CONTENTS OF THE SEMINARS 

Introduction to Extrusion

Introduction.  Archimedes, Nero, Newton and Ohm.  The ten (11) key principles, and some basics of thermoplastic materials.

Hardware.  Motors, speed reduction and bearings. Learning from the motor nameplate. Measurement and importance of rpm, motor amps, melt temperature and pressure. Basic three-zone screw in a smooth barrel, and some popular variations: Maddock, barrier, grooved barrel. Breaker plates, screen changers, mixers, gear pumps, coextrusion feedblocks. Wear and corrosion. Vented systems. Twin-screw extruders: how they work, different designs, where and why they are used.

Principles.  In the feed zone, importance of bulk density and wall friction, concept of perfect bite. In the compression zone, solid bed theory and the origins of surging. In the metering zone, pressure peaks and the blue-screw syndrome. How to predict output of a screw. Basic extrusion rheology: what is melt index, meaning and usefulness of shear rate and viscosity, shear-thinning and the power law, streamlined flow passages and avoiding degradation.

Operation.  Setting temperature conditions, how controllers and microprocessors work, energy consumption, start-up and material change, shutdown, cleaning small parts, maintenance, safety.  The importance of reading instruments, record-keeping and testing of finished products. Role of computer simulation.

Problems & Solutions

Basics of Problem Solving.  Define the problem, quantify if possible, get data as background. 

Thickness Problems.  Surging, distortion of profile, warping, sudden thinning or stopping, swell, drawdown and shrinkage. Effects of mixing and die adjustment. Automatic measuring and feedback, both linear and transverse.

Strength Problems.  Brittleness, unbalance (one direction weaker), effect of porosity, stress cracking, long-term service failure, thermal, UV and water-based degradation. Special problems with regrind and recycle.

Appearance Problems.  Moisture marks, air pocks, bubbles, die lines or bands, die drool, roll nip marks and line scratches, color streaks and poor mixing, gloss, transparency and haze, melt fracture and draw resonance, yellowing and "fisheyes."

Operating Problems.  Output too low, PVC "burning," instrument and controller failure. Motor and bearing problems, misalignment, broken screw, heater burnout. Leakage. Purging.

Material Problems.  Testing materials, contamination, selecting grades, on-line formulation change, control of regrind percentage, special needs for food packaging and medical uses.

Avoiding Problems by thoughtful product design, equipment and material specs, good maintenance, statistical process and quality control, computer simulation, and well-trained personnel.