NC CNC DNC - A K Mansuri

Program: B Tech(Mechanical)
Class: SE
Course: Manufacturing Process-2
Unit: NC CNC DNC Concepts,
Machining Center
CNC Programming ATC
School of Engineering and Technology

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www.sandipuniversity.edu.in
1. Prof Arif K Mansuri
2. Years of Experience:-24
3. Domain Expertise:-Advance Production Systems
SCHOOL OF ENGINEERING AND TECHNOLOGY

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History of NC/CNC/DNC
YEAR WORK
1949 US Air Force asks MIT to develop a "numerically controlled" machine
1952 Prototype NC machine demonstrated (punched tape input)
1980 CNC machines (computer used to link directly to controller)
1990 DNC: Remote/external computer control programmer to machine tool controller

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Numerically Controlled (NC) Machine Tools
• Numerical Control is a system in which actions are controlled by the
direct insertion of numerical data at some point.
• In other words, Programmable automation in which the mechanical
actions of a ‘machine tool’ are controlled by a program
• It is defined Method of programmable automation in which various functions
of machine tools are controlled by numbers, letters and symbols.

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Basic NC Machine Tool Components
PART
DRAWING
&
PART
PROGRAM
PUNCHED
TAPE
MACHINE
TOOL
MCU

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1. Part program:-
• Using the part drawing and the cutting
parameters, the part program is written.
• The part program is a set of step by instruction
to the machine tool for carrying out the
operation.
Method use for part programming
a)Manual part programming
b)Computer-aided part programming

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2. Program Tape:-
• The part program is entered on the program
tape.
• The program is entered on the tape in
the form of punched holes. The holes are
punched with the help of punching machine.
3. Machine Control Unit(MCU):-
• The program tape is read by the tape reader.
The controller takes input from the tape
reader.
4. Machine Tool:-
• The machine tool is operated
by the controller of the machine control unit.

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Video

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COMPUTER NUMERICAL CONTROL (CNC)
A system in which action are controlled by
the direct insertion of numerical data at some point. The
system must automatically interpret at least some
portion of this data.
 It is a versatile system that allows you to control the
motion of tools and parts through computer programs
that use numeric data.
 CNC can be used with any traditional machine.
Video

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What is the difference between NC and CNC ?
⚫The earliest NC machines performed limited functions and
movements controlled by punched tape or punch cards.
⚫As the technology evolved, the machines were equipped with
increasingly powerful microprocessors (computers) with the
addition of these computers, NC machines become CNC
machines.
⚫CNC machines have far more capability thantheir
predecessor.
⚫Some of the enhancements that came along with CNC
include: Canned Cycles,Sub Programming Cutter
Compensation, Work coordinates, automatic corner rounding,
chamfering

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NC/CNC Machines-Advantages
⚫High Repeatability and Precision e.g. Aircraft parts
⚫Volume of production is veryhigh
⚫Complex contours/surfaces can be machined. E.g. Turbines
⚫Flexibility in job change, automatic tool settings, less scrap
⚫More safe, higher productivity, better quality
⚫Less paper work, faster prototype production, reduction in lead times

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Classification of NC Machines
According to Tool Positioning or Modes of Programming

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Point to point system Straight line or straight cut
system
Continuous or contouring
path system
According to Motion Control System

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According to Servo Control System

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Direct Numerical control (DNC)
 Number of NC machines are
controlled by a central computer.
 Part program is transmitted to
machine directly from computer
memory
 The system designed in such a way
that, on demand it will provide
instruction to each machine tool.
Machine
Tool
Machine
Tool
Machine
Tool
Machine
Tool
Telecommunication
lines
Bulk
memory
NC
program
Central computer
 Central computer
 Bulk memory, which stores
the NC part program
 Telecommunication lines
 Machine tool

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DNC system without satellite computer

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DNC system with satellite computer

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1. A central computer connected to a number of machine tools and
control them
2. Part program of all machine tools are stored in the memory of the
central computer and transmitted on direct transmission lines on
demand
3. Two way information flow take place in real time
4. Various machine tools can communicate with the computer in real
time
5. Programs in full or segment can be transferred to NC
machines
6. Computer can be used for program editing
7. No tape readers are used
8. No limitation for the number or size of programs stored
DNC

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Types of DNC systems:
1.Behind the tape reader (BTR) System
1.In this arrangement , the computer is linked directly to the regular NC control unit.
2.The replacement of the tape reader by the telecommunication lines to the DNC computer is
what gives BTR configuration
3.The connection with the computer is made between the tape reader and the controller unit behind the
tape reader.
4.The controller unit uses 2 temporary storage buffers to receive blocks of instructions from the DNC
computer and to convert them into machine actions.
5.While one buffer is receiving a block of data , the other is providing control instructions to the
machine tool

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Types of DNC systems:
2.Special machine control unit (SMCU) system
1.In this arrangement , a special machine control unit completely
replaces the regular NC controller.
2.This special MCU is a device that is specially designed to facilitate
communication between the machine tool and the computer.

