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1. 1
SUMMER TRAINING & PROJECT REPORT
ON
CNC
&
PLC
DEVELOPED
AT
BHARAT HEAVY ELECTRICALS LIMITED,
JHANSI
UNDER GUIDANCE OF- SUBMITTED BY-
MR. VIJAYVERMA AMANGUPTA
(DPT. MANAGER) B.TECH (E.C.E)
B.H.E.L JHANSI (UP) AMITYUNIVERSITY,
GWALIOR, MADHYA PRADESH

2. 2
ACKNOWLEDGEMENT
I am highly thankful to B.H.E.L. engineers and technical staff for providing us vital and valuable
information about the different facets of an industrial management system.
We express our gratitude to Human Resource and Development department for giving us a chance to feel
industrial environment and its working in B.H.E.L. and we are thankful to Mr. Vijay Verma, Sr. Engineer
for giving his precious time and help us in understanding various theoretical and practical aspect of our
project on PLC under whose kind supervision we accomplished our project. We are also thankful to
Mr. Dhruv Bhargav H.R.D for his kind support.
Aman Gupta
B.TECH (Electronics &
Communication Engineering)

3. 3
PREFACE
At very outset of the prologue it becomes imperative to insist that vocational training is an integral part of
engineering curriculum. Training allows us to gain an insight into the practical aspects of the various topics,
with which we come across while pursuing our B.E. i.e. vocational training gives us practical
implementation of various topics we already have learned and will learn in near future. Vocational training
always emphasizes on logic and commonsense instead of theoretical aspects of subject.
On my part, I pursued 2 weeks training at B.H.E.L. Jhansi. The training involved a study of various
departments of the organization as per the time logically scheduled and well planned given to us. It also
involved a project on PLC under the guidance of Mr. Vijay Verma (Sr. Engineer in W, E & S Department).
The rotation in various departments was necessary in order to get an overall idea about the working of the
organization.
Aman Gupta
B.TECH (Electronics &
Communication Engineering)

4. 4
INDEX
CHAPTER TITLE PAGE NO.-
1-Company profile 5
2-Rotation Report of Industry 12
3-Programmable Logic Controllers (PLCs) 26
4-Computer Numeric Control (CNC) 31
-CNC Constructional details 33
-CNC coordinate systems 36
-Positioning of machine origin 37
-CNC motion control systems 39
-Part programming 48
-Advantages of CNC machine 49
5-Numerical control (NC) and computer numerical
control (CNC) 50
6-Applications 62
7-References 63

5. 5
COMPANY
PROFILE
AN OVERVIEW OF BHEL

6. 6
BHEL is the largest engineering and manufacturing enterprise in India in the energy/ infrastructure sector
today. BHEL was established more than 40 years ago when its first plant was set up in Bhopal in 1956,
ushering in the indigenous Heavy Electrical Equipment Industry in India, a dream that has been more than
realized with a well-recognized track record of performance.
BHEL caters to core sectors of the Indian Economy viz., Power Generation & transmission Industry,
Transportation, Telecommunication, Renewable Energy, Defense, etc. The wide network of BHEL’s 17
manufacturing divisions, 4 power sector regional centers, over 100 project sites, 8 service centers and 18
regional offices, enables the company to promptly serve its customers and provide them with suitable
products, systems and services-efficiently and at competitive prices. BHEL has already attained ISO 9000
certification for quality management, ISO 27000 for Information Technology and ISO 14001 certification
for Environmental Management.

7. 7
VISION, MISSION AND VALUES OF B.H.E.L.
VISION:
“A world class innovative, competitive and profitable engineering enterprise providing total business
solution”. A world class engineering enterprise committed to enhancing stakeholder value.
MISSION:
To be an Indian Multinational Engineering Enterprise providing total business solution through quality
products, system and services in the fields of energy, industry, transportation, infrastructure and other
potential areas.
VALUES:
 Zeal to Excel and Zest for change.
 Integrity and Fairness in all matters.
 Respect of Dignity and potential of individuals.
 Strict adherence to commitments.
 Ensure speed of response.
 Foster learning creativity and teamwork.
 Loyalty and pride in the company.

8. 8
BHEL OBJECTIVE
A dynamic organization is one which keeps its aim high, and adopts itself quickly to changing environment.
So here we are in BHEL.
BUSINESS MISSION
To maintain a leading position as a supplier of quality equipment, system and services in the field of
conversion, transmission, utilization and conservation of energy for applications in the areas of electric
power, transportation, oil and gas exploration industries.
Utilized company is capabilities and resources to expand business into allied areas and other priority sectors
of the economy like defense, communications and electronics.
GROWTH
To ensure a steady growth by enhancing the competitive edge of BHEL in existing new business areas and
international market so as to fulfill national expectation from BHEL.
PROFITABILITY
To provide an adequate return on capital employed, primarily through improvements in operational,
efficiency, capital utilization, productivity and adequate internal resources to finance the company’s growth.
PEOPLE ORIENTATION
To enable each employ to achieve his potential, improve his capabilities, perceive his role and
responsibilities and participate and contribute to the growth and success of the company.
TECHNOLOGY
To achieve technological excellence in operations by developments of indigenous technologies and efficient
absorption and adoption of imparted technologies to suit business and priorities and provide competitive
advantage to the company.
IMAGE
To fill the expectation which state holders like government as owner, employees, customers and the country
at large have from BHEL.

9. 9
VARIOUS BHEL UNITS:
First Generation Units
BHOPAL : Heavy Electrical Plant.
HARIDWAR : Heavy Electrical Equipment Plant.
HYDERABAD : Heavy Electrical Power Equipment Plant.
Second Generation Units
TIRUCHY : High Pressure Boiler Plant.
JHANSI : Transformer and Locomotive Plant.
HARDWAR : Central Foundry and Forge Plant.
TIRUCHY : Seamless Steel Tube Plant.
Unit Through Acquisition and Merger
BANGALORE : Electronics Porcelain Division.
New Manufacturing Units
RANIPAT : Boiler Auxiliaries Plant.
JAGDISHPUR : Insulator Plant.
GOVINDWAL : Industrial Valve Plant.
RUDRAPUR : Component and Fabrication Plant.
BANGALORE : Energy Systems Division.
Repair Shop
BOMBAY : Motor Repair Shop.
VARANASI : Heavy Repair Shop.
BHEL is growing concern to meet the changing needs of the nation has taken it beyond power into the total
gamut of energy, industry and transportation BHEL is able to offer a service in each of this field. Its
manufacturing the capability is supported by a corporate R&D division at Hyderabad works closely with the
research and development cell at various units and Welding Research institute at Tiruchinapalli.

10. 10
BHARAT HEAVY ELECTRICALS LIMITED, JHANSI
By the end of the fifth year plan, it was envisaged by the planning commission that the demand for the
power transformer would raise in the coming years. Anticipating the country’s requirement BHEL decided
to set up a new plant, which would manufacture power and other type of transformer in addition to the
capacity available at BHEL in Bhopal. The Bhopal plant was engaged in the manufacture transformers of
large rating and Jhansi unit would concentrate on power transformer, traction transformer for railway etc.
The unit at Jhansi was established in 9 Jan, 1974 and it is situated around in 15 kms from the city on the
national highway number 26 i.e. Jhansi-Lalitpur road. It is called second generation plant of BHEL it was
setup in 1974 and estimated cost of Rs 16.22crores inclusive of Rs 2.1crores for township. Late Mrs. Indira
Gandhi, the prime minister laid the foundation on 9th Jan 1974. The commercial production of the unit began
in 1976-77 with an output of Rs 53 lacs, since then there has been no looking back for BHEL Jhansi.
Unit of BHEL is basically engaged in the production and manufacturing of transformers of various types and
capacities with growing competition in the transformer section in 1985-88 it undertook the re-powering of
diesel but it took a complete year for the manufacturing to begin. In 1987-89, BHEL has taken a step further
in undertaking it is also, manufacturing AC/DC locomotives.

