Under the graphical representation of the power curve, the totalised power is plotted along the screw length of an extruder. This representation provides a detailed analysis of the energy influences and the mechanical power acting on the materials during the entire plasticising process. The screw is shown in the calculation position, which is relevant for the power calculation. This information is essential for understanding and optimising the operating parameters of a screw extruder in plastics processing.

The graph shows various important performance values that are decisive for the operation and efficiency of the screw extruder. The calculations start from the first heating zone and cover the entire length of the screw. The following performance parameters are recorded in the graphical representation:

• Drive power: The drive power represents the mechanical energy provided by the extruder's motor. It is used to set the screw in rotation and thus enable the material flow, shearing and melting of the plastic. This power is directly proportional to the speed and torque exerted by the screw on the material.
• Torque: Torque is another critical parameter that describes the force exerted on the material by the screw rotation. It is closely linked to the drive power and significantly influences the degree of shear of the material, especially in the zones with high compaction or with highly viscous polymers. High torques are often necessary to process materials that are difficult to melt or highly viscous.
• Heating power: The heating power describes the energy supplied by the heating zones along the extruder barrel. This power contributes significantly to the heating of the material and supports the melting process. In the diagram, the heating power is often shown as a separate curve or as part of the total power. It varies along the length of the screw depending on the thermal requirements of the process and the specific heating strategy.
• Total power: The total power is the sum of the various power contributions that are introduced into the process both mechanically (through drive power and torque) and thermally (through heating power). It represents the total energy required to effectively operate the plasticising process in the extruder. A precise analysis of the total power provides information about the energy consumption and efficiency of the extruder.
• Specific drive power: The specific drive power is a characteristic value that relates the drive power to the processed material volume. It is a measure of how much energy is applied per unit mass of plastic being processed. This value is particularly important for evaluating the energy efficiency of the process and can serve as an indicator for optimisation potential.

The power calculation usually starts at the first heating zone of the screw extruder. This starting point is chosen because it is at this point that the screw begins to interact significantly with the material, both mechanically and thermally. The calculations take into account both the mechanical energy transferred by the screw and the thermal energy provided by the heaters. The combination of these two energy sources is decisive for the entire plasticising process and the associated performance curve.

The totalised power curve along the length of the screw generally shows a continuous increase in the amount of energy applied to the material. Typical features of the curve are:

• A moderate increase in output in the area of the first zones in which the material is preheated and compacted.
• A stronger increase in power in the areas where the material is melted. This is the area where both the mechanical shear energy and the heating energy increase significantly to support the melting process.
• Plateaus or stabilisation zones can occur when the heating zones keep the material temperature constant and no additional mechanical compaction or shearing is required.
• A flattening of the curve can be observed at the end of the screw length, especially in extruders with degassing zones or special shear segments where the material does not require any further significant energy input.

• Tab system
• Screw
• Multigraphics
• Pressure profile
• Melting profile
• Temperature profile
• Power profile
• Residence time
• Wall shear stress
• Mixing behaviour
• Material degradation
• Shear deformation gradient and shear rate
• Drag-pressure flow
• Short report
• Long report