Plastic extruders and extrusion lines enable testing of materials before production in the conditions of a research laboratory.
The market for plastics and other extrudable materials always wants more new technologies The market for plastics today demands more and more complex, faster, smarter and better quality solutions in extrusion plants of various materials This involves optimizing extruders, materials, processes and extrusion technologies construction of extruders and their equipment is of key importance for the plastic extrusion technology
Evolution of polymeric materials and their composites becomes a major challenge in plastics extrusion process researchFewer and fewer extrusion lines process virgin materials; this is mainly due to high cost and environmental reasons.
For this reason, manufacturers of lab extruders and associated equipment are adapting to new and diverse polymer materialsCustomers are looking for ease of use and flexibility of lab extruders Government safety and environmental regulations are a constant challengeCustomers are looking for lab extruders that can effectively and reliably simulate production equipmentLaboratories use extruders to develop new compounds plastics or to ensure the quality of your own extrusion systems.
Zamak Mercator is a manufacturer of laboratory extruders for plastics, single and twin screw with screw diameters of 2 x 12/2 x16/2 x 20/2 x 24 mm, co-rotating and counter-rotating with a range of L/D up to 48, with modular and non-modular construction
Our laboratory plastic extruders provide scientists with a high ability to reproduce and design industrial extrusion processes in the conditions of a research laboratory. Due to the high complexity of the extrusion process, a research extruder should have all the capabilities of industrial extruders and even surpass them repeatable and enable the processing of virtually all plastics and many other materialsExtruder preparation time for subsequent tests is shortIn the practice of a research laboratory, meeting this assumption means that in a short time the laboratory extruder must reach and stabilize the working parameters set by the scientistThis feature allows you to respect the scientist's timeChanges to the set parameters must be reliable, repeatable and fast All measurement data must be reliable.
You can achieve reliable scale-up, reduced research or time-to-market of your plastic productOur laboratory twin-screw extruders offer flexible equipment configurations from small batches to pilot scale or low-volume production and are ideal for research and development in the polymers, pharmaceutical, biology and nanotechnology Pharmaceutical manufacturers need precise and reliable laboratory twin-screw extruders that can be relied on to create new drug blends dispersed in a polymer matrix. Our extruders meet a wide range of process requirements, even for the most difficult formulations.
The challenge for a manufacturer of laboratory extruders remains to keep laboratory extruders simple and convenient. It can be said that if something is functional, easy to use and designed to be operated comfortably, the chance that people will use it increases significantly” Our extruders are designed with space saving in mind , money and time.To maximize productivity by allowing quick changes to test materials.
A characteristic feature of laboratory rolling mills for plastics, rubber and other materials should be a wide range of operating parameters, as in the case of laboratory extruders for plastics. Meeting these conditions enables the implementation of a wide range of research on processing processes for various plastics and other materials.
The most important feature of our laboratory rolling mills is the ability to simulate industrial rolling processes in laboratory conditions. Safety of rolling mill operation, ergonomics and short preparation time for the next test are equally important.
The two-roll rolling mill is equipped with doubling mechanisms for independent regulation of the rotational speed of each roll Roller drives should have high power independently for each roll of the rolling mill to enable the testing of a variety of plastics, rubber and other materials Independent roller drives enable full range of friction adjustment with high accuracy Unique electrical adjustment mechanism the gap between the rolls automatically controls the mutual parallelism of the rolling mill rolls during operation Possibility of quick adjustment of the gap between the rolls, its continuous control and the possibility of changing it during the rolling process determine the efficiency of the process and material savings The driving mechanisms and the mechanisms regulating the distance between the rolls are adapted to transfer high forces during rolling of plastics or rubber The rolling mill can be equipped with automatic programmable liquid and granule dispensers All settings can be saved in memory devicesAll measured parameters can be saved on a memory device at any time intervals from 1 s The temperature of the rolling mill rolls is measured by 6 precise temperature transducers, arranged in such a way as to enable control along and around the circumference of the roll The rolling mill is a universal, precise, automated research tool It enables testing of rubber mixtures and polymers.
The rolling mill allows for precise, independent regulation of the speed of the rolls and the distance between the rolls [working gap] The distance between the rolls is compensated depending on the temperature of the rolls of the rolling mill This means that it does not change [decrease] as a result of increasing the diameter of the rolls with increasing temperature The digital controller of the rolling mill takes care of that the gap does not change regardless of the temperature of the rolled plastic or rubber The gap size compensation mechanism is of key importance when rolling thin foils with a thickness of less than 0.5 mm The rolling mill makes precise temperature measurements independently for three zones of each roller The forces acting between the rollers and the parameters are precisely measured each drive motor.
