Several parties, such as production teams, line managers and top management may have a different scope when looking at ‘effectiveness’. Being aware of those differences, it is possible to calculate different indices representing those different scopes; all based upon the same data. In the literature we find several attempts to do so, unfortunately they are not always consistent.
Although this definition goes beyond the scope of OEE, it is necessary to have a clear picture on this issue since it determines how to define certain categories within the OEE.
|3.2||Brief description of different scopes
OEE Solitaire is only applicable in situations where the monitored equipment has a technical link to other equipment/processes. Thus the equipment is an integrated part of a line. The effectiveness of such equipment is partially depending on factors like line balance and effectiveness of other equipment. ‘No Input’ (input buffer empty) and ‘No Output’ (Output buffer full) are the exponents of such influences. In certain case i.e. with huge installations in process industry parties may want to know the effectiveness of the equipment independently from the rest of the process. In other words; What would be the effectiveness of the equipment when it was running solitaire, with no restraints from the rest of the line?
For this purpose, an OEE can be calculated excluding ‘No Input’ and ‘No Output’ thus showing the effectiveness purely focussed on the equipment independent from the line. Calculating the OEE Solitaire takes Line restraint time (normally considered to be (I) Idle time) out of the loading time (so it is considered as Unscheduled time (-) ).
Caution: ‘No Input’/’No Output’ should not be confused with for example ‘no raw material’ or ‘no packaging’ since these have an other cause; they are not Line Restraints!
OEE is the default scope for a production team. It shows the ratio between the theoretical maximum good output during the loading time vs the actual good output. The loading time can be less then the operations time since the equipment can be unscheduled during the operations time, thus reducing the loading time. Loading time therefore is the time the equipment was supposed to be running.
In cases where several products have been produced, (either sequential or parallel) the Performance part of the OEE is calculated as a weighted average between the several expected output ranges.
OEE Top is equal to OEE except for the way the performance rate is calculated. In OEE Top the performance rate is calculated based upon the Name Plate capacity of the equipment; thus ignoring restraints due to the product-machine combination. It is used to detect effectiveness losses due to the chosen product mix.
Operations effectiveness goes beyond the scope of the production team (Maintenance – Operator – Engineer). It includes the operations time the equipment is not available to the production team or operations management does not want or can not schedule the equipment. Examples are [No Orders], [Legal Restrictions] like energy contracts and mandatory holidays and test runs for R&D.
The percentage of the total (calendar) time that the equipment runs.
|3.2.6||Net Utilization (=TEEP)||
Net utilisation reflects the ultimate improvement potential; it is the ratio between the total (calendar) time and the actual effective production time (or, if you wish; the theoretical maximum amount of good product versus the actual amount of good product coming out during that time). In some publications you may find the same definition named TEEP; Total Effective Equipment Performance.
|3.2.7||Capacity Utilization (=Gross Utilization)||
Capacity Utilisation reflects the ratio between the total (calendar) time and the loading time. It shows the hidden operations potential i.e. the difference between 3 and 4 shifts.