REGULATION 2017 ACADEMIC YEAR : 2018-2019 ME8451 ... fileCentre lathe, constructional features, specification, operations – taper turning methods, thread cutting methods, special

REGULATION :2017 ACADEMIC YEAR : 2018-2019

JIT-JEPPIAAR/MECH/Dr.D.Muruganandam & Mr.R.Devanathan /IIndYr/SEM 04 /ME8451/MANUFACTURING

TECHNOLOGY II/UNIT 1-5/QB+Keys/Ver1.0

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ME8451 MANUFACTURING TECHNOLOGY – II L T P C

3 0 0 3

OBJECTIVES:

• To understand the concept and basic mechanics of metal cutting, working of standard

machine tools such as lathe, shaping and allied machines, milling, drilling and allied

machines, grinding and allied machines and broaching.

• To understand the basic concepts of Computer Numerical Control (CNC) of machine

tools and CNC Programming

UNIT I THEORY OF METAL CUTTING 9

Mechanics of chip formation, single point cutting tool, forces in machining, Types of chip,

cutting tools– nomenclature, orthogonal metal cutting, thermal aspects, cutting tool materials,

tool wear, tool life, surface finish, cutting fluids and Machinability.

UNIT II TURNING MACHINES 9

Centre lathe, constructional features, specification, operations – taper turning methods, thread

cutting methods, special attachments, machining time and power estimation. Capstan and turret

lathes- tool layout – automatic lathes: semi automatic – single spindle : Swiss type, automatic

screw type – multi spindle:

UNIT III SHAPER, MILLING AND GEAR CUTTING MACHINES 9

Shaper - Types of operations. Drilling ,reaming, boring, Tapping. Milling operations-types of

milling cutter. Gear cutting – forming and generation principle and construction of gear milling

,hobbing and gear shaping processes –finishing of gears.

UNIT IV ABRASIVE PROCESS AND BROACHING 9

Abrasive processes: grinding wheel – specifications and selection, types of grinding process–

cylindrical grinding, surface grinding, centreless grinding and internal grinding- Typical

applications – concepts of surface integrity, broaching machines: broach construction – push,

pull, surface and continuous broaching machines

UNIT V CNC MACHINING 9

Numerical Control (NC) machine tools – CNC types, constructional details, special features,

machining centre, part programming fundamentals CNC – manual part programming –

micromachining – wafer machining.

TOTAL : 45 PERIODS

TEXT BOOKS:

Hajra Choudhury, "Elements of Workshop Technology", Vol.II., Media Promoters 2014 2. Rao.

P.N “Manufacturing Technology - Metal Cutting and Machine Tools", 3 rd Edition, Tata

McGraw-Hill, New Delhi, 2013.

REFERENCES:

1. Richerd R Kibbe, John E. Neely, Roland O. Merges and Warren J.White “Machine Tool

Practices”, Prentice Hall of India, 1998 2. Geofrey Boothroyd, "Fundamentals of Metal

Machining and Machine Tools", Mc Graw Hill, 1984 3. HMT, "Production Technology", Tata

McGraw Hill, 1998. 4. Roy. A.Lindberg, “Process and Materials of Manufacture,” Fourth

Edition, PHI/Pearson Education 2006.




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Subject Code:ME8451 Year/Semester: II /04

Subject Name: MANUFACTURING TECHNOLGY II Subject Handler:

Dr.D.Muruganadam&Mr.R.Devanathan

UNIT I – THEORY OF METAL CUTTING

Mechanics of chip formation, single point cutting tool, forces in machining, Types of chip, cutting tools–

nomenclature, orthogonal metal cutting, thermal aspects, cutting tool materials, tool wear, tool life,

surface finish, cutting fluids and Machinability

PART * A

Q.No. Questions

1.

Write a short note on heat zone in cutting. (Nov.2017) BTL 1

Primary deformation zone - Shear zone. In the primary deformation zone, the heat generation is

due to the plastic work done (plastic deformation) at shear plane. Heat generated by the secondary deformation due to the friction between the rake face and heated chip.

2

Mention any two modern tool materials. (Nov.2017) BTL 1

The following cutting tool materials are used: Tool steels. They are relatively cheap and tough.

cemented carbides. Harder than tool steels, but less tough. cutting ceramic. They are even harder

than cemented carbides but have lower toughness. "super hard materials": cubic boron nitride.

3

Explain the condition that induces the formation of Built up edge. (May 2017) BTL 1

Built up edge is formed as a result of the occurrence of the leading surface shear stress, which

under certain conditions at high pressure adhere the workpiece to the edge. In many times coolant causes formation of BUE so lack of coolant is not always bad thing.

4

How tool life is estimated? (May 2017) BTL 1

This Tool Life Durations calculator addresses two different conditions. For turning and drilling of non-interrupted cuts, enter the cutting time per part in minutes

5

Classify the different types of chip breakers. (Nov.2016) BTL 3

In respect of convenience and safety, closed coil type chips of short length and ... The principles

and methods of chip breaking are generally classified as follows : ... This is accomplished without

using a separate chip-breaker

6

List the various metal removal processes. (Nov.2016) BTL 2

Machining

a) Mills. Grist mill. Hammer mill. Ball mill. Buhrstone mill. Disc mill. Saw mill. Steel mill.

Blast furnace. Smelting. ...

b) Milling.

c) Turning. Lathe. Facing. Boring (also Single pass bore finishing) Spinning (flow turning)

Knurling. Hard turning. Cutoff (parting)

d) Drilling. Friction drilling.

e) Reaming.

f) Countersinking.




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g) Tapping.

h) Sawing. Filing.

7

Discuss how chip formation occurs in metal cutting. (May 2016) BTL 2

The material fails along a short angled plane, from the apex of the tool edge, diagonally upwards

and forwards to the surface. The material deforms along this line, forming an upward curling chip. These chips generally form from intermediate cutting angles. Type II chips may form in

ductile materials, such as metals.

8

Illustrate the various parts in single point cutting tool. (May 2016) BTL 3

9

Point out the various cutting tool materials. (Nov.2015) BTL 1

The main carbide insert and cutting tool coating materials are titanium carbide, titanium nitride,

aluminum oxide, and titanium carbonitride. Ceramic cutting tools are harder and more heat-

resistant than carbides, but more brittle. They are well suited for machining cast iron, hard steels,

and the superalloys.

10 Deduce the factors that contribute to poor surface finish in cutting. (Nov.2015) BTL 1 The first factor that can cause a poor surface finish is that the tool bit is not fastened ... Cutting

speed is 2.50m/s, feed is 0.30mm/rev, and depth of cut is 3.0mm.

11

Explain the advantage of high machinability. (May 2015) BTL 3

The biggest advantage of high speed machining is that due to the increased speed and rate of feed, the material is cut so fast that it barely transfers heat at all. This keeps the turnaround time

down and the emissions of your shop very low compared to historical figures.

12

Summarize machinability index. (May 2015) BTL 5

A numerical value that designates the degree of difficulty or ease with which a particular material

can be machined; originally based on turning B1112 steel at 180 feet per minute (0.9144 meter

per second) with a high-speed tool for an index of 100; with replacement of high-speed steels

with carbides in turning

13

Classify the cutting fluids. (Nov.2014) BTL 3

The most common types of metalcutting fluids can be classified into five groups: straight, or cutting, oils, soluble oils, semi-synthetics or semi-chemical products, and synthetic or chemical products. narration (vo): straight oil cutting fluids are produced from synthetic, vegetable, animal

or mineral oils.




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14

Examine chip thickness ratio. (Nov.2014) BTL 1

The ratio of to to tc is called the chip thickness ratio (or simply the chip ratio) r. {r= to/tc}. The

chip ratio is always less than one. Why the chip thickness after cutting is always greater than the corresponding thickness before cutting

15

What are the assumptions made in drawing Merchant’s circle? (May 2014) BTL 2

Assumptions made in drawing Merchant's circle: Shear surface is a plane extending upwards

from the cutting edge. The tool is perfectly sharp and there is no contact along the clearance force

PART * B

1

Describe the mechanism of metal cutting and process involved in detail. (13 M) (Nov. 2017)

BTL 2

Answer: Page 17– Dr.R.PANNEERDHASS

a) :Diagram

(3M)

b) Principle

(3M)

A wedge-shaped tool with a straight cutting edge is made to move relative to the

workpiece

and a layer of metal called chip is removed. The model of cutting process is shown in Fig.

The chip is formed by a continuous shearing action of workpiece and there is friction

between the flowing chip and face of the tool.

c) Process

(3M)

d) Mechanism

(4M)

a) Tool & Workpiece interaction.




