Transcript double column grinding machine

Fig.1. Classification of manufacturing processes
Fig.2. Definition of Manufacturing
Fig.3. Classification of Machining Processes
Fig.4. First wooden lathe machine
Development of lathe machine (A brief history):
The ancient Egyptians used these rollers for transporting the required stones
from a quarry to the building site. The use of rollers initiated the introduction of the
first wooden drilling machine, which dates back to 4000 BC.
The first deep hole drilling machine was built by Leonardo da Vinci (1452–1519).
In 1840, the first engine lathe was introduced. Maudslay (1771–1831) added the
lead screw, back gears, and the tool post to the previous design.
Planers and shapers have evolved and were modified by Sellers (1824–1905)
.
Fitch designed the first turret lathe in 1845.
In 1818, Whitney built the first milling machine; the cylindrical grinding machine
was built for the first time by Brown and Sharpe in 1874.
The first gear shaper was introduced by Fellows in 1896.
 In 1879, Pfauter invented the gear hobber, and the gear planers of Sunderland
were developed in 1908.
General requirements of machine tools
Machine tool classifications
Machine tool includes the following elements
1.
2.
3.
4.
5.
6.
7.
A structure that is composed of bed, column, or frame
Slides and tool attachments
Spindles and spindle bearings
A drive system (power unit)
Work holding and tool holding elements
Control system
A transmission linkages
Stresses produced during machining which tends to
deform the machine tools or work piece are:
Both static and dynamic load affect
the machining
performance in finishing stage while the final degree of
accuracy is also affected by the deflection caused due to
cutting forces
Machine structure
Value addition in manufacturing:
Production engineering has two domains
1. Production or manufacturing process
2. Production management
Manufacturing process is
 Application of any existing manufacturing process and
system
 Proper selection of input materials, tools, machines and
environments
 Improvement of existing materials and processes
 Development of new materials, systems, processes and
techniques
All manufacturing processes, systems and techniques have
to be:
Technically acceptable
Technically feasible
Economically viable
Eco-friendly
Production management
Objectives:
 Reduction of manufacturing time
 Increase of productivity
 Reduction of manufacturing cost
 Increase in profit and profit rate
Principle of Machining
Requirements for Machining
Functional Principles of Machine Tools
For material removal by machining, the work and the tool need relative
movements and those motions and required power are derived from
the power sources(s) and transmitted through the kinematic system(s)
comprised of a number and type of mechanisms
The machine tool, in general produce two kinds of
relative motion;
(a) The primary motion is responsible for the cutting action and
absorbs most of the power required to perform the machining action
(b) The secondary motion or feed motion
The line generated by the primary motion (cutting motion) is called
Generatrix
The line representing the secondary motion (feed motion) is called
Directrix
Concept of Generatrix and Directrix
Shaping
Planning
(A) , Long straight cylindrical surface obtained by a circle (G) traversed in direction
(D)
(B) , Short cylindrical surface obtained by traversing a straight line (G) along a circular
path (D).
(C) and (D), Cylindrical surfaces by rotating a curved line (G) in a circular path (D)
Longitudinal turning
Transverse turning
CM: Cutting Motion
FM: Feed Motion
Principle of producing flat surface in shaping machine
Directrix formed by tangent tracing in plain milling
Tool-work motions and G & D in form milling
Tool-work motions and G & D in drilling
Two methods to produce new surfaces;
(a) Tracing method: The surface is obtained by direct tracing of the generatrices
(b) Generation method: The surface produced is the envelope of the genetartices
Example:
The plane and cylindrical surfaces are obtained by the tracing method
Final surface geometry is the envelope of the generatrices
Configuration of basic machine tools and their use
Schematic view of a center lathe
The common machining operations are done in center lathe
Schematic view of a shaping machine
Schematic view of a planning machine
Schematic view of a drilling machine
Schematic view of a milling machine
Some common Milling Operations
Cutting tool classifications
Single point: turning tools, shaping tools, slotting tools, boring tools
Double point: Drilling tool
Multi point: Milling cutters, broach tools, hobs (hobbing tools), gear shaping tools
etc.
