Project at Sil
-
Upload
ashishgiri -
Category
Documents
-
view
131 -
download
3
Transcript of Project at Sil
AProject Report
onTOOL LIFE OF HOB & BROACH
Under the Guidance of
Mr. Krishna Kumar(Chief Manager)
Mr. D.R. Singh(Deputy Manager)
Er. Neeraj Kumar Mishra
In
Scooters India Limited, Lucknow
Submitted by
Ashish GiriDeptt. of Mechanical EngineeringBundelkhand University, Jhansi
CONTENTS
Certificate
Acknowledgement
Vision Mission
Quality Policy
About Scooter India Ltd.
Products
Departments
About Machine Shop
About Line No. 7
Machine Used in Line No. 7
Manufactured Component of Line No. 7
Main Project
DECLARATION
I certify that Mr. Ashish Giri, a student of Institute of
Engineering & Technology, Bundelkhand University, Jhansi,
Mechanical Engineering II year has completed a project on "Tool Life
on Hob and Broach" under my guidance.
I certify the originality of the project report. I wish a bright
future for him.
Date : Mr. Krishna Kumar(Chief Manager)ManufacturingS.I.L. Lucknow
DECLARATION
I certify that Mr. Ashish Giri, a student of Institute of
Engineering & Technology, Bundelkhand University, Jhansi,
Mechanical Engineering II year has completed a project on "Tool Life
on Hob and Broach" under my guidance.
I certify the originality of the project report. I wish a bright
future for him.
Date : Mr. D.R. Singh(Deputy Manager)
ManufacturingS.I.L. Lucknow
ACKNOWLEDGEMENT
It is with great pleasure that I acknowledge the support of Mr.
Krishna Kumar (Chief Manager), Mr. D.R. Singh (Deputy Manager) and
Er. Neeraj Kumar Mishra, Machine Shops as well as the employees of
Machine Shop, Tool Room, Lab Room, Assembly Shop and Quality
Department.
To be thanked also are the machine operators and other factory
employees, who cooperated with me and made it sure that I learn
something from the operation that they are performing.
(Ashish Giri)
VISION OF THE ORGANISATION
To grow into global company constantly striving meet the
changing needs of customer through constantly improving existing
product adding new products and opting new technology and
expanding the customer base.
CORPORATE MISSION
To fulfill customer needs for economical and staff made of road
transport and quality engineering product through contemporary
technology.
QUALITY POLICY OF S.I.L.
We are committed to meet the customer requirements and
continuously improve our quality management system. The company
sales and services quality objective within the frame work of this
policy.
ABOUT SCOOTERS INDIA
Incorporated in 1972, Scooters India Limited is an ISO
9001:2000 and ISO 14001 Company, situated at 16 Km mile stone,
South-west of Lucknow, the capital of Uttar Pradesh on NH No 25 and
is well connected by road, rail and air.
It is a totally integrated automobile plant, engaged in designing,
developing, manufacturing and marketing a broad spectrum of
conventional and non-conventional fuel driven 3-wheelers.
Company’s plant owes its origin to M/s. Innocenti of Italy from
which it bought over the plant and machinery, design, documentation,
copyright etc. The company also possesses the world right of the
trade name LAMBRETTA / LAMBRO.
In 1975, company started its commercial production of Scooters
under the brand name of Vijai Super for domestic market and
Lambretta for overseas market. It added one more wheel to its
product range and introduced three wheelers under the brand name
of VIKRAM/LAMBRO. However, in 1997, strategically, the company
discontinued its two-wheeler production and concentrated only on
manufacturing and marketing of 3 wheelers. These three wheelers
have become more relevant in the present socio-economic
environment as it transports goods and passengers at least cost.
The company has its own marketing network of Regional Sales
Offices all over India, catering to customer’s requirements in the
areas of sales and services.
