Understanding Overall Equipment Effectiveness
The following blog post was submitted by 2016 Continuous Improvement Conference sponosor, Heidelberg.
What is OEE?
When optimizing your production, Overall Equipment Effectiveness (OEE) provides a valuable independent measure of how well a piece of equipment performs over time. It also helps gauge the impact of changes to workflow and production methods. There are several ways to define this, but for the purposes of this blog, I have used the definition we use (at Heidelberg) of OEE as:
OEE = Speed Index × Quality Index × Time Index
Quality Index = Total of all good products
Total of all printed products
Speed Index = Average equipment speed
Maximum equipment speed
Speed Index = Total production time
Total available time
A typical OEE chart from the printing industry is shown in Figure 1 below. This figure illustrates the relationship between OEE and run length, with different equipment/facility combinations shown on the chart. Since there is typically a larger percentage of time spent on makeready, OEE will change as the run length reduces. There are many other factors that can move this value such as equipment type, configuration, controls, job make-up, and production efficiency. Understanding where the equipment is currently, versus where it can be, is critical to improving overall productivity. (The actual result will vary dependent on the industry.)
There are many steps that can be completed to achieve optimal equipment performance. Many of these changes are cultural and need to be embraced by management and recognized by all employees in the company.
- Training. Some operators do not fully utilize all of the available controls on the equipment, and many have never had formal training. Data has shown that operators need active training with hands-on situations, including the opportunity to get involved with training others.
- Additionally, a well-managed and repeatable color workflow will minimize any color changes that need to be adjusted on press.
- Finally, lean manufacturing tools can garner efficiencies, from 5S to value-stream mapping and Kaizen events.
In all of these, the objective is first to evaluate what the current state is and then to evaluate where the biggest impacts can be made. It also helps to obtain “buy in” from staff, who will personally see the benefit from these changes. On one implementation of 5S on a press, an operator objected, stating it was “just to make the press look nice!” Three weeks later, with an average of more than 10 minutes saved per makeready, the same operator was asking if 5S could be rolled out across the facility.
Obtaining the best OEE
To fully optimize your equipment and obtain the best OEE, a maintenance program should be the cornerstone of facility management. Equipment failure and downtime can greatly reduce OEE and lead to missed production deadlines and increased costs. The importance of a Total Productive Maintenance (TPM) program that identifies and fixes issues before they occur is critical to production and can lead to a significant reduction in repair costs.
By optimizing all of the steps in the production cycle and standardizing materials, very high efficiencies can be achieved. An example is shown in Figure 2, where 134 makereadies and 273,000 impressions were completed in 24 hours on a sheetfed press. This was achieved at a commercial print facility, ESP Color Hub, by having a clear focus on their position in the marketplace and optimizing the press, the consumables, and the operating procedures to deliver high quality prints to many satisfied customers.