Overall Equipment Efficiency (OEE): Standardized Work
After you start collecting OEE data for your processes, you may notice significant variance between departments, shifts, and even employees performing the work. Of the many aspects that you will be inclined to investigate, standardized work should be one of them.
Making sure that all employees are executing a process or sequence of processes correctly and exactly the same way every time is the topic of standardized work. The OEE data may also direct you to review how the processes are being executed by some of the top performers to determine if they are truly demonstrating best practices or simply cutting corners.
Lean practices are founded on learning by observing. We cannot stress the importance of observing an operation to see first hand what opportunities for improvement (waste elimination) are available. OEE data is a compass that directs you where to look; however, the destination for improvements is the process, the very source from where the data originated.
Establishing Standard Cycle Times
One of the first questions we usually ask is, “How were the standard cycle times determined?” Was the standard based on best practices, quoted rates, time studies, name plate ratings, or published machine cycle times?
We recommend conducting an actual time study using a stop watch and calculating part to part (button to button) cycle times accordingly. We have used the stop watch capability of the BlackBerry many times. Results for lap times and total elapsed time are easily recorded and can be e-mailed as soon as the study is complete.
The sample size of course will depend on the actual rate of the machine and should be statistically relevant. One or two cycles is not sufficient for an effective time study.
For operator “controlled” processes, we recommend involving the employees who normally perform the work when conducting the time study. It doesn’t make sense to have the “office experts” run the equipment for a short burst to set a rate that cannot be sustained or is just simply unreasonable.
Many processes, those dependent on human effort or automation, are usually controlled by PLC’s that are also capable of providing the machine cycle time. At a minimum, we recommend validating these cycle times to at least satisfy yourself that these are part to part or “button to button” cycle times.
For automated operations, PLC’s can typically be relied upon to provide a reasonable cycle time. Without going to far into process design and development, you will need to understand the elements that control the process sequences. Some processes are driven by time controls (an event occurs after a period predetermined period of time) versus those that may be event-driven (an event occurs based on satisfying a dependent “sensor on-off” condition or similar “event signal” mechanism.
The real key to understanding the process being studied is to develop a flow chart clearly defining each of the process steps. It is of equal importance to observe the differences that may be occurring between employees performing the work. Either the instructions lack clarity or habits (good or bad) have been developed over time. Although templates exist to aid in the development of standardized work, don’t wait to find the right tool.
Using Video – Record it Live
We highly recommend using a video recorder to capture the process in action. With the technology available today, video is readily available and a very cost-effective method of documenting your processes. Video presents several advantages:
- Captures activities in real-time.
- Provides instant replay.
- Establish process or sequence event timing in real-time.
- Eliminates need for “stop watches” to capture multiple event timing.
- Can be used as a training aid for new employees to demonstrate “standardized work practices”.
- Can be used to develop “best practices”.
- Reduces or minimizes potential for time measurement error.
We have successfully used video to not only develop standardized work for production processes, but also for documenting and recording best practices for tool changes, set up, and checking or inspection procedures.
Standardized work eliminates any questions regarding the proper or correct way of performing the work required. Standardized work procedures allow additional development work to be completed “offline” without further disruption to the production process.
Of course, Standardized Operating / Work procedures are required to establish effective and meaningful value stream maps but even more importantly, they become an effective tool to understand the opportunity for variances in your OEE data, certainly where manual or “human” controlled operations are concerned.
It has been argued that OEE data in and of itself is not statistically relevant and we are inclined to agree with this statement. The simple reason is that the processes being measured are subject to significant internal and external variances or influences. Examples may include reduced volumes, product mix changes, tool change frequency, employee turnover, and economic conditions.
As mentioned in many of our posts, it is important to understand “WHAT and WHY” we are measuring. Understanding the results is more important than the result itself. A company looking to increase inventory turns may resort to smaller production runs and more frequent tool changes. This will reduce Availability and, in turn, will result in a lower OEE. The objective may then be to find a way to further reduce tool change times to “improve” the Availability.
The use of OEE data can vary in scope, ranging from part specific performance to plant wide operations. As the scope of measurement changes, so do the influences that impact the net result. So once again, we urge you to use caution when comparing data between personnel, shifts, departments, and production facilities. Typically, first or day shift operations have greater access to resources that are not available on the “off’ shifts.
Perhaps the greatest “external” influence on current manufacturing operations is the rapid collapse of the automotive industry in the midst of our current economic “melt down”. The changes in operating strategy to respond to this new crisis are bound to have an effect on OEE among other business metrics.
The ultimate purpose of Lean practices is to reduce or eliminate waste and doing so requires a rigorous “document and review” process . The ability to show evidence of current versus proposed practices will reduce or eliminate the roadblocks that may impede your continuous improvement objectives.
While the post is brief today, hopefully the message is helpful.
Until Next Time – STAY Lean!