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: The balance between the two should lead to the actual flow rate as well as pressure 1. Flow rate inside the extruder and at the die ? 2. Flow rate outside the extruder and at the die ? die Extruder

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

d w v dc (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. The operating parameter: those that can be changed during the process to affect the output flow Variable

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

die Shaping Processes For Plastics - Extrusion Determination of the operating point Pressure and Flow rate 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: pressure of the material. Output of the material: flow rate of the material. Device or manufacturing machine operates on the material  input and output. 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. Requirements: quality, quantity, time, cost, green 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 and variables in the manufacturing system: device parameter, process parameter, product parameter.

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

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 process or manufacturing. Device control. Process control. Product quality, quantity, cost, time, green and sustainability

Integrated Manufacturing Technology Design of products Design of manufacturing systems Design of manufacturing processes They should be integrated to improve the manufacturing practice further. Manufacturing practice includes: Performance (quality, quantity, delivery time, cost) Resilience and sustainability