Ph.D Thesis

Ph.D StudentRiechstien Riki
SubjectManagement Model for Products Quality through Severity and
Interaction of Defects
DepartmentDepartment of Quality Assurance and Reliability
Supervisor PROFESSOR EMERITUS Amos Notea
Full Thesis text - in Hebrew Full thesis text - Hebrew Version


Every step of a production process involves multiple factors which ensure the quality of the final products. Some of these factors are intrinsically interrelated. There are also control processes that oversee the production process and its outcome at every step.

 The product is evaluated for compliance with requirements (customer stipulations, specifications etc.), and if the result is positive, the product rates as "high-quality".

Defects result from poor quality control; low-grade materials, faulty machinery and product; improper training; misunderstanding of customer needs.

The objective of the study was a model which would facilitate management of the product quality, and a new contract method for the NQ (non-quality) function. This method refers to the economic aspect of retrieval, recognition and processing of data from any production process in the context of the use to be made of the product by the customer. The model, which will make for continued improvement of the QM system in question, is based on the IPMS - Integrated Production Measurement and Severity Scale.

  For any batch-type production, there is a statistical model whereby the distribution is measured by the defectives in each batch or the quality characteristic (QC- frequency, specify, concentration etc.) and marched against a reference constructed on random principles, on the basis of an experimental defectives function.

In the present it is proposed to use the absolute difference of the NQ and reference functions as measure of the non-quality of the batch in question.

The NQ function is constructed by weighting the defectives distribution (or QC) with severity function developed by the customer-user on the basis of prior experience and information, and of course of the application specifies at the product.

In the latter context, insight into the user's particular requirements is essential in designing the product and its components, in selecting its materials, and in determining the product setup and processes. Allowance must also be made for the legal and other aspects of safety and environmental quality throughout the lifetime of the product, including risk analysis and process control.

The model represents a combined approach covering the production-and service problematic from born. The producer's and customer's view points. It permits quality grading of each batch irrespective of its production line, thereby permitting comparison of batches even from short runs.

Finally, the model is of almost universal applicability, from production of semiconductor chips, through measurements of component reliability, remote sensing, photolithography, inductive measurements in soil laboratories-to roasted products in the food industry.