Original Date: 01/23/1995
Revision Date: 01/18/2007
Best Practice : Machine and Process Characterization
Sandia National Laboratories (SNL) applies machine and process characterization to define and qualify a process window and parameter space. This allows SNL to quickly produce a product in an agile environment, with the assurance that the necessary quality is present since the product is a subset of the parts and processes that have already been qualified and characterized. To implement agile manufacturing, customer requirements must be quickly translated into designs, then produced or procured, and assembled. In addition, advance knowledge of part types, features, and tolerances are required to develop a parameter space, as well as what machines, tools, and machine settings are likely to be needed to produce the required parts.
There are advantages to defining a parameter space. When parameters are specified on a continuous basis, it is not possible to test and qualify every point within the parameter space; however, by using design of experiments, every point within the parameters can be qualified by testing only certain points. Sandia identifies this parameter space and particular points within that space as a parent-child relationship. The qualification attributes of a parent design are selected for design, fabrication, assembly, and acceptance processes, and the parameter space is defined. The attributes "capable" and "controlled" for fabrication and assembly processes require the collection of data in characterization studies. When characterizing processes, it is important to explain observed phenomena, predict process behavior, control the process, and optimize the process throughout the parameter space.
To verify process characterization techniques, Sandia has implemented machine and process characterization within the A-PRIMED program, an agile product realization of innovative electromechanical devices. Design of experiments was used to verify that the chosen process window or parameter space was capable of producing qualified products throughout the parameter space.
The machine and process characterization for parameter space qualification presents a systematic approach for qualification of high quality parts and processes. This system uses engineering analysis and statistical design of experiments to qualify the parameter space and any individual point within it. This enhances agility by qualifying a family of designs and flexible processes before production.
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