The injection molding station for testing the mechanical properties of thermoplastics optimizes the development process, enabling testing of the properties of samples from 5 ml to 20 ml.The need to produce different samples with varying geometry combined with a limited amount of material can often cause great difficulties in product development.
Strict management of all parameters during sample creation enables optimal repeatability and precision of research. Unintentional potential user influence on sample quality has been limited by controlling and storing all operating parameters of the devices.
The injection molding machine can be equipped with molds for paddles, bars, discs and other samples for testing plasticsPrepared molds meet current standards, and can also be adapted to specific customer needsReady samples can be used for strength tests of thermoplastics, Charpy impact tests, determination of Shore hardness, as well as for determining mechanical properties and modulus of elasticity, e.g. when stretching or bending. Moreover, the obtained forms are perfect for research on thermal degradation of polymeric materials and for determining processing and secondary shrinkage of plastics.
Test specimens can be made from powders, granules, or by direct transfer from a conical or parallel twin-screw extruder. The geometry of the injected specimens is offered from fixed standards to custom molds that can be ordered individually.
The Zamak Mercator test system was designed based on RIM micro injection molding machines and the REM-2C Vertex II micro cone extruder as a piston injection system for test samples. The system allows to radically reduce the amount of material used due to its small volume compared to conventional injection molding devices the cylinder of the injection molding machine and the volume of the plasticizing system of the extruder.
Three basic extrusion research equipment has been briefly described above.
Our offer includes many models of single and twin screw extruders, rolling mills, micro injection molding machines, granulators and other equipment for research lines. The devices in our offer allow us to offer many, even unusual and personalized stations and lines for research on new polymers, composites and other materials.
Extruders and lines for rubber or silicone profiles are intended for the production of rubber and silicone profiles of any diameter and shape. process.
The product range includes a complete range of single-screw extruders for rubber and vulcanization systems based on modern and energy-saving technologies of hot air combined with IR (Infrared) radiation, which penetrates the material accelerating the vulcanization processVulcanization system consisting of a shock furnace and a segmental vulcanization furnace can be configured according to with the customer's expectations [length, width, speed, number and distribution of radiators] Our lines enable the production of rubber profiles for almost all industries, including, above all, for the automotive, household appliances, construction, transport and military sectors.
The rubber and silicone vulcanization line includes the following devices:
Zamak Mercator is a manufacturer of single-screw extruders for rubber and silicone with screw diameters from 32mm to 120mm in the L/D range of 8 to 22. The construction of the extruders is based on innovative design assumptions, modern components and is based on many years of experience gained in the rubber and silicone processing industry. durable, reliable and repeatableThe preparation time for subsequent tasks is short due to the refined design solutions and high thermal efficiency of the plasticizing system. Changes of the set parameters are reliable, repeatable and fast. All measurement data are reliable.
The first key factor determining the quality of production is the control and reliable measurement of temperature in each of the extruder zones. The extruder cylinder j must be designed in such a way that each zone has high energy efficiency. are arranged in such a way as to ensure reliable measurement and limit thermal interference.
The second important factor is the technical parameters of the rubber extruder and the possibility of adapting the device to work with various materials. High maximum torque, maximum revolutions, drive motor power and operating temperature range. of which the screw and cylinder are made will allow it.
In rubber extrusion, stabilization of the final shape always means heat vulcanization. Different methods can be used for this, depending on the product requirements and material properties.
The IR (Infrared) shock oven and IR tunnel ovens enable the vulcanization process to be carried out using heat supplied by infrared radiators.Radiators emit infrared radiation, this is electromagnetic radiation (EMR) with a wavelength longer than visible lightIR covers wavelengths from about 1 millimeter to about 700 nanometers Infrared radiation can be used as an energy source for heating One of the advantages of this energy is that the energy Infrared radiation directly heats illuminated objects by penetrating their surface. Heating with infrared radiators is becoming more and more popular in industrial production processes. In these applications, infrared radiators replace convection ovens and can be effectively used to vulcanize profiles of very different shapes.
The distribution of infrared radiators in the furnace chamber is selected individually for the customer's application. Radiator power regulation is carried out independently for each zone, thanks to which it is possible to adjust the intensity of the thermal energy stream to the shape of the vulcanized profile.
Infrared radiation ensures high efficiency of heat transfer without the use of an intermediate medium (air or other gas) to the vulcanized material. This solution minimizes the heat loss needed to heat the media used in other vulcanization methods.
The shock IR furnace by ZAMAK MERCATOR is equipped with high-power short-wave IR radiators. The furnace is designed to pre-fix the shape of the extruded profiles and create a skin. infrared radiation Therefore, it is a very effective process, especially in the process of pre-vulcanization The profile formed in the head is fed into the blast furnace chamber and, under the influence of infrared radiation, its surface is initially cross-linked As a result, we obtain a thin, pre-vulcanized coating on the profile before it goes to the actual curing furnace This improves the quality of the product by giving the profile surface smoothness and a delicate gloss, and enables better control of the external dimensions of the profile.
