Description
Plastic blow molding is a manufacturing process that is used to create hollow plastic parts by inflating a heated plastic tube until it fills a mold and forms the desired shape.
The raw material in this hollow blow molding process is a thermoplastic in the form of small pellets or granules, which is first melted and formed into a hollow tube, called the parison. The parison is then clamped between two mold halves and inflated by pressurized air until it conforms to the inner shape of the mold cavity.

Advantages of Hollow Blow Molding
1. Can form complex shapes with uniform wall thickness
2. High production rate
3. Low labor cost
4. Little scrap generated

Application of Plastic Blow Molding
1. Parts made from blow molding are plastic, hollow, and thin-walled, such as bottles and containers that are available in a variety of shapes and sizes.
2. Small products may include bottles for water, liquid soap, shampoo, motor oil and milk, while larger containers include plastic drums, tubs, and storage tanks.

Hollow Blow Molding

Plastic Blow Molding Process
1.Extrusion blow molding
An extruder uses a rotating screw to force the molten plastic through a die head that forms the parison around a blow pin. The parison is extruded vertically between the two open mold halves, so they can close on the parison and blow pin. Pressurized air flows through the blow pin to inflate the parison. This is the most common type of blow molding and is used to manufacture large quantities of relatively simple parts.
2.Injection blow molding
The molten plastic is injection molded around a core inside a parison mold to form the hollow parison. When the parison mold opens, both the parison and core are transferred to the blow mold and securely clamped. The core then opens and allows pressurized air to inflate the parison. This is the least commonly used method because of the lower production rate, but is capable of forming more complicated parts with higher accuracy. Injection blow molding is often preferred for small, complex bottles, such as those in medical applications.
3.Stretch blow molding
The parison is formed in the same way as injection blow molding. However, once transferred to the blow mold, it is heated and stretched downward by the core before being inflated. This stretching provides greater strength to the plastic. Stretch blow molding is typically used to create parts that must withstand some internal pressure or be very durable, such as soda bottles.

Common Materials of Plastic Blow Molding

Material name	Abbreviation	Description	Applications
Polyester - Thermoplastic	PBT, PET	Rigid, heat resistance, chemical resistance, medium/high cost	Automotive (filters, handles, pumps), bearings, cams, electrical components (connectors, sensors), gears, housings, rollers, switches, valves
Polyethylene - Low Density	LDPE	Lightweight, tough and flexible, excellent chemical resistance, natural waxy appearance, low cost	Kitchenware, housings, covers, and containers
Polyethylene - High Density	HDPE	Tough and stiff, excellent chemical resistance, natural waxy appearance, low cost	Chair seats, housings, covers, and containers
Polypropylene	PP	Lightweight, heat resistance, high chemical resistance, scratch resistance, natural waxy appearance, tough and stiff, low cost.	Automotive (bumpers, covers, trim), bottles, caps, crates, handles, housings
Polyvinyl Chloride - Plasticised	PVC	Tough, flexible, flame resistance, transparent or opaque, low cost	Electrical insulation, housewares, medical tubing, shoe soles, toys