DESIGN AND DEVELOPMENT
DEPARTMENT
Design & Development has become the prime mover for the
organisation. The business today is customer driven. The department
remains in constant touch with the customers to transplant their
needs and thinking on the drawing board - nay on the computer
screen. The department serves the internal customers through
design, development, standardization, value engineering, defect
removal etc. Equipped with Computer Aided Design Laboratory ( CAD
lab ), Advanced Instrumentation, testing rigs prototype manufacturing
facilities and internet, the company's D & D is recognised by the
Ministry of Science and Technology, Govt. of India. It has the
distinction of the developing first zero pollution electric three wheeler
in the world. Company besides its own in-house R&D ; also works in
association with leading Research Associations & Educational
Institution like I.I.T 's. Kanpur; I.I.T. , Dehradun; A.R.A.I. Pune;
T.C.I.R.D. Patiala etc
Computer Aided Design Laboratory
The CAD laboratory provides a wide range of facilities. The
versatility of brains combines with the flavour of new creation to
evolve a quality product. All the designing & drafting process moulds
into a shape in this well-equipped environment of CAD
laboratory.Which includes FE analysis, Working model simulation &
designing through Auto-Cad 14.
ASSEMBLY DEPARTMENT
The components manufactured in plant as well as those bought
have to be finally assembled to make the product three wheelers. In
the process many sub assemblies, too, are involved. However, two
main assemblies worth mentioning are engine assembly and vehicle
assembly. Both are conveyorised. Every 5 minutes a three wheeler
rolls down the conveyor. The vehicle conveyor has 23 stations. Speed
can be adjusted to meet increasing demand.
DIE CASTING SHOP
The biggest die casting shop in this part of the country handles
both Aluminum and Zinc alloys. Equipped with pressure die casting
machines of 160, 250, 400 and 1,000 tons locking pressure, the metal
is fed to machines from individual holding furnaces of 75/150 kg.,
which in turn are fed by mother melting furnace of 500 kg. aluminum
capacity.
The shop based on projected area, is capable of producing
aluminum die casting upto 5 kg. in weight. The shop is backed by
chemical and metallurgical labs as also with a die maintenance
section. The well-equipped machineries are used in this department in
single shift, except two machines that are used in two shifts; that
produce all the accessories required by this organization. The die
casting of various type of components like Gear box housing,
Crantcase, Front wheel drum, Rear wheel drum, Bell housing,
Magneto flange, Cylinder head, lower and upper Handle bar, Levers,
Differential housing cover, Brake shoe etc are undertaken.
Die casting some components for fulfilling customers'
requirement are also taken up. Some of our customers are BHEL,
Bhopal; Greaves India Limited, Aurangabad to whom supplying the
Gear boxes and 422 cc aluminium Engine are supplied.
FABRICATION DEPARTMENT
The fabrication operations are carried out in Two departments viz. Press
Shop and Welding Shop. The Press Shop is equipped with 20 presses ranging
from 10 tons to 550 tons. Presses are fed by sheets cut to size on shearing
machines of 3000x6 & 2500x3 mm. size. Components ranging from washer to
cabin roof and door(1000x1200 mm.) are being processed in this shop.
The Welding Shop is equipped with battery of Spot welding, MIG welding,
Seam welding as well as Arc welding machines. CO2 welding is extensively used
for getting close tolerance on welded structures. The department has its own
auxillary shop for maintenance of tools and dies.
FOUNDRY LAB
The foundry, most modern in this part of the country, can
produce all grades of grey cast iron as well as S. G. iron. In fact, it had
been innovative to find new processes of modulisation, for which it
was granted 2 patents.Equipped with an Induction Melting furnace,
Shell Moulding Machines & Core Shooters, Green Sand Moulding
facilities, Isothermal Heat Treatment Furnace, one sand muller
machine, two shot blasting machine, two set jolting machines for
green sand moulding, fettling and shot blasting equipments, its
normal range of production weighs upto 8 Kgs. on a pattern plate of
450x600 mm. However, foundrymen are trained to make casting even
of 1 ton weight if emergent requirement arises.
The foundry is not fully loaded with its captive requirement.
