What are the causes of "variability" that affect quality, and how can we minimize it as much as possible?

Variability in quality can significantly affect product performance. This article explores the causes of "variability" and methods to mitigate its impact.

Many companies struggle with "quality variation" on the manufacturing floor. Even with the same processes and materials, differences in products can occur—this is a challenge seen in many workplaces. The causes of variation can mainly be summarized into the following four plus additional factors: 1. Variation due to people Quality varies depending on the experience, attention, and understanding of procedures by the workers. Establishing standard operating procedures (SOP) and providing training are effective measures. 2. Variation due to equipment Wear and insufficient adjustments of machines can affect products. Regular maintenance and thorough preventive care lead to stable operations. 3. Variation due to materials The quality of raw materials and lot differences are also factors contributing to product quality variation. Strengthening incoming inspections and lot management is necessary. 4. Inadequacies in process management If processes and procedures are unclear or poorly managed, quality will not be stable. Utilizing process capability indices (Cp, Cpk) and statistical process control (SPC) is effective. In addition to these "4Ms," environmental factors such as temperature, humidity, and lighting also impact quality, so monitoring and managing the work environment is required. Significant quality variation can be controlled through "management." Visualizing the workplace and maintaining the PDCA cycle are the first steps toward stabilizing quality.

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