How to calculate OEE – tutorial (xls)


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OEE is comprised of three factors:  Availability, Performance, and Quality.  While calculating these factors is fairly straightforward, it is important to recognize that a standard definition for OEE does not exist.  It is important to understand the assumptions you are making to make sure that you understand the final OEE result.

OEE measures how effectively TIME is used to produce a quality product.  We have established the following definitions of TIME to be used to calculate OEE:

1. Scheduled Production Time or Planned Production Time

2. Planned Down Time:  Scheduled down time events

3. Unplanned Down Time:  Unscheduled down time events

4. NAT = Net Available Time (Scheduled Production Time - Planned Down Time)

5. NOT = Net Operating Time (Net Available Time - Unplanned Down Time)

6. IOT = Ideal Operating Time (Time to Produce All Parts at Rate)

7. LOT = Lost Operating Time Due to Production of Scrap or Non-Saleable Product.

Although we will provide examples of these calculations, the following formulas are used to calculate each of the OEE factors and overall OEE:

1. Availability % = NOT / NAT * 100

2. Performance % = IOT / NOT * 100

3. Quality = (1 - (LOT / IOT)) * 100  OR  Quality = (IOT - LOT) / IOT * 100

4. OEE = Availability * Performance * Quality

You will notice that a quick way to check your OEE result is to calculate the time required to make good parts divided by the Net Available Time: OEE = (IOT - LOT) / NAT

Calculating OEE:  A real life example

An 8 hour shift is scheduled to produce three parts as shown in the schedule below.  The shift has two 10 minute breaks and a 5 minute clean up period.Production Schedule:

M/C:  A   Part #:  A123, Cycle:  10 (seconds), Produced:  2240, SCRAP:  50, Unplanned Downtime:  32 minutes

M/C:  B   Part #:  B456, Cycle:  45 (seconds), Produced:  450, SCRAP:  25, Unplanned Downtime:  18 minutes

M/C:  C   Part #:  C789, Cycle:  70 (seconds), Produced:  229, SCRAP:  11, Unplanned Downtime:  22 minutes

Calculating OEE

Calculating OEE starts by calculating the Net Available Time, Net Operating Time, Ideal Operating Team, and Lost Operating Time as shown in the table below.