Hobbing tool
Broach tool
A gear hob in a hobbing machine
Gear Shaping
The optimum tool geometry depends on;
(1) The workpiece material
(2) Machining variable
(a) Cutting speed
(b) feed
(c) Depth of cut
(3) Material of the tool point
(4) Type of cutting
A standard cutting tool
Tool Geometry:
Many factors that contribute to cutting tool efficiency are:
(1) The shape of cutting edge that remove excess material
(2) The correct selection of the type of cutting tool for the material to be
machined
(3) The correct choice of cutting speed and feed
(4) The proper setting of cutting tool relative to work
(5) The correct choice and proper application of coolants
Tool geometry is basically referred by some specific angles or slope of the salient
faces and edges of the tools and their cutting points.
Rake angle and clearance angle are most significant for all the cutting tools.
Rake angle and Clearance angle of cutting tool
Rake angle: Angle of inclination of rake surface from the reference plane
Clearance angle: Angle of inclination of clearance or flank surface from the
finished surface
Advantages and disadvantages of +ve, -ve and zero rake angles
Description of tool geometry and nomenclature
Tool Geometry Description
1. Tool-in-Hand System
2. Machine reference System-ASA system
3. Tool reference system
(a) Orthogonal rake system (ORS)
(b) Normal rake system-NRS
4. Work Reference System- WRS
Basic features of single point tool (turning) in Tool- in- Hand system
Only the salient features of the cutting tool point are identified or visualized.
There is no quantitative information, i.e., value of the angles
Machine reference system coordinates for a lathe
Machine reference system for Milling and Drilling machine
Planes and axes of reference in ASA system
The three planes of reference and coordinates are chosen based on the
configuration and axes of the machine tool concerned.
Plane of reference
R
X
Y
 R   X  Y
Reference plane; the plane perpendicular to the velocity vector
Machine longitudinal plane; plane perpendicular to reference plane and
taken in the direction of assumed longitudinal feed
Machine traverse plane; plane perpendicular to both reference plane
and machine longitudinal plane. This plane is taken in the direction of
assumed cross feed
Coordinates
XM
YM
ZM
X M  YM  Z M
Direction of longitudinal feed
Direction of cross feed
Direction of cutting velocity
Side
Front
Top
Tool angles in ASA system
Definition of rake angles
Definition of clearance angles
Definition of cutting angles
Nose radius: curvature of the tool tip. It provides strength to the tool tip and
better surface finish
Points to be noted:
The tool geometry specified in this system has no direct relation to the
mechanics of cutting.
From tool grinding point of view, this system specification is convenient
because of ease of determining the reference coordinates
ASA System Sequence
Back rake angle-side rake angle-end clearance angle-side clearance
angle-end cutting edge angle-side cutting edge angle-nose radius
Orthogonal system
Orthogonal system of specification is related to the behavior of cutting tools since
the geometry of chip formation is always analyzed with respect to the cutting edge
In this, reference planes are chosen from the considerations of tool operation on
the workpiece on the machine tools. The reference planes are three mutually
perpendicular planes but related to the position of the cutting edge
This is also known as ISO-old
Orthogonal Rake system
Planes and axes of reference
in ORS
These are taken in respect of the tool configuration
Tool angles in ORS system
Rake angles
Clearance angles
Cutting angles
Nose radius
All the angles except the orthogonal rake angle, are true angles
Auxiliary orthogonal clearance angle
ORS sequence:
Inclination angle-orthogonal rake angle-orthogonal clearance
angle (principal clearance angle)-auxiliary clearance angleauxiliary cutting edge angle-principal cutting edge angle-nose
radius
Normal Rake System (NRS)(ISO – new)
Why NRS ?
ASA has limited advantage and use as well as convenience of inspection
ORS does no reveal the true picture of the tool geometry when the cutting
edges are inclined from the reference plane
Basic difference between ORS and NRS:
In ORS, rake and clearance angles are visualized in orthogonal plane, where as in
NRS, those angles are visualized in another plane called NORMAL PLANE.
The orthogonal plane is always normal to the reference plane and cutting plane,
but the normal plane (for auxiliary cutting edge) is always normal to the cutting
edge
This is also known as International System
Reference planes in NRS
In this system, except the normal rake, the principal normal flank and auxiliary
normal flank angles, the remaining tool angles are defined in the same manner
as in the ORS.