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DNC
 Control of more than one NC machine
 Elimination of punched tape and tape reader
 Convenient storage of NC part program in computer files
 Greater computational capability and flexibility
 The data for tools and cutters can be centrally maintained and updated.
 Inventory can be better controlled
Advantages
 The major disadvantage of DNC system is that, if the central computer
goes down, all machines become inactive.
 Initial cost is too high
Disadvantages
Video

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Machining Center
 They are capable of carrying out milling, drilling,
reaming, tapping, boring etc.
 They do not need operator intervention for
change of tools and workpiece.
 Machining centers are equipped with automatic
tool changers (ATC). A machining center is
characterized by an indexable tool magazine which
can store several tools. Tools from tool magazine is
transferred by tool changing arm to the machine
spindle.

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Machining Center
Horizontal Machining Center Video
A HMC is used for cube shaped
parts. Rotary table used in HMC
for machining all four faces.

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Machining Center
Vertical Machining Center
In CNC vertical machining center, the work
piece is held on the table base and the
spindle which contains the cutting tool is
fixed on vertical Z axis. The table moves in X
and Y axis and spindle with cutting tool
moves in Z axis. It is used for flat work that
requires tool axis from the top.
Ex: Mould and die cavities,
components of aircraft.

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Features of Machining Center
• Automatic tool changer (ATC)
• Automatic Work positioning (AWP)
• Automatic pallet changer (APC)

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Automatic tool changer (ATC)
A tool magazine where sufficient
number of tools can be stored (16-80)
and is integrated with the machine tool.
When cutter needs to changed, the tool
drum rotates to proper position and ATC
operating under program exchanges tool
in the spindle for the tool in the tool
storage unit

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Automatic tool changer (ATC)
Video

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Automatic Work positioning (AWP)
Many horizontal and vertical machining
centers have the capability to orient the
work part relative to the spindle. This is
accomplished by means of a rotary table
on which work part is fixed. The table can be
oriented at any angle about a vertical axis to
permit the cutting tool to access almost
entire surface of the part in a single setup.
Various planes possible by the 2-axis rotary table with a HMC

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Automatic pallet changer (APC)
Machining centers are often equipped with
two or more separate pallets that can be
presented to the cutting tool using
automatic pallet changer. While machining is
performed with one pallet in position at
machine, the other pallet is in a safe
location, the operator can unload the
finished part and the fixes the raw work part
on pallet for next cycle. Video

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Types of CNC control units
Fuji Automatic Numerical Control (FANUC)
FANUC CNC (American) provides the answer to demanding machining operations
involving multiple axes and multiple path applications. From very small to very large
work pieces, from very soft to very hard materials, FANUC CNC provides the ideal
balance between utmost precision, flawless surface quality and the shortest possible
cycle times. This translates into less non-productive time and eliminates the
inaccuracies incurred in multiple-part set-up operations.
Each controller model is typically available with several device control capabilities,
depending on what software functions are licensed for use on that device. Some
common control capabilities are: M – Milling T - Turning (lathe) TT - Twin Turret P -
Punch press G - Grinding.

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SINUMERIC (SIEMENS) CONTROLLER
Sinumeric is the first German brand for CNC controller
• as of 2009: The operating software Sinumeric Operate combines programming according
to DIN 66025 and workshop programming (ShopMill and ShopTurn) in the same user
interface.
• 2009: Compact CNC in technological design for turning and milling machines up to 8 axes
- SINUMERIC 828D
• 2011: Bundling competence around the energy efficiency of machine tools -
SINUMERIC Ctrl-Energy
• 2012: Entry-level CNC in technological design for turning and milling machines up to 3 axes
- SINUMERIC 808D
• 2020: SINUMERIC 840D 5 axes machine center
Types of CNC control units

