REGULATION :2017 ACADEMIC YEAR : 2018-2019 JIT-JEPPIAAR/MECH/Dr.D.Muruganandam & Mr.R.Devanathan /II nd Yr/SEM 04 /ME8451/MANUFACTURING TECHNOLOGY II/UNIT 1-5/QB+Keys/Ver1.0 3- 1 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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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
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
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
Answer: Page 148– Dr.R.PANNEERDHASS
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
Answer: Page 120– Dr.R.PANNEERDHASS
a) Diagram
(4M)
b) Principle
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(4M)
c) Construction
(3M)
1) Lathe bed
2) Tailstock
3) Headstock
4) Carriage
d) Advantages and Disadvantages
(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
Answer: Page 138 – Dr.R.PANNEERDHASS
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
Answer: Page 177– Dr.R.PANNEERDHASS
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
Answer: Page 172– Dr.R.PANNEERDHASS
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
Answer: Page 195– Dr.R.PANNEERDHASS
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
Answer: Page 203 – Dr.R.PANNEERDHASS
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
Answer: Page 211– Dr.R.PANNEERDHASS
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
Answer: Page 200 – Dr.R.PANNEERDHASS
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
Answer: Page 152 – Dr.R.PANNEERDHASS
a) Diagram
(4M)
b) Types
(4M)
c) Construction
(4M)
d) Properties
(3M)
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3- 25
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
Answer: Page 137– Dr.R.PANNEERDHASS
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
Subject Name: MANUFACTURING TECHNOLGY II Subject Handler:
Dr.D.Muruganadam&Mr.R.Devanathan
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
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
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
Answer: Page 300 – Dr.R.PANNEERDHASS
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
Subject Name: MANUFACTURING TECHNOLOGY II Subject Handler:
Dr.D.Muruganadam&Mr.R.Devanathan
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
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
Subject Name: MANUFACTURING TECHNOLOGY II Subject Handler:
Dr.D.Muruganadam&Mr.R.Devanathan
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
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
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
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)
c) Construction (3M)
d) Advantages and Disadvantages (2M)
4
Explain the M code and G code with respect to manual part programming: (13M) (May
2017) BTL 3
Answer: Page 469, 477– Dr.R.PANNEERDHASS
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: