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Granulating methods are necessary when the specific surface of fine powders has to be decreased, and its bulk density increased. This will reduce the problems of charging in the loading of the equipment, so that the flow characteristics and accuracy during the pressing of tablets (for example) improve. Solids with low bulk weights are usually heavily ventilated, leading to a strong dust nuisance in the workplace. In addition, segregation of heterogeneous composites is avoided by granulating materials with different average particle sizes that are to be processed together. Fixing of the different particles to each other allows a further processing without significant loss of uniformity with regard to the composition.
Size Reduction - Granulation and Shredding
The developments over the past years in various plastics processing and materials have led to new developments in the design of size reduction equipment. From the processing of small runners from the Injection Molding Process to the processing of tires, large purgings, document destruction, medical waste, scrap from the thermoforming , film , blow molding process as well as post industrial and post consumer waste…They all have one thing in common…they can be sized reduced and reprocessed.
The function of a granulator is to allow the safe, easy feeding of scrap plastics into it feed hopper. A series of rotary cutters brakes down the plastics by cutting it against the stationary knives (bed knives). A sizing screen further classifies the particles into a more uniform size. The result is a good quality regrind that can be reprocessed.
Granulating Plastic Scrap
The function of a granulator is to process the plastic scrap with as little dust and fines as possible. This is achieved by many functions in the granulator but it all starts with the precision rotor alignment necessary for accurate cutting. A perfect example is trying to cut a piece of paper with new pair of scissors. This is very easy when the tolerance is tight between the blades. When the scissors ware and the tolerance opens it becomes difficult, if not impossible to cut the paper. This is the very same principle in granulation. The rotor alignment must be precise.
Feeding and Discharging Design
Various methods of feeding and discharging the machine are important factors in the design of any size reduction equipment. Application versatility is another very important function of size reduction equipment. The ability to process a number of different materials and thicknesses offer the processor a better value. Granulators are sized form the smallest 7x9 through Central machine ranging in size from 24x63 and larger.
Regrind As defined by ASTM D5033, is "a product or scrap, such as sprues and runners, that has been reclaimed by shredding and granulating for use in-house, and that may be dry blended by the molder with the same grade of virgin material."
An industrial shredder is a machine used for reducing the size of all kinds of material. Industrial shredders come in many different variations and sizes. Some examples of materials that are commonly shredded are: tyres, metals, car wrecks, wood, and plastics. However by far, the most common use of an industrial shredder is to shred high volumes of paper documents.
The largest scrap metal shredder in the world is the 9,200 hp (6,860 kW) Lynxs at the Sims plant at the mouth of the River Usk in Newport Wales with access by road, rail and sea. It can process 450 cars per hour.
Laws like The Privacy Act, HIPAA, FACTA and Sarbanes Oxley have moved shredding from being just a prudent business practice to an essential business function that protects companies from civil penalty and lawsuits.
Single Shaft Shredders
Single Shaft Shredders are designed with low RPM and higher torque allowing these machines to process heavy cross section with less HP. Multi knife cutting with the assistance of a feeding ram offer greater application versatility. Once again the basic principals apply: Precision rotor alignment, close tolerance cutters for greater versatility, ease of feed and discharge, safe operation, highest quality components and assembly and highest value to the customers.