However it may not be optimal since the cost is not

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Unformatted text preview: ferent from continuous tolerance-cost function, the IT grades characterize tolerances-cost discretely and give more realistic representation of industrial practices. It is also recognized that IT grades of features produced by the same type of processes vary with machining parameters, operators’ skills, machine and tool conditions, fixturing plan, etc. Generally, there is a known or estimated IT grade range associated with each type of manufacturing process. This IT grade range describes the process variability. Any tolerance requirement tighter than lower limit of this range cannot be achieved by corresponding process. On the other hand, it is not cost effective to use this process for any tolerance requirement looser than the upper limit of the IT grade range. The process variability and design requirement can determine process capability indices as follows. The process capability study will be used for quality control planning in the developed CATA system and discussed in a separate paper. Cp = USL − LSL 6 ×σ ⎧USL − x LSL − x ⎫ C pk = min ⎨ , ⎬ 3×σ ⎭ ⎩ 3×...
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This note was uploaded on 08/03/2010 for the course DD 1234 taught by Professor Zczxc during the Spring '10 term at Magnolia Bible.

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