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• Introduction to Mechatronics.Mechatronics in
manufacturing -Mechatronics in products-Scope of
• Fundamentals of numerical control-advantages of NC
systems-Classification of NC systems-Point to point and
contouring systems-NC and CNC – Incremental and
absolute systems-Open loop and closed loop systems-
• features of NC machine tools-Fundamentals of
machining-Design consideration of NC machine tools-
Methods of improving machine accuracy and
productivity -Special tool holders
• The word "mechatronics" was first coined by Mr.
Tetsuro Moria, a senior engineer of a Japanese
company, Yaskawa, in 1969.
• Mechatronics may alternatively be referred to as
"electromechanical systems," or as "smart
• Mechatronics is centered on mechanics,
electronics and computing which, combined,
make possible the generation of simpler, more
economical, reliable and versatile systems.
• Mechatronics is “the synergistic integration of
Mechanical Engineering with Electronics and
intelligent control algorithms in the design
and manufacture of products process”.
• The Prime Example – Industrial Robots.
• Mechatronics can also be termed as
replacement of mechanics with electronics or
enhance mechanics with electronics. Eg- Fuel
Evolution of Mechatronics
• Primary Level : Integrates electrical signaling
with mechanical action at the basic control
level for e.g.fluid valves and relay switches
• Secondary Level : Integrates microelectronics
into electrically controlled devices for e.g.
cassette tape player.
Evolution of Mechatronics
• Tertiary Level : Incorporates advanced control
strategy using microelectronics, microprocessors
and other application specific integrated circuits
for e.g. microprocessor based electrical motor
used for actuation purpose in robots.
• Quaternary Level : This level attempts to improve
smartness a step ahead by introducing
intelligence ( artificial neural network and fuzzy
logic ) and fault detection and isolation ( F.D.I.)
capability into the system.
• Marketing: Signifies market research, identification of
user needs, information analysis and formulation of
• Manufacturing: Looks into process development,
production planning, material handling and quality
• Design: The concentration is on studying fundamental
aspects of sensors, actuators, control and integration
methods. Broadly the core of a mechatronics system
incorporates Mechanical,Electronics, Control and
Information system engineering.
Mechatronics: products and systems in
• Computer numerical control (CNC) machines
• Tool monitoring systems
• Industrial robots
• Advanced manufacturing systems
– a) Flexible manufacturing system (FMS)
– b) Computer integrated manufacturing (CIM)
Computer numerical control (CNC)
• CNC machine is the best and basic example of
application of Mechatronics in manufacturing
• Mechatronics based automation in these machine
tools has greatly reduced the human intervention in
manufacturing operation and improved the process
efficiency and product quality.
• CNC is the operation of a machine tool by a series of
coded instructions consisting of numbers, letters of the
alphabets, and symbols which the machine control unit
Tool monitoring systems
• Tool wear is a critical factor in productivity of a
Flexible Manufacturing Systems
• Nowadays customers are demanding a wide
variety of products.
• To satisfy this demand, the manufacturers’
“production” concept has moved away from
“mass” to small “batch” type of production.
• Batch production offers more flexibility in product
• FMS is a manufacturing cell or system consisting
of one or more CNC machines, connected by
automated material handling system, and all
operated under the control of a central computer.
Benefits of an FMS
• Flexibility to change part variety
• Higher productivity
• Higher machine utilization
• Less rejections
• High product quality
• Better control over production
• Just-in-time manufacturing
• Minimally manned operation
• Easier to expand
• Just-in-time (JIT) manufacturing is a
production model in which items are created
to meet demand, not created in surplus or in
advance of need. The purpose of JIT
production is to avoid the waste associated
• Computer-integrated manufacturing (CIM) is
the manufacturing approach of using
computers to control the entire production
• Parts handling
• Parts processing
• Product building
• Recognizing, sorting/separating the parts
• Picking and placing parts at desired locations
• Palletizing and de-palletizing
• Loading and unloading of the parts on
• Fundamentals of NC
• Advantages of NC
• Classification of NC
– PTP- Contour
– Incremental – absolute
– Open loop – closed loop
• Punched Card
Manufacturing Systems Evolution
• Construction of simple production machine started in
• Fixed automatic mechanisms and transfer lines for
mass production came along at this century
• Introduction to Numerical control NC in 1952
• The logical extension of NC – CNC
• Industrial robots were developed simultaneously with
• First commercial robot in 1961
• 1969 Mechatronics –
• FMS with CAD / CAM
Fundamentals of Numerical Control
• Fundamentals of Numerical Control
Definition – EIA
Electronics Industries Assoc.
