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Computer Numerical Control
(CNC)
Banu Akar Neşe Kaynak
Duygu Gökçe Meltem Erdi
Hacettepe University
Chemical Engineering Department
22.12.2010

CONTENT
1. What are NC & CNC?
2. History
3. CNC system Elements
4. Properties of CNC machine
5. Types of CNC machines
6. CNC applications
7. Advantages& Disadvantages
8. Conclusion
9. References

What are NC & CNC ?
 Numerical control (NC) is a method of automatically
operating a manufacturing machine based on a code
letters, numbers and special characters.
 The numerical data required to produce a part is
provided to a machine in the form of program, called part
program or CNC (computer numerical control)

What are NC & CNC ?
 The program is translated into the appropriate electrical
signals for input to motors that run the machine.
 A CNC machine is an numerical control machine with
the added feature of an on board computer. The
computer is referred to as the machine control unit
(MCU)

HISTORY
 In 1775, John Wilkinson- cannon boring machine (lathe).
 In 1881, Eli Whitney- milling machine.
 In 1947, Mr. John Parsons began experimenting for
using 3-axis curvature data to control the machine tool
motion for the production for aircraft components.
 In 1949, parsons- first NC machine.
 In 1951, MIT was involved in the project.
 In 1955, after refinements NC became available in
industry
 Today, modern machinery are CNC milling machines
and lathes.

CNC SYSTEM ELEMENTS
A typical CNC system consists of the following six
elements
 Part program
 Program input device
 Machine control unit
 Drive system
 Machine tool
 Feedback system
Figure 1 : Schematic illustration of the major
components of a numerical control machine tool

Basic Concept of Part Programming
 Part programming contains geometric data about the part and
motion information to move the cutting tool with respect to the work
piece.
 Basically, the machine receives instructions as a sequence of blocks
containing commands to set machine parameters; speed, feed and
other relevant information.
 A block is equivalent to a line of codes in a part program.
 N135 G01 X1.0 Y1.0 Z0.125 T01 F5.0
Block number Coordinates
Special function
Tool number
G-code

Programming Methods
 Automatically Programmed Tools (APT)
 A text based system in which a programmer defines a
series of lines, arcs, and points which define the
overall part geometry locations.
 These features are then used to generate a cutter
location (CL) file.

Programming Methods
 Computer Aided Machining (CAM) Systems-
Computer Aided Design (CAD) Systems
 CAD/CAM systems allow for rapid development and
modifying of designs and documentation.
 The 3D geometric model produced becomes a common
element for engineering analysis (FEA), machining
process planning (including CNC part programming,
documentation (including engineering drawings), quality
control, and so on.

Drives of CNC machine tool
 Hydraulic actuator
- high power machine tool
 Stepping motor
- small machine due to limited power and torque
 DC motor
- excellent speed regulation, high torque, most widely
used

Properties of CNC machines
 Based on Motion Type: Motion control - the heart of
CNC
Point-to-Point or Continuous path
 Based on Control Loops:
Open loop or Closed loop
 Based on Power Supply:
Electric or Hydraulic or Pneumatic
 Based on Positioning System
Incremental or Absolute

Point-to-Point Tool Movements
 Point-to-point control systems cause the tool to
move to a point on the part and execute an operation
at that point only.
 The tool is not in continuous contact with the part
while it is moving.
 Examples: drilling, reaming, punching, boring and
tapping.
Figure 2 : http://www.tradekorea.com/products/cnc_machine.html

Continuous-Path Tool Movements
 Continuous-path controllers cause the tool to
maintain continuous contact with the part as the tool
cuts a contour shape.
 These operations include milling along any lines at
any angle, milling arcs and lathe turning.
Figure 3: http://kaymak06.50webs.com/cnc.html

Loop Systems for Controlling Tool
Movement
Schematic illustration of the components of (a) an open-loop and (b) a closed-loop control
system for a CNC machine.
Figure 4 : http://www.nd.edu/~manufact/MET%20pdf_files/MET_Ch37.pdf

Types of CNC Machines
 Lathe Machine
 Milling Machine
 Drilling Machine
The bench drill
The pillar drill
 Boring Machine
 Grinding Machine

CNC Mills

These machining centers use
computer controls to cut different
materials.

They are able to translate
programs consisting of specific
number and letters to move the
spindle to various locations and
depths.

Used to make 3D prototypes,
moulds, cutting dies, printing
plates and sights.
Figure 5 :http://huayucnc.win.mofcom.gov.cn/en/plate01/product.asp?id=24916

CNC Lathes

They cut metal that is often turning
at fast speeds.

CNC lathes are able to make fast,
precision cuts using indexable
tools and drills with complicated
programs.Normally, they cannot
be cut on manual lathes.

They often include 12 tool holders
and coolant pumps to cut down on
tool wear.
Figure 6 :http://www.automation-drive.com/cnc-lathe-machine

Turning Centers are capable of executing many
different types of lathe cutting operations
simultaneously on a rotating part.
Figure 7 : http://www.cnc-machining-center-yida.com/cnc-turning-center-bml-420.htm

CNC Grinders

Grinding metal process uses a
coated wheel that slowly
removes metal to create a
part.

