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Purpose: The purpose of this experiment is to give a general knowledge to
students on how to operate the milling machine and know each type and segment of the
machines. In this experiment, students will study on how to shape and mill the multi
segment shape such as cubic shaped.
Equipment:
A Types of milling machine:
| Milling machine |
Milling machines are made in many types and sizes. The drive
is either a cone pulley bet drive or an individual motor. The feed of the work is manual,
mechanical, electric, or hydraulic. There are varieties of table movements. |
| Hand milling machine |
The simplest milling machine is hand operated. It may have
either the column and knee construction or the table is mounted on a fixed bed. Machines
operated by hand are used principally in production work for light and simple milling
operations such as cutting grooves, short keyways, and slotting. These machines have a
horizontal arbor for holding the cutter and a worktable is usually provided with three
movements. The work feeds to the rotating cutter either by manual movement of a lever or
by a hand screw feed. |
| Plain milling machine |
It is much sturdier construction and is provided with a
power-feeding mechanism to control the table movements. Plain milling machines of the
column and knee type have three motions: longitudinal, transverse, and vertical. The
machine uses stop dogs to control machine slide movements. Automatic table cycles are
available. Cutters are mounted on a horizontal arbor rigidly supported by the overarm. |
| Vertical milling machine |
It is the vertical position of the cutter spindle. The table
movements are the same as in plain milling machines. Ordinarily no movements are given to
the cutter other than the usual rotational motion. However, the spindle head may be
swiveled, which permits setting the spindle in a vertical plane at any angle from vertical
to horizontal. This machine has a short axial spindle travel to facilitate step milling.
Some vertical milling machines are provided with rotary attachments or rotating worktables
to permit milling circular grooves or continuos milling of small production parts. End
mill cutters are used. It is used to mill or drill any block into a required shape and
measurement. |
| Planer milling machine |
This milling machine receives its name from its resemblance
to a planer. The work is carried on a long table having only a longitudinal movement and
is fed against the rotating cutter at the proper speed. The variable table feeding
movement and the rotating cutter are the principal features that distinguish this machine
from a planer. Transverse and vertical movements are provided on the cutter spindle.
Planer milling machines are designed for milling large work requiring heavy stock removal
and for accurate duplication of contours and profiles. |
| Machining center |
These NC machines are designed for small-to medium-lot
production. A machining center may refer to one or more NC machines that have multipurpose
capability machining. |
| Planetary milling machine |
It is used for milling both internal and external short
threads and surfaces. The work is held stationary and the milling cutters make all
movements necessary for the cutting. At the start of a job, the rotating cutter is in
center or neutral position. It is first fed radially to the proper death and then given a
planetary motion either inside or around the work. |
| Duplicating machine |
The production of large-forming dies for automobile fenders,
tops, and panels is an important use of duplicator machines. These machines are
reproducing a part from a model with no reduction or enlargement of size. It is also known
as a copy-milling machine. |
In this experiment, vertical milling machine is used.
Components of vertical milling machine:
| Name |
Function |
| Base |
Forms part of column; storage tank for coolant |
| Table |
Carries suitably mounted; workpiece to the cutter |
| Spindle |
Provides mounting and drive for cutter |
| Spindle speed gearbox |
Select speed of rotation of spindle |
| Table feed gearbox |
Provides selection of automatic feeds for table |
| Table hand feed (longitudinal) |
Moves table towards or away from cutter |
| Table vertical travel control |
Raises or lowers table (y-axis) |
| Table cross travel control |
Moves table towards or away from column (z-axis) |
| Vertical head |
Houses spindle |
| Spindle vertical adjustment handle |
Provides vertical traverse for spindle |
B Milling machine is versatile because of the large variety of cutters and
the kinematics versatility of the machine tool components. The milling cutter is
multitooth. Milling cutters consists of four basic groups of materials: tungsten carbide,
cermet, ceramic, and polycrystalline. The cutters most generally used that are classified
according to their general shape or the type of work they will do. Types of milling
cutters:
| Plain milling cutter |
A plane cutter is a disk-shaped cutter having teeth only on
the circumference. The teeth may be either straight or helical if the width exceeds 5/8
in. (15.9 mm). Wide helical cutters used for heavy slabbing work may have notches in the
teeth to break up the chips and facilitate their removal. |
| Side-milling cutter |
This cutter is similar to a plain cutter except that it has
teeth on the side. Where two cutters operate together, each cutter is plain on one side
and has teeth on the other. Side-milling cutters may have straight, helical, or staggered
teeth. |
| Metal-slitting saw cutter |
This cutter resembles a plane or side cutter except that it
is made very thin, usually 3/16 in. (4.8 mm) or less. Grinding the sides to afford
clearance for the cutter relieves plain cutters of this type. |
| Angle-milling cutter |
All angle-shaped cutters come under this classification. They
are made into both single- and double-angle cutters. The single-angle cutters have one
conical surface, whereas the double-angle cutters have teeth on two conical surfaces.
Angle-milling cutters are used for cutting ratchet wheels, dovetails, flutes on milling
cutters, and reamers. |
| Form milling cutters |
The teeth on these cutters are given a special shape. They
include convex and concave cutters, gear cutters, fluting cutters, corner rounding
cutters, and many others. |
| End mill cutters |
These cutters have an integral shaft for driving and have
teeth on both periphery and the end. The flutes may be either straight or helical. It is
also used for surfacing projections, squaring ends, cutting slots, and in recess work such
as die making. |
C Mild steel-cubic shaped, which lengths are 52 mm X 52 mm X 43 mm.
D Face mill cutter.
E Vernier caliper gauges.
Procedure:
- First of all, the face mill cutter is set to rotate in 370 rotation per minute (rpm).
- Then, the slot fitting is set to 22 unit.
- A piece of paper (can be called as ‘stamp’) soaked in the coolant is pasted
onto the mild steel in order to adjust the face mill so that it just touch the surface of
the block.
- Finally, switched on the motor and when the pasted stamp is removed by the face mill,
the y-axis is set to be zero at this point.
- The coolant and the motor are switched.
- Then, the feed gearbox is on, which is provided the selection of automatic feed for the
table to move in x-axis (from right to left or vice versa).
- Y-axis is adjusted to 2 mm for polishing the mild steel and removes the rusted surface.
- To start milling the mild steel, the steel is needed to be milled about 40 ± 0.5 mm for y-axis, 47 ± 0.5 mm for
z-axis, and 47 ± 0.5 mm for x-axis for all both sides.
- First of all, the milling process goes to one side of the block first. The block cannot
be milled straight away to it’s required measurement, it must be milled part by part
until it reaches the required measurement so that the surface of the block will be smooth
and will not exceeding the tolerance needed for each axis and the distortion also can be
avoided.
- Then, the machine will be switched off and the coolant also and the milled block is
measured using a vernier caliper gauge to make sure whether it is in right scale or not.
- Finally, when all measurement for the block are the same as required, the milling
machine must be switched off and cleaned. This is to make sure that no residue or scrap
left behind to ease the next users.
- I have to make sure that all 6 surfaces have to be done by using the same procedures.
Safety Precautions:
- Wearing protective clothes.
- Wearing goggles.
- Wearing boots or shoes.
- When doing experiment, people who handle experiment have to stand at the side of the
machine. Other people have to stand not to close to the machine because of safety.
- We have to follow all the instructions given by our instructor, Encik Kamaruddin Ali in
order to avoid any accident.
- Always used the safety precaution while doing this experiment and also for future’s
experiment.
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