CHAPTER-1
INTRODUCTION
I had the opportunity to study both conventional and CNC machines, but have
given more stress on the CNC machines, owing to their emerging importance. A
general description of conventional lathe and milling machines has been given. The
concepts of Computer Numerically Controlled machines have been explained in
greater detail.
Figures 1.1 CNC Machine
After its foundation from 1947, “NPL has made its valuable contribution to the
community, industries as well as to building edge of enlightenment in areas of
engineering”.
WORKSHOP AREAS
Cutting and welding
Electroplating
Designing
Working on sheet metal
Carpentry capacity
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Conventional machines section
CNC machines section
CONVENTIONAL MACHINES SECTION
In this section, some of the machines are :
Bandsaw-
The bandsaw is useful for cutting stock to size and roughing out shapes. It cuts
curved shapes very well.
Belt sander-
Belt sander is used to remove rough edges. It makes use of an abrasive riding
belts. Effective on wood ,plastic and most metals.
Drilling machine-
The drill press is mostly used for drilling holes, reaming, countersinking
etc.and other hollow surfaces.
Power hacksaw-
A type of hacksaw powered either by its own electric motor or connected to
an engine.
DRILLING MACHINE POWER HACKSAW
For measurement and testing, micrometers, calipers, etc. as well as for sheet
electroplating, metal work, etc., several other machines are used.
Surface grinding machine – High precision surface finish is provided by this
machine tool. The machine has highly adaptable grinding wheel which revolves in the
spindle. The part or work-piece is fed by a straight table placed under the grinding
wheel.
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Figures 1.2: Drilling Machine Power Hacksaw
Slotting machine – It is analogous to the vertical shaper machine. For machining
straight, smooth surfaces, this machine is commonly used.
Figure1.3: Slotting machine
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CHAPTER-2
MANUFACTURING OPERATIONS TO BE CARRIED OUT ON A LATHE
Turning – Reduction of part or work piece’s diameter to a desired dimension.
Facing - Creating a smooth, flat and accurate face perpendicular to the axis of
a part or workpiece on lathe machine.
Parting - Shallow and fine as compared with a turning tool. Parting is intended
to make constricted grooves.
Drilling - Accurately concentric holes are also drilled with the axis of a
cylindrical work-piece on lathe machine.
Boring - An operation which is intended to enlarge a hole with an SPCT
(Single-Point Cutting Tool).
Threading – Internal and external threads is formed by the use of a tap and a
die respectively.
Fig 2.1: Lathe
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TYPES OF LATHE MACHINES
The most commonly used lathe machines - Bench Lathe/Centre Lathe/Engine Lathe
Tool-room Lathe –
Lathe enhanced for tool room work. This lathe has all possible features that
may be misplaced from less costly models, such as a taper attachment, collet closer,
and others.
Capstan lathes and Turret lathes –
These lathes are used for tedious manufacturing of identical work-pieces.
Multi-spindle lathe –
These lathes have an automated control system and having one or more spindle.
CNC LATHE
Cnc lathe are swiftly replacing the older production lathes due to their ease of setting
and operation. The job may be designed by the Computer-aided-manufacturing(CAM)
process, the design of the processed job be uploaded to the machine and once set and
trailed the machine will continue to turn out parts under the supervision of a machine
operator.
MILLING MACHINE
Milling is one of the most versatile machining operation and most of the shapes can
be produced with the help of it. In the milling operation the milling cutter with its
several edges at its outside is being fixed on the vice and being rotating on the armour
and the job being fixed brought in closer to it.
If “f ” is the feed velocity of the table in mm/min, the effective feed per tooth in mm
will be f/(NZ),where N is the cutter rpm and Z is the number of teeth in the cutter.
The material removal rate per unit width of the job is given by fd.