IR tunnel ovens ensure short heating time and vulcanization throughout the entire volume of the extruded profile. The use of infrared heaters enables faster vulcanization and better temperature distribution throughout the section, thus ensuring high dimensional stability of the product and higher quality.
Thanks to the optimized design of the reflector, we can reduce energy consumption. The furnace has separate heating zones, enabling the selection of individual parameters of the vulcanization process, depending on the shape of the vulcanized profile and the extrusion speed.
The regulation of the vulcanization process is carried out by means of an advanced control system for the power of the radiators.
The divided construction of the furnace allows the opening of individual segments, enabling easy changeover of the conveyor belt in the tunnel chamber and control of the process during its operation.
The great advantage of infrared furnaces is the short time necessary to obtain full readiness for operation. This significantly reduces the energy losses needed to heat the chamber.
Filament production for 3D printers is a highly valued technology Launched industrial innovation, ensuring the cost-effective production of a wide range of filaments necessary for 3D printers operating using FDM additive printing technologyFused filament manufacturing is one of the most widely used technologies that has found the maximum number of applications in all types of sectors manufacturing, including biomedical, aerospace, automotive, pharmaceutical, construction, electrical and electronic food and various others. Thanks to the highest level of printing flexibility and cost-effectiveness, it holds the largest share in the 3D printing industry.
Filament production lines that are intended for use in 3D printers are characterized by high linear speeds, precision and dimensional accuracy, energy efficiency and intuitive operation while maintaining great controllability of the entire process. melted plastic continuous filament, and then wound it on the spool of the winder It may seem easy, but a good 3D printer filament that actually prints well must be completely uniform and homogeneous in terms of composition The key parameters determining the quality of a 3D printer filament is its diameter and ovality A change in diameter or ovality by a few hundredths of a millimeter can result in poor 3D print quality Cheap filament lines and extruders generally produce low quality filaments as they are unable to maintain the quality necessary for smooth printing The incredibly fast-growing 3D printing industry is challenging 3D printer filament production line manufacturers and plastics manufacturers 3D printing process introduces a new level of variabilityToday's 3D printing customers don't like to wait long for new filaments and prefer to quickly delight in new ideas and inventionsThis is a problem for larger industrial producers with their long product development cycles and inability to produce customized products.
Since filaments for 3D printers working with the use of FDM technology are subject to very high requirements regarding uniformity, diameter and ovality, the lines used for their production must also meet high requirements.
When it comes to the benefits that large format 3D printing can bring to your business, several factors come into play. The key considerations include the ability to improve speed, cost and quality. 1, moulds, patterns, furniture, boats and end parts All of them are particularly well positioned for the growing use of large format 3D printing.
Prototyping was the first and remains the largest area of application for 3D printingIndustries such as automotive, aerospace, boatbuilding and anywhere where large thermofusible plastic parts are neededBeing able to do it relatively quickly in-house speeds up the design process and time to market Ensuring proper fit and functionality of the part is a critical parameter of the design process Hands-on use of 1:1 scale prototypes allows teams to ensure all the real-world parameters required by the design In such applications, 3D printing is the obvious solution, as it is faster and cheaper than standard alternatives The greatest advantage of industrial 3D printing is the freedom to design parts, which does not depend on any tool or form.
Building larger parts means pushing the boundaries of extruded plastic 3D printing technology Means replacing 3D printer filament with plastic pellets that will directly feed the 3D printer head As the part size increases, so do the challenges that must be overcome to achieve good results using printing technology FDM FDM technology is the process of creating physical objects by building successive layers of molten plastic Thermoplastic fiber obtained directly from pellets is placed by the 3D printer head where it is needed in each layer to complete the desired object Underlying is the method or process of Additive Manufacturing (AM) opposite for traditional manufacturing, which is based on subtractive technology 3D printing in FDM technology from plastic pellets is clean, easy to use and user-friendly Thanks to industrial-grade materials that are mechanically stable e and eco [PLA pellets] amazing results are possible These include many of the same tried and tested thermoplastics used in traditional manufacturing processes such as industrial extrusion or injection molding.
FDM [Fused Deposition Modeling] printing technology using fiber-powered 3D printers has limited 3D printing performance. Also, the price of the 3D printing filament itself is high compared to the price of plastics supplied in the form of pellets. An additional factor to be considered is the need for multiple processing [melting ] of plastics to produce [extrude] a filament for a 3D printer. Multiple melting of plastics deteriorates their physical and chemical properties. Therefore, the use of heads for 3D printers that extrude plastic directly from granulate is technically and economically justified.
