CT Scanning Aimed as Machined Part Validation Method

Machine shops invest sizeable sums of money and time in guaranteeing that the parts they produce meet specifications - especially those used in high-performance industries such as automotive, aerospace, electronics, and medical. One way they do this is by using advanced metrology and related inspection procedures.

Third-party providers often conduct these analyses with specialized equipment and software. One such company is Jesse Garant & Associates (JG&A) of Windsor, Ont., Canada. At the recent Plastec New England Show in Boston, JG&A outlined its services.

A centerpiece of the company's capabilities is industrial computed tomography (CT), a non-destructive scanning technology. JG&A uses it to take up to 3,500 2D X-rays of a part as it rotates 360 degrees. The company then transfers the data to software that interlaces the images to create 3D internal and external representations -- much the same way a medical scan is created.

VGStudio Max software from Volume Graphics allows CAD data to be overlaid with CNC data to validate part dimensions. VGStudio Max software from Volume Graphics allows CAD data to be overlaid with CNC data to validate part dimensions.

CT is a fast and accurate way of validating geometric dimension and tolerance, JG&A says. The company uses it to validate wall thickness, reverse engineer parts to verify internal and external geometries, conduct void analyses and examine metal for porosity, and ensure that data from CAD models has been accurately transferred to CNC programs.

Of particular note, CT scans identify microscopic cracks, knit lines, and other imperfections that might not be apparent with conventional inspection procedures.

The company supplies a report for a customer, usually in 24 hours, detailing its findings. JG&A also provides software that machine shops or OEMs can use to examine the CT-generated data.

A JG&A representative at Plastec New England said the company is working to educate the market about the benefits of CT inspections. It's a "slow process of education," he acknowledged, but the market is opening up and becoming more receptive. JG&A can cite a number of critical part validations it has conducted with CT scans, among them an internal engine blade for an aircraft manufacturer in Canada.

CT scanning validates parts made by electrical discharge machining as well as those produced on horizontal and vertical machining systems, and it can be used with any metal or alloy. According to the company, it is also effective in analyzing parts produced by laser sintering and additive manufacturing (3D printing). Other applications include composites, where, among other procedures, CT scanning inspects the placement of reinforcements, and plastics parts.

Machine shops and OEMs with their own machining facilities can do CT scanning, though it would probably be more cost-effective to contract with a third-party vendor. A number of companies supply CT industrial scanning systems; notable among them are Nikon Metrology, GE Measurement & Control, North Star Imaging, and Hadland Technologies.

JG&A uses software from Volume Graphics of Heidelberg, Germany (U.S. office is in Charlotte, N.C.), for CT scan analysis. The company is also an authorized reseller of the software.

Key to the performance of CT scanning, at least as practiced by JG&A, is VGStudio Max software and modules from Volume Graphics. The software analyzes voxel or volume data. A voxel is a volumetric value on a grid in 3D space. (The word is a portmanteau of "volume" and "pixel.")

VGStudio Max software arranges the data of individual voxels into a 3D grid and provides a full picture of a component along with information about its material properties and inner structure.

The basic capabilities of the software include 15 functions, among which are visualization, object positioning, segmentation and classification, data analysis and measuring, surface extraction, and documentation. Modules include coordinate measurement, nominal and actual data comparisons, porosity analysis, wall thickness analysis, and CAD import.

The developer's other software include VGStudio, which it describes as a "high-tech solution for the visualization of voxel data" (functions include animation), and VG InLine, which allows machine shops and other manufacturers with their own CT scanning systems to convert them into a non-destructive inspection tool without a major reprogramming of the scanner software.

VG InLine rapidly inspects parts with recurring analysis/visualization patterns. Volume Graphics says it can be used in an automated inline inspection system, for batch production, and in quality-assurance laboratories.


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