OEE Calculation Errors

Database Errors

We agree that collecting and tracking OEE data is a task best suited for a database, however, all the bells and whistles of an OEE system don’t serve much purpose if the calculations are wrong.  Before you make a significant investment in your OEE data collection, tracking, and monitoring system, make sure the system you plan to purchase is calculating the OEE results correctly.

The ultimate system is one that supports automated data collection technology to minimize data entry costs, reduces the risk of entry errors, and provides reporting or monitoring of OEE in real time.  These solutions may be purchased “off the shelf” or customized to your specific process application.

Excel Spreadsheets

If a database is the best approach, you may ask why we use Excel spreadsheets to present our examples or why we supply templates to allow you to track and monitor OEE.  We have four primary reasons:

1. Almost everyone is familiar with spreadsheets and most people have access to them on their computer.
2. We determined that a customized database solution being used was not calculating the weighted OEE factors correctly and the overall OEE index was also wrong.  We found it necessary to develop a spreadsheet that made it easy to validate the database calculations.
3. Database enhancements were easier to develop and demonstrate using a spreadsheet.  We encountered a production process that was equipped with automated data collection capability and provided an overwhelming amount of performance data in real time.  It was easier to perform database queries and use the power of PIVOT tables to develop the desired solutions.
4. Spreadsheet templates allow you to start collecting and analyzing data immediately.  It also allows the users to get a “feel” for the data.  Although the graphs and drill downs offered by databases are based on predetermined rules, humans are still required to make sense of the data.

Recommendations

In summary, validate the software and its capabilities prior to purchase.  We have observed installations where the OEE data is used to monitor current production performance and the reports generated by the system are used to support the results – good or bad.

We have also evaluated a number of other free OEE spreadsheet offerings on the web and observed that some of these also fail to correctly calculate OEE where multiple machines or part numbers are concerned.  Take a look at our free spreadsheets offerings (see the sidebar).  Our tutorial provides an in depth explanation of how to calculate OEE for single and multiple machines or parts.

The purpose of measuring OEE is to ensure sustained performance with the objective to continually improve over time.  Don’t fall into the trap of setting up a system that, once installed, will only be used to generate reports to justify the current results.

Take the time to train your team and demonstrate how the results will be used to improve their processes.  Involve all of your employees from the very beginning, including the system selection process, so they understand the intent and can provide feedback for what may be meaningful to them while, in turn, they can support the company’s goals and objectives.

Reference Posts.

We encourage you to visit our previous posts showing how to calculate OEE for multiple parts and machines.

1. Single Process – Multiple Shifts:  OEE

2. Multiple Parts / Processes:  OEE

3. Practical OEE

4. Weighted Calculations:  OEE

5. How to Calculate OEE

6. Overall Equipment Efficiency

If you have any questions, comments, or wish to suggest a topic for a future post, please forward an e-mail to leanexecution@gmail.com

We appreciate your feedback.

Until next time – STAY Lean!