Co-rotating twin-screw extruders with functional modules and self-cleaning screws

The planning of the process part of MARIS co-rotating twin-screw extruders concerns a group of functional modules composed of barrels and, at their inside, of transport and kneading elements at variable geometry, which are mounted on shafts for the motion/shear transmission.
The concept of the functional modules originated from the necessity of achieving a perfect correspondence between the extruder hardware component and the process phases that can be identified with whatever compounding or reactive extrusion.
The equipment capacity to meet with the process requirements can be found, first of all, in the technicians ability to precisely establish the physical or physic-chemical phenomena occurring inside the machine, both in qualitative and in quantitative terms.

The functional modules composing the compounding extruder can be detailed in the following way:


Main feeding:

it is composed of a barrel with a hole on the top and a hopper. In this area are generally mounted screw elements at high transport capacity.

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Homogenizing:

this phase generally follows the melting and requires the presence of elements for the distributive mixing of the viscous floods.
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Polymer/s transport, heating and melting:

one more or more barrels are foreseen. At their inside, there are transport elements of proper geometry and length apt to generate a rapid thermal increase through the shear stress and, in this way, to melt or soften the polymer. The entity and the time of shear application depend on the polymer thermal and rheological features.


Additional feedings:

they are composed of a barrel having a presetting for the side introduction of additives and resins and/or an injection point for liquids. The design of the internal transport, homogenizing and melting elements depends on the nature of the materials to be fed. These additional feedings can be more than one and different among them.


Liquid injection:

device used to feed liquids, liquid resins, oils, etc., inside the barrels in contact with the melt; such liquids can be at room temperature or heated.
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Side degassing:

high efficiency, consists of a barrel having a flanged side opening (identical to the barrel side feeding module), for degassing. Such module is used with the insertion of a fume extractor composed as for the side feeder with the adding of a degassing. This systems allows to have a degassing surface always free, for the benefit of efficiency, and also to prevent the material leaking from the vent itself.


Degassing:

it consists of one or more barrels having a proper venting port and a screw profile suitable to the formation of pneumatic sealing chambers, which can have a normal or a reduced pressure (up to 10 torr in the latter case). In this area, the volatile fractions, the humidity and their air, being present in the compound, are removed.


Pumping:

this phase consists of a continuous barrels and of transport and compression elements apt to eject the material from the die-head. Finally, as far as the screw geometry is concerned, it is a most important process factor. As a matter of fact, self-cleaning, positive or negative transport capacity, material shear stress and relevant application time of this same are strongly affected by this factor.

Control systems

High level hardware and software.

In order to allow the customers to exploit the high technological content of its extruders, Maris has developed sophisticated control systems. The company has always been attentive to the use of high-quality hardware and software systems, in line with the high quality standards of machinery employed.
Particular care is taken with the insertion of its production lines within the modern industrial contexts, where each component has to be placed on line and has to be able to communicate with the connected devices such as the automatic systems for raw material moving, feeding, granulation, packing …
The network connection includes the possibility to communicate with the plant management systems in order to grant a constant analysis of production data.

Key word: technology

A tailor-made product.

Technological fruits Maris, with its co-rotating twin-screw extruders, is proud to be 100% owner of its technology. This is possible thanks to the fact that all fundamental parts are manufactured internally, with high level production and quality processes. The demonstration of this is the production of screw construction elements, in its entirety, the barrel sectors and, above all, the manufacture of their own gear-boxes.
Particular attention is paid to the search for new construction materials to be used in order to improve the performance of its extruders.
The result is extruders, whose strength is their versatility, allowing their use in a wide range of production layouts, typical of the most varied productions linked to compounding.
Maris makes productive versatility its strong point in order to provide its customers with tailor-made solutions.

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