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b) Force. Tool. Workpiece.

c) Tool penetration. (depth of cut).

d) Relative motion between tool and workpiece

2

Explain various cutting tool materials. (13 M) (Nov. 2017) BTL 1


a) Types

(4M)

b) Properties

(6M)

c) Advantages and Disadvantages

(3M)

a) High carbon steel,

b) High speed steel,

c) Non -ferrous cast alloys,

d) Cemented carbides,

e) Ceramics

f) Sintered oxides,

g) Ceremets,

h) Diamond,

i) Cubic boron nitride,

j) UCON and

k) Sialon

3

Give your understanding of the basic metal-cutting process, what are the

important physical and chemical properties of a cutting tool. (15 M) (May 2017) BTL 5

Answer: Page 7, 83– Dr.R.PANNEERDHASS

a) Types

(4M)

b) Properties

(5M)


(4M)

Properties of Cutting tool material

a) Hardness, hot hardness and pressure resistance.

b) Bending strength and toughness.

c) Inner bonding strength.

d) Wear resistance. oxidation resistance.

e) Small prosperity to diffusion and adhesion. abrasion resistance. edge strength




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4

Explain merchant force circle assumptions, diagram and characteristics. (13 M) (May

2016) BTL 5


a) : Diagram

(4M)

b) Principle

(4M)

Assumptions made in drawing Merchant's circle: Shear surface is a plane extending

upwards from the cutting edge. The tool is perfectly sharp and there is no contact along

the clearance force. The depth of cut remains constant.

(3M)


(2M)

5

Explain the basic actions, characteristics and properties of cutting fluids. (13 M) (Nov. 2016)

BTL 4


a) Types

(4M)

b) Properties

(5M)


(4M)

The Four Main Types of Cutting Fluids and their Properties

a) Straight oils. These oils are non-emulsifiable and very useful in machining




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operations where they function in undiluted form.

b) Synthetic fluids. They do not contain mineral oil base or petroleum.

c) Soluble oils. Soluble Oils usually form an emulsion after mixing them with water.

d) Semi-synthetic fluids.

6

Explain the standard angles of cutting. Illustrate with an example. (13 M) (Nov. 2016) BTL 4


a) :Diagram

(5M)

b) Terminology

(5M)

c) Construction

(3M)

7

Describe the expression for the shear angle in Orthogonal metal cutting. (13 M)

(May 2015)BTL 4





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a) :Diagram

(3M)

b) Expression

(5M)

c) Explanation

(5M)

8

In an orthogonal cutting operation on a work piece of width

2.5mm, the uncut chip thickness was 0.25mm and degree.

It was observed that the chip thickness was 1.25mm.The cutting force was measured

to be 900N and the thrust force was found to be 810 N.

(a) Find the shear angle.

(b) If the coefficient of friction between the chip and the tool, was 0.5,

what is the machining constant Cm (13 M) (May 2015) BTL 6


a) Diagram

(3M)

b) Given data

(2M)

c) Shear angle

(4M)

d) Machining constant

(4M)

9




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Difference between orthogonal cutting and oblique cuttinh. (13 M) (Nov. 2015) BTL 1


a) Diagram

(4M)

b) Principle

(4M)

c) Properties

(3M)

d) Advantages and Disadvantages

(2M)

10

A turning tool with side and end cutting edge of 20 degree and 30 degree respectively

operates at a speed of 0.2 mm/rev. Calculate the CLA of the surface produced if the tool

force radius is 3 mm. (13 M) (Nov. 2015) BTL 6


a) Given data

(2M)

b) Depth of cut

(4M)

c) CLA

(7M)




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PART * C

1

List the various tool materials used in industry. State the optimum temperature of each of

the tool materials. (13 M) (May 2016) BTL 1

Answer: Page 52 – Dr.R.PANNEERDHASS

1. High Carbon Steel tools

• Its composition is C = 0.8 to 1.3%, Si = 0.1 to 0.4% and Mn = 0.1 to 0.4%.

• It is used for machining soft metals like free cutting steels and brass and used as chisels

etc.

• These tool loose hardness above 250°C.

(2 M)

2. High speed steel (H.S.S)

H.S.S is used for drills, milling cutters, single point cutting tools, dies, reamers etc.

• It looses hardness above 600°C.

• Some times tungsten is completely replaced by Molybdenum.

• Molybdenum based H.S.S is cheaper than Tungsten based H.S.S and also slightly greater

toughness but less water resistance.

(2 M)

3. Non – ferrous cast alloys

It can not heat treated and are used as cast form.

• It looses its hardness above 800°C

• It will give better tool life than H.S.S and can be used at slightly higher cutting speeds.

• They are weak in tension and like all cast materials tend to shatter when subjected to

shock load or when not properly supported.

(2 M)

4. Cemented carbides

• Produced by powder metallurgy technique with sintering at 1000°C.

• Speed can be used 6 to 8 times that of H.S.S.

• Can withstand up to 1000°C.

(2 M)

5. Ceramics and sintered oxides

• Ceramics and sintered oxides are basically made of Al2O3, These are made by powder

metallurgy technique.

• Used for very high speed (500m/min).

• Used for continuous cutting only.

• Can withstand upto 1200°C..

(2 M)

6. Diamond

• Can withstand above 1500°C.

• A synthetic (man made) diamond with polycrystalline structure is recently introduced and

made by powder metallurgy process.

(2 M)

7. Cubic Boron Nitride (CBN)

• The trade name is Borozone.

https://me-mechanicalengineering.com/reamer/

https://me-mechanicalengineering.com/ceramics/




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• Consists of atoms of Nitrogen and Boron and produced by power metallurgy process.

• Used as a substitute for diamond during machining of steel.

• Used as a grinding wheel on H.S.S tools.

• Excellent surface finish is obtained.

(2 M)

8. Sialon (Si-Al-O-N)

• Sialon is made by powder metallurgy with milled powders of Silicon, Nitrogen,

Aluminium and oxygen by sintering at 1800°C

(1 M)

2

Maximum temperature in orthogonal cutting is located at about the middle of the tool-chip

interface - Evaluate (15 M) (May 2016) BTL 5


a) Diagram

(4M)

b) Principle

(7M)

c) Aspects

(5M)

3

Describe in detail your thoughts regarding the technical and economic factors involved in

tool material selection. (15 M) (May 2015) BTL 6


a) Principle

(4M)

b) Types

(4M)




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c) Construction

(3M)


(4M)

Material selection in engineering design process is very important to ensure that the There are

number of other considerations in the materials selection process. This is also very important

factor to consider when selecting a material for a of Data Tables in Engineering · Precision

Turning & Tool Making in Demand.


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UNIT II – TURNING MACHINES

Centre lathe, constructional features, specification, operations – taper turning methods, thread cutting

methods, special attachments, machining time and power estimation. Capstan and turret lathes- tool

layout – automatic lathes: semiautomatic – single spindle : Swiss type, automatic screw type – multi

spindle

PART * A

Q.No. Questions

1.

List out the factors to be considered while specifying a lathe. (May2017) BTL 1

a) Swing the largest work diameter that can be swung over the lathe bed.

b) The shape of bed ways and horse power of the driving motor sometimes taken into

specifications.

c) Distance between head stock and tail stock center.

d) Some manufacturers designate the lathes by the swing and length of the bed.

2

Explain the meaning of “swing of the lathe". (May2017) BTL 4

The largest diameter of work that can be carried between the centers of a lathe. In England, the

swing refers to radius.

3 Discuss the difference between feed rod and lead screw. (Nov. 2016) BTL 2

The lead screw is used for threading, the feed rod is for general machining. The feed rod runs much

slower than the lead screw for finer feeds.

4 Define the term “Conicity”. (Nov. 2016) BTL 1

The amount of taper in work piece is usually specified by the ratio of the difference in diameters of the

taper to its length.

5

Express the formula for calculating taper turning angle by tailstock set over distance and

compound rest method. (May2016)BTL 2

6

Describe the term “Thread cutting”. (May2016) BTL 2 Screw threads are cut with the lathe for accuracy and for versatility. Both inch and metric screw threads

can be cut using the lathe. A thread is a uniform helical groove cut inside of a cylindrical workpiece, or

on the outside of a tube or shaft.

7 Explain, how the number of teeth on various change gears calculated. (Nov. 2015) BTL 5


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The ratio is determined by the number of teeth on each gear wheel. Calculate the speed ratio of

two gears by dividing the angular velocity of the output gear (represented numerically by the

number of teeth) by the angular velocity of the input gear (represented numerically by the number of

teeth).

8 Define automatic machine. (Nov. 2015) BTL 1

A machine or machine tool (such as a spinning machine or lathe) that after once being set operates

automatically except for applying the power, lubricating, supplying material, and shutting off the power.

