文档介绍：© Don Winton 1999 ---- 8500_CPU:Desktop Folder:
Process Capability Studies
[The following is based in part on the paper “Process Capability Studies” prepared by M.
Suozzi, Member of the Technical Staff, Hughes pany, Tucson, Arizona,
27NOV90]
Introduction
Process capability is an important concept for industrial managers to understand. The
challenge in today’petitive markets is to be on the leading edge of producing high
quality products at minimum costs. This cannot be done without a systematic approach and
this approach is contained within what has been called “statistical quality control” or
“industrial statistics.” The segment of statistical quality control (SQC) discussed here is the
process capability study.
So why is process capability so important? Because it allows one to quantify how well a
process can produce acceptable product. As a result, a manager or engineer can prioritize
needed process improvements and identify those processes that do not need immediate
process improvements. Process capability studies indicate if a process is capable of
producing virtually all conforming product. If the process is capable, then statistical process
controls can be used to monitor the process and conventional acceptance efforts can be
reduced or eliminated entirely. This not only yields great cost savings in eliminating non-
value added inspections but also eliminates scrap, rework and increases customer
satisfaction. The benefits of performing process capability studies are certainly worth the
effort in the long run.
After a process capability study has been performed, a process will be classified as either
capable or incapable. When the process is not capable of producing virtually all conforming
product, the process is said to be incapable and acceptance sampling procedures (or 100%
inspection) must remain part of the process. Figure 1 shows the process output when
compared to the specification limits for a typical incapable proces