Study on operational reliability of tool magazine and automatic tool changer based on tool-pulling force

A tool magazine and automatic tool changer (ATC) is used to store and change tools in a machining center, which plays an important role in automatic manufacturing. Therefore, the stability and reliability of a tool magazine and ATC are very important to a machining center. Failures of a tool magazine and ATC would increase the maintenance time and repair cost. So the operational reliability for a tool magazine and ATC becomes a hotspot research. The tool-pulling force of a tool magazine and ATC would be obvious when the tool changing arm draws a tool holder out of a tool pocket and the tool-pulling force can reflect the degree of the lock springs failure which is one of the main reason for tool falling failure. To calculate the operational reliability of springs in the ATC and get ATC running status, the mathematical models between tool-pulling force and parameters of springs are built. Then, tool-pulling force test is conducted by using a special device and the test data are fitted by the linear equation. According to the correspondence between the mathematical models and coefficients of the linear fitting, the loading of springs is obtained. Then, the operational reliability of the single spring is calculated by the stress strength interference model and the operational reliability of springs set is calculated by reliability calculation method of series system.