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					Intro to NC Machining




   A Cuyler , Baehr Production!
What is this NC Machining All about?
                What is it?
           How can it be set up?
             Let’s take a look.
         NC-Numerical Control

 A Programmed path is loaded into a machine
then executed by a series of codes the machine
               can understand.
    CNC- Computer Numerically
           controlled

A Dedicated Computer acts as the controller
              for each tool.


 Computer         Computer         Computer



 Machine           Machine         Machine
  Tool              Tool            Tool
   DNC- Distributed Numerically
            controlled

 One central Computer controls all other
   Machine Tools on the factory floor.


                  Central
                 Computer


Machine    Machine      Machine    Machine
 Tool       Tool         Tool       Tool
Which type of NC system do we
         use in class?
     Goals of NC Machining

1. Increase Production

2. Improve the Quality and Accuracy of parts

3. Stabilize Manufacturing Costs

4. Manufacture and assemble complex parts quickly
     Timeline of NC Machining
Single items produced by craftspeople

Eli Whitney (Cotton Gin) - Interchangeable Parts

Engineer designed parts for production (tolerances)

WW II - development of servo motors (electrically aimed
guns) Military products created the need to produce
precision quickly and accurately.

Servo motors applied to machine tools as a result.
        Timeline Continued
1945- University of Pennsylvania- ENIAC to assist
    with Engineering calculations.

1945- Parsons corporation awarded USAF contract

1952- Parsons corporation subcontracted with MIT
    to develop first NC machine.

1960’s- NC machines become affordable and
    common in industry to produce parts.
         Timeline Continued
1970’s- Programs stored on Punch tapes and
    Cards. Programmable controllers replace
    relays.                                Punch Tape

1980’s- Computer assisted Part Programming-
    computer is used for translating data and
    performing necessary calculations, creates
    punch tape.
1990’s- CNC And DNC become widely used in
    industry. Punch cards become obsolete.

Currently 85 percent of machine tools
    produced are run by CNC.
ENIAC
        First NC Machine at MIT




Today
Advantages Of CNC
  Increased productivity after programming is
  completed

  Reliability - reduces human error

  Often eliminates need for special jigs and
  fixtures

  Makes possible the machining of complex
  shapes requiring simultaneous 3 axis motion
Advantages
  Single part and production runs can be
  programmed and machined with minimum
  effort and cost.

  Programs can readily be altered and re-run

  Reduced inspection costs (more reliable)

  Once programming, setup and verified the
  equipment can be operated by a less skilled
  operator.
Disadvantages
 Initial cost of CNC machine tools

 Servicing of equipment

 Larger machines require more space

 Personnel must be trained in the programming
 and operation of this equipment.
All videos Copywrite CNC Workshop
   Addison Wesley Longman 1999
Definitions
 FMS
   Fixed Manufacturing Systems-
   An automated process that can not be
   reprogrammed. The system is most likely
   replaced.

   Flexible Manufacturing System-
   An automated system that can be reprogrammed
   and broken apart to complete other tasks. This
   type of system is initially expensive but pays off
   in the long run.
Definitions
    NC - A method of accurately controlling the
    operation of a machine tool by a series of
    coded instructions, consisting of numbers,
    letters of the alphabet, and symbols that the
    machine control unit can understand.

    MCU - Machine Control Unit - decodes NC
    codes to drive and monitor servo motor
    movements.
Definitions
     CAM Package: (Computer Aided
     Manufacturing) A software solution capable of
     generating NC code from assigned tool paths
     applied to part geometry.

     Control Systems
       Open loop system - servo motor driven by pulses
       without feed back encoders.
       Closed loop system - servo motor is driven by
       electrical pulses. An encoder provides feedback to
       verify machine movements.
Punched Paper Tape

				
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