The operating temperature of calender rolls depends on the material, formulation, and processing requirements. In plastic processing, roll surface temperatures generally range from 150 to 280°C during heating and 80 to 120°C during cooling, depending on the application. Temperature control also affects sheet thickness, surface quality, material plasticization, and equipment service life.
Temperature settings for different processing stages
Plastic processing
Heating temperature: Roll surface temperatures generally range from 150 to 280°C to help the material melt and plasticize sufficiently. Appropriate temperature settings help produce plastic sheets with smooth surfaces and reduce the risk of bubbles.
Cooling temperature: For thinner plastic sheets, the roll temperature may need to be reduced to 80 to 120°C to limit deformation. Suitable pressure should also be maintained during forming.
The actual settings depend on the material formulation and process requirements. The temperature range should not be treated as a universal setting for every plastic calendering application.
Temperature requirements during shutdown and maintenance
Shutdown conditions: When the roll temperature is above 70°C, the machine should not be stopped immediately. The rolls should be cooled gradually to below 60°C to reduce the risk of deformation or bearing damage caused by thermal expansion and contraction.
Cooling rate: The specified cooling rate depends on the roll temperature.
Above 100°C, the cooling rate should not exceed 0.5°C per minute.
At or below 100°C, the cooling rate can be increased to 1°C per minute.
Following the appropriate shutdown procedure helps limit thermal stress on the rolls and related components.
Factors that affect roll temperature settings
Temperature differences between rolls
Adjacent rolls are commonly set at temperatures that increase by 5 to 10°C, depending on the process. For example, a four roll calender may use settings of 170°C, 175°C, 180°C, and 185°C.
This progressive temperature arrangement can help the material bond layer by layer and allow trapped air to escape during processing. The appropriate temperature profile depends on the material and the intended calendering process.
Relationship between roll speed and temperature
Increasing roll speed generates more shear heat during processing. To prevent excessive plasticization, the heating temperature may need to be reduced as roll speed increases.
Temperature and speed settings should therefore be evaluated together. Changing one parameter without considering the other may affect material flow and surface quality.
Material formulation
The material formulation also affects the required roll temperature. When a formulation contains low melting point resins or a high proportion of plasticizer, as in soft PVC, the roll temperature may be reduced by approximately 20 to 30°C.
Rigid PVC and highly filled materials generally require higher temperatures. The final settings should be determined according to the material characteristics and actual processing conditions.
Custom precision machining for calendering equipment
Stable roll temperature control is one part of maintaining consistent calendering quality. Equipment condition and component accuracy also affect machine operation and maintenance requirements.
Hansheng Automation provides custom precision machining for nonstandard components used in calendering and rubber processing equipment. We manufacture parts according to customer supplied drawings and the specified dimensional and structural requirements.
Our machining services also cover components for tobacco packaging and filling machinery, along with precision parts for yachts and remote control racing cars. Each component is manufactured according to its drawing and application requirements.
