The Mechanics of Section Drawing

Abstract

Although much industrial, experimental and theoretical work has been done on the cold-drawing of round rod or wire to round section, no experimental or theoretical work has been published on the direct drawing of round rod to polygonal section. Since economic factors are compelling manufacturers of cold-drawn section to seek new production route, consideration is being given to the cold drawing of bar or wire of regular section from round stock through a single die. This thesis details theoretical and experimental work and shows that the direct drawing of accurate section from round rod through a single die is practicable. The design of the die profile, that is, the curves of interpenetration between the round section and the drawn section, has been found to be critical, and the most efficient design incorporates the principle of least work done. The theoretical solution to the prediction of draw force, for a variety of drawing parameters for regular polygonal sections, has been obtained and computerised. Also, a new method for the determination of the coefficient of friction has been devised, which is equally applicable to the drawing of round to round section, and experimental work has shown that it also is reliable. The predicted results incorporating values of mean die pressure, and coefficient of friction, compare well with the experimental results and enable the optimum die design to be adopted with confidence allowing work to be allocated reliably in industrial drawbenches and bull-blocks. The new type of dies designed for the direct drawing of section rod is now available under patent No. 29509/76 filed by the N.R.D.C.