INTRODUCTION TO NFC:

The Nuclear Fuel Complex (NFC) is the backbone of the Indian

nuclear power program. Established in the year 1971, it is the major industrial unit of

Department of Atomic Energy, Government of India. The complex is responsible for the

supply of nuclear fuel bundles and reactor core components for all the nuclear power

reactors operating in India. It is a unique facility where natural and enriched uranium

fuel, zirconium alloy cladding and reactor core components are manufactured under one

roof starting from the raw materials.

The Nuclear Fuel Complex is unique in many respects. It is the

only Complex of its kind where Uranium concentrates on the one hand and Zirconium

mineral on the other are processed at the same location all the way to produce finished

fuel assemblies and also zirconium alloy tubular components, for supplies to the Nuclear

Power Industry. The complex also symbolizes the strong emphasis on self-reliance in the

Indian Nuclear Power Program. The advanced technologies for the production of nuclear

grade uranium di-oxide fuel, zirconium metal and zirconium alloy tube components and

the manufacture of fuel bundles conforming to reactor specifications were developed

through systematic efforts during the late 50's and the 60's.

The common plant facilities comprising of the Quality Control

Laboratory, the Central Workshop, the Compressor and Boiler House, the Civil, Electrical

and Mechanical Engineering Services render strong support to the Plant operations.

While the individual plant capacities were designed to match the

requirements of the Indian Nuclear Power Program as projected in the early '70s the

capacities have been under continuous review. With the experience gained in the

operation of various production plants, process and equipment modifications have been

incorporated to progressively improve plant performance. The stage has now been

reached for substantial increase in capacities and plans have been drawn up for

1

establishing new plants to cater to the requirements of fuel and zircaloy for the 6,000

Mwe Indian Nuclear Power Program to be implemented in this decade.

WHY NUCLEAR ENERGY IS REQUIRED?

It is not just the threat of climate change which makes a U-turn in

energy policies an urgent requirement. A fundamental reorientation is indispensable also

because worldwide energy resources in terms of fossil fuels such as coal, gas and oil are of

course limited. Independent studies have shown that on the basis of current rates of

output, global oil reserves would last around 40 years, natural gas reserves c. 65 years,

and coal deposits some 200 years. Non-renewable energy sources, do, as their name

suggests, run out.

Apart from their impact on global warming, they are finite.

Rapid industrial growth and increased use of electrically operated

domestic appliances have increased the demand for electrical energy all over the globe.

India is not an exception to that. Consumption of electricity has been increasing in India at

the rate of around 10% per annum. Thermal power plants depending on running out coal

reserves and hydroelectric power plants with complicated setups and scarce water

resources need alternative energy sources.

Originally it was because it was seen as more convenient and

probably cheaper than fossil fuel alternatives such as coal, gas and oil. That was when

the technology was first developed for harnessing the power of the atom in a safe and

controlled manner, in the 1950s. Since then the question of sustainability has emerged,

giving rise to a more sophisticated rationale.

Nuclear energy has distinct environmental advantages over fossil fuels, in that virtually

all its wastes are contained and managed - nuclear power stations do not cause any

pollution. The fuel for nuclear power is virtually unlimited, considering both geological

and technological aspects. That is to say, there is plenty of uranium in the earth's crust

and furthermore, well-proven (but not yet fully economic) technology means that we

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can extract about 60 times as much energy from it as we do today. The safety record of

nuclear energy is better than for any major industrial technology.

The sun and stars are seemingly inexhaustible sources of energy.

That energy is the result of nuclear reactions, in which matter is converted to energy. We

have been able to harness that mechanism and regularly use it to generate power.

Presently, nuclear energy provides for approximately 16% of the world's electricity.

Unlike the stars, the nuclear reactors that we have today work on the principle of nuclear

fission.1 gram of 92U235 on complete fission can give energy equivalent to 2.5 tons of coal.

It is renewable, non-polluting and is being considered increasingly important in present

days.

MAIN PROCESSES IN NFC:

India is pursuing an indigenous three stage Nuclear Power Program involving

closed fuel cycles of Pressurized Heavy Water Reactors (PHWRs) and Liquid Metal cooled

Fast Breeder Reactors (LMFBRs) for judicious utilization of the relatively limited reserves

of uranium and vast resources of thorium .The zircaloy clad enriched uranium oxide fuel

elements and assemblies for these reactors are fabricated at NFC starting from imported

enriched uranium hexafluoride.

