CT devices for Dimensional Metrology Filip Geuens CTO - Nikon - - PowerPoint PPT Presentation

CT devices for Dimensional Metrology

Filip Geuens CTO - Nikon Metrology

Symposium on Computed Tomography KULeuven – Group T 4th June 2013

Content

1. Vision about Metrology CT 2. Benefits of Metrology CT 3. Traceability of Metrology CT 4. Needs for Research

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4. Needs for Research

2

New production technology requires new metrology

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3

Metrology CT measurement process

NM CT Pro 3D volume reconstruction NM Inspect-X 2D data collection Feature inspection + CAD compare

MCT will lead to integrated

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Defect analysis

integrated material and dimensional analysis

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

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metrology company and KULeuven spin-off Became part of Nikon group as Nikon Metrology in 2009

Legacy Method - Measurement in a non-metrology system

Measure with traceable touch probe to get calibrated value Measure with system and measure the Compare the values and calculate the error Adjust the scaling based

• n minimising

the error of the calibration piece scan

Scan the specimen and the calibration artefact at the same position and under the same X-ray conditions

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and measure the same distance piece scan

Advantages:

• Simplicity
• Any CT system can make

measurements Disadvantages:

• Difficult to determine measurement

uncertainties

• Must be performed for every new

manipulator position

• Slow
• Calibration artefact must have similar

radiographic properties to part

Example - Specialised blade inspection

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7

Research new material and production techniques

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8

2D CT slice of carbon fiber plate with impact region De-lamination below impact

Research new material and production techniques

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9

How are the carbon fibers woven?

Benefits MCT over traditional metrology

Reduce total measurement time

• Measurement + reconstruction time independent from

number of features

• Very easy machine programming & operation

Provide better insight in problem to reduce number of iterations

• 3D image provides better insights
• Higher

productivity

• Shorter time

to market

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• 3D image provides better insights

But also

• Avoid destroying sample
• Do any analysis at any time without remeasuring

10

Current Metrology CT

Temperature

controlled enclosure 20OC ± ± ± ±1OC

Strengthened manipulator for maximum stability MPESD = 9 + L/50

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High resolution detector 200 µm pixel size Precision manipulator

• High resolution encoders
• Error mapping using laser

interferometer In-house designed micro- focus source for sharp low-noise images

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.

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It is not an agreed standard, there is scope for variation within the Guidelines.

Forms the basis of the current ISO draft. TC213 WG10

Verification - A standard is needed – “the missing link”

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13

Method and Artefact with reference to VDI/VDE 2630 part 1.3

Spatial Resolution

Using calibration piece suggested by University of Padua. Scan piece with main calibration piece

D d

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Fit spheres and calculate diameter of circle of confusion

• n co-tangent plane

Using circle diameter calculate the spatial resolution

D R

2 2

d D D R − − =

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.

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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.

Major issue - Multi-material assemblies

Optimised for low density Optimised for high density Compromise

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Measurement possible, accuracy depends on object No accurate measurement possible Accurate measurement possible

• 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.

Summary and Conclusions

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• 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

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