Manufacturing Technology (3)

Milling Machine

Reported to: Dr.Waal Akl

Prepared by:

Mohamed Tarek Soliman Ahmed

Mohamed Sayed Saber Allamy

Mohamed AbdelRasol Sayed Mansour

Group No.11

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Table of Contents Milling machines ...................................................................................................................................................................... 2

Column and knee type ......................................................................................................................................................... 2

Horizontal milling machine ............................................................................................................................................... 3

Vertical Milling Machine ................................................................................................................................................... 4

Universal Milling Machine ................................................................................................................................................ 6

Production Type milling machines ....................................................................................................................................... 9

Bed type milling machine ................................................................................................................................................. 9

Planer Type milling machine .......................................................................................................................................... 11

Special types milling machines ........................................................................................................................................... 12

Rotary table milling machine.......................................................................................................................................... 12

Drum type milling machine ............................................................................................................................................ 13

Tracer milling machine ................................................................................................................................................... 13

Tool Holders ........................................................................................................................................................................... 22

Milling cutters......................................................................................................................................................................... 23

Milling operations .................................................................................................................................................................. 28

References .............................................................................................................................................................................. 32

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Column &knee Milling

machines

Horizontal

Vertical

Universal

The Milling Principle:

It is the operation in which metal is removed from work being fed against a rotating multipoint

cutter. The cutter rotates at a high speed and because of the multiple cutting edges it removes

metal at a very fast rate. That is why a milling machine finds application in production work.

Milling machines

Column and knee type

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Horizontal milling machine

Horizontal milling machines have a spindle or cutters mounted on a horizontal arbor

above an X-Y table. Some horizontal mills have a table, known as universal table that features a

rotary function for machining at different angles. Horizontal mills are optimal for machining

heavier pieces because the cutters have support from the arbor, as well as a bigger cross-section

area than a vertical

The Horizontal Milling Machine is a very robust and sturdy machine. A variety of cutters are

available to removed/shape material that is normally held in a strong machine vice. This

horizontal miller is used when a vertical miller is less suitable. For instance, if a lot of material

has to be removed by the cutters or there is less of a need for accuracy - a horizontal milling

machine is chosen.

The cutter can be changed very easily. The arbor bracket is

removed by loosening nuts and bolts that hold the arbor firmly

in position. The arbor can be slid off the over arm. The spacers

are then removed as well as the original cutter. The new cutter

is placed in position, spacers slid back onto the arbor and the

arbor bracket tightened back in position.

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Vertical Milling Machine

The vertical milling machine is made up of five major groups: base and column, knee,

saddle, table, and head, (see figure). The base and column are one piece that forms the

major structural component of the milling machine. They are cast integrally, ad provide

the mill with its stability and rigidity. The front of the column has a machined face which

provides the ways for the vertical movement of the knee. The knee supports the saddle

and table. It contains the controls for raising and lowering the saddle. Sitting atop the knee

is the saddle which supports the table. The saddle slides in dovetailed grooves into and

away from the machine, providing the mill with its Y-axis movement. On top of the

saddle sits the table. Being moved side-to-side, left-right, over the saddle furnishes the

mill with its X-axis movement. The workpiece is secured to the table through the use of

various types of holding devices. The head is the most complex assembly in the major

parts groups. This contains

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DIFFERENCES BETWEEN HORIZONTAL & VERTICAL

MILLING MACHINES:

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Universal Milling Machine

- A universal horizontal milling machine differs from the plain horizontal type because it

has a table swivel housing, which allows the table to move out 45 degrees from the

standard horizontal position. This workpiece movement allows for easier angular or

helical milling operations.

- The universal machine can be fitted with various attachments such as:

1. The indexing

fixture and various

special fixtures.

2. rotary table

3. slotting and rack cutting attachments

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Here a catalogue for a Universal milling machine For LAGUN

Company:

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SPECIFICATIONS OF MILLING MACHINE:

1. Size of the work table: expressed in length x width Eg: 1500 x 30mm.

2. Longitudinal movement: Total movement of table in mm(X-direction). Eg:800mm

3. Transverse movement: Total movement of saddle along with table in mm(Y-direction).

Eg:200mm

4. Vertical movement: Total movement of table, saddle & knee in mm mm(Z-direction).

Eg:380mm

5. Range of the speed: Speed variation in the gear box in RPM. Eg: 45 to 200 rpm.

6. Power capacity of the motor in HP. Eg: 2 HP

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Production Type milling machines

After World War II; metal cutting processes required more rigid more productive types of machine tools

especially milling machines. Engineers introduced new generation of milling machines to satisfy market needs.

Bed type milling machine

This refers to any milling machine where the spindle is on a head unit that moves up and down to move the cutter into the work, while the table sits on a fixed bed that rests on the floor. The usual feature of these

machines is the automatic cycle of operation for feeding the table that is repeated in a regular sequence.

It could be equipped with more than single head unit to be more productive:

a) Simplex refers to single head unit

b) Duplex refers to 2 head units

c) Triplex refers to 3 head units

a.Simplex bed type milling machine

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Bed type usually has a 3 axis movements with variants of design:

i. Bed moves on X, Y Axis and head unit moves on Z axis.

b.Duplex Bed type milling machine

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ii. Bed in gantry design is totally fixed and head unit moves on 3 axis X, Y and Z.

