Bilateral Cp / Cpk
What are Cp and Cpk?
- The indicators Cp and Cpk are considered “first generation capability indicators”, because they evaluate and expresses the capability of a technological process relative to a certain accuracy / measurable quality characteristic.
What is process capability?
- The capability of the technological process represents its ability to make parts with characteristics within the prescribed tolerances under specified conditions relating to the factors of influence of the process and in conditions of technological risk assumed at a certain level; underlining other nuances of the concept.
It is admitted that:
<1,00, the technological process has a inadequate performance;
1,00<Cp<1,33, the technological process has a modest performance;
1,33<Cp<1,67, the technological process has a good performance;
1,67<Cp<2,00, the technological process has a very performance;
Cp>2,00, the technological process has excellent performance.
The values mentioned above are not arbitrary, they are deduced probabilistically based on the normal Gaussian law for the distribution of the values of the characteristic of precision / quality.