What is OEE (Overall Equipment Effectiveness)?
→ OEE (Overall Equipment Effectiveness) is an index to judge production run in terms of machine (equipment) availability, production rate & quality rate of the product.→ For TPM (Total Productive Maintenance) and Lean Manufacturing programs, OEE is a key metric.
→ It is an important characteristic of capacity planning, material planning, and other resource planning.
→ OEE is also known as TEEP (Total effective equipment performance).
→ Overall Equipment Effectiveness is a Lean Manufacturing Tool.
Basics of OEE (Overall Equipment Effectiveness)
→ There are three parameters for OEE (Overall Equipment Effectiveness) monitoring- Availability
- Performance
- Quality
[1] Availability:
→ Availability shows the machine available duration for manufacturing.
→ In other words, for how much time our machine is available for manufacturing.
→ Availability takes into account of Breakdown Losses.
→ Downtime losses include events or incidents that lead to a stoppage of planned production for a considerable duration.
→ After removing, downtime we can get the operating duration of the machine.
➨ Examples of Downtime:
⇢ Equipment failure,
⇢ Material shortage,
⇢ Excess change over timing, etc...
[2] Performance:
→ Performance shows the excess time taken for manufacturing as compared to standard operating timing.
→ The performance takes into account of Speed Losses.
→ The Speed Losses includes any factor that leads to operating production with more cycle time than maximum permissible.
➨ Examples of performance losses:
⇢ Low speed of job loading/unloading,
⇢ Fatigue of the operator,
⇢ Excess cycle time in manual work, etc...
[3] Quality:
→ Quality shows the Good Quality of Product.
→ It takes into account the quality losses (loss due to the manufacturing of a bad part).
→ Quality loss can only be present due to the manufacturing of a defective part or non-conforming part.
➨ OEE Calculation is mentioned in the below picture.
Times and Losses Calculation in OEE:
→ Planned Shutdown – Not part of Overall Equipment Effectiveness Calculation.→ Break Down Loss - Operating timing to Planned Manufacturing timing ratio is called availability when a process runs without any stoppage there will be 100% availability.
→ Speed Loss – It is the ratio of net operating timing to total operating timing or it can be calculated by actual cycle time / ideal cycle time. When the process runs with maximum theoretical speed then performance will be 100%.
→ Quality Loss- it is the ratio of total good parts to a total part produced. When all produced parts are good then there will be 100% quality.
Example of OEE Calculation:
→ Let’s assume below data to understand Overall Equipment Effectiveness calculation→ Shift Duration = 8 Hours (480 Minutes)
→ Total Breaks = 55 Minutes
→ Break Down = 40 Minutes
→ Ideal Production Rate = 1 Part per Minute
→ Total Part Produced = 350
→ Rejected Parts = 4
➨ Planned Production duration = Total Available Time – Planned Breaks
= 480 Minutes – 55 Minutes
= 425 Minutes
➨ Actual Production duration = Planned Production duration – stops (breakdowns)
= 425 Minutes – 40 Minutes
= 385 Minutes
➨ Availability (A) = Actual Production Time/Planned Production Time
= 385/425 Minutes
= 0.905
➨ Actual Production Rate = Total Count/Total Run Timing
= 350/385
= 0.909
➨ Performance (P) = Actual Production Rate/Ideal Production Rate
= 0.909/1.0
= 0.909
➨ Quality (Q) = Good Parts/Total Parts Produced
= (350-4)/350
= 0.988
➨ OEE = Availability (A) x Performance (P) x Quality (Q)
= 0.905 x 0.909 x 0.988
= 0.812 ~ 81.2 %
Six Big Losses in OEE
- Breakdowns
- Setup and Adjustment
- Small Stops
- Reduced Speed
- Start-up Rejects
- Manufacturing Rejects
[1] Breakdowns:
→ The breakdown comes under the Category - Downtime Loss.→ Unplanned downtime elimination is critical.
→ Preventive maintenance is a key weapon to kill unnecessary breakdowns.
→ Root cause analysis can be done on severe breakdowns.
→ Timely validation of tools is also important in order to prevent unplanned downtime.
→ Prediction of an equipment failure is a key skill of engineering that helps a lot in the prevention of downtime.
➨ Examples of Breakdown Losses:
⇢ Tooling Failure,
⇢ Unplanned Maintenance,
⇢ Equipment Failure,
⇢ General Breakdowns, etc...
[2] Setup and Adjustment:
→ Setup and Adjustment come under the Category - Downtime Loss.→ It is generally called duration between the last good part produced before setup change and the first good part produced after the changeover.
→ Tracking of adjustment timing is very important in reducing this loss.
→ We can use the concept of SMED (Single Minute Exchange of Dies) for reducing the Setup and Adjustment timing.
➨ Examples of Setup and Adjustment:
⇢ Excess setup/change over timing,
⇢ Material shortage,
⇢ Operator shortage,
⇢ warm-up timing, etc...
[3] Small Stops:
→ Small Stops comes under the Category - Speed Loss.→ Recording of this type of loss is very difficult.
→ Cycle time analysis to be used to identify this type of loss.
→ Activity wise actual-time monitoring and micro-mapping of this data help in the identification of small stops and speed reduction.
➨Examples of Small Stops:
⇢ Component jam,
⇢ Sensor blocked,
⇢ Delivery blocked,
⇢ Cleaning and Checking, etc...
[4] Reduced Speed:
→ Reduced Speed comes under the Category - Speed Loss→ Recording of Reduced Speed losses is very difficult.
→ It can be recorded by Cycle time analysis.
➨ Examples of Reduced Speed:
⇢ Poor planning,
⇢ Machine wear and tear,
⇢ Operator inefficiency,
⇢ Under design capacity, etc...
[5] Start-up Rejects:
→ Start-up Reject comes under the Category - Quality Loss.→ “First Time Right” concept to be adopted during each startup of production.
→ Effective use of production start-up check sheet can eliminate start-up rejects.
→ The process parameter setting plays a vital role in the manufacturing of the good part at the first time.
➨ Examples of the Start-up Rejects:
⇢ Damage,
⇢ Scrap,
⇢ Rework,
⇢ Incorrect assembly, etc..
[6] Manufacturing Rejects:
→ Manufacturing Reject comes under the Category - Quality Loss→ It is related to the rejection during the manufacturing
➨ Examples of the manufacturing Rejects
⇢ Damage,
⇢ Scrap,
⇢ Rework,
⇢ Incorrect assembly, etc...
Benefits of OEE:
→ It helps us to set goals for improvement, and track the progress.→ Overall Equipment Effectiveness helps us to find inefficiencies in the operation process.
→ It Provides us a benchmark data for the new process setup.
→ Overall Equipment Effectiveness helps to track progress in eliminating waste from an operation process.
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