Analysis And Simulation Of The Forming Stress Of A Green Part Formed On A Hydraulic CNC PM Press

Powder metallurgy (PM) is a forming technique of less or no cutting. It cangreatly improve the utilization ratio of resources and energy. The die forming withhydraulic press is the most popular in many forming ways. There is moredemanding on performance of PM press along with its wide application. CNC PMpress is better suitable for obtaining products with complex shape and uniformdensity.In this paper, analysis method is studied for pressing force in powder pressforming as the important process of multi-step powder metallurgy. First of all,based on the theory of unequal height powder pressing, the method of structuredisassembling is present. Then, according to the theory of equal stiffness curve ofcompressive metal powder, the way of structural disassembling and transformationis put forward. Finally, the multi-step powder metallurgy can be disassembled andtransformed into many simple cylinders for pressing force analysis.In order to establish mathematical model of the pressing force, two experimentswere processed. Firstly, the friction coefficient curve was obtained at the interfacebetween mixed iron powder and cavity die wall in different pressing force using aspecial friction coefficient test device. Secondly, compressive stiffness curve withdifferent powder height was got in a cylindrical cavity die with a certain size. Usingdata fitting function of MATLAB, the mathematical expressions of the curvesobtained by the two experiments were got. Therefore, the pressing forces of themulti-step powder metallurgy can be analyzed using the mathematical expressions.Using the AMEsim simulation software, a simulation model of multi-steppowder metallurgy is constructed. Combining the mathematical expression ofpressing force with the hydraulic system simulation function in AMEsim, thepressing curve of each plug was obtained. Then, using the optimization function inAMEsim, the corresponding optimized parameters were got to meet therequirements of the pressing speed.In this paper, the way of disassembling and transforming the multi-step powdermetallurgy into simple cylinders can offer reference data for powder pressing theory, thus the motion of each plug can be controlled with higher efficiency andaccuracy.