Manufacturing today is becoming steadily more competitive, and manufacturing businesses are always looking to improve the productivity — and the profitability — of their operations. As such, they must objectively understand whether improvement is occurring, or not. Often, this sort of self-assessment is based on quantitative measures.
There are various methods used across manufacturing industries to track operational efficacy. One of the most common ways to measure overall manufacturing performance is through Overall Equipment Effectiveness, or OEE. If used in the proper way, tracking OEE can give machine shops a good understanding of its manufacturing processes. Because it is an overall measure of a process, OEE can quickly shed light on an area of concern. It also can be used to compare lines across the shop floor, and ultimately optimize the entire production.
Most often, OEE is determined by a combination of these three metrics:
• Availability – is the line available to run, or is it down for maintenance?
• Performance – how quickly is the line producing? (think widgets per hour, etc.)
• Quality – how many defects are there? (think defective percentage of widgets.)
There are two ways to calculate OEE — simplified and advanced. The method you use likely depends on your operation and preferences.
A simplified method would be to multiply the number of good parts made by the ideal cycle time, and divide the total by the planned production time.
An advanced way to calculate OEE is by determining availability, performance, and quality; each separately as a percentage. Then, multiply the percentages by each other to come up with a single percentage number.
Let’s walk through a quick example to help illustrate the concept. Assume you are calculating OEE for one week of time in a 24/7 operation.
Quality: Of the 1,200 widgets produced last week, 100 contained defects on inspection. Thus, the quality percentage was 1,100 / 1,200 = 91.67%.
Multiplying all three metrics together results in one number: The OEE for the week, in this case. 94.05% * 75.95% * 91.67% = an overall equipment efficiency of 65.48%.
Improving OEE — As you can see, there are three main tracks to improving OEE: Increasing availability, performance, or quality. And the calculation of the OEE will inherently highlight the areas on which to focus.
How can condition monitoring be used to improve OEE? Well, directly and indirectly, it can positively impact all of the calculations outlined above:
• Increased availability, by reducing the number and length of unexpected machine breakdowns which cause unplanned downtime.
• Increased performance. Condition monitoring allows you to keep machines in peak operating condition — in other words, working at maximum output — by tracking machine health and deterioration levels.
• Increased product quality. Healthy machines that work as intended will produce fewer defects – and condition monitoring helps keep them operating that way.
Often, the greatest benefit to OEE is that it leads to improving availability. Downtime is typically one of the biggest costs in manufacturing. Many report the cost at $100,000 to $300,000 per hour, and some in excess of $1 million per hour!
If the line is down, it cannot produce any product. So, good quality products made at capacity is not a possibility. Therefore, we will focus on this area for the remainder of the article.
Condition monitoring — There are several strategies to reduce downtime, including equipment upgrades or regular preventive maintenance tasks. Recently, condition monitoring has become a leading option as cost and technology barriers have been lowered.
Condition-based maintenance (CBM) is the act of monitoring equipment via sensors to determine overall health, often with the use of models and software. By using sensors and other precise technology, you can find equipment problems much earlier and have a chance to respond. For example, a report in the UK estimated 53% of machine downtime is caused by “hidden internal faults.” CBM allows you to find these “hidden faults.”
Besides downtime reduction, condition monitoring provides several additional benefits:
• It lowers maintenance costs by fixing problems before they become catastrophic.
• It increases the life of your equipment by running it more efficiently.
• It helps to prioritize maintenance work by detecting and quantifying existing issues.
There are a great number of CBM techniques and tools at your disposal that cover a wide variety of different types of machines and components.
Starting a condition-monitoring program — In starting a CBM program, there are some general steps to follow. Here is a quick rundown:
1. Select the assets to monitor. Typically, these are assets critical to production and/or equipment that is difficult and expensive to repair or replace.
2. Identify failure modes. These are the ways that the equipment may see most common failures.
3. Select CBM monitoring. Set up the monitoring so that you will detect the failure modes previously determined.
4. Set alarm limits for sensors. Determine the level at which you want to take action. This may be a theoretical or empirical limit and may take some iteration.
5. Assess and adjust. As with any successful program, take the time to assess its effectiveness and adjust if necessary.
Key takeaways— Overall Equipment Effectiveness remains a key metric on today’s manufacturing floor. It is a quickly understandable number that can lead you to opportunities to improve your process.
One of the best ways to improve your OEE is by focusing on availability, which typically means reducing unplanned downtime. Condition Based Monitoring is a cost-effective way of reducing downtime, and the hurdles to implementation are lower than ever before. With a successful CBM program, your OEE will improve, and so will your profitability.
Bryan Christiansen is the founder and CEO at Limble CMMS — an easy-to-use mobile CMMS software that takes the stress and chaos out of maintenance by helping managers organize, automate, and streamline their maintenance operations.
