Introduction

QUALITY PLANNING TECHNIQUES for P/M secondary operations are no different than quality planning for any other manufacturing process--the thought process should be consistent throughout. Developing quality control and inspection for any P/M part begins with the quality planning phase of the product launch process. Quality planning begins well before the purchase order is issued. A thorough review of print requirements with the customer can minimize problems later in the process development. The dimensioning techniques used when designing a part will often determine types of gaging and quality control methods to be used. Geometric dimensioning and tolerancing (GDT) is widely used in design work to ensure the part meets the form, fit, and functional requirements. If properly used, GDT will minimize misinterpretations of the print and lead to the most economical gaging solutions for the part.

It is extremely useful to have mutual (customer/supplier) agreement on gaging concepts during the quality planning process. Quality requirements must also be discussed at this time to avoid capability and processing issues later on. Classification of characteristics (C of C) and the associated capability indices should be thoroughly understood to properly process the part. Secondary operations are often added to satisfy statistical process control requirements.

Another important step in the quality planning process is to plan and develop the process(es) before the first parts are produced--it is much less desirable to backtrack (reactive) in the quality planning activities than to act (proactive) on a well thought out plan with failure modes defined and methods provided to prevent and/or detect those potential failure modes. Two useful tools to help in the planning process are a failure mode and effects analysis (FMEA) and a control plan.

A FMEA process is a very good engineering tool that is used to detect problem areas in the process and to mistake-proof and/or assign the correct process controls. It should be noted that the FMEA process is used to flag potential causes of failure in the process: if the potential for failure is high, efforts should first be made to minimize the potential effects of the failure. Once the risk has been minimized, the appropriate process control can be assigned. Mistake-proofing should be used to reduce risk and ensure quality.

The control plan assigns control methods to the process in an effort to help minimize process and product variation. Features to be checked, method of inspection, control method, frequency of inspection, and responsibility are assigned for each operation. The control plan takes into consideration the FMEA results as well as any classification of characteristics that the customer has defined. Depending on the characteristic, the amount of control may vary, from simple first piece layouts (for tool generated dimensions) to 100% inspection on characteristics generated using incapable machinery.

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