1.0 TITLETRANSFER STATION (AUTOMATION LAB)
2.0 PROBLEM STATEMENTUsing a transfer station, blocks are to be
transferred from a magazine to a processing station. The blocks are
pushed out of the magazine by cylinder 1A and transferred to the
processing station by cylinder 2A. The piston rod of cylinder 2A
may only return when the piston rod of cylinder 1A has reached the
retracted end position. The magazine is monitored by means of a
limit switch. If there are no more blocks in the magazine, it is
not possible to start the cycle. The control is to be operated
continuously and can be stopped at any time. Include any other
performance enhancement of the automation system.
Figure 2.1 : Positional sketch of the transfer station
3.0 OBJECTIVESThe objective of the experiment was listed below :
i. To design and realize coordinated sequential motion control with
auxiliary conditionsii. To enhance the performance of the transfer
station with students creativity
4.0 INTRODUCTION (BACKGROUND & THEORY)
On an automation system one can find three families of
components, which are sensors valves and actuators. An adequate
technique is needed to project the logic circuit to integrate all
the necessary components and execute the sequence of movements
properly. For a simple direct sequence of movement an intuitive
method can be used, but for indirect or more complex sequence the
intuition can generate a very complicated circuit and signal
mistakes. It is necessary than to use another method that can save
time of the project, make a clean circuit, can eliminate occasional
signal overlapping and redundant circuits.
The electro-pneumatic system can be defined as a control system
for pipe organs. The air pressure, controlled by an electric
current and operated by the keys of an organ console, opens and
closes valves within wind chests, allowing the pipes to speak. This
system also allows the console to be physically detached from the
organ itself. The only connection was via an electrical cable from
the console to the relay, with some early organ consoles utilizing
a separate wind supply to operate combination pistons.
An electric circuit is completed when the organ key is
depressed, by means of a switch connected to that key. This causes
a low-voltage current to flow through a cable to the windchest,
upon which a rank or multiple ranks of pipes are set. Within the
chest, a small electro-magnet associated with the key that is
pressed becomes energized. This causes a very small valve to open.
This, in turn, allows wind pressure to activate a bellows or
"pneumatic" which operates a larger valve. This valve causes a
change of air pressure within a channel that leads to all pipes of
that note. A separate "stop action" system is used to control the
admittance of air or "wind" into the pipes of the rank or ranks
selected by the organist's selection of stops, while other ranks
are "stopped" from playing. The stop action can also be an
electro-pneumatic action, or may be another type of action.One of
the advantages of the electro-pneumatic system is the console of an
organ which uses either type of electric action is connected to the
other mechanisms by an electrical cable. This makes it possible for
the console to be placed in any desirable location. It also permits
the console to be movable, or to be installed on a "lift", as was
the practice with theater organs. For the disadvantage, the
electro-pneumatic system used the large quantities of thin
perishable leather, usually lambskin and sometimes requires an
extensive "re-leathering" of the windchests every twenty-five to
forty years depending upon the quality of the material used, the
atmospheric conditions and the use of the organ.
Figure 4.1: The example of electro-pneumatic system
5.0 METHOD OF APPROACH
1. The displacement-step diagram was design.2. The pneumatic and
electric circuit diagram was design3. The pneumatic and electric
circuit construction has been carry out4. The sequential motion
control system was implemented and realized5. Check and trouble
shoot the sequence of the circuit.6. The report is prepared based
on this case study.
6.0 APPARATUS
Component ListDescriptionQuantity
Double Acting Cylinder2
5/2-way double solenoid pilot valve2
Limit Switch4
24 DC power supply1
7.0 EXPERIMENTAL PROCEDURE
1. The electro-pneumatic circuit was set up in the required
sequence.
2. Once the circuit has been set up, the push button is pressed
to turn on the system.
3. The first limit switch is pressed. The limit is used as a
sensor to sense the block that needs to be moved.
4. Once the limit switch is pressed, the sequences of cylinders
were observed.
Figure 7.1 : Cylinder 1A extends first
Figure 7.2 : Cylinder 2A extends after cylinder 1A is fully
extended and cylinder 1A begin to retract once cylinder 2A is fully
extended.
Figure 7.3 : Cylinder 2A starts to retract when cylinder 1A is
fully retracted
5. The cycle repeats every time the sensor detects the
block.
8.0 RESULT AND DATA ANALYSIS
9.0 DISCUSSION OF RESULTS
Check the Sequence of the CircuitAs been mentioned before, the
design displacement-step of the circuit is:-
Sequence of operation pneumatic circuit :1. Cylinder A is
extended (A+), while cylinder B is retracted in position.2. When
cylinder A is fully extended, then the cylinder B is started to
extend (B+). Note that the cylinder A is still in that position.3.
When the cylinder B is fully extend, then the cylinder A is
starting retracted. It should note that the cylinder B is still in
fully extending position.4. When cylinder A is fully retracted the
cylinder B then started to retract. This operation is continuous
until the transfer block or component is completely, or stop button
is pressed.5. Therefore the sequence of this circuit is 1A+, 2A+,
1A-, 2B-.An electro-pneumatics circuit above was design to operate
the mechanism of two double acting cylinders where the operation is
applied at the transfer station of the conveyer system where the
double acting cylinder A is extended to push the magazines from the
slot to the left. Then, the double acting cylinder B will extend
and push the magazines into the box. The detail sequence as follow
:1. When main supply switched on, air is supplied to the
directional control valve. If main supply switch is deactivated
then the air supply to the system is switched off.2. When limit
switch (L1) is in detected by block of magazines it will activate
the 5/2-way double solenoid pilot valve. 5/2- way double solenoid
pilot valve is control the air for the cylinder A to extend.3.
