Extrusion Fundamentals, Materials & Industry Trends

The invention relates to a screw extruder for working plastic compositions, especially polymers and rubber mixtures, consisting of a cylinder in which a motor-driven screw is disposed, the cylinder of which is provided with pins which are arrayed in several planes perpendicular to the cylinder axis and can be inserted radially through openings in the cylinder wall, and the screw is provided in the spirals of the screw with gaps disposed in the planes of the pins.

Such screw extruders are disclosed in German Patent 137,813 and U.S. Pat. No. 1,848,236. The pins extending radially into the extruder cylinder improve the kneading and mixing of the material, and in many cases they have made such kneading and mixing possible for the first time.

When the screw is changed and when the extruder is to be cleaned these pins have to be removed and then reinstalled. When the pins are threaded in place it becomes possible to adjust their depth, which is done for the purpose of reducing the screw resistance by having the pins reach less deeply into the cylinder and to improve the kneading and mixing action by setting the pins deeper.

Occasionally there is a desire to be able to vary the pin depth rapidly and without consuming too much time between zero and maximum for reasons relating to the process. Pin extruders for working rubber mixtures which are not preheated have attained great economical importance when constructed in accordance with German Patent 22 35 784. The mechanical fine pin adjustment operating with spiral plates is rarely used, however, for reasons of cost. The movement of, for example, eight pins in a single pin plane also requires considerable power and thus causes great wear on the adjusting means. For the numerous pin planes, amounting to about six to sixteen planes, this adjustment is furthermore quite time-consuming. Therefore there is a need for a rapid adjustment of the pins for the purpose of losing as little time as possible when the screw has to be replaced for technical reasons with one of a different shape, or because it is worn, or for cleaning purposes.

German Patent 35 03 911 has disclosed a hydraulic pin adjustment which permits the pins to be driven all the way in and backed all the way out, each pin being constituted by the plunger of a hydraulic cylinder. For each pin a separate hydraulic cylinder is provided. The possibility of achieving specific, defined pin depth settings has been practically unattainable on account of the immensely great complexity of the controls required. Even the complete plunging and extraction of the pins is so structurally complex that such hydraulic pin control has not become established to any great extent.

A pin adjuster that appears to be mechanically very simple, and which theoretically also offers the possibility of any desired depth adjustment, has been disclosed by German Patent 35 06 424. The disadvantage of this type of construction using Kellen drives for the screw movement producing the axial movement of the pins lies in the fact that extremely great friction is involved, which renders unfunctional any design based on this principle, and therefore it has never been used in actual practice.

The present invention avoids the disadvantages of the state of the art. It is the aim of the invention to create a practically usable and economical possibility for rapid pin movement and depth adjustment on screw extruders.

Extrusion is widely used for about half of all plastics product manufacturing. Mostly by using single screw extruders, plastics products are manufactured. Most of these products contain a very wide range of additives, mainly in the form of masterbatches. These range from visible colours to the invisible traces of anti-block and slip additives. There are also continuing pressures to improve overall efficiencies and these require increased mixing performance in many cases.

Extruders are widely used in industry. There is a variety of extruders, such as twin screw extruders, single screw extruders and so on. A lot of plastics products are extruded and most of those products contain additives, which mean that the plastic must be mixed at some point. Mixing is generally done with these extruders, which is used in the product production. A former principal consultant at Smithers Rapra has written a reference handbook to introduce the screw extruders.

In food processing, extrusion combines heating with the act of extrusion to create a shaped cooked product. Extrusion is accomplished by single screw extrudersand twin screw extruders.The choice of extruders is determined by the moisture content of the extrusion feed mixture. Low moisture extrusion mixtures appropriate for a single screw extruder must have a feed composition of less than 35% moisture. High moisture extrusion mixtures, those with a moisture level of 35% or above, require the use of a twin-screw extruder.The 13.5% (w/w) moisture content of the extrusion mixtures used throughout this study was applicable to a single screw extruder.

The extruding formation can also be called as extrusion molding. It is a forming method that with the help of the extrusion affection of screw or plug screw, and the uniform plasticization melting plastic can pass the mouth model forcibly so that it can form series of products with constant cross-section.

Extrusion forming is mainly used to forming thermoplastics and the forming fashioned product includes the covering of tubes, rods, plates, wires, films, cable wires and aluminum profile with a variety of cross-section shapes. In exceptional circumstances, extruding formation can also be used to forming several kinds of thermoplastic plastics.

The general working process of plastic extruder is adding the graininess plastic into the hopper when extruding, then extruding the material in the barrel along with the rotation of screw and the electricity heating of the out wall of barrel, and lastly producing melt plastic.

With the continuous improvement of modern extrusion technology especially the usage of high-speed extruding of latest-type screw and latest material (such as cross linking polyethylene and so on), the high-precision control system is needed in order to make sure the quality of high-speed extruding and original material saving.

According to the number of screw, extruders can be divided into single screw, twin screw and multi-screw extruder.

At present, the single screw extruder has been the most widely used in the world, in general the extrusion processing of materials.

