A Look at “Assure Quality at the Source”

by Ken Snyder


“Assure Quality at the Source” is a principle in the Continuous Improvement dimension of the Shingo Model. Perfect quality can only be achieved when every element of work is done right the first time. If an error should occur, it must be detected and corrected at the point and time of its creation. This is done through error-proofing – i.e., taking countermeasures to prevent quality problems from occurring again.

Suggestions and Rationales

Four different suggestions have been submitted to improve the description of this principle. All four suggestions are based on the premise that “assure” is either the wrong word, or is easily misunderstood. The most common definition of “assure” is “to tell confidently to dispel doubt.” This is not the intended meaning in the context of the Model. A less common definition contains the intended meaning: “To make something certain to happen.” Because this definition is less common, and the more common definition creates some confusion, it is worthwhile to consider these suggestions:

  • “Guarantee Quality at the Source.” The most common definition of “guarantee” is “a formal promise or assurance that certain conditions will be fulfilled.” While the intention is to clarify “assure,” this word tends to perpetuate the existing confusion.
  • “Ensure Quality at the Source.” This more directly gets at the intended meaning of “assure” as described above. The most common definition of “ensure” is, “to make certain that something will occur,” or its corollary, “to make certain that something (e.g., a problem) will not occur.”
  • “Control Quality at the Source.” This suggestion has value in that it implies that people need to be pro-active in controlling quality, rather than ensuring quality after the fact. This also implies a heavy responsibility on the person performing the work to be responsible for the output. This is consistent with error-proofing.
  • “Build in Quality.” This is an interesting suggestion, but seems to be specific to manufacturing. It doesn’t seem to fit healthcare or other service settings.

“Ensure” or “Control”?

“Ensure” certainly solves the confusion currently experiences with “assure,” and is, therefore, a superior description of the intended meaning of this principle. However, “control,” as explained above, implies being pro-active to solve and prevent quality problems.

The Proposal

Change the wording to “Control Quality at the Source.” “Control,” as explained above, implies being pro-active to solve and prevent quality problems, and the deep responsibility to find the cause of problems and prevent them from occurring again.

It should be noted that Toyota’s phrasing of this principle is, perhaps, even more confusing. The phrase Toyota uses is genryū kanri「源流管理」which literally means “control flow at the source,” where 源means “source,” 流means “flow,” and 管理means “control.” The idea behind this phrasing is that ALL problems need to be controlled at the source – including quality problems, maintenance problems, parts shortages, etc. Otherwise, those problems will stop the flow of products. I’ve asked several Japanese Toyota people what this principle means and they typically respond: “If you have a problem – for example, a quality problem – then you need to stop the line and fix the problem.” I’ve never had them respond with an example other than a quality problem. When I ask them about other issues, such as maintenance, they give a nod that yes, maintenance is included, but then respond that most preventive maintenance is done to make certain quality problems do not occur. The phrase “control quality at the source” clarifies the potential confusion in Toyota’s phrasing that the primary intention is to control quality at the source. Note: Toyota uses the word control.


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3 thoughts on “A Look at “Assure Quality at the Source””

  1. I hope that “Control Quality at the source” will not be mis-read as “Quality Control” at the source, thus transferring responsibility from the Operator to someone in “Quality Control”.
    I agree that the action implied by “Control” is better than the passivity implied by “Ensure”.

  2. Dear Ken:

    Your explanation is spot on. There is so much lacking in terms of what leaders need to know about the relationship between quality management and lean management. Your conclusion would make Dr. Juran pleased.

    Dr. Joseph A. DeFeo
    CEO Juran Global

  3. Ken, you conclude that the revised phrase “control quality at the source” clarifies the potential confusion in Toyota’s phrasing of this principle. Actually, there is no confusion in Toyota’s phrasing. “Control flow at the source” is what they do. Quality problems are just a subset of possible distortions to flow. As you know, TPS is built on the twin pillars of “Just-in-time” and “Jidoka”. Just-in-time involves the creation of flow and Jidoka makes disruptions in flow visible in real time.

    The 1977 Toyota paper (in English) – Toyota Production System and Kanban System Materialization of Just-in-time and Respect-for-human System – says: “The term’ Jidoka’ as used at Toyota means ‘to make the equipment or operation stop whenever an abnormal or defective condition arises’”. Contrary to the belief of many Lean Practitioners, Jidoka does not just deal with Quality, but it deals with any flow abnormality.

    In the book “Profitability with No Boundaries” (Fox and Pirasteh), they include an extensive interview with Taiichi Ohno that took place near the end of his life. In that interview Ohno says:

    “When something in our assembly plants or machine shops needs to be scrapped or reworked it disrupts and slows the flow, it is a big waste. Eliminating these disruptions reduces the cost of making a car and assures that we have a better product. Improving quality wasn’t our primary focus. We tried to remove everything that disrupted achieving a fast-flowing river system. Machines that break down and workers that are absent also disrupts the flow. We had to reduce all types of disruptions to make our river flow quickly and smoothly.”

    “Improving quality wasn’t our primary focus”. You cannot be any clearer than that. While there is nothing wrong with saying “control quality at the source”, I’m not sure it qualifies as a “principle”, at least from the Toyota perspective. The Shingo principle could be stated more accurately as “control ‘process’ quality at the source”. “Product” quality is a byproduct of “process” quality.

    But at Toyota “control flow at the source” means much more than just managing flow disruptions/abnormalities. They actually “control” the flow through the use of Takt Time and Pull. Takt controls the flow rate and Pull assures that the flow is synchronized with customer demand. And Pull also allows “control” of flow “at the source” by connecting the various processes with each other in real time to create a systemic flow. System flow is not controlled by a remote third party such as Production Control.

    There is much to be admired by Toyota’s principle of “control flow at the source”. It’s much more than just Quality.

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