Barrels for co-rotating screws (parallel and conical) can be made from one piece or can be also modular.
Barrels for counter rotating screws (parallel and conical) can be made only from one piece, modular type is not possible.
The barrel performs two basic functions:
- Heat transfer required to melt the plastic granulate
- After the granulate is melted the liquid plastic is held in the barrel before injecting the plastic into the mould
When designing the technical solution, it is necessary to place great emphasis on the selection of suitable materials for the production of the barrel in relation to the type of plastics to be processed and possible additives – this parameter is directly proportional to the lifespan of the barrel.
The barrel can be divided into two basic categories in terms of the production process:
Suitable for the production of plastics that do not contain abrasive or corrosive additives.
Nitriding = saturation of the steel surface with nitrogen at a temperature of 500 – 600 °C (depending on the selected steel)
Suitable for processing plastics containing abrasive and corrosive additives.
The composition of the bimetallic layer is selected based on the specification of the plastics to be processed on the IMM.
Production of the bimetallic barrel briefly in points::
- Machining of forged steel bar to the required outer diameter
- Drilling of the inner diameter to the given diameter including the reserve for the bimetallic layer
- Application of powder (specially prepared mixture) inside the barrel and closing both sides of the barrel
- Insert the barrel into the centrifugal furnace and heating to the required temperature
- After heating to the required temperature, the barrel is rotated at high speed, the molten mixture is now spread over the inner wall of the barrel by centrifugal force and a bimetallic layer is formed
- After cooling, the barrel is drilled to the required diameter and a control measurement is performed
- After the final drilling, there is an output dimensional inspection and quality control (recorded and confirmed by the responsible employee of the quality management department)