Abstract
A study has been made of the effect of various needle characteristics on the needle temperature during high-speed sewing without thread. The needle temperatures were determined by means of infrared flux measurements. A very fast indium antimonide detector coupled with a closed-circuit television recording system and the individual determination of needle emissivities overcame almost all the dit1iculties previously associated with this methcxl. Despite the accuracy of the measuring system, there was a fair amount of variation among the needles of a particular group. An average tem perature difference hetween groups of less than 30°F is probably not significant. Xeedle surface finish was found to be the most significant needle variable. Kooltorr R or dark matte surface finishes ran at much lower temperatures than any other finishes, while sewing heavy cotton-duck fabric at 4200 stitches per minute. Nickel, plain steel, and chrome gave increas ing temperatures in that order. There is a moderate, but not completely consistent, effect of higher needle temperatures with increasing diameter. Point type and most other physical variations had very little effect. The range of maximum temperatures for standard 88X 1 size 16 needles was from 640°F for the Kooltorr® to over 800°F for the chrome and nickel finishes.
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