• Numerical Control is a system in which
actions are controlled by the direct insertion of
numerical data at some point. The system
must automatically interpret at least some
portion of the data.
Types of Numerical Control
• Conventional Numerical Control (NC)
– Data is sent to the machine tool by means of
punch cards or tapes. The reader at the machine
performs no calculations or interpolations.
• Computer Numerical Control (CNC)
– The idea of computer numerical control is to
position a computer right at the machine tool.
• Part Program- Numerical data on a punched
• The block contains , in coded form , all
information for processing a segment of work
piece like Segment length, cutting speed,
• NC replaces the manual actions of the skilled
• Part Programmer V/s Skilled operator.
• APT – Automatically Programmed Tool
• BLU- Each unit corresponds to the position
resolution of axes of motion referred to Basic
• BLU is also known as ‘increment size’ or ‘bit
• The part dimensions are expressed in part
programs by integers
• To calculate position command in NC, the
actual length is divided by the BLU value.
• To move 0.7 inch in positive X direction , with
BLU =0.001, the position command is X+700
• Axis of motion – An axis in which the cutting
tool moves relative to the work piece.XYZ
• Machine tools- drilling,milling,lathe
• Rotary motions also possible.
NC machine parts
– Data Processing Unit
• To decode the information received from tape, process
it, and provide data to CLU
– Control Loops Unit.
• Operated Drive attached.
• Machine tool
Advantages of NC
• First NC- 1952.
• Accuracy- Measuring Time
• 70-80 % Time wasted on measurements
• Tolerance improved.
• A Further saving of time is achieved while passing
from one operation to another during the
machining of the work space.
• Rate of production decreases in conventional
• Contour cutting in 3 D or 2D can not
performed by manual operation
• Two Hand wheels required for this operation
CNC - Disadvantages
• High initial investment
• A long preparation time for each production
• Inflexibility of the process. Machine is planned
to make a certain fixed cycle of operation. If
the part configuration changed , The machine
adjustment must be rebuilt or altered.
• A big stock of parts is required for the process.
• NC in Flexible Manufacturing System
• Production in low quantity
• Eg . Aircraft
• Machines should be economical.
• When a new product required , only the part
program has to b chgange.
Advantages of NC
1. A Full flexibility ; a part pgm is needed for producing a
2. Accuracy is maintained through the full range of
speeds and feeds.
3. A shorter production time
4. Easy adjustment of the machine. Less time than other
5. The possibility of manufacturing a part of complicated
6. Need for highly skilled & Experienced labor is avoided
7. The operator has free time
Disadvantages of NC
• A relatively high cost
• More complicated maintenance- Special
maintenance crew is desirable.
• Highly Skilled & properly Traned part
programmer is needed
Classification of NC
• According to type
– Point to point / contouring
• According to Structure
– NC/ CNC
• According to programmed method
– Incremental / absolute
• According to type of control loops
– Open loop / closed loop
• Drilling machine
• Work piece is moved along axis of motion
until center of hole is drilled is exactly beneath
• Drill is automatically moved to the work piece,
hole is drilled , and the drill moves out in a
rapid traverse speed.
• In countering or continuous-path systems, the
tool is cutting while the axis of motion are
• Eg. milling machine
• Interpolator contained in the DPU of
contouring systems provide the proper
velocity commands for each axis.
Straight Cut Systems
• PTP machine equipped with milling tool.
NC & CNC
• NC- Hard ware based
• CNC- software based
• The digital control in NC employs voltage
• 1 pulse = BLU (NC)
• Pulses to actuate motors.
– Stepper- open loop
– DC motor – closed loop
• 1 bit = BLU (CNC)
• Simplest hardware configurations – emulates
hardware based NC and transmit output pulse.
• 1 bit =1 pulse =BLU
• The main difference in the operation between NC
and CNC is in the way that the punched tape is
– NC – read 1 block and cut
– CNC – store complete data , stored in memory before
Absolute - Advantages
• With an incremental system , each time the
work is interrupted the operator must restart
the part pgm and repeat the entire operation
• Dimensional data can change at any time.
• One reference point
Incremental - Advantages
• Inspection of the part pgm is easy. Sum of
position commands must be zero
• The performance of the incremental system can
be checked by a closed-loop tape. This is a
diagnostic punched tape which test the various
operations and performance of the NC Machine
• Mirror image programming is facilitated with
incremental systems. The sign of the
corresponding position commands is changed
from + to - . No new calculation required for the
• Fundamentals of machining
• Design Consideration of NC Machine Tools
• Method to increase accuracy and
• Special Tool Holders
Encoder A/C Motor
Input (converted from analog to digital value)
Fundamentals of machining
• Machining is the manufacturing process in
which the size, shape or surface properties of
a part are changed by removing excess
• High Accuracy and good surface finish are
Basic machine Tool
• Lathe or turning machine
• Drilling or boring machine
• Milling machine
• Shaper or planer
• Chemical – Electro Chemical machining(ECM)
• Electrical – electrical discharge machining
• Thermal – laser beam machining.
