How To Use The Kneading Block of The Extruder

The kneading block of the extruder is also called the shear block or the screw element. It plays an important role in the extrusion compression molding system. Its structure is usually relatively simple. It is usually composed of two or more blocks combined with each other and installed on the screw. It has the functions of increasing the staggered angle, reducing the transmission capacity, prolonging the residence time of the material in the extruder, and improving the mixing effect.

The angles of kneading blocks are generally 30, 45, 60, and 90 degrees. In mixing, the angle of 45 degrees is the most ideal, followed by 30 degrees, and the effect of 60 degrees is relatively poor. Common kneading blocks are usually double-headed, which are composed of single double-headed kneading blocks stacked together at different angles.

The main parameters that affect the kneading blocks are the staggered angle, the number of kneading blocks, and the thickness of a single kneading block. The thicker the kneading block, the greater the shear and the less the mixing. The smaller the width, the less shear and the greater the mixing.

The kneading block has the function of distributing and mixing materials. Distributing and mixing means dividing and reorganizing the solution. The solution is divided through separation, stretching (compression and expansion are produced alternately), twisting, fluid activity and other methods, so that the solution is distributed more evenly in space.

Dispersive mixing refers to the dispersion and mixing of particles or materials that have been divided into small particles but are incompatible to achieve the corresponding mixing requirements. Dispersive mixing is mainly achieved by shear pressure and tensile stress.

At present, in addition to the double-head kneading block, there are also merchants producing three-head kneading block combinations and combinations of double-head and three-head kneading blocks acting on twin-screw extruders. The double-head and three-head kneading block combinations are divided into two groups, each corresponding to a screw, and are installed at the corresponding extruder screw conveying position when used.

The double-head kneading blocks can be smoothly connected with the double-head threaded sleeves at both ends of the double-head and three-head kneading block combination. The three-head kneading blocks in the combination are arranged with a 90-degree phase difference. The arrangement angles of the adjacent three-head kneading blocks in each group of double-head and three-head kneading blocks are 90 degrees, 60 degrees, 45 degrees and 30 degrees.

Such a kneading block combination has the function of fully crushing and mixing the powdery or loose raw materials just entering the barrel, and can also improve the striking, extrusion, shearing and grinding performance.

Summary: Kneading blocks are components installed on the extruder screw. They are used in combination of two or more to mix and disperse materials and improve the mixing effect of the extruder. If you want to achieve a good mixing effect, it is important to choose the right kneading block.

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