Design Comment

DESIGN

COMMENT

Michael Paloian, Integrated Design Systems, Inc.

Root Cause Analysis – A Critical Design Skill

Choosing product design as a career path will lead you into many challenging and sometimes very frustrating experiences. It is a gratifying profession that requires you to learn, think, be creative, and solve problems constantly. The design process is often equated to sitting at a computer and generating CAD files. Nothing could be further from the truth. Great designs are developed from brilliant ideas, which have been skillfully engineered into elegant devices that are beautiful, reliable, and minimal. The last step in the design process is often overlooked because it is not glorious or dramatic. It is sometimes referred to as debugging or troubleshooting, but is essentially design analysis and verification. This process requires a designer to be objective, observant, analytical, and technically skilled. We’ll discuss some of the problems frequently encountered toward the end of a design project immediately before production begins in the remainder of this article.

The CAD files been checked hundreds of times throughout the design process. Parts have been inspected for draft, clearances, radii, and dozens of other essential considerations before they were released for tooling. You’re sure everything will be fine when parts are molded and assembled. The big moment arrives, and now you’re confronted with the reality of parts not fitting as they were expected to fit. There are numerous interferences, irregular gaps between mating parts and unsightly warpage on critical cosmetic surfaces. Everyone is surprised, and all eyes are on you. Why are we dealing with these problems before this critical production launch? Numerous suggestions for solving these problems are offered by the salesman, production guy, manufacturing manager, and quality people. Most of the corrective actions imply your design is wrong, and the molds must undergo significant changes to remedy the situation. The pressure is on; what do you do? You must maintain a cool head, an open mind, and begin to examine each problem step-by-step critically. You’ve transformed yourself from a temperamental creative designer to a calm, unemotional detective whose mission is to find the root cause of all the problems and offer the best solutions for all of them.

Design analysis and verification during production startup should comply with the following guidelines: • Never make any design changes without first identifying the root cause of the problem • Analysis should be methodical and consistent • Maintain vigilance in observing all inconsistencies • Dimensional measurements should account for potential part warpage and distortion • Multiple measurements of the same feature should be recorded • Sample measurements should be made a room temperature

Identifying the root cause of problems of products in the field should include the following considerations: • It’s always helpful to be able to trace parts with a date stamp to a particular date of manufacture and resin lot • Always document the number of failures, the mode of failure, the use conditions, and the environment • Environmental factors include temperature, loads, time in the field, chemicals, etc.

Comparison of measurements to production control drawings will confirm parts have been molded within specifications or are not compliant. Production control drawings are essential for identifying critical dimensions and tolerances. If tolerances are too tight, design modifications will be required for parts to fit one another as intended. Unfortunately, I cannot elaborate on this topic within this editorial, but I do hope this brief focus on root cause analysis has provided you with some insight pertaining to the complexities of this critical step in the design process.

If you have any comments or questions, please feel free to contact me at paloian@idsys.com. I’d love to hear from you.