New national facility for coordinate measurement

The Mitutoyo Legex 574 at home in the new coordinate measurement facility at the Measurement Standards Laboratory. Celebrating the installation are Eleanor Howick, Lenice Evergreen and Chris Young from MSL's Length team with Mr Hum of Mitutoyo - Singapore and Stephen Browne, the NZ Agent for Mitutoyo.

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For decades, MSL’s length metrology team has supported New Zealand industry and academia. From calibrating artefacts and realising the definition of the metre, to (external link)determining the roundness(external link) of aircraft engine parts and characterising components for the world’s leading telescopes(external link), our scientists have successfully tackled a broad range of measurement challenges.

And now, after more than three years of effort, and in the midst of a global pandemic, MSL is adding a critical new facility to its offering – a national centre for coordinate metrology. Housed within a dedicated lab on the Gracefield campus, its two new coordinate measuring machines (CMMs)[1] will cement MSL’s position as the New Zealand home of innovative – and traceable – length measurements.

 “This is a major upgrade to our existing dimensional measurement capability,” says Research Engineer Lenice Evergreen. “Our previous CMM was an excellent machine, but it was reaching the end of its life, and it was limited in the size and types of objects it could measure.” As part of the business case, and to ensure that any new CMM they purchased would be fit-for-purpose, Evergreen set out to speak to companies scattered across New Zealand. “In all, we spoke to about 50 organisations; everything from educational institutions and jet-ski builders, through to major manufacturers,” she says. What they all had in common was a measurement need that could be met by coordinate metrology. Some had an existing relationship with MSL, while others had their own in-house coordinate measuring machines, which they used for a variety of different tasks. “The goal of these conversations was to understand what kind of things NZ organisations needed and wanted from a national facility.”

Something that became clear in this process was that the needs of industry diverged. “People either said they wanted a system that could measure relatively small objects very, very accurately, or much larger objects with a slightly lower accuracy,” Evergreen explains. “To be frank, any machine that could simultaneously meet both of those requirements would fall well outside our budget. It made [Principal Research Scientist] Eleanor Howick realise that we’d need two separate machines, possibly from different manufacturers.”

There are just three instrument makers who can produce such high-precision CMMs – Zeiss (Germany), Leitz (now part of Swedish-owned Hexagon MI), and Mitutoyo (Japan). In the search for a small-volume ultra-high accuracy CMM, Evergreen and Howick found the Mitutoyo Legex 574. She says, “It offered us exactly what we were looking for. Its volume is smaller than our old CMM [500 x 700 x 450 mm], but it is very accurate, to within 0.28 µm.” Its low probe force would also allow MSL to study objects made from plastic and other deformable materials – something that had not been possible with their previous machine. Stephen Browne, New Zealand Distributor for Mitutoyo, admits that he was keen to get involved, “I’ve worked with MSL on several projects over the years, but the opportunity to get a Class 1 CMM into NZ was a hugely exciting prospect,” he says. For the large-volume CMM, the length team turned to Hexagon – their Global S Green 12.22.10 would allow them to look at much bigger objects with a range of probes, including non-contact vision and laser scanner sensors."

The business case for the facility was approved at the end of 2019. The next stage was to upgrade the existing CMM lab, to ensure its specifications met those of the two new machines. The ceiling would need to be raised to accommodate the Hexagon’s 3.5 m-tall ram, and a new air-conditioning system installed to manage temperature and humidity within the room, particularly for the Mitutoyo CMM.

But then, the global COVID-19 pandemic hit. Everything was thrown into doubt.

“Our original timeline was that we’d get the Hexagon machine on-site by May 2020, with the made-to-order Mitutoyo to follow in May 2021,” explains Evergreen. “But we knew that would have to shift. The lockdown also meant that all progress on the lab upgrade was paused indefinitely, so even when the machines arrived, they’d have to go into storage.”

Browne, she says, was critical in helping get the project over the line. “Stephen has been amazing to deal with,” she says. “He helped us navigate a big foreign exchange correction that we feared might scupper our chances. And incredibly, Mitutoyo even managed to deliver their machine early – it arrived here in January 2021.”

“The major challenge for us was installing the machine,” says Browne. “It’s a job undertaken by a specialised engineer normally based in Singapore.” And that meant navigating New Zealand’s MIQ (Managed Isolation and Quarantine) system. Pure luck saw an MIQ spot secured for the Singapore-based engineer on the first day room allocations opened. With a firm deadline to hit, work on the lab picked up pace, and was completed before Mr Hum completed his stay in MIQ on 16 November. Hum and Browne travelled to Wellington, and spent a full week installing the CMM. Browne says, “The team at MSL have done the very best they could with their lab space. The environmental criteria for this machine are very stringent, and they’ve certainly met them. It looks really good in there.”

Since completing their familiarisation and training on the Mitutoyo CMM, Evergreen and Howick have been characterising it, preparing it for commercial use. “The initial calibration is still at an early stage, but with gauge blocks, we’re already seeing standard deviations of better than 40 nanometres.” First up on their worksheet is an international comparison, “an exercise that only happens every ten years or so.” A single artefact – in this case, a steel and ceramic step gauge – is sent to a series of national metrology institutes (NMIs). At each institute, the gauge is carefully measured on a CMM or laser interferometer, with the results shared and compared across all of the NMIs. “Comparisons are a key tool for the international metrology community,” explains Evergreen. “So our participation in this one was a driving factor in getting the CMM operational.”

The recent reopening of New Zealand’s border means that commissioning of the large-volume Hexagon CMM could also be just a few months away. "It's amazing to finally be at this point,” says Evergreen. “After three long years we are confident we will be offering a service to industry on both machines by the end of the year."

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[1] A CMM is a computer-controlled device that measures the geometry of physical objects in three dimensions using a very sensitive probe. While CMMs have been around since the 1970s(external link), their accuracy and precision have continued to improve.