What is the working principle of a blow molding machine?

The working principle of a blow molding machine is based on shaping hollow plastic parts by blowing air into a heated plastic tube (called a parison) inside a mold, causing the plastic to expand and take the shape of the mold cavity.

Here’s a simple breakdown of how it works:

1. Plastic Melting: Plastic pellets (such as HDPE, PET, or PP) are heated and melted inside an extruder or injection unit.

2. Parison Formation: The molten plastic is shaped into a tube-like form (the parison) through an extrusion or injection process.

3. Mold Closing: The parison is positioned between two halves of a mold, which then close around it.

4. Air Blowing: Compressed air is blown into the parison through a needle or a blowing pin. The air pressure forces the soft plastic outward until it fits tightly against the mold walls.

5. Cooling: The molded plastic part cools and hardens inside the mold, maintaining the shape of the cavity.

6. Mold Opening and Ejection: Once the part has solidified, the mold opens and the finished product is removed. The machine immediately starts the next cycle.

In short:

- Melt the plastic  

- Form the parison  

- Blow air to expand it inside the mold  

- Cool and eject the finished hollow product  

Blow molding is widely used to make plastic bottles, containers, tanks, and even some automotive parts because it’s fast, efficient, and great for producing lightweight, strong hollow objects.

Would you also like me to explain the three main types of blow molding (extrusion, injection, and stretch blow molding)? It could make the concept even clearer! 🌟