Spare capacity is utilised for producing sophisticated castings of
prestigious customers like BHEL, Indian Railways, Aerospace, Brakes
India Limited, Crompton Greaves limited. The induction furnace has a
capacity of 1.3 tons. The two types of moulding is been done here. 1.
Shell moulding 2. Green sand moulding. The foundry can manufacture
a wide range of products namely Differential housing, Differential
cages, Power transimission wheel, Crankcase flange, Magneto motor,
Engine output flange, Adapter plate for electric vehicle, Cylinder for
both Vikram 410 petrol version and Vikram 750 diesel version.
ABOUT MACHINE SHOP
Machine shop has a wide variety of machines like General purpose
machine, Special purpose machine, Multispindle automatic machine,
Single spindle automatic machine etc; which are mainly working on
single shift through eight different lines. Line no 2 is basically
machining the aluminium components. crank shaft and cylinder
machining is usually done on line no 3. Line no. 4 is the Grinding line
where the grinding process is done. Heat treatment is performed in
line no 5, while different turning of shafts and gear shaping and
shaving are carried on line no 6.Line no. 7 includes the functioning of
gear manufacture process mainly broaching, hobbing, finish turning,
gear shaving etc. Machining of different levers, centreless grinding of
tubes and shafts, serration / thread rolling operations is achieved in
line no. 8 & lastly different components are fed in two other lines by
line no. 9. Blank turing of gear and machining of parts is done on
multi spindle and single spindle automatic machine. Engine
components and some vehicle component are the prime production
PAINT SHOP
Paint shop includes three sections namely Paints section, spray
phosphating section, pickling.Paint section includes two convention
painting spray booth & one electrostatic painting plant. The first one
is called conventional primer where mainly frame paintings are done.
The equipments used for conventional painting are Bullow's 230 spray
gun and pressure fit tanks (we prepare paints). The various types of
frames like Diesel 750, Mini petrol, Mini diesel, Diesel floor mounting,
Diesel Nepal, Diesel scrubber, Electric vehicle are painted here. The
other conventional booth is known as conventional finish booth. Here
the frame accessories like cabin front, roof top, front fork, axle
housing are painted. In electrostatic plant the accessories of the
frame, the component of lighter weight and minimum size like
silencer, pillar and various brackets are painted here.
In spray phosphating the main work is to clean the components
before painting or to make surface according to paint requirement.
After phosphating the products goes to passivation for converting
ferrous to ferric for paintings need. The products comes from welding
shop, press shop and machine shop to phosphating, and after the
process is being done the products go to vehicle assembly. The
pickling department is mainly for maintaining the surface of heavily
corroded materials.
TOOL ROOM
The tool room is a cell where brain combines with versatility to
evoke the new era of invention. The designs of tool coming from main
tool planning departments are implemented here. The tool room is
furnished with well equipped machineries namely, CNC machine
(Taiwan), Jig Boring machine (Czec Republic), Jig Grinding machine
(Switzerland), Profile Grinding machine (Germany), Die shielding
machine (Czech Republic), EDM (USA), Schaublin machine
(Switzerland).
Tool room evoke a high performance output, consisting almost
99.9% of company's requirement : one die casting die per year, 1-10
press tools per month, 8-10 jigs per month, 10-12 gauges per month
and 400 C.T. tools per monthThese machines are efficiently used to
manufacture different tools and dies like Jigs & fixture, Gauges,
Cutting tools, Forging dies, Die casting dies, Development items etc.
The different activities like like turning, milling different shapes,
grinding, heat treatment, jig boring, jig grinding, checking in the
standard room, heat treatment according to the job requirement, final
inspection are undertaken in the tool room.
DEPARTMENTS
The organisation has various departments to perform different
activities competently. SIL has an organised system to control
different activities. Personnel & administration department looks after
the employees welfare, medical benefits, conveyance facilities,
maintains their personal records and controls their regularity. It also
take care of the security for the organisation. Marketing & services
department looks after the marketing of the products, provide
services to the customer and regulates the activities in its various
regional offices.
