Page 48 - MetalForming May 2012

Dimensional
Measurement
of Automotive
Stampings
The Holy Grail of measurement is to develop one system for the stamping plant that can potentially perform all of the required functions with reliability, repeatability and accuracy.
Here we present the pros and cons of a few of the most common dimensional-measurement systems.
following discussion of various meas- urement systems, since proper use of GD&T to datum a part is significant to the success of the measurement system.
In a die shop or stamping plant, two important measurements must take place. First, part measurements must be reliable, repeatable and accurate. Then we need a system to accurately measure the dies, enabling the use of the data to generate offsets to the sur- faces measured. This process will allow the end product to be manipulated to provide a stamping that meets design requirements and, therefore, eliminate
BY HARI MENON
Measurement systems for auto- motive stampings can cause controversy through the auto- motive enterprise, since these systems vary from the body shop to general assembly due to operational efficiency and other requirements. Basically, it boils down to the ‘stamping guy’ not measuring parts correctly, and there- fore not providing parts to the right specifications.
Body-shop workers often will check a panel in ‘free state’ based on geo- metric dimensioning and tolerancing (GD&T), where only the A-B-C datums are engaged and dimensions are taken, with the expectation of the stamping behaving like a rigid body. While die
Hari Menon, MBA, is president of Opti- mized Manufacturing Group llc, spe- cializing in manufacturing and quality consulting combining lean manufac- turing and Six Sigma methods. He also is the author of the book, TQM in New Product Manufacturing: 248/805-4787; omgroupllc@gmail.com.
compensation—to bring the dimen- sional adherence to the requirements to the GD&T—has developed by leaps and bounds, the expectations of the body folks often are unrealistic, though it clearly is getting closer to the require- ments for clamping the secondary datums.
This is stated as a prelude to the
46 MetalForming/May 2012
www.metalformingmagazine.com
Feeler and step gauges (shown here) offer simplicity when measuring stamped parts, providing the die maker and the stamper a good sense of the dimensional accuracy of a panel.