Laser Weld Penetration Estimation Using Temperature Measurements

[+] Author and Article Information
K. N. Lankalapalli

FANUC Robotics North America, Inc., Rochester Hills, MI 48307

J. F. Tu

School of Industrial Engineering, 1287 Grissom Hall, Purdue University, West Lafayette, IN 47907-1287

K. H. Leong

Laser Applications Laboratory, Technology Development Division, Argonne National Laboratory, 9700 South Cass Avenue, TD/207, Argonne, IL 60439-4841

M. Gartner

Ford Motor Company, Box-16, ATEO-Livonia 36200 Plymouth Road, Livonia, MI 48150

J. Manuf. Sci. Eng 121(2), 179-188 (May 01, 1999) (10 pages) doi:10.1115/1.2831202 History: Received July 01, 1997; Revised February 01, 1998; Online January 17, 2008


Penetration depth is an important factor critical to the quality of a laser weld. This paper presents a 3D heat conduction model with a moving line source to correlate the temperature measured on the bottom surface of the workpiece to the weld penetration, weld bead width and welding speed. Temperatures on the bottom surface of the workpiece are measured using infrared thermocouples located behind the laser beam. The averaging effect due to the temperature measurement spot size is analyzed. This paper provides a model-based approach for laser weld penetration monitoring instead of a pure empirical correlation between a measured signal (e.g., acoustic, infrared) and the penetration depth. Experiments were conducted to compare the depth estimation based on the model to bead-on-plate welds on low carbon steel plates of varying thickness at different laser power levels and speeds. It is shown that the temperature on the bottom surface is a consistent indicator of penetration depth and that the correlation is also sensitive to the sensor location as well as other process conditions such as weld shape, width, and the plate thickness. The proposed model is computationally efficient and is suitable for on-line process monitoring application.

Copyright © 1999 by The American Society of Mechanical Engineers
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