When drilling a well, clearing a forest or excavating a building site, experienced operators count on their toughest equipment to help them get the job done.
The same is true for a big measuring job that won’t fit into a metrology lab—a train car, ship or airplane—when experts pack laser trackers and scanners that can not only capture large point clouds but also function reliably where there may be no electrical outlets and when the weather messes with the most carefully laid out plans.
“The No. 1 factor that we look for is utility,” Direct Dimensions CEO Michael Raphael said. “As a 3D measurement service bureau, we are looking for metrology instruments and equipment that are broadly applicable and can solve a wide range of problems.”
The go-to metrology equipment in Direct Dimensions’ storage room includes laser scanners from Leica (Hexagon), Faro, Surphaser and Artec because they have the features Raphael and his team need for jobs such as scanning the historic warship U.S.S. Constellation in dry dock in Baltimore. For that historic-preservation job, the service bureau used a Faro Focus Laser Scanner and a Surphaser 3D scanner.
Surphaser scanners, from Basis Software, are built for industrial and outdoor environments and promise submillimeter accuracy. These are the scanners Raphael and his team use when they need to capture accurate detail in a large-size project, particularly when the scan is for reverse engineering and an accurate, detailed scan is critical.
“If we’re going to scan an airplane and it’s for some manufacturing-related reason, like they want to design a new component that needs to fit on the airplane, we need dimensional accuracy,” he said. “They’re going to go off and build tooling, do engineering work, they’re going to fabricate something, and it has to fit. The tolerances on a project like this will likely dictate that we need to use the Surphaser.
“Now, when you’re scanning a very large building in the architectural world, we can get away with less precision and provide an output that’s well within the requested tolerances for that type of application. As such, a Faro Focus or Leica (Hexagon) RTC360 are perfect tools for AEC (architectural, engineering and construction) applications.”
Greg Groth, division manager for the Brookfield, Wisc. office of Exact Metrology, a contract measurement and scanning company that also sells and rents metrology hardware and software, said that in addition to precision and quality of data, he looks for ruggedness in the equipment he uses.
“That can come in the form of packaging (most common) or the measurement tool itself,” he said. “We travel all around the world, so we have to be able to withstand various travel methods and the occasional baggage handler trying to get first place in a throwing contest.”
Other desirable features that can land metrology equipment in the “go-to” category include:
- the option for battery-powered operation;
- an integrated human-machine interface vs. one that requires a laptop;
- the ability to be mounted or used in different orientations;
- operability in extreme conditions, such as fluctuating temperatures and weather, and weight.
“If you have to move this piece of equipment around, if it’s 30 pounds or more, that’s not easy,” Raphael said. “But if it’s 10 pounds, it’s significantly better.”
Another feature to add to the list of desirables is a magnetic base like the one on the portable Romer (Hexagon) Absolute Arm, Groth said. He said the magnetized base that’s standard on the various versions of the high-precision portable arm—available in 6-axis, 7-axis, compact, with and without an integrated scanner models—increases the possibilities for placing it in just the right position for accurate measurement.
One of the newer features on metrology equipment is Ingress Protection (IP) certification, an international standard for electrical enclosures that define levels of sealing effectiveness against intrusion from foreign bodies, such as dust, dirt and moisture.
“It wasn’t until a few years ago that you could even get that, but now that the electronics have gotten much better and the design of this equipment has gotten much better, these manufacturers are able to go for IP certification,” Raphael said.
Operators choosing metrology equipment have to consider not only the initial price but also cost over time, he said. Questions to ask for overall costs include:
Is the equipment reliable so it will be available when I need it?
What are the maintenance and repair costs?
Is it compatible with third-party software or will I need proprietary software?
Buyers should also check out the equipment’s supplier: Both Direct Dimensions and Exact Metrology are resellers for metrology solutions. What’s the supplier’s history? Have they been around a while? Do they stand behind this piece of equipment? Do they put out revisions on a regular basis or has product development stagnated?
No Ph.D. needed
Hexagon Manufacturing Intelligence has made product development a priority since introducing its first laser tracker, the Smart 310, in 1990.
