is going to come forward and collide with the Z head, so when we are going to do a tool change, the spindle will move to the Z height for the tool change to happen and go through a spindle orientation. It needs to orientate the spindle so that the dogs are lined up with a slot in the tool changer so that when the tool changer comes in the clip, it will engage in the groove of the flange of the tool holder and the drive dog on the spindle will go inside of a little notch, then the tool holder will be retained inside the tool changer. Once we’re at the Z height and we’re orientated and the spindle is locked in its orientation position, then the machine will call for the tool changer to come in, when the tool changer comes in, there’s another limit switch that tells the machine controller that the tool changer is completely in the tool change position, so it waits for that limit switch to be made before it will continue on the cycle.

Once the tool changer is in the full change position, we’re going to release the drawbar to let go of the current tool, so when this happens you’ll see the tool change or carousel get pushed down just a little bit and that’s the drawbar completely releasing the tool. There’s a sensor on the drawbar piston to signal when the drawbar has fully released, the machine will not go on until that sensor is made. When that sensor is made then the z-axis will move up to the changing height, once we complete that move, then the signal will be sent to the carousel to rotate to the tool pocket, the next tool is in.

When the spindle comes all the way down again, you’ll see that it pre-loads the carousel just a little bit while the spindle seats completely on the next tool and then once that Z move is complete then the drawbar will release, and then the machine will know that it has the next tool firmly held in the spindle and then it will call for the tool changer to retract and then they will wait to form the tool changer to fully retract and that retract park limits which to be made, so the machine knows that the tool changer is completely out of the way, after that the tool change cycle is complete, the orientation mechanism that locks the spindle and its orientation for the tool change will then release, we can go on to CNC machining.

In CNC programming, the tool change code is M06, which is the M-Code used to activate the automatic tool change along which T number called on the program. When the controller reads the T number with M06, it will search the tool magazine for the T number specified and rotates, then brings the tool into the spindle. Many lathes don’t use M06 because the T address itself indexes the turret.

Tool Change Procedure - Steps for Tool Changing

What is Tool Offset? Tool offsets are the set of values that move the center point of the cutter to the correct position for cutting the part using a specific tool.

1. Homing

2. Measure tool offset with fixed tool sensor

3. Set current X, Y offset

4. Measure current Z offset with movable sensor

5. Start spindle and begin cutting

6. Pause to turn off the spindle

7. Pause to change tool

8. Measure the second tool offset

9. Pause to turn on the spindle

10. Turn off spindle when cutting is completed