Big trucks, big job: Sleuth doesn't toy around to solve dimensional challenges.

Sleuth was getting claustrophobic. His world was shrinking from tenths to microns and perhaps soon to nanometers. He was tucked away in the far corner of the Humongous Earth Mover Company (HEMCO) metrology lab developing multi-sensor measurement system protocols for analyzing prototype engine block and fuel injector components.

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He was concentrating mostly on features you could barely see. Nevertheless, if you could see them, they were often impossible to reach with conventional probes. So Sleuth used the multi-sensor software to stitch together accurate scans of the territory under consideration using data acquired by the smallest touch-trigger probe available, a camera, and even a micro-optical probe.

As long as the various probes were oriented in a common coordinate system, the software didn't care where the data came from.

He wanted to scream, "I've got to get out of here. Give me something big to measure. Let me roam the wide open spaces."

But, of course, he didn't. Even so, the metrology gods must have heard his silent plea for help because relief arrived in a matter of seconds.

"Sleuth," boomed a raspy voice from directly behind him. "I've got somebody here who would like to meet you." Sleuth bolted to totally upright in the chair where he was hunched over his laptop.

Standing next to Bob Rossi, the lab manager, he saw a strapping, tall, blond-haired guy whose tan indicated he spent a lot of time in the great outdoors.

"This is Todd Anderson from our BHT (Big Honking Truck) Division," said Rossi. "He's here to do some brainstorming with the corporate metrology staffers about some problems he needs to fix at the BHT assembly plant."

"What's it all about?" Sleuth asked.

Here's the pitch

"Time, money, and manpower," Anderson said. "There's a lot of pressure on our division to get our new earth mover models to market faster. On the other hand, engineering needs even more detailed dimensional analyses of our prototype assemblies even to the point of integrating external measurements with some taken from places inside, like in the cab and under the hood.

"These are very big units we have to measure. Sometimes it takes two or three guys and several different kinds of equipment to build up the tooling or measure the bodies. Not only does management want more data faster, they want me to get the job done with fewer people. Is that something you can help me with?"

"Certainly," said Sleuth, without pausing to think. "Come back here to see me tomorrow and I will have some ideas for you." Perhaps Sleuth had found his ticket out of these confined spaces.

Todd Anderson was taken aback by the quickness of the response. He flashed Rossi a look out of the corner of his eye as if to say, "Is this guy alright?"

"OK," he answered, "H1 be back here this time tomorrow."

Starting with a toy

When Anderson returned at the appointed hour, Sleuth was working on one of the lab's DCC CMMs equipped with a rotary table and multiple sensing devices, including a vision probe. Centered on the rotary was a toy dump truck a little smaller than a breadbox. It was similar in many respects to the ones made by the BHT Division, except some Big Honking Trucks were two stories high and nearly 50 feet long.

When the burly Anderson saw this arrangement, he bunched his eyebrows into the shape of storm clouds. Sleuth would have to make his point fast.

"Mr. Anderson," Sleuth began. "Here is a model of one of your products and several sensors capable of measuring or scanning areas of interest from any direction for a full 360 degrees. Because we have sensors that are accurately calibrated to a common coordinate system, we can integrate all the measurements into a single map of the territory. The software does not care which probe collected the data, only that they were aligned properly."

The storm clouds over Anderson's eyes grew darker and deeper and he explode.

"I don't have time for this," he spouted. "I don't care if a single puny guy can measure toy trucks with cross-calibrated probes, automated laboratory CMMs, and a single piece of software. I'm talking trucks so big it takes a minute just to walk around them. We need two or three guys and laser trackers and portable arms, and different kinds of software."

"Well, you should care, Mr. Anderson," countered Sleuth, getting a little angry himself, "because the measurement software people are scaling up their automated multi-probe and sensor automation techniques to answer your big measuring problems.

Who's on first

"First, there is common software that can be used on your laser trackers and portable arms," Sleuth said. "So you won't need specialists in the different measurement systems. That alone might eliminate one person on a measurement or fixture build-up assignment.

"Now, we can't put a real dump truck on a rotary table. But we can set up common coordinates so an entire truck can be measured with a laser tracker from just four corner locations around the truck.

"Of course, the laser tracker needs to follow a target to measure the part. However, that now can be automated so that a single person can set up the software then control it from 'mouse buttons' on the tracker itself.

"If you need to measure points out of the line of sight of the tracker, there are even special hand-held probe holders that accurately can orient different kinds of probes for collecting data points and scans--so frequently you don't have to switch to an arm type measuring system to capture data from these problem areas.

"If the probe holder is out of the line of sight, then, you have to switch to the measurement arm," Sleuth continued. "For example, you can take a measurement arm inside the cab, take all your measurements, and stitch the data back into the common measurement program.

"Once all the data has been collected, individual components can be compared with the same components measured on gantry CMMs in the lab, again using the same software."

Simmering down

Anderson's storm clouds relaxed.

"So you are telling me I can set up my Big Truck measurement tools with common software that one guy can use and stitch everything into a single 3D representation of the results?" he asked.

"That's right," Sleuth said. "So would you like me to come out to the plant and help you get started?"

"Nah," said Anderson. "I've heard enough. I've got to get back to work."

EM Sleuth is sponsored by Wilcox Associates Inc. (www.pcdmis-ems.com), part of the Hexagon Metrology Group and makers of PC-DMIS measurement software.

Contributors to this article include Troy Johnson, product development manager, PC-DMIS Portable, Wilcox Associates, [e-mail]; Rob Fabiano, Sleuth ilustrator: [e-mail], and Joel Cassola, writer, [e-mail]