11. 11
PRODUCT PROFILE OF B.H.E.L. JHANSI UNIT
1. Power Transformer Up to 400 KV class 250 MVA.
2. Special Transformer Up to 180 KV.
3. ESP Transformer 95 KVp, 1400 mA.
4. Freight Loco Transformer 3900 to 5400 KVA & 7475 KVA
(3 Phase).
5. ACEMU Transformer Up to 1000 KVA (1Phase).
1385 KVA (3 Phase).
6. Dry Type Transformer Up to 6300 KVA 33 KV class.
7. Instrument Transformer VT and CT Up to 220 KV class.
8. Diesel Electric Locomotives Up to 2600 HP.
9. AC/DC Locomotives Up to 5000 HP (25 KV AC/1500V DC).
10. Well Wagon 200 Tone.
11. Over Head Equipment cum Test Car
12. Dynamic Track Stabilizer
13. Rail cum Track Stabilizer

12. 12
ROTATION REPORT
OF
INDUSTRY

13. 13
MAIN AIM OF ROTATION
Main aim behind the rotation of various departments is that one can understand the working of each and
every department and to see that how people (workers, middle level executive, top officials) work in
corporate environment.
Main departments of BHEL Jhansi
 Administration
 Production
PRODUCTION UNIT DEPARTMENTS
STORE
There are separate stores for different type of material in the BHEL
There are three sections in store;
 Control Receiving Section
 Custody Section
 Scrap Disposal Section
Functions: - A list of material coming in store is prepared and Quality Control people are called for
inspection. If material is found as par standard SRV (Store Receipt Voucher) is issued for each material. A
total of 08 SVR’s are prepared. Some materials such as Silicon oil, Transformer oil, insulating material etc
are directly stored in the Bays.
Scraps are also sold through unit by a MATERIAL SCRAP TRADING –DELHI.
FABRICATION
Fabrication is nothing but production. It comprises of three bays i.e. Bay 0, Bay 1, Bay 2.
BAY – 0
It is the Preparation shop while the other two bays form the assembly. This section has –
the following machines:
 Planer machine – Two reduce thickness.
 Shearing machine.
 CNC/ANC Flame cutting machine – To cut complicated shaft using Oxy-Acetylene flame.
 Bending machine.
 Rolling machine.
 Flattening machine.
 Drilling machine.
 Nibbling machine.
 Pantograph flame cutting machine.

14. 14
BAY-1
It is an assembly shop where different parts of tank come from bay 0. Here welding processes are used for
assembly, after which a rough surface is obtained Grinder operating at 1200 rpm, is used to eliminate the
roughness.
BAY 2
It is assembly shop dealing with making different object mentioned below:
 Tank assembly
 Tank cover assembly
 End frame assembly.
 Foot assembly.
 Cross feed assembly.
 Core clamp assembly.
 Pin and pad assembly.
Before assembly, short blasting (Firing of small materials i.e. acid picking) is done on different parts of jobs
to clean the surface before painting.
After assembly some tests are known as NON DESTRUCTIVE TESTS:
Ultrasonic Tests: To detect the welding fault on the CRO at the fault place high amplitude waves are
obtained.
Die Penetration Tests: Red solution is put at
the welding & then cleaned. After some time white solution is put. Appearance of a red spot indicates a
fault at the welding.
Magnetic Crack Detection: Magnetic field is created & then iron powder is put at the welding. Sticking of
the iron powder in the welding indicated as a fault.
BAY – 3
Here are basically three sections in the bay:
1. Machine Section.
2. Copper Section.
3. Tooling Section.
MACHINE SECTION : The operations to form small components of Power & Traction Transformers are
done in section. The shop consists of following machines:
CENTRAL LATHE: It consist one tailstock, headstock low part of tailstock is fixed & tailstock spindle is
moving. On this machine facing, turning & threading is done.
TURRET LATHE: Its function is same as central lathe but it is used for mass production. Here turret lathe
is used in presence of tailstock because turret lathe contains many tailstocks.

15. 15
CAPSTAIN LATHE: It is belt drive.
RADIAL ARM DRILLING MACHINE: It is used for drilling & boring.
HORIZONTAL BORING MACHINE : It is computerized and used for making bore, facing etc.
MILLING MACHINE :
a) Horizontal milling machine – It is used for making gear and cutting operations.
b) Vertical milling machine – By this machine facing, cutting & T slot cutting is done
.
COPPER SECTION: All the processes related to copper are done here.
TUBE SLITTING MACHINE: This machine is developed here & is used for cutting the tube along its
length & across its diameter. Its blade thickness is 3 mm.
SHEARING MALCHINE: It is operated hydraulically & its blade has V-shape & a thickness of 15 mm.
DIE AND PUNCHING MACHINE: It is also hydraulically operated & has a die & punch for making
holes.
HYDRAULIC BEINDING MACHINE: It is used for bending job up to 90 degree.
FLY PRESS MACHINE: It is used to press the job. It is operated mechanically by a wheel, which is on the
top of the machine.
BEND SAW MACHINE : This machine is used for cutting job having small thickness. It is circularly
operated blade, around 1.5 m long.
WATER COOLED BRAZING MACHINE: It contain two carbon brushes. The sheet is put along with a
sulfas sheet & the carbon brushes are heated. A lap joint is formed between the sheets as the sulfas sheet
melts.
LINCING BELT MACHINE: It creates a smooth surface.

16. 16
HYDRAULIC PRESS MACHINE: To press the job.
SOLDER POT MALCHINE: It has a pot that contains solder. Solder has a composition of 60% Zn & 40%
Pb.
TOOLING SECTION: In this section the servicing of tools is done.
BLADE SHAPE MACHINE: It sharpens the blade using a circular diamond cutter. Blade of CNC,
cropping line machine is sharpened here.
MINI SURFACE GRINDER MACHINE: It serves grinding purposes. It has a grinding wheel made of
Aluminium Oxide.
TOOL & SURFACE GRINDING MACHINE: This is specially used to grind the tool used in Bay 7.
DRILL GRINDING MACHINE: To grind the drills.
BAY – 4
It is the winding section.
TYPES OF WINDING:
1) Reverse section winding.
2) Helical winding
3) Spiral winding.
4) Interleaved winding.
5) Half Section winding.
There are four TYPES OF COIL fixed in a transformer.
They are:
1) Low voltage coil (LV)
2) High voltage coil (HV)
3) Tertiary coil.
4) Tap coil.

17. 17
The type of winding depends on job requirement also the width and thickness of the conductors are designed
particulars & are decided by design department. Conductors used for winding is in the form of very long
strips wound on a spool, the conductor is covered by cellulose paper for insulation.
For winding first the mould of diameter equal to inner diameter of required coil is made. The specifications
of coils are given in drawing. The diameter of is adjustable as its body is made up of wooden sections that
interlock with each other. Interlocking can be increased or decreased to adjust the inner diameter of coil.
The Moulds are of following types:
1. Belly types.
2. Link types.
3. Cone type
BAY – 5
It is core and punch section. The lamination used in power, dry, ESP transformer etc. for making core is cut
in this section.
CRGO (Cold rolled grain oriented) silicon steel is used for lamination, which is imported in India from
Japan, U.K.Germany. It is available in 0.27 & 0., 28 mm thick sheets, 1 m wide & measured in Kg. The
sheets are coated with very thin layer of insulating material called “carlites”.
For the purpose of cutting & punching the core three machines are installed in shop.
1. SLITING MACHINE : It is used to cut CRGO sheets
In different width. It has a circular cutter whose position can be changed as per the
requirement.
2. CNC CROPPING LINE PNEUMATIC: It contains only
One blade, which can rotate 90 degree about the sheet. It is operated pneumatically.
3. CNC CROPPING LINE HYDRAULIC: It is all so used to cut the CRGO Sheet. It contains
two blades, one is fixed and the other rotates 90 degree above the sheet. It is operated
hydraulically. M4 quality sheet 0.23-0.33 mm thickness is used.
BAY – 6
Single – traction transformer for AC locomotives is assembled in this section. These Freight locomotive
transformers are used where there is frequent change in speed. In this bay core winding & all the assembly
& testing of transformer is done.
These three phase transformer for ACEMU are also manufactured in this section. The supply lines
for this transformer are of 25 KV & power of the transformer is 6500 KVA.
The tap changer of rectifier transformer is also assembled in this bay. Rectified transformer is used in
big furnace like the thermal power stations/plants (TPP).

18. 18
BAY –7
This is the insulation shop. Various types of insulation are:
1) AWWW: All Wood Water Washed press paper.
The paper is 0.2-0.5 mm thick cellulose paper & is wound on the conductors for insulation.
2) PRE-COMPRESSED BOARD: This is widely used for general
insulation & separation of conductors in the forms of block.
3) PRESS BOARD: This is used for separation of coils e.g. L.V.
From H.V. It is up to 38 mm thick.
4) UDEL: UN Dignified Electrical Laminated Wood or Perm wood.
This is special type of plywood made for insulation purposes.
5) FIBER GLASS: This is a resin material & is used in fire prone
areas.
6) BAKELITE
7) GASKET: It is used for protection against leakage.
8) SILICON RUBBER: It is used for dry type transformer.
The machine used for shaping the insulation material are-
1) Cylindrical machines. (2) Circle cutting machine.
3) Punching Press machines (4) Drilling machine.
5) Bench saw (SPL) (6) Jig saw.
7) Circular saw. (8) CNC insulating cutter.

