Technical note -: The significance of chuck wall angles in the quantification of seam thickness in canned food

One of the key dimensional measures in quality control of canned foods is the double seam thickness (mm). Electronic micrometers quantify the seam thickness, based on a chuck wall angle of 4.0 degrees due to the seaming chuck being fixed at the same angle during seaming. Investigations of chuck wall angles (n = 144) in non-round cans by a coordinate measuring machine revealed that 93% of the chuck wall angles following seaming were off the interval 4.0 +/- 0.250 (range: 3.146-10.281 degrees. CV = 23%), indicating that the seaming process introduces a significant variance in the chuck wall angle. The aberration in the actual chuck wall angle from 4.0 degrees introduces a bias (epsilon) in the measured seam-thickness (T-ms), which may cause rejection of closed cans as having unacceptable seam thickness based on incorrect measurements. The mathematical deduction of the bias introduced in the measured seam thickness when the actual chuck wall angle is aberrant from 4.0 degrees is presented, and it is concluded that it is erroneous to neglect the chuck wall angle of sealed cans in the methodology of seam thickness determination. Copyright (c) 2005 John Wiley & Sons, Ltd.