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Figure 2.2 Milling machine
Classification of Milling Cutters
Figure 2.3:classification of milling cutter
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OPERATIONS TO BE CARRIED OUT ON MILLING MACHINES
Figure 2.3 Operations Done On Milling Machines
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SEVERAL COMMON CNC CONTROL SYSTEMS
FIDIA
DECKEL
SINUMERIC
HINUMERIC
ECS
LECS
HEIDENHAIN
GILDEMEISTER
A CNC Milling center by DECKEL
NUM
SELCA
MARPOSS
Z-16
FANUC
FAGOR
BASIC TERMS ASSOCIATED WITH CNC MACHINING
Machine Zero –
It is a point at the origin of the machine’s coordinate measuring system. This
point is taken as a reference for all the axis movements and measurement of other
dimensions. Machine zero is related with the origin of CMS (co-ordinate measuring
system).
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Figure 2.4 Machine Zero
Machine-Reference Point –
It denotes to the starting point of return for the benefit of feedback/ measuring
systems. The feedback/measuring system has to be adjusted by indicating this point
on each axis, whenever a CNC machine is switched ON.
Work Zero –
This is the origin for measuring of dimensions of parts. The programmer is
allowed to choose it anywhere on the drawing.
Axis Designation –
The Electronic Industries Association (EIA) RS 274-B standard is used for
designation of axis for each machine tool. This conforms to ISO Recommendations
R831. “Left hand rule” technique is used for the terminology of the X, Y and Z axis
(main axes). The orientation of X-axis is indicated by the thumb; the Y-Axis is
indicated by the index finger, and The Z-axis is indicated by the middle finger points.
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Tool and tool offset –
The particular tool and tool offset in the program is called by T function. The
data entered in the coordinate system preset block is corrected by the tool-offset. It is
very convenient to set up the tools and make alterations in work-piece size using the
tool offsets.
Spindle speed –
It is the rotating frequency of the spindle of the machine, measured in RPM
(Revolutions/minute). Depending upon the material being cut, the preferred speed is
to be determined. The quality of the surface finish and the tool life is affected by
using the accurate speed of spindle for work-piece material as well as for tools.
Feed rate –
It is the velocity at which the cutter is fed in advanced against the part or
work-piece. For turning and boring, it is described in millimeters per revolution
(distance per revolution). It is described in millimeters per minute (distance / time) for
the purpose of milling.
Cutting Speed –
It is defined as the speed (or rate) that the material moves towards the cutting
edge of tool, regardless of the process of machining used.
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CHAPTER-3
CNC MACHINES’s CONSTRUCTION DETAILS
Fundamentals of motion transmission
In a CNC machine, the connection between the screw and the nut is through
an endless stream of re-circulating steel balls, replacing sliding friction threads with
rolling friction. Greater efficiency, reduction in wear and tear and reversibility are the
main advantages.
Figure 3.1 Elements of motion transmission
Hydrostatic Slide-ways
An air or oil is pumped into small pockets machined into slides which are in
contact with the slide-ways in hydrostatic slide-ways,
CNC machines has an in-built computer system that allows the operator to
read, analyze, and edit the programmed information. The computer works on a binary
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code value, 0 and 1 code is used for information and processing respectively in CNC
machines. Unique in-built software gathers the user entered program or language and
convert it into machine language and the machine moves the tool by its servomotors.
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CNC MACHINES WORKING
1. Modes of Operation
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Manual operation
CNC PROGRAMS PROCESSING
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CONCLUSION
The significance of milling and lathes machines, although these all are
conventional, can not be challenged. These types of machines have shown a vital role
to bring the revolution in industrial field and placed the foundations. The conventional
machines are required in small quantities while the CNC machines must be increased
to enhance the quality and quantity of production.
Less trained / skilled personnel can drive the CNC machines.
Similarity of the products manufactured depends on the ability of worker.
CNC machines can produce numerous products, which are very analogous and
accurate.
Conventional machines provides very less chances for major improvement.
CNC machines can be updated by using improved software configuration to
operate the machines.
Conventional machines are required with very highly skilled operators to
work.
One worker cannot drive more than one conventional machine at a time.
A single person can control various CNC machines and work themselves.
Conventional machines are very tough to run for some hours. The worker has
to constantly focus on the part in hand.
CNC machines can be used continuously for long intervals and only need to
be switched off for occasional maintenance.
Conventional Machine CNC Machine.
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REFERENCE
www.nplindia.org
www.wikpedia.org
www.fortune.com
www.headland.com
www.machinetoolhelp.com
www.cncezpro
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