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Technology study of twin screw extruder

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Technology study of twin screw extruder

release date:2015-08-01 00:00 Source:http://www.sdob.cn Click:

Classification of extruder

Product code specification parameter

Note: for example SHJM-Z40 x 25 x 800, screw diameter is 40mm and the ratio of length to diameter of 25, traction roller length 800mm twin screw mixing plastic extrusion modified plastic film machine.

1, "SH" type code, refers to the double screw mixed (also have to write: SHSJ, SJ refers to plastic extruder)

2, "J" group code, refers to the extruder.

3, "M" refers to a variety of code, refers to blow film machine

4, "Z" refers to auxiliary code, referring to the main unit, the other is the "F" refers to the auxiliary machine.

5, "40 x 25 x 800" refers to the specifications, the screw diameter is 40mm, the ratio of length to diameter is 25, traction roller length is 800mm.

6, the last one for the manufacturer identification number, generally does not appear, is omitted

Two, the function parameter of twin screw extruder

1, "D" as the diameter, an important parameter to measure the size of the output.

2, "L/D", refers to the length and diameter ratio, directly affect the degree of the plastic, is a measure of the use of signs, general plastic modification, with 30-40 or so, commonly used 36:1 or 30:1.

3, "H", the depth of the slot, the size of the material space.

4, "e" the thickness of the screw, the process is reflected in the size of the shear.

5. The "6" screw and the gap between the machine and the machine, the quality of the extruder is an important parameter, which is usually in 0.3-2mm, and the 5mm is the police.

6, "N" the main engine speed, refers to its highest value, refers to a processing adjustment range, which greatly affects the production and the division of high and low speed. (domestic general 500-600r/min) such as: max:600r/min, 350r/min, 230-240r/min, medium speed: high speed 450-600r/min.

7, "P", motor power and heating power.

Three, screw arrangement and process setting

Section and function of screw

(1) the screw is generally divided into 5 segments: the conveying section, the melting section, the mixing section, the exhaust section and the average section.

1, conveying section, conveying material, prevent overflow.

2, the melting section, this section through the heat transfer and the friction shear, causes the material to melt and the homogenization fully.

3, the mixing section, so that the material component size further refinement and uniform, the formation of the ideal structure, with distribution and dispersion of mixed function.

4, exhaust section, discharge water vapor, low molecular weight material and other impurities.

5, all of the (measurement) section, conveying and pressure, the establishment of a certain pressure, so that the material has a certain density, at the same time, further mixing, and ultimately achieve the purpose of smooth extrusion granulation.

(2) distribution (allocation) and dispersion mixing stage

1, the distribution of mixed, so that the melt segmentation and reorganization, so that the distribution of the space distribution of each component is uniform, mainly through the separation of tension (compression and expansion), distortion, fluid activity and other stress functions under the replacement flow and realize.

2, dispersion, so that the composition of the particles into particles or make incompatible with the size of the dispersed phase of the two groups up to the range, the main shear stress and the stress of the.

Transmission element, screw type

- Representation Method: if the "56/56" conveyor block, the first "56" instruction process is 56MM, and the "56" refers to the length of 56MM.

- large lead, with a pitch of 1.5D~2D

- small pilot, the pitch is about 0.4D.

- the use of the law: with the increase in the lead, the increase of the screw extrusion, the material residence time and the mixing effect decreased.

- A, selection guide thread of the occasion, to transport primarily occasions, to improve the yield; thermo sensitive polymer, shorten the residence time, reduce the degradation; exhaust, selection (also choose shallow groove), surface area is increased, conducive to the exhaust, volatile.

- B, choose guided thread occasions, dominated by mixed occasions, with different work gradually narrowing the combination for transport and pressure boost.

- C, select the use of small lead screw occasions, for the general assembly is gradually reduced, used for conveying and metering section of the metering section, to improve the melt; improve the degree of mixture and extrusion stability.

The mixed refine element, there are two major categories, "K" series and "M" series (dentate)

- "K" series

- Representation: such as K45/5/56, belongs to the block shear, with "K" refers to the cutting of sheet block, "45" refers to the angle pieces spell, 5 refers to a total of 5, "56" refers to the length of 56mm, screw edge width for 56/5=11.2mm). The parameters:

- A, direction, there is a positive and reverse - reverse, the transport of the material has an obstacle to the role, play an extension of time, improve the filling pressure, greatly improve the effect of mixing.

- B, angle, generally have "30 degrees, 45 degrees, 60 degrees, 90 degrees", the role and effect:

- A, positive, larger cross angle will reduce transmission capacity, prolonging residence time, improve mixing effect, but the leakage flow. For the distribution of mixed and dispersive mixing, the distribution of the mixture is more effective and more efficient, and the dispersion is mixed at the angle of 45. When the best, followed by 30. , the worst is 60..

B, when the reverse angle increases, will reduce the effective limit, polymer, but the leakage flow

- C, 7mm, 11mm, 11.2mm, 14mm, 19mm, etc., which is one of the most important parameters in the measurement of the shear and the mixed size, the larger the width, the smaller the width and the smaller the width of the shear. For the distribution and dispersion, the distribution is mixed, with the increase of the width and the effectiveness of the dispersion, the dispersion increases with the increase of the width.


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