Process

Rotomoulding Process classified in the following sub processes.

  • Compounding to produce colored Granules
  • Pulverising to convert material in to Powder form
  • Rotational Molding to produce the final product.

Compounding of the granules by Extrusion

The L.L.D.P.E. raw material with suitable master-batch is being fed in to the barrel cylinder through storage hopper. The barrel is preheated by heating zones and suitable temperature control system to process the input material. The rotating screw pushes the material towards die end with uniform and homogenized plastics melt. The screw is rotated by suitable AC motor coupled with heavy duty gearbox. The plastics strands extruded from die are fed in to high speed Pelletizer unit after they get cooled and traveled through SS water cooling tank. Pelletizer cuts the strands in to desired size of pellets which can be collected in to storage silo.

Pulverising

The compounded or colored granules are being fed in to Pulverising machine as Input material. The granules are fed in to Disc Mill via vibratory feeder which feeds the material as pr rate of vibration of the device. The fed material is being crushed in to Mill at very high speed by one Rotating blade and one stationary blade. The crushed material is conveyed in to cyclone hopper at heigh via efficietn suction system. The Rotary Air lock devise seperates the blown air and pulverized resin and allows the powder passes in to Screen Vibro unit. Vibro screen unit the powder as per mesh used and discharge the final product in to the storage silo. The course particles are fed again in to the Mill to re-pulverize the same.

Compounding by means of High speed Mixer (Incase the Extrusion process is not used to produce the colored Granules) The pulverized resin is being mixed with other ingredients to prepare a ready formulation. This process is also being adopted by many processors instead of producing granules from Extrusion Plant.

In the process the polymers mixed with other ingredients is being loaded in to Mixer vessel. The mixer vessel is made from special double wall construction of SS and MS Plates. In which the material is being mixed by means of specially designed two nos blades running at very high speed. The mixing cycle is decided by the certain set termperature. Normally batch time is 10 - 15 minutes depending upon grade, quantity and formulation of material to be mixed. After cycle time is over, the material is being discharged and collected in to silo. The final material is uniformly and homogenized mixed which is ideal to use as for Rotomoulding process.

Rotational Moulding

In the other plastic processes, like injection moulding, globe moulding and acquistion process the plastic materal is being melt at curtain high temperature and conveyed forward into die or mould by special designs screws unlike such processes rotational moulding is a very simple process in which it is easy to produce holow and seamless product of all sizes and profiles. Since rotational moulding is a very simple and economic process along with low cost moulds. It is a very popular in India especially to produce the water storeage tanks. It comprise of mainly four steps as per following.

  • Material Loading : The polymer powder is being loaded in to two parts Rotational Mould as per size and shape of product. After loading material manually in to mould, the mould is closed. According to type and shape of Mould, some times the mould are also closed by insultating covers.
  • Rotational Molding : The closed Moulds mounted on to Arm are swing in to closed heating chamber where Hot an forced Air is circulating. The moulds are already rotating in two perpendicular axis at certain low speed as per size of the mould. The moulds are in Rotation in two axis so as to distriute the loaded powder uniformly inside surface of the moulds. The muolds are heated by forced hot air in to chamber up to certain heating time. The material in to moulds fuses after heating and it forms a uniform layer inside the mould.
  • Cooling : Now the moulds are taken out form heating chamber and indexed to cooling station. Themoulds are cooled at cooling station by means of forced air or by spraying water where the moulds are in rotation mode in both axis. After certain cooling period, the raw material gets solidifies in to shape of the mould.
  • Unloading the finished product : The mould is taken to unloading/loading part where the mould is opened to get the finished product. After getting the finished product, again fresh polymer powder is being charged in to mould so as to keep ready for next cycle.