08-03-2011, 04:55 PM
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INTRODUCTION
The Polymer material are converted into plastic and used as tubes, sheets, foams, rods, adhesives, etc. The theological properties, softening, tempering, stability, the size and shape are important in describing the method. These methods are different kinds of plastics. Broadly speaking the method may be discussed under the following headings.
ABSTRACT
The project deals about the injection moulding machine. The main principle is to compress the plastic material in a barrel and the compression motion is developed by rotating the screw rod and sliding nut arrangement. The plastic material is heated by the heater surrounding the barrel. Then it is converted into molten state. The molten plastic is injected through the nozzle in barrel to the die by the compression force. After completing this process, we will get the product from the die. Commercial products like bushes, couplings, switches etc, can be produced.
FABRICATION TECHNIQUES :
1. MOULDING PROCESS
2. FOAMING PROCESS
MOULDING PROCESS :
In this process the plastic are fabricated under the effect pressure and heat and both thermoplastics and thermosetting plastics may be starting materials.
INJECTION MOULDING :
Thermoplastics are produced by this method. In this the material is softened by heating and the hot softened plastic is forced under high pressure into the mold, when it is set by cooling and the mold is ejected.
FOAMING PROCESS :
This involves the blowing of a volatile organic liquid. Which is entrapped into a polymer network resulting in the formation of foamed plastics. Foamed polystyrenes are produced in this process.
WORKING PRINCIPLE
The injection moulding process is best suited for producing articles made of thermoplastic materials. Here the equipment cost is relatively high but the main attraction is the amenability of the injection moulding process to a high production rate. In injection – moulding machine is shown in the process consists of feeding the compounded plastic material as granules, pellets or powder through the hopper at definite time intervals into the hot horizontal Cylinder where it gets softened. Pressure is
applied through a motorised driven piston to push the molten material through a cylinder into a mould fitted at the end of the cylinder. While moving through the hot zone of the cylinder, a device called torpedo helps spread the plastic material uniformly around the inside wall of the hot cyclinder sand thus ensures uniform heat distribution. The molten plastic material from the cylinder is then injected through a nozzle material from the cylinder in then injected through a nozzle into the mould cavity.
The mould used in its simplest form, is a two part system. One is movable part and the other stationary. The stationary part is fixed to the end of the cylinder while the movable part can be opened or locked on to the stationary part. By using a mechanical locking device, the mould is proper held in position as the molten plastic material is injected under a pressure as high as 1500 kg/ cm. The locking device has to be very skillfully designed in order to withstand high operating pressures. Further more, a proper flow of the molten material to the interior regions of the mold is achieved by preheating the mould to an appropriate temperature. Usually this temperature is slightly lower than the softening temperature of theplastic material under going moulding.
After the mould is filled with the molten material under pressure. Then it is cooled by cold water circulation and then opened so as to eject the molded articles. The whole cycle could be repeated several time either manually of in an automated mode.
