Extrusion is a process which can be used to manufacture objects by melting and reforming the raw material. Usually this is performed as a continuous procedure which transforms the material within a screw or sleeve. This is a flexible and widely used technology which can be used in a wide variety of situations. For example in the food industry an extrusion cooking process enables manufactures to reliably diminish microorganisms in the product, inactivate food enzymes and remove any naturally occurring toxins.

In industrial manufacturing the process is now relatively simple. Raw materials (usually in the form of small beads) are fed into an opening at the rear of the sleeve. A screw forces the beads along the sleeve which is heated to the temperature required to melt and mix. In most cases the temperature of the sleeve increases as the beads are passed along it allowing the plastic to melt gradually. A filter (known as a breaker plate) is fixed to the front of the sleeve to remove any clumps or unwanted contaminants before the mix enters a mould or die. The die gives the product its shape and is designed so that the plastic flows smoothly and evenly around it to prevent stress points which could cause warping on cooling. The product is then cooled by passing through a water bath.

Screw design is very important and most of them have three areas.

. The feed area, forcing the beads into extruder
. The melting area
. The final metering area that melts the last beads and mixes them to a uniform temperature and composition

Twin screw extrusion is an important modification and uses a machine which houses two screws inside the bore of the sleeve. They are now used in the polymer processing industry for the profile extrusion of temperature sensitive materials and speciality operations like compounding and the fine control of chemical reactions. Typically twin screw extruders can work at lower speeds of around 20 rpm and provide more reliable feeding and conveying. These characteristics allow the machine to accommodate hard to feed materials like powders whilst also providing better mixing and heat control. Most twin screw extruders used in profile extrusion are intermeshing and counter-rotating.

A twin screw extrusion system enables a manufacturer to maintain high melt quality and efficiency and thus maintain their competitive advantage. The pharmaceutical industry makes significant use of this technology where continuous processing allows productivity and quality improvements over traditional processing technology. Importantly batch to batch variation is eliminated by continuous production. Twin screw extruders also enable small scale continuous processing of materials for research and development. At the manufacturing level it enables powder coating and polymer modification. One practical outcome relates to the manufacture of slow or controlled release drugs. These are of great advantage to the patient. The ability to take one tablet that slowly releases a drug makes it much easier for a patient to remember to take the correct effective dosage. This is important for two reasons. Firstly, a treatment only works effectively when taken at the right dosage. Secondly, when a treatment is regularly missed this imposes huge costs on the NHS in terms of wasted drugs and uncontrolled symptoms that get worse rather than better. When you bear in mind that up to 50% of people regularly forget to take their medication you get some idea of the financial implication of the problem.

The flexibility of this type of extrusion, allowing for small batches and operations to be designed for the formulation being processed, means that twin screw extrusion is extensively used in the food and pharmaceutical industry.

Twin screw extruder included a pair of screws extending along parallel axes relatively close to one another. To assure uniform extrusion flow, the screws were required to be driven both at the same speed.

In some instances twin screw extruder were driven in the same direction of rotation, while in other instances each compounding extruder was driven in an opposite direction. This, of course, depended upon the screw configuration. Relatively high torques were required to drive the screws.

A drive system suitable for driving a twin screw extruder as constructed in accordance with claim 1 further including bearing-free means for supporting the ring gear for rotation about the axis of the sun gear, the bearing-free supporting means comprising the engagement between the ring gear and the planet gears.

We, Faygo Union, can provide high quality twin screw extruder for kinds of plastic pipe or profile extrusion line.

Here, we present extensive analysis and calculations of screw-pumping characteristics in intermeshing, counter-rotating twin screw extruders and compare them with experiments. We used the flow-analysis-network method—which is based on hydrodynamic lubrication theory—to model pumping characteristics. The flow path through the compounding extruder consists of two regions, one between the screw and the barrel, and the other between the screws.

In summary, we considered the effects of screw-flight thickness and channel depth, as well as non-Newtonian fluid behavior, in our simulations of screw characteristics for intermeshing, counter-rotating twin screw extruder. We achieved improved prediction by considering screw-flight shearing, which was experimentally verified. This model will next be included in our global model for extruders.

We, Faygo Union, can produce hight quality twin screw extruders for kinds of plastic production line, such as pipe production line, wpc extrusion line, profile extrusion line etc.

Reference: Wikipedia

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GUANGZHOU, CHINA (June 17, 2011) — China’s plastics machinery industry continued to grow in the first quarter, but the speed slowed down, according to data released by the China Plastics Machinery Industry Association (CPMIA).

The country produced 66,149 units of plastics machines in the first quarter, up 17 percent from 54,904 units in the same period a year ago, said Qian Yaoen, executive vice president of CPMIA.

Total output value of machines reached 9.75 billion yuan in the first three months, up 24 percent year on year. Sales reached 9.63 billion yuan, a 29 percent increase from a year ago.

“The industry has maintained good growth,” Qian said.

However, the first quarter growth rate is significantly lower than that of 2010.

China produced 42.1 billion yuan of plastics machinery in 2010, up 63 percent from 2009, while sales reached 40.01 billion yuan, up 60 percent.

Qian said the industry faces increasing pressure and challenges due to a series of macroeconomic factors, such as rising costs and the appreciation of yuan.

He added that the industry achieved high growth in 2010 partly because market demand, from both domestic and overseas markets, was constrained in 2008 and 2009 during the economic downturn.

For the coming few years, Qian said the industry targets an annual growth rate of 12 percent, with annual output value and sales reaching 50 billion yuan by 2015.

Extrusion may be continuous (theoretically producing indefinitely long material) or semi-continuous (producing many pieces). The extrusion process can be done with the material hot or cold.

Commonly extruded materials include metals, polymers, ceramics, concrete and foodstuffs.

Hollow cavities within extruded material cannot be produced using a simple flat extrusion die, because there would be no way to support the center barrier of the die. Instead, the die assumes the shape of a block with depth, beginning first with a shape profile that supports the center section. The die shape then internally changes along its length into the final shape, with the suspended center pieces supported from the back of the die.

SWP Series Plastic Crusher

SWP Series Plastic Crusher