Extrusion blow molding equipment can be categorized into two types: multi-layer hollow forming and single-layer hollow forming, depending on the blown products, plastic materials, and extruded plastic preforms. Currently, the most commonly used extrusion blow molding machines are multi-layer hollow forming machines and single-layer hollow forming machines. Both types feature continuous and intermittent extrusion methods. They can also be classified based on the number of mold clamping stations into single-station, double-station, and double-station, with single-station and double-station machines being the most prevalent.

As the research and development of hollow-forming machines progresses and the market expands, we are beginning to see the emergence of high-speed production lines that utilize multiple hollow-forming machines in a coordinated manner. With the increasing concentration in the blow molding product industry, these high-speed, high-output fully automated digital control hollow forming machine production lines are set to become more widespread and developed.

(1) Continuous Single-Station Blow Molding Equipment

In a continuous single-station hollow forming machine, the motor drives the extruder for continuous extrusion. After the preform is extruded, the single-station mold clamping mechanism moves downward. Once the perform is in position, the mold clamps the plastic preform and moves outward. An upper blowing rod then inserts from above into the preform’s opening, introducing compressed air to inflate the preform into the desired shape. Meanwhile, the extruder continues to extrude the preform.

After the product cools and solidifies, the mold clamping mechanism opens, allowing the product to be demolded, while the next preform is already being extruded into position. The clamping mechanism then returns the mold to the head for the next cycle. This continuous single-station hollow forming machine is particularly suitable for molding blow-molded products with a volume of less than 5 liters and smaller production batches.

(2) Continuous Double-station Blow Molding Equipment

The continuous double-station hollow forming machine is equipped with a single extruder and die head, two sets of mold clamping mechanisms, and an upper-blowing device, along with two identical molds. During operation, the motor drives the extruder to continuously extrude, while the die head keeps pushing out the plastic preform. One station’s mold clamping mechanism moves the mold downward towards the die head, capturing the preform and then moving it outward. The upper blowing rod inserts into the preform’s neck, introducing compressed air to inflate and shape the preform.

As the extruder keeps churning out preforms, the other station’s mold clamping mechanism shifts the mold down towards the die head, capturing the extruded preform and moving it out. Similarly, the upper blowing rod inserts into the preform, and the compressed air inflates and shapes it. At this point, the product from the first station has cooled, set, and been demolded, allowing it to move down again. Once the preform is in position, the next work cycle begins.

This continuous double-station hollow forming machine is particularly suitable for blow-molded products with a volume of less than 30 liters and larger batch sizes. Currently, this machine type is evolving towards high-speed operations, automatic trimming of product flash and scrap, automatic product inspection, automatic conveying, and automatic packaging. It can produce up to 9 layers of products, with the die head and molds reaching up to 12 units, and multiple machines can be connected to form a large-scale blow molding production line.

(3) Intermittent Single-Station Blow Molding Equipment

The intermittent single-station hollow forming machine operates as follows: the motor drives the extruder screw through a gearbox, pushing heated plastic melt into the storage hopper. Once the material reaches a preset level, the servo-hydraulic cylinder at the top of the hopper moves the core mold downwards, while the main hydraulic cylinder pushes the material out through the compression piston, forming a controllable plastic shape. When the extruded plastic reaches the desired length, the mold-closing mechanism equipped with a mold begins to close and inflate the shape. Meanwhile, the extruder continues to operate, replenishing the hopper for the next cycle. After the product cools and solidifies, the mold-closing mechanism opens the mold, allowing for demolding and retrieval of the product, before entering the next working cycle.

This type of intermittent single-station hollow forming machine is available internationally in specifications ranging from 5L to 20,000L. The domestic hollow-forming machine manufacturing industry also offers a variety of equipment capable of producing blow-molded products and related industrial blow-molding components up to 2,000L.

So far, the large-scale blow molding machines designed and manufactured by Yankang can produce plastic containers with a volume of up to 20,000L. Blow molding machines with larger volumes and heavier unit weights are also under development.