Plastics Workshops and Seminars
Extrusion
Instructors: Dr. John Perdikoulias
WHO SHOULD ATTEND:
The student should have a desire to better understand the controlling mechanism of single screw extruders and extruder performance. It is a practical and intensive introduction for people in the extrusion business: engineers, supervisors, lab support, and others who sell equipment and materials to those who extrude. Many line operators and technicians have found it useful, as well. Mathematical topics are presented and explained in a manner easy to comprehend and use for effective trouble shooting and specification.
EDUCATIONAL GOALS:
An intensive introduction to extrusion equipment and extrusion science and technology by an experienced industrial extrusion scientist, this seminar is designed to provide a thorough understanding of extrusion basics and terminology . The course will cover extrusion technology from the basic extruder components to the description of the primary extrusion models in sufficient detail to permit the student to specify new extrusion equipment, characterize performance of current and new screw designs and auxiliary extrusion equipment and to understand the models that are key to understanding the design of extruder screws. Participants are encouraged to bring their problem products to the workshop for diagnosis and discussion during the problem-solving session.
SEMINAR OUTLINE:
I. Introduction to Extrusion
- Introduction: Review of the purpose and history of extrusion systems , and some basic properties of thermoplastic materials. Basic extrusion rheology: what is melt index, meaning and usefulness of shear rate and viscosity, shear-thinning and the power law
- Extrusion equipment: Motors, speed reduction and bearings, understanding the motor nameplate. Measurement and importance of rpm, motor amps, melt temperature and pressure. Standard and high performance screw designs: mixer technology. grooved feed zone. Breaker plates, screen changers, static mixers, gear pumps, coextrusion feedblocks. Wear and corrosion. Vented systems. Twin-screw extruders: how they work, and why they are used.
- Extrusion mechanisms: Solids conveying and feeding, bulk density and wall friction, Melting Mechanism, the compression zone, solid bed theory and the origins of surging. Metering zone. How to predict output of a screw. Balancing Solids conveying, melting and metering to improve screw performance, Screw design and scale up principles and methods, the role of computer simulation
- Operation: Setting temperature profiles, diagnosing extrusion problems and determining corrective actions. Energy consumption, start-up and material change, shutdown, cleaning small parts, maintenance, and safety. The importance of reading instruments, record-keeping and testing of finished products. Streamlining flow passages and avoiding degradation. Coupling with melt pumps and the operation of Tandem Extrusion systems
- Characterization: Measuring performance of extrusion systems, Interpreting performance results, Setting extruder and screw specifications for products and coextrusion systems
- Trouble Shooting Extrusion problems: Define & quantify the problem, gather data as background (new problem or day 1 defect). Thickness Problems, Appearance Problems, Strength Problems, Material Problems & Operating Problems
- Avoiding Problems by thoughtful product design, equipment and material specs, good maintenance, statistical process and quality control, computer simulation, and well-trained personnel.
- Student problems for discussion: Bring your questions on existing problems for review and class room discussion.