What is Blow Molding?
The basic blow molding technology evolved from glass blowing techniques developed by early Egyptian glass blowers thousands of years ago. In contrast modern day plastic blow molding is high-tech and very automated.
Plastic blow molding can be described as a manufacturing process which uses air pressure to inflate thermoplastic materials within a mold. The design and creation of the mold itself is the most time consuming part of the process. Blow molding is used in the production of hollow, seamless plastic products, such as water bottles, pharmaceutical containers, garbage cans, fuel tanks, and any plastic container with a hollow chamber.
How Does it Work?
Extrusion Blow Molding – The process begins with the melting down of raw plastic material, which is extruded through a die and shaped into a hollow tube called a parison. It is then clamped between two mold heads, which come together to form a sealed cavity. The parison is inflated with air, forcing the softened plastic evenly into the walls of the mold. The plastic solidifies as it cools and is formed into the shape of the mold cavity. The cavity opens up and the part is ejected. The entire process is automated, and may continue down the line for labeling.
Injection Blow Molding – This process involves the injecting of molten plastic into a mold at high pressure. The molten plastic is injected via the injection unit, where a reciprocating screw turns, forcing the plastic into an injection mold. A parison(hollow plastic tube) is formed around the blowing rod, which is inserted into a blow mold. Air is released into the blowing rod and through an air valve into the parison. the air pressure causes the parison to expand within the mold cavity where it quickly cools, and hardens. The mold opens and ejects the fully formed plastic part.