2. Plastic Cam Bush for Transformer

The objective of the paper is to design and Analysis the injection mould tool for a cam bush of an High voltage transformer. Cam Bush is used as a indexing device in ON/OFF Load Tap changer device of high voltage transformer and serves as the connector between the indexing head and the power changing gears. The indexing head is connected to the gear by means of the shaft which is attached with the Cam Bush. The cam bush has two tail ends, one side is press fitted to the indexing crank circle and the other side is fitted to the driving mechanism. Each hole has different driving mechanism, when the indexing circle rotates and the crank pin engaged in the first hole the first driving mechanism turns on. The different type of power is obtained by means of changing the index position. Cam bush serves as the connector between crank circle and the gears. It is provided in the power changing indexing mechanism. The indexing crank circle has many indexing holes, but the mechanism has 6 drive, so the cam bush with 6 holes is provided in between the crank circle, speed indicator wheel and the shaft which is intersected in center and connected to the gears. This CAM BUSH is generally made with Polystyrene, Nylon6 and PVC. Due to high voltage regulating application this Cam Bush becomes heated up and wear off. Due to repeatedly applying pressure by regulating it, it becomes damage.

Fig.1 Cam bush Solid Model and Assembly

Plastics are man-made materials. They are less brittle than glass, yet they can be made equally transparent and smooth. They are light weight and at the same time possess good strength and rigidity. They resist corrosion and the action of chemicals. They can be easily molded to different shapes. Commonly used thermoplastic materials are Polystyrene, Nylon 6, P.V.C , Polypropylene etc. Mould making is an important role in plastics industries because the related products constitute more than 70% of the components in consumer products. Injection moulding is a complex but highly efficient means of producing a large variety of thermoplastic products and has many advantages, such as short production cycles, excellent surfaces of the products, and has no secondary operations, good results in moulding of complicated shapes. The design and fabrication of injection moulding tool for complex plastic products is play a wider role to meet the industrial demand especially in plastic industries. Hence, there is a demand in the industry for plastic injection moulding techniques capable of producing plastic parts. Literature review reveals that there is a lack of research on design and manufacturing of injection moulding tool for complicated plastic components. Hence, this project focused on design and Analysis of Injection moulding tool with baffle type cooling channel and submarine gate for cam bush.

3. Injection Moulding Process

It is a manufacturing process for producing parts by injecting liquid molten material into a mould. Injection moulding can be performed with a host of materials, including Metals, Glasses, Elastomers, Confections and most commonly Thermoplastic and Thermosetting polymers. Material for the part is fed into a heated barrel, mixed, and forced into a mould cavity where it cools and hardens to the configuration of the cavity. After a product is designed, usually by an industrial designer or an engineer, moulds are made by a mould maker (or toolmaker) from metal, usually either steel or aluminum, and precision-machined to form the features of the desired part. Injection moulding is widely used for manufacturing a variety of parts, from the smallest components to entire body panels of cars. The part, the desired shape and features of the part, the material of the mould, and the properties of the moulding machine must all be taken into account. The versatility of injection moulding is facilitated by this breadth of design considerations and possibilities Injection molding utilizes a ram or screw-type plunger to force molten plastic material into a mold cavity; this solidifies into a shape that has conformed    to     the     contour     of     the     mold.     It     is     most     commonly     used     to     process both thermoplastic and thermosetting polymers, with the former being considerably more prolific in terms of annual material volumes processed.