Our Guest Post today comes from Prof. Phillip S. Coles at Lehigh U.’s Dept. of Decision and Technology Analytics.
The Plan, Do, Check, Act (PDCA) Cycle, also known as the Deming Wheel, is an important tool in Kaizen, or continuous improvement. (It is discussed in Ch. 6 of your Heizer/Render/Munson text). In Plan we search for process problems and/or possible improvements and establish objectives. In Do we execute the improvement on a small scale and collect performance data. The results are assessed in Check, and finally we Act by adopting the change, if approved, or if it fails, abandon it and analyze the failure. We start over by returning to Plan to again improve the process. We continue turning the wheel in an endless cycle of continuous improvement.
The PDCA cycle is enhanced when used in conjunction with the Standardize, Do, Check, Act (SDCA) Cycle because a process cannot be improved without a thorough understanding of the process. Without standardization, if there are 100 people doing a particular job, there are most likely 100 ways the job is being done. Standardization establishes a baseline and ensures everyone is doing the job in the best way possible – the present state of the art.
Standardize the best way the process is currently being done. Do implement the standard operating procedure. Check to make sure everyone is doing the same thing and finally Act by correcting any deviations from the standard. Standardization removes variability, the enemy of quality, and the process can more easily be improved. Hence, why standardization is the base of the Toyota Production System, the topic of Ch. 16 of your text.
Once we have gone through the SDCA Cycle, we can move to the PDCA Cycle and improve the process. However, even though the process has been improved, because people are not accustomed to the new standard operating procedure, variability is increased. Therefore, we return to the SDCA Cycle to wring out variation through standardization and return stability to the process – then alternate the SDCA and PDCA Cycles in perpetuity.
If the PDCA Cycle is used exclusively, there will be increased variation between each turn of the Deming Wheel from the inevitable process drift. In this case the process would be improved, but between turns, as the process degrades, each successive improvement would be from a lower base. Standardization prevents process degradation. By using the SDCA and PDCA in combination, there is both stability and improvement, and progress is optimized.