OEE reverse calculation

Overall Equipment Efficiency (OEE) calculation with traditional and "academic" approach is long and fastidious. Scolar application often delays the first progresses, with a risk of demotivation for the actors!

The "academic" approach

The "academic" approach starts from shop total available time and substracts all non operational times, lost times while machine is stopped, but also the time spent producing bad parts. OEE is the ratio of the extrems: time spent producing OK parts divided by total available time.

Proceeding this maner to collect and compute all necessary data is long and fastidious. In fact, the "academic" approach is more a pedagogic approach to demonstrate how the available time is reduced by different factors, than an operational method.

Reverse OEE calculation

To calculate OEE quickly, the production results are enough:

• The number of OK units is counted or calculated by substraction of defective units from total of produced units.

• To determinate the total number of fabricable units supppose a given time period has been defined and cycle time per unit is known.

The same result should be met if expressed in time units:

Necessary data for these calculations are generaly available on shop floor. OEE is easily and quickly calculated if done reversely, starting from achieved production results.