Causes of Variation

Special Causes of Variation

Special causes are problems that arise in a periodic fashion.  They are somewhat unpredictable and can be dealt with at the machine or operator level.  Examples of special causes are operator error, broken tools, and machine setting drift.  This type of v

Common Causes of Variation

Common causes are problems inherent in the system itself.  They are always present and effect the output of the process.  Examples of common causes of variation are poor training, inappropriate production methods, and poor workstation design.

As we can see, common causes of variation are more critical on the manufacturing process than special causes.  In fact Dr. Deming suggests that about 80 to 85% of all the problems encountered in production processes are caused by common causes, while only

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	The. Deming PDCA Cycle	QMS Implementation	FMEA Information	APQP Information
Auditing Information	8-D Problem Solving	Statistics	Error Proofing (Poka Yoke)	Brainstorming
Identifying Waste	Pull Systems	Lead Time Reduction	Planned Maintenance	Quick Setup
Discovering Change	Process Capability - Cp vs. Cpk	Histogram. Animation	Process Loop Animation	Taguchi Loss Function
		Fishbone / Cause and Effects Animation

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