Materials controls the purchasing of the raw material, keep an
eye on the cost of the material in the market, store the different
materials and products and establishes a company-vendor
relationship. Workshop manufacture different products in steps in
different lines. Design & development is the prime creative unit for
the organisation. It brings out some brilliant design with modern
technologies. Finance & accounts section keeps track on the financial
growth and the maintenance of various types of accounts.
PRODUCTS OF S.I.L.
Scooters India Limited makes various & versatile types of three
wheelers: Vikram 450D, Vikram 410G, Vikram 600G, Vikram 750D,
Vikram 750D (WC), Vikram EV.
The products have a high payload capacity and efficiency.
These are specially designed and developed for local transportation.
However, the generation of Vikram run successfully in different
countries also. Our product is very demanding in various countries all
over the world . Germany, Italy, Sudan, Nigeria, Nepal, Bangladesh
are few of the countries. For product details click on the product
options.
MACHINES USED IN LINE NO. 7
Broaching Machines
1. Internal Splines Broaching 4976
2. Oil groove broaching machine 3505
3. Bore Broaching 2021
4. Bore Broaching 3271
5. Bore Broaching 2997
Hobbing Machines
1. Semi Automatic Hobbing Machine – 10488
2. Semi Automatic Hobbing Machine – 10576
3. Semi Automatic Hobbing Machine – 10120
4. Tag Teeth Hobbing – 2014
5. Semi Automatic Hobbing Machine – 10290
6. Eight Head Shaft Hobbing Machine – 2586
7. Eight Head Shaft Hobbing Machine – 2585
Hydraulic Press & Turning Facing, Chamfering Machines
1. Fresh turning, facing & bore chamfering Machine – 2148
2. Hydraulic Press – 392
3. Fresh Turning, Facing & Bore Chamfering – 10489
4. Hydraulic Press – 728
5. Turning – 3249
6. Hydraulic Press – 2773
7. Turning – 296
8. Turning – 10498
9. Hydraulic Press – 383
10. Turning Machine – 10490
11. Turning Machine – 10387
Shaving Machines
1. Teeth Shaving – 4817
2. Teeth Shaving – 4102
3. Speed Gear Teeth Shaving – 4395
Milling Machines
1. Milling Machine – 10466
2. Horizontal Milling Machine – 2732
3. Horizontal Milling Machine – 10621
4. Cam Milling – 10388
5. Cam Milling – 91
6. Cam Milling – 513
7. Cam Milling – 511
Lathe Machine
1. Central Lathe Machine – 441
Drilling Machines
1. Portable Drilling Machine – 2419
2. Portable Drilling Machine – 5035
Teeth Chamfering Machine
1. Teeth Chamfering Machine – 2168
2. Teeth Chamfering Machine – 2992
3. Teeth Chamfering Machine – 10623
Bench Grinding Machine for Deburring
COMPONENTS MADE IN LINE NO. 7
1. Ring Nut
2. Speed Gears (I, II, III & IV)
3. Primary Transmission Wheel
4. Engine output Gear
5. Reverse Gears
6. Spline Sleeve
7. Transmission Shafts
8. Big Spockets
9. Couplings
10. Sliding Dog
11. Reverse Gear Sprockets
12. Central Lug
ABOUT LINE NO. 7
Broaching :-
Broaches tools for cutting metal, comprising a plain pilot
portion, a tapered toothed portion and a plain shank engaging with
the pulling head on a broaching machine. The teeth have normally
single cutting edges and on a circular broaches run in series round
the tapered portion, gradually increasing in cross section as they near
the shank. They are either pushed or pulled mechanically through a
previously cored or drilled round, square, rectangular or hexagonal
hole to produce the current form. They will also finish flat surfaces,
irregularity – formed holes and open grooves such as key ways in
hubs. Another application is to the forming of teeth in internal gears
and rachets, splines in shafts etc.
