Abrasive Machining PPT MFG Chapter26 Final - Copy

7/23/2019 Abrasive Machining PPT MFG Chapter26 Final - Copy

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Manufacturing Engineering Technology in SI Units,Manufacturing Engineering Technology in SI Units,

66thth EditionEdition Chapter 26:Chapter 26:

Abrasie Machining and !inishingAbrasie Machining and !inishing" erations" erationsCopyright © 2010 Pearson Education South Asia Pte Ltd



Chapter Outline

Introduction

Abrasives and Bonded Abrasives

The Grinding Process

Grinding Operations and Machines Design Considerations for Grinding

Ultrasonic Machining

Finishing Operations

Deburring Operations

cono!ics of Abrasive Machining and Finishing O

perations

Copyright © 2010 Pearson Education South Asia Pte Ltd



Introduction

Some manufacturing processes cannot produce the

required dimensional accuracy or surface finish

An abrasive is a small, hard particle haing sharp

edges and an irregular shape

A!rasies is remoing of small amounts of material

from a surface through a cutting process that produces

tiny chips

Grinding wheels can sharpen"nies and tools

Sandpaper or emery cloth can

smoothen surfaces and remoe

sharp corners




Introduction

A!rasies are hard and used in finishing processes for

heat#treated metals and alloys

Applications include$

1% &inishing of ceramics and glasses2% Cutting off lengths of !ars, structural shapes, masonry

and concrete

'% (emoing un)anted )eld !eads and spatter

*% Cleaning surfaces )ith +ets of air or )ater containinga!rasie particles%




Introduction




Abrasies and #ondedAbrasies A!rasies that are commonly used$

"# Conventional abrasives

$# %uperabrasives

A!oe a!rasies are harder than conentional cutting#tool materials

Cu!ic !oron nitride and diamond are the t)o hardest

materials "no)n referred to as superabrasives

Friabilit& defined as the a!ility of a!rasie grains tofracture into smaller pieces




Abrasies and #ondedAbrasiesAbrasive T&pes

Commonly found in nature are emery , corundum

-alumina., quartz , garnet and diamond

A!rasies that hae !een made synthetically$"# Alu!inu! o'ide

$# %eeded gel

(# %ilicon carbide

)# Cubic boron nitride

*# Dia!ond




Abrasies and #ondedAbrasiesAbrasive Grain %i+e

A!rasies are ery small )hen compared to the si/e of

cutting tools and inserts

A!rasies hae sharp edges and allo) remoal ofsmall quantities of material

ery fine surface finish and dimensional accuracy can

!e o!tained using a!rasies as tools

Si/e of an a!rasie grain is identified !y a grit nu!ber Smaller the grain si/e, larger the grit num!er




Abrasies and #ondedAbrasiesAbrasive,-or.piece/!aterial Co!patibilit& Affinity of an a!rasie grain to the )or"piece material is

important he less the reactiity of the t)o materials, the less

)ear and dulling of the grains occur during grinding (ecommendations )hen selecting a!rasies$

"# Alu!inu! o'ide0 Car!on steels, ferrous alloys, andalloy steels%

$# %ilicon carbide: onferrous metals, cast irons

(# Cubic boron nitride0 Steels and cast irons

)# Dia!ond0 Ceramics, cemented car!ides, hardenedsteels




Abrasies and #ondedAbrasies:$rinding %heels Each a!rasie grain remoes only a ery small amount

of material at a time

3igh rates of material remoal can !e achieed )hen

large num!er of these grains act together

4one !y using bonded abrasives




Abrasies and #ondedAbrasies:$rinding %heels 5n !onded a!rasies, porosity is essential to proide

clearance for produced chips and cooling

Porosity can !e o!sered !y the surface of grinding

)heel

&or non#porosity, it is fully dense and solid




Abrasies and #ondedAbrasies:$rinding %heels 4ue to their high cost, only a small olume )heels

consists of supera!rasies

6onded a!rasies are indicated !y the type of a!rasie,

grain si/e, grade, structure, and !ond type




Abrasies and #ondedAbrasies:

$rinding %heels Cost of grinding )heels depends on the type and si/e

of the )heel





#ond Types Common types of !onds$

"# 1itrified0

Consist of feldspar and clays

Strong, stiff, porous, and resistant to oils acids, and)ater

$# 2esinoid0

6onding materials are thermosetting resins

(esinoid )heels are more fle7i!le than itrified)heels





#ond Types(# 2einforced 3heels0

Consist of layers of fiberglass mats of arious mesh

si/es

)# Ther!oplastic0 8sed in grinding )heels

9ith sol#gel a!rasies !onded )ith thermoplastics

*# 2ubber0

8sing po)der#metallurgy techniques Lo)er in cost and are used for small production

quantities


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Abrasive Machining PPT MFG Chapter26 Final - Copy