Overall Equipment Effectiveness (OEE) is a performance measurement metric that plays a crucial role in evaluating equipment efficiency and productivity. By considering three key components — Availability, Performance, and Quality — OEE provides insights into the overall equipment performance.
How to calculate OEE
The formula for calculating Overall Equipment Effectiveness is as follows:
OEE = Availability × Performance × Quality
- Availability: Availability represents the amount of time that equipment is available for production. It is calculated by dividing the operating time of the equipment by the total scheduled time or planned production time. The formula for availability is:
Availability = (Operating Time – Downtime) / Operating Time
Operating Time refers to the total time that the equipment should have been in production, excluding any planned downtime such as scheduled maintenance.
Downtime includes any unplanned stoppages or equipment breakdowns that result in a loss of production time.
- Performance: Performance measures the speed and efficiency of the equipment during production. It takes into account factors such as speed losses, minor stoppages, and idling time. The formula for performance is:
Performance = (Ideal Cycle Time × Total Count) / Operating Time
Ideal Cycle Time refers to the theoretical time required to produce one unit of the product under optimal conditions.
Total Count represents the actual number of units produced during the operating time.
- Quality: Quality assesses the percentage of good-quality products produced by the equipment. It considers defects, rework, and scrap. The formula for quality is:
Quality = Good Count / Total Count
Good Count represents the number of units produced without defects or the need for rework.
Total Count represents the total number of units produced during the operating time.
By multiplying the availability, performance, and quality components, you can calculate the OEE, which provides an overall measure of equipment effectiveness and productivity.
It is important to note that each component of OEE should be expressed as a decimal or percentage before performing the multiplication. For example, if availability is expressed as a percentage, divide it by 100 to convert it to a decimal before performing the calculation.
Example of OEE calculation
Let’s calculate the Overall Equipment Effectiveness for a conveyor belt system. We will assume the following data for our example:
Availability:
- Operating Time: 720 minutes (12 hours)
- Downtime: 60 minutes (due to unplanned breakdown)
Availability = (Operating Time – Downtime) / Operating Time
Availability = (720 – 60) / 720
Availability = 660 / 720
Availability ≈ 0.9167 or 91.67%
Performance:
- Ideal Cycle Time: 1 minute (the time it should ideally take to move one unit along the conveyor)
- Total Count: 650 units produced during the operating time
Performance = (Ideal Cycle Time × Total Count) / Operating Time
Performance = (1 × 650) / 720
Performance = 650 / 720
Performance ≈ 0.9028 or 90.28%
Quality:
- Good Count: 625 units produced without defects or rework
- Total Count: 650 units produced during the operating time
Quality = Good Count / Total Count
Quality = 625 / 650
Quality ≈ 0.9615 or 96.15%
Now, let’s calculate the Overall Equipment Effectiveness (OEE) by multiplying the availability, performance, and quality:
OEE = Availability × Performance × Quality
OEE = 0.9167 × 0.9028 × 0.9615
OEE ≈ 0.7660 or 76.60%
In this example, the OEE for the conveyor belt system is approximately 76.60%. This means that the equipment is operating at about 76.60% of its maximum potential efficiency and productivity.
👷 See also: What are the Six Big Losses of OEE?
Best practices to improve OEE
To maximise OEE and enhance equipment efficiency, consider the following:
Address common causes of equipment inefficiency
Identify and eliminate root causes of downtime, breakdowns, and performance losses, by implementing preventive maintenance, improving changeover processes, and ensuring adequate operator training.
Maximise equipment availability and performance
Reduce unplanned downtime through proactive maintenance practices, improve scheduling and planning, and optimise changeover processes to minimise setup time.
Improve product quality
Implement quality control measures, provide operator training on quality standards, and continuously monitor and address defects to reduce rework and scrap.
Define realistic performance targets
Set achievable performance targets based on historical data and industry benchmarks. Regularly measure and analyse performance against these targets to track progress and identify areas for improvement.
Monitor and analyse data
Collecting and analysing OEE data is crucial for measuring equipment performance and identifying improvement opportunities. Utilise data visualisation tools and software to track OEE metrics in real-time, generate reports, and visualise trends. Youcan then analyse the data to identify bottlenecks, areas for improvement, and potential causes of equipment inefficiency.
