Leading Blow Moulding Companies

What is Blow Molding?

Blow molding is a method of producing hollow plastic pieces by shaping and connecting them. It can also be used to make glass bottles or other hollow objects. While injection molding and rotational molding are more precise methods of plastic molding, blow molding offers the advantage of high-volume capacity, efficiency, and relatively low costs.

Blow molded products can be formed from standard and common die-cast cavities, but custom blow molding can be used to create specific products for unusual and unique purposes. It is the most well-suited method for forming hollow plastic parts. Thousands of applications benefit from the versatility of the process combined with the strength and durability of the products.

Blow Molding Process

The plastic is melted down and formed into a parison clamped into a mold. A blow pin is then used to force compressed air into the parison, and the molten plastic expands to fit the shape of the cavity.

Controlled and constant airflow is essential to the quality of the final product since varying wall thicknesses compromise the strength and durability of the product. Blow molders have to ensure the constant expansion of the plastic in the mold to achieve uniform wall thickness in the product.

The cavity is cooled, usually by conduction, and the hardened plastic product is removed from the mold, sometimes with the assistance of ejector pins. The process usually takes seconds; blow molding machines can produce high volumes of durable plastic products in short periods with minimal finishing requirements.

Types of Blow Molding Techniques

Injection blow molding, extrusion blow molding, and stretch blow molding are the three most common types of blow molding, which differ during the preform stages. Each variation has specific advantages and application uses, yet the basic process of blow molding is straightforward.

Injection Blow Molding

Injection blow molding is a process in which a plastic preform is injection molded and then transported on a core rod to a blow mold station. Blown air enters through the core rod and lifts the hot preform material off the core rod, forming it to the design of the female blow mold by air pressure.

The blow molds open when the blown plastic bottle has reached the desired shape, and the core rod containing the blown bottle travels to the stripping station, where the blown bottle is stripped off the core rod. After that, the procedure is repeated.

Extrusion Blow Molding

In extrusion blow molding, a plastic material feedstock is supplied through a hopper onto a feeding transfer screw. This feeds material into a specifically designed blow molding die, which guides the flow of material to make a parison, an extruded hollow tube.

Gravity causes this parison to fall until it reaches a process-specific length, causing the mold to wrap around it and seal the bottom edge (giving it the distinctive end seal). A cutting knife splits the parison's open top, and a blow pin advances to the tool's top, inflating the parison against the tool cavity's walls.

The cooled tool walls solidify the molding, which is evacuated after a predetermined time. Finally, the process is repeated with the newly extruded mass of molten glass.

Injection Stretch Blow Molding

Molten polymer flows into the injection cavity via the hot runner block, forming the required shape of the preform with an inner diameter produced by a mandrel (the core pin) and an outer diameter produced by the injection cavity. After a predetermined amount of time, the injection molds and core pins are removed, and the preform supported in a neck carrier is turned 90 degrees.

The preform is ready for stretching and blowing to the finished shape once it has been conditioned to the proper temperature. Once the preform is within the blow mold region, the molds are closed, a stretch rod is supplied to stretch the preform longitudinally, and the preform is blasted circumferentially utilizing two levels of air pressure.

The molds open once a certain amount of cooling time has passed, and the preform is extracted using drop chutes or robotics. In practice, the four phases are completed simultaneously by rotating a carousel of molds.

Choosing the Right Blow Molding Manufacturer

To make sure you have the most positive outcome when purchasing Blow Molding from a Blow Molding Manufacturer, it is important to compare at least 5 or 6 Manufacturers using our list of Blow Molding manufacturers. Each Blow Molding Company has a business profile page that highlights their areas of experience and capabilities and a contact form to directly communicate with the manufacturer for more information or request a quote. Review each Blow Molding business website using our patented website previewer to get an idea of what each business specializes in, and then use our simple RFQ form to contact multiple Blow Molding businesses with the same quote.