CNC Knowledge: Tool change principle of machining center tool magazine

The biggest difference between machining centers and CNC mills is the tool magazine and its tool changing device. Common forms of machining center tool magazine include: disc type tool magazine, hat type tool magazine and chain type tool magazine. There are two ways to change tools in machining centers: robot tool change and spindle tool change. 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 from the tool magazine: sequential tool selection and arbitrary tool selection. The first is to install the tools required for processing in the tool holder in sequence according to a predetermined processing sequence when changing tools, in the tool magazine. is indexed in order, this method has simple tool magazine control and movement, but low 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.

Arbitrary tool magazine can be divided into fixed address tool change magazine and random address tool change 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 removed from the tool magazine will always 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 situation of loading the tool into the tool magazine, the T command in the machining program can be directly written according to the distribution of tools in the tool magazine. The hat type tool magazine mainly 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 configured with a tool table to store the relationship between the tool number tool 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 stored in the tool table. The tool selection command allows you to select the tool based on the tool holder number corresponding to the tool in the tool. table (note The tool selection command in the program always controls the tool number). Additionally, the operator can query the tool list at any time and edit and modify the tool list as necessary. Disc and chain tool magazines mainly use random address tool selection.

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

1) Run TxxM06 first, xx is the tool number to modify.

2) Manually install tool #xx onto the spindle.

Repeat above to continue loading the knife.

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

It should be noted that the tool magazine of a machining center is usually produced by a professional manufacturer. Its tool selection and tool changing methods and order formats depend on the design of the tool magazine manufacturer and the machine tool manufacturer. and the tool magazine’s tool changing methods shall be based on the machine tool manufacturer’s operating manual which shall take precedence.

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