PRODUCTION

PRODUCTION PROCESSES CLUSTER




Before going into the production process of different plastic materials, it will not be out of the objectives of cluster to mention what this plastic is. A basic knowledge of plastics what they are and how they are produced and the types of products in common use, will help in assessing the production process.


Plastics are produced from natural resources such as oil, natural gas, coal and common salt. Even in developed countries only 4 to 5 percent of commercially produced oil is used in production of plastics.


One of the main characteristics of plastics is their retention of an inherent energy content, which can be recovered.


A process called polymerisation, the chemical bonding of monomers into polymers, produces plastics. The size and structure of the polymer molecule determines the properties of granules, liquids and solutions. The applications of heat and pressure to these raw materials produce the familiar products of everyday life.


The varieties of plastics may be as different from each other as copper is to aluminum in the world of Metals. However, plastics can be broadly divided into two categories in terms of processing. Thus


Thermoplastics

Thermosets

Most of the products of Balasore Plastic Cluster are made of thermoplastics. Common thermoplastics used in the cluster are HDPE, LDPE, PP and PVC. The chronology of manufacturing processes involved is generally as follows -

Mixing or Compounding:

Properties of polymers may be modified to meet specific properties requirement like mechanical strength, thermal properties & other characters of the product for end use application. Thus the plastic materials are mixed/ blended with other additives like filler, plasticizer, lubricants, stabilizers, pigments etc. under specified conditions.

Extrusion Blow Moulding:

Extrusion blow moulding is the prime and most vital process that gives the desired shape to the product. This process is carried out in a standard extruder “Barrel and Screw assembly” to plasticise the polymer. The mixed raw material is continuously fed in to the extruder hopper through suction pipe and passes on to the Barrel and Screw. Inside the extruder, the raw material passes through an increasing order of temperature up to a maximum of 270 °C, generated by electric heaters. During this flow it starts melting and passes on to the pre-shaped dice through the screw.

In certain cases, custom moulding is designed but the same is usually not practised in this cluster.

Machines are available with manual, semiautomatic and automatic operation both in either conventional and microprocessor controlled system. Nowadays most of the companies are using microprocessor controlled system to achieve close tolerance and zero waste / defects.

Injection Moulding:

The mixed raw material is fed in to the hopper and compressed under high pressure to flow in to the pre-shaped dice. Here also the raw material is melted through different stages of temperature maintained by electric heaters.

Cooling:

The Extruded plastic product is immediately immersed in water connected to a chilled water system, which creates necessary heat transfer to solidity the plastic.

In the plastic blown film process, passing it across a finned heat exchanger, which is supplied with chilled water, can chill the air blown in to the bubble. The air-cooling or chilling system can have the effect of improving the clarity and quality of the film and speed at which it can be produced

Blow moulding of Plastic Containers

Extrusion Machine for manufacturing of PVC pipes.

Cutting:

The extruded pipe is printed automatically with a digital printer and cut to size. In woven sack manufacturing process, the extruded film is cut to tapes.

Belling & Stretching:

The pipe cut to size is expanded at one end purposefully with the help of belling machine. In woven sacks or thread making units, the tapes/ threads are stretched over a hot surface called Godet to a length 4 to 5 times longer than the original. The stretching is necessary for enhanced tenacity and luster of the tape/thread.

THREADING / SPINNING:

The leveled pipes are taken to lathe where threading is done. The threaded pipes are packed for marketing. By RND, there is recent technology that pipe-to-pipe connection is made without threading.

The stretched tapes/threads are wound around bobbins in case of woven sacks/net making units.

WEAVING:

The tapes/threads wound around bobbins are woven in looms to form sacks/nets.

The woven sacks are cut to size, stitched in stitching machines, printed and packed for marketing.