The OEE - the king indicator among the production ratios
One of these metrics is Overall Equipment Effectiveness (OEE), which is an important basis for continuous improvement and adjustment of production. It thus forms a central pillar for Industry 4.0.
Especially in the course of digitization, OEE can be determined more precisely and the causes of production losses can be traced better. Nowadays, machines are equipped with an increasing number of sensors, which thus reveal a better picture of the process flow. By collecting and analyzing large amounts of data, many correlations can be developed.
What is the OEE?
OEE, or overall equipment effectiveness, provides any company with a quick and transparent insight into the productivity of a machine. In this way, optimization potentials can be uncovered and appropriate measures can be taken. The focus is on increasing productivity, reducing waste of resources and increasing product quality.
The OEE value is essentially made up of three factors: Availability, performance and quality. The value range is between 0% and 100%. The higher the value, the more effective the production process. The formula is therefore:
OEE = Availability x Performance x Quality
Factors and causes of loss of OEE
OEE is also a key indicator of Total Productive Maintenance (TMP). In the TPM concept, six influencing variables are defined, which turn out to be the main problems at the production facilities. These are referred to in the literature as the six major sources of loss that significantly affect the effectiveness of production facilities.
For the respective factors of the OEE ratio, the losses have different reasons. Availability expresses the ratio between actual and theoretically possible production time and thus measures losses caused by unplanned downtime. This thus provides information on how often a plant is available for production. Downtimes can occur, for example, due to malfunctions, set-up and adjustment times.
Power considers the losses that occur due to reduced output of a plant. The theoretically possible output of a plant is usually higher than the actual output quantity, since the plant cannot run continuously at the highest speed. These performance losses can be attributed to longer production cycles, reduced speed, idling or short stoppages, also called microstops.
Downtimes that are below a predefined limit - for example, below five minutes - are assigned to power losses. Prolonged downtime is associated with availability.
The quality factor puts the achieved yield in relation to the actual total quantity, which is reduced by start-up losses, rejects and rework.
The relationship between the types of loss
The theoretically possible production time is provided as the starting point for considering the OEE at the machine - 100% OEE. This results from the available time minus the time in which no production of a machine is scheduled. The other periods result when the corresponding periods of loss are deducted. The resulting net productive time is related to the theoretically possible production time. In the figure, the respective periods of the OEE calculation are listed in staircase form.
The OEE as the most important key figure in production
The OEE represents the most important key figure for production companies. By determining the individual OEE factors, priorities can be set to make production efficient. OEE can thus make a significant contribution to optimizing production and increasing productivity for a company by specifically analyzing plant losses and deriving appropriate measures. For this reason, it is all the more important to deal with the decisive key figures for store floor management.