They are usually made of a tough, hard, sound, non distarting
steel alloy, high carbon and case hardening types, the precise steel
depending on the service life required, the material to be cut, and the
length and form of the broached areas. Relatively few are made of
case carburizing steel and hardened high speed steel is now the most
popular material for the cutting teeth of solid and some other
broaches. The tools have to be heat treated and ground and the heat
treatment is extremely important.
Broaches for finishing internal holes differ from those for
finishing the external surface of a component. Those to be pushed
through the work are shorter than those to be pulled through. For
internal work the tools are usually solid, unless their diameter is so
great as to render distortion in heat treatment probable and serious.
The teeth are of size and form for the operation and if the broach is
more than 3½ inches. How it is often made as a composite consisting
of a tough central portion of carbon steel, conically ground, on to
which cutting segments of nickel or high speed steel are mounted in
the form of toothed rings set one over the other until the cutting
portion is adequate for the job. This makes its possible tommorrow a
segment or ring when pulled or worm and insert a replacement each
ring then move up one this costs for less than replacing the entire
broach.
Hobbing :-
In this process, the gear bank is rolled with a rotating cutter
called hob. A majority of involute gears are produced by this
method. . A grear hob looks like a worm, but carries a number of
straight flutes (gashes), cut all around, parallel to its axis. This results
in the production of separate cutting teeth and cutting edges, as
shown. In operation, the hob is rotated at a suitable speed and fed
into the gear blank. The blank also rorates simultaneously. The
speeds of the two are so synchronised that the bank rotates through
one pitch distance for each complete revolution of the hob. There is
no intermittent motion of any of the two and the generating motion
continues steadily. The hob teeth are just like screw threads, i.e.
having a definite helix angle. The hob is, therefore titled to its own
helix angle while cutting the gear so that its teeth are square with the
blank and produce a true involute shape. Spur, helical and
herringbone gears and many other shapes like splines and gear
sprockets etc. can be cut by hobbing process.
Each cutting tooth of the hob is provided relief at its back to
enable clerance. In poration, the hob can be conceived as a cylindrical
body, around which the teeth of a long rack are wrapped along a
helical path and provided with straight flutes at regular intervals,
parallel to the axis of the cylinder. Cross section of every tooth across
the helix resembles that of the rack teeth.
Types of Hobbing :-
This hobbing process is classified into different types according
to the directions of feeding the hob for gear cutting. This classification
is as follows :
1. Hobbing with axial feed.
2. Hobbing with radical feed
3. Hobbing with tangential feed
Shaving :
It is a process of finishing gear teeth by running the gear at high
speed in mesh with a gear shaving tool which is in the form of a rack
or pinton. The teeth of the shaving tool are hardened, accurately
ground and their faces are provided with serrations. These serrations
form the cutting edges which actually provide a sort of scraping
operation on the mating faces of the gear teeth to be finished. The
gear is pressed into contact with the shaving tool and the latter
rotated at high speed. The gear also rotates in mesh with the tool and
is also reciprocated simultaneously. The shaving tool carries a little
inclined teeth so that their axes can be crossed as the two come in
contact. This prevents the jamming of the two. The above relative
motion of the gear and the shaving tool results in a highly finished
surface on the gear teeth. When a rack type tool is used, the gear is
mounted on a reciprocating arbor and is brought in mesh with a
horizontal rack situated under it. The rack is reciprocated
longitudinally at high speed and the gear across it. The lengthwise
movement of the rack type tool also rotates the gear. Shaving with
rack-type tool, however, suits only small gears. The shaving tools,
although costly, have a fairly long life.
Drilling :
Drilling is an operation through which holes are produced in a
solid metal by means of a revolving tool called drill. Since it is not
possible to produce a perfectly true hole by drilling, it is considered as
a roughing operation. Obviously, therefore, where a very close
dimensional accuracy is to be maintained, this forms only the basic
operation. For such holes, drilling is followed by another operation
called reaming, in which the required dimensional accuracy and fine
surface finish is obtained by means of a multi-tooth resolving tool
called reamer. Boring is the operation employed for enlarging an
existing hole. The hole may be previously drilled, cast, punched or
produced through any other suitable operation.
