Increase manufacturing yield and improve customer satisfaction!

Process capability improvement

Capability analysis is an outstanding tool that demonstrates the extent of an improvement made to a process. It summarizes a great deal of information simply, showing in successive steps: the capability of a process, the extent of improvement needed, and the extent of the improvement achieved.

There are many circumstances when capability analysis should be carried out: when a new machine or installation is involved (before purchase and after installation); for an existing process or machine, there should be regular checks; when the processing conditions are altered.

Improved process capability means centring a process parameter on a specified target, and reducing the process spread within specification limits. A process capability analysis is only meaningful if the defined specification limits accurately reflect the needs of the final product. Improved process capability will tighten the distribution of process data, but the return on investment is determined by comparing the resulting improvement in product yield or customer satisfaction against the additional cost of providing an improved process.

Capability analysis is summarized in indices; these indices show a system's ability to meet its numerical requirements. They can be monitored and reported over time to show how a system is changing. Like this, statistical control is the default state and the processor is able to establish policies and practices for continuous process improvement.

The main indices used are Cp and Cpk. The indices are easy to interpret; for example, a Cpk of more than one indicates that the system is producing within the specifications or requirements. If Cpk is less than one, the system is producing data outside the specifications or requirements. It is a quite straightforward procedure, which ensures that each critical process is schematically presented and analyzed using appropriate quality or statistical charting methods. Capability indices help to change the focus from only meeting requirements to continuous improvement of the process. Traditionally, the focus has been to reduce the proportion of product or service that does not meet specifications, using measures such as percentage of nonconforming product. Capability indices help to reduce the variation relative to the specifications or requirements, achieving increasingly higher Cp and Cpk values.

PES can advise you on ways to eliminate special cause variation that negatively affects process outcome. The suggestions include ways to minimize common cause variation. This allows for an accurate estimation of process capability. Recommendations on process improvement take into consideration all regulatory aspects of the proposed changes. For firms using third-party statistics packages, our team helps accelerate software system integration.

PES is your partner in order to:

• Define the overall process and sub-processes.
• Determine the reliability of analytical tests, specifications, and measurements.
• Collect, record, and statistically treat and analyze data.
• Test for special cause variation.
• Estimate the process capability.
• Acquire measures aiming at improving the process capability and minimize common cause variation.
• Help you quantify the costs and the return implied by employing the proposals.
• Prove the statements made prior to implementation of the proposed solution.

More information