Threaded component combinations for different twin screw extruders
It is concluded that the full length of the screw of the twin-screw extruder is composed of several sections, and the so-called several sections can be distinguished by the feeding port and the exhaust port. If there is only one feed port and no second feed port or exhaust port, it can be regarded as a section. If there are two feeding ports or one exhaust port and one feeding port, it is regarded as the two segments and so on. It is necessary to use several paragraphs according to the requirements of the mixing process. Below is a small series to explain the requirements for the use of twin-screw extruders.
In a resin that participates in a solid filler and performs filling modification without requiring exhaust gas, a feed port is generally required. In this case, the combination of the screw and the barrel can be regarded as a combination. However, there are also exceptions. For example, if the packing is severely worn on the barrel, it is also conceivable to use two feeding ports. The top feeding port participates in the resin, and the second feeding port participates in the packing, that is, when the resin is melted, the filler is added, so that the melt can be The solid filler is wet-coated so that it does not directly touch the screw and the barrel, and the wear of the latter is reduced. If the amount of fillers involved is large, it is difficult to participate completely from a feeding port. It is also conceivable to use a second feeding port or even a side feeding port.
Two resins with different viscosities are blended to produce a plastic alloy. The requirements know the two group allocation ratios. If the low-viscosity material accounts for a small percentage, one feeding port can be used, that is, one section is selected; if the percentage of the two components is nearly flat, two feeding ports can be used to participate in the high-viscosity material at the top feeding port, and melt near it. A second feed port is provided to participate in the low viscosity material at a higher rate. If the low-viscosity material has a high share, or even three feed ports are available. This is considered. If a higher proportion of low-viscosity materials are joined with the high-viscosity materials from the top feed port, the former is like a lubricant, which will prevent the shearing component from inputting energy into the high-viscosity material so that it cannot be melted. The above approach is chosen for the detailed use of the equivalent viscosity criteria that are often followed for the manufacture of blends.
If the meltable resin and the non-melting rubber are blended, the selection of several feed ports (or a few sections of the twin-screw extruder) depends on the details. The rubber content is small and two or more feed ports are available. If the rubber content is large, 1 or 2 feeding ports can be used. If the rubber content is small, the rubber is difficult to disperse because the viscosity of the molten resin drops rapidly. In order to disperse the rubber, all rubber and part of the resin should be taken at the top of the feeding port, and the rest of the resin is taken in the downstream feeding port.
After the number of segments is determined, the selection and combination of various screw elements of each segment can be performed. Because the effects of the segments vary throughout the extrusion process, the combination of segments should also vary. Now take a three-stage combination of two feed ports and one exhaust port as an example to analyze how they are combined.
The first paragraph: The primary effect of this paragraph is to melt the resin. The beginning of the twin-screw extruder corresponds to the top feeding port. The threaded components here have a large pitch, a deep groove, and a large groove volume (greater than the future threaded components), to accommodate the low-volume participation of the self-metering feeder. Density material. The next section of the screw should gradually compact the loose material. Therefore, the threaded element with the gradually smaller volume of the groove should be selected (after variable pitch, variable groove depth, variable screw width, etc.), if it is needed in this section To mix the material, a toothed threaded element can be added, after which a positively threaded element of equal depth is added to establish the pressure. A set of kneading discs can be attached after the positive threaded element, in order to promote the melt plasticization of the material (the material should be fundamentally melted and plasticized here), if the reverse threaded element is connected, the intention is to melt, establish pressure and form a seal, It is beneficial to feed in the second feeding port at the back.
The second paragraph: its primary function is to participate in the second component (such as fiberglass and second resin, etc.) and mix it with the materials from the top of the feed. The beginning of the threaded component is aligned with the second feeding port, and should have a larger volume of the groove, so that the material in the groove is in a semi-filled, non-pressure state, so as to facilitate the participation of materials. After that, the transporting component can be connected, and then the toothed component or the reversely threaded component or the kneading disk component (the spiral direction formed by the staggered angle can be forward or reverse) to facilitate the mixing of the materials by the two feeding ports. And set a high pressure before the exhaust port after this to form a seal.
The third paragraph: its primary function is to exhaust, further mixing, and finally the fixed material is extruded from the die by constant pressure, quantitative and constant temperature. The beginning of this section is the threaded element facing the exhaust port, and its groove volume should be large to facilitate the appearance of the renewal. The downflow of the exhaust port can be connected to the positive thread conveying element, but the pitch should be gradually reduced (even if the volume of the groove becomes smaller), so that the material gradually fills the groove and establishes the pressure. If it is further desired to further enhance the mixing effect, a pair of toothed elements or kneading disc elements may be combined. In the final section of the twin-screw extruder, the threaded elements should be transported equidistantly in the forward direction for final quantitative, constant pressure, and constant temperature transport of the material to the die.
The above is the general twin screw extruder thread component combination criteria. The combination of threaded components of a twin-screw extruder is a very complex, multi-element, multi-conditional experience-based skill process that combines various materials, processes, temperatures, and environments to explore. However, the scientific and reasonable combination of the screw improves the mixing effect and product quality, improves the production power, reduces the energy consumption, and extends the service life of the equipment. Therefore, the importance of the screw component combination in the production of the blending modification process should be highly valued by the equipment manufacturers and users, and the research and innovation will continue to be explored, which will play an important role in energy saving, quality improvement and production value expansion. The company supplies kneading blocks , thread blocks, shear blocks , screw components, extruder barrels , twin-screw mandrels, etc. Welcome to inquire!