PET Bottle Blow Molding Process: Simple & Complete Guide (From Preform to Finished Bottle)

Introduction

PET bottles are widely used for water, beverages, oil, and daily chemicals. This article will explain the entire production process in simple and clear terms.

1. Preform Loading & Arranging

First, put PET preforms (small plastic tube with neck) into the machine. The automatic feeder will arrange preforms neatly with the neck upward and send them to the heating area. This step keeps production smooth and avoids jams.

2. Preform Heating

Preforms go into a heating oven with infrared lamps. The machine heats the preform body evenly to make it soft and easy to shape. The neck is kept cool to maintain its shape and thread. Uniform heating ensures the final bottle has stable thickness and good transparency.

3. Mold Closing

The heated preform is sent to the mold. The mold closes tightly to fix the preform in place. The inside shape of the mold decides the final bottle size and appearance.

4. Stretching & Low-Pressure Blowing

A stretching rod pulls the preform downward to lengthen it. At the same time, low-pressure air starts to blow the preform outward. This step makes the material distribute evenly.

5. High-Pressure Blowing

Then high-pressure air is sent in quickly. The soft preform expands fully and sticks closely to the mold, forming the complete bottle shape. This step makes the bottle strong and clear.

6. Cooling & Shaping

The mold cools the bottle rapidly with circulating water. The bottle becomes hard and keeps its shape. Good cooling prevents shrinking and deformation.

7. Mold Opening & Bottle Taking Out

After cooling, the mold opens. The finished bottle is automatically taken out and sent to the conveyor belt.

8. Inspection and Finished Product Output

Check the bottle. Remove bad bottles (broken necks, dirty, deformed) and send the good bottles to the next line for filling, labeling, or packaging.

Conclusion

The PET bottle blow molding process includes 8 simple steps: feeding → heating → mold closing → stretching → blowing → cooling → demolding → inspection. Every step is controlled accurately to make high-quality bottles. Zego Machinery provides reliable blow molding machines and full technical support to help you run production easily.