9

List the types of taper turning method? (May2015) BTL 3

a) Compound rest method

b) Tailstock setover method

c) Special attachment method

d) Form tool

10

Compare the advantages of turret lathe over capstan lathe. (May2015) BTL 4

11

Explain the term "copy turning". (Nov.2014) BTL 4

Copy turning is carried out on special lathes that control the cutting tool in some manner to produce

identical items. The copy lathe uses a template to guide the cutter. They are capable of creating good

quality components for little expense in patterns and setting up. Sanding is usually carried out by hand.

12 Differentiate automatic lathe and capstan lathe.BTL 2


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13

Discover the four major parts of Swiss type automatic lathes. (Nov.2014)BTL 3

a) Cam

b) Cam shaft c) Headstock d) Tool layout

14

Discuss the purpose of providing lead cam in single spindle automatic screw cutting

machine. (May 2014)BTL 3 An automatic lathe is a lathe (usually a metalworking lathe) whose actions are controlled

automatically. Although all electronically controlled (CNC) lathes are automatic, they are . Small- to

medium-sized cam-operated automatic lathes were (and still are) usually called screw machines or

automatic screw machines.

15

Tabulate the difference between parallel action and progressive action multi spindle

automatic lathes. (May 2014)BTL 1

PART * B


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1

Explain taper turning operation in a lathe by taper turning attachment method. (13 M)

(Nov. 2017) BTL 4


a) Diagram

(4M)

b) Types

(4M)

c) Construction

(3M)

d) Properties

(2M)

2

Explain the construction and working principle of a lathe with a neat sketch. (13 M) (Nov.

2017) BTL 5


a) Diagram

(4M)

b) Principle


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(4M)

c) Construction

(3M)

1) Lathe bed

2) Tailstock

3) Headstock

4) Carriage


(2M)

3

What are the different types of machining operations that can be performed on a lathe?

Explain any four in detail. (13 M) (May2017) BTL 4


a) Diagram

(4M)

b) Types

(4M)

c) Construction

(3M)

d) Properties

(2M)

Various Types of Operations Performed in Lathe Machine

• Facing.

• Turning. Straight turning. Step turning.

• Chamfering.

• Grooving.


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• Forming.

• Knurling.

• Undercutting.

• Eccentric turning.

4

Explain the thread cutting operation in a lathe with a neat sketch. Also make a note on

knurling, grooving and forming operations in a lathe. (13 M) (May2017) BTL 5

Answer: Page 141,145– Dr.R.PANNEERDHASS

a) Diagram

(4M)

b) Principle

(4M)

c) Process

(3M)

d) Application

(2M)


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5

Discuss about the Geneva mechanism of turret lathe with neat sketch. (13 M) (Nov. 2016)

BTL 2


a) Diagram

(4M)

b) Principle

(4M)

c) Construction

(3M)

d) Applications

(2M)

6

Discuss the features of Ram type and Saddle type turret with neat sketches. (13 M)

(Nov. 2016) BTL 2


a) Diagram

(4M)

b) Types

(4M)

c) Construction

(3M)

d) Properties

(2M)


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7

Explain the tooling layout for the producing of a Hexagonal bolt in a Capstan lathe. (13 M)

(May2016) BTL 5


a) Diagram

(4M)

b) Types

(4M)

c) Construction

(3M)

d) Properties

(2M)


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8

Classify transfer machines. Sketch and explain the working of Swiss type automatic screw

machine. What are the advantages of automatic machines? (13 M) (May2016) BTL 3


a) Diagram

(4M)

b) Types

(4M)

c) Construction

(3M)

d) Properties

(2M)


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9

Differentiate between parallel action and progressive action multi spindle

automatics. (13 M) (Nov. 2015)BTL 4


a) Diagram

(4M)

b) Types

(4M)

c) Construction

(3M)

d) Properties

(2M)


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10

Explain the classification of automatic lathes. (13 M) (Nov. 2015) BTL 3


a) Diagram

(4M)

b) Types

(4M)

c) Construction

(3M)

d) Properties

(2M)

PART * C


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1

A badly oxidized and uneven round bar is being turned on a lathe. Would you recommend

a small or in large depth of cut? Explain. (15 M) (Nov. 2016)BTL 6

Answer: Page 111– CLASS NOTES

a) Diagram

(4M)

b) Types

(4M)

c) Construction

(4M)

d) Properties

(3M)

A highly oxidized and uneven round bar is being turned on a lathe. relatively small or

large depth of cut and (b) continuous chips would entangle on spindles and machine

components

2

Describe the problems, if any, that may be encountered in clamping a work piece

made of a soft metal in a three-jaw chuck. (15 M) (May 2016)BTL 2


a) Diagram

(4M)

b) Types

(4M)

c) Construction

(4M)

d) Properties

(3M)


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A common problem in clamping any workpiece into a chuck is that the jaws will bite into

the workpiece , possibly leaving an impression that may be unsightly or functionally

unacceptable. Shim stock, made of a softer material, can be used between the jaws and the

workpiece to minimize damage to the workpiece surface. Parts may also be designed for

convenient clamping into chucks, or provided with flanges or extensions which can be

gripped by the chuck, which can later be removed.

3

We have seen that cutting speed, feed, and depth of cut are the main parameters in a

turning operation. In relative terms, at what values should theses parameters be set for a

(a) roughing operation and (b) finishing operation? (15 M) (Nov. 2015) BTL 6


a) Diagram

(4M)

b) Types

(4M)

c) Construction

(4M)

d) Properties

(3M)

For a finishing operation, with good surface finish, they should be set at high speed,

low feed, and low depth of cut. (b) For a roughing operation, where surface finish is not as

important, they should be set at low speed and high feed and depth of cut. where surface

finish is critical, feed and depth of cut should be low. Speed does not appear in this equation;

the main effect of speed is to generate chatter at higher speeds. This, when surface finish is

not critical, speed can be set high. When surface finish is critical, it is important to avoid

chatter.


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UNIT III– SHAPER, MILLING AND GEAR CUTTING MACHINES

Shaper – Types of operations. Drilling ,reaming, boring, Tapping. Milling operations-types of milling

cutter. Gear cutting – forming and generation principle and construction of gear milling, hobbing and

gear shaping processes –finishing of gears..

PART * A

Q.No. Questions

1.

Briefly describe the importance of quill mechanism. (Nov. 2017) BTL 1

Quill drive is a mechanism that allows a drive shaft to shift its position (either axially, radially,

or both) relative to its driving shaft. It consists of a hollow driving shaft (the quill) with a driven

shaft inside it. The two are connected in some fashion which permits the required motion.

2

Define the cutting speed, feed and machining time for drilling. (Nov. 2017) BTL 1 Feed is speed of tool moving on the surface perpendicular to the direction of cut. This gives a

measure of how much surface the tool covers per unit time while cutting. Depth of cut is volume

of material removed per unit time by the cutting tool.

3

What is the difference between up milling and down milling? (May 2017) BTL 2

down milling, while cutting the workpiece from right to left cutter rotates in clockwise direction.

The material from the surface or cutting chips are thrown in the upward direction that's why it is

called as up milling. Up milling is mostly used for rough cutting operations.

4

Write the differences between drilling and tapping. (May 2017) BTL 3

Drilling is the operation of producing cylindrical hole in a work piece. It is done by rotating the

Cutting edge of a cutter known as drill. The work is rotated at high speed. Tapping is the process used for making internal threads in a machine component by a tool called

“TAP”

5

What is a shell mill? (Nov. 2016) BTL 4

A shell mill is any of various milling cutters (typically a face mill or endmill) whose construction takes a modular form, with the shank (arbor) made separately from the body of the

cutter, which is called a "shell" and attaches to the shank/arbor via any of several standardized

joining methods.

6

Sketch the various elements of a plain milling cutter with a neat sketch. (Nov. 2016) BTL 4




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7

What do you know about straight fluted drill and fluted drill? (May 2016) BTL 3

Straight fluted bit. Straight fluted drill bits do not have a helical twist like twist drill bits do.

They are used when drilling copper or brass because they have less of a tendency to "dig in" or

grab the material.

8

How do you classify milling cutters? (May 2016) BTL 2

Milling operations may be classified under four general heading as follows:

a) Face Milling, machining flat surfaces which are at right angle to the axis of the cutter.

b) Plain or Snab Milling, machining flat surfaces which are parallel to the axis of the cutter. c) Angular Milling, machining flat surfaces which are at an inclination to the axis of the

cutter.

d) Form Milling, machining surfaces having an irregular outline.

