International Journal of Electrical, Electronics and Computer Systems (IJEECS)
_______________________________________________________________________________________________
Machine control using Programmable Logic Controller (PLC)
1
Nidhi Ponnamma M.A, 2E. Elavarasi
M.Tech, IV Semester, DEC, Asst. Professor
Dept. of ECE, AMCEC
Email: 1nidhi9253@gmail.com, 2elu_ye@yahoo.co.in
Abstract: PLC and ladder logic are the workhorses of
factory automation. Earlier automated systems used
hundreds or thousands of electromechanical relays; which
used to consume lot of time in wiring. A single PLC can be
programmed as an efficient replacement. This paper
speaks of programming the PLC and designing HMI
screens used in the design & development of an induction
hardening machine. Induction hardening is a form of heat
treatment in which a metal part is heated by induction
heating and then quenched. PLC is a digitally operating
electronic apparatus which uses a programmable memory
for the internal storage of instructions for implementing
specific functions, such as logic, sequencing, timing,
counting and arithmetic, to control various types of
machines or process through digital or analog
input/output. HMI is the part of the machine that handles
the Human-machine interaction. This helps in
communicating with the machine. HMI screen is also
referred as the operator interface terminal, it allows to:
view faults, operate machine and control manual functions.
Keywords: PLC, Ladder logic, Simatic Manager,
Induction hardening, Quenching, Quenchant, WinCC
Flexible Advance and HMI.
II. INDUCTION HARDENING
Heat treatment is usually carried out to provide metal
with desirable properties. Induction hardening is a
thermal hardening process in which the material is
austenitized through inductive heating followed by
quenching, which causes the austenitized volume to
transform to martensite. It is an energy effective method;
only the volume to be hardened is heated. This method
provides the desired hardness profile at a reasonable
cost. Hardening is carried out to improve the final
properties of the metal such as, tensile strength, fatigue
strength, elasticity and wear resistance.
Quenching is the rapid cooling of a work piece to obtain
certain material properties. It must be rapid enough to
transform austenite to matensite. Commonly used water
based polymer quenchants are: Polyalkylene Glycols
(PAG) and acrylates (PA).
III. DESCRIPTION OF CPU “315-2 PN/DP”
I. INTRODUCTION TO PLC
Programmable Logic Controller (PLC) is a specialized
industrial computers used for controlling and operating
the manufacturing process and machinery. It uses a
programmable memory to store instructions and execute
functions including on/off control, timing, counting,
sequencing, arithmetic, and data handling. The PLC
accepts inputs from switches and sensors, evaluates
them based on a program (logic), and changes the state
of outputs to control a machine or process.
Programmable Logic Controllers (PLC’s) are used in
every aspect of industry to expand and enhance
production. Where older automated systems would use
hundreds or thousands of electromechanical relays, a
single PLC can be programmed as an efficient
replacement. Programming is carried out using
“LADDER LOGIC”.
Fig.1. PG to PLC interface
_______________________________________________________________________________________________
ISSN (Online): 2347-2820, Volume -2, Issue-3, 2014
32
International Journal of Electrical, Electronics and Computer Systems (IJEECS)
_______________________________________________________________________________________________
1.
2.
Status and Error display:
C.
It is used to display internal CPU fault or fault in
module.
It is used to remove heat from liquid via a vaporcompression or absorption refrigeration cycle. This
liquid can then be circulated through a heat exchanger to
cool air or equipment as required.
Bay for Simatic Micro card:
It is the slot provided for a memory card.
Programs are saved in memory card.
3.
Source
Power source used is CAMI 100kw, with low frequency.
Mode selector:
It allows us to select the mode of PLC; Run mode
or Stop mode.
4.
D.
Chiller unit
Industrial Ethernet twisted pair cable for
connecting to additional PROFINET devices:
E.
Control unit
CPU, S7 315-2 PN/DP is present on the control unit.
Programs are downloaded onto the CPU, S7 315-2
PN/DP using MPI.
It is used to interface PLC and Human Machine
Interface.
5.
Industrial Ethernet twisted pair
interconnecting PN interface X2:
cable
for
It is used to interface PLC and computer/PG.
6.
Programming device (PG) with STEP 7 software:
It is referred to the computer/laptop in which the
software is installed. Step 7 or Simatic Manager is
the software used for programming.
7.
Mounting rail:
It is used to mount the CPU/ PLC.
