Service HotlineThe process flow of extrusion blow molding hollow products mainly includes four core steps: parison extrusion, mold closure and expansion, cooling and shaping, and trimming.
Detailed explanation of extrusion blow molding process
1. Parison extrusion .
Molten plastics (such as polyethylene, polypropylene, etc.) are extruded through a ring die by an extruder to form tubular parison. The thickness and length of the parison need to be pre-adjusted according to the size of the product.
2. Mold closure and inflation .
Move the hot parison into the blow molding mold, close the mold and clamp the neck of the parison, while cutting off the excess part.
Compressed air is injected into the mold to make the parison expand and adhere to the inner wall of the mold, forming the designed shape. Multi-layer blow molding requires the compounding of different materials through co-extrusion technology.
3. Youdaoplaceholder0 cooling and setting .
Maintain the expansion pressure to cool and solidify the product in the mold, ensuring dimensional stability. The cooling time depends on the thickness and thermal conductivity of the material.
4. Finishing and post-processing .
Open the mold to remove the product, cut off the flash or burrs, and carry out surface treatment (such as printing, polishing) if necessary.
5. Process Variants and technical Highlights
Youdaoplaceholder0 stretch blow molding : Before blowing, the parison is axially stretched to enhance the mechanical strength and transparency of the product. It is suitable for materials such as PET.
Multi-layer co-extrusion : By combining different materials (such as barrier layer + structural layer) to enhance functionality, the thickness of each layer needs to be precisely controlled.
Material selection : HDPE is often used for large containers, PVC is suitable for transparent packaging, and PET is mostly used for pressure-resistant food bottles.