9 List out the gear finishing processes. (Nov. 2015) BTL 4

Several finishing operations are available, including the conventional process of shaving, and a

number of abrasive operations, including grinding, honing, and lapping

10

Mention the differences between shaper and planer. (Nov. 2015) BTL 1

The main difference between these two processes is that in shaping the tool reciprocates across the stationary workpiece. Planing motion is the opposite of shaping. Both planing and shaping

are rapidly being replaced by milling. The mechanism used for this process is known as a planer.

11

State the differences between a vertical shaper and slotters. (May 2015) BTL 3

It may be considered as a vertical shaper. The chief difference between a shaper and a slotter is the direction of the cutting action. The machine operates in a manner similar to the shaper,

however, the tool moves vertically rather than in a horizontal direction. The job is held

stationary.

12

Why is sawing a commonly used process. (May 2015) BTL 2 The blade itself remains relatively cool because during its operating cycle it is in contact with

hot metal for only a short time. Circular sawing uses a rotating saw blade to provide a

continuous motion of the tool past the work. Circular sawing is often used to cut long bars and

tubes to specific lengths.

13

Sketch a twist drill. (Nov. 2014) BTL 3

https://en.wikipedia.org/wiki/Grinding_(abrasive_cutting)

https://en.wikipedia.org/wiki/Honing_(metalworking)

https://en.wikipedia.org/wiki/Lapping




3- 29

14

Make a note on different types of work holding devices used in a slotting machine. (Nov.

2014) BTL 6

Different work holding devices are used according to the shape, length, diameter ... The three

jaws fitted in the three slots may be made to slide at the same time by an ... Hence this type of

chuck can hold woks of irregular shapes. ... when the workpiece fitted with the carrier fits into

the slot of the catch plate.

15

Give the two principal methods of gear manufacturing. (May 2015) BTL 4 The most common gear-cutting processes include hobbing, broaching, milling, and grinding.

Such cutting operations may occur either after or instead of forming processes such as forging,

extruding, investment casting, or sand casting. Gears are commonly made from metal, plastic,

and wood.

PART * B

1

Explain various milling cutters with neat sketches? (13 M)(Nov. 2017) BTL 2


Types of milling cutters

Many different kinds of milling cutters are used in milling machines. They are:

Slab or plain milling cutter

Plain milling cutters are hollow straight HSS cylinder of 40 to 80 mm outer diameter having 4 to

16 straight or helical equi-spaced flutes or cutting edges horizontal arbor to machine flat surface

milling cutters are termed as slab milling cutters.

Side milling cutters

These arbor mounted disc type cutters have a large number of cutting teeth at equal spacing on

the periphery. Each tooth has a peripheral cutting edge and another cutting edge on one face in

single side cutter and two more cutting edges on both the faces leading to double sided cutter.

One sided cutters are used to produce one flat surface or steps comprising two flat surfaces at

right angle sided cutters are used for making rectangular side milling cutter.

(4 M)

Slitting saws or parting tools

These milling cutters are very similar to the slotting cutters having only one peripheral cutting

edge on each tooth.

(1 M)

(3 M)




3- 30

(3 M)

End milling cutter:

• Mostly made of High Speed steel

• 4 to 12 straight or helical teeth on the periphery and face.

• Diameter ranges from about 1 mm to 40 mm

• Very versatile and widely used in vertical spindle type milling machines

(2 M)

2

Discuss various hole making processes. (13 M) (Nov. 2017) BTL 2


HOLE MAKING

Machining round holes in metal stock is one of the most common operations in the manufacturing

industry. It is estimated that of all the machining operations carried out, there are about 20 % hole

making operations. Literally no work piece leaves the machine shop without having a hole made

in it.

The various types of holes are shown in Fig.

(4 M)

(5 M)

Description




3- 31

(4 M)

3

Discuss boring and reaming operation with neat sketches. (13 M) (May 2017)BTL 3

Answer: Page 257 & 258 – Dr.R.PANNEERDHASS

BORING

Boring is an operation of enlarging and locating previously drilled holes with a single point

cutting tool. The machine used for this purpose is called the most versatile machine tools used to

bore holes in large engine cylinders, machine housings this machine. Screw cutting. Turning,

planetary grinding and gear cutting operations also can be done by fitting simple attachments.

The principle of boring operation is illustrated in Fig.

(3 M)

(4 M)

REAMING

Reaming is an operation of finishing a hole previously drilled to give a good surface finish and an

accurate dimension. A reamer is a multi tooth cutter which rotates and moves axially into the

hole.

The reamer removes relatively small amount of material. Generally the reamer follows the

already existing hole and therefore will not be able to correct the hole misalignment. Fig.

illustrates the elements of a reamer.

(3 M)




3- 32

(3 M)

4

Describe the working of a crank and slotted link mechanism. (13 M) (May 2017)BTL 4


THE CRANK AND SLOTTED LINK MECHANISM:

(7 M)

This mechanism has a bull gear mounted within the column. The motion or power is transmitted

to the bull gear through a pinion which receives its motion from an individual motor.

This radial slide carries the bull gear will cause the crank pin to revolve at a constant speed

Rocker arm sliding block is mounted up to arm sliding block is fitted within the slotted link and

arm). The bottom end of the rocker arm and connected to the ram block by a pin which can slide

in the forked end.

As the bull gear rotates causing the crank pin to rotate, the rocker arm sliding block fastened to

the crank pin will rotate on the crank pin circle, and at the provided in the slotted link. This up

and down movement to the slotted link (rocker arm), which is converted into reciprocating

movement of the ram.

The work piece is clamped directly on the by rotating the lead screw.

A radial slide is a bull gear sliding block into which the crank pin is fitted. about the upon the

crank pin and is free to rotate about the pin. The rocker can slide along the slot in the is pivoted to

the frame of the column.

Thus the rotary motion of the bull gear converted in to reciprocating motion of ram.

(6 M)

5

What are the operations performed on a drilling machine? (13 M) (May 2016) BTL 4


The wide range of applications of drilling machines includes:

Drilling machines are generally or mainly used to originate through or blind straight cylindrical

holes in solid rigid bodies and/or enlarge (coaxially) existing holes:

• Of different diameters up to 40 mm.




3- 33

• Of varying length depending upon the requirement and the diameter of the drill.

• In different materials excepting very hard or very soft materials like rubber, polythene etc

• Originating stepped cylindrical holes of different diameter and depth.

• Making rectangular section slots by using slot drills having 3 or 4 flutes and 1800 cone

angle.

• Boring, after drilling, for accuracy and finish or prior to reaming

• Counter boring, countersinking, chamfering or combination using suitable tools.

• Spot facing by flat end tools.

• Trepanning for making large through holes and or getting cylindrical solid core.

(7 M)

(6 M)

6

Explain different types of milling cutters. (13 M) (May 2016)BTL 5


Same as 1.

7

Explain the tooling layout for the producing of a Hexagonal bolt in a Capstan lathe. (13 M)




3- 34

(Nov. 2015)BTL 5


Selection of machine tool

Blank selection

(4 M)

Machining operations

• Facing

• Centering

• Chamfering (1) – front

• Chamfering (2) – mid

• Rough turning (1) – to make circular from hexagon

• Rough turning (2) – to reduce diameter to 12 mm

• Finish turning – to φ10

• Drilling

• Grooving (forming)

• Thread cutting

• Initial parting

• Parting

Combining elementary operations

(3 M)

(6 M)

8




3- 35

With the help of a neat sketch, discuss the Tapping and Gear hobbing operation. (13 M)

(Nov. 2015)BTL 5


TAPPING:

Tapping is the faster way of producing internal threads. A tap is a multi fluted cutting tool with

cutting edges on each blade resembling the shape of threads to be cut. A tap is used after carrying

out the pre drilling operation corresponding to the required size.

(3 M)

(4M)

Gear hobbing is a machining process in which gear teeth are progressively generated by a series

of cuts with a helical cutting tool (hob). The gear hob is a formed tooth milling cutter with helical

teeth arranged like the thread on a screw. These teeth are fluted to produce the required cutting

edges. All motions in hobbing are rotary, and the hob and gear blank rotate continuously as in

two gears meshing until all teeth are cut. This process eliminates the unproductive return motion

of the gear shaping operation. The work piece is mounted on a vertical axis and rotates about its

axis.

The hob is mounted on an inclined axis whose inclination is equal to the helix angle of the hob.

The hob is rotated in synchronization with the rotation of the blank and is slowly moved into the

gear blank till the required tooth depth is reached in a plane above the gear blank. The tool-work

configuration and motions in hobbing are shown in Fig.

(3 M)




3- 36

( 3 M)

9

Sketch the Quill mechanism .Write its main parts and their functions? (13 M) (May 2015)BTL 6


The spindle is a vertical shaft which holds the drill. It receives its motion from the top shaft

though bevel gears.