After the cylinder A is fully extended, block of magazine will
touch the limit switch (L2) and it will active the 5/2- way double
solenoid pilot. The 5/2- way double solenoid pilot will control air
at double acting cylinder B to extend fully. It should not that
double acting cylinder A still extend fully.4. Once the cylinder B
is fully extended, block will touch the limit switch (L3) in which
it will activate the 5/2- way double solenoid pilot and it will
control the air for the cylinder A retracted. 5. When cylinder A
fully retracted, it will touch the limit switch (L4). Then the
cylinder B will retract fully in the transfer station.
Limit switch (L1) detect other block and the operation or cycle
will be continuous until limit switch (L1) not detect any block
From the steps, it is related to the problem that has been given
which blocks need to be transferred to one station to another
station by using pneumatic system. The steps are needed to satisfy
the given problem so that no problems occur during the system being
operated. More creative design could be implemented in order to
have different kind of sequence but still fulfill the
objectives.
Trouble Shoot of the Circuit
The control of pneumatic cylinders could be affected by manual,
mechanical, pneumatic and electrically actuated valves. Electrical
energy has certain specific advantages over all other forms of
control energy. However, electrical controls in pneumatic system
should not be used where there exists the possibility of hazards
due to fire-borne accidents which may be caused by electrical
sparks. In comparison to other types of mechanical systems,
pneumatic systems are found to be less problematic. However,
industrial experience shows that even best of system sometimes
fails and hence need to take necessary care in order to keep the
system runs at the optimum efficiency. A systematic procedure for
finding and eliminating faults reduces the downtime of pneumatic
systems. Faults are generally occurs by external failures of
machine components and internal failures within control system.
Typical problems are seal wear, internal leakage and valve seal
wear.
In order to have a good and efficient pneumatic system, students
should: Understand the circuit function and component symbols of
the total system including the construction Understand the
port-numbering system valves Analysis the circuit problems
Troubleshoot from bottom to top of the circuit
Component with good and well planned preventive maintenance
programmed, pneumatic components are expected to last quite a long
period of time without any unexpected and untoward failure.
10.0 CONCLUSION
The electro pneumatic system is successfully designed and the
coordinate sequential motion with auxiliary conditions is realized.
A new idea for the performance of the transfer station is get from
the understanding the basic pneumatic system and some basic about
programming controller of the circuits.
The programming of the controller does not use PLC languages,
but a configuration that is simple and intuitive. With
electro-pneumatic system, the programming follows the same
technique that was used before to design the system, but here the
designer works directly with the states or steps of the system.
With a very simple machine language the designer can define all the
configuration of the step using four or five bytes. It depends only
on his experience to use all the resources of the controller.
The controller task is not to work in the same way as a
commercial PLC but the purpose of it is to be an example of a
versatile controller that is design for an specific area. Because
of that, it is not possible to say which one works better; the
system made with microcontroller is an alternative that works in a
simple way.
11.0 RECOMMENDATION
i. Emergency stop buttonEmergency stop (E-Stop) buttons are an
important safety component of many electrical circuits, especially
those that control hazardous equipment such as gas pumps, moving
machinery, saws, mills, and cutting tools, conveyor belts, and many
other types of equipment. They are designed to allow an operator or
bystander to stop the equipment in a hurry should anything go
wrong.
ii. RelayA relay is a simple electromechanical switch made up of
anelectromagnet and a set of contacts. Relays are found hidden in
all sorts of devices. In fact, some of the first computers ever
built used relays to implementBoolean gates. For example, in this
case study, relay can be used to act as a switch to control the
flow of blocks. When the sensor detected the block was empty, the
relay will switch off the circuit to saving electricity.
iii. CounterIndigital logicandcomputing, acounteris a device
which stores (and sometimes displays) the number of times a
particulareventorprocesshas occurred, often in relationship to a
clock signal. In practice, there are two types of counters : Up
counters, which increase (increment) in value Down counters, which
decrease (decrement) in value
For example, in this case study, we recommend that the circuit
used a counter in order to count the total number of blocks
transfer or used in a cycle.
iv. BuzzerAbuzzerorbeeperis anaudiosignaling device, which may
bemechanical, electro-mechanical, orelectronic. Typical uses of
buzzers and beepers includealarms,timersand confirmation of user
input such as a mouse click or keystroke. For example, in this case
study, we also recommended to use a buzzer in order to detect the
problem that occurs in the system/circuit.
v. Timer Atimeris a specialized type ofclock. A timer can be
used to control the sequence of an event or process. Whereas
astopwatchcounts upwards from zero for measuring elapsed time,
atimercounts down from a specified time interval, like anhourglass.
Timers can be mechanical,electromechanical,electronic(quartz), or
evensoftwareas all modern include digital timers of one kind or
another. When the set period expires some timers simply indicate so
(e.g., by an audible signal), while others operate electrical
switches.
12.0 REFERENCE
i. Amit M. Rampure, Pneumatic Training Report, Mumbaiii. S. R.
Majumdar, 1996, Pneumatic Systems: Principles and Maintenance, Tata
McGraw-Hilliii. J. widera, G. Wszoeka, W. Carvalhob, Programmable
controller designed for electro-pneumatic systems, Silesian
University of Technology, Department of Mechanical Engineering, May
2005