OEE Calculations

The OEE (Overall Equipment Effectiveness) percentage is calculated from three underlying metrics: OEE Availability, OEE Performance, and OEE Quality. These metrics indicate how closely a manufacturing unit performs relative to its designed capacity, with higher values indicating better performance.

All OEE metrics are calculated from values in traceability fields designated for Available Time, Scheduled Time, #Good Parts, #Total Parts, and Ideal Cycle Time. For more information, see Requirements for collecting OEE data.

Intermediate OEE statistics

These intermediate statistics are used to report Downtime and to calculate the primary metrics of OEE Availability, OEE Performance, OEE Quality, and OEE.

Where n is the number of data records that are grouped for analysis:

OEE Sum Available Time

OEE Sum Available Time =

Available Timen

Also commonly known as Operating Time, this indicates the total amount of time that the process was running.

It is the sum of all retrieved values in the Available Time traceability field. If all values are blank, or if the five traceability columns for OEE are not defined, this returns "NA".

OEE Sum Scheduled Time

OEE Sum Scheduled Time =

Scheduled Timen

This indicates the total amount of time that the process was scheduled to run.

It is the sum of all retrieved values in the Scheduled Time traceability field. If all values are blank, or if the five traceability columns for OEE are not defined, this returns "NA".

OEE Sum Downtime

OEE Sum Downtime =

Scheduled Timen

-

Available Timen

This indicates the total amount of time that the process was scheduled to run but not actually running.

It is the difference between all retrieved values in the Scheduled Time and Available Time traceability fields. If all Scheduled Time or Available Time traceability values are blank, or if the five traceability columns for OEE are not defined, this returns "NA".

OEE Sum (Good * Cycle Time)

OEE Sum (Good * Cycle Time) =

( #Good Partsn * Ideal Cycle Timen )

This indicates the amount of time theoretically needed to create the good (non-defective) parts produced, if the process were running at its ideal cycle time.

For every data record being analyzed, this calculates the product of the values in the #Good Parts and Ideal Cycle Time traceability fields, and then it calculates the sum of the products for all the data records being analyzed. If all #Good Parts or Ideal Cycle Time traceability values are blank, or if the five traceability columns for OEE are not defined, this returns "NA".

OEE Sum (Total * Cycle Time)

OEE Sum (Total * Cycle Time) =

( #Total Partsn * Ideal Cycle Timen )

This indicates the amount of time theoretically needed to create the total parts produced, if the process were running at its ideal cycle time.

For every data record being analyzed, this calculates the product of the values in the #Total Parts and Ideal Cycle Time traceability fields, and then it calculates the sum of the products for all the data records being analyzed. If all #Total Parts or Ideal Cycle Time traceability values are blank, or if the five traceability columns for OEE are not defined, this returns "NA".

OEE Metrics

Where n is the number of data records that are grouped for analysis, and with the intermediate statistics described above:

OEE Availability

Also commonly known as Uptime, this indicates the percentage of scheduled running time that the process was actually running.

It is the ratio of the OEE Sum Available Time to OEE Sum Scheduled Time. If either of these calculations is "NA", or if the five traceability columns for OEE are not defined, this returns "NA".

OEE Performance

Also commonly known as Speed or Process rate, this indicates the actual speed of the process as a percentage of its designed speed.

It is the ratio of the OEE Sum (Total * Cycle Time) to OEE Sum Available Time. If either of these calculations is "NA", or if the five traceability columns for OEE are not defined, this returns "NA".

OEE Quality

There are two methods for calculating OEE Quality. The configuration setting Take lost time into account when calculating OEE Quality in the System Administration module determines which method is used.

When the Take lost time into account... check box is selected (the default setting):

This is the ratio of the OEE Sum (Good * Cycle Time) to OEE Sum (Total * Cycle Time). If either of these calculations is "NA", or if the five traceability columns for OEE are not defined, this returns "NA".

This formula for OEE Quality represents the time spent producing good parts as a percentage of the total time spent producing all parts. (It uses the Ideal Cycle Time stored with the data to calculate the theoretical time spent producing good and bad parts, so any performance or availability issues do not affect this metric.) When rolling up OEE metrics across parts and processes with different Ideal Cycle Times, this formula is sensitive to those different cycle times.

When the Take lost time into account... check box is cleared:

OEE Quality =

#Good Partsn

/

#Total Partsn

This sums all retrieved values in the #Good Parts traceability field and those in the #Total Parts traceability field and calculates their ratio. If all #Good Parts or #Total Parts traceability values are blank, or if the five traceability columns for OEE are not defined, this returns "NA".

This formula for OEE Quality represents the Process Yield - good parts as a percentage of total parts produced. It is not sensitive to different Ideal Cycle Times across parts and processes.

Formula Comparison Example

You are analyzing OEE for a process that ran two different parts during a 10-hour shift.

• During the first five hours, Part type A produced 1,200 parts of which six were bad. The Ideal Cycle Time for Part type A is .25 minutes (four parts per minute).

• During the next five hours, Part type B produced five parts, of which one was bad. The Ideal Cycle time for Part type B is 60 minutes (one part per hour).

Taking into account the time lost producing bad parts:

NOT taking into account the time lost producing bad parts:

OEE

There are two methods for calculating OEE. The configuration setting Calculate OEE even if all three component values are not available in the System Administration module determines which method is used.

When the Calculate OEE even if all three component values are not available check box is selected (the default setting):

OEE is calculated as the product of OEE Availability, OEE Performance, and OEE Quality.

If OEE Availability, OEE Performance, or OEE Quality is reported as "NA", it is excluded from the calculation and OEE is calculated from the remaining metrics that are not "NA".

If all three metrics are reported as "NA", then OEE is also reported as "NA".

This method allows you to calculate OEE even if you cannot collect all five OEE data values.

When the Calculate OEE even if all three component values are not available check box is cleared:

OEE is calculated as the product of OEE Availability, OEE Performance, and OEE Quality.

If OEE Availability, OEE Performance, or OEE Quality is reported as "NA", then OEE is also reported as "NA".