/webtest/epaper_i.php?lang=en&ID=444 SHINI PLASTICS TECHNOLOGIES, INC.

Special Reports

2011 Quarter 2 Issue 7

How to Select Plastics Auxiliary Equipment for Granulators

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Classifications of granulators

• Based on the rotating speed of main shafts, there are three types of granulators including low-speed, medium-speed and fast-speed granulators with the main shaft rotating speed of 20~30rpm, 200~300rpm and 400~600rpm respectively.


• Based on the functions, there are beside-machine granulators, centralized granulators, granulators for tubular materials and granulators for special materials. The beside-machine type is applicable for instant recycling of sprues out of plastics moulds and centralized type is mainly suitable for granulating wastes, rubber headed materials and defective products. Plastic granule is available for use only after being processed.


Model selection

There is no one and only standard type for granulators and some small-sized granulators can be replaced by the larger-sized ones for operation. Granulators from Shini are capable of meeting different requirements of customers. Some options should be well considered during selecting granulators such as the shape and size of material, characteristic and granulating volume (Total granulating volume per hour).



    Paddle Blades                                                                  Staggered Blades 


Also it is necessary to do analysis on the materials. For example, paddle blades are optimal cutters if materials had the shape of sheet, strip, shell body and middle hollow while staggered blades are optimal if it were solid core parts, water channels (Injection water channels and purges) and small accessories.


Confirmation for granulators models

The size comparison between material (The size in the thickest position) and cutting chamber is important. Generally the size of material should be 20% smaller than that of cutting chamber.


To select granulators in line with the thickness of solid-core materials is also feasible. For example, SG-14/24/16/20 series are suitable for sprues and small-sized materials with less than 10mm thickness; SG-23/30 series are suitable for materials with less than 20mm and SG-36 series for those with less than 30mm; SG-43 series is suitable for thickness between 60 to 100mm (SG-43 series has a relatively high cutting point, which is applicable for granulating thick and solid-core plastics); SG-50 series which has a big cutting chamber is suitable for large-sized shell bodies such as that of washing machines, refrigerators and air conditioners.


Model selection of granulators can be confirmed through comparing granulating capacity provided by customers with the parameters in the catalogue. However, the granulating capacity has a direct connection with kinds of materials and mesh size, thus it is considered a normal phenomenon if there was differences between granulating capacity and the data in catalogue.


Granulating for special plastics

• How to select granulators for elastomer flexible glue like TPE, TPR and TPU


Concerning this kind of model selection, firstly it is necessary to get an understanding on the features of flexible glues like rubber: they are elastic and hard to be cut up.


Materials of cutters should be V-4E with the hardness value amounting to HRC61~62 or other steels materials so that cutting force would be strengthened.


The cooling system has to be installed to reduce high temperature due to operation friction so that cutter shaft and cutting chamber can be cooled down.


About the handling of sieve, mesh size needs to be broadened as much as possible within acceptable limits. Also sieve surface should be processed with destaticization to avoid sticky materials.


• How to select granulators for the plastics added with glass fiber


Glass fiber plays a key role in plastic products for it is capable of improving performance of finished goods and enhancing the hardness. During model selection of granulators, the intensity of cutting chamber is the top concern because of the high requirement for a rigid chamber structure. In the issue, Shini adopts hardening treatment for cutting chamber and uses V-4E type of blades with the hardness value amounting to HRC61~62.