Process capability studies

It is recommended at this stage of the text that the reader unfamiliar with the basic concepts of variation and process capability refer to Appendix I for an introductory treatise on statistics, and Appendix II for a discussion of process capability studies. 

Process development trials, process capability studies, and analyses... 

Process capability study report Measurement systems analysis report... 

Depending on the nature of the work you may require space models, prototypes, process capability studies, or samples of work as evidence of their capability. You may also make a preliminary visit to each potential bidder but would not send out an evaluation team until the qualification stage. 

Process capability studies are studies conducted to obtain information about the inherent variation present in processes that are under statistical control, in order to reduce the spread of variation to less than the tolerances specified in the product specification. 

Preliminary process capability studies are those based on measurements collected from one operating run to establish that the process is in statistical control and hence no special causes are present. Studies of unpredictable processes and the determination of associated capability indices have little value. Preliminary studies should show acceptable results for special characteristics before production approval can be given. These studies and associated indices only apply to the measurement of variables and not to attributes (see below). 

Customer complaints Warranty claims Failure analysis reports Process capability studies Service reports Concessions Change requests Subcontractor assessments Performance analysis Deviations and waivers Contract change records Quality cost data External Quality Audit records... 

Conclusions regarding whether the process is centered at the target and is meeting the specifications can be drawn from the process capability study. When Cp = Cpk, the process is centered. When Cp has a value of 1.0 or greater, the process is capable of producing products meeting specifications otherwise, it is not capable. 

Process demonstration or process capability studies are usually started in this important second stage of the pilot program. Such capability studies consist of process ranging, process characterization, and process optimization as a prerequisite to the more formal validation program that follows later in the piloting sequence. 

In summary, process capability studies start in the development laboratories and/or during product and process development, and continue in well-defined stages until the process is validated in the pilot plant and/or pharmaceutical production. 

Evaluation of cleaning procedures themselves—Many companies prefer to perform a prevalidation study (often referred to as a process capability study or engineering run ) to verify that the cleaning procedure is satisfactory prior to the actual validation runs. This is an excellent opportunity to determine if the cleaning procedures are adequately written. On some occasions, cleaning procedures are not detailed enough and may not provide enough information about, for example, the extent of disassembly of the equipment. If left to interpretation, there is the possibility that different operators may interpret the instructions differ-... 

In Annex 15, the scope was limited to drug products only (omitting APIs), and references to process capability studies (that had not really been given... 

As mentioned earlier, as part of a process capability study, an assessment of variability is conducted. 

Process development (process qualification) or process capability studies are normally started in this important stage II of the scale-up sequence. The scope of stage-II process development consists essentially of product optimization and process characterization studies. Product Optimization ... 

However, cause-and-effect relationships in these situations are obscured by rampant variability and multiple mysterious causes. The approach is passive. Classical observational tools for industry usually include sampling plans, control charts, and process capability studies. In addition, Branning has found two of the most useful observational tools for validation and PAT are process flow charts and fishbone diagrams, which help define the process and identify the potential sources of variability. These observational tools need to be used on a routine basis to collect background data for validation and PAT. 

Process Controls Engineers Control plans and statistical support Process capability studies Production process, and control plan review... 

In the approach based on the analysis of historical data, no experiments are performed in retrospective validation, but instead all available historical data concerning a number of batches are combined and jointly analyzed. If production is proceeding smoothly during the period preceding validation, the data from in-process inspection and final testing of the product are combined and treated statistically. The results, including the outcome of process capability studies, trend analysis, etc., will indicate whether the process is under control or not... 

The purpose of a control chart is to improve the process and the ultimate aim is to distinguish between a variation that is predictable within limits (a common cause or random variation) and a variation that is not (special cause and is a significant trend). A significant trend could be caused by an inconsistency in raw materials or an irregular process operation. A control chart can, for example, be used for process capability studies, or investigating customer complaints. Once a control chart has achieved its objective, it should be discontinued and efforts should then be directed towards other improvements. 

When performing a process capability study using attribute data, the process must demonstrate that it can produce 300 consecutive parts with no defects for all attributes being studied. 

Process capability studies are used to determine what fraction of the tolerance band the process output consumes. Cp measures the fraction with consideration of where the process is centered. Cpk measures the fraction to the closest specification limit if the process is not centered. Cp and Cpk assume that the process is in control. Ppk is similar to Cpk but does not assume that the process is in-control. 

Prior technology SPC and process capability studies are based on the assumption that part characteristics are not related. This is not the case for many, but not all, manufacturing processes. Part characteristics are related (correlated) for many processes. To the extent that this is true, doing SPC and process capability analysis on all part characteristics is redundant, wasteful, and unnecessarily time-consuming. 

Prevention. This comprises the costs of measures to prevent defects from taking place, such as training and process capability studies. 

The AML supports faculty Instruction in seven different courses, and as a support facility, the equipment may be used on a stand-alone basis. The Mitutoyo Coordinate Measuring Machine of the AML is used by students in the "Metal Processes II" course for precision measurement experiments and to evaluate their final projects. The same machine is used in "Statistical Quality Control" for developing statistical process control (SPC) charts and for conducting process capability studies on the machine tools in the AML. 

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