Uranium Refining:

The raw material for the fuel is Magnesium Di-uranate (MDU) popularly known as 'Yellow

Cake'. The MDU concentrate is obtained from the uranium mine and milled at Jaduguda

and Jharkhand. The impure MDU is subjected to many refining processes and sinterable

uranium dioxide powder is formed which is then compacted in the form of cylindrical

pellets and sintered at high temperature to get high density uranium dioxide pellets.

Zircaloy Production:

The source mineral for the production of zirconium metal is zircon (zirconium silicate)

available in the beach sand deposits of Kerala, Tamil Nadu and Orissa. Zircon sand is

processed to get homogeneous zircaloy ingots which are then converted into seamless

tubes, sheets and bars by extrusion, Pilgering and finishing operations.

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Fuel Fabrication

For PHWR fuel, the cylindrical UO2 pellets are stacked and encapsulated in thin walled

tubes of zirconium alloy, both ends of which are sealed by resistance welding using

zircaloy end plugs. A number of such fuel pins are assembled to form a fuel bundle that

can be conveniently loaded into the reactor. The fuel bundles for PHWR 220 Mwe and

PHWR 500 Mwe consist of 19 and 37 fuel pins respectively

Seamless Tubes, FBR Sub-assemblies and Special Materials:

The Stainless Steel Tubes Plant and Special Tubes Plant at NFC produce a wide variety of

stainless steel and titanium seamless tubes for both nuclear and non nuclear applications.

NFC is supplying sub-assemblies and all stainless steel hardware including tubes, bars,

sheets and springs for the operating FBTR and the forthcoming PFBR. The Special

Materials Plant at NFC manufactures high value, low volume, high purity Special Materials

like tantalum, niobium, gallium, indium etc., for applications in electronics, aerospace and

defense sectors.

DIFFERENT PLANTS AT NFC:

The complex includes various separate plants for different processes to be done .They

include:

1. The Zirconium Oxide Plant: For processing of Zircon to pure Zirconium oxide;

2. The Zirconium Sponge Plant: For conversion of Zirconium oxide to pure sponge metal;

3. The Zircaloy Fabrication Plant: For producing various zirconium alloy tubings and also

sheet, rod and wire products;

4. The Uranium Oxide Plant: For processing crude uranium concentrate to pure uranium

di-oxide powder;

5. The Ceramic Fuel Fabrication Plant: For producing sintered Uranium oxide pellets and

assembling of the fuel bundles for the PHWRs;

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6. The Enriched Uranium Oxide Plant: For processing of imported enriched uranium

hexafluoride to enriched uranium oxide powder;

7. The Enriched Uranium Fuel Fabrication Plant: For producing enriched UO2 pellets and

the fuel assemblies for the BWR reactors;

8. A plant for fabrication of components and sub assemblies for Fast Breeder Reactors

9. A Special Materials Plant for producing a number of electronic grade high purity

materials for supplies to the Electronic Industry;

10. Facilities for reclamation of Zircaloy mill-scrap;

11. Plants producing stainless steel seamless and other special tubes have also been set

up in this complex

A notable feature at the Nuclear Fuel Complex is that, apart from in-house

process development, a lot of encouragement is given to the Indian industry for

fabrication of plant equipments and automated systems. Major sophisticated equipments

fabricated in-house at NFC include the slurry extraction system for purification of

uranium, high temperature (1750 deg C) pellet sintering furnace, vacuum annealing

furnace, cold reducing mill, split spacer and bearing pad welding machines, automatic

tube cleaning station, etc. In addition to this, several services like vacuum arc melted

alloys production, seamless tube extrusion and finishing, production of tools, NDT

services, etc., are undertaken.

