Lec 10

Question 1

Abrasive machining adv

Answer 1

High dimensional accuracy

Question 2

What is abrasive machining

Answer 2

Abrasion used to remove small amounts of material by cutting processes that introduce tiny chips
Each abrasive grain removes only small amount of material
A method used to produce parts with high
dimensional accuracy
Each particle acts as a cutting tool

Question 3

Types of bond (grinding wheel)

Answer 3

Clay and Feldspar crystalline material

vitrification used to produce a glassy amorphous structure strong and stiff resistant to oil acid and water

Question 4

Bond too strong (grinding wheel)

Answer 4

Dull grains cannot be dislodged to

allow other sharp grains to perform grinding

Question 5

Bond too weak (grinding wheel)

Answer 5

Grains become dislodged easily,
hence maintaining dimensional accuracy
becomes difficult

Question 6

What is attritious wear (grinding wheel)

Answer 6

Wear of grains (flank wear of cutting tool) caused by friction between grain and workpiece involving chemical and physical reactions

Question 7

Why are abrasive grains brittle (grinding wheel)

Answer 7

if grains dull grinding inefficient therefore should fracture moderately to expose new sharp grains
continuously being sharpened

Question 8

Why is porosity important (grinding wheel)

Answer 8

Essential in bonded wheels provides cooling and clearance for minute chips produced

Question 9

What is grinding?

Answer 9

chip removal process - The grinding tool is made up of irregular shaped grains spaced randomly along the
periphery of the cutting wheel
Range of machines available for different workpiece geometries - CNC automation load - unload clamp repeat cycle path will sharpen wheel between processes

Question 10

Ultrasonic machining (drawing)

Answer 10

removal by micochipping or erosion with fine abrasive grains

Question 11

Ultrasonic machining process

Answer 11

high freq
Tip of tool vibrates
amplitude 0.05
vibration drives grain at workpiece high velocity
high stress between grain and workpiece - small area short contact time

Question 12

Tool vibration speed 20kHz or 3000000kHz ultrasonic machining

Answer 12

20kHz

Question 13

Ultrasonic machining best suited for

Answer 13

Brittle materials as high enough stresses causes microchipping - glass ceramics silicon hardened steels precious tones

Question 14

What is a Finishing operations how do they affect a design

Answer 14

These are used to improve the surface finish of a
workpiece
Can contribute significantly to production time
and product cost

Question 15

Finishing operations What is Sanding

Answer 15

Uses coated abrasives sand paper emery cloths

Question 16

Construction of sandpaper (diagram)

Answer 16

The grains are electro-statically deposited on backing
material
Coating is made of resin

Question 17

What types of surface can sanding be used on?

Answer 17

Any! Widely used in finishing flat or curved metallic non metallic

Question 18

What is honing (diagram)

Answer 18

stock removal process abrasive stones remove smallamounts of metal

Question 19

What is honing used for

Answer 19

Size and finish bored holes (engine cylinders)
remove errors left by boring
tool marks left by grinding

Question 20

What is lapping? (diagram)

Answer 20

fine abrasive particles embedded in relatively soft material called lap (leather/cloth/cast iron/copper)

Question 21

Shapes and materials used for lapping

Answer 21

Flat cylindrical metal and non metal

Question 22

What is polishing

Answer 22

Produces a smooth, lustrous surface finish - takes time costs alot of money

Question 23

What is an abrasive

Answer 23

Is a small, non-metallic hard particle with sharp

edges and irregular in shape

Question 24

For higher material removal rates what is done

Answer 24

Abrasives are bonded together to form a grinding

wheel

Question 25

What is Vitrification

Answer 25

Used to produce a glassy, amorphous

structure

Question 26

The selection of a grinding process depends

on x4

Answer 26

Part shape Part size Ease of fixing Production rate

Question 27

Limitations of Ultrasonic machining

Answer 27

Each job requires special tooling

Question 28

Purpose of grooves in lapping plate

Answer 28

serve to hold slurries, removing cutting chips and evenly supply slurry to workpiece
uniformly distribute pressure across workpiece - improves flatness accuracy

Question 29

How is polishing done

Answer 29

It is done with disks or belts of fabric or leather coated

with fine powders of aluminium oxide or diamond

Question 30

What is electro-polishing

Answer 30

polishing using electrolysis

Question 31

What is electro-polishing

Answer 31

polishing using electrolysis

Question 32

How is electro-polishing done (diagram)

Answer 32

A DC electric circuit is constructed using the workpiece
as the anode, usually submersed in electrolyte
As current is applied, material is oxidised and then
dissolved by the electrolyte, stripping it from the
surface

Question 33

Order of surface finish highest to lowest; Finish turn, Hone, Rough turn, Grind Semi-finish turn, As cast
or cut

Answer 33

Process/surface finish micrometres/machining cost (%)

As cast or cut/500/0, Rough turn/500-10/20, Semi-finish turn/5-4/70, Finish turn/2/100, Grind/0.8/250, Hone/0.4/400