Planer Type milling machine

Large mills built in the same configuration as planer machine except with a milling spindle

instead of a planing head. This term is growing dated as planers themselves are largely a thing of the past. The

essential difference between a planer and a plano-miller lies in the table movement and the type of cutters. In

planer the table moves to give the cutting motion, but in a plano-miller it gives the feed motion.

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Special types milling machines Rotary table milling machine -Its a vertical milling machine but the circular table rotates about horizontal axis

-Used for machining flat surface at production rate

-Face milling cutters mounted on two or more vertical spindles

-work pieces are clamped on the horizontal table

-Cutters are adapted in difference heights in which the first cutter make first path for a work

piece and second cutter make the second path for another work piece and so on.

-So the loading and unloading of the work pieces is performed continuously by the operator

while the machine is working which provide time

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Drum type milling machine The drum milling machine is similar to a rotary

table milling machine but the work pieces are

clamped on a drum that rotates around horizontal

axis

The face milling cutter mounted on three or four

spindle heads rotate about horizontal axis and

remove metal from work pieces

finished pieces are removed after one complete

turn of the drum and then the new pieces are

clamped to it

Tracer milling machine The tracer controlled milling machine reproduces irregular or complex shapes of dies, moulds....

etc. by synchronized movements of the cutter and tracing element. The feed motion of the

machine is controlled automatically by means of a stylus that scans a profiled template or a

contoured model which is to be reproduced. The movement of the stylus energizes on oil relay

system, which in turn operates the main hydraulic system of the table. This arrangement is called

servomechanism.

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Types of Milling Machines

Work Holding

Before we can begin to start making chips on the milling machine, the workpiece must

somehow be securely fastened to the machine table. On most jobs that require milling,

setting up the workpiece is the most difficult part of the job. Setups require critical

thinking because not only does that part has to be fastened to the table, but the part must

be positioned so that the proper surfaces can be machined using the correct features of the

workpiece for positioning. If the setup is not properly planned and the accuracy is not

insured in the setup, the part will probably end up as scrap. To insure a good setup, the

operator must become aware of the types and proper uses of the work holding devices

associated with milling machines.

Milling Machine Vises

The milling machine vise is the most common type of work holding devise used on the

milling machine (Figure 1).

Figure 1: Plain Milling Machine Vise

The plain milling machine vise is used for holding work which has parallel sides. The vise

is bolted directly to the table using the T-slots in the machine table. The plain vise can be

accompanied by a swivel base (Figure 2).

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Figure 2: Swivel Base

Figure 3: Swivel Base and Vise

The swivel base is graduated in degrees and allows the vise to swivel in the horizontal

plane. The swivel base gives the vise a greater degree of versatility, but should be avoided

when doing heavy rough cutting operations because it reduces the rigidity of the setup.

For machining operations involving compound angles, a universal vise are commonly

used (Figure 4).

Figure 4: Universal

Angle Milling Vise

The universal vise allows the operator to tilt the

workpiece 90 degrees in the vertical plane as well as

swivel it 360 degrees in the horizontal plane.

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Figure 4

Locate the part in the center of the vise.

This equalizes the pressure on the vise

jaws.

Holding the workpiece off center puts

unequal pressure on the vise jaws. This

can cause the piece to loosen up.

The workpiece should always be

supported by the bottom of the vise or by

parallels.

Work pieces that are not supported will

move under the pressure of the cutting

forces.

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Keep the workpiece as low in the vise as

possible.

Work that extends out of the vise has a

greater chance of loosening up under

cutting conditions.

Figure 6: Vise Clamping Principles For Milling

V-Blocks:

V-Blocks hold and support round work for milling

or drilling (Figure 7). V-Blocks come in many

different sizes. On milling machines, V-Blocks are

typically clamped directly to the table (Figure 8).

Figure 7: V-Blocks

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Angle Plates:

An angle plate is an L shaped piece of Cast Iron or Steel that has tapped holes or slots to

facilitate the clamping of the workpiece (Figure 9).Angle plates are used when parts need

to have machining operations performed at a 90 degree angle to the axis of the

table(Figure 10 ).

Figure 9: Angle Plates

Figure 10: Angle plate being used to

machine the end of a long part.

Direct Mounting to the Table

Work that is too large or has an odd configuration is usually bolted directly to the table

(Figure 11). This method of work holding takes the most ingenuity and expertise.

There are a number of accessories that can be used to help you set up the workpiece.

Figure 11: Direct Clamping using strap clamps-Notice the stop block. It is used to align the

work as well as prevent the part from slipping.

A variety of commercially available clamp

sets are available for directly

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Parallels:

Parallels are pieces of steel bar stock

accurately machines so that the

opposing sides are parallel to each

other (Figure 13). Parallels are

provided in sets of two with identical

dimensions.

Figure 13: Parallels come in sets of two.

Figure 14: Parallels being used to raise the

workpiece above the table surface.

