CT devices for Dimensional Metrology Filip Geuens CTO - Nikon Metrology Symposium on Computed Tomography KULeuven – Group T 4 th June 2013
Content 1. Vision about Metrology CT 2. Benefits of Metrology CT 3. Traceability of Metrology CT 4. 4. Needs for Research Needs for Research Nikon Metrology Confidential Information 2
New production technology requires new metrology Nikon Metrology Confidential Information 3
Metrology CT measurement process NM Inspect-X NM CT Pro Feature inspection + CAD compare 2D data 3D volume collection reconstruction MCT will lead to integrated integrated material and Defect analysis dimensional analysis Nikon Metrology Confidential Information
X-ray history of Nikon Metrology The company began as X-Tek Systems Ltd specialising in real-time micro-focus X-ray Acquired in 2007 by Metris, a metrology company and metrology company and KULeuven spin-off Became part of Nikon group as Nikon Metrology in 2009 Nikon Metrology Confidential Information
Legacy Method - Measurement in a non-metrology system Scan the specimen and the calibration artefact at the same position and under the same X-ray conditions Measure with traceable touch Adjust the probe to get scaling based Compare the calibrated value on minimising values and the error of the calculate the error calibration Measure with system piece scan piece scan and measure the and measure the same distance Disadvantages: Advantages: • Difficult to determine measurement • Simplicity uncertainties • Any CT system can make • Must be performed for every new measurements manipulator position • Slow • Calibration artefact must have similar radiographic properties to part Nikon Metrology Confidential Information
Example - Specialised blade inspection Nikon Metrology Confidential Information 7
Research new material and production techniques 2D CT slice of De-lamination carbon fiber plate below impact with impact region Nikon Metrology Confidential Information 8
Research new material and production techniques How are the carbon fibers woven? Nikon Metrology Confidential Information 9
Benefits MCT over traditional metrology Reduce total measurement time • Measurement + reconstruction time independent from number of features • Higher • Very easy machine programming & operation productivity • Shorter time Provide better insight in problem to reduce number of to market iterations • • 3D image provides better insights 3D image provides better insights But also • Avoid destroying sample • Do any analysis at any time without remeasuring Nikon Metrology Confidential Information 10
Current Metrology CT Strengthened Temperature MPE SD = 9 + L/50 manipulator for 20 O C ± ± ± 1 O C ± controlled enclosure maximum stability High resolution detector 200 µm pixel size In-house designed micro- focus source for sharp low-noise images Precision manipulator • High resolution encoders • Error mapping using laser interferometer Nikon Metrology Confidential Information
How do we verify accuracy of performance VDI/VDE 2630 – not quite a standard but all we have for now What is VDI 2630? VDI/VDE 2630 is a guideline for verifying the accuracy of a CT metrology system. It is published in Germany and is being adopted by CT Metrology manufacturers. It is not an agreed standard, there is scope for variation within the Guidelines. Forms the basis of the current ISO draft. TC213 WG10 Nikon Metrology Confidential Information
Verification - A standard is needed – “the missing link” Method and Artefact with reference to VDI/VDE 2630 part 1.3 Nikon Metrology Confidential Information 13
Spatial Resolution Using calibration piece suggested by University of Padua. Scan piece with main calibration piece d D D R Fit spheres and calculate diameter of circle of confusion on co-tangent plane Using circle diameter calculate the spatial resolution 2 2 R D D d = − − Nikon Metrology Confidential Information
Many factors influence the accuracy of CT measurement tools � Specimen surface condition, shape, topology and material(s). � Data handling - Reconstruction methods, introduction / suppression of artefacts, data filtering techniques, 3D model creation, surface finding and thresholding. � Radiographic factors, kV, mA, magnification and filtering – effect of scatter. � Detector physics: incl. sensitivity, resolution and geometry. � Environmental temperature and vibration � X-ray source: focal spot size and shape, spectral content � Specimen mounting, stability and orientation. Nikon Metrology Confidential Information
Major issue - Multi-material assemblies Optimised for Compromise Optimised for low density high density Measurement No accurate Accurate possible, accuracy measurement measurement possible depends on object possible Nikon Metrology Confidential Information
Summary and Conclusions • CT has evolved from a qualitative inspection tool to a quantitative measuring instrument. • The ability to verify accuracy and repeatability in a traceable way is essential to enable more widespread adoption. • A recognised standard is needed. • Metrology CT will have an impact on the market of dimensional inspection and merge it with material inspection. But … • Still more research needed for better understanding and making it applicable to a wider range of applications and parts Nikon Metrology Confidential Information
Nikon Metrology Confidential Information
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