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Programming is telling the machine by ‘command data’
through numerical control for its working of components.
Or
NC programming where all the machining data are
compiled and where the data are translated into a
language which can be understood by the control system of
the machine tool.
The machining data is as follows
a. Machining sequence, classification of process, tool startup point, cutting
depth, tool path etc
b. Cutting condition spindle speed, feed rate, coolant, etc
c. Selection of cutting tool
CNC Programming

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Programming consists of a series of instructions in form of
letter codes:
 N codes- specify program line number to executed by the MCU
 Preparatory Codes: G codes- Initial machining setup and
establishing operating conditions
 Axis Codes: X,Y,Z - Used to specify motion of the slide along X,
Y, Z direction
 Feed and Speed Codes: F and S- Specify feed and spindle speed
 Tool codes: T – specify tool number
 Miscellaneous codes – M codes For coolant control and other
activities
CNC Programming

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Word address format (WAF) -ISO Standard
CNC Programming
Word Address Format
This type of tape format uses alphabets called address, identifying the function of
numerical data followed. This format is used by most of the NC machines, also called
variable block format. A typical instruction block will be as below :
N20 G00 X1.200 Y.100 F325 S1000 T03 M09 <EOB>
or
N20 G00 X1.200 Y.100 F325 S1000 T03 M09;
The MCU uses this alphabet for addressing a memory location in it.

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A program block is a combination of functions of
machine tool in a single line.
Example: N01 G01 G91 X0.0 Y10.0 S2000 F100 M03 ;
SEQUENCE
NUMBER
END OF BLOCK
Line number is optional
End of block is mandatory
CNC Programming

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 Designated by alphabet N
 Used to identify the blocks
 Not mandatory
 Occupies memory
 Can be used for each process
rather than for each block.
Sequence Number Spindle Speed Function
The spindle speed can be specified by a S code followed by a
Numerical value (rpm).
Syntax :S ; ;
Example : S2000 ;
Usually S command is associated with M03 or M04 to
specify the direction of rotation CW or CCW
CNC Programming

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CNC Programming
Feed Function
The feed can be specified by F code followed by a
Numerical value (feed per minute or feed per
revolution).
Syntax :F ;
Example : G98 F100;
: G99 F0.15;
G98 and G99 are preparatory functions to
specify feed per minute and feed per revolution
respectively.
Tool selection
A 2 digit or 4 digit numeric followed by a T code is
used to select the required tool.
Syntax T
Example T0303; Selects tool 3 with offset No.03
T0313; Selects tool 3 with offset N0.13

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CNC Programming
G00 Rapid Transverse
G01 Linear Interpolation
G02 Circular Interpolation, CW
G03 Circular Interpolation, CCW
G17 XY Plane,G18 XZ Plane,G19 YZ Plane
G20/G70 Inch units
G21/G71 Metric Units
G40 Cutter compensation cancel
G41 Cutter compensation left
G42 Cutter compensation right
G43 Tool length compensation (plus)
G44 Tool length compensation (minus)
G49 Tool length compensation cancel
G80 Cancel canned cycles
G81 Drilling cycle
G82 Counter boring cycle
G83 Deep hole drilling cycle
G90 Absolute positioning
G91 Incremental positioning
G Codes (Preparatory codes)

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Rapid Positioning (G00)
Linear Interpolation (G01)
Circular Interpolation (G02) CW
Circular Interpolation
(G03) CCW
Cutter Compensation (G40)

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CNC Programming
M Codes (Miscellaneous codes/Auxiliary Functions)
M00 Program Stop Temporary stop of program
M01 Optional Stop Temporary stop of program ( Optional Stop )
M02 Program end Program end and reset
M03 Spindle normal rotation Clockwise rotation of spindle
M04 Spindle reverse rotation Counter clockwise rotation of spindle
M05 Spindle Stop Spindle rotation stop
M06 Tool Change ATC Cycle start
M08 Coolant ON Coolant Discharge
M09 Coolant OFF Coolant shut
M22 Index Forward Turret index clockwise
M23 Index Reversed Turret index counter clockwise
M24 Chuck open Opening of chuck
M25 Chuck close Closing of chuck
M30 Program end and rewind Program end and reset/rewind
M98 Sub-program call Call of a sub-program from a main program
M99 Sub-program end Return from a sub-program to a main program

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NC CNC DNC - A K Mansuri

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