24-06-2013, 04:56 PM
AUTOMATIC DOUBLE AXIS WELDING MACHINE
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INTRODUCTION
The technology of pneumatics has gained tremendous importance in the field of workplace rationalization and automation from old-fashioned timber works and coal mines to modern machine shops and space robots. Certain characteristics of compressed air have made this medium quite suitable for used in modern manufacturing and production industries. It is therefore important that technicians and engineers should have a good knowledge of pneumatic system, air operated valves and accessories. A pneumatic system consists of a compressor plant, pipe lines, control valves, drive members and related auxiliary appliances. The air is compressed in an air compressor and from the compressor plant the flow medium is transmitted to the pneumatic cylinder through a well laid pipe line system. To maintain optimum efficiency of pneumatic system, it is of vital importance that pressure drop between generation and consumption of compressed air is kept very low.
In our project “AUTOMATIC DOUBLE AXIS WELDING MACHINE” is beings with an introduction to welding the various components automatically. Three-pneumatic cylinder and solenoid valve are provided. One cylinder is for the up and down movement, another one for arm lifting and one for the rotary motion.
Need For Automation
Automation can be achieved through computers, hydraulics, pneumatics, robotics, etc., of these sources, pneumatics form an attractive medium for low cost automation. The main advantages of all pneumatic systems are economy and simplicity. Automation plays an important role in mass production.
Automation plays a vital role in mass production .for mass production of a product, the machining operations decides the sequence of machining .the machines designed for producing a particular product are called transfer machines.
Needs for pneumatic power
Pneumatic system use pressurized gases to transmit and control power, as the name implies, pneumatic systems typically use air as fluid medium, because air is a safe, low cost and readily available fluid. It is particularly safe environments where an electrical spark could ignite leaks from the system components. There are several reasons for considering the use of pneumatic system instead of hydraulic system. Liquid exhibit greater inertia than gases. Therefore, in hydraulic system the weight of the oil is a potential problem. To design and development a material handling system for automation /semi automation of industries by using pneumatic control system, which is used for low cost automation.
COMPRESSORS
The main function of the air compressor is to compress the air up to the required pressure. The maximum capacity of the compressor is 10105 to 12 105 N/m2. This is a two stages or two-cylinder reciprocating air compressor. The two cylinders are for low and high compression. The air pressure is measured at various places by the use of pressure gauges. V-belt and pulley are used to drive the compressor.
Dynamic compressors
These are rotary continuous machines in which a high speed rotating element accelerates the air and converts the resulting velocity head into pressure.
Positive displacement compressors work on the principle of increasing the pressure of a definite volume in an enclosed chamber. Dynamic (turbo) compressor employs rotating vanes or impellers to impart velocity and pressure to the flow of the air being handled. The pressure comes from the dynamic effects such as centrifugal force.
SOLENOID VALVE
A solenoid is an electrical mechanical device that can convert electrical power to mechanical force and motion. It consists mainly of plunger, mostly a T type plunger, wire or coil and a C-frame. The working principle is such that when an electric current is passed through a coiled wire, a magnetic field sets up around the wire. Because of coiled wire, the magnetic field would be several times stronger around and through its center.
The solenoid force is directly fed to the spool of the direction control valve to shift it. This force is applied through the T-plunger that is surrounded by the coil, also called the armature. To select a proper electromagnet, the forces resisting the actuation of the magnet, i.e. the force of friction and spring force have to be kept at their minimum so that the electromagnet can develop a force greater than the resultant of the resisting force.
Mostly in the case of dc magnets, the body and the armature may be made of one piece whereas the ac magnets require both the parts to be made from thin laminated sheets to obstruct flow of eddy current and to avoid increase of the solenoid body-temperature.
Whether one has to go for a dc or ac magnet, depends fully on the requirement of the control system. However in majority of pneumatic direction control valves, only dc magnets are used as the overall requirement of force and response time is quite suitable for such application.
OPERATION OF SOLENOID VALVE
With solenoid valves, a current through a solenoid is used to implement switching between positions. When a current flows through the solenoid, a magnetic field is produced which pulls the laminated steel core into the coil, the force depending on the current through the solenoid? The larger the current the greater the force exerted.