Detailed Analysis Report of the Double Screw Extruder

Auxiliary equipment of double screw extruder mainly includes pay-off device, straightening device, preheating device, cooling device, traction device, meter counter, spark tester and take-up device. The selection of auxiliary equipment for extruders varies with their different purposes, such as cutters, dryers, printers, etc.

Divisional and building block type barrel for double screw extruder

The obvious feature of the divisional coaxial double screw extruder is that the barrel is divisional. At the same time, the screw and the inner liner of the barrel can be combined arbitrarily.

Divisional barrel

The previous double screw extruder barrel was integral and cannot be opened. The divisional double screw extruder is a split type, which consists of upper and lower half barrels, and the lower barrel is fixed on the frame. The upper barrel is connected to the lower barrel through a worm gear reducer.

Normally, the upper and lower barrel are fastened with two rows of bolts. When it is necessary to open the barrel, simply loosen the bolts and turn the worm gearbox handle to open the barrel.

Building block type screw and barrel

The screw and barrel of the divisional double screw extruder mainframe adopt the advanced "building block type" design. The screw is composed of various forms of screw blocks set on a core shaft, and the inner liner of the barrel can be adjusted according to different screw blocks. Thus, the ideal thread element structure can be flexibly combined according to the material variety and other process requirements. This approach achieves various process phases such as material delivery, plasticizing, refining, shearing, exhausting, decompression, and extrusion. It has better solved the contradiction between the general screw universality and the sex, and achieved the goal of one machine with multiple uses and functions.

Another advantage of the "building block type" design is that worn screw and barrel components can be partially replaced, avoiding the need to discard the entire screw or barrel, thereby greatly reducing maintenance costs.

Before the double screw extruder unit is officially put into operation, the following necessary checks should be done

  • Check whether the electrical, water, gas wiring, and piping of the unit are properly and firmly connected;

  • According to the usage instructions of the equipment, add enough lubricating oil to each lubrication point of the unit;

  • Check whether the electric heating joint of the barrel and head is well insulated, and whether the thermocouple and pressure sensor are installed reliably;

  • Check whether the vacuum exhaust system can operate normally;

  • Check whether each auxiliary equipment system and extruder elements can operate normally;

  • Check whether the emergency stop button is reliable;

  • Fill the cooling water tank with water and check whether the cooling water spray system can operate normally;

  • Organize the hopper, insert the baffle plate, and fill the material hopper of the metering feeder with material.

Currently, there are many types of double screw extruders, and the working principles of different types of double screw extruders are different, resulting in different material mixing and plasticizing effects. Therefore, they are applied differently in production. Seek advice from twin screw extruder manufacturers and select appropriate types based on the requirements of the processed products. 

  • Generally, meshing parallel co-rotating double screw extruders are mainly used for material dewatering, de-volatilization, granulation, and modification of materials, filling, reinforcement, and reactive extrusion. Meshing counter-rotating parallel double screw extruders are mainly used for directly extruding products such as polyolefins and PVC powders, as well as plastic modification.

  • Non-meshing parallel double screw extruders are mainly used for material dewatering, de-volatilization, reactive extrusion, mixing, and plastic recycling.

  • Cone-shaped double screw extruders are mostly counter-rotating meshing types, which are mainly suitable for the shaping and processing of PVC powders and thermosensitive materials, especially the extrusion molding of complex rigid PVC products, such as corrugated pipes and special-shaped profiles.