19. 19
BAY – 8
Basically two types of transformers are assembled in this bay:
1) Electrostatic Precipitator (ESP)
2) Instrument Transformer:
a) Current Transformer (CT)
b) Voltage Transformer (VT)
1) ELECTROSTATIC PRECIPITATOR (ESP)
These electrostatic precipitators are used in the thermal power plants remove (precipitate) the
barb on from the smoke coming out from the chimney ESP is of two types.
1) Si oil type.
2) Transformer oil type.
2) INSTRUMENT TRANSFORMER:
In power lines current & voltage handled is very large & therefore dire measurement are not
possible as these current & voltage are for too large for any other of reasonable size & cost. The
solution lies in steeping down the current & voltage with instrument transformers that would be
mattered with instruments of moderate size. The transformers are also used for protective
purpose.
In B.H.E.L. Jhansi transformers from 11 KV class to 220 KV are manufactured.
BAY – 9
In this bay power transformer are assembled. After taking different input from different bays 0-9
assemblies is done.
Power Transformer is used to step & step down voltages at generating & sub-stations. There are various
ratings 11 KV, 22 KV manufactured, they are
a) Generator Transformer
b) System Transformer
c) Auto Transformer

20. 20
A transformer in a process of assemblage is called a job. The design of the transformer is done by the design
department & is unique of each job; depends on the requirement of customer. The design department
provides drawing to the assembly shoP
1) Core Building:- It is made of cold rolled grain oriented steel CRGO. The punch core is sent to this
shop from core punching shop. Here it is assembled with the help of drawing a set of 4 laminations is
called a packet. The vertical portion of a core is called a leg. The horizontal one is caller a yoke.
Packets of both are interlinked. It is undesirable to keep the X section of core circular to provide low
reluctance part with out air space. A perfect cannot be made so the core is steeped to achieve a near
circle. Whatever spaces left are fitted with thin wooden rod. After core building the end is bolted.
The bolts are insulated from the core.
2) Core Lifting:- The core is lifted by a crane & is placed vertical.The rest of assembly is done on the
core in this portion.
3) Unlacing & Core Coil Assembly:- The yoke of this core is removed using crane. Bottom insulation
in form of 50 mm thick UDEL sheets is placed PCB & press board are also used for filling the gap &
to provide a good base for the coil to rest. The coil are then lowered primary, secondary, tertiary &
tap in that sequences.
4) Replacing & End-frame Mounting:- After lowering a coil the top insulation similar to the bottom
one is provided. The removed yoke is placed end-frame bolted back into its position. The
connections are then made as per drawing. All the conductors are insulated using crepe paper.
Brazing copper makes the connections. For brazing sulfas is used.
5) H.V.T.G. & L.V.T.G. :
Terminals gears are accessories provided at high voltage. The upper portion of the OLTC contains
mechanism by which tapping is changed .There is switch which changes tap in very small type
(Microseconds). But there is a possibility of sparking. To get rid of it, OLTC is filled with oil. The
bottom part houses the terminals and the mechanism, which makes automatic connections. The
terminals are made of thick Al strops.
6) Vapour Phasing & Oil Soaking:
It is well known fact that water (impure) is conductor electricity. Therefore, moisture presence in
transformer will affect insulation; the process of moisture removal from transformer is called vapour
phasing. The job is put in dummy tank and place in a vacuum vessel. It is an airtight chamber with
heating facilities. A solvent vessel is released is the chamber which enters all transformer parts and
insulations. It absorbs water rapidly. The job is heated in vacuum. All the solvent vapour is sucked
out with moisture and if not taken care of, may burst the job.
After moisture removal tank is filled with transformer oil & soaked for at least three hours, so that
every gets wet with oil.
The job remains in vessel for three days during phasing. It is then taken out of the vessel & also out
of the dummy tank.
7) Final Servicing & Tanking: After taking the job out of dummy tank all the parts retightened any
other defects are rectified and the job is retimed in mild steel tank. After this the tanking oil is filled.
8) Case Fitting: The accessories are fixed and final touches given the job. The accessories included
tank cover, fixing bushing, fixing valves etc. The terminals are marked and R and D (Rating and
diagram) plate is fixed. Bolting and not riveting because it may require maintenance and opening
close the tank.

21. 21
TRANSFORMER COMMERCIAL
The objective of this department is to interact with the customers. It brings out tenders & notices & also
responds to them. It is department that places the contracts of building the transformers & after delivery
further interacts with the customer regarding faults, this department does failure & maintenance. All such
snags are reported to them & they forward the information to the concerning department.
The works of the commercial department are :
1) Tenders and Notices.
2) Interaction with design department.
TENDERS AND NOTICES:- The department response to the tenders calls of companies/organization,
which requires transformers. Contracts are bagged through also notices. Before inviting tenders it must be
sure that BHEL is ready to undertake the contract and before full knowledge of scope of work is essential.
TRANSFORMER DESIGN
The transformer is designed according to the specifications of the customers i.e.
1. The input/output voltage.
2. The KVA rating.
3. The weight of iron and copper.
The basic design factors are:
1. The amount of copper and iron losses.
2. The rise in temperature of coils.
3. The ambient condition.
The designer has to keep rise between the design factors and selects the optimization of the core yoke
winding etc.
LOCOMOTIVE DEPARTMENT
This unit was started in 1985. This department of Jhansi consists of two sections the first is manufacturing &
other is design. The diesels, AC, AC/DC locomotive are manufactured here.

22. 22
1. THE DIESEL LOCOMOTIVE:
Salient features:
a) Flat bed under frame.
b) All pneumatic valves provides in single panel.
c) All electrical Equipments provided in single panel.
d) Improved filtration system.
e) Brush less traction alternators.
f) Fault display on control desk with alarm.
g) Simple driving procedure.
h) Automatic wheel slip detection & correction.
i) Multiple unit operation up to three locomotives.
j) Air & vacuum brakes.
2. THE AC LOCOMOTIVE:
Salient features:
a) Operate on 25 KV AC Single-phase lines.
b) Driving cab at both ends.
c) Corridors on both sides for maintenance.
d) All pneumatic valves at one place.
e) Automatic wheel slip detection & correction.
f) Multiple unit operation up to three locomotives.
g) Fault display on driver’s desk.
h) VCB in AC circuit.
i) Air & Vacuum brakes.
3. THE AC/DC LOCOMOTIVE
Salient features
a) Designed to operate both in 1500 V DC & 25 KV AC lines.
b) Driving cab at both ends.
c) High adhesion bogie.
d) Corridors on both sides for maintenance.
e) All pneumatic valves at one place.
f) Automatic wheel slip detection & correction.
g) Multiple unit operation up to three locomotives.
h) Fault display on driver’s desk.
i) Static inverter for auxiliary supply.
j) FRP control desk.
k) VCB in AC circuit.
l) Air & Vacuum brakes.
m) Air dryer for brake system.

23. 23
WORK ENGINEERING & SERVICE
As the name suggest this section deals with services & maintenance. It has following sections:
A) Plant equipment: This has electronics & elect/mech. Maintenance.
B) Services: This section deals with air, steam & Power equipments.
C) Telephone Exchange.
D) Township Electrical Maintenance.
E) W.E. & S Planning.
This sections deals with stores & new machines procurement & other general things. There are three
maintenance centers at bay-2, substation 1 & Loco. This section is also responsible for Power distribution in
B.H.E.L.
The power distribution is of two types:
1) HT Power Distribution:- This is at 11 KV, OCB are used for protection. There are four substations for
this distribution.
2) LT Distribution:- This is for the auxiliary in each shop & other section of B.H.E.L. It uses
OCB/OVC/BHEL BHOPAL, 800 KVA 415V Transformer & ACB (English Electro).
TECHNOLOGY
This section mainly deals with continuous modification in the operations to be performed for the completion
of the job. It gets the PSR (Performa of Specification & routine Sheet) from PPC.
This section gives the sequence of operations, time for operations, no. of labors etc., according to the given
standards; it can be modify the above things to obtain best results.
Recently it has modified the operation of crimping in which it advised the use of tungsten carbide thus
reducing the work time to three hours instead of 27 hours with HSS; this also relieved the workers from
maintenance of different dies for different jobs.

