Examining the Effectiveness of CT Metrology for Measuring Manufactured Parts

Share this Article

[Image: Nikon]

X-ray computed tomography, also known as CT or CAT scan, has been used for years in the medical field. More recently, manufacturers have begun using it to measure a part’s geometrical dimensions, including both internal and external features. It is frequently used in additive manufacturing to non-destructively measure complex parts. In a thesis entitled “Studies of Dimensional Metrology with X-ray CAT scan,” a University of North Carolina at Charlotte student named Herminso Villarraga Gómez conducts several experiments that evaluate the performance of cone-beam CT measurements and their uncertainty estimates, comparing them to reference measurements mostly obtained from tactile coordinate measurement machines (CMMs).

Gómez points out that the field of CT metrology still faces challenges in trying to estimate measurement uncertainties, “mainly due to the plethora of influencing factors contributing to the CT measurement process.” His thesis attempts to further understand the role of variables affecting the precision and accuracy of CT dimensional measurements. The main CT variables he investigates are temperature in the Xray CT enclosure, number of projections for a CT scan, workpiece tilt orientation, sample image magnification, material thickness influences, software postfiltration, threshold determination, and measurement strategies.

[Image: Laser Design Inc.]

In some experiments, Gómez contrasted the results against simulations performed in Matlab software and another simulation tool called Dreamcaster.

“For dimensions of geometric features ranging from 0.5 mm to 65 mm, a comparison between dimensional CT and CMM measurements, performed at optimized conditions, typically resulted in differences of approximately 5 µm or less for data associated with dimensional lengths(length, width, height, and diameters) and around 5 to 50 µm for data associated with measurements of form, while expanded uncertainties computed for the CT measurements ranged from 1 to over 50 µm,” he states.

He also assessed methods for estimating measurement uncertainty of CT scanning. He presents a thorough study of metrics used for proficiency testing, including tests of statistical consistency (null-hypothesis testing) performed with Monte Carlo simulation, and applies them to results from two recent CT interlaboratory comparisons.

“In particular, it is shown that the use of the En-metric in the current state of CT interlaboratory comparisons could be difficult to interpret when used to evaluate performance and/or statistical consistency of CT measurement sets,” he continues.

[Image: Nikon]

Gómez’s study is important when applied to additive manufacturing because, particularly in fields such as aerospace, precision of parts is of the utmost importance. A flawless method of measurements must be established, and CT scanning has great potential, and is indeed already in widespread use. But it’s not perfect, as Gómez points out, and his thesis attempts to assess and better understand its limitations.

One of the benefits of additive manufacturing is that it can create parts with complex geometries, both internal and external, and those can be difficult to measure, especially non-destructively. QA for 3D printing is still problematic for many parts. CT scanning is a largely reliable method for measuring the complicated internal channels and features that additive manufacturing is known for, and Gómez’s work is a big step toward making it even more reliable.

Discuss this and other 3D printing topics at 3DPrintBoard.com or share your thoughts below. 

 

 

Share this Article


Recent News

How does PLA Color Influence Mechanical Properties in FDM 3D Printing?

SmarTech Patent Reports Provide New Insights into Corporate Strengths and Strategies



Categories

3D Design

3D Printed Art

3D Printed Food

3D Printed Guns


You May Also Like

3D Printing News Briefs: November 1, 2019

In this Halloween week edition of 3D Printing News Briefs, we’re telling you about a report, an agreement, and 3D printed footwear. SmarTech Analysis has released its market analysis report...

Additive Manufacturing Strategies: Early Bird Registration Rates End October 30th

If you’re interested in attending an industry event that will offer a deep dive into all things metal, medical, and dental 3D printing, then the third annual Additive Manufacturing Strategies...

3DPOD Episode 15: The Ceramics 3D Printing market: Davide Sher of SmarTech Analysis and 3D Printing Media Network

Davide Sher used to write extensively on 3D printing. Nowadays he runs his own media network in 3D printing and works for SmarTech Analysis. Davide looks at 3D printing from...

SmarTech Analysis Launches New Data Product Addressing Parts Produced by Additive Manufacturing

Industry analyst firm SmarTech Analysis today announced a new data product geared towards addressing the critical metric of additively manufactured parts produced. The Additive Manufacturing Applications Market Analysis Report is a...


Shop

View our broad assortment of in house and third party products.


Services & Data

Subscribe To Our Newsletter

Subscribe To Our Newsletter

Join our mailing list to receive the latest news and updates from our 3DPrint.com.

You have Successfully Subscribed!