What is a twin screw extruder? It is a newly developed machinery that has been widely used in the extrusion industry due to its improved performance. So friends who are familiar with it may already know its operating process. Today, the editor will introduce to you the operating methods to improve the blending performance of the twin screw extruder, as well as how to carry out maintenance work for the subsequent use of the twin screw extruder. If you are interested, then follow the editor to read the article together!

1、 Improving the Blending Performance of Twin Screw Extruders

1. Add insulation gaskets between the flanges of the feeding section and the second section

The feeding section of the machine barrel is mostly water-cooled and locked together with the second section of the barrel (heated) by a flange, allowing heat to be continuously transmitted from the high-temperature barrel to the cold barrel. Causing the second section of the cylinder to not maintain sufficient temperature. Usually, the operator sets a temperature of 180 ℃ on the second cylinder, but due to the heat loss in the feeding section, the actual stability usually does not exceed 135 ℃.

The solution is to add 1-2 1mm thick insulation gaskets between the feeding section and the second cylinder flange, and replace the insulation gaskets every few years because they tend to age, degrade, and shrink.

2. Replace the extruder cooling system with a high-pressure cooling system

As we all know, turbulent flow in a water pump can cause more wall heat exchange than laminar flow. Turbulence in high-pressure transmission has a high degree of transverse momentum exchange, which breaks the boundary layer. As a result, the intense fluid movement caused much greater heat exchange between the pipe wall and the fluid. The cooling circulation system of the extruder generally provides a pressure of 20-60psi.

To achieve turbulence, a pressure of 120PSI should be reached. Almost all cooling system components (hoses and valves) of the extruder need to be upgraded to 150PSI in order to meet the safety factor of 120PSI. After the transformation is completed, the cooling system can timely discharge a large amount of heat during processing.

3. Using appropriate modifications to increase feed rate

(1) The volumetric feeding capacity of side feeding and the volumetric feeding capacity of the main screw of the extruder. The volumetric feeding capacity depends on the free volume of the side feeder and main screw, as well as the rotational speed of these two screws.

The main screw should have a long pitch threaded element, extending a length of 2D-4D downstream of the side feeding port. This will allow the melt to quickly pass through the side feeding port, allowing the filler to be fed into the main screw to a large extent. If the design of the host screw causes the accumulation of any side feeding material, it will severely limit the feeding amount of the filler.

(2) The exhaust capacity that allows gas to be discharged from the extruder. The purpose of exhaust is to make it easy for air to escape, while also protecting the filler from excessive leakage from the exhaust port. A good configuration is to open an upward exhaust port upstream of the side feeding port. Sometimes, a small half slit is opened in the upper part of the side feeder for exhaust.

2、 Equipment maintenance of twin screw extruder

1. Flush the cooling water channel with acid

The water-cooled extruder barrel is actually a heat exchanger, like all heat exchangers, the water channel is prone to scaling and deterioration. Many operators have noticed that the cooling performance of a new extruder is much better than that of an extruder that has been in use for three to four years. The old machine has a layer of scale attached to the surface of the water channel, which affects heat transfer efficiency. Cleaning the machine barrel with a certain concentration of acid solution can remove scale and maintain good heat transfer performance of the barrel.

2. Use synthetic gear oil

The gearbox is the heart of a twin screw extruder. Therefore, we should prevent the gearbox from having problems. The use of synthetic gear oil can better protect the gear.

3. Regularly clean the machine

The purpose of machine cleaning is to remove residual materials from the extruder and die, which avoids time-consuming disassembly and cleaning. Cleaning materials are often divided into two categories: chemical cleaning agents and mechanical friction cleaning agents. Many cleaning agents have both chemical and friction functions. Chemical cleaning agents will react with plastic residue to detach it from the mechanical surface.

The principle of mechanical friction cleaning is to rub and wash away residual materials from the metal surface, using friction and shear methods. Processors can only find suitable cleaning materials and methods through multiple experiments. No cleaning material has a cleaning effect on all materials. Processors need to clean materials cheaply and effectively.

The above is some basic knowledge about twin screw extruders summarized by the editor. You can delve into it and learn more about this field, which can help you better understand this industry.