CENTRALIZED TOOL ROOM:

The Centralized Tool Room of NFC caters to the tooling

requirements of practically all the plants in NFC. In addition, the Tool Room carries out

special job orders for other sister units of DAE and the Defense Laboratories, including

NPCIL, BARC, IGCAR, CAT and DMRL. The Tool room manufactures tooling for the

horizontal and vertical extrusion presses, dies and mandrels for HPT and VMR Pilger mills

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and dies and plungers for the powder compaction presses of the fuel plants. The Tool

Room also takes up several special jobs, some of which are listed below:

1. Import substitution products like silver gaskets for steam generators.

2. Pot hole dies for aluminum tube extrusion

3. Tube spinning mandrels

4. Titanium sponge compacting dies

5.Components for PFBR blanket and control rod assemblies such as control

rod head, conical connecting piece, control rod seating piece, handling head, sheath body,

guide-cum-labyrinth, coolant entry tube and discriminator, coolant passage tube, support

sleeve, foot upper part etc in stainless steel meeting strict dimensional tolerances.

6. Defect standard notches for Ultrasonic and Eddy current testing of tubes,

rods and sheets.

The main activities of tool room are to fabricate, machine and heat treat the

various components. The fabrication is done on various conventional lathes and CNC

machines. Unique machinery like the Becker lathes, CNC’s and S-PILOTE present in the

tool room help in finest machining of the components

Heat treatment is done to impart hardness and toughness to the

material. Hardening is the process of heating the components to recrystallisation

temperature, maintaining them at that temperature for certain time and then cooling back

to room temperature through various quenching processes. There are many furnaces of

various capacities – 12KW, 200KW, 2KW, 40KW, 8KW and convection tempering furnace

-120KW present in the heat treatment section of tool room to meet the requirements.

Processes like hardening, carbo-hardening, tempering are done. The carbo-hardening

process is a process uniquely invented and done at NFC which provides double hardness

when compared to normal hardening process. Thus the tool room caters the total tool

requirements of NFC.

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DIFFERENT MACHINES IN TOOL ROOM:

1. Furnaces: 12KW, 200KW, 40KW, 8KW capacities

2. Air conditioners

3. Band saw –Horizontal

4 .Centre Lathe - LZ-3009, NH-22, NH-26

5. CNC Lathe

6. CNC Lathe –Cylindrical grinding machine HMT make GIC-20

7. CNC Lathe – SB-CNC-30

8 .Conventional tempering furnace 120KW

9. Copying lathe- S-PILOTE

10. Cylinder grinder –G17, G22, K-130

11. Die groove cutting machine –Becker lathe – KB-47, KB-65

12. GAG-Press

13. Heavy duty Lathe – L-45, L-50

14. Honing machine K-13

15. Miscellaneous

16. Mono rail electric hoist -2T

17. Motor vehicle

18. Pedestal grinder

19. Pillar drilling machine

20. Profile projector

21. Radial drilling machine

22. Rotary surface grinds

23. Shaping machine

24. Single grinder EOT Crane -5Tons capacity

25. Surface grinders

26. Tool and cutter grinders

27. Universal grinders

28. Universal milling machine

29. Universal boring machine

30. Welding generator.

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COMPUTER NUMERIC CONTROL:

CNC is short for Computer Numerical Control. It's a method used in modern machining

to perform a wide range of associated tasks. In this article, we are going to take a look at

CNC machining and how it is used in both large metalworking fabrication applications

and by thousands of home hobby enthusiasts.

History

Before the invention of CNC machining, metalworking fabrication was performed by NC

(numerical controlled) machines. These machines were designed and developed in the

late 1940s and early 1950s by John T. Parsons, who worked in collaboration with MIT.

The work being conducted by Parsons and MIT was commissioned by the U.S. Air Force

as a means to develop a more cost-effective way to manufacture aircraft parts featuring

complex curved geometries. Over the course of the decade, NC machining became the

industry standard. In 1967, the concept of computer-controlled machining began to

circulate. In 1972, major developments in the evolution of CNC machining began to take

place, with the implementation of CAD (Computer Aided Design) and CAM (Computer

Aided Machining). In 1976, the first 3D CAD/CAM systems were introduced and by

1989, the CNC machines became recognized as the industry standard.

Significance

The original NC machines were controlled by paper punch cards that

featured a series of codes--called G-Codes--that gave the machine its positioning

instructions. These machines were all hard-wired and as such, they were not capable of

changing their pre-set parameters. With the development of CNC machines like milling

machines and lathes, G-Codes are still used as a means of control but are now designed,

controlled and conducted through computers. In some of the more recent variations of

CNC machines, G-Codes and logical commands are combined to form a new

programming language called parametric programs. Machines that feature parametric

programs allow the operator to make adjustments on-demand and make it easier to

access important system parameters.

