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Inspection and quality control with X-ray CT
The inspection and quality control of metal AM parts with X-ray Computed Tomography (micro CT) X-ray Computed Tomography (micro CT) is just one option for the inspection of metal AM parts. Other options include using eddy current, ultrasonic technology, white-light interferometry and non-interferometric optics. However, given recent developments, it is micro CT that has the most potential in view of its unique capability for the inspection of complex internal structures and geometries without destroying the part. The capabilities of this inspection method are presented by Andrew Ramsey and Herminso Villarraga-Gomez of Nikon Metrology Inc.
X-ray Computed Tomography (micro CT) is the only non-destructive testing method that is able to effectively inspect - with measurement strategies from coordinate dimensional metrology - volume defects and complex geometry inside a part. Eddy current testing can only inspect local defects near the surface of a part, while ultrasonics can inspect only simple geometries near the surface with some reach inside the volume. Optical and interferometric methods can only inspect features at the surface of the part. While the latter (interferometric) techniques are very good at achieving higher resolutions (up to a few nm), the micro CT technique can cover, in a single scan, external and internal surfaces, with micrometre-level resolution and, in some cases, at higher resolutions below the micrometer level (on the order of a few hundred nanometers). The growing interest in micro CT comes at a time when interest in Additive Manufacturing is redefining the manufacturing landscape. Consulting firm IDC states that global spending on AM equipment, both desktop and industrial, reached
Vol. 3 No. 2 © 2017 Inovar Communications Ltd
about $11 billion in 2015 and is forecast to reach $27 billion by 2019. Another company, MarketsandMarkets, is predicting that Additive Manufacturing will experience 30% compound annual growth and reach $30 billion by 2022. In its April 2016 study, “3D Printing Comes of Age in
US Industrial Manufacturing,” Price Waterhouse Coopers (PWC) stated that, compared to two years ago, more manufacturers (52% this year compared to 38% in 2014) expect Additive Manufacturing to be used in high-volume production in the next three to five years.
Fig. 1 A Nikon Metrology XT H225 ST X-ray CT system
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