Better Design Through Measurement: Contact vs. Non-Contact Technologies


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FARO Applications Engineer Ryan Dant explores contact and non-contact measurement technologies, and explains the advantages of each to the design engineer, OEM manufacturer and others. Attendees gain a greater understanding of the advantages and drawbacks for both, and ultimately are able to decide which is best for their unique application. In addition, Ryan:
Discusses, in-depth, the process of contact measurement including the types of probing methods – hard-probing and touch-trigger methods
Explains laser probing as it relates to articulated arm CMMs; covering point cloud spread, volume, and the effects of color and reflectivity on the target item
Details the uses of each type of measurement in different applications, and explain the specific benefits to users

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Better Design Through Measurement: Contact vs. Non-Contact Technologies

  1. 1. Better Design Through Measurement: Contact vs. Non-Contact Technologies
  2. 2. Before We Start  This webinar will be available afterwards at & email  Q&A at the end of the presentation  Hashtag for this webinar: #DWwebinar
  3. 3. Moderator Presenter Leslie Langnau Ryan Dant Design World FARO Technologies
  4. 4. Better Design Through Measurement: Contact vs. Non-Contact Technologies Ryan Dant, Applications Engineer, FARO Technologies
  5. 5. Agenda • Introduction • Single Point Repeatability and Volumetric Accuracy • Contact Measurements o • Non-Contact o • • Strengths and Weaknesses Strengths and Weaknesses How can You Benefit? Q and A
  6. 6. What Is Contact Measurement In terms of articulated arm CMM’s, contact measurement includes any probes that require the probe to be physically touching the surface of the part being digitized. • This includes hard probes and touch-trigger probes
  7. 7. Non-Contact Measurement A type of digitization that uses lasers or light systems to capture data without touching the part. • Includes white and blue light systems, as well as laser line probes, used with portable CMM’s. • We will focus on those types of probes that can be used in tandem with an articulated arm (e.g. Laser Line Probes (LLPs)
  8. 8. Single Point Repeatability and Volumetric Accuracy Two ways to compare different measurement methods: • • Single Point Repeatability, or precision, is how close the same measurements are together. Volumetric Accuracy: How close a point can be in 3D space to it’s nominal (or correct) position.
  9. 9. Contact Measurement Hard Probing Touch-Trigger Probing
  10. 10. Contact Measurement: Hard Probing • Hard Probing is a subset of those types of probes that require contact with the desired surface and a manual trigger. • Hard probes come in a variety of different shapes and sizes, ranging from large ball-type probes down to a needle point.
  11. 11. Contact Measurement: Hard Probing - Calibration • When a probe is switched it is important to “teach” the arm the location of the tip (point probe), or the center of the sphere (ball probe). o Known as calibration • There are different types of calibration, each used for a specific case of probe type. Videos available at
  12. 12. Contact Measurement: Hard Probing – Ball Compensation • When measuring a surface with a ball probe, the radius of the probe (4) must be considered. • This is because the point is taken at the center of the probe (3) which was found during compensation. • But the ball contacts the surface at the tangent point (2).
  13. 13. Contact Measurement: Hard Probing - Accuracy • The accuracy of a hard probe is entirely determined by the accuracy of the articulated arm CMM that it is mounted to. • Modern “Arms” range in accuracy from <.001” to around .005”
  14. 14. Contact Measurement: Hard Probing – Capturing Data When capturing data with a hard probe, the probe is placed up against the desired surface and a manual trigger is depressed which records the 3D location of the probe at the moment of the trigger. Single Point – Trigger for every reading Interval – Press and hold for either distance based or time based readings
  15. 15. Contact Measurement: Hard Probing – Points Taken vs. Accuracy To accurately represent a feature, enough points must be taken to improve the best fit. How many is enough?
  16. 16. Contact Measurement: Best Fit • When accurate readings for surface inspection are needed it is important to take a high volume of points to account for any deviation on the surface of the part. • It can be a lengthy process to cover a surface in a high volume of points necessary for detailed surface inspection.
  17. 17. Hard Probing • Accurate o As high accuracy as .0005” • Low volume of points • Quick Measurement of Geometric Primitives
  18. 18. Contact Measurement: Touch Trigger Probes • With a touch-trigger probe the articulated arm will record a point when the probe contacts the surface. o Thus, the x,y,z data of the point will be recorded at very low pressures. • This can be beneficial when measuring parts consisting of material that deflects under low amounts of pressure. o e.g. Molded or formed plastic, sheet metal
  19. 19. Non-Contact Measurement Laser Line Probes
  20. 20. Non-Contact Measurement: What is an LLP? • (1) Laser Emitter • (2) Camera • (3) Calibration Plate
  21. 21. Non-Contact Measurement: LLP Calibration As with the hard probe, we need to teach the arm the 3D distance from the laser emitter to the points being taken.
  22. 22. Non-Contact Measurement: Calibration Considerations • When calibrating a laser probe, it is first necessary to use a properly calibrated contact probe to define a feature. • When dealing with an attached LLP the accuracy of the LLP must be added to the accuracy of the Arm; the resultant “system” accuracy will be what is measured to.
  23. 23. Non-Contact Measurement: Acquiring Data Takes ~45,000 points per second along a line
  24. 24. Non-Contact Measurement: Point Clouds A scan with an LLP will produce a point cloud, which is just a large 3D group of points that correspond to the geometry measured. • Point clouds can be exported to CAD and turned into models • They can also be used for inspection
  25. 25. Non-Contact Measurement: Point Cloud Color Contour Map Laying a point cloud over a CAD model we can obtain a color map that shows us the deviation of the part scanned.
  26. 26. Non-Contact Measurement: Measurement Considerations • Part Color o The easiest colors to capture start at white and the difficulty increases as the color darkens. • Darker colors absorb more light • Part Reflectivity o As a part reaches a certain threshold of reflectivity, the part will scatter the laser and make reading hard to acquire o e.g. high machine finish and chrome parts
  27. 27. Non-Contact Measurement: Resolving the Reflectivity Problem • Paint the part. • Coat the part in a solvent, which can counteract the effects of reflectivity.
  28. 28. How Can You Benefit? Industry Comparison & Conclusions
  29. 29. Conclusions: Hard Probing Good for doing simple measurements quickly on rigid parts. • • • Machine Shops Fabrication Shops Welding
  30. 30. Conclusions: Touch-Trigger Probes Applications where simple feature based measurements suffice, but material will deform if pressed on by a hard probe. • • Plastics Formed Sheet Metal
  31. 31. Conclusions: Laser Line Probe • Ideal for complete reverse engineering projects o Point Clouds can be exported into CAD and turned into IGES, STP, or X_T (to name a few) • Inspection of complex geometry not suited for feature based inspection o Can compare to CAD and provide color contour maps
  32. 32. Thank You For more information:
  33. 33. Questions? Design World Leslie Langnau Phone: 440.234.4531 Twitter: @DW_RapidMfg FARO Technologies Ryan Dant Phone: 630.862.4752 - Can call or text
  34. 34. Thank You  This webinar will be available at & email  Tweet with hashtag #DWwebinar  Connect with  Twitter: @DesignWorld  Facebook:  LinkedIn: Design World Group  YouTube:  Discuss this on