Overall equipment effectiveness (OEE) is a calculated key figure that provides an indication of how effectively a system is working. How overall equipment effectiveness is calculated and what role digital solutions and data analysis play in this is explained below.
What is overall equipment effectiveness?
Overall equipment effectiveness can be used to measure the productivity of a system or machine. The key figure is crucial for evaluating the overall performance of a system and initiating optimization processes. The overall equipment effectiveness is specified with a value between 0 and 1 or 0 % and 100 %. Depending on the situation, different threshold values apply with regard to the evaluation of the OEE. In some areas, for example, an OEE of at least 90 % should be achieved, while in very complex production processes, for example, an OEE of 60 % is already considered convincing.
How is the overall system effectiveness calculated?
Three factors are used to calculate the overall system effectiveness: Availability, performance and quality. The formula for calculating the OEE is as follows:
Availability x performance x quality = overall effectiveness
It is crucial that the overall system effectiveness always allows a view of unplanned losses of a system. Planned downtimes and failures are not taken into account in the calculation. Therefore, the actual operating time of the system must first be calculated.
Operating time
To calculate the operating time of a system, the calendar time is used as the basis (365 days a year with 24 hours each). All planned system downtimes are deducted from the calendar time. This includes the hours in which the system is not manned (e.g. weekends/overnight), planned maintenance work, work breaks and any other types of planned downtime. The result is the operating or utilization time, which is used as the basis for calculating the overall system effectiveness at 100%. This value is practically never achieved in reality. All losses in terms of availability, performance and quality are deducted from it.
Availability
The availability parameter is the operating time reduced by all unplanned downtimes. This can include, for example, waiting times for maintenance and repair work as well as downtimes due to system malfunctions or power failures. In order to be able to calculate this factor correctly, it is necessary to define the period of time from which a standstill is actually considered a restriction in availability. In many cases, the value of one minute has become established. Downtimes of less than one minute are taken into account as a restriction in performance.
Performance
The performance parameter summarizes all losses due to production losses in the number of units, short downtimes (which are not taken into account in the availability factor) and idle times. It is important that this parameter is set in relation to the actual running time (operating time minus deductions for availability).
Quality
The quality parameter describes all losses incurred due to parts that are classified as defective or require reworking. The total number of all parts produced is reduced by the number of defective or reworked parts. As quality defects are not always detected at the plant where they occur, a pragmatic approach is recommended when using this factor to calculate overall plant effectiveness.
What is the benefit of calculating the overall system effectiveness?
The OEE enables an objective assessment of the performance of systems, both individually and with a view to the overall added value of a company. The OEE also shows where there is potential for optimization. In addition, the performance of a system can be evaluated over time. Once optimization measures have been implemented, the overall system effectiveness can be used to determine whether they have achieved the desired success.
What role do digital solutions play in overall system effectiveness?
Digital solutions play a role in data collection and evaluation in particular when it comes to calculating overall system effectiveness. Smart technologies collect all relevant data in real time and can also take over the evaluation if required. This not only saves a lot of time and effort, but also provides an up-to-date view of the overall system effectiveness at all times. Digital data collection and evaluation is particularly advantageous for complex systems. In addition, data analytics solutionsmake it possible to uncover optimization processes and thus increase productivity and quality while reducing resource consumption and costs.