Of the many different machines used for manufacturing products, the blow molding machine is one of the most fascinating and useful. Known as extrusion blow molding, the simple explanation as to how this blow mold design works is that air is blown into a parison, shaping the hollow bottle as it inflates. However, there is much more to the plastic extrusion blow molding process.
The Blow Molding Process
The extrusion blow molding process produces plastic bottles of various sizes and shapes. Millions of people use these bottles daily for soda, water, cleaning products, food, and more. With this process, low-pressure air of around 25 to 150 psi is forced into a parison. Multiple materials are used, including Low-Density Polypropylene (LDPE), High-Density Polyethylene (HDPE), Polyvinyl Chloride (PVC), Polyethylene Terephthalate (PET), and Polypropylene (PP).
- A parison with a conventional downward extrusion is inserted into the mold cavity until reaching the required length.
- The neck ending catches and holds while the bottom end pinches closed as the tube closes.
- A blow-pin is interested into the neck end of the hot parison while compressed air inflates it to the shape of the mold cavity. Simultaneously, the process creates the threaded opening.
- Once the mold sufficiently cools, it opens, ejecting the finished bottle along with excess plastic that was trimmed off from around the neck and bottom portions.
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