Spurgeon, Susan P.; Cramer, Harlan C.; Zahorchak, Adam (1992, ASQC) Westinghouse ATD, Baltimore, MD 21203
With short production runs on a wide variety of products, establishing efficient and cost-effective repeatable electrical testing capability is essential to meeting customer requirements in a timely and cost-effective manner.
The Advanced Technology Division uses a designed experiment to separate precision (repeatability) from product variability. Fifty pieces of product are tested or measured on a particular instrument twice. The two repeated test measurements are then used to create an X-bar and R chart for samples of two. The range chart represents the difference between repeat measurements on the same unit of product; it indicates the variability of the test over a measued product window. The X-bar chart identifies points lying outside of the control limits and indicates the ability of the test to discriminate between different pieces of a product.
This approach provides an easy method for evaluating the test capability, and the graphical representation of the data promotes acceptance by test engineers because the data is easier to understand.
Variation,X-bar control charts,Testing,Metrology,R (range) chart,Short runs,Design of experiments (DOE),Electronics industry,Experiments