The sleeve may be moved up or down by rotating a pinion which meshes with the rack and this

movement is imparted to the spindle. The downward movement of the spindle is effected by

rotating the pinion which causes the quill to move downward exerting pressure on the spindle

through a thrust bearing and washer. The spindle is moved upward by the upward pressure

exerted by the quill acting against a nut through the thrust bearing. The lower end of the spindle is

provided with Morse taper hole for accommodating taper shank drill.

The hole drill tool used in the deep hole drilling operation is shown in Fig.

(6 M)




3- 37

10

How will you cut the following types of surfaces on milling machines? (13 M) (May 2015)

(a) Flat surfaces (b)Slots and splines BTL 5

Answer: Page 305 & 307– Dr.R.PANNEERDHASS

(a) Flat surfaces: It will be cut by plain milling, face milling, end milling and straddle milling.

(2 M)

(4 M)

(b) Slots and splines:

Cutting the slots of various sections and slots of external spline shafts are shown in Fig.

(2 M)




3- 38

(5 M)

PART * C

1

Explain the different types of table drive and feed mechanisms in a planning machine. (15

M) (May 2016)BTL 5


Open and cross belt drive mechanism:

In this mechanism the movement of the table is effect by an open belt and a cross belt drive. It is

an old method of quick return drive used in planers of smaller size where the table width is less

than 900 mm.

(5 M)

(5 M)




3- 39

Reversible motor drive quick return mechanism

All modern planers are equipped with variable speed electric motor which drives the bull gear

through a gear train. The most efficient method of an electrical drive is based on Ward Leonard

system.

(5 M)

2

Explain different types of drilling machines with their special features? (15 M) (May

2015)BTL 6


Types of drilling machine

The different types of drilling machine which are most commonly used are:

• Portable drilling machine.

• Sensitive drilling machine

• Upright drilling machine

• Radial drilling machine

• Gang drilling machine.

• Multiple spindle drilling machine.

• Deep hole drilling machine.

• Turret type drilling machine

(10 M)

Description of features:

(5 M)

3

Write short notes on expanding hand reamers and adjustable machine reamers. (15 M)

(May 2014)BTL 6


REAMING

Reaming is an operation of finishing a hole previously drilled to give a good surface finish and an

accurate dimension. A reamer is a multi tooth cutter which rotates and moves axially into the

hole.




3- 40

The reamer removes relatively small amount of material. Generally the reamer follows the

already existing hole and therefore will not be able to correct the hole misalignment.

(4 M)

There are hand reamers and machine reamers. They mainly differ with respect to the shank (hand

reamer: square, machine reamer: taper) and to the cutting portion (machine reamers have a shorter

lead).

Hand reamers are primarily used for assembly work to make parts fit better. Their main feature is

a long taper lead. This ensures good guidance in the hole and prevents canting. The reamer is

inserted into the hole by means of the milled square and a tap wrench with clockwise rotation and

slight pressure.

Machine reamers used on lathes are: non-adjustable reamers, arbor-mounted reamers, adjustable

reamers, spiral-fluted reamers and taper reamers.

(5 M)

(6 M)




3- 41


Subject Name: MANUFACTURING TECHNOLOGY II Subject Handler:


UNIT IV– ABRASIVE PROCESS AND BROACHING

Abrasive processes: grinding wheel – specifications and selection, types of grinding process– cylindrical

grinding, surface grinding, centreless grinding and internal grinding- Typical applications – concepts of

surface integrity, broaching machines: broach construction – push, pull, surface and continuous

broaching machines

PART * A

Q.No. Questions

1.

How does loading differ from glazing in grinding process? (Nov.2017) BTL 1 Glazing. It is the condition of the grinding wheel in which the cutting edges or the face of Loading. The wheel is loaded if the particles of the metal being ground adhere to the wheel.

2

Why most abrasives are now made synthetically? (Nov.2017) BTL 1

Many synthetic abrasives are effectively identical to a natural mineral, differing only in that the

synthetic mineral has been manufactured rather than mined. Impurities in the natural mineral may

make it less effective. ... Emery (impure corundum) Diamond dust (synthetic diamonds are used

extensively)

3

What is an abrasive? What are super abrasives? (May 2017) BTL 1

Abrasives that belong to the Superabrasive family includes,Industrial diamonds: an industrial diamond is a non-gem quality small diamond that is for abrasives, cutting, and drilling tools. Cubic boron nitride (CBN): Usually called CBN it is the second hardest cutting tool material after a diamond.

4

Define hardness of the grinding wheel. (May 2017) BTL 2

Hardness. The hardness of a grinding disc is the resistance that the binding of the disc exerts

against grain shedding. The bond hardness of a cutting-off wheel or grinding disc can be

influenced and adjusted by the resin used as well as by the added filler materials.

5

Define lapping. (Nov.2016) BTL 2 Lapping is a machining process in which two surfaces are rubbed together with an abrasive

between them, by hand movement or using a machine. ... This produces microscopic conchoidal

fractures as the abrasive rolls about between the two surfaces and removes material from both. .

6

How will you express “grade” and “structure” of a grinding wheel? (Nov.2016) BTL 2

Grain Size, Grade and Structure of Grinding Wheel

a) Grain Size (Grit) The grinding wheel is made up of thousands of abrasive grains. ...

b) Grade. The grade of a grinding wheel refers to the hardness with which the wheel holds

the abrasive grains in place. ...

c) Structure. The relative spacing occupied by the abrasives and the bond is referred to as




3- 42

structure.

7

Give four important factors that influence the selection of grinding wheel. (May 2016) BTL 3

Selection of abrasive tool characteristics to grinding...

a) Worked material. Type and condition.

b) Type and nature of grinding operation.

c) Operating speed of grinding wheel.

d) Contact area between the grinding wheel and ground material.

e) Difficulty rate of grinding operation.

f) Grinding machine power.

g) Approximate relationship between surface roughness and grain size.

8

Discuss the need of truing and dressing operations in a grinding wheel. (May 2016) BTL 3

Dressing sharpens the wheel by removing bond material and fracturing the superabrasive grit to

expose fresh edges, so dressing always follows truing. A superabrasive grinding wheel is largely

self-sharpening, although the workpiece material can cause it to dull or load-up.

9

Point out the abrasives used in manufacture of grinding wheels. (Nov.2015) BTL 3 The manufactured abrasives most commonly used in grinding wheels are aluminum oxide, silicon

carbide, cubic boron nitride, and diamond. ... They are used for grinding most steels and other

ferrous alloys. They are used for grinding most steels and other ferrous alloys.

10 Classify the types of external grinders. (Nov.2015) BTL 4 A disc type grinding wheel performs the grinding action with its peripheral surface. Both traverse .This machine is used to produce external cylindrical surface.

11

Discuss the operations done in centreless grinders. (May 2015) BTL 4 Centerless grinding is a machining process that uses abrasive cutting to remove material from a

workpiece. Centerless grinding is typically used in preference to other grinding processes for operations where many parts must be processed in a short time.

12

Explain the work holding and supporting devices used in grinders. (May 2015) BTL 3

Describe methods of holding odd-shaped, nonmagnetic, and thin workpieces. Magnetic Chucks.

The most common work-holding device for the surface grinder is the magnetic .Permanent-

magnet chuck, the most widely used surface grinding chuck.The work is supported on laminated magnetic parallels.

13

Explain why the centreless grinders are called specialized machines for Cylindrical parts?

(Nov.2014) BTL 4 Centerless grinding is a machining process that uses abrasive cutting to remove material from

One wheel, known as the grinding wheel (stationary wheel in the diagram), is on a however, it can only be used for parts with a simple cylindrical shape. Centerless grinding uses purpose-built centerless grinding machines.

14

What is the principle of a broaching process? (Nov.2014) BTL 5 Broaching is a machining process that pushes or pulls a cutting tool (called a broach) over or

through the surface being machined. Its high-production, metal-removal process is sometimes

required to make one-of-a-kind parts.

15 Discuss surface integrity. (May 2015) BTL4




3- 43

Surface integrity is the surface condition of a workpiece after being modified by a manufacturing

process.The surface integrity of a workpiece or item changes the material's properties.

PART * B

1

Explain the working mechanism of cylindrical and surface grinding. (13 M) (Nov. 2017) BTL 4

Answer: Page 369, 377 – Dr.R.PANNEERDHASS

(5 M)

CYLINDRICAL GRINDING PROCESS

It is used generally for producing external cylindrical surfaces. The machine is very similar to a

centre lathe. The grinding wheel is located similar to the tool post with an independent power and

is driven at a high speed suitable for the grinding operation. There are four movements in a

cylindrical grinding process.

i. Rotation of cylindrical work piece about its axis.

ii. Rotation of grinding wheel about its axis.

iii. Longitudinal feed movement of the work past the wheel face.

iv. Movement of wheel into the work perpendicular to the axis of the work to give depth of cut.

