Download - Grinding & Finishing Process
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9M402.21 1
Department Of Technical Education
Andhra Pradesh
Name : V.Yesu prasada Rao
Designation : Senior LecturerBranch : Mechanical Engg.
Institute : M.B.T.S Govt polytechnic,Guntur.
Year/semister : IV Semister
Subject : Manufacaturing technology-IISubject code : M402
Topic : Grinding & Finishing processes
Duration : 50 Minutes
Subtopic : Principle of metal removal by Grinding
Teaching Aids : Diagrams & ppt
Revised by : K.Chakravarty
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Recap
In the last chapter, Milling ad Gear making topics are
discussed..
Another important machining method is grinding
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On completion of this period, you would be able
to know about
Objectives
Grinding
Principle of Grinding
Purpose of Grinding
Its Advantages and Applications
Abrasives and types
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How knife is sharpened ?
How scissors are sharpened ?
How chisels are sharpened ?
How axe are sharpened ?
Do you know?
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Introduction
Quality working surface cannot be produced by the usual
machining
Good surface finish can be obtained by grinding
The art of grinding goes back many centuries over 5,000
years ago by Egyptians
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Grinding A process of removing metal in small quantities by
using an abrasive wheel
Grinding wheel may be regarded as a multi point cuttingtool
A grinding wheel is composed of abrasive grains
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After some time the grains become dull faced
The dull grain breaks away and exposing new cutting edge
to work piece due to pressure and heat created between
wheel and work piece
Working principle of Grinding
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Abrasive grains
Fig-2
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The cutting action of abrasive grains
Fig-3
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Animation of grinding process
Fig-4
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Purpose of Grinding
To bring the component to close size
To obtain required surface finish
To machine very hard surfaces
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Advantages of grinding
The surface finish obtained is superior
One of the most dimensionally accurate machining
processes Hardened components can be machined
Grinding permits to machine light and delicate parts due
to requiring little pressure
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Advantages of grinding
Surface unevenness can be eliminated
Various kinds of works can be grinded
Designed geometrical configuration can be achieved
It removes little material of order 0.25 to 0.50mm
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Disadvantages of Grinding
Work surface gets over heated
Wheel wear results duplicate parts do not have the same
dimensions
Grinding is not suitable for heavy metal removing
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Disadvantages of Grinding
For some complicated parts grinding needs attention.
Achieving true parallelism requires skill.
Achieving concentricity needs attention.
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Grinding
Fig-5
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Applications of grinding
All cast components require grinding
Welded components require grinding
Crank cases , Forged components
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Summary
So far, we have learnt about
Grinding and its uses
Working principle of grinding
Applications of grinding
Advantages and disadvantages of grinding
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Abrasives
An abrasive is a small non metallic hard material having
sharp edge and an irregular shape
The abrasive must have the following characteristics
Must be harder than material being ground
Must be strong to withstand grinding pressure
Must be heat resistant
Must be capable to break when cutting edge is dull.
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Abrasives
Fig-6
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Natural Abrasives
Sand stone is relatively soft and cannot be used for
grinding hard materials
Emery and corundum are natural Aluminum Oxides,having greater hardness and better abrasive action
Diamond is hardest natural abrasive but limited usage
due to high cost
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Sand stone or solid quartz
Is one of the natural abrasive
stones from which grind stones
are shaped
The Quartz of cutting agent is
relatively soft so that materials
harder than the Quartz can be
abraded , grounded rapidly
Fig-7
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Emery
Is a natural aluminium oxide
It contains 55 to 65 percent
alumina and remaining
consists of iron oxide and
other impurities.
Fig-8
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Corundum
It is also a natural aluminium
oxide
It contains 75to95 percent of
aluminium oxide and
remaining consists of
impurities
Fig-9
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Corundum abrasives
Fig-10
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Diamond
It is the best natural abrasive
Diamonds of less than gem quality are gashed to
produce abrasive skins for making grinding wheels to
grind cemented carbides, glass, marbles and garnets
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Diamond (abrasives)
Fig-11
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Artificial abrasives
Silicon carbide is harder but not tougher (brittle)
Used for grinding materials of low strength such as iron,
brass, bronze.
Aluminum Oxide is tough and not easily fractured.
It is used for grinding high tensile strength materials such
as steel and malleable cast iron
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Silicon carbide
It is manufactured from 56 parts of silica sand, 34
parts of powdered coke, 2 parts of salt and 12 parts
of saw dust.
It is used for cemented carbide, ceramic, grey castiron , brass.
This is manufactured under the trade names of
carborundum, crystolen, carbolon,electrolon etc.
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Silicon carbide crystal
Fig-12
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Aluminium oxide
It is manufactured by heating
mineral bauxite, a hydrated
aluminium oxide clay mixed
with ground coke and iron in
an arc-type electric furnace
Fig-13
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Aluminium oxide
It is better adopted to grinding materials of high tensile
strength, such as high speed steels , tough bronzes etc
This is manufactured under the trade names of aloxide,
aluminium, borolon ,electrite etc
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Aluminium oxide grinding wheel
Fig-14
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Comparison of SIC and AL2O3
Abrasivematerial
Year ofDiscovery
Hardness(knoop)
Properties and uses
Sic 1891 2200-2800 Used for brass, bronze,
aluminium, stainless
steel, and cast iron.
AL2O3 1893 1600-2100 Soft and tough then sic,used on steel,
malleable cast iron,
tough bronzes.
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Summary
In this class ,we have discussed about
Principle of Grinding
Purpose and Applications of Grinding
What is an abrasive
Types of abrasives and their properties
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Quiz
1.Grinding process is mainly used to
a) Finishing
b) Shouldering
c) Knurling
d) Centering
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Quiz
2.The ability of the grains to manufacture and expose newsharp edge is known as
a) Malleability
b) Tough
c) Friability
d) Abrasive buffing
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Quiz
3. Which of the following natural abrasive is harder
a) Sand stone
b) Corundum
c) Diamond
d) Emery
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4. The natural aluminum Oxide is
a) Sand stone
b) Emery
c) Corundum
d) B&C
Quiz
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Quiz
5. What is the correct sentence among the listed below
a) Grinding process cannot be used to machine hard parts
b) Grinding requires high pressure
c) We can produce duplicate parts with this process
d) Grinding is not suitable for high metal removal
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1. Explain working principle of grinding
2. Explain advantages and disadvantages of grinding
Frequently asked questions
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Frequently asked questions
3. What are the characteristics of good abrasives?
4. What are the different types of abrasives? Explainbriefly?