Computed tomography scanning (CT) seems like a dream come true for dimensional inspection. It both measures the outside of parts and reveals the hidden, from occlusions to internal cooling channels, without destroying the piece. Evolving from looking at human brains and hearts to measuring the complexities of turbine blades, it is part of the growing complexity of industrial metrology.
But the story is more than that.
The ongoing evolution of CT scanning, which I have been covering for a few years, is an interesting case study in technology development. The story is in both its limitations and how those limitations are gradually being addressed. Unfortunately, it is not a panacea. CT penetrates a limited set of materials, measures slowly, is typically confined to smaller parts—and is expensive. The story is in how innovative professionals are advancing the technology.
Speed and penetration of CTs are highly dependent on their power, usually measured in kilo-electron volts (KeV). Many of the largest machines are in the 450 KeV range, capable of measuring parts roughly 300 mm in volume. Lighter elements in the periodic table have proven ideal for CT metrology, with steel on the edge of practicality even for the higher power machines. High-temperature materials, such as Inconel, are difficult to penetrate, except for the smallest or thinnest parts.
For the Jesse Garant Metrology Center, this was simply not enough. It developed a massive 3 million electron volt (3 MeV) machine—over six times more powerful than the most powerful CT scanner commercially available, with a 1 × 1-m active detector panel. It measures parts up to 43.5″ (1.1 m) in diameter by 66″ (1.7 m) in height. The accuracy is 500 microns, calibrated using the VDI/VDE 2630 testing methodology on a test specimen certified by NIST, according to Andrew Good, technology manager for the company. The machine is contained within its own garage-sized shielded room. It is also fast. “Customers do not have to wait for days and we can do production runs. We have one job where we are measuring 1800 mid-size parts,” said Good.
Three factors allowed the building of this “monster” machine. One is that Jesse Garant runs only a service bureau operation. They build their own machines, using expertise they have developed since 2009. It gives them a competitive advantage while expanding the envelope of what is possible.
The second factor was a solid market forecast. “We knew customers would clamor to have us feasibly measure larger parts made of heavier metals with critical internal features,” said Good. This allows the company to book enough business on the machine with enough of a diverse customer set to pay back the initial investment—which was considerable.
The third factor is the ability to back up technology with a well-trained staff and educate existing and potential customers. “You have to provide easy access to a complicated technology,” he said. “We do it with consulting, classes, and webinars. Each customer walks away with an education.” A knowledgeable customer knows when to come knocking with the right part, preproduction run, or production project.
The three factors Jesse Garant learned are ones anyone might apply to any technology on the frontier. No doubt other technology professionals are building the future as well…I look forward to learning about what comes next.
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