In today’s manufacturing environment, plastics are being used to make everything from automotive body parts to human body parts. Each application requires a special manufacturing process that can mold the part based on specifications. This article provides a brief overview of the different types of molding and their advantages and applications.
Blow Molding – Well suited for hollow objects, like bottles
The process follows the basic steps found in glass blowing. A parison (heated plastic mass, generally a tube) is inflated by air. The air pushes the plastic against the mold to form the desired shape. Once cooled, the plastic is ejected.
The blow molding process is designed to manufacture high volume, one-piece hollow objects. If you need to make lots of bottles, this is the process for you. Blow molding creates very uniform, thin walled containers. And, it can do so very economically.
Compression Molding – Well suited for larger objects like auto parts.
The name of this molding method says everything. A heated plastic material is placed in a heated mold and is then compressed into shape. The plastic can be in bulk but often comes in sheets. The heating process, called curing, insures the final part will maintain its integrity. As with other molding methods, once the part has been shaped, it is then removed from the mold. If sheeting plastic material is used, the material is first trimmed in the mold before the part is removed.
This method of molding is very suitable to high-strength compounds like thermosetting resins as well as fiberglass and reinforced plastics. The superior strength properties of the materials used in compression molding make it an invaluable process for the automotive industry.
Extrusion Molding – Well suited for long hollow formed applications like tubing, pipes and straws.
While other forms of molding uses extrusion to get the plastic resins into a mold, this process extrudes the melted plastic directly into a die. The die shape, not a mold, determines the shape of the final product. The extruded “tubing” is cooled and can be cut or rolled for shipment.