In the blow molding process, commonly used oil-free piston air compressor, two-stage oil-free screw (water lubrication) compressor or screw and piston compressor unit the specific choice needs to be considered in combination with process pressure requirements, production scale, energy efficiency and maintenance costs. The following is a specific analysis of different types of air compressors:
1. selected according to process pressure requirements
- low pressure blow molding (15-25bar) some small blow molding equipment or specific processes may use low-pressure air compressors, but it is necessary to ensure that the pressure stability meets the production requirements.
- Medium pressure blow molding (25-35bar): Common in PET bottle blow molding and other processes, need to be equipped with a medium pressure air compressor, such as oil-free piston or two-stage compression screw machine.
- High pressure blow molding (35-40bar and above): For special materials or high-precision blow molding, high-pressure screw and piston compressor unit or special high-pressure air compressor should be selected.
2. selected by production scale and efficiency
- small blow molding production line: Piston air compressors are suitable for small businesses or low production scenarios due to their low cost and simple maintenance.
- large automatic production line screw air compressor (especially oil-free water lubrication model) high efficiency, strong stability, can meet the demand of continuous production, and compressed air quality is better.
3. selected by energy efficiency and operating cost
- energy efficiency priority screw air compressor (especially the variable frequency model) can automatically adjust the power according to the amount of gas, the energy saving effect is remarkable, and the long-term operation cost is lower.
- Maintenance costs: The piston air compressor has many vulnerable parts and high maintenance frequency; the screw air compressor has a simple structure and relatively low maintenance cost.
4. selected by compressed air quality
- oil-free requirements the blow molding process is sensitive to the oil content of the compressed air, so it is necessary to choose an oil-free air compressor (such as oil-free piston type or water-lubricated screw type) to avoid oil pollution.
- Drying and Filtration: Air cooling dryer and precision filter are required to further remove moisture and impurities and ensure the quality of compressed air.
5. Recommended Scheme
- PET bottle blow molding: It is recommended that the two-stage oil-free screw (water lubricated) compressor or screw plus piston compressor unit, the pressure can reach 3.5-4MPa, meet the demand of stretch blow molding.
- Universal blow molding process: Oil-free piston air compressor (pressure 2.5-3.5MPa) is cost-effective, suitable for small and medium-sized enterprises.
- Large production line screw air compressor is used in parallel or series combination to realize high pressure and large flow gas supply and improve production efficiency.
