Six Sigma Fundamentals: A Complete Introduction to the System, Methods, and Tools

Statistical tolerancing is an analysis of the tolerance accumulation, in an assembly or system, based on process capability through assembly stack-up, performance variation and cycle time stack-up. It is also the process to identify significant and non-significant effects of subsystems or component variation. The process of tolerancing analysis is based on four steps:

  1. Identify the significant characteristic.

  2. Develop a model.

  3. Acquire process capability data.

  4. Perform tolerance analysis.

Developing model for tolerancing

Typically, there are two types of models: a) linear (such that the coefficient of xs are constants (e.g., Y = X1 + X2 + X3 -X4, 1-D stack-up tolerance; Y = X1 - X2, cost model) and nonlinear (so that the coefficient of Xs are functions of Xs (e.g., , geometric function; P = L/A, performance function; Y = X1exp(0.5X2X3)). To develop a tolerancing model, we follow five steps. They are:

  1. Developed from mechanical assembly tolerance model the parameters and the tolerances (using tolerance chain vector loop and/or assembly kinematics. Perhaps the most common technique to develop a tolerance chain for a one or two dimensional case is the "vector loop technique.")

  2. Derived from physical principles parameters and the tolerances (engineering science, using models from surrogate data, and/or obtaining help from an expert).

  3. Use computer-aided engineering (CAE) tools such as Abacus, ADAMS, Easy5, Nastran and Simulink.

  4. Conduct computer experimentation and response surface using CAE.

  5. Conduct hardware DOE and fit response model.

Related

Категории