3D printing with lightweight extruders powered by pellets provides a number of benefits Allows you to achieve very high productivity from 1kg / h to 120 kg / h depending on the 3D printing head used Reduces the cost of materials and offers access to new types of polymers that are not present in the filament format. The 3D printer head, built on the basis of a professional extruder, can be equipped with replaceable screws adapted to the extrusion of various types of materials.The use of dedicated screws allows printing with many materials available in the form of granules such as PLA, ABS, TPU, PETG, ASA, HIPS and others.
These benefits are offered by a new range of 3D printer heads designed for use in robotic 3D printersThanks to our technical solutions, customers achieve higher printing speeds and larger sizes of 3D printsDue to the professional construction of our 3D printing heads, they provide excellent polymer plasticization, transport and construction pressure and very good distributing mixing and homogenization of the extruded alloy. These are the key factors that have a decisive impact on the quality and mechanical properties of the printed prototype using the FDM [Fused Deposition Modeling] technology.
The combination of pellet-powered 3D printing heads in combination with multi-axis industrial robots from companies such as ABB, Kuka, Fanuc is usually used for large-scale printing, e.g. furniture, boats, and makes the production of these objects more economical due to lower material costs and faster 3D printing times
In addition, customers can create their own custom composites and material blends by combining different granules By easily adding various dyes, additives and reinforcing fibers to the mix, customers can create custom composite plastics Professionally creating your own blends and composites requires a professional granulation line equipped with a twin screw extruder along with the appropriate equipment necessary to run the process, Zamak Mercator offers professional lines for creating plastic composites. Therefore, printing with granulate-powered 3D printer heads not only ensures efficiency and financial benefits, but this technology also provides environmental benefits.
The flexibility and versatility of industrial robots makes them the ideal component for the implementation of automated additive manufacturing methods due to their repeatability and accuracy By combining automation tools, extruders and application-specific software, the needs of industrial additive manufacturing can increasingly be met. hoc and a faster, stronger and cheaper approach to manufacturing continues.
This is an exciting time for modern 3D printing as very small or very large components and parts can be produced in line with the on-demand economy, with benefits such as reduced cost of prototyping. with traditional subtractive methods Product integrity, consolidation of larger assemblies and multiple material combinations can be achieved, expanding the range of production possibilities.
High-protein extruded food productsExtrusion technology for textured meat analoguesConsumer demand for higher-quality food products with excellent texture and high nutritional value is growingExtrusion processing has proven to be a very practical and economical food processing tool It is used to produce a variety of food products that are used by consumers Due to its ease and extrusion offers many opportunities, it will continue to be a valuable processing technology for the food industry As extrusion research continues, more and more methods to use it effectively and further change will continue to drive the technology and expand the number of possible products that can be produced with food extrusion technology.
The most common types of extruders used in food processing are single-screw extruders and twin-screw extruders. A single-screw extruder consists of only one screw housed in a barrel, which is often of fluted or grooved design. Additionally, the screw in a single-screw extruder is usually designed with a decreasing pitch to produce compression. The amount of decreasing pitch is determined by as a compression stageTwin screw extruder has two screws that are intertwined or non-interlacedThe set up in a twin screw extruder can be co-rotating or counter-rotating Co-rotating is more commonly used because it can transfer more mechanical energy to the material than counter-rotating screws Twin-screw extruders are more commonly used in the food industry due to their wide range working conditions and the ability to produce food products
Twin screw extruders are characterized by high flexibility in handling various ingredients and higher production rates than single screw extruders Twin screw extruders can operate with a greater range of moisture content, which is the limitation of the single screw extruder Preconditioning systems can be used to extend the capabilities of the extruders which can prevent residue build-up, and relatively faster and more uniform heat transfer from the cylinder walls to the extruded food ingredients.
Food extruders intended for research on food extrusion should provide scientists with a high ability to reproduce and design industrial processes in the conditions of a research laboratory. Due to the high complexity of the food extrusion process, a laboratory extruder should have all the capabilities of industrial extruders and even exceed them. that in a short time the laboratory extruder for food must reach and stabilize the process parameters set by the scientist. Changes in the set parameters must be reliable, repeatable and fast. All measurement data must be reliable.
Our food twin screw extruders offer flexible configurations from small batches to pilot scale or low volume production, and are ideal for research and development in the food, pharmaceutical, biology and nanotechnology sectors. Manufacturers need reliable and accurate laboratory twin screw extruders for research and development to create new blends of extruded ingredients Our instruments meet a wide range of process requirements, even with the most challenging formulations.The best tool for researching food extrusion processes are laboratory extruders that can work as co-rotating and counter-rotating. These extruders are equipped with a Vertex II automatic changing the direction of rotation of the screws.
