Single-Stage Grinding Process for Thick-Walled Materials
Herbold Meckesheim GmbH in Meckesheim, Germany, completely redesigned the SMS series of granulators, in order to master even difficult tasks in one single operation. The machines feature rotors 600 to 2,000 mm wide, with drive loads between 45 and 315 kW. The blades are designed in segments, which shows that easy and fast tool change was the major aspect in design.
The granulators grind the material in a single-stage process. This includes a number of benefits. In many cases, there is not enough space for a two-stage unit. Restrictions to the performance of preliminary granulation often affects the quality of the grinding stocks in an unfavorable way, especially considering the fact that thin-walled flakes feature poor flowability and bulk density. The need of frequent cleaning in case of small batch sizes may be another aspect in favor of single-stage grinding. In addition, two machines mean double maintenance and repair.
The key to single-stage design is the rotor concept. Only a rotor forged out of a single piece will guarantee the stability required. There are no weld lines, so nothing can tear. The manufacturer claims that the rotor blades cannot change position, because they are fixed to the rotor against a massive backstop. This design facilitates cleaning, too, with no "dead spots" where grinding stocks might sit.
Processing heavy, thick-walled semi-finished products of PE, PP, POM and PA, as well as thick-walled pipes and big purgings are typical tasks of granulators. However, not only thick-walled materials are difficult to cut. The same is true for aramid and carbon fibers, just as for composite materials. Neither are contaminated plastic materials easy to process. They are highly abrasive and apply high loads on the rotor and casing, if the grinder is equipped with blunt rotor blades. In this case there is a danger of cracks and fractures.
In particular, for abrasive materials such as glass fiber-reinforced plastics Herbold Meckesheim offers hard faced abrasion-free rotors and casings equipped with an exchangeable wear area.
Herbold Meckesheim GmbH
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