SURFACE GRINDING

Surface grinding machines are generally used for generating flat surfaces. These machines are

similar to milling machines in construction as well as motion. There are basically four types of

machines depending upon the spindle direction and the table motion. They are,

1. Horizontal spindle and rotating table grinding machine.

2. Vertical spindle and rotating table grinding machine.

3. Horizontal spindle and reciprocating table grinding machine, and

4. Vertical spindle and reciprocating table grinding machine.




3- 44

(8 M)

2

What do you understand by grinding as an abrasive process? Explain with a neat sketch. (13 M) (Nov. 2017) BTL 2


ABRASIVE PROCESSES: GRINDING

Grinding is the most common form of abrasive machining. The art of grinding goes back many

centuries. Over 5000 years ago the Egyptians abraded and polished building stones to hairline fits

for the pyramids. Grinding is a metal cutting process which engages an abrasive tool whose

cutting elements are grains of abrasive material known as grit. These grits are characterized by

sharp cutting points, high hot hardness, wear resistance and chemical stability. The grits are held

together by a suitable bonding material to give shape of an abrasive tool. Simply it is a metal

removal process in which the metal is removed with the help of rotating grinding wheel. Fig.

illustrates the cutting action of abrasive grits of disc type grinding wheel similar to cutting action

of teeth of the cutter in slab milling.

(8 M)

(5 M)

3

Explain the working principle and various methods of centreless grinding with a neat

sketch. (13 M) (May 2017) BTL 3


Centreless external grinding machine

This grinding machine [shown in Fig.] is a production machine in which outside diameter of the

work piece is ground. The work piece is not held between centres but by a work support blade. It

is rotated by means of a regulating wheel and ground by the grinding wheel. In through-feed

centreless grinding, the regulating wheel revolving at a much lower surface speed than grinding

wheel controls the rotation and longitudinal motion of the work piece. The regulating wheel is

kept slightly inclined to the axis of the grinding wheel and the work piece is fed longitudinally as

shown in Fig.

(8 M)




3- 45

(5 M)

4

Explain why there are so many different types and sizes of grinding wheels? (13 M) (May

2017) BTL 3


GRINDING WHEELS

Grinding wheel consists of hard abrasive grains called grits, which perform the cutting or material

removal, held in the weak bonding matrix. A grinding wheel commonly identified by the type of

the abrasive material used. The conventional wheels include Aluminium Oxide (Al2O3) and

Silicon Carbide (SiC) wheels while diamond and CBN (Cubic Boron Nitride) wheels fall in the

category of super abrasive wheel. Thus, it forms a multi-edge cutter.

(4 M)

Grinding wheel and work piece interaction

The bulk grinding wheel-work piece interaction can be divided into the following:

Grit-work piece (forming chip).

2. Chip-bond.

3. Chip-work piece.

4. Bond-work piece.

Except the grit-work piece interaction which is expected to produce chip, the remaining three

undesirably increases the total grinding force and power requirement. Therefore, efforts should

always be made to maximize grit-work piece interaction leading to chip formation and to

minimize the rest for best utilization of the available power.

The importance of the grit shape can be easily realized because it determines the grit geometry

e.g. rake and clearance angle as illustrated in Fig. It appears that the grits do not have definite

geometry unlike a cutting tool and the grit rake angle may vary from +450 to -600 or more

(4 M)




3- 46

(5M)

5

Explain the factors to be considered to select a grinding wheel and recommended

parameters. (13 M) (Nov. 2016) BTL 5


SELECTION OF GRINDING WHEEL

Selection of a proper grinding wheel is very important for getting the best results in grinding

work. The selection will depend upon the following factors:

(1 M)

1. Constant factors

a. Physical and chemical properties of material to be ground. b. Area of contact.

c. Amount and rate of stock to be removed. d. Types of grinding machine.

(2 M)

2. Variable factors

a. Work speed. b. Wheel speed. c. Condition of the grinding machine.

d. Personal factor. e. Type of grinding (stock removal grinding or form finish grinding).

(2 M)

Types of abrasives

Abrasives may be classified into two types:

1. Natural abrasives - Emery (50 - 60 % crystalline Al2O3 + Iron Oxide), Sandstone or Solid

Quartz,

Corundum (75 - 90 % crystalline Al2O3 + Iron Oxide) and Diamond.

2. Artificial abrasives - Aluminium Oxide (Al2O3), Silicon Carbide (SiC), Artificial diamond,

Boron Carbide and Cubic Boron Nitride (CBN).

(2 M)

Grit size or grain size

It refers to the actual size of the abrasive particles. The grain size is denoted by the number.

Table 4.1 shows the different types of grit or grain sizes and their corresponding numbers.




3- 47

(2 M)

Grade

Grade or hardness indicates the strength with which the bonding material holds the abrasive

grains in the grinding wheel. This means the amount of force required to pull out a single bonded

abrasive grit by bond fracture. It does not refer to the hardness of the abrasive grain. The worn out

grit must pull out from the bond and make room for fresh sharp grit in order to avoid excessive

rise of grinding force and temperature.

(2 M)

Structure / Concentration of wheels

This term denotes the spacing between the abrasive grains or in other words the density of the

wheel. Structure of the grinding wheel is designated by a number.

(2 M)

6

How do you classify cylindrical grinders? What is the difference between “Plain and

universal cylindrical grinder”? (13 M) (Nov. 2016) BTL 5


centre type cylindrical grinding machine

Fig. illustrates schematically this machine and various motions required for grinding action.

(4 M)

Working principle: The machine is similar to a centre lathe in many respects. The work piece is

held between head stock and tailstock centres. A disc type grinding wheel performs the grinding

action with its peripheral surface. Both traverse and plunge grinding can be carried out in this

machine as shown in Fig.

(2 M)




3- 48

Universal cylindrical grinding machine

These grinders, in addition to the features offered by plain grinders, are provided with a swiveling

headstock and a swiveling wheel head. This permits the grinding of taper of any angle, much

greater than is possible in plain grinder. Universal machines are available to handle parts

requiring swings up to 450 mm and centre distance of 1800mm. This allows grinding of any taper

on the work piece. Universal grinder is also equipped with an additional head for internal

grinding. Schematic illustration of important features of this machine is shown in Fig.

(3 M)

(4 M)

7

Briefly discuss about the different types of abrasives used in a grinding wheel. (13 M) (May

2016) BTL 3


Types of abrasives



Quartz,

Corundum (75 - 90 % crystalline Al2O3 + Iron Oxide) and Diamond.



(3 M)

The abrasives that are generally used are

1. Aluminium Oxide. (Al2O3) 2. Silicon Carbide. (SiC)

3. Diamond. 4. Cubic Boron Nitride. (CBN)

(2 M)

Description of each. (4 x 2 M)

(8 M)

8

Describe the factors that contribute to broaching force and explain why they do so. (13 M)




3- 49

(May 2016) BTL 2

Answer: Page 402,403 – Dr.R.PANNEERDHASS

BROACHING

Basic principles of broaching

Broaching is a machining process for removal of a layer of material of desired width and depth

usually in one stroke by a slender rod or bar type cutter having a series of cutting edges with

gradually increased protrusion as indicated in Fig. In shaping, attaining full depth requires a

number of strokes to remove the material in thin layers step-by-step by gradually in feeding the

single point tool as illustrated in Fig. Whereas, broaching enables remove the whole material in

one stroke only by the gradually rising teeth of the cutter called broach. The amount of tooth rise

between the successive teeth of the broach is equivalent to the in feed given in shaping.

Instead of using simple broach sometimes the progressive cut type broach with the teeth segments

distributed into the three areas as shown in Fig. 4.56 (b) is used in surface broaching. The

progressive action reduces the maximum broaching force, but results in a longer broach.

a) Diagram (4M)

b) Principle (4M)

c) Construction (3M)

d) Advantages and Disadvantages (2M)

9

Explain the generalized classification of broaching machines. (13 M) (Nov. 2015) BTL 6


Different types of broaches

Broaching is getting more and more widely used, wherever feasible, for high productivity as well

as product quality. Various types of broaches have been developed and are used for wide range of

applications.

(3 M)

Broaches can be broadly classified in several aspects such as:

• Internal broaching or external broaching.

• Pull type or Push type.

• Ordinary cut or Progressive type.

• Solid, Sectional or Modular type.




3- 50

• Profile sharpened or form relieved type.

(10 M)

10

Explain the construction of a Push type and pull type broaching machine. (13 M) (Nov.