24. 24
PROJECT REPORT ON
PROGRAMMAE LOGIC
CONTROLLER
(PLc)

25. 25
PROGRAMMABLE LOGIC CONTROLLERS (PLCs)
A PLC (Programmable Logic Controllers) is an industrial computer used to
monitor inputs, and depending upon their state make decisions based on its program
or logic, to control (turn on/off) its outputs to automate a machine or a process. It can
also be defined as a digitally operating electronic apparatus which uses a
programmable memory for the internal storage of instructions by implementing
specific functions such as logic sequencing, timing, counting, and arithmetic to
control, through digital or analog input/output modules, various types of machines or
processes.
The PLC system:-
A programmable logic controller consists of the following components:
 Central Processing Unit (CPU)
 Memory
 Input modules
 Output modules and
 Power supply.

26. 26
Programming
Terminal
CPU
Output
Module
Memory
Power Supply
Input
Module
A PLC hardware block diagram is shown in Figure. The programming terminal in the
diagram is not a part of the PLC, but it is essential to have a terminal for
programming or monitoring a PLC. In the diagram, the arrows between blocks
indicate the information and power flowing directions.
PLC Hardware Block Diagram
CPU
Like other computerized devices, there is a Central Processing Unit (CPU) in a PLC.
The CPU, which is the “brain” of a PLC, does the following operations:
 Updating inputs and outputs. This function allows a PLC to read the status of
its input terminals and energize or deenergize its output terminals.
 Performing logic and arithmetic operations. A CPU conducts all the
mathematic and logic operations involved in a PLC.
 Communicating with memory. The PLC’s programs and data are stored in
memory. When a PLC is operating, its CPU may read or change the contents
of memory locations.

27. 27
 Scanning application programs. An application program, which is called a
ladder logic program, is a set of instructions written by a PLC programmer.
The scanning function allows the PLC to execute the application program as
specified by the programmer.
 Communicating with a programming terminal. The CPU transfers program
and data between itself and the programming terminal.
A PLC’s CPU is controlled by operating system software. The operating system
software is a group of supervisory programs that are loaded and stored
permanently in the PLC’s memory by the PLC manufacturer.
Memory
Memory is the component that stores information, programs, and data in a PLC. The
process of putting new information into a memory location is called writing. The
process of retrieving information from a memory location is called reading.
The common types of memory used in PLCs are Read Only Memory (ROM) and
Random Access Memory (RAM). A ROM location can be read, but not written. ROM
is used to store programs and data that should not be altered. For example, the PLC’s
operating programs are stored in ROM.
A RAM location can be read or written. This means the information stored in a RAM
location can be retrieved and/or altered. Ladder logic programs are stored in RAM.
When a new ladder logic program is loaded into a PLC’s memory, the old program
that was stored in the same locations is over-written and essentially erased.
The memory capacities of PLCs vary. Memory capacities are often expressed in
terms of kilo-bytes (K). One byte is a group of 8 bits. One bit is a memory location
that may store one binary number that has the value of either 1 or 0. (Binary numbers
are addressed in Module 2). 1K memory means that there are 1024 bytes of RAM.
16K memory means there are 16 x 1024 =16384 bytes of RAM.
Input modules and output modules
A PLC is a control device. It takes information from inputs and makes decisions to
energize or de-energize outputs. The decisions are made based on the statuses of
inputs and outputs and the ladder logic program that is being executed.

28. 28
The input devices used with a PLC include pushbuttons, limit switches, relay
contacts, photo sensors, proximity switches, temperature sensors, and the like. These
input devices can be AC (alternating current) or DC (direct current). The input
voltages can be high or low. The input signals can be digital or analog. Differing
inputs require different input modules. An input module provides an interface
between input devices and a PLC’s CPU, which uses only a low DC voltage. The
input module’s function is to convert the input signals to DC voltages that are
acceptable to the CPU. Standard discrete input modules include 24 V AC, 48 V AC,
120 V AC, 220 V AC, 24 V DC, 48 V DC, 120 V DC, 220 V DC, and transistor-
transistor logic (TTL) level.
The devices controlled by a PLC include relays, alarms, solenoids, fans, lights, and
motor starters. These devices may require different levels of AC or DC voltages.
Since the signals processed in a PLC are low DC voltages, it is the function of the
output module to convert PLC control signals to the voltages required by the
controlled circuits or devices. Standard discrete output modules include 24 V AC, 48
V AC, 120 V AC, 220 V AC, 24 V DC, 48 V DC, 120 V DC, 220 V DC, and TTL
level.
Power Supply
PLCs are powered by standard commercial AC power lines. However, many PLC
components, such as the CPU and memory, utilize 5 volts or another level of DC
powers.
The PLC power supply converts AC power into DC power to support those
components of the PLC

29. 29
PROJECT REPORT ON
computer numerical
control machines (cnc)

30. 30
C.N.C (COMPUTER NUMERIC CONTROL)
Many of the achievement in computer numeric control have a common origin in
numerical control (abbreviated nc). The conceptual framework established during the
development of numerical control is still undergoing further refinement and
enhancement. Modern nc systems rely heavily on computer technology.
Nc (numerical control):-
Numerical control can be defined as a form of programmable automation in which the
process is controlled by numbers, letters, and symbols. Numerical control is the
combination of mechanical, electrical and electronic devices, controlled by numerical
data. In nc, the numbers form a program of instructions designed for a particular work
part or job. When the job changes, the program of instructions is changed. This
capability to change the program for each new job is what gives nc its flexibility. It is
much easier to write new programs than to make major changes in the production
equipment.
Nc technology has been applied to a wide variety of operations, including drafting,
assembly, inspection, sheet metal press working, and spot welding. However
numerical control finds its principal applications in metal machining processes. The
machined work parts are designed in various sizes and shapes, and most machined
parts produced in industry today are made in small to medium-size batches. To
produce each part, a sequence of drilling operations may be required, or a series of
turning or milling operations. The suitability of nc or these kinds of jobs is the reason
for the tremendous growth of numerical control in the metal working industry over
the last 25 years.

31. 31
Constructional details of c.n.c machines
In general, a cnc machine tool consists of the following units:
(i) Computers
(ii) Control system
(iii) Drive motors
(iv) Tool changers
According to the construction of cnc machine tools, it works in the following
(simplified) manner:-
1. The cnc machine controlled by the computer reads the program and translates it into
machine language, which is a programming language of binary notation used on
computers, not on cnc machines.
2. When the operator starts the execution cycle, the computer translates the binary codes
into electronic pulses which are automatically sent to the machine’s power units. The
control unit compares the number of pulses sent and received.
3. When the motor receives each pulse, they automatically transform the pulses into
rotations that drive the spindle and lead screw, causing the spindle to rotate and slide
or move the table. The part on the milling machine table or the tool in the lathe turret
is driven to a position specified by the program.
Computers:-
Cnc machines introduced in the late 1970s were less dependent on hardware and more
dependent on software. These machines store a program into memory when it is first
read in. This facilitates faster operation when producing number of identical parts,
since the program can be recalled from memory repeatedly without having to read it
again. Cnc machines use an on-board computer that allows the operator to read,

32. 32
analyze and edit programmed instruction, while nc machines require operators to
make a new tape to alter a program. In essence, the computer distinguishes cnc from
nc.as with all computers, the cnc machines computer also works on a binary principle
using only two characters, 1 and 0 (machine language) for information processing.
When creating the program, the programmer does not care about the machine
language, instead he or she simply uses a list of codes i.e. g&m codes and keys in
meaningful information. Special built-in software compiles the program into machine
language and the machine moves the tools by servomotors. However, the ability to
program the machine is dependent on whether there is a computer in the machine
control. Modern cnc machines use 32-bit processors in their computers to allow fast
and accurate processing of information. This results in considerable saving of
machining time.
Control system:-
There are two types of control systems on nc/cnc machines. The overall accuracy of
the machine is determined by the type of control loop used.
Open loop:-the open loop control system does not provide positioning feedback to
the control unit. The movement pulses are sent out by the control unit and are
received by a special type of servomotor called a stepper motor. The stepper motor
then proceeds with the next movement command. Since this control system only
counts pulses and cannot identify discrepancies in positioning, the control has no way
of knowing whether the tool has reached the proper location or not. The machine will
continue this inaccuracy until some body finds the error.the open loop control can be
used in applications in which there is no change in load conditions, such as the cnc
drilling machine. The advantage of the open loop control system is that it is less
expensive, since it does not require the additional hardware and electronics needed for
positioning feedback. The disadvantage is the difficulty of detecting positioning error.
Closed loop:-in the closed loop control system, the electronic movement pulses are
sent from the control to the servomotor, enabling the motor to rotate with each pulse.
The pulses are detected and counted by a feedback device called a transducer. With
each step of movement, a transducer sends a signal back to the control, which
compares the current position of the driven axis with the programmed position. When
the number of pulses sent and received match, the control starts sending out pulses for
the next movement. Closed loop systems are very accurate. Most have an automatic
compensation for error, since the feedback device indicates the error and the control