8.
Power supply ON/OFF:
It is used to indicate the supply given to the PLC.
IV. HARDENING MACHINE OPERATION
Below figure.2 represents the block diagram of
hardening machine. It consists of Chiller unit 1 and 2,
Control panel, Air blower, Quench water, Quench tank,
Power source, Loading conveyor, Unloading conveyor
and heating station.
A.
Heating station
Component/ Parts are heated at the heating station. In
this station metal is heated to hardening temperature
(austenitizing).
B.
Cooling station or Quench water
Component/ Parts are cooled using continuously
showering quench water. It is carried out to transform
austenite to martensite.
Hardening is followed by quenching in a suitable
quenchant.
Quenching should be fast enough, but not so fast that it
causes problems such as cracking or unnecessary
distortion.
The most used quenchant is a polymer solution in water
and the next most used is pure water.
The heating zone can be quenched in different ways, but
the spray quenching method is the most common.
Fig.2. Block diagram of Hardening machine
The overall system operation is controlled using PLC
and the programming is carried out using ladder.
This machine is used for hardening different sized
component/part/work piece. Component size selection
and power percentage selection is made on “Human
Machine Interface” (HMI).
Hardening machine consists of 14 meters long conveyor.
Left side of the machine is referred as loading conveyor
and the right side is referred as unloading conveyor.
Seven proximity sensors are placed on the conveyor.
Each sensor performs different functions.
First sensor senses, when the component is loaded to the
conveyor (loading side). When second sensor is high,
the component is heated; Pyrometer is used to monitor
component temperature, and programming is done in
such a way that the pyrometer value is read on the HMI
screen. Air blower starts when third sensor gets
activated. If third and fourth sensors are low, then
blower should be switched OFF. When proximity
sensor 5 gets enabled unload the component at
unloading side. Last two sensors are used to indicate
conveyor chain cut (both loading and unloading). These
functions are digitally operated using PLC. PLC used is
S7300 with CPU “315-2PN/DP”.
Three modes of operation are: Manual mode, Semi Auto
mode and Auto mode.
_______________________________________________________________________________________________
ISSN (Online): 2347-2820, Volume -2, Issue-3, 2014
33
International Journal of Electrical, Electronics and Computer Systems (IJEECS)
_______________________________________________________________________________________________
a)
Manual mode: Entire machine operations (from
loading the component till unloading) are controlled
manually.
b)
Semi Auto mode: Loading and unloading the
component it done manually, remaining operation is
carried out automatically.
c)
Auto mode: Entire machine operation is
carried out automatically. Components are loaded with
the help of lifter unit and singling unit. Lifter unit is
used to lift the work piece, where as singling unit is used
to select single component from group of components.
V. ALGORITHM
Step1: Cycle start
Step 2: Turn on the pumps.
Step 3: Check for Pre- Condition. If the condition
doesn’t satisfy, then go to Step 2.
Step 4: Press cycle start button.
Step 5: Check for Alarms. If there are any active alarms,
then go to Step 20.
Step 6: Start loading and unloading conveyor motor.
Step 7: Check whether the work piece/part is present at
loading side.
Step 8: Check whether the work piece is present at
heating point.
Step 9: Switch ON the heat.
Step 10: Check whether PS2 and PS 3 is low.
Step 11: Switch OFF the heat.
Step 12: Wait till PS 3 becomes high.
Step 13: Switch ON the Air blower.
Step 14: Wait till PS 4 becomes low.
Step 15: Switch OFF the Air blower.
Step 16: Part/ work piece is cooled at Quench station.
Step 17: Wait till PS 5 becomes high.
Step 18: Unload the part/work piece.
Step 19: Check if Emergency/Cycle stop/Reset button is
pressed. If yes, then go to step 20.
If no, then repeat the steps from step 7.
Step 20: Stop.
VI. FLOW CHART
Figure 3 shows the flow chart of machine operation.
Fig.3. Flow chart
VII. SIMATIC MANAGER
Figure.4 represents the elements present on the “Simatic
Manager” window. Simatic Manager is the tool used to
carry out PLC programming.
Programmable Logic Controller (PLC) is a specialized
industrial computers used for controlling and operating
the manufacturing process and machinery.
It uses a programmable memory to store instructions and
execute functions including turning ON/OFF the control,
timing, counting, sequencing, arithmetic, and data
handling. The PLC accepts inputs from switches and
sensors, evaluates them based on a program (logic), and
changes the state of outputs to control a machine or
process.