Through the years, grinding
was done on a manual
machine, but with the advent
of CNC technology, the
grinding process has
advanced
Figure 8 :http://cnc-machine-center.blogspot.com/2008/09/cnc-surface-grinding-machine.html

CNC DRILLING
Drilling is commonly used for mass production. The drilling machine
(drilling press) is used to create or enlarge holes.
Drilling machine for different jobs;
The bench drill: For drilling
holes through raw materials such
as wood, plastic and metal
The pillar drill: A larger version
that stands upright on the floor.
As the bench drill, it can be used
to drill larger pieces of materials
and produce bigger holes.
Figure 9 : http://www.metalshopsolutions.com/

CNC Boring
 Process of enlarging an
existing hole or internal
cylindirical surface.
 This can be accomplished on
a lathe or a machine tool
specifically designed for the
process, such as a horizontal
boring machine.
Figure 10:http://cadcamcnccenter.com/cadcamthai/cnc/machine/108-what-is-cnc.html

Electrical Discharge Machines (EDM)
Wire EDM machines utilize a very thin wire (.0008 to .012
in.) as an electrode. The wire is stretched between
diamond guides and carbide that conduct current to the
wire and cuts the part like a band saw.
Material is removed by the erosion caused by a spark that
moves horizontally with the wire.
Figure 11: http://news.thomasnet.com/news/machinery-machining-tools/electro-discharge-machines

Laser Cutting Machines

The machine utilizes an intense
beam of focused laser light to cut
the part.

Material under the beam
experiences a rapid rise in
temperature and is vaporized.

Laser cuts with a minimum of
distortion, no mechanical cutting
forces.
Figure 12 :http://zaipul.wikispaces.com/file/view/01+Introduction+to+CNC+Technology.pdf

Specific tools to perform different
operations
Figure 13: http://users.isr.ist.utl.pt/~pjcro/courses/api0910/API_I_C5.pdf

Specific tools to perform different
operations
Figures 14: http://users.isr.ist.utl.pt/~pjcro/courses/api0910/API_I_C5.pdf

APPLICATION of CNC
MACHINES
 cutting
 drilling
 milling
 welding
 boring
 bending
 spinning
 pinning
 gluing
 sewing
 routing

Application of CNC in Some
Industries
 Automotive Industry
 Aerospace Industry
 Machinery Industry
 Electrical Industry
 Instrumentation Industry

Automotive Industry
Different Products
Figure 15:http://www.efunda.com/eds/company_details.cfm/id2/4846/pv/NO/cp/Zhejiang%2020Co

Aerospace Industry
Aircraft Turbine Machined by
5-Axis CNC Milling Machine
Figure 16: http://boeingcockpit.com/html

Advantages of CNC Machines
Ease of Use
 CNC machines are easier for beginners
 operation of several CNC machines at same time
 some CNC machines don’t need any operator
●call their operator in case of the emergencies.
High Efficiency
 operate almost continuously 24 hours a day, 365 days a
year

Expanding Options
 Expand the machine's capabilities with Software
changes and updates
No Prototyping
 New programmes provide elimination build a prototype,
save time and money
Precision
 Parts are identical to each other

Reduce Waste
 Reduce waste as errors allows minimize wasted
material.

Disadvantage of CNC Machines
Cost
CNC machinery:
 costs quite a lot more than conventional machinery
 does not eliminate the need for expensive tools
 expensive to repair

CONCLUSION
 CNC machines which are applicable any type of
processing
 manufacturing anything is identical in shorter time
 CNC machines provide many advantages
 many industries prefer using CNC machines

REFERENCES
 http://www.ehow.com/about_5415088_types-cnc-machines.html
 http://www.cncci.com/resources/articles/what%20is%20cnc.htm
 http://www.bracingsystemsinc.com/basic-motion-types-in-a-cnc-machine
 http://www.madehow.com/Volume-2/CNC-Machine-Tool.html
 http://dget.nic.in/lisdapp/Trade/syllabus/pdf/TTCNC.pdf
 http://users.isr.ist.utl.pt/~pjcro/courses/api0910/API_I_C5.pdf
 http://www.tradekorea.com/products/cnc_machine.html
 http://kaymak06.50webs.com/cnc.html
 http://www.nd.edu/~manufact/MET%20pdf_files/MET_Ch37.pdf
 http://huayucnc.win.mofcom.gov.cn/en/plate01/product.asp?id=24916
 http://www.automation-drive.com/cnc-lathe-machine
 http://www.cnc-machining-center-yida.com/cnc-turning-center-bml-420.htm
 http://cnc-machine-center.blogspot.com/2008/09/cnc-surface-grinding-machine.html
 http://cadcamcnccenter.com/cadcamthai/cnc/machine/108-what-is-cnc
 http://news.thomasnet.com/news/machinery-machining-tools/electro-discharge-machines
 http://zaipul.wikispaces.com/file/view/01+Introduction+to+CNC+Technology.pdf
 http://www.metalshopsolutions.com/
 http://www.efunda.com/eds/company_details.cfm/id2/4846/pv/NO/cp/Zhejiang%2020Com
 http://boeingcockpit.com/html
 http://www.westone.wa.gov.au/toolbox8/furniture/toolbox/shared/resources_mw/ask_expert
/tony/advantages.htm

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