33. 33
makes the necessary adjustments to bring the slide back to its position. They use ac,
dc or hydraulic servomotors.
Drive motors:-the drive motors control the machine slide movement on cnc
equipment.they are classified into four basic types as follows:-
Stepper motor:-these convert a digital pulse, generated by the microcomputer unit
(mcu i.e. machine control unit) into small step rotation. Stepper motors have a certain
number of steps that they can travel. The number of pulses that the mcu sends to the
stepper motor controls the amount of rotation of the motor. Stepper motors are mostly
used in applications where low torque is required. Stepper motors are used in open
loop control system, while ac, dc or hydraulic servomotors are used in closed loop
control systems.
Dc servomotor:- these are variable speed motors that rotate in response to the applied
voltage. They are used to drive a lead screw and gear mechanism. Dc servos provide
high torque output than stepper motors.
Ac servomotor:-these are controlled by varying the voltage frequency to control the
speed. They can develop more power than a dc servo. They are also used to drive a
lead screw and gear mechanism.
Fluid servomotor:-it is also a variable speed motor. They are able to produce more
power or more speed in the case of pneumatic motors than electric servomotors. The
hydraulic pump provides energy to valves which are controlled by the mcu.
Tool changers:-most of the time, different cutting tools are used to produce one part
of a machine. The tools have to be replaced quickly for the next machining
operation. Owing to this reason, the majority of cnc machine tools are equipped with
automatic tool changers, such as magazines on machining centers and turrets on
turning centers fig. They allow tool changing without the intervention of the operator.
Typically an automatic tool changer grips the tool in the spindle, pulls it out, and
replaces it with another tool.on most machines with automatic tool changers, the
turret or magazine can rotate in either forward or reverse direction. Tool changers
may be equipped for either random or sequential tool selection. In random tool
selection, there is no specific pattern of tool selection on the machining centre, when
the program calls for the tool, it isautomatically indexed into waiting position, where

34. 34
it can be retrieved by the tool handling device. On the turning centre, the turret
automatically rotates, bringing tools into position.
In sequential tool selection, the tools must be loaded in the exact order in which they
are called for in the program (fig.). Even if the tools are not in the correct order, the
next tool is automatically selected, whether it is suitable or not for the next machining
operation. When it is necessary to use a tool twice, the operator must load another tool
with the same purpose. The advantage of sequential tool selection is that less time is
needed for indexing the tool into the waiting position. The disadvantage is that more
time is needed for setup when switching to a job with a different order of tools. This
means that although the same tools are to be used, they have to be preloaded
(rearranged) because of a different order in the program. This eliminates the time
advantage of sequential tool selection, making random tool selection a standard
feature on today’s cnc machine tools.
Cnc coordinate systems
1. for milling:-
In order for the part programmer to plan the sequence of positions and movements of
the cutting tool relative to the work piece, it is necessary to establish a standard axis
system by which the relative positions can be specified. However, to make things
easier for the programmer, we adopt the view point that the work piece is stationary
while the drill bit is moved relative to table. Accordingly, the coordinate system of
axes is established with respect to the machine table. Two axes, x and y, are defined
in the plane of the table, as shown in figure. The z axis is perpendicular to this plane
and movement in the z direction is controlled by the vertical motion of the
spindle. The positive and negative directions of motion of tool relative to table along
these axes are as shown in figure. Cnc drill presses are classified as either two- axes

35. 35
or three- axes machines, depending on whether or not they have the capability to
control the z axis.
A numerical control milling machine and similar machine tools (boring mill, for
example) use an axis system similar to that of the drill press. However, in addition to
the three linear axes, these machines may possess the capacity to control one or more
rotational axes. Three rotational axis axes are defined in cnc: the, b, and c axis. These
axes specify angle about the x, y, and z axes, respectively. To distinguish positive
from negative angular motions, the “right-hand rule” can be used. Using the right
hand with the thumb pointing in the positive linear axis direction (x, y, or z), the
fingers of the hand is curled to point in the positive rotational direction.
2. For turning:-
For turning operations, two axes are normally all that are required to command the
movement of the tool relative to the rotating work piece. The z axis is the axis of
rotation of the work part, and x axis defines the radial location of the cutting
tool. This arrangement is illustrated in figure.the purpose of the coordinate system is
to provide a means of locating the tool in relation to the work piece. Depending on the
cnc machine, the part programmer may have several different options available for
specifying this location.
Positioning of machine origin
Fixed zero:- the programmer must determine the position of the tool relative to the
origin (zero point) of the coordinate system. Cnc machines have either of two

36. 36
methods for specifying the zero point. The first possibility is for the machine to have
a fixed zero. In this case, the origin is always located at the some position on the
machine table. Usually, that position is the southwest corner (lower left-hand corner)
of the table and all tool locations will be defined by positive x and y coordinates.
Floating zero:-the second and more common feature on modern cnc machines
allows the machine operator to set the zero point at any position on the machine
table. This feature is called floating zero.the part programmer is the one who decides
where the zero point should be located. The decision is based on part programming
convenience. For example, the work part may be symmetrical and the zero point
should be established at the center of symmetry. The location of the zero point is
communicated to the machine operator. At the beginning of the job, the operator
moves the tool under manual control to some “target point” on the table. The target
point is some convenient place on the work piece or table for the operator to position
the tool. For example, it might be a predrilled hole in the work piece. The target point
has been referenced to the zero point by the part programmer. In fact, the programmer
may have selected the target point as the zero point for tool positioning. When the
tool has been positioned at the target point, the machine operator presses a “zero”
button on the machine tool console, which tells the machine where the origin is located for subsequent
tool movements.
Mode of positioning
Absolute positioning:-

37. 37
Another option sometimes available to the part programmer is to use either an
absolute system of tool positioning or an incremental system. Absolute positioning
means that the tool locations are always defined in relation to the zero point. If a hole
is to be drilled at a spot that is 8 in. Above the x axis and 6 in. To the right of the y
axis, the coordinate location of the hole would be specified as x=+6.000 and
y=.+8.000.
Incremental positioning :-
Positioning means that the next tool location must be defined with reference to the
previous tool location must be defined with reference to the previous tool location. If
in our drilling example, suppose that the previous hole had been drilled at an absolute
position of x=+4.000 and y=+5.000. Accordingly, the incremental position
instructions would be specified as x=+2.000 and y=+3.000 in order to move the drill
to the desired spot.figure illustrates the difference between absolute and incremental
positioning.
CNC motion control systems
In order to accomplish the machining process, the cutting tool and work piece must be
moved relative to each other. In cnc, there are three basic types of motion control
systems:-

38. 38
1. Point- to- point cnc:-point-to-point (ptp) is also sometimes called a positioning
system. In ptp, the objective of the machine tool control system is to move the cutting
tool to a predefined location. The speed or path by which this movement is
accomplished is not important in point-to-point cnc.
Once the tool reaches the desired location, the machining operation is performed at
that position. Cnc drill presses are a good example of ptp systems. The spindle must
first be positioned at a particular location on the work piece. This is done under ptp
control.then the drilling of the hole is performed at the location, and so forth. Since no
cutting is performed between holes, there is no need for controlling the relative
motion of the tool and work piece between whole locations. Figure illustrates the
point-to-point type of control.
2. Straight-cut cnc:- straight-cut control systems are capable of moving the
cutting tool parallel to one of the major axes at a controlled rate suitable for
machining. It is therefore appropriate for performing milling operations to fabricate
work pieces of rectangular configurations. With this type of cnc system it is not
possible to combine movements in more than a single axis direction. Therefore,
angular cuts on the work piece would not be possible. An example of a straight-cut
operation is shown in figure. A cnc machine capable of straight cut movements is also
capable of ptp movements.
3. Contouring cnc: - contouring is the most complex, the most flexible, and the
most expensive type of machine tool control. It is capable of performing both ptp and
straight-cut operations. In addition, the distinguishing feature of contouring cnc
systems is their capacity for simultaneous control of more than one axis movement of
the machine tool. The path of the cutter is continuously controlled to generate the
desired geometry of the work piece. For this reason, contouring systems are also
called continuous-path cnc systems. Straight or plane surfaces at any orientation,
circular paths, conical shapes, or most any other mathematically definable form are
possible under contouring control. Figure illustrates the versatility of continuous path
cnc. Milling and turning operations are common examples of the use of contouring
control.
G CODES
CODE FUNCTION
G00 POINT TO POINT POSITIONING MODE OF CONTROL(RAPID
TRANSVERSE)