DIFFERENT CNC MACHINES:

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CNC has different applications depending on the machines that operate on it. So if

you’re a budding operator, you should know the most common machines that can

operate on CNC.

Milling

Milling machines are common CNC machines. These devices are used in the shaping of

metal and other solid materials. It is basically a rotating cutter and a table. Milling

machines are capable of complex tool paths as the cutter is not limited to a sideways

movement but allows for an “in and out” motion. This movement is precisely controlled

by moving the table and the cutter relative to each other. Cutting fluid is then pumped in

to lubricate and cool the cut and to remove any swath that is generated by the cut.

Lathes

Lathes are machines that perform different operations such as sanding, cutting,

knurling, deformation, or even drilling. These machines work by spinning various solid

objects and then using tools that are symmetric to the axis of rotation. A lathe machine

has a single tool in which the work piece is worked against the tool. The tool is then

worked alongside or into the work piece in order to generate the feed. Lathes can be

used for different operations.

Machining Centers

These are more complex CNC machines that combine milling and turning. As milling

was described earlier, turning will be the focus of this section. Turning is the process by

which a central lathe is used in conjunction with the rotation of the material to be

turned. The cutting tool is then moved along the two axes of motions to produce

accurate dimensions.

Combining turning and milling can produce extremely precise components. And that is

what these machines are used for. However, due to the complexity of these machines,

operators have to be specialists in order to be able to operate with maximum efficiency.

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Electrical discharge machine

An electrical discharge machine (EDM) creates cavities in metals by emitting electric

sparks. This process requires an electrode, coolant, a power source, and a tank. The

cycle is accomplished by connecting the work piece to one side of the power supply and

then placing it in the tank. An electrode (made in the shape of the cavity required) is

then connected to the other side of the power supply. The tanks are then filled with

coolant and the electrode is lowered until a spark jumps between the work and the

electrode. As the coolant is a dielectric substance (resists electric currents), it requires a

smaller difference in distance in order for a spark to jump through. This means that

when the spark appears, the dielectric property has been overcome. The spark then

dislodges material thereby creating a cavity in the shape of the electrode.

CNC LATHE MACHINE

CNC MILLING MACHINE

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CNC systems

CNC systems are complex machines that transfer and store data regarding the operation

mechanism of the machines. Motion programs include point to point control, straight

cut control, and contouring control. Point to point control means the control of the tools

from one point to another in the coordinate plane. This method of control is commonly

used in drilling and boring operations. Straight cut control is the method by which a tool

is moved in all axes of the machine. The tool also has the ability to move in a 45 degree

angle. Contouring control is the means to create a tool path. It moves the tools by

interpolating points or coordinates that make up the path for the tool to follow.

Motion Control - The Heart of CNC

Motion control can be applied in many categories such as robotics, CNC operated

machine tools and Kinematics, wherein motion control in kinematics are usually

simpler. It can be mainly used nowadays with packaging, textile, assembly industries,

printing, and semiconductor production. The hardware of a motion controlled machine

usually consists of drive systems, motors, a computer, a PLC or Programmable Logic

Controller to run the programs, and an amplifier.

The basic design of a motion control system would include a motion controller to

produce a set of points including closing a position, a drive or amplifier to convert the

control signal of the motion controller into a high power electrical current, an actuator,

one or more feedback sensors, and mechanical components to convert the motion of the

actuators to the desired motion. CNC machines use programmable commands to make

inputting motion to the machine easier rather than using cranks or other conventional

machine tools. Almost all CNC machine tools can have programmable motion type

(whether it would be rapid, linear or circular), the amount of motion, the feedback rate,

and the axes to move.

Motion control is the simplest function of any Computer Numerical Control (CNC)

machine. It is precise, consistent, and automatic system of control. CNC equipments

need two or more modes of direction to which they are called axes. There are two

common axis types and they are called linear and rotary. The linear axis type of motion

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control is driven along a straight path while the rotary axis type is driven along a

circular path.

The operator of the motion controlled machine counting the number of revolutions

made on the hand wheel, added the generations of the dial would accomplish accurate

positioning. The drive motor of the machine would be rotated to a resulting amount,

which would then drive the ball screw, which would cause the linear motion of the axis.

The feedback device at the end of the ball screw would confirm its revolutions.

