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Guide To Automatic Tool Changing

Using an automatic tool changer (ATC) greatly increases efficiency, especially in extensive projects that may require switching tools dozens of times.

Automatic tool change

Techniques to minimise tool changing time can save both work-hours and reduce the MTBB (mean time to breakdown) due to efficiency gains. The ATC attaches to the CNC system and allows tool changes to proceed automatically, but it is possible to make the use of ATC’s even more efficient by following the simple tricks explained below.

Programming Instructions Explained

  • M06 – Tool change command. Exchanges the tool in the spindle with the tool in the ready position.
  • T word – Tool control function. Rotates the tool storage device to bring a tool into the ready position.
  • M19 – Spindle orientation command. Rotates the spindle to align the key in the tool changer arm with the key way in the tool holder.

Machining centres may use their own terminology but the programming instructions themselves remain the same between systems.

Note the Tool Change Position

Machine tool builders differ in specification to where the machine must be sent during a tool change. Tool changing time can be reduced by being aware of the tool change position and keeping it as close as possible to the current work piece. It is important to reduce the distance between these two points as this will reduce the need for distant movements to reach the tool change position.

Prepare the Next Tool

You can save magazine rotation time by pre-preparing the next tool. Rotate the magazine while the previous tool is machining the work piece and the tool will be ready after the spindle tool has finished. This is accomplished simply by adding a T word to specify the tool number after each tool change.

Load Tools Sequentially

Selecting tools that are next to each other in the magazine can minimise cycle time under certain circumstances. This can be a useful time saver especially during short cutting operations.

Mark Timing During Automatic Operation

It is good practice to time the current cycle as inconsistency in cycle time can occur during automatic tool changing as the placement of tools in the magazines changes. The tools may be placed efficiently in the beginning yet going forward a few cycles you will find that the cycle time has changed due to positioning changes in the magazine. Recording the timing of each cycle ensures that the process runs as efficiently as possible.

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