39. 39
G01 LINEAR INTERPOLATION MODE OF CONTROL(LINEAR
TRANSVERSE)
G02 CIRCULAR INTERPOLATION ARC CLOCKWISE(NORMAL
DIMENSION)
G03 CIRCULAR INTERPOLATION ARC COUNTER CLOCKWISE(USED
FOR NORMAL DIMENSION)
G04 DWELL-A PREDETERMINED TIME DELAY BEFORE EXECUTING
(CURRENT BLOCK INSTRUCTIONS.)
G05 HOLD-AN INFINITE DELAY BEFORE EXECUTING CURRENT
BLOCK INSTRUCTIONS TERMINATED ONLY BY OPERATOR OR
INTERLOCK SWITCH.
G06 UNASSIGNED-MAY ACQUIRE STANDARD USE.
G07 AVOID ACCELERATION
G08 REACCELERATION
G09 LINEAR INTERPOLATION USED FOR LONG DIMENSIONS
G10 LINEAR INTERPOLATION USED FOR SHORT DIMENSION
G11 3-D-INTERPOLATION
G12 TO
16
AXIS SELECTION
G17 XY PLANE SELECTION
G18 ZX PLANE SELECTION
G19 YZ PLANE SELECTION
G20 CIRCULAR INTERPOLATION ARC CW(INCHES MODE)(USED FOR
LONG DIMENSIONS)
G21 CIRCULAR INTERPOLATION ARC CW FOR (MM) MODE (USED FOR
SHORT DIMENSIONS)
G22 COUPLED MOTION-
G23 COUPLED MOTION-
G24 UNSIGNED
G25 START OF SUB ROUTINE
G26 END OF SUB ROUTINE
G27 TO
29
UNASSIGNED
G30 RESERVED FOR CONTOURING CCW(LONG DISTANCE)
G31 RESERVED FOR CONTOURING CCW (SHORT DISTANCE)
G32 UNASSIGNED
G33 THREAD CUTTING (CONSTANT LEAD)
G34 THREAD CUTTING (INCREASING LEAD)
G35 THREAD CUTTING (DECREASING LEAD)
G36 USED FOR CONTROL PURPOSE ONLY
G37 CALLING OF SUBROUTINE
G38
G39 PERMANENTLY UNASSIGNED
G40 CUTTER COMPENSATION (CANCEL)

40. 40
G41 CUTTER COMPENSATION (LEFT)
G42 CUTTER COMPENSATION (RIGHT)
G43 CUTTER COMPENSATION (POSITIVE)
G44 CUTTER COMPENSATION (NEGATIVE)
G45 TO
51
UNASSIGNED
G52 UNASSIGNED AND RESERVED FOR ADAPTIVE CONTROL
G53 LINEAR SHIFT CAN EL
G54 LINEAR SHIFT (X)
G55 LINEAR SHIFT(Y)
G56 LINEAR SHIFT(Z)
G57 LINEAR SHIFT(XY)
G58 LINEAR SHIFT(XZ)
G59 LINEAR SHIFT(YZ)
G60 TO
61
UNASSIGNED
G62 POSITIONING FAST
G63 TAPPING
G64 CHANGE OF RATE
G65 CASSETTE LOAD
G66 CASSETTE SAVE
G67 CASSETTE SEARCH
G68 TO
69
UNASSIGNED
G70 INCH PROGRAMMING ON CNC TOOLS WHICH ACCEPT
DIMENSIONS IN INCHES AS WELL AS MILLIMETERS
G71 METRIC PROGRAMMING
G72 TO
77
UNASSIGNED
G78 MILL CYCLE
G79 MILL CYCLE
G80 FIXED CYCLE CANCEL
G81 REPEAT FUNCTION-FIXED TURNING CYCLE/DRILLING CYCLE.
G82 CIRCULAR CYCLE/DRILL DWELL
G83 DRILLING CYCLE
G84 RECTANGULAR CYCLES(THREADING CYCLE)
G85 TO
89
UNASSIGNED
G90 ABSOLUTE DIMENSION PROGRAMMING
G91 INCREMENTAL DIMENSION PROGRAMMING
G92 POSITION PRESET
G93 UNASSIGNED
G94 FEET RATE IN MM/MIN(INCHES/MM)

41. 41
G95 FEET RATE IN MM/REV(INCHES/REV)
G96 CONSTANT SURFACE SPEED (MM/MIN)
G97 SPEED (REV/MIN)
G98 SPEED (REV/MIN)
G99 FLOATING DATUM
M CODES
M00 PROGRAM STOP
M01 OPTIONAL (PLANNED) STOP
M02 END OF PROGRAM
M03 SPINDLE START IN CLOCKWISE DIRECTION.
M04 SPINDLE START IN ACW DIRECTION.
M05 SPINDLE STOP
M06 TOOL CHANGE
M07 COOLANT ON (TYPE 2-FLUID COOLING)
M08 COOLANT ON (TYPE 1-MIST COOLING)
M09 COOLANT OFF
M10 CLAMP
M11 UNCLAMP
M12 UNASSIGNED
M13 CW SPINDLE START-COOLANT ON
M14 ACW SPINDLE START + COOLANT ON
M15 MOTION + VE
M16 MOTION – VE
M17 UNASSIGNED
M18
M19 ORIENTED SPINDLE STOP
M20 AUXILIARIES.
M21 INPUT
M22
TO 29
UNASSIGNED
M30 END OF TAP, SIMILAR TO M02 EXCEPT THAT IT MUST INCLUDE
REWINDING OF TAPE TO END OF RECORD, THUS READY FOR NEXT
WORK PIECE.
M31 INTERLOCK BY-PASS
M32
TO 35 CONSTANT CUTTING SPEED (USED WITH TURNING)
M36 FEED RANGE 1
M37 FEED RANGE 2
M38 SPINDLE SPEED RANGE 1
M39 SPINDLE SPEED RANGE 2

42. 42
M40
TO 47
GEAR CHANGE
M48 CANCEL M49
M49 BYPASS OVERRIDE
M50 COOLANT NO.3 ON
M51 COOLANT NO.4 ON
M52
TO 54
UNASSIGNED
M55 LINEAR TOOL SHIFT POSITION 1
M56 LINEAR TOOL SHIFT POSITION 2
M57
TO 59
UNASSIGNED
M60 WORK PIECE CHANGE
M61 LINEAR WORK PIECE SHIFT POSITION 1
M62 LINEAR WORK PIECE SHIFT POSITION 2
M63
TO 67
UNASSIGNED
M68 CLAMP WORK PIECE
M69 UNCLAMP WORK PIECE
M70 UNASSIGNED
M71 ANGULAR WORK PIECE SHIFT POSITION 1
M72 ANGULAR WORK PIECE SHIFT POSITION 2
M73
TO 77
UNASSIGNED
M78 CLAMP SLIDE
M79 UNCLAMP SLIDE
M80
TO 89
UNASSIGNED
STOCK DEFINATION

43. 43
l - Stock length
d1 - cylinder diameter
d2 - hole diameter
z - Origin z
The stock reference point (origin) is the center of the right face. Origin z indicates the
z position of the program origin relative to the stock origin.
If the stock has more complicated shape than cylinder it may be defined by sequence
of g-code lines prefixed with the character your cnc controller uses for a comment
line. This sequence must be placed between stock/begin and stock/end commands.
TOOL DEFINITIONS.
Standard od tool:
TOOL/STANDARD, BA, A, R, IC, ITP
Standard id tool has the same definition (back angle instruct cut viewer to the
orientation of the tool):
Note: the ic (inside circle) is the diameter for which the tool insert geometry is created
about. The IC is an industry standard term used by all insert manufactures. The itp
(imaginary tool point) is the intersection of the vertical and horizontal edges of the
tool and this point often is used for tool path programming.

