Drona Gyaan

Drona Gyaan
MACHINING-INTRODUCTION
Manufacturing is a VALUE ADDITION process by which raw materials or objects of low value due to
inadequate material properties, poor or irregular size, shape and finish are converted into HIGH
UTILITY and HIGH VALUE products with proper size , form , dimensions and finish , imparting some
functional ability.
Manufacturing is classified into:
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FORMING PROCESSES: e.g. Rolling, Extrusion.
MACHINING PROCESSES: e.g. Drilling, Milling
MOULDING PROCESSES: e.g. Blow and Dip moulding
CASTING PROCESSES : e.g. Sand and Centrifugal casting.
“Machining” is basically a removal process by which jobs of desired dimensions and surface finish are
produced by gradually removing the excess material from the preformed blank in the form of chips,
with the help of cutting tools moved past the work surface.
Every machining process requires choice of accurate input parameters. In this round you need to
choose the four essential input parameters, namely: Material, Feed, Speed and Depth of cut
(M,F,S,D). The three key mechanical inputs in metal removal operations are feed, speed, and depth
of cut. Manipulating the feed, speed and depth of cut can maximize the benefits of a particular
cutting fluid and can increase productivity. However, like most decisions, the choice of feed, speed
and depth of cut must be based on the customer’s objectives. What is their goal in this application?
Do they want to manufacture parts faster or maximize tool life? How important is the surface finish
and dimensional accuracy of the part? Answers to these questions will drive their decisions on feeds,
speeds and depth of cut.
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MATERIAL-Material implies the type of work material which is selected for machining
operations. Here are commonly used work material:- Carbon steel, Alloy Steels, Cast Iron,
Stainless steel, Aluminium , Aluminium alloys, Magnesium Alloys.
FEED- Feed rate is the relative velocity with which the cutter is advanced along the work
piece. Feed rate units depend on the motion of the tool and workpiece; when the workpiece
rotates (e.g., in turning and boring), the units are almost always distance
per spindle revolution (inches per revolution [in/rev or ipr] or millimeters per revolution
(mm/rev).
DEPTH OF CUT - The measurement (normally in inches or millimeters) of how wide and deep
the tool cuts into the workpiece.
SPEED- Speed is the rate of rotation of the spindle where the tool is held. It is measured in
revolutions per minute (RPMs).
Machine Tools:
A machine tool is defined as one which while holding the cutting tools, would be able to
remove metal from a workpiece so as to generate job of required shape, size and surface
finish.
They are classified into –
1. General purpose machine tools(GPM) : are those designed to perform a variety of
machining operations on a wide range of components. e.g. lathe, shaper, milling
machine.
2. Production machine tools: are those where a number of functions of the machine
tools are automated such that the operator skill required to produce the component
is reduced. Hence these machine tools can be used for large volumes of production.
3. Special purpose machine tools(SPM) : are those machine tools in which the setting
operation for the job and tools is practically eliminated and complete automation is
achieved. e.g. cam shaft grinding machine, piston turning lathe.
4. Single purpose machine tools : are those which are designed specifically for doing a
single operation on a class of jobs or on a single job. These tools have highest
amount of automation and are used for really high rates of production. e.g. transfer
lines composed of unit heads for completely machining any given product.
LATHE : is the oldest machine tool invented, starting with the Egyptian tree lathes. This
primitive device has evolved over the last two centuries to be one of the most
fundamental and versatile machine tools with large variants, to be used practically in all
the manufacturing shops. The principle form of surface produced in a lathe is the
cylindrical surface.
TURNING
Material
Cast iron
Cast steel
AISI 1020
AISI 1040
Manganese steel
Nickel steel
Stainless steel
Spring steel
Tool steel
Tool steel
Tool steel
Tool steel
Malleable iron
Glass
Copper
Brass
Bronze
Zinc alloys
Hardness
200
280-300
110-160
170-200
PARTING
185-215
200-240
150
400
150
200
215
300
110-130
80-85
190-200
180-200
110-125
Speed m/min
Feed mm/rev
25-35
0.13-0.30
12-15
0.06-0.19
35
0.20-0.50
Common
25
0.13-0.30
DRILLING
Lathe
5
0.06-0.19
Operations
18
0.06-0.19
15
0.13-0.30
6
0.06-0.19
23
0.20-0.50
18
0.13-0.30
15
0.13-0.30
KNURLING
12
0.06-0.19
26
0.20-0.50
4.5
0.06-0.19
21
0.06-0.19
70
0.20-0.50
54
0.20-0.50
70
0.20-0.50
SAMPLE PARAMETER VALUES FOR DRILLING OPERATION
MOULDING- INTRODUCTION
“Moulding” is the process of manufacturing by shaping liquid or soft raw material using a rigid
frame called a mould.
Moulding Flask: A moulding flask is one which holds the sand mould intact . Depending upon the
position of the flask in the mould structure , flask is referred by various names such as
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DRAG- lower moulding flask
COPE- upper moulding flask
CHEEK- intermediate moulding flask, used in three piece moulding.
Pattern is the replica of the component which we are going to manufacture.
Materials used for making patternWood
TYPES OF MOULDING SAND:
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GREEN SAND: It is also known as natural sand and is obtained from natural resources. It is a
mixture of silica sand ,with 18 to 30% clay and 6 to 8% water. The clay and water give bonding
strength to green sand. It is fine, soft, light and porous.
Green sand is used for casting small or medium sized moulds. Coal dust is mixed in green sand to
prevent defects in castings.
DRY SAND: Dry sand moulding is employed for large castings. The moulds prepared in green
sand are dried or baked to remove all moisture of the moist sand.
LOAM SAND: Loam sand is a mixture of clay and sand milled with water to a thin plastic paste
from which moulds are built up on a backing of soft bricks. It contains 50% clay and fire clay.
Loam is dried very slowly and completely before it is ready for casting.
BACKING SAND: It is black in colour due to addition of coal dust and burning or coming in
contact with molten metal. It is used to fill in mould at the back of facing layer.
PARTING SAND: Parting sand is used to keep the green sand from sticking to the pattern.
EQUIPMENTS USED IN MOULDING
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Showel
Riddle
Rammer
Trowel
Slicks
Lifters
Draw spikes
Swab
Rawhide mallot
Gate cutter
Clamp
TWO BOX MOULDING:
Two box moulding uses the moulding box made in two parts. The upper part is known as COPE
and the lower one is known as DRAG. Two parts are fitted with a suitable clamping and locating
device. Clamping prevents the cope from lifting due to the pressure of the molten metal while
pouring. Locating device enables the two parts to maintain proper alignment at all times. In this
method drag and pattern are placed on the moulding box and the sand is rammed in the drag.
The drag is then rolled over the box. The other part of the pattern is fitted over bottom one and
cope is placed over the drag.