2015) BTL 6

Answer: Page 406,407 – Dr.R.PANNEERDHASS

Pull type and push type broaches

During operation a pull type broach is subjected to tensile force, which helps in maintaining

alignment and prevents buckling. Pull type broaches are generally made as a long single piece

and are more widely used, for internal broaching in particular. Push type broaches are essentially

shorter in length (to avoid buckling) and may be made in segments. Push type broaches are

generally used for external broaching, preferably, requiring light cuts and small depth of material

removal.

(4 M)

Both pull and push type broaches are made in the form of slender rods or bars of varying section

having along its length one or more rows of cutting teeth with increasing height (and width

occasionally). Push type broaches are subjected to compressive load and hence are made shorter

in length to avoid buckling. The general configuration of pull type broaches, which are widely

used for enlarging and finishing preformed holes, is schematically shown in Fig.

(4 M)

(5 M)

a) Diagram (4M)

b) Principle (4M)



PART * C

1

Describe as many parameters as you can that could affect the final surface finish in

grinding. (15 M) (May 2017)BTL 5


The final surface finish depends upon selection of grinding wheel by constant and variable factors

described as follows:

(1 M)

1. Constant factors

a. Physical and chemical properties of material to be ground. b. Area of contact.

c. Amount and rate of stock to be removed. d. Types of grinding machine.




3- 51

(2 M)

2. Variable factors

a. Work speed. b. Wheel speed. c. Condition of the grinding machine.

d. Personal factor. e. Type of grinding (stock removal grinding or form finish grinding).

(2 M)

Types of abrasives



Quartz, Corundum (75 - 90 % crystalline Al2O3 + Iron Oxide) and Diamond.



(2 M)

Grit size or grain size

It refers to the actual size of the abrasive particles. The grain size is denoted by the number.

Table 4.1 shows the different types of grit or grain sizes and their corresponding numbers.

(2 M)

Grade

Grade or hardness indicates the strength with which the bonding material holds the abrasive

grains in the grinding wheel. This means the amount of force required to pull out a single bonded

abrasive grit by bond fracture. It does not refer to the hardness of the abrasive grain. The worn out

grit must pull out from the bond and make room for fresh sharp grit in order to avoid excessive

rise of grinding force and temperature.

(2 M)

Structure / Concentration of wheels

This term denotes the spacing between the abrasive grains or in other words the density of the

wheel. Structure of the grinding wheel is designated by a number.

(2 M)

2

Would you recommend broaching a keyway on gear blank before or after

machining the teeth? Why? (15 M) (May 2016) BTL 6





3- 52

Internal broaching and broaches

Internal broaching tools are used to enlarge and finish various contours in through holes

preformed by casting, forging, rolling, drilling, punching etc. Internal broaching tools are mostly

pull type but may be push type also for lighter work. Pull type internal broaching tools are

generally provided with a set of roughing teeth followed by few semi-finishing teeth and then

some finishing teeth which may also include a few burnishing teeth at the end.

(4 M)

The wide range of internal broaching tools and their applications include:

• Through holes of different form and dimensions.

• Non-circular holes and internal slots.

• Internal keyway and splines.

• Teeth of straight and helical fluted internal spur gears.

(4 M)

(5 M)

3

(i) Explain with neat sketches horixontal pull broaching operation and vertical push

broaching operation. (8)

(ii) List out various types of bonding material used in grinding wheel. Explain any three. (7)

(15 M) (May 2015) BTL 6





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(4 M)

Broaching is a process of machining a surface with a special multipoint cutting tool called

broach which has successively higher cutting edges in a fixed path. Each tooth removes a

predetermined amount of material.

Horizontal broaching machine:

Mostly all horizontal broaching machines are of pull type. They are generally used for internal

broaching or surface broaching. The machine has a box type bed. The length of the bed is

twice the length of stroke. These machines are attached with a hydraulic or electric drive. Job

Is held by an adopter.

The adopter is fitted in the front vertical face of the machine. The broach is inserted in the job

by making a small hole initially or before starting the broach, and it is connected to the

pulling head. This head is attached with the ram with a guides. This machine has an automatic

stopper to control the length of stroke.

Vertical push broaching machine: (pushdown type)

It is used for surface broaching operations. It consists of a box shape column, slide and drive

mechanism. Broaching tools are mounted on the slide which is hydraulically operated and

accurately guided on column ways. The slide with the broaches travels at various speeds

which are controlled by the hydraulic drive. Its stroke is adjusted to suit the broaching

operation to be performed. The slide is provided with quick return mechanism. In this type

most of the machines are provided with quick return stoke.

The work table is mounted on the base in front of the column. The fixture is clamped to the

table. The work piece is held in the fixture. After advancing the table to the broaching

position, it is clamped and the slide with the broach travels downwards for machining the

work price. Then the table recedes to load a new work piece and the slide returns to its upper

position. The cycle is then repeated.




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(4 M)

(iii) BOND: It is an adhesive substance which holds the abrasive grains together to form the

grinding wheel.

(1 M)

(iv) Types of bonds - Bonds are classified into two types:

1. Organic - Resinoid, Rubber, Shellac & Oxychloride

2. Non - Organic - Metallic, Vitrified & Silicate

(2 M)

Vitrified bond (V)

Vitrified bond is suitable for high stock removal even at dry condition. It can also be safely

used in wet grinding. It can not be used where mechanical impact or thermal variations are

like to occur. This bond is also not recommended for very high speed grinding because of

possible breakage of the bond under centrifugal force.

Rubber bond (R)

Its principal use is in thin wheels for wet cut-off operation. Rubber bond was once popular for

finish grinding on bearings and cutting tools.

Silicate bond (S)

Silicate wheels are made by mixing abrasive grains with silicate of soda. The mixture is

moulded in a mould and dried for several hours. After drying, the moulded material is kept in

a furnace at about 2600 C for 20 to 80 hours. Silicate bonded wheels are light grey in colour.

These wheels are having a fairly high tensile strength.

Metal bond (M)

Metal bond is extensively used with super abrasive wheels. Extremely high toughness of

metal bonded wheels makes these very effective in those applications where form accuracy as

well as large stock removal is desired. (4 M)




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Subject Name: MANUFACTURING TECHNOLOGY II Subject Handler:


UNIT V– CNC MACHINING

Numerical Control (NC) machine tools – CNC types, constructional details, special

features, machining center, part programming fundamentals CNC – manual part

programming –micromachining – wafer machining

PART * A

Q.No. Questions

1.

List the differences between NC and CNC.BTL 1 NC stands for Numerical Control whereas CNC stands for Computer Numerical Control. In NC Machine the programs are fed into the punch cards. The cost of the NC machine is less as compared with the computer control machines.

2

Define linear bearings.BTL 1

A linear-motion bearing, or linear slide is a bearing designed to provide free motion in one

direction. There are many different types of linear motion bearings. Motorized linear slides such

as machine slides, XY tables, roller tables and some dovetail slides are bearings moved by drive

mechanisms.

3

Mention the type of ball screws. BTL 3

A ball screw is a mechanical linear actuator that translates rotational motion to linear motion with

little friction. A threaded shaft provides a helical raceway for ball bearings which act as a

precision screw.

4 Define feed drives. BTL 1

Feed drive – Computer. An optical drive that grabs the disc after it is partially inserted in the slot

and pulls it onto the drive spindle.

5

Discuss the types of motion control system used in NC machines. BTL 1

Numerical control (NC) (also computer numerical control (CNC)) is the automated control of

machining tools (drills, boring tools, lathes) by means of a computer. An NC machine alters a

blank piece of material (metal, plastic, wood, ceramic, or composite) to meet precise

specifications by following programmed instructions and without a manual operator.

6

Express the meaning of APT language. BTL 2

APT or Automatically Programmed Tool is a high-level computer programming language most

commonly used to generate instructions for numerically controlled machine tools. ... APT is a

language and system that makes numerically controlled manufacturing possible.

7

Discuss closed loop NC system with open loop system. BTL 1

In CNC systems, open and closed loop systems describes the two primary types of control

systems: Open Loop: Refers to a system using a stepper motor, where the communication

between the controller system and motor is one way. ... This is considered a drawback to the open

loop system.

