Experiment No :07 Design of simple pneumatic systems used in practice

 

Expt No :07   Design of simple pneumatic systems used in practice

Aim: Design of simple pneumatic systems used in practice

Apparatus:  Automation studio Software 5.7

Theory:

A pneumatic circuit is a group of components such as cpmoressor, actuators, control valves, conductors and fittings arranged to perform useful work. There are three important considerations in designing a hydraulic circuit:

 

1. Safety of machine and personnel in the event of power failures.

2. Performance of given operation with minimum losses.

3. Cost of the component used in the circuit.

 

Problem statement:

A double acting cylinder is used to press together glued components . Upon operation of a press button, the clamping cylinder slowly advances. Once the fully extended position is reached , the cylinder is to remain for a time of t = 6 seconds and then immediately retract to the initial position. A new start cycle is only possible after the cylinder has fully retracted and after a delay of 5 seconds. During this delay the finished part is manually removed and replaced with new parts for gluing. The retracting speed should be fast, but adjustable.

 

Solution :

 

Fig : Pneumatic Circuit for given problem

 

If the push button S1 is actuated for a sufficiently long time period ( t = 5 second) then the air reservoir of time delay valve V1 is filled and corresponding 3/2 valve is switched, following which a signal is applied at input 1 of the dual pressure valve V2.  If the push button S1 is actuated, the AND condition at the dual pressure valve is met. A signal is applied at the control port 12 of the control element V4. The valve V4 switches, pressure is applied to the piston side of the cylinder 1A and the piston rod advances. After as short advancing distances, the limit switch S2 is released, pressure is reduced in the air reservoir of the time delay valve V1 via the roller lever valve S2, and the integrated 3/2 way valve switches back to its initial position. The

AND condition at the dual pressure valve is now no longer met. Actuation of the push button S1 becomes ineffective. Upon reaching the advancing position, the piston rod actuates the roller lever S3. The pressure line to the time delay valve V3 is now released and pressure in the air reservoir is increased. The rate of pressure increase is adjustable via the integrated flow control valve. When the switching pressure has been reached, the integrated 3/2 way valve switches and a signal is applied at the control port 12 of the final control element V4. The valve V4 reverses and the piston rod retracts. Upon release of the limit switch S3, the time delay valve V3 Switches to its initial position again.

 

The limit switch S2 is actuated, when the piston rod reaches its initial position, the pressure in the air reservoir of the time delay V1 starts to increase until the switching pressure has been reached after t = 5 seconds. The integrated 3/2 way valve switches. The initial status of the system is now reached again and a new cycle can be started.   The piston rod speed is set at the restrictors of the one way flow control valves V5 and V6.