Injection blow molding is a two stage process since the parison is produced in a separate operation. In the first process molten plastic is injected into a heated preform mold around a hollow mandrel blow tube or core rod. This is similar to insert injection molding. The workpiece for the second, blow molding, process is the preform-mandrel assembly. The preformed parison is placed in a larger mold cavity for blow molding. Between the preform production and blow blow molding processes a heated preform may be held in a temperature conditioning stage or a cooled preform re-heated. After blow molding part is stripped from the core rod at an ejection station.
- Injection Blow Molding General Processing Guidelines
Process Steps
Step 1. Injection Step 2. Blowing Step 3. Ejection |
Raw Materials
- Polyethylene (Low Density) LDPE, LLDPE
- Polypropylene PP
- Polyethylene – Terephthalate PET
- Polyvinyl chloride PVC
- Polyethylene (High Density) HDPE
These factors are critical to this process:
- Shear & temperature dependent viscosity
- Temperature-dependent tensile strength on the pin
- Tensile elongation during inflation
- Crystallization kinetics on the core pin
- Crystallization kinetics during blowing and cooling
Examples of Application
- Bottles
- Jars
- Roll-on containers