A laboratory extruder designed for food extrusion provides full control over the entire process. Thanks to accurate measurements, structural changes in the product can be recorded in real time and correlated with the obtained product properties.
In addition to changing the texture and restructuring of plant food proteins, the food extrusion system performs several other important functions: denatures proteins Proteins are effectively denatured during the moist, thermal extrusion process Protein denaturation lowers solubility, destroys biological activity of enzymes and toxic proteins Deactivates residual, growth inhibitors native to many plant proteins raw or partially processed Growth inhibitors have adverse physiological effects on humans or animals, as shown by growth or metabolism studies Controls raw or bitter flavors commonly associated with many plant-based sources of dietary protein Many of these undesirable flavors are volatile and are eliminated by extrusion and decompression of the protein into extruder head.
HME pharmaceutical extrusion has become a novel processing technology in the development of molecular dispersions of active pharmaceutical ingredients API (Active Pharmaceutical Ingredient) into various polymer and/or lipid matrices. This technique enables time-controlled, modified and targeted drug delivery. HME has received significant attention from both the pharmaceutical industry and academia for applications for pharmaceutical dosage forms such as tablets, capsules, films and implants for oral, transdermal and transmucosal drug delivery. These pharmaceutical extrusion capabilities make HME is an excellent alternative to other available techniques In addition to being a proven manufacturing process, HME meets the goal of the US Food and Drug Administration's Process Analytical Technology (PAT) scheme bones and drugs (FDA) to design, analyze and control the manufacturing process by measuring quality control during the active extrusion process. .
In recent years, extrusion technology has shifted the focus of pharmaceutical research due to its versatile applications. In the meantime, great effort has been devoted to the miniaturization of equipment in pharmaceutical extrusion technology, especially with regard to the development requirements of new chemical entities and formulations. This has led to a reliable small-scale extrusion process.
Hot extrusion (HME) technology has proven to be a robust manufacturing method for many drug delivery systems and has therefore proven useful in the pharmaceutical industry as well. Extrusion is the process of pumping, mixing, and shearing materials at elevated, controlled temperature and pressure into a product of uniform shape and density. and transforming powder or granular mixtures into a uniformly shaped product During this process, polymers are melted and formed into products of various shapes and sizes.
Extrusion is a technique with great potential for use in organic synthesisExtrusion provides a way to achieve mixing of reagents, it also allows fine tuning of the mixing range by modifying the configuration of the pharmaceutical extruder. The extruder itself can provide heating up to several hundred degrees and small amounts of solvent can be added to speeding up the reaction Extruders can be equipped with efficient cooling systems Therefore, it can be concluded that the extruder provides most, if not all, of the parameters that conventional solvent-based synthesis can provide In fact, with regard to the current move towards a more sustainable environment, the extruder is advantageous because the amount of solvent is reduced or eliminated Moreover, typically reaction times are significantly shortened and drug-release devices with a processing option that maximizes the blending of API and polymer while minimizing API (Active Pharmaceutical Ingredient) degradation, and even opens the door to products that cannot be prepared by other means.
The modular configuration of twin-screw extruders makes it possible to combine several unit operations in one machine.Feeding, mixing, extrusion and molding are performed simultaneously in the twin screw extruder due to the continuous process.
In recent years, twin screw extruders have been successfully applied to pharmaceutical applications through reduced size machines. The key factor is the size and in particular the volume of the plasticizing system of the pharmaceutical extruder.
Twin-screw extrusion has become an efficient and flexible technique due to advantages such as cost reduction, improved process efficiency and flexibility in research and production capacity it is also applicable in the development of new solid dosage forms for personalized medicine.
The high material throughput required by the continuous extrusion process is an advantage in production but is a limitation in the development of new formulations Particularly in the early development period, new chemical units are not available or are too expensive in large quantities Therefore, there is a need for low throughput extruders for product development pharmaceutical products obtained by pharmaceutical extrusion (HME).
In pharmaceutical production, small extruders are useful because they are more reliable when using small quantities, and batches can be easily accessed and easily adjusted by changing the process.
One of the dominant obstacles in the development of miniaturized extruders is the optimization of key parts of the equipment when downsizing The limitations are the available materials, specifically the availability of structural acid-resistant steels with the desired strength properties and approved for contact with pharmaceutical products Another limitation is the ability to design and build miniature extruders with high performance and technical parameters .
