/webtest/epaper_i.php?lang=en&ID=457 SHINI PLASTICS TECHNOLOGIES, INC.

Special Reports

2011 Quarter 2 Issue 7

Discussion on the Importance of Plastic Process Auxiliary Equipment

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In plastics processing industries such as extrusion, injection molding, calendaring, hollow molding, film blowing and spinning, host machines satisfying the requirements are the necessary parts while plenty of auxiliary equipments completing all processes are the indispensable components. Therefore, product quality and corporate viability depend to some extent on the automation and rationalization of plastic process auxiliary equipment.


According to the functions, there are three kinds of plastic auxiliary equipments including feeding equipment, temperature control equipment and granulating and recycling equipment of rim leftover. And these devices provide a variety of functions in plastics process.


Feeding system providing high-quality material


Drying, conveying, metering and mixing equipments make up a complete set of feeding system for plastics process.


Drying equipment is applicable to pretreat hygroscopic materials like ABS, POM, PC, PA and PMMA before molding. During the processing of polyolefin plastics, highly drying is generally adopted to guarantee product quality. For instance, in the tubing production plus injection molding of random copolymerization polypropylene PP-R and polyethylene material for cross-linked polyethylene, material needs to be dried to the extent of moisture content. Based on the material moisture content of various products, various drying fashions and equipments are also under application. For the material loading of PVC granules, oven dryer is the optimal equipment. For the plastics with strong thermo sensitivity, rotary double-cone vacuum dryer is mostly used. But for the successive drying, direct-type hopper dryer is the first choice.


In regard to conveying system of conveying powder, air conveying with a combination of spring coil conveying system and Roots air blower is adopted and vacuum loader is suitable for conveying granules. The central feeding system is mostly applied on large-scale and automated production. Equipments in system are controlled via computers with all kinds of material enter mixers after passing metering devices by proportion. Each hopper is equipped with a level sensor to detect material quantity, which will control open or close of material tank in conveying pipes. The critical technique in central feeding system is the accurate metering of electronic scale, which will influence whether the feeding material quantity is right or not by proportion.


Temperature control ensuring product quality


Heating equipments during plastic process include the cylinder moulds used for extruder, injection molding and rolling machines, as well as heating controllers for forming rolls. Heating method under current use is the electric heating of heat transfer oil but not the complicated steam heating.


Heating equipment in plastics process mainly refers to the temperature heating controller applicable to cylinder mold and stack of extrusion, injection and calendaring production.


Recycling reducing costs


Throughout plastics process, there is 5~20% proportion of rim leftover in the total production quantity. More and more processors have realized that an effective recycle of these resources is greatly beneficial for company development. Currently there are various widely used plastics granulators, some of them suitable for granulate rigid and small-size material, recycling and pelleting soft plastic foam, shredding pipe or long tubing products and recycling the waste silk. The development and research of plastic recycling equipment are heading towards the features of low noise, easy operation and the continuous feeding with central hopper.


In the successive granulating of large-scale workpiece, plastics will be stirred and cut inside granulator with heat coming into being, which will render plastics elastic and hard to granulate. To eliminate these situations, a new type of granulator with cooling water jacket on machine shell is developed to ensure continuous operation and effective granulation of large scale material.