The same linear motion can be found on a table vise. When you rotate the vise crank, it

would also rotate a lead screw, which would then be able to drive the movable jaw in

the table vise. In comparison to a motor controlled CNC machine, the linear axis in it is

extremely precise compared to that of a table vise. This is because the number of

revolutions of the axis drive motor in the CNC machine accurately controls the amount

of linear motion along the axis.

A CNC command programmed and executed within a control of a machine would tell the

drive motor of the machine as to how many number of precise times it would rotate.

This in turn would rotate the ball screw then the ball screw would drive the linear axis.

After the process has started, a feedback device located at the end of the ball screw

would confirm the programmed number of rotations that the machine would run has

taken in effect.

How would axis motion be controlled?

Utilizing a form of coordinate system would make axis controlling a whole lot simpler

and more logical to the CNC control. Two coordinate systems that are being used in CNC

machines that have been popular are rectangular and polar coordinate system, to which

the more popular of the two is the rectangular coordinate system. Graphing is a

common application for the rectangular coordinate system and is needed to cause

movement in a CNC machine.

CODING

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The programming language that CNC uses is called a G-Code. These codes actually

position the parts and do the work. To be able to have a machine work properly, you

have to input the correct variables such as axes, reference points, the machine

accessories, and whatnot. Every machine has a different set of variables so you have to

be careful to take note of the differences.

Aside from the G-Code, logical commands or parametric programming can be used to

make the process more time-efficient. This type of programming language shortens

lengthy programs with incremental passes. A loop can also be programmed thereby

removing the need for coding repetitions.

Because of these features, parametric programming is more efficient than CAM. It

allows users to directly and efficiently make performance adjustments. It also allows

extensions to the functionality of the machine it is running on.

And that makes CNC.

G CODES AND M CODES OF PROGRAMS:

G CODES:

G00                       Rapid traverse

G01                       Linear interpolation

G02/G03            Circular interpolation

G07                       Tangential circle interpolation

G08/G09              Path control mode and "Adaptive Look ahead" function

G10/G11             Block pre-processing control

G12/G13             Circular interpolation with radius input

G17-G20              Plane selection

G25/G26 Programmable working area limitation ON/OFF

G33                        Thread cutting/rigid tapping with constant lead

G34/G35 Thread cutting/rigid tapping with variable lead

G36/G37              Programmable feed rate limitation

G38/G39              Mirror image

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G40-G44               Tool radius compensation

G50                        Scaling

G51/G52               Part rotation

G53-G59               Settable Zero offsets

G63/G66               Programmable feed rate/spindle speed override

G70/G71               Inch/metric dimensioning

G72/G73               Interpolation with in position stop

G74                       Home position

G80-G89               Canned cycles

G90/G91               Absolute/incremental programming

G92                       Position register preset

G94/G95               Feed rate

G160-G164           ART learning function

G186                     Programmable tolerance band

M CODES:

M00                       Program stop

M01                       Optional stop

M02/M30               End of program

M03/M04/M05   Spindle control (cw/ccw/stop)

M06 2ND coolant motor on

M07 2ND coolant motor off

M08 Coolant motor off

M09 Coolant motor on

M11 Tool probe enable

M12 Part probe enable

M13 Disable part probe

M17 End of sub routine

M19 Spindle orientation

M20 Chuck high pressure OD clamp

M21 Chuck high pressure ID clamp

M22 Chuck low pressure OD clamp

M23 Chuck low pressure ID clamp

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M24 Tail stock quill forward

M25 Tail stock quill retract

M26 Tail stock quill plunger engage

M27 Tail stock quill plunger disengage

M30 End of program

M31 Bar feed on

M35 Part catches forward

M36 Part catches retract

M39 Steady lubrication on

M40 Spindle auto gear range

M41 Spindle neutral range

M42 Spindle low range

M43 Spindle high range

M48 Steady close

M50 Steady open

SAMPLE PROGRAMS:

1.

PROGRAM:

N5 G54*

N10 M42*

15

N15 G95 S500 M4*

N20 T01D1M8; //FACING TOOL PSSNL 252508 SNMG120404*

N25 G00 X80 Z0*

N30 G01 Z-1 F0.1*

N35 X0*

N40 G00 X200 Z200*

N45 T02D1M8; //OD TURNING TOOL PDJNL 2525M15 DNMG 150604*

N50 X80 Z-1*

N55 G01 X70*

N60 X70 Z-100 F0.2*

N65 G00 X71 Z-1*

N70 G01 X60*

N75 Z-100 F0.2*

N80 G00 X61 Z-1*

N85 G01 X50*

N90 Z-100 F0.2*

N95 X100Z 100*

N100 M30*

2.

