Theory of Constraints Versus Total Quality Management

Updated on January 9, 2018
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Tamara Wilhite is a technical writer, industrial engineer, mother of 2, and a published sci-fi and horror author.

What is TQM?

TQM stands for Total Quality Management. TQM was pioneered by Dr. Deming, best known for his 14 Points of Quality. He can be credited with the manufacturing miracle of Japan, which evolved from the source of cheap junk to manufacturers exceeding American quality levels by the 1970s. Only then did Dr. Deming’s quality methods take root in the United States.

Total Quality Management shifted focus from the lowest cost and highest volume to quality. Higher-quality products would command a greater price while minimizing costs like rework and scrapped products. If two products were available for the same price, Deming believed quality would win out in the marketplace, increasing sales volume.

The TQM model has five steps: customer focus, process planning, process management, process improvement, and total participation.

What is TOC?

TOC stands for Theory of Constraints. Theory of Constraints refers to the solving of problems by finding the weakest link in a process. Engineers improve output by first identifying the bottleneck and then improving that sub-process. The rest of the production line is sped up until a new production speed is achieved, and a new bottleneck is identified. The Theory of Constraints says there will always be constraints, such as delivery speed or production rates of different types of equipment or labor, but you can maximize efficiency to the point that you aren't under-performing because of one major bottleneck.

TOC as a management philosophy is traced to Eliyahu Goldratt, though the concepts of bottlenecks limiting production levels were well known to industrial engineers before his book. Goldratt’s book applied the concepts of the theory of constraints to whole organizations, and his constraints included legal and regulatory limits in addition to the maximum number of parts that can be supplied by a part feeder or human productivity.

The Theory of Constraints has five steps: identify the limits and constraints, exploit the limits, subordinate other processes to match the constraint, elevate or improve the entire system, then find the next constraint to start the process all over again.

TQM and TOC are both iterative improvement methodologies.
TQM and TOC are both iterative improvement methodologies. | Source

How Are TQM and TOC Alike?

In both TQM and TOC, there is a continual loop to find the next problem to solve. TOC and TQM both look at the production line or service area as a whole process to be improved.

Working with either methodology, quality and production constraints are the result of an entire series of related processes and variables, and the entire system must be improved to increase output or quality.

Both TOC and TQM reject acceptance of the status quo as good enough and seek to improve outcomes or output. TOC is sometimes called the process of ongoing improvement, referring to itself as a process improvement methodology like TQM, Six Sigma, Lean Management or Lean Six Sigma.

TQM and TOC both focus on a single problem at a time. TQM and related methods like Six Sigma look for a “burning platform” or quality problem to solve, and then fix it. TOC focuses on a single constraint. After the system is improved, the next outstanding problem is identified for resolution.

Total Quality Management is similar to Six Sigma in that it aims to improve overall quality, while TOC focuses on output or value.
Total Quality Management is similar to Six Sigma in that it aims to improve overall quality, while TOC focuses on output or value. | Source

How Are TQM and TOC Different?

TOC does not have the specific goal of improving product quality. TQM requires management changes, such as the elimination of quality slogans and management providing adequate resources to the shop floor to improve quality.

TOC does not require continuous learning or training of those on the shop floor. While ideas for improving the process flow can come from the shop floor, TOC is often at the behest of manufacturing engineers and management, unlike quality circles that can generate and flow up ideas from the shop floor.

Total Quality Management aims for zero defects and six sigma quality levels are achievable. Theory of Constraints seeks to maximize output, but the results of each project are only comparable to similar manufacturing operations. A process being modified by TOC is best compared to its prior performance or the performance of similar production lines that have not yet been changed.

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