Real-Time Draw-in Sensors and Methods of Fabrication

Draw-In Sensor for Sheet Metal Forming NU 2001-024 Inventors Jian Cao Junghoon Lee Michael Peshkin Abstract Northwestern researchers have invented a device to monitor process quality for sheet metal fabrication. The invention, made from printed-film technology, measures the so-called 'draw-in' at points on the periphery of a sheet metal blank during press stroke. Such monitoring is especially important in automotive and aerospace manufacturing. Sheet metal forming is one of the predominant processes in the manufacture of automobiles (about 300 parts per vehicle), and is also widely employed in the manufacture of aircraft, appliances, beverage cans and many other products. As the automotive industry replaces sheet steel with high-strength and low-weight materials like aluminum, the industry must face the increased challenge of wrinkling and tearing of the sheet metal. The edges of a sheet metal blank move inward as a press forms the blank into a part, and the amount by which the blank moves in the press is referred to as "draw-in." It is important to measure and control the amount of draw-in at several points around the circumference of a part because too little draw-in can tear a part, while too much draw-in can wrinkle the part. Further, with more complex geometries implemented in the automotive industry, draw-in becomes especially difficult to measure and control around the periphery of a part. Manufacturers of automotive and aerospace parts would benefit with this new sensor. R&D groups would apply the sensor to test tool performance. Quality control and production engineers would apply the sensor to monitor and control production performance on a real-time basis. Real-time production control of sheet metal forming is especially important if sheet metal properties vary among production lots. Applications o Sheet metal forming for manufacturing automobiles, aircraft, appliances, beverage cans o Test tool performance o Monitor and control production performance on a real-time basis Advantages o Sensitive to complex geometries o Non-invasive/Non-contacting o Easy to apply o Extremely rugged o Inexpensive (possibly disposable) o Real-time production control to account for variability between production lots IP Status Issued US Patent No. 6,769,280.