The extruder barrel screw is a common part of 3D printers

The extruder barrel screw is a common part of 3D printers. However, its design is not simple. Various factors affect the life of the screw, including the lubrication film and the Bimetallic screw.

Extruders
The extruder barrel screw is a critical part of the plastics production process. The screw's axial movement is controlled by the motor to convey the polymer to the channel. The effect of heat resistance in the barrel causes the polymer to melt and be pushed forward into the mold. Modern material technology has made the use of difficult-shaped materials more common. These materials have exceptional thermal and mechanical properties. Developments in barrel and screw design have complemented each other and a number of new designs have been developed to facilitate processing of this material.

When designing an extruder, it is important to select the correct screw elements and barrel sections. The choice of these components can affect the extruder's functional performance, including the degree of mixing, melting, and metering of the finished product. It may be necessary to choose several different systems, which will likely be governed by economics, availability, and flexibility. However, there are several other considerations to consider when selecting a screw and barrel system.

Bimetallic screw
The use of recycled material in extrusion has become a common practice. However, the recycled material often has unsavory properties compared to the smooth and lubricated function of a Bimetallic extruder barrel screw. To ensure a more sustainable environment, end users often choose to use recycled materials. These materials often contain particulates and impurities and may not be as clean as virgin material. Additionally, they are often made of recycled plastics. These factors combine to cause additional wear and tear on the screw barrel.

Grooved barrel sections
A grooved barrel section has a continuous depth of 2.8 mm in the feed opening, and the taper angle diminishes to zero along the residual length of 220 mm. The geometrical information on grooves is given in Table 2.

A grooved feed section is an important component of the extruder screw. It reduces melt temperature and improves solids conveying. The grooved barrel section increases the pumping action of the extruder and lowers the energy required to pressurize the extruder screw. It is also a great way to reduce the amount of energy put into the polymer. It is important to note that a grooved barrel section is not necessarily a must-have feature for an extruder.

Shear stress
The shear stress on an extruder barrel screw is the force exerted on the solid by the rotating extruder barrel. The material is accelerated into the progressively narrowing channel 126 due to drag flow. The relative motion of the screw and the barrel surface results in axial pressure increases and deflections. Consequently, the pressures in the groove are increased. The axial pressure increases are proportional to the changes in material velocity.

The shear stress on the extruder barrel screw is measured at the bottom of the extruder and is an important parameter when calculating the horsepower required to drive the screw. In addition, it is crucial to understand the solid bed down-channel velocity so that you can adjust the screw and barrel to ensure consistent performance. However, due to the pseudoplastic nature of the polymer and its strong temperature dependence, the calculation is complicated.

Flow surging
Flow surging on the extruder barrel screw is a common problem. This phenomenon is caused by a variety of factors, including variations in feed-entry, plugging in the melting section, or an inadequately filled metering section. The causes of surge vary depending on the type of polymer and process. Flow surging on the extruder barrel screw can be difficult to diagnose, but proper understanding of its causes and how to control it is essential.

A high-resistance extruder barrel is capable of sustaining the pressure required to extrude polymer. Using a heated feedstock reduces temperature variation between the solids bed and the melt pool, which helps improve consistency and melt temperature homogeneity. Using a reduced screw speed will prolong the time required for heat conduction into the solids bed. High-speed extruders are more susceptible to this phenomenon, as higher speed increases the risk of a vortical fountain flowing through the screw.