The biggest difference between machining centers and CNC milling machines is the tool magazine and its tool changing device. Common forms of machining center tool magazines include: disc-type tool magazine, hat-type tool magazine and chain-type tool magazine. There are two ways of tool changing in machining centers: robot tool changing and spindle tool changing. Disc-type tool magazines and chain-type tool magazines generally use robots to change tools, while hat-type tool magazines generally use spindle tool changes.

There are two ways to select tools in the tool magazine: sequential tool selection and arbitrary tool selection. The former is to install the tools required for processing in the tool holder in sequence according to a predetermined processing sequence. When changing tools, the tool magazine is indexed in sequence. , this method has simple control and tool magazine movement, but poor flexibility, and has not been commonly used in recent years. The latter mainly codes the tool holder in the tool magazine, and the CNC machine tool selects the tool according to the coded address. This method is widely used.

     The arbitrary tool magazine can be divided into fixed address tool changing magazine and random address tool changing magazine according to different tool coding methods. The tool storage position in the fixed address tool magazine is the same as the tool holder number and is fixed. The tool taken out from the tool magazine will still return to the original tool holder after use. The tool number and tool holder number are always consistent. The operator can know the tool magazine at any time. According to the tool loading situation in the tool magazine, the T command in the processing program can be directly written according to the distribution of the tools in the tool magazine. The hat-type tool magazine mostly adopts the fixed address tool selection method. The tool number and tool seat number of the tool are stored in the random address tool magazine, so the system is set up with a tool table to store the relationship between the tool number and the corresponding tool seat number. After each tool change action, the relationship between the tool number and the tool holder number changes, but this change is memorized in the tool table. The tool selection command can select the tool according to the tool holder number corresponding to the tool in the tool table (note The tool selection command in the program still commands the tool number). In addition, the operator can query the tool list at any time and edit and modify the tool list when necessary. Disc-type and chain-type tool magazines mostly use random address tool selection.

     The hat-type tool magazine is generally small, and the tools can be directly loaded into the corresponding tool holders in the tool magazine by hand. However, most of the tools in the tool magazine are loaded manually with the help of the spindle, and then loaded into the tool magazine through the tool change command. The knife installation operation is as follows:

1) Execute TxxM06 first, x x is the tool number to be changed.

2) Manually install knives number x onto the spindle.

     Repeat the above operation to continue loading the knife.

     The tool changing process of a machining center generally includes two actions - tool selection and tool change, which respectively correspond to the tool code command Tx segment is completed, the latter can improve work efficiency.

     It should be noted that the tool magazine of a machining center is generally produced by a professional manufacturer, and its tool selection and tool changing methods and command formats depend on the design of the tool magazine manufacturer and the machine tool manufacturer. Therefore, the tool selection and tool changing methods of the tool magazine must be based on The machine tool manufacturer's operating manual shall prevail.

     The tool change position of the machining center is generally relatively fixed. For example, it is set at the reference point position of the Z axis (returned with the G28 command), and there are also specially set positions (generally returned with the G30 command).