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• Workpiece

  • 5 basic features
  • Side C
• Solution

  1. Cut raw material from block stock with dimensions: 6.25 x 4.25 x 2.25 in

  2. 2 through holes on strip 1 interact with formation of angle α

  3. Slot in side C interacts with cutting of angle β

  4. Machining angle strip 1 first

  5. Machining angle strip 2 first

  6. Recommended process sequence

  
• Manual process planning


  Process planning entails human ability to interpret design and familiarity with manufacturing processes and equipment
• Industry may need more people than are actually available to do process planning
• Expertise and experience within a company will diminish over time, creating the need to document and capture that expertise
• Two process planners will never come up with the same process plan for the same item
• Computer Aided Process Planning (CAPP)

  Implemented methodology of process planning in software package<|>Includes all process planning activities to realize design of process plan<|>Solves planning activities like selection of machining operations, machine and cutting tools<|>Prepares route sheet for engineering drawing<|>Interprets part in terms of manufacturing processes to be used<|>Input from CAD system, output to CAM system
• CAPP approaches

  • Variant (Retrieval)
  • Generative
  • Semi-generative (Hybrid)
• Variant (Retrieval) CAPP


  Parts grouped into families by manufacturing characteristics<|>Standard process plan established for each family<|>Retrieved for new parts in that family<|>Editing may be required for slight differences
• Generative CAPP


  Computer creates individual process plan from scratch automatically<|>Employs algorithms to make technical and logical decisions<|>Inputs comprehensive part description, not existing plans
• Computer Numerical Control (CNC)


  A computer that is joined to the NC machine to make the machine versatile. Information can be stored in a memory bank. The program is read from a storage medium such as the punched tape and retrieved to the memory of the CNC computer.

  
• Advantages of CNC

  • Increased productivity
  • High accuracy and repeatability
  • Reduced production costs
  • Reduced indirect operating costs
  • Facilitation of complex machining operations
  • Greater flexibility
  • Improved production planning and control
  • Lower operator skill requirement
  • Facilitation of flexible automation
• Limitations of CNC

  • High initial investment
  • High maintenance requirement
  • Not cost-effective for low production cost
• Elements of a CNC system

  • Input device
  • Machine Control Unit (MCU)
  • Machine tool
  • Driving system
  • Feedback devices
  • Display unit

  
• Driving System

  1. Open loop systems

  2. Closed loop systems
• Types of CNC machines

  • CNC laser cutting machine
  • CNC Lathe Machine
  • CNC Milling Machine
  • CNC router Machine
  • CNC Plasma Cutting Machine
  • axis machine
  • 3-D Printer
  • Pick and Place Machine
• Numerical control (NC)


  A method of automatically operating a manufacturing machine based on a code of letters, numbers, and special characters

  
• NC machine programming

  1. Written instructions converted into a hole pattern on tape

  2. Tape reader reads hole pattern and converts to electrical signal code

  3. Controller receives electrical signal code and causes NC machine to respond

  4. NC machine executes required motions to manufacture a part
• NC machine tools

  • One or more functions may be automatic: starting/stopping spindle, controlling spindle speed, positioning/guiding tool tip, controlling feed rate, changing tools
• Purpose of a machine tool

  • Cut away surplus material to leave a work piece of the required shape and size, produced to an acceptable degree of accuracy and surface finish
  • Able to hold work piece and cutting tool securely
  • Sufficient power to enable tool to cut work piece material at economical rates
  • Capable of displacing tool and work piece relative to one another to produce required work piece shape, with precision to ensure desired accuracy and surface finish
• Computer Numerical Control (CNC)


  Characterized by availability of dedicated computer and enhanced memory in controller, providing additional capabilities over traditional NC

  
• Additional capabilities of CNC over traditional NC

  • Part program storage memory
  • Part program editing
  • Part program downloading and uploading
  • Part program simulation using tool path
  • Tool offset data and tool life management
  • Additional part programming facilities
  • Macros and subroutines
  • Background tape preparation
• The controls with the machine tools these days are all CNC and the old NC control do not exist anymore