“Starting all the way back then in the early 1990s our focus had always been to take the technology and move it to something that was capable, was easier to use, made it so you didn’t have to be a Ph.D. or a seasoned operator to use the technology,” said Joel Martin, laser tracker product line manager for North America.
Martin, who’s been with Hexagon 23 years, said he and his colleagues used to say that trackers were transportable rather than portable—because you could move them from one place to another but it required a van.
They were big and heavy and sat on huge carts. Their weight and accessories like cables and controllers made them a challenge to set up and configure.
- In the decades since the Smart 310 came out, the company’s developments include:
the T-Probe, a wireless handheld probe that substitutes for a spherically mounted retroreflector (SMR);
- the T-Scan, a handheld laser scanner, and
- PowerLock, a laser beam technology that helps a laser tracker operator automatically connect the laser beam emitted by the tracker with the reflector.
Hexagon has also focused on making its technology lighter, battery-operated, equipped with wireless communication and IP54-certified.
“The whole focus for us has been when somebody needs to implement a laser tracker into an inspection, an application or a process, that they don’t have to worry about what idiosyncrasies exist in the technology to work around,” Martin said. “We’ve made it so that you just put the laser tracker down, measure with a probe, measure with a scanner, measure with a reflector, measure whichever end effector device makes it easiest and have that seamless integration where we really don’t have to worry about the technology or the ins and outs of how it measures.”
All of this has made life easier for operators like Raphael and Groth, who use Hexagon’s equipment, and others,’ and travel the globe to do metrology outdoors in all kinds of weather.
“When you look at operating in adverse conditions, anything outdoors is pretty much the climax of all of that,” Martin said.
Operators have used Hexagon’s equipment in winter’s snow and ice to do inspections on the doors that open and close locks, gated sections of waterways that can adjust water levels to move ships from one waterway to another, and in desert conditions doing alignment work on government testing ranges, he said.
“It takes a lot of foresight to understand where do I set up the equipment, what are my lines of sight, what do I have to worry about,” Martin said.
Safety is paramount
Even with the type of planning Groth and his team do while figuring out logistics for a job, when something unexpected comes up they need to be ready to respond on the fly.
“Because of the diversity of our projects, we make the necessary adjustments on site,” he said. “For example, tenting the equipment during precipitation or wrapping the hardware in protective cloth in highly contaminated environments.”
Tenting the metrology equipment may also be necessary on a hot, sunny day to maintain your setup, Martin said.
“If you’ve got direct sunlight beating down on anything, that turns into thermal expansion of whatever that is,” he said. “So, if you have a tracker sitting on an aluminum tripod that tripod is going to shift and move around.”
Every detail matters
Sometimes it’s even necessary to tent the object being measured, or to work at dawn or dusk because some scanners don’t work well in bright sunlight. (Direct Dimensions had to tent the warship it was scanning in Baltimore, Raphael said.)
Because of the detail needed in the scan to meet the requirements for tight tolerances, the crew used a Zeiss Comet scanner. Even though the Comet is designed to be light and portable, the technology is engineered for indoor use. What made the Comet useful is its ability to capture large volumes, up to 4 x 4’.
“The technology needs a homogeneous light,” said Alberto “Al” Griffa, a regional product sales manager at Zeiss. “If there is variable light, the accuracy can’t be achieved.”
For this large project, the Comet was used with a technology called photogrammetry.
“It allows us to scan large parts with a high accuracy because the photogrammetry allows us to combine all the scans together,” Griffa said. “With a photogrammetry kit, the system is a high-end, 32-megapixel camera that captures different images and then in combination with the Comet you can stitch them all together very accurately.”
On large jobs like the ship, Groth advises operators to be aware of their environment to maintain safety.
“Not all of the technology is wireless, or battery operated, so being aware of your cable management is very important,” he said. “Tripping over a cable or having a fork truck drive over a communication cable can certainly ruin a day.
“When scanning very large environments, like powerplants or factories, several repositions of the equipment occurs. This presents a variety of hazards to the application engineer onsite, who more than likely is not used to the hazards in that specific facility. Those movements sometimes need to be surgical, with good teamwork being key.”