Sewing Needle Temperature

Abstract

The general problem of sewing-needle temperature rise due to frictional heat genera tion is discussed. Several possible mathematical models which could be used to predict needle temperatures are considered. The solution of even the simplest model which seems capable of giving accurate results would require extensive use of a high-speed digital computer. Because the parameters which govern the frictional heat generation and convective heat-loss mechanisms cannot be predicted with any accuracy, the probable computer results do not seem worth the effort required to obtain them. A very simple calculation of heat losses indicates that the thermal conductivity of the needle is the most important property governing needle heat dissipation.

An experimental method of determining the needle temperature by infrared flux measurements is described. The many variables, such as emissivity, geometrical view factors, and signal shape and frequency which relate the flux to the needle tempera ture, are discussed. A calibration procedure is described which eliminates these factors as variables and permits determination of the peak needle temperature with an accuracy of ±2°C.