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 :
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.
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.
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
Availability = 75 %
Performance =90 %
Quality = 89 %,
OEE= 75 % * 89 % * 90%
= 60 %
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
Availability =Operating Time (300 min) / Planned Operating Time (400 min)
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
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
Hence, planned operating time is 480 -70 = 410 min
Actual Operating Time
Planned operating time – down time
=410 – 110
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
Availability = actual operating time / planned operating time
= 73 %
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
Quality is the ratio of good qty produced to total qty produced.
Total qty produced = 270 pieces
Good qty = 240 pieces
Quality = 240 / 270