The Extrusion Division Board is composed of 27 members
from industry and academia. The Board members are noted for a variety
of plastic processing and business skills. In this feature some basic
information is presented by a member or former member to be known to be skilled and
experienced in a niche field.
Dr. Mount is an independent consultant and a recognized expert inpolymer and film extrusion, metalization, coextrusion, andrheology. He has over 30 years experience in extrusion theory,practice, design, and operation of extrusion lines. He did hisgraduate studiles with Professor Chang Chung and gained over twodecades of practical experience with ICE and Mobil Chemicalbefore becoming an indendent consultant. Dr. Mount is on the Board ofDirectors of the Extrusion Division and is a Fellow of SPE.
Here is a slide show of some basic information about rheology of plastic materials.
Wayne A. Gifford is the president and lead consultant of DIEFLOW, a consulting firm specializing in the design of extrusion and co-extrusion dies for film, sheet, and coating processes. Wayne is the recognized authority in implementing fast and efficient 3-D algorithms for the routine design of extrusion dies and feedblocks.
He is the sole author and developer of DIEFLOW, a 3-D computer model for efficient design of extrusion and co-extrusion dies. Phenomena which include multiple feeds, free surfaces, dieswell, and non-Newtonian fluids with temperature dependency can be incorporated in the model. The model has been used for fiber spinning dies, plastic foam dies, medical tubing dies, as well as film and sheet coating dies.
The efficiency of the model gives it a computaional speed that makes it feasible for huge numbers of simulated design trials. This provides for excellent die design optimization.
Jim Frankland is a recognized expert in all types of single screw extrusion with 44 years of practical extrusion experience. He has designed over 10,000 screws in his career covering every process with sizes ranging from ½” to 23.6”. Designs include barrier screws, wave type, multi-stage, grooved feed, crammer fed, special mixing designs and dual diameters. His background extends to all aspects of extrusion trouble shooting including down stream equipment, extruder design, energy efficiency, polymer specifics and die design. Before retiring and becoming an independent consultant he worked for General Tire Plastics, Arco Polymers, Uniloy, New Castle Industries and Milacron. He served continuously on the Extrusion Division Board of Directors for over 35 years is a Fellow of the Society, and Honored Service Member and received the Bruce Maddocks award for his contributions to single screw extrusion.
Here are few tips from Jim about some recent typical extrusion issues.
Question: We have trouble maintaining an even coextruded cap on our sheet.
Answer: It’s important to match the viscosity of the base resin and cap resin as close as possible to minimize die flow issues. However if the die is an older design and/or not designed for the polymer you are using it may be impossible to get an even distribution of the cap layer. This is particularly true of coat hanger design dies without a restrictor bar. Often these dies can be recut at lower cost than a new die to provide balanced flow using rheology pertaining to your application.
Question: Do barrier screws provide better power efficiency?
Answer: The basic benefit of a barrier screw is its separation of the melted and unmelted polymer. A properly designed barrier screw allows for aggressive shear rates to be applied to the unmelted polymer while applying lower average shear rates to the melted polymer. The result is usually a lower melt temperature, less localized barrel over hearing, and a lower power draw at the drive motor.
Question: How do you trouble shoot gauge variation on a complicated profile?
Surging or gauge variation on complex profiles can come from the extruder, die or down stream equipment. It’s important to eliminate them one by one starting with the extruder. For the extruder one must check the delivery of polymer to the extruder, the polymer consistency, the stability of the extruder (even if it has a melt pump) and the melt temperature variation as a starting point. Proceed to the die heating and any outside forces like air through the die or on the die. Finally all the down stream equipment must be examined for consistency and hang-ups.
Question: We have broken several 4.5” screws in one extruder yet we have the same screw design made by the same manufacturer in our other extruders with no problems.
Answer: I would bet you have an extruder alignment issue. The proper method of alignment is not used by some extruder manufacturers and of course anytime an extruder is moved it should be re-aligned. Also cold alignment of an extruder does not insure that it is aligned for its operating temperatures requiring an extra step seldom used by even some alignment experts.
Dr. Mount is an independent consultant and a recognized expert inpolymer and film extrusion, metalization, coextrusion, andrheology. He has over 30 years experience in extrusion theory,practice, design, and operation of extrusion lines. He did hisgraduate studiles with Professor Chang Chung and gained over twodecades of practical experience with ICE and Mobil Chemicalbefore becoming an indendent consultant. Dr. Mount is on the Board ofDirectors of the Extrusion Division and is a Fellow of SPE. 
Jim Frankland is a recognized expert in all types of single screw extrusion with 44 years of practical extrusion experience. He has designed over 10,000 screws in his career covering every process with sizes ranging from ½” to 23.6”. Designs include barrier screws, wave type, multi-stage, grooved feed, crammer fed, special mixing designs and dual diameters. His background extends to all aspects of extrusion trouble shooting including down stream equipment, extruder design, energy efficiency, polymer specifics and die design. Before retiring and becoming an independent consultant he worked for General Tire Plastics, Arco Polymers, Uniloy, New Castle Industries and Milacron. He served continuously on the Extrusion Division Board of Directors for over 35 years is a Fellow of the Society, and Honored Service Member and received the Bruce Maddocks award for his contributions to single screw extrusion.
