Design Components of Manufacturing Automation

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Design Components of Manufacturing Automation
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Computer-aided Design CAD

• New parts or alterations to existing parts are
  designed by means of computer
• Definition- the application of computers and
  graphics software to aid or enhance product
  design from conceptualization to documentation
• many organizations, CAD is usually introduced as
  a separate entity

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• CIM integrates together CAD and all other
  databases for the organization
• Summary of history - See automation timeline
• Basic CAD system would consist of
• input devices - e.g keyboard, mouse
• processing and storage - CPU, storage devices
• output devices - monitor, plotter
• Hardware - used to develop, store and display the
  geometrical part shapes
• Object stored as geometric and graphical
  parameters for lines, arcs and curves

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• When object is loaded in the computers active
  memory for display it is put in a bitmap, but can
  be stored in vector format - regenerated to
  bitmaps for display
• Software
• Two broad categories - 2D and 3D
• Numerous software available commercially - e.g.
  AutoCAD, Pro/ENGINEER, CATIA, I-Deas
• CAD software will normally translate data
  for/from different file formats and inputs - i.e.
  systems linked through CAE so that different
  applications can share information in the
  database

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• Because of the diversity in the various CAD
  platforms, a need for exchange of data exists -
  Initial Graphics Exchange Specification (IGES)
  format allows for this.
• Types of CAD Hardware
• Mainframes
• powerful, multiple program execution, good
  support and response for large drawings and
  designs
• large initial cost, requires large number of
  users to maintain low cost per terminal, complex
  OS, single failure can terminates all work

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• RISC platforms (workstations)
• lower cost, good performance ratio, multiple
  program execution
• requires multiple copies of CAD software, UNIX
  rather complex
• PC platforms
• cheap, simple OS
• more difficult to integrate into CIM, lower
  capability, cannot support complex or multiple
  designs easily.

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• The CAD process involves
• a) Geometric Modeling - description of a
  physical object or part mathematically. Models
  can be represented in 2D (as lines) or in 3D
  (lines, wire frames, surfaces or solids)
• b) Design Analysis and optimization performing
  an engineering analysis such as FEA on the model.
  Experiments may be required
• c) Design Review and evaluation
• d) Documentation and drafting hard copies,
  specifications, coding

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• CAD model representations

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• Current trends in CAD involve
• workgroups in which different groups
  concurrently design different aspects of the
  product while sharing the data in real time
  Concurrent or Simultaneous engineering (Example
  Airbus Consortium)
• product development management applications
  involving the Internet CIM applications.

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Selection of CAD hardware and software -
considerations

• Type and complexity of drawings involved
• degree of axysymmetry, curved surfaces, interior
  complexity, parts in assembly
• Concept vs Repetitive Design
• for repetitive 2D often sufficient concept might
  require more modelling
• Size and complexity of product

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• Enterprise Data Interfaces
• data available for product brochures and manuals
  easily, ease of CNC code generation, ease of PPC
• External Data Interface
• electronic data interchange(EDI), type EDI
  between contractor and vendor, transferrability
  of data