Classification and related applications of blow molding machines and hollow blow molding machines

Blow molding machines can be divided into three categories: extrusion blow molding machines, injection blow molding machines, and special-structure blow molding machines.

Extrusion blow molding machines are a combination of an extruder, a blow molding machine, and a clamping mechanism. They consist of the extruder, a parison die, an inflation device, a clamping mechanism, a parison thickness control system, and a transmission mechanism. The parison die is a key component in determining the quality of blow-molded products and is typically classified into side-feed and center-feed types. Accumulator-type parison dies are often used for blow molding large products. The accumulator capacity ranges from 1 kg to 240 kg. The parison thickness control device is used to control the parison wall thickness, with up to 128 control points, typically 20 to 30. Extrusion blow molding machines can produce hollow products with volumes ranging from 2.5 ml to 104 l.

Injection blow molding machines are a combination of an injection molding machine and a blow molding mechanism, including a plasticizing mechanism, hydraulic system, control electronics, and other mechanical components. Common types include three-station and four-station injection blow molding machines. Three-station machines have three stations: preform, blow molding, and demolding, with each station spaced 120 degrees apart. Four-station machines have an additional preform station, with each station spaced 90 degrees apart. There are also two-station injection blow molding machines with stations spaced 180 degrees apart. Plastic containers produced by injection blow molding machines are precisely dimensioned and require no secondary processing, but mold costs are higher.

Special-structure blow molding machines use sheet material, molten material, and cold billets to form hollow bodies with specific shapes and applications. Due to the varying shapes and requirements of the products being produced, the structure of the blow molding machine varies.

Classification of Blow Molding Machines

Blow molding machines can be divided into continuous extrusion blow molding machines and intermittent extrusion blow molding machines based on their discharging method.

1. Continuous Extrusion Blow Molding Machine

This machine continuously extrudes a tube billet from an extruder. Its advantages include simple molding equipment, low investment, and ease of operation. It is currently the basic molding method widely adopted by small and medium-sized enterprises in China. Continuous extrusion blow molding processes are divided into three types: reciprocating, rotating, and rotary.

In a reciprocating continuous extrusion blow molding machine, the parison is continuously extruded by the extruder. When the parison is sufficiently long, the blow mold moves from the blowing and cooling station to a clamping station under the die head to hold the parison, and then returns to the blowing station. The reciprocating motion of two molds, located on the left and right sides of the die head, ensures the continuity of the production process.

In a rotating continuous extrusion blow molding machine, a reversing valve is used at the front end of the extruder to control the flow of the melt, allowing the melt to alternately extrude the parison through the die heads on both sides of the extruder, achieving continuous production.

In a rotary continuous extrusion blow molding machine, the extruder continuously extrudes the parison. After being clamped by the die, the parison is transferred around the axis of the rotary table to the blowing, cooling, mold opening, and product removal stations, ensuring a continuous process. The blow molding mold can also be set up with a horizontal turntable.

2. Intermittent Extrusion Blow Molding Machine

This involves an extruder continuously squeezing molten, plasticized material into a storage chamber. When the desired amount of material is in the chamber, the material is rapidly pushed out.