44. 44
the itp is a value indicating the tip position of the imaginary tool point with respect to
the tool nose radius center point as illustrated below.
It p=0 if the tool nose radius center point is used for tool path programming.
Grooving od tool:
Tool/groove, r1, r2, l, w, a1, a2, oa, itp
Oa=90
Grooving id tool:
Tool/groove, r1, r2, l, w, a1, a2, oa, itp
Oa=270

45. 45
For face tool oa=0
Note: to change control point (left or right tool corner) simply changes sign of w
value.
Threading od tool:
tool/thread, a, l, w, oa
Drill:
Tool/drill, d, a, l

46. 46
PART PROGRAMMING
the programmer carefully converts the sequence of operations to a set of instructions,
i.e., (part program). Part programming consists of sequence of blocks. each block has
a specific function to perform. Machine read one block & commands the tool or other
slides to perform that operation. After this controller shifts to the next block. in this
way complete machining is performed which consists of small step operation define
by each block. let us take example of some blocks.
Format: g02 x__ z__ i__ k__ f__( i, k format)
Or g02 x__ z__ r__ f__
Here in first syntax,
i = distance between start point & center point of arc along x-axis.
k= distance between start point & center point of arc along z-axis.
& in second syntax
r = radius of the arc.
The g02 command is utilized to move the tool in the circular arc profile. with g02 the
movement will be in the clockwise direction. the movement taken will be at the
programmed feed rate.
Manual part program:-
the program contains g and m codes. g codes are called preparatory codes. they
prepare the machine for cutting operation e.g. linear interpolation, circular
interpolation, rapid etc. m codes are called miscellaneous codes.they perform all other
operation except for cutting like spindle on/off, coolant on/off, tools changing etc.the
manual part program looks like the following statement.
n10 g90 g00 x + 100 y – 100 z + 50; (single block)
Programming tips
programming is just like any other work- with good knowledge and appositive
attitude; it can be done right and with first class results. here are some tips to get the
best
result from any programming effort.

47. 47
1. Approach cnc programming in a logical and methodological way.
2. always calculate unknown values – never guess.
3. Standardize a programming style and adhere to it.
4. program dimensional values in absolute mode whenever possible.
5. make a setup sheet and/or tooling sheet before programming, not after.
6. Program as many machining operations in a single setup as possible.
7. Use minimum numbers of tools for maximum number of jobs- standardize.
8. always program for the safety of cnc machining.
9. document your work and store everything relating to the program development.
10. watch for programming errors- syntax and logical- all errors are avoidable.
Advantages of CNC machine
Most of the advantages derived from cnc technology are due to the high level of
automation, high flexibility of cnc machines and their ability to combine
multifunction machining requirements in minimum number of workstations and
setups.
The significant advantages are as follows:
High accuracy and repeatability:
reduced inspection:
 ease of assembly and interchangeability.
 less scrap and rework
 Reduction in floor space/number of men/handling, results in better management
control over the production.
 Development of new work is done faster with the usage of cnc machines.
 saving in jigs and fixtures as well as in dead time;
 less material handling.
 Cost accounting and production control becomes very precise.
 Dependence on skilled operators can be dispensed with.
 Optimum utilization of horse power of the machine.
 increase effective machine utilization:
 reduced usage of tools.
 less paper work.

48. 48
NUMERICAL CONTROL (NC) AND COMPUTER
NUMERICAL CONTROL (CNC)
Numerical control refers to the operation of machine tools from numerical data. Data
for the operations may be stored on paper tape, magnetic tape, magnetic disks, etc.
because numerical information is used, the concept is called numerical control.
Numerical control is the operation of machine tools and other processing machines by
a series of coded instructions. with a built-in computer controlling the machine tool
functions and the system is known as computer numerical control (cnc).
A typical numerical control machine tool system contains three basic
components:
1. A program, that is, a set of instructions
2. A machine control unit (mcu)
3. The machine tool.
figure shows these three basic components.
Fig-1-basic components of nc machine in the nc system, all the information which is
required for producing a component, viz. dimensional information. Speed, feed, and
cutting speed is stored in the coded form as a part program.
the mcu is further divided into two elements: the data processing unit (dpu) and

49. 49
control loops unit (clu). the dpu processes the coded data read from the tape or other
storage media and passes information on (i) the position of each axis, (ii) required
direction of motion, (iii) speed, feed, and (iv) auxiliary function control signals to clu.
For example, a typical part program may contain an instruction
x + 100, y + 50, s + 90
this instruction is interpreted as: to move by a distance of 100 mm in the x-positive
direction, 50 mm in the y-positive direction and rotate the spindle at 90 rpm
clockwise. these information pieces are decoded by the dpu and sent to clu.
the clu operates the drive mechanisms of the machine to move the table in x and y
directions, and to rotate the spindle as specified. then it receives feedback signals
concerning the actual position and velocity of each of the axes, and signals for
completion of the operation. when execution of one line (instruction) as noted by the
clu is complete, another instruction is read. a data processing unit consists of some or
all of the following parts:
• Data input device such as a paper tape reader, magnetic tape reader, etc.
• Data reading circuits and parity checking logic
• decoding circuits for distributing data among the controlled axes
• An interpolator, which supplies machine-motion commands between data points
for tool motion.
• A control loops unit, on the other hand, consists of the following:
• Position control loops for all the axes of motion, where each axis has a separate
control loop
• Velocity control loops, where feedback control is required
• Deceleration and backlash take up circuits
• Auxiliary functions control, such as coolant on/off, gear changes, spindle on/off
control.
Geometric and kinematics data are fed from the dpu to the clu. the clu then governs
the physical system based on the data received from the dpu.
Processing equipment is the third basic component of the nc system.
it is the machine tool that performs the useful work. the machine tool is designed or
modified to be controlled, operated, and interfaced with the control loop unit (clu).

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Advantages of NC system
NC systems offer several advantages over the conventional manufacturing methods.
These are:
1. High machine utilization
2. Need for special tooling is mostly eliminated
3. High quality products can be manufactured
4. Consistency in quality
5. Quality is not dependent on the operator's skill
6. Lesser production cost per unit
7. Reduced scrap
8. Reduced in-process inventory
9. Higher productivity
10. Reduced set-up time.
Disadvantages of NC system
1. Very high initial investment on specialized equipment
2. Redundancy of labour
3. Downtime of NC is highly expensive
4. Special skill is required for programming and operating equipment.
Comparison between CONVENTIONAL MACHINES and
NC MACHINES
1. The NC machine differs from a conventional machine in many ways. Different
aspects of the two are
compared here.
2. New NC machines cost around two to five times more than the similar capacity
conventional machines,
depending upon the sophistication of the control system and the size of the
machine.
3. Conventional machines require a high order of skill and trained personnel to
operate to produce complex
Contours.
4. The machine hour rate is generally higher for the NC machines or the down time
of these machines is
Very costly.
5. Maintenance of NC machine is costlier than the conventional machine.
6. The production rate of NC machines is higher than that of the conventional
machines and they can
produce complicated profiles consistently with good accuracy.

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7. NC machines require special tooling. Because, these machines are designed to
operate at the very high
Operating conditions (today, NC machines are capable of operating at 50,000 rpm)
Tools made from
Carbon tool steel and HSS cannot be used at such a high speed.
8. Use of automatic tool changers to change the tool automatically and simultaneous
machining by multiple
tools are the features available with high-end NC machines. These features help to reduce down
time set-up time.
Coordinate systems and Program Zero Point
To describe the geometry of a workpiece for NC programming, we use coordinate systems with X-, Y- and Z-axes.
The origin of the frame and the alignment of the axes are chosen in such a way that any point on the workpiece can
be defined by naming its X, Y and Z coordinate values. A coordinate frame attached to the corner of a prism is
shown in Fig.2. The directions of X, Y, Z axes illustrated in Fig. 2 are treated as the positive directions and the
movement of the tool in the opposite direction is treated as negative.
Lathe coordinate system
Milling machine coordinate system

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the point of intersection of the three axes (the origin) is called zero point. A point at a
distance 60 mm from the zero point in positive X direction and 30 mm in positive Y
direction is denoted as:
X + 60, Y + 30
And a point 10 mm below the top surface at the above location is denoted as:
X + 60, Y + 30, Z - 10
It is also possible that we can locate the origin of another coordinate frame anywhere
in the work piece. This new origin of frame is called program zero point. All
coordinate values in the program may be referred relative to the program zero point.
The different locations of program zero point are illustrated in Fig. 3

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With a program zero point at the lower left corner of a workpiece, the coordinate
values of X + 50, Y + 60, Z + 30, for example, would mean that the tool is required to
move to a point located 50 mm away from the program zero point in positive X
direction, 60 mm away in positive Y direction and 30 mm away in positive Z
direction. This is shown in Fig.4
DEFINING THE COORDINATE SYSTEM FOR A TANGENT
POINT P
Classification of Numerical Control Machines.
Numerical control machines can be generally classified using the following
categories:
1. Type of motion
2. Programming method
3. Control system.
Type of motion
According to the type of motion, NC machines can be classified as:
1. Point-to-point systems
2. Contouring or continuous systems.