Along with the reduction of the dimensions of the pharmaceutical extruder, there are objective physical and technical factors leading to a reduction in the possibility of supplying mechanical energy to the plasticizing system. the capacity of the extruder to transport such materials is compromised The throughput of the extruder must be reduced to a lower value, which is often a challenge in terms of feed uniformity Cohesive powder materials place high mechanical stress on the extruder, generating a high demand for mechanical power This affects residence time of the material in the extruder and sometimes on the properties of the final productAn iconic issue is the ability to scale down the equipment in such a way that it is effective to the general o use due to varying process conditions for test productsFactors affecting upscaling or downscaling include volume, heat transfer and mass transfer distributing and homogenizing mixingThese factors affect both the delivery equipment and the design of the plasticizing system of the pharmaceutical extruder which is responsible for the flow and quality of the extrusion process The downscaling of the process, along with the reduction of the geometries of the barrel and screws of a pharmaceutical extruder, is a key factor as the general concepts of scaling used in large extruders fail. For example, the concept of geometric similarity has a range that becomes invalid when using small extruders. is the relationship between the surface area and the volume of the components that affect friction and heat transfer.Another problem with scale-down is that the properties of the substance, such as particle size and viscosity, remain constant while the machine gets smaller. The pharmaceutical extrusion process may also be affected.
Our company has put a lot of effort into the process of miniaturization of components in the pharmaceutical extrusion technology. We offer various types of miniaturized extruders that differ in diameter and length of the plasticizing system, but also in construction.
The first group of machines was designed for early development as it can be started with just a few grams of material RES-2PN 2x12mm-Pharma, RES-2PB 2x12mm-Minilab, RES-2PM-Minilab.
The second group of our extruders includes reduced size extruders RES-2PN 2x16 mm-Pharma, RES-2PM 2x20 mm-Pharma, RES-2PM 2x20 mm-Pharma.
All our extruders intended for pharmaceutical extrusion are connected by high functionality, high technical parameters and, which is a unique possibility of operation as co-rotating and counter-rotating extruders. The process of changing the direction of rotation of the extruder screws is automated thanks to the developed Vertex II technology..
Extrusion using extruders is a method of processing polymeric materials that is of great economic importance, as more than 50% of plastic materials produced are processed thanks to this process. Extrusion (extrusion) is not an easy process to carry out in practice. range of phenomena occurring in the plasticizing system of the extruder It is necessary to have knowledge in the field of material science and technology in the field of plastics processing The extrusion device is a difficult object to control Problems may occur in the plasticizing system of the extruder or in the process of forming a polymer material Conditions in the extruder, such as high temperature, high pressure , significant shear stresses and the presence of various fillers may cause accelerated wear of components of plastics processing machines. The extruder is built of three basic systems in: drive, control and plasticizing, as well as auxiliary components In the extrusion process, a very important role is played by the plasticizing system of the extruder, built of a cylinder and screw [screws], which is a key component of each extruder The specific type of the plasticizing system of the extruder is selected adequately to the specificity of the processed material The screw of the extruder corresponds because for the quality and consistency of the extruded material, there are many possible configurations of screws used in extruders. The key parameters of the extruder are the quality of plasticization of the material and its homogenization, i.e. thorough mixing of ingredients. In the cylinder, as a result of the rotation of the screw [screws, the material is transported towards the head. into the heated zone, where it is melted and then materially and thermally homogenized The plasticized and mixed melt is fed with appropriate efficiency and with the appropriate pressure to the extruder head, where the material is formed taking the shape of the mouthpiece.
The complexity of plastics extrusion issues is evidenced by a large number of design solutions used in the design and manufacture of extruders.
In the extrusion technology, plasticization is of decisive importance, i.e. the appropriate transition of the input material as a result of heating, compression, movement and forces from a generally solid state to a plastic state. This process is the most important factor determining the extrusion efficiency and the quality of the obtained extrudate. specific parameters, i.e. temperature, pressure, degree of homogenization, speed of movement and flow rate. There are larger or smaller fluctuations of these values, characterized by a specific period and a given amplitude.
The processing zones of the extruder screw are defined by the changing height of the screw channel:
Geometrical dimensions that characterize the extruder screw:
Figure 1 geometrical dimensions of the extruder screw
In extrusion, the angle of the helix is the angle between the helix and a plane transverse to the axis of the extruder screw. For most applications, the pitch of the extruder screw is equal to its diameter. Volumetric capacity depends on the angle of the helix. ), then the volumetric efficiency is 45.4%.
The energy used to rotate and pump the plastic forward of the extruder's plasticizing system is converted to heat Since the material is also sheared, the heat generated is known as shear heat Shear heat is not evenly distributed throughout the material, but is greatest where the shear rate is highest The amount of heat released can be high enough to cause localized overheating and decomposition of the material or its degradation For a given material, the amount of shear heat generated depends on the speed and diameter of the screw If possible, the size of the extruder should be matched to the expected capacity It is possible to achieve the required capacity with a small diameter of the extruder screw operating at high speed or with a larger diameter machine running slower It is generally stated that a larger machine will melt at a much lower temperature and achieve higher resultsFor this reason extruders running at high RPM should be equipped with efficient cylinder zone cooling systems.
