Engineering Research Center for Reconfigurable Manufacturing Systems (ERC/RMS)

Innovative SoV Method Results in a Better Product

The Stream of Variations (SoV) methodology provides an effective means to understand, analyze, and reduce the process-induced variation on final products, thereby enhancing the quality of the products that consumers buy. A new body of knowledge that is based on blending state-space control theory with real-time statistics was created in the University of Michigan ERC for Reconfigurable Manufacturing Systems (ERC/RMS) in order to form the scientific basis for the SoV methodology.

With potential applications ranging from auto bodies through engine blocks to computer processors, the SoV can not only detect the process change as well as the traditional quality control methodologies (e.g., statistical process control, SPC), but also can quickly identify the root causes of quality-related problems. Therefore, SoV methodology can accelerate the ramp-up of a new production system, which has two tangible benefits:

•  reduced time-to-market of a new product improves the
   manufacturer's profit, and
•  products with better quality enhance consumer satisfaction.

A set of tools has been developed based on the SoV theory, including a module for modeling variation-propagation based on the product and process design, part gauge strategy and optimization, and root cause identification. Various validation studies have been successfully conducted in the ERC/RMS testbed. The SoV methodology was implemented in auto-body production (see chart), and is currently being tested at an engine plant of one of the ERC/RMS industrial partners.

To learn more about this topic:
Visit the Engineering Research Center for Reconfigurable Machining Systems research page at http://erc.engin.umich.edu/research.htm.

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A real case in an auto-body plant; time-to-market
was reduced from 26 weeks to 10 weeks; product
quality (6 sigma) was improved from 5.5 mm to
2 mm..

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Last modified: February 25, 2005