In line no. 7 there are portable drilling machine are used.
It is very small, compact and self-contained unit carrying a
small electric-motor inside it. It is very commonly used for drilling
holes in such components that cannot be transported to theshop due
to their size or weight or where lack of space does not permit their
transportation to the bigger type of drilling machine. In such cases,
the operation is performed on the site by means of the portable
electric drill. Portabe drills are fairly light in weight so that they can be
easily handled by one or two men only. They are manufactured in
different sizes and capacities, thus being suitable for a wide range of
hole sizes. Also, on account of the high speeds available, a
considerable saving in time is affected by their use. Another
advantage is that the holes can be drilled by means of them at any
desired inclination. Usually they are made to hold drills upto a
maximum diameter of 12 mm. However, portable drills of upto 18
mm. dia. capacity are available.
Milling :
‘Milling’ is the same given to the machining process in which
the removal of metal takes place due to the cutting action of a
revolving cutter when the work is fed past it. The revolving cutter is
held on a spindle or arbor and the work, clamped on the machine
table, fed part the same. In doing so, the teeth of the cutter remove
the metal, in the form of chips, for the surface of the work to produce
the desired shape.
Milling machine has acquired an indispensible position in all
modern production workshops. Its specific significance lies in its
capability to perform a large number of operations which no other
single machine tool can perform. At the same time, it gives
production at a fairly high rate and within very close machine tools
like shapers, planers, slotters etc., but for small and medium size
jobs only; as it will prove to be too slow for machining very long jobs.
For small and medium jobs, the milling machine gives probably the
fastest production with very high accuracy. For this reason, it has
gained a very wide application in mass production work. Obviously,
therefore, it is very versatile machine tool.
In line no. 7 there are horizontal milling machine are used. In
this the vertical coumn serves as a housing for electricals, the main
drive, spindle bearings, etc. The knee acts as a support for the saddle,
worktable and other accessories like indexing head, etc. Overarm
provides support for the yoke which in turn, supports the free end of
the arbor. The arbor carrying the cutter rotates about a horizontal
axis. The table can be given straight motions in three directions :
longitudinal, corss and vertical up and down but cannot be swivelled.
For giving vertical movement to the table the knee itself, together
with the whole unit above it, slides up and down along the ways
provided in front of the column. For giving cross movement to the
table, the saddle is moved towards or away from the column
alongwith the whole unit above it. A brace is employed to provide
additional support and rigidly to the arbor when a long arbox is used.
Both hand and power feeds can be employed for the work.
Cam Milling :
The constant rise and fall cams can easily be cut on a universal
milling machine, equipped with a universal dividing head and a
switching type vertical milling attachment. The dividing head is
geared to the tabe feed scre in the same way as for spiral milling. end
milling cutters are usualy employed in this operation. If the table is
moved towards right, the blank approaches nearer to the cutter. Also,
because of the gearing at the back, the dividing head spindle revolves
simultaneously. The combination of these two movements. i.e. the
table movement and the spindle rotation, enables milling of cam on
the blank fitted on the dividing head spindle. Both, the cutter as well
as the dividing head spindle, should be inclined at the same angle.
Steeper the angle of inclination quicker will be the approach of the
blank to the cutter. Alternatively, we can have the cam axis above
and the cutter axis below. In that case, we will be required to move
the table towards the left for feeding the blank against the cutter.
Plain Step And Fresh Turning Between Centers :
When the work is held between centers for any sort of turning
operation, one end (left hand end) is firmly gripped in a table dog and
then the same end is supported on the tip of the live centre. Tail of
the dog engages with the driving plate and the other end (right hand
end) of the job is supported on the dead centre fitted in the tail stock.
Work revolves during the operation and the tool is fed against the job.