Parallels are used in order to

provide clearance under the

work so the cutting tool

does not damage the

machine table or the vise

base (see Figure 14).

In Figure 15 please study the correct and incorrect direct clamping practices.

Place clamp stud close to the

workpiece.

Do not place clamp stud closer to the

support

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Use shims between finished

surfaces and clamps

Clamps in contact with finished surfaces will

mar the workpiece.

Clamps that are level or with a slight

decline toward the workpiece will equalize

the clamping pressure.

Angling clamps incorrectly puts

pressure on the support, not the

workpiece.

Place support parallels

directly under clamps.

The spring caused by

improper parallel placement

will cause the part to bow.

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The indexing fixture:

The index fixture (Figure 4-19) consists of an index head, also called a dividing head,

and footstock which is similar to the tailstock of a lathe. The index head and footstock

attach to the worktable of the milling machine by T-slot bolts. An index plate containing

graduations is used to control the rotation of the index head spindle. The plate is fixed to

the index head, and an index crank, connected to the index head spindle by a worm gear

and shaft. Workpieces are held between centers by the index head spindle and footstock.

Workpieces may also be held in a chuck mounted to the index head spindle or may be

fitted directly into the taper spindle recess of some indexing fixtures. There are many

variations of the indexing fixture. Universal index head is the name applied to an index

head designed to permit power drive of the spindle so that helixes may be cut on the

milling machine. Gear cutting attachment is another name applied to an indexing fixture;

in this case, one that is primarily intended for cutting gears on the milling machine.

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Tool Holding 1) Arbor: The cutters having a

bore at the Centre are mounted

and keyed the arbor which is

connected with the milling

machine spindle by a draw bolt

end driving keys.

2) Collet: a form of sleeve bushing for reducing the size of

the taper hole at the nose of the milling machine spindle so

that an arbor or a milling cutter having a smaller shank than

the spindle taper can be fitted in.

Straight shank cutters are usually held in a special adapter

called spring collet or spring chuck. The nose end of the collet is tapered from inside and threaded for a small

distance from outside.

3) Bolted cutters:

large diameter Face milling cutters which have no shank are

fixed directly on the nose of the spindle

this method provide more rigidity

4) Screwed on cutters: The small cutters having threaded holes at the Centre are screwed on

the threaded nose of an arbor which is mounted on the spindle in the usual manner.

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Milling cutters Milling cutters may be classified according to:

1) The methods of mounting the

cutter:

1) arbor type cutters

2) shank type cutters

3) face type cutters

2) The direction of rotation : right or left hand cutters

3) The constructional of the cutter

1) Solid cutter: has teeth integral with the cutter body.

2) Tipped solid cutters: the cutter teeth are made of cemented carbide which are brazed

on the tool shanks of an ordinary tool steel cutter body

3) Inserted teeth cutters: In large milling cutters, the teeth or blades are inserted or

secured in a body of less expensive materials. The blades are usually held in the cutter

body by mechanical means.

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4) The purpose of use of the cutter:

1) Special milling cutter: Special milling cutters are designed to perform special

operations.

2) Standard milling cutter: conventional type of milling cutters whose dimensions

are standards

Types Standard milling cutter:

plain milling cutters: cylindrical shape & have teeth on

the circumferential surface only

and it classified as

1) heavy or light duty plain

milling cutters

2) heavy or light duty helical

milling cutters

side milling cutters:

the teeth on the circumferential surface and one or both sides

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Plain side milling cutters :

have alternate teeth with

opposite helix angle

Half side milling cutter

side teeth for size and

finishing

Slitting saw

used for parting off

operations

Single angle milling cutter

have teeth on conical or

angular face and on the flat

side

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Double angle milling cutter :

teeth on two conical sides

the angle may be not

symmetrical with respect to

the plain

End mill :

used to make slots or small

holes

the shank may be tapered or

straight

t-slot milling cutter

Dovetail milling cutter

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Formed milling cutter

Gear cutter

Thread cutter

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Milling operations

There is two concepts of cutting in milling; up-milling and down-milling.

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Operations:

1) Plain Milling: Process to get the flat surface on the work piece in which the cutter axis and work piece axis are parallel.

2) Face Milling: Operation carried out for producing a flat surface, which is perpendicular to the axis of rotating cutter.

3) End Milling: Operation performed for producing flat surfaces, slots, grooves or finishing the edges of the work piece.

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4) Slot Milling: Operation of producing slots like T-slots, plain slots, dovetail slots etc.,

5) Angular Milling: Operation of producing all types of angular cuts like V-notches and grooves,

serrations and angular surfaces.

6) Form Milling: process of machining special contours composed of curves and straight lines, or entirely of curves, at a single cut.

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7) Gang Milling: Process to get different profiles on the work piece simultaneously with two or more cutters, at a single cut.

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References http://en.wikipedia.org/wiki/Milling_%28machining%29

http://its.foxvalleytech.com/MachShop3/basicmill/WorkHold.htm

http://www.slideshare.net/SharanabasappaBhurke/milling-and-grinding-machines

http://www.technologystudent.com/equip1/hmill2.htm