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Extrusión de espuma. Una completa teoría de control vincula los componentes individuales de los sistemas contemporáneos de extrusión de espuma. Los ajustes en el rendimiento junto con el arranque y la parada de todo el sistema se realizan en gran medida de forma automática, reproducible y en un método de fácil manejo.
Las formulaciones típicas de materia prima para la extrusión de espuma consisten en hasta 8 componentes que deben ser procesados bajo las condiciones descritas. Los fabricantes de máquinas se enfrentan al reto de los crecientes conceptos de control y tecnologías que aseguran el desarrollo reproducible de productos semielaborados de espuma. La extrusora de doble husillo se alimenta con las materias primas poliméricas por medio de una unidad gravimétrica (alimentador con pérdida de peso) y esto determina el rendimiento de la máquina. El agente espumante físico en forma líquida se introduce en el barril con la ayuda de bombas de alta presión.
La extrusora de doble husillo es alimentada por hambre. La aceleración de los husillos dobles se puede variar dentro de límites seleccionados. La relación entre el caudal de polímero [kg/h] y la rapidez de los husillos [rpm] se define como el caudal preciso: (1) Una reducción de la rapidez de los tornillos para un caudal determinado tiene como resultado un aumento del caudal específico. La velocidad mínima por debajo de la capacidad de alimentación de la extrusora ya no es satisfactoria. Si se excede el rendimiento máximo determinado .m spez,ZE,max, la zona de alimentación se llena. Aumentar la velocidad del tornillo reduce el rendimiento específico. Normalmente, esto conduce a un aumento del calor de la masa fundida y a un acortamiento de la longitud de reserva. Dado que la longitud de reserva es fundamental para proporcionar la estanqueidad y evitar la circulación inversa del agente de soplado en esta técnica, el caudal específico incluye un límite inferior. La velocidad del tornillo no puede ser aumentada a ningún valor
El rendimiento específico de la extrusora de un solo husillo también puede establecerse de manera similar al utilizado para la extrusora de fusión. También en este caso, el caudal específico puede variar dentro de límites y por lo tanto tener alguna influencia en las temperaturas de la masa fundida junto con el nivel de presión en el sistema completo
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Foam Extrusion. A thorough control theory links the individual components of contemporary foam extrusion systems. Adjustments in throughput together with startup and shutdown of the entire system happen largely automatically, reproducibly and in a user-friendly method.
Typical raw material formulations for foam extrusion consist of up to 8 components that must be processed under described conditions. Machines manufacturers face the challenge of growing control and technologies concepts that ensure reproducible development of semi-finished foam goods.
The twin-screw extruder is fed with the polymeric raw materials by means of a gravimetric unit(loss-in-weight feeder) and this determines the machine throughput. The physical blowing agent in liquid shape is fed into the barrel with the aid of high pressure pumps.
The twin-screw extruder is starve-fed. The acceleration of the twin screws can be varied within selected limits. The partnership between polymer throughput [kg/h] and screw swiftness [rpm] is defined as the precise throughput: (1) A reduction in screw swiftness for a set throughput results in an increase in specific throughput. Gleam minimum speed below that your feeding capacity of the extruder is not any longer satisfactory. If the maximum certain throughput .m spez,ZE,max is exceeded, the feed zone becomes filled. Raising the screw swiftness reduces the specific throughput. Normally, this leads to a rise in melt heat and a shortening of the back-up length. Since the backup length is critical to give sealing and prevent reverse circulation of the blowing agent in this technique, the specific throughput includes a lower limit. The screw speed cannot be increased to any value.
The specific throughput of the singlescrew extruder can also be established in a manner similar to which used for the melting extruder. Here, too, the specific throughput can be varied within limitations and therefore have some influence on the melt temperatures along with the pressure level in the complete system.
With the aid of the specific throughputs, the control of the extruder speeds can be from the polymer throughput. A transformation in the throughput specified automatically results in a change in speed.
A typical raw material formulation for foam extrusion includes up to eight elements: the virgin polymer, additives and reclaim for cell size control, colorants and flame retardants. The amounts of the substances are specified in terms of percent, for example, for component. A comprehensive control theory links the individual components of contemporary foam extrusion systems. Alterations in throughput and also startup and shutdown of the entire system happen largely instantly, reproducibly and in a user-friendly manner.
For certain foam goods, up to three blowing agents are added. Injection takes place into the polymer melt directly, i. e. in to the barrel of the twin-screw extruder.
Maintaining constant task parameters is crucial for consistent top quality of the ultimate end product. In addition to temperature control, this means the proportions of the polymeric components especially, the blowing agents and the specific throughputs of the extruders.
Based on its percentage, control of the blowing agent could be from the polymer throughput also. This does mean a noticeable transform in the absolute move rate of blowing agent with a adjust in throughput. Knowing the individual proportions of the polymeric elements and the blowing agents, the formulation clearly is specified. Knowledge of the polymer throughput, the proportions of all materials and the precise throughputs of the two extruders, means that the essential parameters of an functioning point are defined.
Regular changes of the operating point, such as changes on throughput or startup and shutdown of the entire line, Schematic layout of a tandem system for foam extrusion. The sum of all polymeric raw components is normally 100%. The complete throughput of each specific component in [kg/h] is calculated with regards to the full total polymer throughput. To maintain proportions exactly, all factors gravimetrically are fed. Likewise, the specified sums for the blowing agents are likewise stated in percent with regards to the full total polymer throughput. The absolute ideals of blowing agents throughput are as well calculated with regards to the total polymer throughput and entered as setpoints on the metering pump controls.
Measurement of the stream rate is founded on the theory of the Coriolis drive. The total throughput of a foam tandem line is calculated because the sum total of the polymer and blowing agent throughputs, that is, the blowing agent is going to be incorporated into the total. Startup at the desired line throughput is initiated from a central control panel with the click of a mouse on a keep an eye on. The speed at which changes should be made can be preselected with the aid of a ramp function.
It is defined at the change found in polymer throughput [kg/h] per unit of time. The change then takes place on the basis of the links described above. All sequences are thus reproducible. The operator can focus on observing the product quality and adjusting the brand speed. If you loved this short article and you would like to obtain even more facts concerning plastic extruder kindly see our own webpage. Any necessary temperature improvements for individual zones happen to be either entered manually or transmitted to the machine with the previously stored formulation. All equipment parameters are recorded continuously, stored and will be shown graphically in pattern diagrams.Using these diagrams, the behavior of the processes over time could be observed and analyzed. In this way, changes in the required operating points could be monitored perfectly by the operator.
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