Enough care should be taken while starting the operating, particularly
by a beginner. Speed of spindle and its direction of rotation should be
checked and suitably adjusted. Rough cuts in the beginning should be
followed by finishing cuts for which the spindle speed should be
increased and depth of cut reduced. Check the controls and practice
hand feeds which, in due course, can be followed by power feeds. For
taking any sort of measurement always stop the machine. In this first
the tail stock is moved and brought near the head stock to ensure a
true alignment of dead and live centers by sighting along the axes of
the two. Work is then held between centers and revolved. A chalk is
held in hand gently against the revolving work and marks made near
both the ends. Continuity of these marks indicates the trueness of the
marked centers, otherwise the chalk marks will be found only on
elevated portions of the periphery of the work.
Once the larger part of the excess material has been removed
through rough turning, it is followed by Finish turning operation in
order to bring the job to correct size and provide a fine surface finish
on it. The amount of excess material to be removed through this
operation is very less and, therefore, lighter feed and smaller depth of
cut are used and the heavier tool is replaced by a finish turning too.
Facing :
It is an operation which enables the production of a flat surface
through machining at the end of a job. In this operation the tool is fed
at right angles to the axis of the job. Since no longitudinal feed is
needed, the carriage is usually clamped to the bed so that it remains
stationary during the operation. Feed to the tool is provided by
moving the cross-slide by hand. Depending upon the diameter of the
work piece the power feed can also be used. Two methods of holding
the tools are usually employed. One is to set the tool slightly inclined
to the exact right angle position so that only the tip of the cutting
edge remains in contact with the job face and the remainder of the
tool is free of the job. Another method is to set the tool parallel to the
axis of the job. This is done when the job is held in a chuck or a face
plate. In both the cases the tool can either be fed outwards, i.e., away
from the centre. Normally the selection of any one to these methods
is according to convenience, still the latter method is more commonly
employed.
The facing operation is usually performed in two steps. In the
first step a rough facing operation is done by using a heavy cross of
the order of 0.5 to 0.7 mm and a deeper cut upto 5 mm (maximum).
It is followed by a finer cross feed of 0.1 to 0.3 mm and a smaller
depth of cut of about 0.5 mm. In the first step the idea is to remove
major part of excess material while in the second step a fine finish is
provided to the surface.
MAIN PROJECT
Tool life :
The time interval for which the tool works satifactory between
two successive grintings (sharpenings). Thus it can be basically
conceived as functional life of the tool. The tool is subjected to wear
continiauly while it is operating. Obviaulsy, after sometime, when the
tool wear is increased considerably, the tool losses its ablity to cut
efficiently & must be reground. If not it will totally fail. The tool life
can be effecting used as the basis to evaluate the performance of the
tool material assess machinbility of the conditions tool life :
(1) As time Period in minutes between two successive grintings.
(2) In terms of no of components machined between two
successive grindings. This mode is commonly used when the
tool operates continuously, as the case of automatic
machines.
(3) In terms of the volume of material removed between two
successive grindings this mode of expression is commonly
used when the tool is primarily used for heavy stock
removal.
Factors affecting tool life :
The life of cutting tool as affected by the following factors :
(1) Cutting speed
(2) Feed & depth of cut
(3) Tool Ceometry
(4) Tool material
(5) Work material
(6) Nature of cutting
(7) Rigidity of machine tool & work
(8) Use of cutting fluids
Effect of Cutting speed :
Out of all the above factors the max effect on tool life is of
cutting speed. The tool life is various inversely as the cutting speed
i.e. the higher cutting speed, the smaller the tool life. Generally the
reduction an tool life corresponding to an increase in cutting speed is
Parabolic.
V Tn =C
V= Cutting speed in m./min.
T= Tool life in min.
C= Machining constant
n= Tool life index
For all practical purpose the average values of exponent (n) for
common tool materials can be taken as :-
n = .1 to 0.15 for high speed steal tools
= 0.2 to 0.5 for cemented carbide tools
= 0.6 to 1.0 for ceramic tools