16

N5 G54*

N10 M42*

N15 G95 S500 M4*

N20 T01D1M8; //FACING TOOL PSSNL 252508 SNMG120404*

N25 G00 X80 Z0*

N30 G01 Z-1 F0.1*

N35 X0*

N40 G00 X200 Z200*

N45 T02D1M8; //OD TURNING TOOL PDJNL 2525M15 DNMG 150604*

N50 X80 Z-1*

N55 G01 X70*

N60 X70 Z-50 F0.2*

N65 G00 X71 Z-1*

N70 G01 X60*

N75 Z-50 F0.2*

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N80 G00 X61 Z-1*

N85 G01 X80 F0.1*

N90 X70*

N95 Z-100 F0.2*

N100 G00 X200 Z 200*

N105 M30*

3.

INCREMENTAL PROGRAMME:

N5 G54*

N10 M42*

N15 G95 S500 M4*

N20 T01D1M8; //OD TURNING TOOL PDJNL 2525M15 DNMG 150604*

N25 G00 X80 Z0*

N30 L500 P3*

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N35 G00 G90 X200 Z200*

N40 M30*

SUB PROGRAMME:

L500

N5 G91*

N10 G00 X-5*

N15 G01 Z-100 F0.1*

N20 G00 X1 Z-100

N25 X-1*

N30 M17*

CANNED CYCLE:

SUB PROGRAMME:

L500

N5 G01 X0 Z0 F0.1*

N10 X50*

N15 Z-100 F0.2*

N20 X80 F2*

N25 M17*

N5 G54*

N10 M42*

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N15 G95 S500 M4*

N20 T01D1M8; //OD TURNING TOOL PDJNL 2525M15 DNMG 150604*

N25 G00 X80 Z0*

N30 CYCLE 15(“L500”…….)*

N35 M30*

ADVANTAGES OF CNC:

CNC machines can be used continuously 24 hours a day, 365 days a year and only

need to be switched off for occasional maintenance.

CNC machines are programmed with a design which can then be manufactured

hundreds or even thousands of times. Each manufactured product will be exactly

the same.

Less skilled/trained people can operate CNCs unlike manual lathes / milling

machines etc.. Which need skilled engineers.

CNC machines can be updated by improving the software used to drive the

machines

Training in the use of CNCs is available through the use of ‘virtual software’. This

is software that allows the operator to practice using the CNC machine on the

screen of a computer. The software is similar to a computer game.

CNC machines can be programmed by advanced design software such as

Pro/DESKTOP®, enabling the manufacture of products that cannot be made by

manual machines, even those used by skilled designers / engineers.

Modern design software allows the designer to simulate the manufacture of

his/her idea. There is no need to make a prototype or a model. This saves time

and money.

One person can supervise many CNC machines as once they are programmed

they can usually be left to work by themselves. Sometimes only the cutting tools

need replacing occasionally.

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A skilled engineer can make the same component many times. However, if each

component is carefully studied, each one will vary slightly. A CNC machine will

manufacture each component as an exact match.

DISADVANTAGES OF CNC:

CNC machines are more expensive than manually operated machines, although

costs are slowly coming down.

The CNC machine operator only needs basic training and skills, enough to

supervise several machines. In years gone by, engineers needed years of training

to operate centre lathes, milling machines and other manually operated

machines. This means many of the old skills are been lost.

Fewer workers are required to operate CNC machines compared to manually

operated machines. Investment in CNC machines can lead to unemployment.

Many countries no longer teach pupils / students how to use manually operated

lathes / milling machines etc... Pupils / students no longer develop the detailed

skills required by engineers of the past. These include mathematical and

engineering skills.

PUNCHES:

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Punches are used in presses to get uranium pellets which are filled in

the fuel rods which make up the fuel bundles. The punches are used to apply pressure n

the uranium powder to get a solid pellet of uranium. The punches are fixed in double

acting hydraulic pressure and pressure is applied. The pellets are then grinded,

inspected and then filled in the fuel rods.