Due to less heat generated by friction and average material shear, twin screw extruder has greater transmission capacity with advantages of stable extrusion volume and mixed evenly.

However, the characteristics of the conical twin screw extruder are as follows: forced extrusion, high quality, wide adaptability, longevity, small shear rate, hard to break down materials, good mixing performance plastics, direct molding and so on with the temperature-controlled, vacuum exhaust and other devices. It is applied to produce tubes, boards and special-shaped materials.

Generally speaking, multi screw extruder refers to an extruder with tri-screw or more screws, which is designed at the aim of more effective processing. Compared with single and twin screw extruders, it has a limited market. Planetary extruder is one of the multi-screw extruder that is relatively popular in recent years. It is effective as a mixed feeder of formation processing, and apt to extrusion processing of common plastics.

In a pipe extruder, there are two steps in production. The main machine is a conical twin screw extruder. Firstly, a mandrel pierces a hole through the center of a billet, and the tip of the mandrel ends up just within the opening of the extrusion die. Second, the now hollow cylindrical billet is extruded through the die and over and around the tip of the mandrel. The process produces a pipe. To limit the movement of the mandrel, stroke-limiting rods pass through bores in a part attached to the mandrel and in a fixed part of the press. The rods can be held fast in one or both of these bores, or released to slide through them, depending on the stage reached in the extrusion process.

Low-priced Chinese-built extruders such as the single screw extruder and twin screw extruder have arrived in North America and Canada to make PVC pipes, sheets, films, and profiles. For the Chinese extrusion machine industry, this is good news. But there are some problems with the Chinese extruders, too. The most frequent general problem encountered has to do with the electrical compatibility issues, ranging from relatively benign—e.g., replacing a Chinese controller with a U.S.-made one—to much more significant. Wires, for example, might be the right color but too thin to meet our electrical codes. In the worst cases, processors had to call in electrical contractors to rewire entire machines to bring them up to code, and this can be very expensive.

Therefore, some of these North American buyers felt good about their purchase and ordered more machines, while others were not as happy with their purchase because of the problems they experienced.

The main trend of plastic machinery such as twin screw extruder is with portfolio structure, specialization, serialization, standardization, micro-and large-scale, personalization, and intelligence. Users can do the “mix and match” based on their actual requirements. Besides, a lot of new type equipment and special purpose equipment have been developed, due to the requirement of technological principle of power, material saving and special application.

In recent years, twin screw extruder extremely has a strong market, but relatively speaking, single screw extruder has been in a state of silence. However, the single screw extruder, as basic plastic processing equipment, enjoys the fame of simple structure, lower cost and greater design flexibility. A variety of special single screw extruders now have attracted people’s attention.

Screw extruder because of its simple structure, good value for money and high production efficiency, has been playing an important role of processing, like the formation of plastic pipe, plate, sheet, etc. With the continuous advancement of technology, as well as people’s awareness of screw extruder, a number of extruders with different structure have come into being.

In recent years, twin screw extruder is in a high rate of development. However, due to more and more studies on extrusion technology and continuous improvement, it is a tendency that special single screw extruder will replace multi-screw extruder in processing technology.

Coating Plant for Steel Pipe Rubber Extruder
A means for the extrusion of an extrusion composition through a plastic extrusion apparatus having anelongated extrusion barrel features an elongate extrusion screw rotatable there within to convey solid extrusion composition from a feed section of mentioned barrel to and through a solids conveying section to a compression setting for its melting down and to a downstream extrusion orifice for the extrusion of the melted down mixture mentioned above, said method consisting of the said extrusion barrel with a plurality of axial grooves which enlongate through the feed section and the solids conveying section and which disappears at the terminal part of the compression section of the barrel, and providing said extrusion screw with at least one helical screw thread ,providing a helical vaulted screw channel or channels having a maximum depth in the area of the feed section of the barrel and a deminshing depth in the area of the compression section therein, which channel or channels disappear(s) at its exit end, whereby solid extrusion composition is fed through to the feed section of the barrel is compressed by the vaulted screw channel or channels into the axial barrel grooves to create a rotation-resistant mass which is moved axially by the screw to substantially fill the solids conveying and compression sections of the barrel, which, increases the dead head pressure exerted by the extrusion composition and increasing the output of said composition from the extrusion orifice.

It is an object of the present invention to provide a single screw extruder with enhanced coupling to a drive shaft to reduce radial movement of the feed screw when subjected to high loading.

Other and additional objects will become apparent from the description as set forth in the specification.

In accordance with the present invention, there is provided a single screw extruder of the type having a drive shaft coupled to the screw for rotational movement wherein the improvement comprises coupling the drive shaft to one end of the screw through a plurality of splines on the screw.

According to preferred embodiments, the respective ends of the screw is coaxially aligned with the drive shaft and coupled together with a sleeve having a plurality of serrations matching the respective splines on the screw.

Screw extruder for working plastic compositions, especially polymers and rubber mixtures having a cylinder in which a motor-driven screw is disposed. The cylinder being provided with pins which are disposed in planes perpendicular to the cylinder axis and can be pushed radially through openings in the cylinder wall, and the screw being provided in the pin planes with gaps in the screw spirals. The object of the invention is to create a practically achievable and economical possibility for the shifting and depth adjustment of pins in screw extruders. A plurality of pins, lying in an axis parallel row, are fastened to a beam at the extremities projecting from the extruder cylinder.

