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

Shaping Processes For Plastics - Extrusion 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.

The goal of the engineering analysis: The flow rate or production rate The pressure of the extrudate or product

die Extruder The general idea to meet the goal: A The result of the equilibrium in pressure between the extruder and die Flow rate at the end of the extruder without the presence of the die. Flow rate at the beginning of the die with the presence of the die. die A Extruder

w Screw surface v d Drag flow Barrel Flow rate of the extruder (not including the die) d w v Screw surface Drag flow Barrel

d w v dc A (1)

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.

Shaping Processes For Plastics - Extrusion The design parameters: those that define the geometry of the screw and barrel. Independent operating parameter The operating parameter: those that can be changed during the process to affect the output flow Variable: characterize the production Dependent operation parameter

Shaping Processes For Plastics - Extrusion Maximum head pressure to cause no flow Maximum pressure and maximum net flow rate

Extruder characteristic Qmax Shaping Processes For Plastics - Extrusion Extruder characteristic Q Qmax pmax p

The result of the equilibrium in pressure between the extruder and die Flow rate at the end of the extruder without the presence of the die. Flow rate at the beginning of the die with the presence of the die. Extrude characteristic die A Extruder

die Shaping Processes For Plastics - Extrusion Determination of the operating point Actual Pressure and Flow rate out of the die Die characteristic die

Shaping Processes For Plastics - Extrusion Determination of the operating point Qx Die characteristic Qmax Operating point Extruder characteristic pmax p

Example: Given: - diameter D=120 mm - length =3.0 m - channel depth =8.0 mm - pitch = 95 mm - viscosity = 75 pas - head pressure = 4.0 Mpa Find: the rotational speed of the screw required to achieve a volumetric flow rate of 90 cm3/s

Solution to be filled in the classroom

Summary: Process has input and output. Input of the material: quantity and quality of the material. Output of the material: quantity and quality the material. Device or manufacturing machine operates on the material  input and output relation of the material Input to the device: torque on and rotation of the screw bar. Output from the device: axial force on and rotation on the screw bar. Head pressure on the material. Forward flow, back flow, net flow. Operating point  actual flow rate and actual (head) pressure

General manufacturing system theory

Shaping Processes For Plastics - Extrusion Discussion A manufacturing process is to change the material to meet some requirement on the material. Requirements: quality, quantity, time, cost, and sustainability. Quantity with respect to time is called production rate. The whole manufacturing system at the equipment level can be viewed as consisting of devices and materials.

Shaping Processes For Plastics - Extrusion Discussion Both the device and material are under the manipulation from the external system that supplies energy or power and material. There are several parameters in the manufacturing system: device parameter, process parameter, product parameter.

Shaping Processes For Plastics - Extrusion Discussion Device parameter/system parameter/design parameter: a category of parameters that describe the device, e.g., diameter of the extruder, length of the extruder, etc. Independent process parameter/operating parameter: a category of parameters that describe the action on the material, e.g., rotational speed of the screw bar, heat energy supply, etc. Product parameter/process variable/dependent process parameter: a category of parameters that describe or characterize the product, which is the output of a manufacturing system, e.g., the flow rate, etc. Product parameter or process variable or dependent process parameter depend on both device parameter and process parameter.

Shaping Processes For Plastics - Extrusion Discussion Manufacturing system design and control: Device design: to determine the device parameter. Process design: to determine the process configuration and parameter. Product modification: design for manufacturing. Device control. Process control. Product quality, quantity, cost, time, and sustainability

Integrated Manufacturing Technology Design of products Design of manufacturing processes Design of manufacturing systems or devices They should be integrated to improve the manufacturing practice. Manufacturing practice is measured by: Performance (quality, quantity, delivery time, cost), and sustainability (stability, green, resilience)