Defect Detection and Quality Control in Additive Manufacturing

Additive manufacturing (AM), also known as 3D printing, is considered to be one of the greatest technologies of our times and has the ability to completely transform many business landscapes in the coming years and decades. However, constraints and challenges still exist in AM that need to be addressed by the combined efforts from Engineers and Scientists.

During this process, with the help of X-ray imaging products and expertise, North Star Imaging can assist users to design, improve and build advanced quality products using this remarkable additive manufacturing technology.

Defect Detection

Conventional X-ray radiography has been used for detecting the internal defects, such as foreign objects (inclusions) and pores in casting samples. Thanks to 3D Computed Tomography (CT), the distinguishable and detectable levels of variation in the sample have been vastly improved allowing the partly fused regions in certain AM parts to be viewed easily.

Dimensional Conformation

AM technology is all about constructing a product directly from a 3D model, and this 3D model, in turn, can have a highly complex geometry because of sophisticated design methods such as free materials simulation, 3D topology optimization or medical implants design tailored by customers.

High Resolution X-ray microtomography (micro-CT) can non-invasively and non-destructively image the object in 3D and is the preferred method in terms of inspecting dimensional (particularly internal dimensions) faithfulness of AM products to its original design.

In addition to taking measurements from the 3D images, one quick, common assessment involves digitally registering the scanned volume image to the original CAD model (with or without reference features), followed by quantifying the differences between the two in 3D.

Raw Materials Control

EBM and SLM are examples of powder bed based AM techniques, where the quality of the raw metallic powders is very important to the build the quality of the final part.

With high resolution CT, the size distribution of metallic powders can be non-destructively characterized, quantifying its sphericity which significantly establishes the overall flowability, and also checks whether there are hollow inclusions or particles in a testing batch.

Process Optimization

In AM process, many manufacturing parameters can considerably influence the quality and morphology of the final part, even for an identical CAD input. These manufacturing parameters include but are not limited to laser scanning path, CAD orientation, pre and post heat treatment, laser power and exposure time, etc.

Using specially designed software and micro-CT, North Star Imaging can track small variations from the parts when adjusting these parameters and thus be able to help the designer with process optimization.

Volume Based Simulation and Further Analysis

Industrial X-ray CT can turn a real part into a comprehensive 3D computer model. When compared to the CAD model design, the scan-derived model can provide additional information such as internal defects, surface roughness and part morphology. Hence it can be changed into a much more realistic model for computational fluid dynamics simulations and finite element analysis.

With North Star Imaging’s special 4D imaging capability, users can simultaneously track and measure the behavior of an AM part being used, tested and imaged using the company’s X-ray CT scanners.

Conclusions

2D radiography, X-ray imaging techniques and especially 3D CT, are robust and useful tools that can be used to develop, improve and validate additive manufacturing technology and products.

North Star Imaging believes that a combined imaging and analysis solution will equip users with the best tool to be successful in this rapidly growing area.

This information has been sourced, reviewed and adapted from materials provided by North Star Imaging, Inc.

For more information on this source, please visit North Star Imaging, Inc.

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