Deming Circle (Shewhart): PDCA Cycle


One technique continuously used and spread more improvement is known as Deming Circle (or Deming Cycle). This is its most popular name, because W. Edwards Deming was responsible for massively spread through his work and the many system implementations successful management quality in which he participated, mainly in Japan and the United States. But the original idea is not yours. The method was proposed in the late ’30s by Walter A. Shewhart, the father of Statistical Quality Control, author admired by Deming. Deming and Shewhart then be fervent collaborators and friends (we recommend reading Post Deming in Japan).

The method, as stated by Deming at its summit work ‘Quality, Productivity and Competitiveness (Exit Crisis)’ 1986 is a procedure that seeks two objectives: to achieve improvement of any process, and “discover a special cause it has been detected by a statistical signal. ”

In this technique is also known as PDCA cycle, by the acronym of the four cyclic steps that comprise:
Plan (Plan)
Do (Make)
Check (Check)
Act (Act)
In Spanish-speaking countries it is common to call this PDSA method for its initials in Spanish. So even it appears on International Standards officially translated into Spanish.

Then briefly describe what happens at each step.

Plan (Plan / Planning)
At this stage the planning is done, ie, needed to meet the desired objective defined activities. This is where data relevant to the current process are obtained, the requirements of the new process are set and specifications that are desired are detailed. There are numerous tools that can be used at this stage. They are: the Gantt, the failure mode and effects analysis (FMEA) and Function Deployment Quality (QFD).

Do (Make)
the necessary changes are made. Where possible, it is implement on a small scale, before putting them to function fully. Even pilot tests can be performed.

Check (Check)
After a prearranged time, the current state of the process is verified through data to compare with the requirements established in the first step. In other publications we have seen several assessment tools that can be useful at this stage: Ishikawa diagrams, Pareto Diagrams, Control Lists, for example.

Act (Act)
Of the results arising from the analysis in the previous step, you act accordingly. Herein lies the success of the method as a tool for continuous improvement. The operation is cyclic, improvement is continuous, so we must act after replan and go systematically perfecting the process.

In recent years, it is common to see references to as Cycle PDSA method instead of the classic PDCA. PDSA changes its third stage CHECK to STUDY, The cycle would be as Plan-Do-Study-Act. The same Deming kept this name his last years, and today the members of his Institute give continuity.

What is the difference? It is actually a matter of concepts, in order to see the method. The criterion to use one or the other denomination has to do with the question we perform when comparing the results obtained and expected. While Check (Check) answers the question ‘How is the system compared to what we expected?’ Study (Study) changes the perspective of your question to ‘What can we learn from the difference between what we got versus what we expected? ‘. It is clear: PDSA is an evolution of PDCA. Like everything, the improvement method itself can improve.

PDCA in ISO 9001: 2015

Both ISO 9001 and many other international quality standards, environment and safety PDCA mentioned as the most important method of continuous improvement. In the Spanish version of ISO 9001: 2015, for example, it is represented the structure of the standard through a PDCA cycle, which includes Chapters 4 through 10. The following chart shows the structure appears. Parenthetically chapter corresponds to what each item shown.
PDCA (PDSA) in ISO 9001: 2015
6 steps control, Ishikawa

Based on the model of the Deming Circle 4 steps, Kaoru Ishikawa poses a 6-step model. The model is virtually identical, only steps P and D Cycle PDCA are subdivided into two steps each.

The 4-step model, as described by Ishikawa includes:
Decide on a goal and decide the methods used to achieve the objective.
Carry out education and training and do the job.
Check the results.
Apply corrective action.
Breaking down the first two steps, we get the 6-step model:

Decide a target.
Decide which methods to use to achieve the objective.
Carry out education and training.
Do the work.
Check the results.
Apply corrective action.

PDCA is well complemented with other continuous improvement techniques such as kaizen, which we discussed in other publications.

Deming Circle (Shewhart): PDCA Cycle

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