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Flashcards in Lec 10 Deck (33)
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1

Abrasive machining adv

High dimensional accuracy

2

What is abrasive machining

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

3

Types of bond (grinding wheel)

Clay and Feldspar crystalline material
vitrification used to produce a glassy amorphous structure strong and stiff resistant to oil acid and water

4

Bond too strong (grinding wheel)

Dull grains cannot be dislodged to
allow other sharp grains to perform grinding

5

Bond too weak (grinding wheel)

Grains become dislodged easily,
hence maintaining dimensional accuracy
becomes difficult

6

What is attritious wear (grinding wheel)

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

7

Why are abrasive grains brittle (grinding wheel)

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

8

Why is porosity important (grinding wheel)

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

9

What is grinding?

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

10

Ultrasonic machining (drawing)

removal by micochipping or erosion with fine abrasive grains

11

Ultrasonic machining process

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

12

Tool vibration speed 20kHz or 3000000kHz ultrasonic machining

20kHz

13

Ultrasonic machining best suited for

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

14

What is a Finishing operations how do they affect a design

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

15

Finishing operations What is Sanding

Uses coated abrasives sand paper emery cloths

16

Construction of sandpaper (diagram)

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

17

What types of surface can sanding be used on?

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

18

What is honing (diagram)

stock removal process abrasive stones remove smallamounts of metal

19

What is honing used for

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

20

What is lapping? (diagram)

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

21

Shapes and materials used for lapping

Flat cylindrical metal and non metal

22

What is polishing

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

23

What is an abrasive

Is a small, non-metallic hard particle with sharp
edges and irregular in shape

24

For higher material removal rates what is done

Abrasives are bonded together to form a grinding
wheel

25

What is Vitrification

Used to produce a glassy, amorphous
structure

26

The selection of a grinding process depends
on x4

Part shape Part size Ease of fixing Production rate

27

Limitations of Ultrasonic machining

Each job requires special tooling

28

Purpose of grooves in lapping plate

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

29

How is polishing done

It is done with disks or belts of fabric or leather coated
with fine powders of aluminium oxide or diamond

30

What is electro-polishing

polishing using electrolysis