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different types of extruder screws brands

- Jul 16, 2022 -

different types of extruder screws brands

The screw is an essential component of a plastic extrusion machine. Through its turning motion inside a tight fitting barrel, the screw conveys the plastic, melts it and forces it through a die. These three steps are carried out in a continuous process capable of producing extrusions in a variety of lengths. The screw’s design is similar in principle to Archimedes’ screw of 250 BC, which was used to raise water to higher levels via axial rotation.

Modern engineering has expanded upon the screw of antiquity by redeveloping its geometry and applying it to plastic extrusion. Today’s extrusion screw can have varying pitch, helix angle, length to diameter ratio and length of processing stages. These variables influence the different pressure, shear and feed rates that are effective for a given plastic. Some extruders also use double screws to provide better additive mixing.

The basic extrusion screw has three distinct parts, each engineered to do a specific task. The feed section is in the rear of the screw, where plastic pellets are gravity fed from above and conveyed forward. The length to diameter ratio of the feed section is typically four or five to one, which is sufficient to build up the pressure needed to transport the plastic. However, the friction between the barrel wall and the plastic must be greater than that between the screw and the plastic in order for lateral movement to occur.

A barrel heater helps the plastic develop tack and stick to a wall. Sometimes, the screw is also chilled to free it of clinging pellets. Feed section length ratios can be increased to eight or ten to one for plastics with a low coefficient of friction. This extra length gives the plastic more time to heat up to a higher temperature, creating more friction at the barrel. From here, the plastic is channeled into the transition section of the screw.

In the transition section, the plastic is transformed into its liquid state through two concurrent methods. Barrel heaters provide some initial melting, while the shear caused by the motion of the plastic against the barrel completes the process. In this stage, the root of the screw increases while the flutes, or “flights,” subsequently decrease in size. This leaves less space for the plastic mass that has been compacted in the feed section. As pressure, shear and friction increases, the plastic begins to melt and flow. The transition section typically occupies five to ten diameters of the cycle.

In the metering or pumping section, the molten plastic is guided into a die. The root diameter of the screw and the size of the flights remain constant in this stage, and its length varies from four to eight diameters, depending on the application.

In the transition, or melting, section of a conventional extrusion screw, molten plastic has a tendency to surround the solid pellets, keeping them away from the barrel where melting takes place. This blockage can result in damaged equipment or unusable extrusions. The barrier screw was designed to address this problem, and it has become ubiquitous in the extrusion industry.

Barrier screws have additional flights serving as barriers in the melting section. These barrier flights are smaller in diameter than the inside of the barrel, creating a gap through which molten plastic may pass but solid pellets may not. This passage separates the solid and the liquid plastics, into their own channels. At the beginning of the melting phase, the solid channel is larger than the molten one, but as more plastic melts, the solid channel gradually empties. By the end of the section, all the material has been reduced to a liquid state.

Additives, such as binders or flock, are sometimes mixed with the plastic pellets before or during the extrusion process. Since standard and barrier screws are not engineered for mixing, a specialized screw must be used to combine the materials. Some systems employ twin side-by-side screws to mix the molten mass, while others rely on a single screw with reconfigured geometry at the metering stage.

In a twin side-by-side system, the two screws either counter- or co-rotate. In addition, various paddles, forward and reverse flights, or kneading blocks may be applied for specific mixing effects. These screw systems possess the same feeding, shearing and metering capabilities as single screw machines, but with a more homogeneous rate of mixing. Liquids, solids or combinations of the two can be combined with twin-screw mixers.

Single mixing screws use special heads at the end of the screw to mix the combined materials, or “batter,” while inside the barrel. There are several varieties of mixing head. The floating sleeve type uses a dimpled and flanged sleeve that floats between the screw and barrel. The viscosity and flow of the molten plastic keeps the sleeve turning slower than the screw because it rotates independently. The sleeve’s geometry and slow movement force the liquid to reverse its course downstream, effectively mixing the mass. Other mixing screws use fluted or pineapple shaped heads that can provide additional shear and cross flow.

