Blown film extrusion is a widely used process for producing products like shopping bags and continuous sheeting. The quality and characteristics of the final film depend on the type of plastic extrusion die used. Boyu Extruder offers a range of innovative plastic extrusion dies that cater to diverse film requirements. Let’s explore three types of plastic extrusion dies commonly used in blown film extrusion: Spider die, Crosshead die, and Spiral die.
Spider Die: Complex Die Design
The Spider die is a complex die design that consists of an internal mandrel connected to the outer die wall by several “legs.” While this design offers structural stability, it can result in weld lines in the film. These weld lines, caused by incomplete healing of the polymer molecular matrix, have different optical characteristics and are weaker than the surrounding polymer. Additionally, the spider legs create a pressure gradient, leading to nonuniform die swell and thicker areas in the resulting film.
Crosshead Die: Ensuring Symmetrical Flow
The Crosshead die is a relatively simple extrusion die design that divides the melt flow into two parts at the manifold inlet and recombines them opposite a cylindrical center mandrel. However, this design can result in non-symmetrical flow. Molecules take longer to reach the opposite side of the mandrel, leading to nonuniform thickness in the resulting film. To address this issue, the inlet diameters should be varied, and different inserts can be added to minimize stagnant regions and improve uniformity.
Spiral Die: Achieving Uniform Melt Profile
The Spiral die is the most complex design among the three plastic extrusion dies. It evenly distributes the polymer melt into several feed tubes that wind around a central mandrel. As the feed tubes spin around the mandrel, their diameters gradually decrease, while the space between the mandrel and outer die walls increases. This process allows the polymer melt to layer and blend, resulting in a uniform melt profile without weld lines. The Spiral die ensures consistent film quality and eliminates the need for additional processing steps to remove weld lines.
Conclusion
Boyu Extruder’s plastic extrusion dies offer versatile options for blown film extrusion, enabling manufacturers to achieve high-quality films. Whether you require a Spider die for structural stability, a Crosshead die for symmetrical flow improvement, or a Spiral die for a uniform melt profile, Boyu Extruder has you covered. By choosing the right plastic extrusion die, you can optimize film quality and meet the specific requirements of your applications. Invest in Boyu Extruder’s plastic extrusion die today and experience enhanced film production capabilities.
