Arab Academy for Science, Technology,

and Maritime Transport

Manufacturing Processes (IM 212)

Department of Industrial & Management Engineering

College of Engineering and Technology

Lecture 11

CNC Machine Tools

&

Nonconventional Machining

1

Computer Numerical Controlled

Machine Tools

Manual Machine Tools

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CNC Machines

Numerical control (NC):

▪ The term used to describe the control of machine movements and

various other functions by instructions expressed as a series of

numbers and initiate via electronic control system.

Computer numerical control (CNC):

▪ The term used when the control system includes a computer.

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CNC Machines

5

CNC Machines

6

Advantages of NC

▪ Greater flexibility: through program changes can be made

rapidly, and design changes to parts can be made rapidly

through minor changes to the part program.

▪ Elimination of templates, models, jigs, and fixtures: The NC

control program takes over the job of locating the cutting tools.

▪ Easier setups: By using more simple work holding and locating

devices, the operator does not have to set table limit stops or

dogs or depend on the feed screw dials when setting up for

machining.

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Advantages of NC

▪ Reduced machining time: Machining with NC provides the use

of a wider range of speeds and feeds than conventional

machine tools. Optimum selection of feed rates and cutting

speeds is ensured. The NC equipment can also move from one

cutting operation to the next faster than the operator which,

significantly, reduces the total machining time.

▪ Greater accuracy and uniformity: No human errors are

possible and machining the same part is performed in the same

way through the stored tape/program. Hence, scrape and

rework are greatly reduced or completely eliminated by using

NC.

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Advantages of NC

▪ Greater safety: The operator is not as closely involved with

the actual machining operations as in case of the

conventional machine tools.

▪ Conversion to the metric system: NC system can be

converted to accept either inch or metric inputs.

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Disadvantages of NC

▪ NC machines costs 5 to 10 times than conventional

machines of the same working capacity.

▪ NC follows programmed instruction that may lead to

machine destruction if they are not properly prepared.

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Disadvantages of NC

▪ The skill required to operate an NC is usually high. (Part

programmers, tool setters, punch operators, and

maintenance staff that are more educated and well trained

than conventional machine operators)

▪ Special training for personnel for the software and hardware

is very important.

▪ NC requires high investments in terms of wages of highly

skilled personnel and expensive spare parts.

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CNC Machines

Example of NC motions12

CNC Machines

Example of NC motions13

Axes of CNC Machine Tool

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CNC Machines

CNC Machines

1. CNC drilling machines

2. CNC milling machines

3. CNC turning machines

4. CNC machining centers

5. CNC turning centers

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CNC Machines

CNC drilling16

CNC Machines

CNC milling 17

CNC Machines

CNC turning18

CNC Machines

CNC machining center 19

CNC Machines

CNC turning center20

Nontraditional Machining

Processes

Why Non-traditional Machining?

Traditional machining drawbacks:

▪ The high cost due to the large energy used to remove a

unit volume from the workpiece material.

▪ Workpiece distortion due to the heat generated during

cutting and abrasion.

▪ Undesirable cold working and the residual stresses

which may require post processing to remedy their harmful

effects.

▪ Limitations related to the size and complexity of the

workpiece shape.

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Ultrasonic Machining

Tool

Workpiece

Oscillation + feed Abrasive slurry

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Water Jet Machining

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Electrochemical Machining

Workpiece (+)

Tool (-)

ECM

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ECM Samples

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Laser Beam Machining

Laser beam

Workpiece

Molten metal

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