Condition Monitoring of CNC Machining Center Performance Degradation Using a Machine Capability Index

Machining tools of manufacturing equipment is often called “mother machine” as they make machines that support industries. Therefore, there are numerous efforts to satisfy needs for high accuracy and durability. Major considerations involved in selecting a machining tool are productivity, flexibility, space, adaptability, precision, reliability, safety and environment, and maintenance and service [1]. Especially, capability [2,3] and reliability [4-5] are the most important requirements for high precision and reliable machining product. To assess the machine capability, machine capability index is used for measuring the quality characteristics of equipment’s processing products [7]. As for the reliability, statistical features based on failure database or condition monitored data is used [4-5]. However, capability and reliability are very closely related because reliability can be evaluated by the capacity of produced items to perform as required over specified time. But there are very few attempts to combine these properties [8]. Thus a new method is proposed in this paper to highlight the correlation between capability and reliability.