Types of GearTrains

GearTrain Definition -

Geartrain can be defined as the combination of gears used to transmit motion from one gear to another.
A geartrain may consist of three parts :

1. Driving Gear
2. Driven Gear
3. Idlers

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Geartrain Define with its contents

 Geartrain can be defined as the combination of gears combined in such a way that they transmit motion from one gear to other.

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Injection molding and injection molding machines

 Making polymers is a fantastic science, as well as shaping plastic objects.
One of the most common methods of shaping plastic resins is a process called injection molding. Injection molding is accomplished by large machines called injection molding machines, which are classified mainly by the type of system that drives them: Hydraulic, electric, or hybrid.

Hydraulic injection machines uses ram system for its clamping mechanism. This type of machine is used by majority of molding companies.

Electric injection machines are driven by motors. Unlike the hydraulic machines, which continuously pump hydraulics to the cylinder throughout the whole molding cycle, an electric machine only makes use of energy during closing and opening of the clamping unit. It uses toggle system for its clamping mechanism in order to build up tonnage. It is also faster, quieter, and has higher accuracy, but it is also known to be more expensive.
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Special Casting Processes

Special Casting Processes:

The sand moulds may be used for casting ferrous and non-ferrous metals, but these moulds can be used only once, because the mould is destroyed after the metal has solidified. This will increase the cost of production. The sand moulds also, can not maintain the tolerance and smooth surface finish. In order to meet these requirements, following casting method may be use:

1: Permanent Mould Casting

A casting made by pouring molten metal by gravity into a mould made of some metallic alloy or other material of permanence is known as permanent mould casting.

2: Slush Casting

The slush casting is a special application involving the used of  permanent mould. It is used for casting low melting temperature alloys. This method is only adopted for ornaments and toys of non-ferrous alloys.

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“Pattern”- making, allowances and its types:

Pattern:

Pattern can be simply said as the replica of cast.A pattern may be defined as a model of desired casting which when moulded in sand forms an impression called mould. The mould when filled with the molten metal forms casting after solidification of the poured metal. The quality and accuracy of casting depends upon the pattern making. The pattern may be made of wood, metal(cast iron, brass, aluminium and alloy steel.), plaster, plastics and wax.

Pattern Allowances:

A pattern is always made larger than the required size of the casting considering the various allowances. These are the allowances which are usually provided in a pattern.

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Arc Welding and its types.

Arc Welding:
The arc welding is a fusion welding process in which the welding heat is obtained from an electric arc struck between the work(or base metal) and an electrode. The temperature of the heat produced by the electric arc is of the order of 6000°C to 7000°C. Both the direct current (D.C) and alternating current(A.C) may be used for arc welding, but the direct current is preferred for most purposes. When the work is connected to the positive terminal of the D.C welding machine and the negative terminal to an electrode holder, the welding set up is said to have straight polarity. On the other hand, when work is connected to negative and the electrode to a positive terminal, then the welding set up is said to have reversed polarity. The straight polarity is preferable for some welds while for other welds reversed polarity should be used.
Following are the two types of arc welding depending upon the type of electrode:
(A): Un shielded arc welding:
When a large electrode or filler rod is used for welding, it is said to be un- shielded arc welding.
(B): Shielded arc welding:
When the welding rods coated with fluxing material are used, then it is called shielded arc welding.

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Electrical Resistance Welding

 Electric Resistance Welding
It is a type of pressure welding. It is used for joining pieces of sheet metal or wire. The welding heat is obtained at the location of the desired weld by the electrical resistance through the metal pieces to a relatively short duration, low voltage, high ampere electric current. The amount of current can be regulated by changing the primary turns of the transformer. When the area to be welded is sufficiently heated, the pressure varying from 25MPa to 55MPa is applied to the joining area by suitable electrodes until the weld is solid. The various types of electric resistance welding are as follows:

(1) Spot welding
It is used for welding lap joints, joining components made from plate material having 0.025 to 1.25 mm in thickness. The plate to be joined together are places between the two electrode tips of copper or copper alloy.

(2) Roll spot and seam welding
When the spot welds on two over lapping pieces of metal are spaced, the process of welding is known as roll spot welding. If the spot welds are sufficiently made close, then the process is called seam welding. This process is best for metal thickness ranging from 0.0.25 to 3 mm.

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