Overall Equipment Effectiveness ( OEE) -Introduction

What is OEE?

Overall Equipment Effectiveness (OEE) is one of the best METRICs used for monitoring and improving the Efficiency of manufacturing processes.

The manufacturing processes can be machining, fabrication, assembly line etc

OEE is a simple, holistic, and powerful metric.

OEE takes into account the typical sources of manufacturing productivity losses and groups them in THREE categories like AVAILABILITY, PERFORMANCE, and QUALITY. By grouping so in different categories, it distills the complex manufacturing losses into simple metrics .It helps us to understand the losses with clarity and helps to choose the right lean tool for each loss. In addition, it helps us to verify the effectiveness of action against each manufacturing productivity losses

 Elements of OEE :

Availability:

It measures manufacturing productivity losses from down time .i.e. the events that stops planned production like machine breakdown, changeover, material not available, operator not available etc.

Performance:

It measures manufacturing productivity losses from slow cycles .i.e. the factors that cause the process to operate at less than the standard or possible speed.

Quality:

It measures manufacturing productivity loss from manufactured parts do not meet the specification or quality requirements.

Together all three measure like Availability, Performance and Quality combine into one FACTOR as OEE

Score .This one complete measure OEE reflects the manufacturing efficiency and effectiveness.

OEE provides simple, consistent, and proven way of measuring the effectiveness of any productivity initiatives or lean manufacturing programmes or TPM programmes

World class OEE for discrete manufacturing process

Generally, world class OEE for discrete manufacturing process is considered 85 % or greater than 85 %

It is arrived from Availability (90 %) * Performance (95%) * Quality (100 %) = 85 %

Generally, from the study, it is indicated that average OEE score for discrete manufacturing process is around 60 %.If we aim for excellent OEE standard of 85 %, then we can realize that there is so much opportunity to move from 60 % to 85 % through loss elimination or reduction initiatives.

  

Calculating OEE :

OEE is calculated from three categories like availability, performance, and quality

OEE = Availability * Performance * Quality

Pl note that OEE is not calculated as addition or average of three categories, it is calculated by multiplying three categories

For example

Availability = 75 %

Performance =90 %

Quality = 89 %,

Then

OEE= 75 % * 89 % * 90%

       = 60 %

Availability:

Availability is the ratio of actual operating time to planned operating time ….

It measures the downtime loss

Availability = Operating Time / Planned Operating Time

Operating time = planned operating time – downtime loss

For example

Availability =Operating Time (300 min) / Planned Operating Time (400 min)

                   =75 %

Planned Operating time:

Available time per shift – planned shutdown time

Available time per shift

Say 8 hrs i.e. 8 * 60 = 480 min

Planned shutdown time

It is planned shutdown for valid reasons like morning meetings, lunch break; refresh break, scheduled maintenance check etc

For example

Morning meeting – 10 min

Lunch break – 30 min

Refresh break – 20 min

Scheduled maintenance check – 10 min

Hence planned shutdown time = 10 + 30+20+ 10

                                                       =70 min

Hence, planned operating time is 480 -70 = 410 min

Actual Operating Time

Planned operating time – down time

=410 – 110

=300 min

Break up  of down time (110 min ) can be

Machine breakdown -20 min

Operator not available – 30 min

Material not available – 10 min

Changeover loss – 50 min

Hence,

Availability = actual operating time / planned operating time

                   =300/ 410

                  = 73 %

Performance:

Performance is the ratio of actual qty produced during operating time / standard qty can be produced during operating time.

From above example,

Actual operating time = 300 min

Say std time per piece = 3 min

So standard qty can be produced during operating time = 300/3 =100 pieces

Suppose, in a given operating time, actual qty produced is 270 pieces, then

Performance = 270 / 300

                       =90 %

Quality:

Quality is the ratio of good qty produced to total qty produced.

For example,

Total qty produced = 270 pieces

Good qty = 240 pieces

Quality = 240 / 270

             =89 %