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Plastic extrusion is a manufacturing process used to create long objects of a fixed cross-sectional profile. The material, like plastic, is drawn through a die of the target profile shapes and forms a continuous length of that shape. Vacuum is used during the process of plastic extrusion to create a variety of items like custom plastic profiles, extruded rods and tubes, piping, edges, molding, specialty plastic coatings, and multi-material extrusions known as co-extrusions.
Nash recognizes the varying vacuum demand required by the plastic extrusion industry; therefore, our vacuum pumps can be configured to handle the water carryover associated with sizing and calibration tables as well as optimizing for extruder barrel venting.
Plastic extrusion begins with plastic chips, beads or pellets - often referred to as resin. The resin, along with additives such as colorants and UV inhibitors, is fed from a hopper into the barrel of the extruder.
The resin is pushed by the screw extruder towards the barrel where it is heated at around 400°F (200°C) to a molten state. As the material nears the end of the screw, the melt is unpressurized, and NASH vacuum pumps are used to vent the trapped gases. The gases need to be vented because they could create voids and other imperfections in the finished product.
Once the melted plastic leaves the barrel, it travels through a screen pack and removes any contaminants. The screens are reinforced by breaker plates, which are thick metal pucks with many holes. The plates can withstand the high pressure at that stage of the process, which can exceed 5,000 psi. They also serve to create backpressure in the barrel, which is required for uniform melting and proper mixing of the resin and it converts the "rotational memory" of the material to "longitudinal memory," adding strength.
Once through the breaker plate, the plastic - still in its molten state - enters the die, which gives it the final profile. The extrudate is then cooled and solidified as it is pulled through a water tank. In a tube or pipe extrusion line, a sealed water bath has a carefully controlled vacuum applied to keep the molten tube or pipe from collapsing.
NASH liquid ring vacuum pumps are ideal for this application because they handle intermittent and continuous streams of water without damage or loss of vacuum level and are tolerant of plastic resin carryover.
The Vectra SX eliminates the need for traditional arrangements of separate air and water removal pumps.
Nash is a leading global provider of engineered vacuum solutions and has supported the growing plastic extrusion industry for several decades. The NASH Vectra series is rugged in construction with lower water consumption and associated utility costs. The Vectra series is the ideal solution and supports customer’s specific demands and offers:
NASH liquid ring vacuum pumps are tested prior to installation. Thus, ensuring top quality and avoiding operational downtime. Nash is the leading global manufacturer of highly-engineered vacuum products.
Backed by over 110 years of experience, NASH certified experts provide aftermarket support with maintenance, service, parts, and repair. Service centers are globally located to protect your vacuum system investment and provide quality, reliable and efficient solutions.
