Introduction to the role and function of twin-screw thread elements


Screw outer surface cut with a spiral groove of the cylinder or cut with a conical spiral groove of the cone. The screws have different heads, such as large flat screws, hexagon socket screws, etc. Today Xiaobian mainly talk with you, the role and function of the double screw thread element.

Segmentation of twin-screw thread elements and their functions

1, generally divided into five sections: conveying, melting, mixing, exhaust, homogenization.

(1) Conveying: Conveying materials to prevent overflow of materials.

(2) Melting: The material is completely melted and homogenized by heat transfer and friction shear.

(3) Mixing, further refining and homogenizing the size of the material components, forming an ideal structure, with the mixing function of distribution and dispersion.

(4) exhaust: exhaust water vapor and low molecular weight substances and other impurities.

(5) Homogenization: Conveying and pressurizing, establishing a certain pressure to make the material at the die have a certain density, and further mixing to achieve the purpose of smooth extrusion and granulation.

2, distribution (distribution) and dispersion mixing segment.

(1) Distribution and mixing, that is, the melt is divided and recombined, so that all components are evenly distributed in space, which is mainly in the separation, stretching (compression and expansion alternately), distortion, fluid activity reorientation and other stresses Realized by displacement flow.

(2) Dispersive mixing, that is, the components are broken into particles or the size of the two-component incompatible dispersed phase reaches the required range, which is mainly achieved by shear pressure and tensile stress.

3. Twin screw thread element

(1) Representation: For example, for the "56/56" transport block, the dominant route of the former "56" is 56MM, and the length of the latter "56" is 56mm.

(2) Large citation, referring to pitch 1.5D ~ 2D.

(3) small lead, refers to the pitch of about 0.4D.

(4) Its use rule: With the increase of lead, the extrusion amount of the twin-screw threaded element increases, the material residence time decreases, and the mixing effect decreases.

(5) the use of large lead thread occasions to transport-based occasions, is conducive to increasing production; heat-sensitive polymer, shorten the residence time, reduce degradation; the use of exhaust (or shallow groove) to increase the surface area, is conducive to exhaust and volatile.

(6) the selection of medium lead thread occasions, mainly mixed occasions, there are different working sections of the combination, gradually reduce the delivery pressure.

(7) When selecting small lead wires, the general combination is gradually reduced, which is used to pressurize the conveying section and the homogenizing metering section to improve melting; improve the mixing degree and extrusion stability.

(8) Mixed elements, there are two types, "K" series and "M" series (with teeth)

"K" series: annotation: such as K45/5/56, belongs to the cutting block, where "K" refers to the sheet cutting block, "45" refers to the angle of splicing pieces, "5" refers to a total of 5 pieces, "56" refers to the length of 56MM and the width of 56/5=11.2mm spiral rib).

Direction, divided into forward and reverse. The opposite direction will hinder the transportation of materials, extend the time, increase the filling pressure, and greatly improve the mixing effect.

Keywords: Introduction to the role and function of twin-screw thread elements

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