The plastic industrial sector is a high energy user and manufactures several fundamental industrial materials. It utilizes over one hundred techniques and process variations to manufacture a vast array of different plastic products.

There are four common plastics production functions: moulding, calendaring, extrusion and coating, accounting for over 90% of plastics volume. The majority of plastics production occurs through injection moulding, thermoforming, extrusion and blow forming. Energy saving potential in the plastics sector is very high, and typical savings with best practices can be over 40% of energy usage and cost. Contact us for more information.

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Average specific energy consumption in kWh/kg

1. Injection moulding is essentially a basic extrusion process which is followed by another process of moulding. This involves heating and cooling of a large mass of metal that forms the mould, plus the energy needed to close the mould. There is an often an additional downstream operation, including complex assembly, occasionally in clean room environments, which accounts for the higher site specific energy consumption or SEC.
2. Pipe and profile extrusion not only has complex downstream operations but often involves the storage and handling of large hollow products, sometimes with welding, trimming and assembly operations, all of which add to the increased energy usage.
3. Vacuum thermoforming is first a sheet extrusion process, then the sheet is reheated and formed under vacuum in a mould. The items produced are generally thin-walled and lightweight. Additionally, when producing multiple circular items from a sheet, the excess material is recycled, adding to the consumption of energy.
4. Rotational moulding essentially has to heat and cool the large surface area of a metal mould for every hollow article produced. The mould is often heated by hot air circulating around the rotational mould, which is sometimes smaller than the chamber, thus reducing the energy efficiency even further. A large amount of energy is used for a small weight of the polymer, explaining the high site specific energy consumption.
5. Compression moulding is a slow process where the mould is heated and compresses while the reaction takes place. The specific energy requirement is similar to injection moulding.
6. Fibre extrusion has more downstream equipment, including stretching rolls and winding machinery, while film extrusion will include cast film and blown film, again involving more complex downstream operations.
7. Compounding, which is an extrusion process, generally involves less ancillary equipment than other extrusion processes and therefore has the lowest specific energy consumption. The polymer is heated and cooled only once, with very little else being done, apart from granulating.
8. Blow moulding is used to produce uniform hollow products in one piece, such as water bottles. A molten tube or injection-moulded preform of resin is expanded into a mould using compressed air. The finished product is hollow and takes on the shape of the mould.
9. Film or sheet extrusion is used to produce products in the shape of a flat film or sheet. The material is fed through an extruder and heated as it is forced through a flat opening. The extruded product is then cooled either by blowers or by water immersion. The extruded film or sheet may go through additional forming steps such as thermoforming.
10. Thermoforming is not identified separately because it is typically used in conjunction with film extrusion processes. A flat film is heated and either pulled by a vacuum or pushed by a plug to take the shape of the mould.

In the processing of resin into plastic products, some typical energy efficiency best practices are outlined below.

1. Process equipment, such as an injection moulding machine, sometimes requires refrigerant-based chillers to supply cold water for mould cooling. Free cooling utilizes cool outdoor conditions to removet the heat generated during processing. Free cooling can apply to injection moulding or other process areas where refrigerant based chillers are used. One side benefit is reduced wear on the chillers. Typical energy payback time ranges from two to four years.
2. Variable frequency drives are used in cooling systems for injection moulding machine cooling. Any plastics manufacturing process that requires cooling requires pumps to move the cooling water around the plant. Since the full output of the pump is not normally required, the pump can run at a slower than rated speed to meet actual process demands. This applies to injection moulding, thermoforming, and blow moulding and wherever else cooling is needed, especially in cases where process needs vary over a wide range of loads for a significant number of operating hours.
3. Plastic heater retrofits can be used to increase efficiency. Electric thermoformers cam be converted to catalytic gas fired ones, and electric oven thermoformers can be retrofitted to operate on natural gas using special catalytic heaters. Efficiency gains come from the fraction of heat that is radiant.
4. Hydraulic injection moulding machines can be replaced with all-electric ones. This solution eliminates the losses associated with the idling of the large hydraulic motors and provides for better control of clamp pressure and improved quality.
5. The efficiency of auxiliary systems, such as air compressors, cooling and extraction fans, pumping systems and barrel insulation, can be improved.

Below are the energy efficiency services we provide. Contact us for more information on these services.