Overview of Extrusion Blow Molding Process

Blow molding production helps make three-dimensional articles made from thermoplastics materials, such as granules or powders. Two parts on the tool help contain a closed cavity. The powder is softened in a cylinder and eventually extruded into a tube.

The Basics of Using a Parison

The parison is surrounded by the mold, which is closed to seal the lower end of the parison. The wall thickness depends on the size of the parison, along with the mold. Die design is based on factors such as melt flow pattern, band length and backpressure. These features help produce bottles with wall thickness.

The understanding of temperature is important. It is required that you have optimized screw design to handle the specific polymer. The die’s uniform pressure, temperature, and viscosity should not vary.

Backpressure should merge wild lines. You should clamp the two halves around the parison and then cut it as it goes to the blow station.

Expand the parison and then cut it as it goes to the blow station. Expanding the parison into the cavity allows the cooling of mold to take place. Ejection is carried out after the mold has exhausted air.

Disadvantages of Using Molds

However, there are some disadvantages. Wall thickness decreases as the mold diameter increases. This causes thinning to occur. Since the holes cannot be moulded in, that leads to a post-molding operation. Cooling times are longer for injections because the molding is cooled from the exterior. Due to wall thickness, the cycle time may be longer and the molding may be heavier.