Identifying machine times with OPC UA for Equipment as a Service (EaaS)

With Equipment as a Service (EaaS), subscription-based business models are becoming increasingly popular in mechanical and plant engineering. The main argument in favor for EaaS is a better overall equipment effectiveness (OEE) when a factory supplier operates the equipment. Therefore, the constant determination of the OEE in EaaS operations becomes crucial. This value is usually determined combining data retrieved from the equipment itself in combination with data from higher level systems like the manufacturing execution system (MES) of the customers. The latter are not accessible by the factory supplier. To bridge this information gap, the OEE of a piece of equipment is determined based solely on the available equipment data retrieved through data exchange standards such as the Open Platform Communications Unified Architecture (OPC UA). To achieve this, the time information needed to determine the OEE as defined in the ISO 22400-2 standard is either directly determined from OPC UA data from the machines or approximated through assumptions and exclusions. As an example for the mapping of equipment data to different time information, machine tools are focused and, hence, OPC UA 40501 and OPC UA 40001. In addition, the findings are analyzed regarding limitations in using the available time data via OPC UA. The mapping’s applicability is demonstrated with an exemplary use case and the OEE is compared when calculated only with equipment data retrieved via OPC UA with the OEE calculation having the additional information from a higher level system. This comparison allows to evaluate the uncertainty introduced by making assumptions and exclusions. The resultsare a valuable input to supplement the OPC UA Companion Specifications in order to cover the OEE determination in EaaS use cases.