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
2
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
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