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There are advantages, but it is not a panacea, the production of twin screw extruders is insufficient and the corresponding optimization scheme

Advantages of twin screw extruder

  1. Intuitively understand the wear of wearing parts. Due to the easy opening, the degree of wear of threaded elements and barrel bushings can be found at any time, so that effective maintenance or replacement can be carried out. It will not be discovered when there is a problem with the extruded product, resulting in unnecessary waste.
  2. Reduce production costs. When manufacturing masterbatches, it is often necessary to change colors, open the open processing area within minutes if necessary to change the product, and analyze the mixing process by observing the melt profile along the entire screw. At present, when changing the color, ordinary twin screw extruders need to use a large amount of cleaning materials for cleaning, which is time-consuming, electricity-consuming, and wastes raw materials. The split twin screw extruder can solve this problem, when changing the color, it only takes a few minutes to quickly open the barrel for manual cleaning, so that no or less cleaning material can be used, saving costs.
  3. Improve labor efficiency. When equipment maintenance, ordinary twin screw extruders often have to remove the heating and cooling systems first, and then extract the screw as a whole. The split twin screw does not need to, just loosen a few bolts, turn the worm gear box handle device to lift the upper part of the barrel to open the entire barrel, and then carry out repairs. This not only shortens the maintenance time, but also reduces the labor intensity.
  4. High torque, high speed. At present, the development trend of twin screw extruders in the world is to develop in the direction of high torque, high speed and low energy consumption, and the effect brought by high speed is high productivity. Split twin screw extruders fall into this category, with speeds of up to 500 rpm. Therefore, it has a unique advantage in processing high-viscosity, heat-sensitive materials.
  5. Wide range of applications, can be applied to the processing of a variety of materials; High output, high quality, and high efficiency can be achieved.
twin screw extruders

Deficiencies in the production of twin screw extruder

Parallel co-directional twin screw extruders are commonly used in plastic modification, plastic dyeing and plastic reinforcement. At present, domestic twin screw extruders, in the production process, have encountered a variety of problems, such as the following:

1. During production, the performance of particles is unstable;

2. Need to constantly adjust the formula;

3. Particle defects are getting worse;

4. Frequent replacement of screw fittings;

5. The cost of the formula cannot be reduced, but increased, and so on.

In fact, most of the above problems are caused by the shortcomings in the design of twin screw extruders

Twin screw extruder require optimized links

Equipment serves production, so solving problems in production is also a key consideration in equipment design. Now combined with practical problems, we will discuss the direction that twin screw extruders need to be optimized:

1. The physical properties of the product are reduced

When the plastic melt is extruded in the screw, due to the excessive relative gap between the screw and the barrel of the traditional extruder, excessive countercurrent phenomenon is produced, resulting in repeated shearing of the components in the formula, and excessive shear quickly increases the internal shear heat of the melt, which destroys the formula components to varying degrees, such as the early cracking and volatilization of small materials.

2. Particle defects (particles have pores, flow marks, scars, low yield, high power consumption)

Due to the large extrusion gap, the melt flows countercurrently, which will reduce the screw extrusion conveying capacity per unit time.

low head pressure; Cause particles to be not compact;

Low yield; Countercurrent causes repeated shearing, which invisibly consumes too much electrical energy and increases the cost of granulation.

3. The surface of the particles is not bright, the screw is not easy to clean when the material is replaced, and the cylinder is rusted and blocked

The barrel is the core component of the extruder, and the American arc plastic machine greatly improves the accuracy of the flow channel in the extrusion system, and the cylinder and screw are made of special alloy imported plastic machine. The finish can reach the mirror surface, which reduces the frictional resistance during melt propulsion, and also facilitates color change and cleaning, which is a necessary condition for the production of colored masterbatches and high-demand plastic masterbatches.

In terms of barrel cooling, Meiarc Plastic Machine adopts a dual-channel oil cooling system, which not only avoids the quenching of the cylinder, but also reduces the carbon deposits and rust plugging of the cylinder cooling hole.

4. The powder is not well dispersed

The arc of the thread sleeve tends to the theoretical design value; The kneading space is minimized and the mixing function of the thread sleeve is improved; Application analysis, such as: PP and PET two white masterbatches, requires not only good dispersion, but also high viscosity, if too much shearing, dispersion will of course be good, but the viscosity will decrease, directly affecting the spinning coloring effect.

5. Physical and chemical properties do not meet the requirements

Too many shear blocks, increase the shear heat of small materials, reduce physical properties, and chemical properties cannot meet the requirements. BECAUSE THE TWIN SCREW IS A COMBINATION OF BUILDING BLOCK THREADED SLEEVES, THE SCREW THAT MAKES MASTERBATCHES IS GENERALLY MADE WITH A RELATIVELY LONG DIAMETER (44:1 TO 48:1; 2090-2280MM).

twin screw extruders 2
twin screw extruders 3

The mandrel of the positioning thread sleeve is generally positioned on the side of the involute tooth, so the linear positioning accuracy of the mandrel is particularly important, which determines whether the phase of the first and last thread sleeve in the screw combination can coincide in a straight line, which is related to the Archimedes spiral kneading effect of the thread sleeve on the two screws; If the accuracy is not high, it will lose the thread sleeve kneading effect, and can only increase the number of kneading blocks to meet the shear effect, and the number of shear blocks is too much, which not only increases the resistance but also brings too much shear heat, which is easy to cause the decomposition of raw materials and the loss of formula components, and the loss of physical properties.

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