MACHINE TOOLS
INTRODUCTION
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Generating and Forming
Methods of producing surfaces
Surfaces are produced in machining by:
–Generating
• by providing a suitable relative motion between the
workpiece and cutting tool
• Shape or form of the surface produced is not
identical to the surface or profile or contour of the
cutting edge
–Forming
• The shape of the surface would be identical to the
shape of the cutting edge
–Generating and Forming
• Many times, the surface generated is a combination
of both Generating and Forming.
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Methods of generating surfaces
Generating Shape
(a) straight turning
(b) taper turning
(c) contour turning
(d) plain milling
(e) profile milling.
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Forming to Create Shape
Methods of forming surfaces
(a) form turning
(b) drilling
(c) broaching
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Generating and forming surfaces
Forming and Generating
(a) thread cutting
on a lathe
(b) slot milling
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Generatrix and Directrix
Generating Motions
Generatrix (primary motion): is the main motion
provided by a machine tool to cause relative motion
between the tool and workpiece so that the face of
the tool approaches the workpiece material. Usually,
the primary motion absorbs most of total power
required to perform the machining operation.
Direcrtix (feed motion): is a motion that may be
provided to the tool or workpiece by a machine tool
which, when added to the primary motion, leads to
chip removal and the creation of a machined
surface with the desired geometric characteristics. It
usually absorbs a small proportion of the total power
required to perform the machining operation.
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Concept of Generatrix & Directrix
Generatrix and Directrix
Cutting Motion
P
Feed
a) Motions of cutting point
b) Production of surface
Generatrix
Directrix
c) Generatrix & Directrix
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Generatrix and Directrix – Flat surface
Concept of Generatrix & Directrix
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Generatrix and Directrix – Flat surface
Shaping
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ME 352: Manufacturing Technology - II
09 of 18
Generatrix and Directrix – Cylindrical surface
Concept of Generatrix & Directrix
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Generatrix and Directrix – Cylindrical surface
Turning
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Generatrix and Directrix – Drilling
Drilling
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Generatrix and Directrix – Plain Milling
Plain Milling
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Generatrix and Directrix – Form Milling
Form Milling
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Generatrix and Directrix – Various operations
Tool & W/p Motions for Traditional Machining
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Example
Worked out problem
Show the tool work motions and the Generatrix
and Directrix in external thread cutting in center
lathe.
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Classification of Machine Tools
Machine Tool
• A device in which the energy is expended
in removing the excess amount of
material from the workpiece in the form of
fine chips.
• Machine tools are mother machines, since
without them no component can be
finished and the success of the industrial
revolution can be mainly attributed to
them.
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Elements of Machine Tools
Machine Tool basically consists of

Devices for firmly holding the tool and work
 Drives for providing power and motions to the
tool and work
 Kinematic system to transmit motion and
power from the sources
to the tool-work

Automation and control systems
 Structural body to support and accommodate
these systems with
sufficient strength and
rigidity.
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Machine Tool Drives
Machine tools are driven by electric motors and elements like beltpulley, gears are used.
Hydraulic drive in some machine tools
Machine tools need wide range of cutting speeds and feed rates
to enable

machining different parts (material and size)

using different cutting tools (material, geometry and size)
 various machining operations like high speed turning to
low speed thread cutting in lathes

degree of surface finish desired
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Machine Tool Drives . . .
Types of Drives
Stepped drive
Very common in conventional machine tools
Discrete number of speeds and feeds are available and preferably in G.P.
(Geometric Progression) series.
Stepped drive is obtained by using
gear boxes or cone pulley (old method) along with the power source
Stepless drive
CNC machine tools use stepless drives enabling flexibility in optimum
selection and automatic control of the speeds and feeds.
Stepless drive is accomplished usually by
• Variable speed AC or DC motors
• Stepper or servomotors
• Hydraulic power pack
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Classification of Machine Tools
Classification of Machine Tools
• Based on Production capability and
application
– General Purpose Machine Tools
– Production Machine Tools
– Special Purpose Machine Tools
– Single Purpose Machine Tools
• Based on type of cutting tools used
– Those using single point tools
– Those using multipoint tools
– Those using abrasive wheels
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Classification of Machine Tools
Classification of Machine Tools
• According to direction of major axis
– Horizontal - horizontal center lathe, horizontal boring
machine etc.
– Vertical – vertical lathe, vertical axis milling machine
etc.
– Inclined – special (e.g. for transfer machines).
• According to degree of automation
– non-automatic – e.g. center lathes, drilling machines
etc.
– semi-automatic – capstan lathe, turret lathe, etc.
– automatic – e.g., single spindle automatic lathe, CNC
milling machine etc.
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Classification of Machine Tools
Classification of Machine Tools
• According to size:
– heavy duty – e.g., heavy duty lathes (e.g. ≥
55 kW), boring mills, planning machine,
horizontal boring machine etc.
– medium duty – e.g., lathes – 3.7 ~ 11 kW,
column drilling machines, milling machines
etc.
– small duty – e.g., table top lathes, drilling
machines, milling machines.
– micro duty – e.g., micro-drilling machine etc.
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Classification of Machine Tools
Classification of Machine Tools
• According to precision:
– ordinary – e.g., automatic lathes
– high precision – e.g., Swiss type automatic
lathes
• According to number of spindles:
– single spindle – center lathes, capstan
lathes, milling machines etc.
– multi-spindle – multispindle (2 to 8) lathes,
gang drilling machines, etc.
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Classification of Machine Tools
Classification of Machine Tools
• According to type of automation:
– fixed automation – e.g., single spindle and
multispindle lathes
– flexible automation – e.g., CNC milling
machine
• According to configuration:
– stand alone type – most of the conventional
machine tools.
– machining system (more versatile) – e.g.,
transfer machine, machining center, FMS
etc.
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Text Books
References
• Materials and Processes in Manufacturing,
by E. Paul DeGarmo, et al, Wiley
• Manufacturing Engineering and Technology,
by S Kalpakjian and Steven R Schmid, Pearson
• Machining Technology – Machine Tools and
Operations, by Helmi A Youssef and Hassan
El-Hofy, CRC Press
• Manufacturing Science, by A Ghosh and AK
Mallik, EWP
• Machining & Machine Tools, by AB
Chattopadhyay, Wiley
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