The Mechanics of Verification Labels and Direct Part Marking

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The Mechanics of Verification(Labels and Direct
Part Marking)

• DoD Part Marking AIT Forum
• Sponsored by AF AIT PMO and
• DOD Logistics AIT Office
• St. Louis MO
• 9-10 December 2003
• Glenn Spitz, President
• Webscan, Inc.

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Data MatrixWhat is it?

• 2 Dimensional Bar Code
• data is encoded in two dimensions
• Small size
• .15 sq.
• Secure Data
• Error Detection/Correction
• Expands to pack a larger amount of information

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Quality and Readability

• Scanners vary in capabilities.
• How can we ensure that a symbol can be read by
  all scanners?
• International DM quality standards exist for this
  reason - ISO 15415
• Incoming Quality Control should verify bar codes
  to this standard

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Scanner vs Verifier

• Scanners are optimized differently
• Scanners ONLY report data content
• Reading Range
• Contrast Range
• Lighting
• Low Cost

• Verifiers measure to standards
• Report Data content
• Instrument to measure and report many parameters
• Give easy to understand grades

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ISO Standard Measurements

• L Side
• Clock Track
• Symbol Contrast
• Modulation
• Error Correction Capability

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L Side

• The L side is used to find the code
• Some defects are easier to ignore than others

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Clock Track

• The Clock Track is used to identify the module
  (data bit) locations

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Symbol Contrast

• This is a measure of overall contrast and has a
  large impact on usable working range.

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Modulation

• Modulation is a measure of localized low contrast

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Error Correction Capability

• Extra code words allow for error detection and
  correction
• Each correction uses up some of these

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Dot Peened

• This is a special case requiring low angle
  illumination
• Does not produce a traditional module pattern
• Very low contrast

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Ink on Metal

• Good visibility to the eye
• Very low contrast dependent upon angle
• Illuminate from above

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Laser Etching

• Generally produces high quality codes

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Challenges ofDirect Parts Marks

• Contrast of mark is very dependent on angle of
  illumination
• The same mark may be readable with one type of
  illumination and unreadable with another

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Specifying Direct Parts Marks for Success

• Specifications must anticipate how the symbols
  will be illuminated
• Everyone in the Supply Chain must evaluate and
  scan the codes consistently
• ISO 15415 Provides a way for Application
  Specifications to dictate the illumination most
  appropriate