Quality Scan: Study: Behavior Impacts Measurements
By Chuck Pfeffer
Coordinate Metrology Society (CMS)
Measure twice, cut once. Measurement proficiency is a skill learned and practiced by craftsmen for centuries. It is the first thing we all learned in shop class or in Dad’s garage workshop. A universal rule like this is never questioned because we all understand why it is important. Whether it means another trip to the hardware store or scrapping a high-value machined part, measurement errors are painful.
In today’s world of computerized measurement systems, careful measurement is as important as ever. The benefits of using state-of-the-art systems are evident in how quickly a new user can start taking measurements. It wasn’t too long ago when high-accuracy measurement was left to highly trained and experienced people wearing white coats in the metrology lab. Technology has ushered in easy-to-use, high-accuracy metrology on the shop floor, and put it into the hands of machinists, tool builders, and engineers.
These new measurement tools enable the highest quality processes while eliminating rework and scrap. But how consistently do they perform when put in the hands of a wide range of users? To find the answer, the Coordinate Metrology Society (CMS) hosted a measurement study at their annual Coordinate Metrology Systems Conference (CMSC). The event was organized in conjunction with the CMS 3D Portable Metrology Certification Committee and the National Physical Lab (NPL) from the UK. The study was established to explore the need for a personal metrology certification program. Over that past two years, the measurement study has evolved from a Gage R&R with first principle hand tools to real 3-D measurement tasks using the latest portable 3-D metrology equipment and software.
The 2011 study titled "How Behavior Impacts Your Measurements" was conducted in the CMSC exhibit hall over a two-day period where over 100 attendees tested their skills in measurement. On the first day, measurements were taken with little assistance and training, and on the second day training and suggestions were offered. Measurement study participants were asked to perform three tasks using portable 3-D coordinate metrology equipment: 1) measure a car door using a combination of a laser tracker, retro reflectors, and software; 2) measure an engine compartment using a combination of an articulating arm, probe and software; and 3) measure a vehicle using a combination of a laser tracker, probing, and laser scanning system.
Authors Keith Bevan (NPL) and Trevor Toman (Metrology Manager at Coventry University) analyzed the results of the study and compiled their conclusions into the 2011 CMS Measurement Study report. The measurement criteria used during the research project enabled the authors to examine various training and assessment techniques, such as the evaluation of questioning methods, practical task monitoring and demonstration, and the participant’s prior learning and experience level. Nearly a quarter of the participants had less than three years of measurement experience, a dozen fell in the midrange of three–seven years of practice, while 69 participants were veteran metrologists with more than seven years of hands-on experience with various measurement systems.
Bevan stated the outcome of this study drives home the importance of defined best practices, and understanding measurement fundamentals that enable an individual to make informed judgments about a measurement, irrespective of the technology used, whether it is hand tools or 3-D portable metrology systems. Clearly, questioning and planning the requirements of the measurement help reduce the possibility of making poor measurements.
The results of the 2011 measurement study corroborated the same key areas identified in the 2010 study irrespective of the equipment. The study concluded that knowledge and understanding of metrology fundamentals, which includes questioning and planning, is essential for a sound measurement strategy. The measurement study report can be downloaded from the CMSC web site at www.CMSC.org.
The CMS 3D Portable Metrology Certification Committee is driving toward a pilot exam at the 2012 Coordinate Metrology Systems Conference being held in New Orleans in July. In conjunction with this effort, a new study will be conducted to test the practicality of a hands-on test with a variety of 3-D portable metrology equipment. Join us! ME
This article was first published in the March 2012 edition of Manufacturing Engineering magazine. Click here for PDF.