The most basic form of manufacturing blow molding is through the extrusion method.
What is the Extrusion Process of Blow Molding?
The plastic is injected from the extruder as a large tube of molten plastic. This extruded plastic is then molded and set in molds that have been cooled with water. Air is then injected into the molds after they are sealed. This air is introduced from the side in some molds.
Other mold types have an air injection point at the neck of the mold. This air expands the plastic to the inside of the mold to form the material into its proposed ridged shape when it cools. The process resembles the simple process of inflating a balloon inside of various bottles of predetermined shapes and sizes.
How Does an Extrusion Blow Molding Machine Work?
There are extrusion blow mold machines that can produce bottles of various sizes and shapes both in the body of the bottle and in neck sizes at an explosive rate of approximately 350 bottles per hour. This explosive production is facilitated by the machine’s ability to be adjusted in wide ranging, minute, and graduated increments.
The amounts can be as small as grams. These machines are commonly much more economical than injection blow molding machines and can be manufactured much quicker.
Advantages to Extrusion Blow Molding Manufacturing
Other advantages include very high production, less expensive tooling, and they are widely available and through multiple dealers. However, they possess a higher scrape rate and trimming the excess plastic can be difficult. Wall thickness is less controllable in extrusion blow mold machines also, but they are able to process various plastics. Additionally, they require very small startup costs, and many extrusion blow machines can produce very small runs.