Injection Molding

Injection molding is one of the most important fabrication processes for the plastics industry. Today, it is almost impossible to do anything without using injection molded parts. You can find them in automotive interior parts, electronic housings, medical equipment, compact discs, and sport products and even in your clothes.

Injection molding is used to fabricate pallets, toys, tools, crates, and pails, food containers, drink cups, and milk bottle caps, among others.

Some advantages of Injection Molding are:

• High production rates
• Design flexibility
• Repeatability within tolerances
• Can process a wide range of materials
• Relatively low labor
• Little to no finishing of parts

Injection blow molding is a process used for the production of hollow objects in large quantities. The main applications are bottles, jars and other containers. The Injection blow molding produces bottles of superior visual and dimensional quality compared to extrusion blow molding. The process is ideal for both narrow and wide-mouthed containers and produces them fully finished with no flash.

Method

The method for injection blow molding has three phases. The first phase is an extruder barrel and screw assembly which melts the polymer. Next the molten polymer is fed into a manifold where it is injected through nozzles into a hollow, heated preform mold. Finally the preform mold forms the external shape and is clamped around a mandrel (the core rod) which forms the internal shape of the preform. The preform consists of a fully formed bottle/jar neck with a thick tube of polymer attached, which will form the body.

The preform mold opens and the core rod is rotated and clamped into the hollow, chilled mold. The core rod opens and allows compressed air into the preform, which inflates it to the finished article shape.

After a cooling period the blow mold opens and the core rod is rotated to the ejection position. The finished article is stripped off the core rod and leak-tested prior to packing. The preform and blow mold can have many cavities, typically three to sixteen depending on the article size and the required output.