Metal removal rate
• Cutting speed
• Size of cut
Cutting Speed (v)
• Cutting speed defined as the relative velocity
between cutting tool and work materiel.
• Unit- feet per minute , meters per minute
• NC- Spindle speed (angular velocity of work
piece , rev/min)
• Spindle speed N= 12v/∏D
• D average diameter in inches
Depth of cut (d)
• Defined as the distance the cutting tool
projects below the original surface of the work
• Expressed in thousandths in an inch or in
• Defined as the relative lateral movement
between tool and work piece during the
• Inches per revolution , mm per revolution
• Milling operation- length units per tooth –
inches per tooth, mm per tooth
• NC machine- length per minute- feed rate.
• Feed rate – feed X spindle speed
Metal removal rate
• The product of proper speed feed, and depth
of cut determines the metal removal
• Volume – units per minute.
• Productivity of the machine during cutting is
proportional to MRSR
Design Consideration of NC Tools
• Better Accuracy to increase productivity
• Design Control techniques and computers
have undoubtedly contributed towards
achieving these goals.
• The term accuracy is often mistakenly
interchanged with the terms resolution and
• Resolution mainly dependent on position
– Programming Resolution – smallest allowable
position increment (BLU)
– Control Resolution- smallest change in position
that the feedback device can sense.
– Eg assume that an optical encoder which emits
1000 voltage pulses per revolution of shaft is
directly attached to 10 mm pitch lead screw . This
encoder will emits one pulse for each 0.01 mm.
the unit 0.01 is control resolution
• To obtain the best systems accuracy programming
resolution is equal to control resolution(System
• Accuracy also depends on computer control
algorithms, system resolution and machine
• System in accuracy due to resolution is usually
considered to be ½ BLU. Since displacement
smaller than 1 BLU can be neither programmed
nor measured .
• System accuracy = ½ BLU + machine accuracy
• The machine designer tries to ensure that
accumulated effect of all in accuracies
associated with machine tool will be under ½
Methods of Improving Machine
• Tool Deflection & Chatter
• Lead screws
• Thermal Deformations
Tool Deflection & Chatter
• The force of the tool edge against the work
piece in milling & turning deflects the tool and
tool holder and causes dimensional error.
• This error can be removed by increasing
stiffness of the construction of tool mounting
• Chatter -Vibratory response due to tool
• If cutting tool deflects at one more than
average, and as result a lump is left on the
workpiece at the point .
• Chatter occurs as a function Of the machine
structure, too, workpiece material, and cutting
• In accuracies due to mechanical linkage
between leadscrew and the tool.
• In order to improve the accuracy , this
mechanism must be time in varient ( no
heating effect) and linear ( no backlash and
• Sources of heat
– Marching process
– Spindle and driving motors
– Friction of slideways & lead screws
• A temp difference of 1˚C along 1000 mm can
cause an error of 0.01 mm
• Machine tool manufacture must take the
thermal effects into considerations in design
stage of the machine.
• It can avoid by removing hi-power motor,
providing large heat removing surface, use of
low friction bearings,symmetrical distribution
of heat sources.
• Heat effect can not completely removed
• Precise machining are always located in an air-
conditioned environment or separate room
Increasing Productivity With NC
• Actual cutting time
• idle and traverse motion time
• Loading and unloading time
• Tool changing time
Special Tool Holders
• A substantial saving in time is obtained with
automatic tool changing methods.
• For simple turning and drilling operations, six
or eight tools may be adequate, and this
restricted number would enable the use of
simple turret machine.
• Turret is not regarded as an ATC
• An ATC is an device containing a rotating tool
storage with an automatic exchange of tools
at the spindle.
• The Tools are available for automatic selection
• Eg – Chain type, carousel type magazine.
• Most ATC have a changer arm to exchange
tools between magazine and machine spindle.
• The changer arm rotates 90 degree and engages the
tools in the spindle and magazine simultaneously.
• The arm grips the tools mechanically, Move forward to
remove tools from the socket.
• The changer arm continuous the rotation with the two
tools to change the position of the tools by 180
• The arm retracts back to the machine column and
places the selected tools in machine spindle and the
used tool in spindle.
• The arm rotates an additional 90 to its rest position,
while machining operation resumes.