Classificationofsolidificationprocesses.ppt

* * * * * * * * * * * * * * * * * * * * * * * * * * ?2010 John Wiley Sons, Inc. M P Groover, Fundamentals of Modern Manufacturing 4/e Classification of solidification processes Principle of the process Structure/Configuration Process modeling Defects/quality control Design For Manufacturing (DFM) Process variation * Shaping Processes For Plastics - Extrusion 1. Introduction Screen pack * 1. Introduction Extrusion is a compression process in which the material is forced to flow through a die orifice to provide a long, continuous product whose cross-sectional shape is determined by the shape of the orifice * Shaping Processes For Plastics - Extrusion 2. Analysis of Flow Rate * Shaping Processes For Plastics - Extrusion Find the flow rate with respect to various parameters in the system. These parameters include: parameters of the screw, the clearance between the screw and the inner surface of the barrel. * Shaping Processes For Plastics - Extrusion The goal of the engineering analysis: * The flow rate or production rate The pressure of the extrudate or product 1. Flow rate inside the extruder and at the die ? 2. Flow rate outside the extruder and at the die ? die The balance between the two should lead to the actual flow rate as well as pressure * Extruder The general idea to meet the goal: Flow rate of the extruder (not including the die) Drag flow Barrel Screw surface d w v * (1) dc * * Back pressure flow * Back pressure flow (2) * Net forward flow Qx (3) * Linear relation between the net flow rate and head pressure. Assumption: viscosity is constant. The structure: extruder only not including die. The design parameters: those that define the geometry of the screw and barrel. The operating parameter: those that can be changed during the process to affect the output flow Variable * Shaping Processes For Plastics - Extrusion Maximum pressure and maximum net flow rate 0 Maximum head pressure to cause no flow * Shaping Processes For Plastics - Extrusion pm