8

Give the uses of preparatory function. How is it important in CNC programming? BTL 3

Preparatory Functions. Preparatory functions are G codes. These codes are the most important

functions in CNC programming because they direct the CNC system to process the coordinate

data in a particular manner. Some examples are rapid traverse, circular interpolation, linear

interpolation, and drilling.

https://en.wikipedia.org/wiki/Automation

https://en.wikipedia.org/wiki/Machining

https://en.wikipedia.org/wiki/Computer




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9

Illustrate the limitations of CNC machine tools. BTL 2

The computer numerical control includes machine tool and also non-machine tools. The CNC

system are mainly used in the milling machine, lathe machine, drill press, grinding, sheet metal

process, laser machine working. There is an automatic changing of the cutting tool operation that is developed in the CNC machining process. In Non-machine tools it includes the welding

machines, electronic assembly, coordinate measuring machine, and tape laying, filament winding

machines for composites.

a) Short production runs b) On conventional machining it requires expensive jigs and fixtures

c) Parts with complicated outlines

10

Examine - canned cycle. BTL 3

A canned cycle is a way of conveniently performing repetitive CNC machine operations. Canned cycles automate certain machining functions such as drilling, boring, threading, pocketing, etc... Canned cycles are so called because they allow a concise way to program a machine to produce a

feature of a part.

11

Define NC. BTL 1

Numerical control, popularly known as the NC is very commonly used in the machine tools. In other words, the numerical control machine is defined as the machined that is controlled by the

set of instructions called as the program.

12

Explain the major elements of NC machines. BTL 1

The machine tool can be any machine like lathe, drilling machine, milling machine etc. The machine tool is the controlled part of the NC system. In case of the CNC machines, the

microcomputer operates the machine as per the set of instructions or the program.

13

Compare the different NC machines. BTL 4

The machine tool can be any machine like lathe, drilling machine, milling machine etc. The machine tool is the controlled part of the NC system. In case of the CNC machines, the microcomputer operates the machine as per the set of instructions or the program.

14

Compare incremental and absolute system. BTL 1

Measurement solutions come in two flavors: Absolute and incremental. With an absolute

measurement system, the system will generate an absolute signal, e.g. the position. An

incremental system counts the number of steps between two positions. The clock is an absolute

measurement system, it will tell you a point in time.

15

Explain the role of computer for NC machine tool.BTL 4

CNC is a computer assisted process to control general purpose machines from instructions

generated by a processor and stored in a memory system. ... The controller uses a permanent

resident program called an executive program to process the codes into the electrical pulses that

control the machine.

PART * B

1

Describe the spindle drives used in CNC machine tools. (13M) (Nov.2017) BTL 2





3 - 57




3 - 58

a) Diagram (4M)

b) Principle (4M)



2

Discuss about slide ways used in CNC machine tools. (13M) (Nov. 2017) BTL 3





3 - 59

a) Diagram (4M)

b) Principle (4M)



3

Describe various type of CNC machine based on tool motion. (13M) (May 2017) BTL 3





3 - 60

Point to point system:

Tool is accurately located at some specified position. The spindle is first brought ot the starting point,

then moved to the next location (hole 1 along the marked path). On that location drilling operation is

performed and then tool moves to next location.

Straight line system:

The cutting tool can be moved along a straight line only, which is parallel to the principal axes of

motion. It is not possible to combine the motion of axes. Hence the tool motion is only along the X-

axis, Y-axis and Z-axis. Due to this angular cuts cannot be produced.

Continuous system:

In this there is relative motion between the tool and workpiece during the whole operation. Due to this relative motion, different curves and profiles can be cut. Actually, it is a combination of point to point and straight cut system.

a) Diagram (4M)

b) Principle (4M)



4

Explain the M code and G code with respect to manual part programming: (13M) (May

2017) BTL 3


M-codes are miscellaneous machine commands that do not command axis motion. The format for

an M-code is the letter M followed by two to three digits; for example:

[M02 End of Program]

[M03 Start Spindle- Clockwise]

[M04 Start Spindle- Counter Clockwise]

[M05 Stop Spindle]

[M06 Tool Change]




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[M07 Coolant On]

[M53 Retract Spindle] (raises tool spindle above current position to allow operator to do whatever

they would need to do)

M Codes are essential in ALL CNC programs to ensure a functioning line of code. All complete

CNC programs have an M code in both the first and last line of code.

(7 M)

G-codes are used to command specific movements of the machine, such as machine moves or

drilling functions. The format for a G-code is the letter G followed by two to three digits; for

example G01. G-codes differ slightly between a mill and lathe application.

for example:

[G00 Rapid Motion Positioning]

[G01 Linear Interpolation Motion]

[G02 Interpolation Motion-Clockwise]

[G03 Circular Interpolation Motion-Counter Clockwise]

[G04 Dwell (Group 00) Mill]

[G10 Set offsets (Group 00) Mill]

[G12 Circular Pocketing-Clockwise]

[G13 Circular Pocketing-Counter Clockwise]

(6 M)

5

Write the part program for drilling holes in the part shown below. The plate thickness is

20mm. (13M) (Nov. 2016) BTL4


(4 M)




3 - 62

(9M)

6

With a neat sketch explain the working of ATC. (13M) (Nov. 2016) BTL 5





3 - 63

a) Diagram (4M)

b) Principle (4M)



7

Explain the various elements of NC machine with closed loop control system. (13M) (May

2016) BTL 3





3 - 64

a) Diagram (4M)

b) Principle (4M)



8

List any five motions and control statements of computer assisted NC programming and

explain. (13M) (May 2016) BTL 2





3 - 65

Point to point system:

Tool is accurately located at some specified position. The spindle is first brought ot the starting point, then

moved to the next location (hole 1 along the marked path). On that location drilling operation is performed

and then tool moves to next location.

Straight line system:

The cutting tool can be moved along a straight line only, which is parallel to the principal axes of motion.

It is not possible to combine the motion of axes. Hence the tool motion is only along the X-axis, Y-axis

and Z-axis. Due to this angular cuts cannot be produced.

Continuous system:

In this there is relative motion between the tool and workpiece during the whole operation. Due

to this relative motion, different curves and profiles can be cut. Actually, it is a combination of

point to point and straight cut system.

a) Diagram (4M)

b) Principle (4M)




3 - 66



9

How is manual programming of a NC machine done. (13M) (May 2015) BTL 6


a) Diagram (4M)

b) Principle (4M)



10

Describe in brief the basic components of a tape operated NC machine tool. (13M) (May

2015) BTL 6


Load-N/C program – controller- own memory - entire program - encoded paper or magnetic tape

- execute commands - one block at a time.

Controller - built-in memory (a CNC type of N/C machine)- three methods. The first method -

keying program directly --multi thousand dollar controller and machine tool - keyed in one

command at a time.

(8M)




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(7M)

PART * C

1

Write CNC part program for the component shown in fig mention the assumptions made. (15M)

(May 2017) BTL 5





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[BILLET X110 Z200;

G21 G98;

M06 T01; //T01 TURNING TOOL//

G28 U0 W0;

M03 S1500;

G00 X112 Z1;

G71 U0.5 R0.1; // G71 TURNING CYCLE FIRST BLOCK U-DEPTH OF CUT, R- RETURN VALUE OF EACH CUT//

G71 P1 Q2 U0.1 W0.1 F50; //G71 TURNING CYCLE SECOND BLOCK

P, Contour start block number Q- Contour end block number, U- Finishing allowance in x- axis,

W- finishing allowance in z-axis, F- feed rate during G71cycle, S-spindle speed during G71 cycle)//

(5 M)

N1 G01 X20 Z-23;

G01 X36 Z-23;

G03 X50 Z-37 R8;

G01 X50 Z-45;

G01 X54.56 Z-85;

G02 X80 Z-95 R10;

G01 X80 Z-120;

G01 X100 Z-130;

G01 X100 Z-150;

N2 G01 X100 Z-150;

G28 U0 W0;

(5 M)

M06 T06; //T06 THREAD CUTTING TOOL//

M03 S1500;

G01 X22 Z1;

G76 P010060//G76-THREAD CUTTING, P010060(01-NO O SPINGS PASSES,00-THREAD RUNO UT, 60-FLUTE ANGLE, R-

FEED);

G76 X 00 Z -20 P919 Q150 F1.5;

G28 U0 W0;

MO6 T05;

M03 S1500;

G01 X40 Z-32;

G01X17 Z-32;

G28 U0 W0;

M06 T02;

M03 S1500;

G01 X18 Z-2;//CHAMFER//

G28 U0 W0;

M05;

M30;




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(5 M)

2

Write short notes on APT language. (15M) (May 2016) BTL 5


Diagram

(7M)

APT or Automatically Programmed Tool is a high-level computer

programming language most commonly used to generate instructions for numerically

controlled machine tools.

Program

(8M)

3

Discuss the important design features of CNC machine tool. (15M) (May 2015) BTL 6





3 - 70

a) Diagram (4M)

b) Principle (4M)



Documents

REGULATION 2017 ACADEMIC YEAR : 2018-2019 ME8451 ... fileCentre lathe, constructional features, specification, operations – taper turning methods, thread cutting methods, special