Additive Manufacturing: 3D CT and Beyond

It’s clear that for reliable quality assurance of additive-manufactured parts, non-destructive inspection is necessary. 3D computed tomography, also referred to as 3D CT or just CT, is an effective tool for NDT.

3D CT and Scanning Speed

Over the last decade, improvements in CT scanning speeds, image accuracy and resolution, and operational efficiencies have led to inline CT, in which inspection occurs practically at the same time as the production line is producing the machine part. This has made CT viable for large-scale automated defect recognition (ADR) in a production environment.

The radiographs are acquired with a known geometry of the key components and for a selected set of scan parameters. During a CT scan, an object is rotated and thousands of pictures are taken at a variety of comprehensive angles, creating a 3D volumetric data set.

The Data 3D CT Produces

This data set consists of voxels (volumetric pixels), where each voxel is a measure of the X-ray attenuation for that scan of the object at that 3D location. After image acquisition, sophisticated software combines the acquired data, imaging geometry, and scan parameters selected by the user to create a 3D volume of the piece.

How Manufacturers can use 3D CT Analysis

Additive manufacturers need to analyze many aspects of their processes, among them feedstock characteristics, material characterization, porosity, lattice structure visualization, and surface roughness. They may also need to perform nominal actual comparison (NAC), finite element analysis (FEA), or reverse engineer a part. CT can assist with all of these, but the aspects most frequently requested for production processes fall into two categories – discontinuity analysis and dimensional measurements.

Comparison with other NDT Techniques

While there are a number of traditional methods for NDT, most of them are limited in what they can detect, so they must be used in conjunction with one another. On the other hand, 3D CT is ideal for addressing all of the needs of NDT. Table 1 compares 3D CT with other NDT characterization techniques:

As the table shows, CT is suited to multiple QA/QC evaluation tasks — a one-stop shop for AM components. By using a single technology, rather than needing several different types of equipment and staff with varied operational and interpretive skillsets, CT analysis could well present a cost-effective alternative to using multiple other NDT methods.

To see some examples of 3d CT in practice, download our whitepaper below

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