Punches materials:

Punches are prepared using OHNS material. OHNS stands for oil hardened-non

shrinking tool steel. The 0-series tool steels are the oil hardened steels having the

properties of excellent abrasion resistance, toughness, and machinability

characteristics.

O1 Tool Steel is an electric-furnace melted, oil-hardened, non-shrinking, general-

purpose tool steel. It is chemically composed of approximately 0.95 percent carbon, 1.1

percent manganese, 0.6 percent chromium, 0.6 percent tungsten and 0.1 percent

vanadium. The hardening temperature of O1 tool steel is between 790 degrees Celsius

and 820 degrees Celsius.

Uses:

O1 Tool Steel is not easily abraded, has high surface hardness post

tempering, does not deform during hardening and can be machined well. Further, it also

has a low hardening temperature (and, therefore, can be heat treated in homes and

shops), and does not lose shape during quenching. It is inexpensive and readily

available. O1 Tool Steel is ideal for making tools and knives, as it can be easily

sharpened.

Strength and Hardness: Strength of a metal determines the extent to which it may

deform when load is applied on it. Strength can be measured based on various

parameters, such as the maximum ability to take strain, resistance to wear and tear,

impact handling, or how the material performs when subjected to frequently changing

22

load conditions. Strength generally increases as the carbon and manganese content

increases. Given the high percentage of both of those,

O1 Tool Steel is strong. Hardness of a material indicates its resistance to get indented

that is not temporary (i.e.; it persists even after the load conditions are removed, as

opposed to the strength that is an indication of its performance only when the load is

applied), and carbon is also the primary hardening element in steel. The Rockwell

method measures the hardness of O1 Tool Steel to be in the range of 64 RC to 58 RC

(this is the most commonly used measurement technique).

Toughness and Brittleness: Toughness of a material determines whether it can be

subjected to shock conditions, and the extent to which it may undergo deformity in

shape but still not snap. If subjected to a proper treatment process,

O1 Tool Steel tends to be very tough. As opposed to toughness, brittleness measures

whether a material will snap instead of getting deformed, when load is applied. Alloy

steels like O1 Tool Steel are less brittle than cast or pig iron because of the presence of

magnesium.

Ductility and Malleability: Ductility is a material's ability to be drawn into wires without

breaking. Ductility decreases with increasing carbon, and because O1 Tool Steel has

very high carbon content, it is not very ductile.

On the other hand, malleability determines a material's ability to be rolled into sheets

without getting ruptured. Since O1 Tool Steel has little or no residual elements like

copper, nickel or molybdenum, it is quite malleable and can be worked upon even at low

room temperature

WHERE ARE THE PUNCHES USED?

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PUNCHES USED FOR MAKING PELLETS PELLETS ARE PREPARED

Manufacturing of two top punches through CNC machine:

Program 1:

