Preface

Injection blow molding is a method of producing hollow plastic bottles through injection blow molding equipment; Extrusion Blowing Molding is currently the main plastic hollow blow molding process. The two have both great similarities and many differences. These two molding processes are widely used in various fields that we come into contact with daily, such as packaging container blow molding production for food, medicine, daily chemical packaging, and petrochemical products.

1、 The production process of injection blown bottles

(1). Principle of Injection Blown Bottle Production Process

Injection blown molding process (IBM), also known as injection blown molding process. The process principle is to use injection blow molding equipment to heat and melt the resin and inject it into the blank mold to form a blank. Then, the blank attached to the core rod and with a certain temperature is transferred to another blow molding station mold, and compressed air is introduced into the blank to blow and expand the blank. Then, the required hollow product is obtained by cooling and shaping the blow molding mold. The formation of products mainly goes through the following four core processes: 1. resin plasticization and melting; 2. Injection molding blank; 3. Blow molding; 4. Product demolding.

 

（Figure 3 Station Injection (Pull) Blowing）

At present, the mainstream equipment in the injection blow molding process market is mainly horizontal three-station rotary molding equipment, with the principle shown in the above figure.

2. Characteristics of injection blowing process

Compared to the extrusion blowing process, injection blown bottles have the following process characteristics.

Advantage：

1. The product is formed in one go without any leftover materials (excluding tail trimming), resulting in a higher resin forming rate and no need for post processing, resulting in a more efficient utilization of raw materials.

2. The surface of the product is smooth and beautiful.

3. The product preform adopts injection molding, with stable quality, weight, and process.

4. The product mouth or threaded part adopts injection molding, which has higher dimensional accuracy and is suitable for producing products with high sealing requirements.

Boundedness：

More suitable for producing small capacity bottles, not suitable for producing bottles larger than 300ml.

For special-shaped bottles or flat bottles, it is not easy to form.

The net weight of the product is fixed and cannot be randomly adjusted.

The cost of mold development and maintenance is relatively high, and the cycle is long.

The production efficiency is relatively lower than that of extrusion blowing.


2、The Manufacturing Process of Squeeze Blown Bottles

Extrusion blow molding process (EBM), also known as hollow extrusion blow molding process. The process principle is to use a blow molding equipment extrusion system to heat the resin into a molten state and then extrude it from the mold head to form a tubular billet, which naturally droops into the mold to form a blow molding billet; After the mold is closed, the blowing air rod blows compressed air into the inner part of the mold through the air nozzle to expand the mold. Then, the mold is cooled and shaped to obtain the required hollow product. After the product is formed, it is automatically cut on the machine or the edge is removed through secondary processing in the later stage.

The formation of products mainly goes through the following six core processes: 1. resin plasticization and melting; 2. Extrude tube blank; 3. Blow molding; 4. Product demolding; 5. Automatic cutting of edge materials; 6. Sort and export products and leftover materials.

Squeeze blowing is divided into two major steps: extrusion and blow molding:：

step1：Extrusion embryo - mold closure

- The extrusion device continuously compresses to form a hollow tubular embryo

- When the mold is extruded to a predetermined length, the top of the mold is cut to a length suitable for a single piece, and the molds on both sides are closed

step2：Air induction - trimming and finishing

- Compressed air is injected into the mold through the core rod for blowing expansion

- The mold embryo is tightly attached to the inner wall of the mold for cooling and shaping, and the product is removed from the mold for secondary trimming

2、Characteristics of Squeeze Blowing Process

Advantage：

1、The product is formed in one step, with mature and reliable technology. The multi-station extrusion and blowing machine has higher production efficiency and strong universality.

2、Suitable for the production of various raw material resin blow molding, blow molding grade plastics (such as PE, PP) have high molecular weight. The product has high impact toughness and high resistance to environmental stress cracking.

3、The product appearance design has high freedom, the mold design and development cycle is fast, and the mold cost is relatively low.

4、Extrusion blow molding can shape products with complex, irregular, and integral shapes. Products with a large flat ratio can be produced through irregular dies. For larger hollow containers of 4L and above with hollow handles.

5、The net weight and wall thickness of the product can be randomly adjusted according to process requirements, without the need for mold repair. Save raw material costs.

6、Suitable for the application of multi-layer co extrusion technology, meeting the production needs of high barrier (2-6 layers) products.

Boundedness：

1、There may be a molding line at the mouth or bottom of the product, which has a slight impact on the appearance.

2、During the extrusion blow molding process, conventional products will have 20-30% leftover material that needs to be recycled and reused.

3、The dimensional accuracy of the product bottle mouth is not as good as that of injection blown products.

Summarize

•Injection blowing and extrusion blowing belong to different hollow container forming processes

•Each has its advantages and limitations

•According to their respective characteristics, they are applied under different usage conditions

•Two processes coexist and cannot be simply replaced by each other.