The barrier screw is the most commonly used screw in plastic extrusion. Consequently, there is ongoing technological development to improve its efficiency, quality, and output. Likewise, both single- and double-format mixing screws are being redesigned to create a more uniform degree of melt. Several companies specialize in screw design and manufacturing, and their work will continue to influence the field of plastic extrusion.

different types of extruder screws brands

Family owned and operated in the USA, Santa Fe Machine Works is a world leader for injection and extrusion screw manufacturing. Since 1923, we’ve been committed to servicing the manufacturing industry with the same attention to detail our great grandfather gave his first customer. We work...

Blown film machinery, high performance mono and coex dies upto 22 layers for blown film and tubing, feed screws, K05 melt fracture reduction coatingsExtrusion lines of all types from 5 gram/hr to 50 pounds per hour including coextrusion. The 3D compounding screw mixes to the nano scale. Batch mixers from a single pellet to 200 grams. Extrusion services using 7 extruder and all downstream systems.

We improve service life and performance of feedscrews, mixing rotors and tip assemblies through application focused engineered thermal sprayed surfaces. We engineer surface coatings to withstand higher levels of abrasion, adhesion and corrosion to maximize production and enhance your bottom...Screws and Barrels: GTS (German TwinscrewS) has over 25 years experience in designing and manufacturing different type of Screws for a vast variety of products such as pipe, profile, sheet and pellets. We deliver large single screws and almost any size of twin screws up to diameter of 500 mm. We guarantee to...

Reiloy USA manufactures bimetallic barrels from centrifugally cast barrel blanks using specialized alloy powders for high wear applications. We are also an injection and extrusion screw provider for the plastics industry with full engineering and technical resources. Reiloy, a division of...REE, Inc. is a supplier of high quality extrusion technology and machinery. REE specializes in custom extruder screws and supplies patented CRD, VIP, and HHT screws for extrusion and molding. CRD mixers are based on elongational flow and provide superior dispersive mixing. VIP mixers employ...

different types of extruder screws brands

Coperion is a German company, As a pioneer in the development of the closely intermeshing, co-rotating twin-screw extruder, Coperion possesses unique know-how and an extraordinary wealth of experience in this field.

Twin-screw ex­trud­ers for the plas­tics and phar­ma­ceu­ti­cal in­dus­tries as well as tools and ma­chine tools for the au­to­mo­tive in­dus­try and me­chan­i­cal en­gi­neer­ing, Leistritz offer a wide range of so­lu­tions.

The heart of the extrusion line – the extruder – is made by Leistritz itself. The Germany site thus plays an important role, since German engineering is the basis for Leistritz lines.

JSW is a renowned Japanese company, mainly manufacturing machines including twin-screw extruders, large extrusion granulators, all-electric injection molding machines and film production lines.

The company offers various models – from the world’s smallest 0.4 mm screw diameter to the largest 10mm screw diameters as well as twin-screw machines for mixing and kneading.

Shibaura Machine is a Japanese company, Shibaura Machine was among the first companies in the world to establish mechatronics-oriented production systems. It started single-screw extruder manufacturing in the 1950s. Shibaura extruders are mainly used for plastic production like sheets, films and PVC pipes.

Cowin Extrusion is a Chinese company, located in Nanjing, China which is considered China’s extruders manufacturing base. Cowin Extrusion has been committed to the independent design and development of new technology and new equipment related to polymer material processing equipment, equipment processing and manufacturing, and complete project service business, and long-term focus on promoting the continuous development of high-end technology products and complete project technology.

Cowin Extrusion has a rich talent pool and technical experience in the field of polymer equipment manufacturing, its technical development team has more than 20 years of experience in the development of polymer blending modification complete sets of equipment while maintaining in-depth cooperation with domestic universities and research institutes, foreign advanced extruder companies.

CPM Extrusion Group is an American company, Our core competency is the development of complete compounding systems, twin-screw extruders, our RingExtruder (twelve screw extruder), spare parts for co-rotating extruders, self-cleaning intermeshing twin-screw extruders and service.

Steer manufacture co-rotating twin-screw extruders