The pitch of the extruder screw is defined as the distance between two consecutive turns.The pitch of the worm screw is directly related to the angle of the worm helix, which is the angle between the thread of the screw and the plane perpendicular to the axis of the screw If the pitch is to be equal to the diameter of the worm, it is called the square pitchNote that the square pitch is not always the optimal pitch for the design of the wormIn fact, the optimum pitch or alternatively, the optimal helix angle can be calculated based on the rheology of the extruded materials.
The compression ratio is an important parameter to evaluate when designing extruder screws. It can be determined by the ratio of the channel depth (or alternatively channel volume) in the feed section to the depth in the dispense section. The former is known as the depth compression ratio and the latter is the volumetric compression ratio. For special screws such as like barrier bolts, the inclusion of the volumetric compression ratio (VCR) is a more reliable design parameter than the depth compression ratio (CR) because the pitch of the driver also changes from the feeding section to the transition and gauge sections in their screw design It is worth mentioning that the CR value can also be a confusing parameter in screw designFor example, if the channel depth changes from 16mm in the feed section to 4mm in the dispense section, the CR is 4:1 However, the same compression ratio will be achieved if the channel depth changes from 12mm in the delivery section up to 3 mm in the dosing sectionThese two screws behave completely differently despite having the same compression ratioAn important parameter in the design of extruder screws, closely related to the compression ratio, is the slope of the transition sectionFor efficient melting, the compression ratio and slope of the transition section should be carefully matched to the melting rate of the processed polymer The degree of compression of the screw also depends on the compressibility of the materials being processed compression.
Another key parameter in screw design is the length to diameter (L/D) ratio. It is defined as the ratio of the length of the screw to its diameter. Typical screw L/D ratios range from 20:1 to 36:1 and even up to 52:1. lengths considered in screw design, which in turn depends on the application and the materials being processed. For conventional screws with three functional zones (i.e. feeding, compression and dispensing zones), the typical L/D ratio is 24:1 to 32:1. However, for processes where where a highly homogeneous and gel-free melt and melting at constant temperature and pressure are required, the need for additional sections is unavoidable. For example, one or more additional mixing elements are often added to the design of these screws to ensure uniform delivery of the melt to the die. Therefore, in these applications, the screw should be longer to accommodate added sections then typical L/D ratio for auger that used in extrusion processes is 32:1 In processes where degassing is required (so-calledscrew), screws with an L/D ratio greater than 32:1 are usually recommended.
The clearance between the screw and the extruder barrel is a measure of the space between the outer diameter of the screw and the cylinder wall of the plasticizing system Incorrect clearance will adversely affect the performance of the plasticizing system A small clearance can cause excessive wear on the screw, while a large clearance can reduce the melting efficiency of the screw to the accumulation of a thick layer of molten on the surface of the barrel, which reduces the thermal conductivity through the barrel. A large clearance between the screw and the extruder barrel can also reduce the pumping capacity of the screw due to excessive backflow of the material.
The extruder screw does not always ensure very good mixing of the extruded plastic This is due to the way the plastic flows or is transported along the plasticizing system The plastic transported in the direction of the longitudinal axis of the extruder screw may not be properly mixed For this reason, the material coming out of the machine will not be of uniform quality It will be heterogeneous because it has a non-uniform shear history Therefore, it is important that the plasticizing system breaks up agglomerates, ensuring good dispersion mixing. The second important action of the plasticizing system is to create a random spatial distribution of the processed material, ensuring distributional mixing.
To ensure high quality extruded material, there is a trend to use longer extrusion systems with a length to diameter ratio [L/D ratio] in excess of 25/1 Long plasticizer systems are used where high flow rates and excellent melt uniformity are required They will produce the same throughput as shorter layouts, but at lower extruder screw speeds This is especially important when a lot of heat is generated that needs to be removed from the system The use of a longer plasticizer gives greater flexibility in operation as there are more options for using shear and mixing elements Some extruders are 32 D to 52 D length.
