Twin-screw compounding machines

Twin-Screw Compounding Machines It is an extruder with two or more screws. It is possible to homogenize the PVC compound and extrude it at the same time. 

The first twin-screw compounder (ZSK) went into production at Werner Pfleiderer in 1957, marking the beginning of a success story for this type of machine. The first major applications were in the chemical industry. Today, the machine is predominantly used in the plastics industry, e. g., in extrusion and compounding. These screw machines are therefore also known as extruders and the twin-screw is known as the twin-screw extruder. 

The plant starts with twin-screw compounding of PP and glass fiber to produce a hot sheet, which is robotically transferred to a vertical compression press of 3300 tons. The fast-stroke press has automatic parallelism control. Another robot transfers parts to a 110-ton press that punches out attachment holes in the parts. Finally a third robot transfers parts to a machine that inserts hole reinforcements and inspects the parts. 

AtNPE, Coperion Group displayed an 18-millimeter twin-screw ZSK machine to simplify scale-up to production quantities in laboratories developing plastic compounds, masterbatches and powder coatings. The machine is making its North American debut at NPE, after the firm sold several earlier this year in Europe [7, 8]. 

Such machines are particularly suitable when there is a requirement for compounding as well as extrusion—as with unplasticized PVC. If compounding and extrusion of the formulation can be carried out in series, so that it is not necessary to heat it twice, the quantity of heat stabilizer added can be reduced. For reasons such as this the manufacture of unplasticized PVC pipe has become a typical use for twin-screw units. 

The twin-screw injection molding extruder is an injection molding machine that is capable of both blending/compounding and extrusion in one step. Because it is a one step process, the fibers never go through the entire extrusion process as well as the pelletization that limits the fiber size, but are blended into the molten plastic before injection. The screw part of this machine is based on a non-intermeshing, counterrotating twin-screw extruder (Chapter 5). One of the screws in this machine is capable of axial movement and has a non-return valve on the end. This action enables the screw to inject and mold parts. 

Co-rotating twin screw extruders are the dominant tjqie of compounding machines. A broad variety of compounding tasks can be executed efficiently [790]. The main advantages of this type of machine are the following [730] ... 

To really control the mixture and dispersion of additives, or to do reactive extrusion, a twin-screw extruder is necessary. Twin-screw extruders are available in several different configurations, but for the work of compounding the most often used is a closely intermeshing co-rotating extruder, with a specially designed screw for the particular task. In order to accomplish this with the least amount of machining. 

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