Overall equipment effectiveness (OEE)
Overall equipment effectiveness is essentially how available your equipment is, how it performs versus its spec and what kind of quality it produces. OEE can be used to monitor the efficiency of your manufacturing processes and to help identify areas of improvement. In practice, overall equipment effectiveness is calculated as the product of its three contributing factors:
Overall equipment effectiveness = availability x performance x quality
- Availability – The system is functioning when it is needed.
- Performance – A measure of system throughput divided by its maximum throughput.
- Quality – The number of good units divided by total units started.
Overall equipment effectiveness excludes planned shutdowns such as preventive maintenance, holiday shutdowns and periods when there are no orders to produce. When you subtract this planned downtime from total plant operating time, you are left with planned production time. OEE is calculated on planned production time. The ideal manufacturing facility, is one that produces the best product, as quickly as possible, with no unscheduled down time. This is an OEE of 100% which is difficult, if not impossible to achieve. For discrete manufacturing plants, world class OEE is generally considered being 85% or better, however, the average OEE score is ~60%.
What is OEE used for?
Overall equipment effectiveness is a good indicator of machine or system productivity. It can also give insights into the behaviours of personnel maintaining the system. A bad maintenance technician will spend the day running around putting our fires. They’ll fix the problem but they won’t prevent it from happening again. A good maintenance technician will perform regular inspections to spot failures before they occur, perform recurring scheduled maintenance and put in measures to prevent further failure reoccurrence; resulting in less machine-related downtime. OEE also provides a way of measuring the success of manufacturing, productivity or lean initiatives such as TPM.
When you identify the 3 different elements that make up overall equipment effectiveness, it is easier to identify where improvements are possible and where to put your focus. If availability is the focus, then you can run downtime reports in Maintenance Assistant CMMS and identify which issues are causing the majority of the system stoppages. In reality, OEE measures the losses that affect your equipment. The 6 big losses are:
- Equipment failures
- Setup and adjustment time due to product changeover
- Idling or minor stoppages – jams, misfeeds, sensor errors etc.
- Reduced speed due to rough running or equipment wear
- Defects in operation or process
- Startup or reduced yield
Edge ahead by measuring your OEE
In today’s fast-paced economy, manufacturing organizations need to find ways of creating a competitive advantage over their competition. Efficiency is one area that every manufacturing plant can improve on, and the best way to measure efficiency is with overall equipment effectiveness. If you don’t know your overall equipment effectiveness, then you don’t know how efficient your plant is. More importantly, you don’t know how efficient your plant could be.
You can calculate the availability element of the OEE equation using MA CMMS, but as you can see from the table above, maintenance activities can impact all 3 elements of OEE. A preventive maintenance solution, like Maintenance Assistant CMMS, is the ideal tool to track your schedule maintenance and inspections so issues can be identified before they turn into something more serious. According to David Berger of Plant Services, a CMMS could deliver a 10% increase in availability, a 5% increase in throughput and a 5% increase in quality of output. With a fully functioning CMMS, coupled with a preventive maintenance philosophy, these gains result in a significant improvement in OEE and hence the company financials.