Obtaining a product of the required quality with high efficiency is possible thanks to extruder screws equipped with appropriate material homogenizing elements, i.e. shearing and mixing, which are usually placed in the end part of the extruder screw. The purpose of the distributing elements is to homogenize the plasticized material leaving the shearing element. other configurations, which results in intensive mixing of the plasticized material. It should be noted that the use of these elements increases the power consumed by the drive extruder, and thus at the same time an increase in the temperature of the plasticized material Such an element acts as a choke, reducing the extrusion efficiency, but allows the process to be carried out at higher rotational speeds of the screw and ensures obtaining a properly homogenized material and optimal product quality
Today, many screws used in extrusion processes have a mixing element.This is due to the fact that obtaining a good quality product requires the supply of a very high quality plastic melt to the nozzle, which is not easy to achieve without a mixing section in the screw. There are basically two types of mixing in the extruder; dispersion mixing and distributive mixing In extrusion processes, dispersion mixers are mainly used to remove gels in the melt Distributive mixers are used to homogenize the melt, in particular to obtain a thermally homogenized melt This is an important problem in extrusion processes because poor homogenization has a detrimental effect on the final product quality, especially its homogeneity Many types of mixing elements have already been developed for both dispersion and distribution mixing, which are used in extruder screw designs Generally, high shear mixing elements are mainly used for dispersion mixing It should be noted that the high shear rate and consequently the high shear stress applied to the polymer melt when moving through the small gap of the barrier run, it can raise the temperature of the polymer meltMaddock twisted mixer, also called shear spiral mixer, has been optimized accordingly The pineapple mixer, typically used as a distribution mixer, continuously separates and combines different melt streams to produce a homogeneous polymer melt. , this mixer can be very helpful.
The geometry of the mixing and shearing elements of the extruder screw should be appropriately selected to the properties of the processed material. It should be taken into account when selecting the properties of the extruder's plasticizing system, including the head shaping the extruded profile. The length of the extruder's screw shearing and mixing elements is usually 2-3 DE. at a distance of 5-7 D from its endMixing elements are used as below:
The plasticizing system of the extruder should first provide dispersion mixing, and then produce distribution mixing. These two mixing processes can be repeated more than once.
A large number of dispersion mixing sections are available. They can be divided into three main groups:
There are many distribution mixing sections available, which can be divided into four main groups:
The barrier extruder screw is considered a state-of-the-art design that incorporates a separate melt channel to ensure full plasticization prior to the dosing section.The barrier screw design uses a secondary thread starting in the transition zone to separate the molten polymer adjacent to the primary thread from the unmelted plastic pellets, thus avoiding the development of a large melt zone in the primary channel which slows down the efficient melting of the raw material This screw also uses a full circumferential barrier at the end of the transition section to guarantee plasticization of the fully molten plastic prior to final mixing and pumping.
In the case of a non-barrier extruder screw, some of the bed of plastic pellets will disintegrate and be melted first The remaining unmelted pellets can only be melted by heat convection from the surrounding melt Heat convection melting is not an efficient mechanism for melting polymeric materials due to their limited thermal conductivity Therefore, unmelted polymer can still flow through the discharge end of the extruder, resulting in unwanted productBarrier screws can solve this problem by separating the molten and solid channels with a secondary scraper called a barrier scraper The barrier section where the main part of the melting takes place is located between the feeding and dispensing sections The barrier section usually replaces the transition section; however, there are auger designs with separate transition and barrier sections.
There are two main designs for barrier augers; constant depth and constant width As the name suggests, the channel depth for unmelted polymer pellets and molten polymer pellets remains the same in a constant depth design Channel width for unmelted pellets becomes narrower along the length of the screw, while the melt channel becomes wider In contrast, constant depth barrier screws widths have channel width for molten and unmelted polymer unchanged throughout the barrier section, while their depths are different; the depth of the solid material channel decreases and the depth of the melt channel increases.
The length of the extruder screw feeding zone should be the longer, the higher the softening temperature of the material, and sometimes its length is reduced at the expense of preheating the material. The length of the compression zone should be the greater, the higher the softening temperature and its range. softeningCrystalline plastics, melt in a small range of temperatures It can be only a few degrees, so screws with a short (1-2D) compression zone are used for their extrusion. The situation is slightly different in the case of easily deformable plastics, such as LDPE, where even two-zone screws a long compression zone, in which plastic granules, which have not yet been melted, are slowly compressed from the beginning. m of plastics in the form of powder will require a screw with a higher compression ratio than the same material in the form of granules. This parameter also depends on the viscosity of the material under extrusion conditions, and so for amorphous plastics with high melt viscosity, low compression screws are recommended to avoid intensive overheating sheared material and excessive load on the screw drive system. Small screw compression ratios, of the order of 2, are recommended for the processing of thermally unstable plastics. Such materials include PVC, for which too high a compression ratio could cause material degradation. For thermally stable semi-crystalline plastics, such as PE or PP, high compression ratios can be used of order 4 and above.The presented relationships would indicate the need to have a large number of screws to obtain optimal extrusion conditions with each change of raw material. In practical applications, this is an expensive solution. for LDPE can be used to extrude PP at slightly higher rotational speeds The screw for PS can also be used for processing PC after increasing the temperatures of the heating zones The screw of the general purpose extruder is designed in such a way as to suit the widest possible range of plastics Such a screw used in the extruder is not ideal response to the processing of any particular material..