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Point-to-point systems.
In case of point-to-point (PTP) motion machine tool, the cutting tool moves to a
numerically defined location, the motion is stopped and the task is performed. After
completing the task, the tool moves to the next point and the cycle is repeated. In a
PTP system, the path of movement of the tool and its velocity, when the tool moves
from one point to another, is of no significance.
Contouring or continuous systems. The tool has to move in a predetermined path in the case of contouring or
continuous systems. For example, consider the component ABCD, as shown in Fig. 5
(b), to be cut from the material. To manufacture this component, the tool has to move
in a predefined contour (path) A-B-C-D. The intermediate points of the contour are
obtained by interpolator, which is contained in DPU of the processing systems. That
is, while moving from A to B (or B to A) in Fig. 5 (b) we just need to input the
coordinates of points A and B, then define whether these points A and B are joined by
a straight line or an arc then interpolator automatically calculates all the intermediate
points between A and B and accordingly gives the signal such that the tool is moved
in the respective path
Programming method
According to programming method used, NC system can be classified into two
categories as:
1. Absolute positioning
2. Incremental positioning (or Chain positioning).
Absolute Positioning.
In absolute positioning, the coordinates of the target point are defined with respect to
a fixed program zero point. Absolute dimensions tell the control to what point the tool
is to move, regardless of its current position. Figure 6 shows absolute positioning for
point B, irrespective of whether the tool was at A or at C. It can be observed from Fig.
6 that all the values are based on the program zero point. The positional command for
the tool to reach point B would be X + 70, Y + 30

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Incremental positioning.
Incremental or chain positioning tells the control by what amount the tool is to move
from its present position. The present position of the tool acts as the program zero
point. Chain positioning for point B from point A and from point C are shown in Figs.
7 and 7(b), respectively.
Each coordinate value is based on the end point of the previous location. The
positional command for the tool to reach B from A would be X + 50, Y + 20 and to
reach B from C would be X + 30, Y - 10

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Control System
According to the typeof controlsystems used, NC systems can be classified as:
1. Open loop system
2. Closed loop system.
Every control system, including NC systems may be designed as open loop or closed loop control.
Open loop system:
The term open loop means that there is no feedback, and the action of the controller
has no information about the effect of the signal that it produces. Figure 8 shows an
open loop control for a single axis of motion.
Since there is no feedback information, the system accuracy is solely a function of the
motor's ability to pass through the exact number of steps, which is provided at its
input.

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Closedloop system:
In a closed loop control system, the actual position and the velocity of the axis are
measured with sensors. The schematic diagram of the closed loop system is shown in
Fig. 9. Assuming a digital control system, a digital to analogue convertor (DAC) is
included in Fig. 9
CLOSED LOOP CONTROL SYSTEM
The difference between actual and the programmed value is termed as the- error. The
control system is designed in such a way so as to eliminate the error or reduce it to a
minimum.
Advantages of CNC Systems over Conventional NC Systems
 Because the computer can be readily and easily reprogrammed, therefore, the system
is very flexible. The machine can manufacture a part followed by other parts of
different designs.

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 More versatility. Editing and debugging programs, reprogramming and plotting and
printing part shapes are simpler
 Program to manufacture a component can be easily called. This saves time and
eliminates errors Due to tape readin
 Greater accuracy.
What is CNC wood router?
A CNC wood router is a Numerical control tool that creates objects from wood. Parts
of a object can be made and then assembled using a router to produce a complete
object.
The CNC router works like a printer. Work is composed on a computer and then the
design or drawing is sent to the CNC router for the hard copy. This outputs a 3-
dimensional copy of the work. The CNC router uses a cutting tool instead of an ink
jet. The cutting tool is generally a router but other cutters can be used as well.
A CNC wood router uses CNC (computer numerical control) and is similar to a metal
CNC mill with the following differences:
• The wood router typically spins faster — with a range of 13,000 to 24,000 RPM
• Low end hobby grade machines typically uses smaller tools — typical shank size 20
mm or at most 25 mm. Professional quality machines frequently use surface facing
tools up to 3" in diameter or more, and spindle power exceeding 15 horsepower.

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Machines capable of routing heavy material at many hundreds of inches per minute
are common.
• Some machines use smaller tool holders MK2 (Morse taper #2 - on older machines),
ISO-30, HSK-63 or the tools just get held in a collet tool holder affixed directly to the
spindle nose. ISO-30 and HSK-63 are rapid-change tool holding systems. HSK-63 has
begun to supplant the ISO-30 as the rapid change standard in recent years.
A wood router is controlled in the same way as a metal mill, but there is a lot of CAM
and CAD software like Art cam, Mastercam, Bobcad, and Featurecam specifically for
wood routers.
Wood with different grain must be approached with unique strategies, and wood
CAM software is less likely to need to have hog-out strategies than the metal ones.
Wood routers are frequently used to machine other soft materials such as plastics at
high speed.
Typical three-axis CNC wood routers are generally much bigger than their metal shop
counterparts. 5' x 5', 4' x 8', and 5' x 10' are typical bed sizes for wood routers. But can
be built to accommodate very large sizes up to, but not limited to 12' x 100'. Most
table routers use a three motor drive system (xyz) utilizing either servo or stepper
motors that drive the router motor via a gantry system. The gantry system isolates the
XYZ movement in the top part of the machine with a stationary table holding the
work piece. Many CNC metal mills have the cutter motor moving on the Z axis, and a
table which moves in X and Y for added stability.
Many wood routers can run at machining speeds of 25 metres/min (linear) or faster
with a few machines such as the Anderson capable of 40 metres/min, Onsrud capable
of 86 metres/min.
Separate heads
Some wood routers have multiple separate heads that can come down simultaneously
or not. This design is generally not as easy as a toolchanger with ISO-30 or HSK-63,
though it is easier to maintain. Some routers have multiple heads that can run
complete separate programs on separate table all while being controlled by the same
interface.
Dust collection
The wood router typically has 6"-10" air ducts to suck up the wood chips/dust created.
They can be piped to a stand-alone or full shop dust collection system.
Some wood routers are specialized for cabinetry and have many drills that can be
programmed to come down separately or together. The drills are generally spaced 32
mm apart on centres - a spacing system called 32 mm System. This is for the proper
spacing of shelving for cabinets. Drilling can be vertical or horizontal (in the Y or X
axis from either side/end of the workpiece) which allows a panel to be drilled on all
four edges as well as the top surface. Many of these machines with large drilling
arrays are derived from CNC point-to-point borers.

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APPLICATIONS
CABINETS - Making cabinet components on a CNC router has become a common
practice today. The technology of manufacturing cabinet boxes, doors, drawer fronts,
shelves and even countertops with a robotic tool is now well within the reach of
smaller shops. Using CNC technology, cabinetmakers are now able to increase
production throughput, while minimizing material handling.
WOODWORKING - In addition to high-volume furniture and millwork companies,
novice and master craftsmen alike are embracing CNC technology in their workshops.
SIGNS – CNC Wood routers are used in signmaking to carve images in wood and
foam, to cut plastic and aluminum letters, and to intricately machine the all sorts of
graphic objects and letters. Full 3D cutting capabilities allow cutting and machining
of practically anything.
BOATS - Boatbuilding is a natural for utilizing the benefits of CNC technology, In
boatbuilding, CNC Wood routers are used for cutting frames, plywood panels and all
manner of interior and exterior parts. They are used in wood, fiberglass and aluminum
production processes.
INSTRUMENTS - Luthiers of all disciplines can now supplement their traditional
woodworking tools with CNC routers. While the CNC may not duplicate all of the
specialized processes involved in instrument making, it brings new capabilities that
can transform an ordinary shop to an extraordinary one.

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REFERENCES
1. www.wikipedia.org/wiki/Main
2. www.bhel.com/home.php
3. Electrical and electronic Instrumentation by A.K. Shawney.
4. http://www.yourpersonalplctutorsite.htm
5. http://www.pc-control.co.uk/index.htm.
6. http://www.plcmanualbasicguidetoplc.htm
7. http://www.plcs.net
8.http://www.sea.siemens.com/step/templates/lesson.mason?plcs:1:1:1
9. Version 2 EE IIT Kharagpur.