Effect of die pockets on the extruded products in Multi-hole Extrusion Process: A finite element simulation study.

Abstract

Multi-hole extrusion process uses a die with more than one orifice through which the billet material is allowed to flow under compressive load. This process is suitable for obtaining many extruded parts of different shapes and sizes (automobile parts and components for medical devices) from a same billet material. The extrusion load, quality of the extruded parts depend on many process parameters like extrusion ratio, billet length, location of orifices or holes on the die, die land length, die design, lubrication and extrusion speed. During design of a multi-hole die, each hole shape and the profile of the hole are mainly considered. In that context, the die pockets play a major role in the extrusion process. The pockets of different geometry and shape are provided at the entry side of the die, through which the work material flows and subsequently pass through the die land region. The properly designed die pockets help in reducing extrusion load and produces parts with less variation in length. In the present finite element study, 2-hole, 3-hole and 4-hole dies have been used to extrude a billet material of 20 mm length and 20 mm diameter at a extrusion speed of 1 mm/min. This low extrusion speed does not put any strain rate effect in the extrusion process. The FE package DEFORM 3D has been used for this study. The diameter of each hole is 3 mm and the pockets of diameter 6 mm and depths of 3, 4, 5, 6, 7 and 8 mm are used. The billet material of lead alloy is used for understanding the process in both simulation and experiments. The detailed study on the extruded product lengths, mean stress on the product and the effective strain are studied. From the study it is observed that optimum pocket geometry for a particular die provides least variation in the product length, mean stress (compressive) and an in-depth focus on the deformation behavior (effective strain study). The study will help in selecting an optimum die design for obtaining high productivity with better quality products.