Skip to main content

Continuous Quality Improvement Through PDCA and DMAIC Cycles

  • Author:
  • Updated date:

I am a trainer and consultant in Lean Manufacturing, Six Sigma, quality management, and business management.

Deming Cycle, Shewhart cycle, PDCA Cycle

Deming Cycle, Shewhart cycle, PDCA Cycle

Continual Quality Improvement

Continuous quality improvement does not just happen; it has to be planned and managed using tools such as PDCA and DMAIC. If you want to be better than your competitors and to flourish as a business, then you must ensure that your business processes are continually improved. Failure to do so will see your competitors eventually taking your customers from you!

Continuous quality improvement is not just going to happen; you need to have a system to ensure that it happens: The PDCA cycle—Plan, Do, Check, then Act—is the obvious choice as a continual cycle of improvement. This is why it has been adopted as the model around which ISO 9001 has been written. ISO 9001 uses the PDCA model as a framework around which you can run and improve your business.

What Is the PDCA Cycle?

Plan, Do, Check, Act (PDCA) was first put forward within the works of Walter Shewhart and later popularized by W.Edward Deming, who referred to it himself as the Shewhart cycle. Since then, it has been more often called the Deming cycle or Deming Circle after Dr. Deming.


  • Plan
  • Do
  • Check
  • Act

It has also been known as PDSA or:

  • Plan
  • Do
  • Study
  • Act

In fact, Shewhart would argue that Study is a correct way to approach this improvement cycle rather than merely checking the outcome of implementing your plan.

The PDCA Cycle forms the backbone of the ISO9001 series of standards for developing a quality management system.

The PDCA Cycle provides a simple repetitive cycle to drive continuous quality improvement of your business processes. It is the power of its repetitive nature that can really bring benefits to your business. You should never be satisfied with achieving your first set of goals; you must continually challenge your business and yourself to drive continuous improvement by continually going around the PDCA cycle.

PDCA and Kaizen

Kaizen is the Japanese term for continuous improvement and is implemented by self-directed teams within many Japanese businesses. They use the PDCA or PDSA cycle as promoted by the quality Gurus after WWII, as a starting point to improve their businesses.

They see kaizen as a whole series of small improvements to their processes. They expect every employee group to plan and implement many small projects to continually improve every facet of their business, ensuring that they stay ahead of their competition.

The west, however, prefers to implement its kaizen initiatives through "kaizen blitzes". Rather than entrusting the operators to continually improve under their own direction, we hold a kaizen blitz event to make a large-scale improvement of an area or process.

Whichever approach you take however to using kaizen, you will still use the PDCA cycle as the backbone of your process. The book below is a very simple and easy-to-understand guide to understanding the improvement cycle and how it relates to kaizen.


"Plan" in the PDCA Cycle

Define what it is that you wish to achieve; depending on the scale of your project, this could be the overall project aims of the business or a specific part of the overall improvement plan.

You need to define exactly what it is you are trying to do or the problem that you are trying to solve; try to define it in as precise a manner as possible. For instance, reduce the levels of defects in the extrusion process from 7% to less than 2% by the end of this year or identify and design two new product lines for the xyz market for introduction at the show next June.

Depending on the complexity of the problem to be solved at this point will define the level of planning and organizing required; it is not unusual to see PDCA loops within other PDCA cycles to solve individual parts of the overall problem.

"Do" in the PDCA Cycle

As it says, "do" it, implement the plan; obviously, this is far more complicated than a mere two-letter word, but this is the stage where you stop planning and start to make things happen! Often the point where many projects begin to flounder!

In my experience, "Do" can be one of the hardest parts of PDCA as many improvement projects flounder and fail to get past planning for a host of reasons. Often a lack of support from top management due to everyday operations prevents people from having the required resources (time) to follow through.

"Check" in the PDCA Cycle

"Check" can take many forms, it can be as simple as a cut and dried we did what we said we would do, or it could be a full-blown investigation with data gathering and analysis to understand the results of the actions taken, hence why Deming later changed the cycle to PDSA with "Study" replacing the rather general term of "Check".

In larger projects, this may be an ongoing process with results published and analyzed each week or month as an ongoing cycle of repeating the overall PDCA process.

PDCA Plan Do Check Act in Quality Improvement

PDCA Plan Do Check Act in Quality Improvement

"Act" in the PDCA Cycle

At this point, if your check shows that your planned activities have achieved your planned result, it is a matter of ensuring full implementation and standardization of your actions to maintain the results. Then look at your next step in the planning side of the cycle to maintain the continuous process improvement cycle.

If you have not reached your goals set out in the plan, then look at your plan, modify what you do, and continue around the cycle until you achieve your plans.

Standardized Processes

Many businesses do not plan to improve on a firm foundation. If you do not have a stable and repeatable process in the first instance, how can you be sure that your actions have been responsible for any improvement or even failure?

Before we start any improvement project, we need to be sure that our processes themselves are repeatable and stable. This is often where many six sigma projects fail; they launch into data collection and analysis for several weeks only to find that their data is "all over the place."

They will find multi-peaked bar charts of results due to variations between shifts, operators, and a host of other factors. The place to start is with, first of all, ensuring that the process itself is "correct" before you even start. Work with the team to standardize and document the process first before you begin any continuous improvement project. Of course, your standardization itself should follow the PDCA cycle!


The PDCA is a very simple process; Deming himself changed the cycle to PDSA after a few years, the “S” being study. The reason is to put more emphasis on the study side of the cycle so that you “study” the results of what you have done rather than just a cursory “check”.

DMAIC has come out of the six sigma philosophy and has expanded on the PDCA cycle. The DMAIC steps are:

  • · D - Define opportunity
  • · M - Measure performance
  • · A - Analyze opportunity
  • · I - Improve performance
  • · C - Control performance

Basically the same principle as PDCA or PDSA but puts more emphasis on the data gathering and analysis within the six sigma methodology, but again an iterative cycle to continually improve the process.

DMAIC Cycle for Continuous Quality Improvement

DMAIC Cycle for Continuous Quality Improvement

Lean Six Sigma

As I mentioned earlier in this article, many improvement projects, especially six sigma projects, fail to ensure that they started with a solid foundation on which to improve. Lean uses many tools, such as 5S and Total Productive Maintenance (TPM), to ensure that your business has a stable set of processes.

Just by implementing lean tools, you will often find that you remove the variation that you would otherwise be running six sigma projects to reduce. This is why many now combine the two philosophies and use the ideas from both in harmony to drive improvement through lean six sigma or just lean sigma.

Continuous Quality Improvement

PDCA, PDSA, or DMAIC are all simple but powerful tools to drive continuous Quality improvement, a must for business survival. Implemented efficiently as part of the culture of your business, these tools can help you not just survive but flourish as a business.

Following these cycles through an iterative spiral, each cycle feeding into the next will help you to achieve your business aims and stay ahead of your competitors. However your process will need to be supported by the other quality tools. Read here about the Seven Quality Tools.

Use PDCA and DMAIC Cycles with Continuous Quality Improvement Tools

Use PDCA and DMAIC Cycles with Continuous Quality Improvement Tools

This article is accurate and true to the best of the author’s knowledge. Content is for informational or entertainment purposes only and does not substitute for personal counsel or professional advice in business, financial, legal, or technical matters.


Tony (author) from At the Gemba on September 11, 2010:

Thank you for reading Winterfate. I like PDCA, a very simple but effective tool for continuous quality improvement, it should be taught in every college.

Darrin Perez from Puerto Rico on September 10, 2010:

I learned a little about PDCA when I was in college. This is a very useful reference! Nice hub! :)