Programmable Logic Controllers (PLC’s) are used in
every aspect of industry to expand and enhance
production.
_______________________________________________________________________________________________
ISSN (Online): 2347-2820, Volume -2, Issue-3, 2014
34
International Journal of Electrical, Electronics and Computer Systems (IJEECS)
_______________________________________________________________________________________________
IX. COMMUNICATION BETWEEN
HARDWARE AND SOFTWARE (PLC AND
PC/PG):
Editor
Window
Using the STEP 7 software, S7 program can be created
within a project. The S7 programmable controller
consists of a power supply unit, a CPU, and input and
output modules (I/O modules).
MPI is used to communicate between PC and PLC.
Through this, the Ladder logic or the programs from
PC/PG is downloaded to PLC.
Fig.4. PLC editor Window
Programs are written on the editor window. On
completing the programming part, the programs are
compiled ( ), and then the programs are downloaded
to the PLC. To download the program, click on
download button
run mode (
. And then the program can be put to
).
VIII. WINCC FLEXIBLE ADVANCE
Figure.5 represents the elements present on the “WinCC
Flexible Advance” window. WinCC Flexible Advance is
the tool used to carry out HMI screens designing.
HMI is the part of the machine that handles the Humanmachine interaction. This helps us to communicate with
the machine. Using HMI, we can perform necessary
operations like controlling and monitoring the machine
operations.
HMI screen are also referred as the operator interface
terminal, it allows to: view faults, operate machine and
control manual functions.
In some machines, the viewing screen is touching
sensitive. On other machines, a separate keyboard and
mouse is used to select and input the data.
Fig.6. Communication between PC and PLC
X. COMMUNICATION BETWEEN PLC
AND HMI:
MPI network is used to communicate between the
Programmable Logic Controller (PLC) and the Human
Machine Interface (HMI)
Fig.7. Communication between PLC and HMI
XI. CONCLUSION
Fig.5. HMI screen editor Window
PLC is very versatile and effective tool in industrial
automation. It cuts the production costs and increases
the quality. Load to load time taken is 90 seconds.
Troubleshooting is easy in PLC. Wiring is complicated
when electromechanical relays are used, where as wiring
_______________________________________________________________________________________________
ISSN (Online): 2347-2820, Volume -2, Issue-3, 2014
35
International Journal of Electrical, Electronics and Computer Systems (IJEECS)
_______________________________________________________________________________________________
is easy when PLC’s are used. Hence it is reliable to
operate/ control a machine using PLC.
Transactions on, On page(s): 5422 - 5435
Volume: 60, Issue: 12, Dec. 2013
[6]
Saracin, C.G.; Saracin, M.; Zdrentu, D.
"Experimental study platform of the automatic
transfer switch used to power supplies backup", Advanced Topics in Electrical Engineering
(ATEE), 2013 8th International Symposium
on, On page(s): 1 – 6
[7]
Ashour, Hamdy "Automatic transfer switch
(ATS) using programmable logic controller
(PLC)", Mechatronics,
2004.
ICM
'04.
Proceedings of the IEEE International
Conference on, on page(s): 531 – 535
[8]
Hoge, D.J.; Jensen, J.R. "A comparison of
protocol conversion methods for the retrofit of
SCADA systems", Petroleum and Chemical
Industry Conference, 1988, Record of
Conference Papers., Industrial Applications
Society 35th Annual, On page(s): 245 - 248
REFERENCES
[1]
R. Filer and L. George Programmable Controllers
and Designing Sequential Logic, 1992: Saunders
College Pub.
[2]
L.A. Bryan and E.A. Bryan Programmable
Controllers: Theory and Implementation, 1988:
Industrial Text.
[3]
C. D. Simpson Programmable Logic Controllers,
1994: Regents/Prentice-Hall.
[4]
W. G. Ian Programmable Controllers: Operation
and Application, 1988: Prentice-Hall
[5]
Bing Tian; Chengxiong Mao; Jiming Lu; Dan
Wang; Yu He; Yuping Duan; Jun Qiu "400
V/1000 kVA Hybrid Automatic Transfer
Switch", Industrial
Electronics,
IEEE

_______________________________________________________________________________________________
ISSN (Online): 2347-2820, Volume -2, Issue-3, 2014
36