Research On The Theory And Process Parameter Of Cold Thread Rolling

In recent years, the thread cold rolling technology was rapidly developed due to its high efficiency, low cost and perfect properties of its production. But few studies were carried out on the technological theory and the mechanical analysis of the precise forming. Especially for hollow parts, because the wall thickness was determined by the empirical or trial and error methods, the production was unscientific and inaccurate, which resulted in serious waste of materials.In this paper, the cold thread rolling process and theory were analyzed. The rolling process was divided into four stages according to the amount of feed of the thread rolling dies. The rolling force and the amount of feed in different stage were analyzed. The effect of the amount of feed on the rolling force was put forward for the first time. It was proved that the rolling force would increase with the increase of the amount of feed. The outside diameter of the blank was resolved according to the principle that volume was invariable in the plastic deformation. By analyzing the relation of the radial rolling force, the tangent rolling force and the axial rolling force, the relation formulae were obtained. The rolling forming of the hollow parts and the difference between the solid parts and hollow parts were researched. The minimum wall thicknesses were solved and their formulae were deduced by solving the static undetermined structure. It can be concluded from the result that three-die rolling was more suitable for hollow workpiece than two-die rolling. The thread parts with thinner wall thickness could be rolled with three thread dies. The numerical simulations on the rolling process of solid parts and hollow parts were carried out with DEFORM software. The change rules of the rolling force and the torque were analyzed. The stress and strain of the workpiece were analyzed. The slipping in the forming process and the repair of the slight destabilization in the final finishing stage were analyzed as well. The theoretical results were verified well.Through the experiments on three-die thread roller with different rolling force, different amount of feed and different wall thickness, corresponding data were obtained and analyzed. The influences of the wall thickness, the amount of feed of the dies and the rolling force on the rolling process were obtained and the theoretical results were proved.The conclusion provides the theoretical basis for the further research of the cold rolling technology and practical operation. It has a theoretical significance and practical value.