A screw extruder for working plastic compositions, said extruder comprising: a cylinder having radially directed bore holes extending there through, said bore holes being disposed in at least two planes perpendicular to the cylinder axis and said bore holes of adjacent planes being aligned parallel to the axis of said cylinder; a rotating spiral screw disposed in said cylinder, said screw having at least two adjacent circumferential grooves forming gaps in the spiral, said gaps corresponding in position to said adjacent bore hole planes; pins corresponding to said bore holes, said pins being radially disposed about said cylinder and having an inner end extendible through said bore holes and into said spiral screw gaps; a beam fastened to an outer end of at least two pins, said at least two pins being aligned in a row parallel to said cylinder axis; stud means for jointly connecting said pins to said beam, said stud means being guidingly engaged in corresponding slots in said beam so as to allow angling of said beam with respect to a normally parallel adjustment of the beam and the cylinder axis; and two drive means disposed at opposing ends of said beam for displacing said beam, whereby said opposing beam ends are independently displaceable by said drive means, thereby controlling the depth to which said at least two pins extend into said screw gaps relative to one another

PET is strong, lightweight and is still improving its recycling track record. Last month Petcore announced that European post-sorting PET collection reached 1.26m tonnes in 2008 (an increase of more than 11% on 2007) and that the overall collection rate rose by nearly 5%, from over 41% to 46% of all PET bottles on the market.

In its everyday form PET packaging provides an excellent barrier to gases and water vapour which keeps content fresh and untainted for many, many months. PET minimises the use of fossil fuels during manufacture, forming, transport and storage. There are many more products that can be packaged in PET. Perhaps we in industry are not communicating effectively with our value chain (internal) and our final customers (external).

Petcore has devoted a significant amount of time to updating our communications strategy. We want to be in tune with our world of today. After industry consultation Petcore has put together a factual document called PET Profile which extols the tangible and positive benefits of PET and the reasons for its success. Too often the media concentrate only on emotional and negative aspects of purchasing products that are protected and packaged in PET.

Petcore has devoted two of its PET Planet Columns to countering the illinformed media stories about PET that are presented as fact. PET does not leach cancer-forming chemicals and PET does not leach oestrogenic compounds. PET does not contain or form Bisphenol A (BPA) or phthalates. Incidentally, BPA and phthalates are some of the most widely studied and understood chemicals in the world. A simple examination of the rigorous EU risk assessments and studies by other internationally respected scientific bodies have consistently demonstrated the safety of BPA and food contact phthalates for their current uses.

A process for manufacturing an all natural, enzyme-saccharified, cereal comes from whole grain is below. The processes of involves milling and separating the whole grain to produce a bran fraction, an endosperm fraction, and a germ fraction. The germ fraction is processed by toasting and grinding and preferably by removing bran before the toasting. The bran fraction and any bran material separated out from the ground germs are modified to increase its functionality by high temperature, high shear extrusion in a counter-rotating twin screw extruder. The fraction is roughly milled, made into slurry, cooked and then enzymatically hydrolyzed. The germ fraction is processed by toasting and grinding and preferably by removing bran before the toasting. The final step involves recombining the processed fractions, to engender cereal dough which is further approached to produce a ready-to-eat breakfast cereal. Optionally from 1-15% of the whole grain may be malted and increased into the cereal dough.

Crusher Haul-off
A method for manufacturing a ceramic article is made up with the steps of affording a plasticized ceramic precursor batch composition which is constituted by a liquid vehicle, an inorganic ceramic powder batch composition, and an organic binder system comprising at least one organic lubricant grafted to a cellulose ether binder. An extruded green body can be created from the plasticized ceramic precursor batch composition and subsequently fired under conditions effective to change the extruded green body into a unitary ceramic article ,simultaneity provided are ceramic articles manufactured by the methods said at this place.

Rubber Extruder Vacuum Powder Loader

A new and beneficial a plastic article, particularly plastic siding, with an accent color pattern incorporated in it, a specially structured accent color pellet which is useful in yielding such an article, and a process for producing the article adopting the provided pellets. The process and uniquely formed accent color pellets. The accent color pellets are alloyed masses of resins and pigmentthat are bigger than the powder particles of the base material, and also, possess a higher vicat softening point temperature than that of the base material. The alloyed pellets are designed to melt controllably and to mix controllably with the base material. During the extrusion process, the accent color pellets set about to soften and disperse later than the base material, and result in controllable dispersion of the accent color into the base material, thereby producing accent color streaks in the resulting product having controllable characteristics. The process is particularly suited for producing a pseudo wood-grain or streaking effect in plastic siding, and as described can create hard streaking, soften streaking, and a mottled or variegated streaking in which more than one accent color is used at the same time. A novel formulation for the accent color pellets is put forward, in which poly-α-methyl styrene is used as the only high vicat softening temperature resin.