Quantifying alignment effects in 3D coordinate measurement.

Details

• Creators:
  Hammett, Patrick D. ; Garcia-Guzman, Luis M. ; Geddes, Steven W. ; Walsh, Patrick T.
• Corporate Creators:
  University of Michigan. Transportation Research Institute
• Subject/TRT Terms:
  3D Non-contact Measurement, Measurement Systems Accuracy Analysis, White Light Measurement, Laser Scanning, Coordinates Dimensional Analysis Lasers Optical Scanners
• Publication/ Report Number:
  UMTRI-2009
• Resource Type:
  Tech Report
• Geographical Coverage:
  Michigan
• Corporate Publisher:
  University of Michigan. Transportation Research Institute
• Abstract:
  The use of fixtureless, non-contact coordinate measurement has become increasingly prevalent in manufacturing
  
  problem solving. Manufacturers now routinely use measurement systems such as white light area scanners, photogrammetry,
  
  laser trackers, and portable laser scanners to conduct studies that require measuring upstream supplier parts, tooling, or inprocess
  
  subassemblies. For part measurements in these studies, certified fixtures with alignment features such as tooling balls
  
  often are not available. Instead, manufacturers rely on ad hoc part-holding fixtures or measure parts without fixtures and
  
  perform alignments mathematically. Here, advancements in software are providing operators with numerous alignment options,
  
  and users are actively using this functionality. Naturally, these additional capabilities have led to inconsistencies in the
  
  alignment method used across measurement studies, often affecting dimensional results.
  
  This paper reviews several common alignment or registration methods and provides a metric to assess systematic
  
  alignment error. To demonstrate alignment effects, we present a measurement system study of a moderately complex part
  
  requiring an over-constrained datum scheme. We first measure the part using a conventional fixture-based method to establish a
  
  baseline for static and dynamic repeatability. We then compare these with results from two mathematically-based iterative
  
  alignment methods based on fixtureless measurement. Next, we assess the systematic alignment error between the different
  
  fixture/alignment alternatives. We show that for the same basic datum scheme provided on engineering drawings, the systematic
  
  alignment error is a far more significant issue for problem solving than the repeatability error or equipment accuracy.
  
  
• Format:
  PDF
• Collection(s):
  US Transportation Collection
• Main Document Checksum:
  urn:sha256:3a6b6801304b250d5529df4354c3a2435904b5948ba0dcb9ee5590cb493b81d6
• Download URL:
  https://rosap.ntl.bts.gov/view/dot/18021/dot_18021_DS1.pdf
• File Type:
  [PDF - 1.00 MB ]