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N5 G54* // WORK OFFSET //

N10 M42* // SPINDLE SPEED OF LOW RANGE //

N15 G95 S 500M4*

N20 T01D1M8; //TURNING TOOL PDJNL 2525M15 DNMG 150604//*

N25 GOO X30Z0*

N30 G01 X28 F0.2*

N35 G01 X30 Z-181.5 F0.2*

N40 G01 X30 F0.2*

N45 GOO X30 Z0*

N50 GO1 X25.5 F0.2*

N55 G01 Z-181.5 F0.2*

N60 G01 X28 F0.2*

N65 G00 X2000 Z2000*

N70 T02D1M8; //GROOVE TOOL: TH-WIDAX 69 327 41 820 KC 5025// *

N75 GOO X 25.5 Z-45.5*

N80 G01 X17.5 F0.06*

N85 G00 X30*

N90 G00 Z-50.5*

N95 G01 X17.5 F0.06*

N100 G00 X30*

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N105 G00 X200 Z 200*

N110 T01D1M8; //TURNING TOOL PDJNL 2525M15 DNMG 150604//*

N115 G00 X25.5 Z -50.5*

N120 G00 X 18.5*

N125 G01 Z-181.5 F 0.2*

N130 G01 X25.5 F0.2*

N135 G00 Z-50.5*

N140 G00 X17.5*

N145 G01 Z-90 F0.2*

N150 G01 X18.5 F0.2*

N155 G00 Z-132

N160 G01 X17.5 F0.2*

N165 G01 Z-181.5 F0.2*

N170 G01 X25.5 F0.2*

N175 G00 X200 Z200*

N180 G00 Z-180*

N185 G00 X17.5*

N190 G2 X19 Z-181.5 CR=1.5*

N195 GO X25.5*

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N200 G00 Z-41.5*

N205 GOO X17.5*

N210 G2 X19 Z-40.5 CR=1.5*

N215 G00 X30*

N220 G00 X200 Z200*

N225 TO3D1M8; //PARTING TOOL HSS (2MM WIDTH)//*

N230 G00 Z-112*

N235 G00 X18.5*

N240 G01 X14 F0.06*

N245 G00 X30*

N250 GOO X200 Z200*

N255 M30* // program stop//

Using this program the OHNS raw material is brought to the shape of two

punches joined in between. Tolerances are provided on the dimensions for further grinding

operations and for final polishing operations. After machining in CNC the components are

sent to heat treatment section.

In heat treatment section, the component undergoes through various heat treatment

processes. They are:

1.HARDENING: It is hardened at a temperature of 880o C for 5-6 hours and then oil

quenched. The hardening process is followed by cryogenic heat treatment process

2.CRYOGENIC HEAT TREATMENT:

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Cryogenics or deep freezing is done to make sure there is no retained Austenite during

quenching. When steel is at the hardening temperature, there is a solid solution of Carbon

and Iron, known as Austenite. The amount of Martensite formed at quenching is a function

of the lowest temperature encountered. At any given temperature of quenching there is a

certain amount of Martensite and the balance is untransformed Austenite. This

untransformed austenite is very brittle and can cause loss of strength or hardness,

dimensional instability, or cracking.

Quenches are usually done to room temperature. Most medium

carbon steels and low alloy steels undergo transformation to 100 % Martensite at room

N15 G95 S450 M4*

N20 T05 D1M8; //RADIUS FORMING TOOL VCMT 16T 304//*

N25 G01 X17.695 Z0 F0.1*

N30 G01 X15.2 Z-0.63 F0.1*

N35 G03 X0 Z0 CR= 46.15*

N40 M30*

This process is done for face forming on the punch. After this polishing is done on the

surface. Later the inspection is done and components are sent to uranium oxide plant.

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MACHINING TIME:

The time taken to convert the raw material to required product is the machining time of

that process.

In conventional lathes , along with the machining time much more time is spend on

operations like job setting , job changing, tool setting, measuring etc. These times are

calculated randomly on various machines and the data is used to calculate the ideal time for

operations in conventional lathe.

Job setting Measuring Tool setting Job changing

5 min 30 sec 30 sec 10 sec 5min

5min 25 sec 40sec 30sec 6min

5 min 40 sec 50sec 40sec 2min

1min 30 sec 25sec 15sec 4.5min

2min 10 sec 30sec 35sec 3min

3min 5 sec 35sec 20sec 4min

6min 40 sec 10sec 15sec 2min

Using such data and in reference to the job the ideal time is calculated and added to the

theoretical machining time to get the total time.

Time taken for completion of operation 1 in CNC machine: 4 min 40 sec

Time needed to complete the same task in conventional lathe is:

Operation1: Turning from 30mm dia to 28 mm dia (length 181.5mm) – 0.907min+ ( job

setting – 1min, measuring- 40 sec, tool setting- 30 sec )=3.073 min

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Operation2: Turing from 28 to 25.5mm dia (length 181.5mm) – 0.907 min +( tool setting-

30sec )= 1.407 min

Operation 3: Turning from 25.5mm to 18mm dia (length 141)- Done in 3 cuts – 2.1151min+

(tool setting- 30 sec , measuring 40 sec)= 3.28 min

Operation4: Turning from 18.5 mm to 17.5mm dia (length=99mm)= 0.495+(measuring 45

sec tool setting – 30sec )= 1.745min

Operation5: Parting for 2 mm length- 30 sec+( tool setting time- 1min)=1.5min

Total time taken in conventional lathe: 11 min

Conclusion:

Thus the conventional lathe takes much more time than the time consumed by the same

component being machined in CNC. Moreover the number of components that can be

machined using CNC is much greater than the number of components that can be machined

using conventional lathe in a given time. The accuracy obtained and the finish of the

component is better in CNC machine.

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