Differences of NRS from ORS with respect to cutting tool geometry
Signature or tool designation in NRS:
Inclination angle- Orthogonal rake angle – Principal clearance (flank) angle –
Auxiliary clearance angle – Auxiliary cutting edge angle – Principal cutting edge
angle – Nose radius
In NRS system;
With this system of plane and axis (as discussed), all angles referred
are true angles and tool geometry is related to the mechanics of cutting
Tool grinding easy and the angles do not require any compensation or
correction while grinding
Both normal and orthogonal systems will give the same values for the
various tool angles for zero inclination angle
CONVERSION OF TOOL ANGLES
Purpose of conversion of tool angles from one system to
another:
Method of conversion
Conversion of tool angles by Graphical method – Master Line
principle
This convenient and popular method of conversion of tool angles from ASA to ORS
and vice-versa is based on use of Master lines (ML) for the rake surface and the
clearance surfaces.
Conversion of rake angles:
Where, T=thickness of
the tool shank
•Extend the rake surface along X plane and let meet the tool’s bottom surface (which
is parallel to  R) at point D ' i.e., at D in the plan view.
•Similarly , extend the rake surface along  Y and let meet the tool bottom surface at a
point B ' i.e., at B in the plan view.
•The straight line obtained by joining B and D is the line of intersection of the rake
surface with tool’s bottom surface which is parallel to  R .
•[If the rake surface is extended in any direction, its meeting point with tool’s bottom
plane must be situated on the line of intersection i.e., BD.
•The point C and A are obtained by extending the rake surface along  O and C
respectively up to the bottom surface, will be on the line of intersection, BD.
•The line of intersection, BD between the rake surface and a plane parallel to R is
called as master line of the rake surface.
Simpler form for conversion of tool
angles
Proof
From this Figure;
The conversion equation in matrix form,
Conversion of rake angles from ORS to ASA
Hints:
The conversion equation in matrix form,
Conversion of clearance angles from ASA system to ORS and vice versa
by graphical method
Master lines of flank surface
Simpler form for conversion of
tool angles
The above equations in matrix form
Conversion of clearance angle from ORS to ASA system
Conversion of tool angles from ORS to NRS
Concept of Work Reference System (WRS)
The above figure shows the relative velocity vector during turning
Depending on the direction of feed, the direction of the relative velocity
vector changes.
Under operation conditions, the reference axis changes and referred to as
tool-operating-in machine system.
Highlights of the reference systems
ASA System
ORS System
NRS system
Selection of tool angles
Rake angles
Rake angles are designed to cut on the principal cutting edge
The chip generated flows on the rake face
The rake face controls the direction of the resultant force on the tool.
With zero back rake angle or inclination angle, the chip flows parallel to the work
surface.
The rake angle influences the cutting force, power and the surface finish.
Flank (clearance) angles
Flank angles are provided to enable the sides of the tool to clear the workpiece
and not to rub against during cutting.
Flank angle should be as large as possible.
Higher flank angles are used for machining of softer materials.
Cutting edge angles
The auxiliary or end cutting edge is provided to clear the cutting edge from the
machined surface.
With the principal or side cutting edge angle, the tool first contacts the workpiece
some distance away from the tip and also increases the tool length in action during
cutting
MULTI-POINT CUTTING TOOLS
Milling Cutter
Geometry of a helical milling cutter
Feed/tooth = so, mm
Feed/revolution = soZ
Number of teeth = Z
Feed rate = soZN, mm/minute
a1 = so sinψ
A = approach of cutter
O = over run of cutter
LT = L+A+O
The cutter has helical cutting edge and is equivalent to an oblique tool.
The inclination angle is equal to helix angle of the cutter.
In plain milling, the helix angle is zero, i.e., the cutting edges are straight and is
equivalent to an orthogonal tool
Radial rake angle of cutters is equal to the back rake angle of single point tool.
Helical cutting edges are provided to obtain smooth cut since a helical cutter
remains in contact for a larger time than plain milling cutter for the same cutting
conditions.
[In plain milling cutters, the forces on the cutting edges rise from zero to
maximum value during tool engagement and then fall to zero during
disengagement.]
In helical cutters, depending on the tooth spacing, two or more edges may cut
simultaneously. This reduces the fluctuations in spindle torque and provide
smoother cutting.
The rake and flank angles are fixed from the same considerations as those for
the single point tools.
Twist drill
Drill bit nomenclature
Feed = s, mm/revolution
Feed/lip = s/2
Feed rate = sN, mm/minute
Depth of cut per lip = D/2 mm
Geometry of a twist drill
d = depth of cut
f = feed per revolution of the drill
t = uncut chip thickness