How Understanding the Six Big Losses in Manufacturing Improves OEE
OEE is an acronym which stands for Overall Equipment Effectiveness. It is a metric widely used as a KPI which helps to determine how often equipment is available for work, how well the equipment does when it’s running, and how many products the equipment produce per cycle. OEE is calculated as the product of availability, performance, and quality. It is a model having its roots in total productive maintenance (TPM), and serving as a useful framework for improving manufacturing operations and achieving greater efficiency on the shop floor.
So, when trying to improve OEE score, the focus should be on eliminating waste. These wastes results in losses of OEE which compromise availability, performance, and quality and, they are collectively referred to as the Six Big Losses of OEE.
Improving overall equipment effectiveness (OEE) can easily be done by eliminating the Six Big Losses. These losses factors in and negatively affect the OEE calculation in the following ways:
- Availability: In this, we have breakdowns (unplanned stops) and setup & adjustments (planned stops).
- Performance: Here, we have idling and minor stops (small stops) + reduced speed (slow cycles).
- Quality: In this, we have defects (production rejects) + reduced yield (startup rejects).
The Big Losses of OEE and How to prevent them
The following details the Six Big Losses of OEE and key ways to avoid them.
Breakdowns
Breakdowns are mechanical failures that usually occur suddenly, making machines unavailable. This loss is the first big loss of OEE that has to be eliminated. The loss gives rise to all the other losses, in that, if the machine is not running, there won’t be such thing as performance or quality.
To prevent sudden breakdown of machine, endeavour to conduct regular preventive and predictive maintenance. Also, pay attention to trends in your past breakdowns through data analysis and then, figure out the root causes of those breakdowns. Once the root causes are determined you will better be able to implement lasting corrective actions.
Setup and Adjustment
Whenever there is a change in part or machine tooling, there’s a readjustment. The time taken to setup equipment for a new manufacturing operation leads to some form of losses. Setup and adjustments can be classified as planned stops. The impact of these losses can be diminished through several ways including the following:
- Create process standards,
- Strictly adhere to maintenance routines,
- Seek high-quality parts,
- Create work instructions in line with the manufacturer’s guidelines and strictly follow them, and
- Ensure compatibility of your equipment,
- For changeovers, implement a SMED (Single-Minute Exchange of Die) programme.
Idling/ Minor Stoppages
In this, production process is disrupted briefly. Examples of situations that can lead to idling or minor stoppages include: obstructed product flows, lack of raw material or tools, material jams, incorrect settings, blocked sensors, idle operators or a temporary malfunction etc.
While these stops last only for some few minutes and can be corrected easily by the operators, they still negatively affect cycle time, which is why they are considered a performance loss rather than an availability loss.
These chronic stoppages often happen on a frequent basis, however, with the help of new sensory technology and IIoT, they can now be easily tracked, thereby improving workflows, and eliminating the stoppages.
Speed
Losing speed also negatively affects cycle time and impacts performance. For instance, if the machine operates at a higher speed than the design speed, the machine could be experiencing mechanical problems such as jamming or the operators might be operating it incorrectly or even leading to production of defective products. This loss can be avoided by applying the following:
- Checking the machine speed
- Regular machine cleaning,
- Replacing worn-out equipment,
- Changing filters and maintaining lubrication as specified by the equipment manufacturers,
- Continuous operator training,
- Implementing autonomous maintenance etc.
Process defects and rework
Process defects refer to processes that result to the production of defective parts or products, while rework takes into account parts that can still be reworked to make the products useful. Defective products represent quality loss. The following are some of the possible causes of defects and rework:
- Poor operator skill level which leads to improper handling of equipment and operating them with incorrect settings.
- Ineffective maintenance of tooling or machines,
- Lack of raw materials or expired products etc.
Depending on what the actual root cause is, there may be need to implement further operator training or better stock management.
Startup losses (“yield losses”)
These losses occur when machines are warming up, and start to produce start-up waste. It may also be that newly installed equipment with the operators not yet familiar with how they are operated. These often lead to decrease in production output. While this is more common after changeovers, they can still happen after equipment startup. To avoid startup losses in OEE, the following can be implemented:
- Equipment Settings: Ensure you define and implement precise equipment settings, even if it’s on a part-by-part basis.
- Material Tests: It is recommended to run some few materials to tests on each piece of equipment to see if it is possible to minimize start-up problems.
About the Author
Adebayo is a thought leader in continuous process improvement and manufacturing excellence. He is a Certified Six Sigma Master Black Belt (CSSMBB), Digital Manufacturing Professional and ISO Management Systems Lead Auditor (ISO 9001, 45001 & ISO 22000) with strong experience leading various continuous improvement initiative in top manufacturing organizations.
You can reach him here.
