Development of Continuous Lubrication Method for Forward Extrusion

Despite the extensive research that has been carried out on alternative liquid lubricants for extrusion processes, it remains challenging to apply liquid lubricants to forms involving long components, such as rotor shafts, which undergo substantial surface expansion. In this study, a continuous lubrication method is proposed, in which lubricant is sealed into the extrusion die using a counterpunch. The negative pressure generated by the punch pulse motion during processing is utilised, and this is applied to the forward extrusion of a two-step shaft profile. The clearance between the container and the billet has a significant impact on the pooling of the lubricant within the extrusion die. It was established that, at a die half-angle of 15°, the maximum load was reduced by 15% at a billet diameter of 9.85 mm for a container diameter of 10 mm. A comparison of load–stroke diagrams from finite element method (FEM) simulations shows that the coefficient of friction (μ) decreased to approximately 0.05–0.1 during reloading and increased to a maximum of approximately 0.12 during loading. It was determined that the die half-angle of 30° resulted in a shorter sliding distance within the die than the 15° angle. This finding enables the suppression of the increase in friction. The findings of the FEM analysis substantiate the notion that material influx into the undercut area exerts an influence on relubrication.