Scanner and probes inspect 'body-in-white'

Leica T-Probe and Leica T-Scan provides more useful information on body-in-white assembly accuracy and enables problems to be solved quicker at DaimlerChrysler.

The first thing you'd notice while walking up and down the seemingly endless corridors of DaimlerChrysler's sleek, ultra-modern Bremen plant is the almost complete absence of people.

Hundreds of robots go about their work with surgical precision, bringing different sheet metal parts into place, welding them together, moving completed parts onto the next station and transporting finished products overhead to maximise space utilisation.

Viewed from afar, the ubiquitous robots seem to be dancing.

The few factory workers you do see use 'old school' bicycles to jet between different parts of the factory: hi-tech and low-tech harmoniously coexist here side by side.

Technological progress in the manufacturing processes has meant that more daring body shapes can make the leap from the designers' drawing board to the assembly line.

In the not-so-distant past, cars had relatively simple, square shapes, with individual parts fitting to one another along more or less straight-forward lines.

On the other hand, modern cars boast far more complex shapes than the cars of yore.

And the task of inspecting how these parts fit to one another has gotten increasingly more complex as well.

The Body-In-White (BIW) Rollout and Process optimisation Department tackles exactly that task: it is entrusted with the job of inspecting how the various body parts fit to one another.

More importantly, based on their measurements, feedback is given to the production facilities so specific, targeted adjustments can be made on the tools.

Operational engineer, Henning Siemers is involved in BIW measurement and inspection tasks.

He explained: "Our job is to assure dimensional accuracy of the entire body-in-white.

Of course, every BIW consists of many individual parts, and they must all fit perfectly.

Our primary duty is to inspect the entire BIW, both individual parts and the whole vehicle, including the panel gaps, and then analyse the data we get".

Siemers continued: "Based on the analysis we perform, we then go back to the production facilities and make adjustments to the tools and make sure that what comes out is an automobile whose parts fit together flawlessly".

In the past, Siemers' department has relied on hand-operated measurement instruments.

However, it is the shape complexity of today's cars and the ever-increasing tolerances that have pushed such instruments against their limits.

Siemers said: "Viewed in retrospect, cars used to be made of almost square-like segments which used to fit nicely together without much hassle.

Nowadays, cars are much more curvy, with round areas suddenly changing shapes and meeting other panels at all kinds of angles and lines.

Plus, the much higher requirements for the nearly seamless fit between individual panels mandate that we work with very tight tolerances".

"With the shapes of our vehicles getting more complex, we have been on the lookout for new technologies that deliver," said Siemers.

"Our quality engineer, Karl-Heinz Boecker, has been attending the CONTROL trade show in Sinsheim, Germany each year, and he had his first encounter with the Leica T-Scan system a couple years ago, when it was still just a prototype.

Based on the announced specs, we knew this could be something for us, but we wanted to wait until we were positive that the product was truly ready for the market.

The primary issue that we saw with many of the other scanning solutions out there was that the software could not keep up with the hardware.

Collecting all those points is relatively simple, but what do you do afterwards? We were under the impression that many manufacturers did not award the same attention to the software as they did to the hardware".

A few months ago, Boecker's team arranged a Leica Geosystems product demonstration at their facilities.

A Leica .840 Laser Tracker coupled to a Leica T-Probe and Leica T-Scan - the top-of-the-line combination - was chosen.

And the Leica system delivered.

"It was immediately clear to us that the Leica T-Scan and the PolyWorks software were a mighty combination.

We already knew that the Leica T-Scan was a great sensor, and we were also shown that the PolyWorks suite is a worthy match for it.

The software is very capable, and we knew we would be on the right track." Since the system delivery, the Leica T-Probe/T-Scan system has been used, among other things, to measure panel gaps, examine part curvatures, inspect reference holes and similar.

Siemers has also been busy testing different applications for the Leica T-Scan system.

"One of the new applications we have found is inline calibration.

In the past, BIWs were inspected by being placed inside a grid station and measured using conventional CMM equipment.

When you have 150 pallets and want to measure with high tolerances, you're quickly reaching the limits with traditional methods.

That's why we wanted to be able to measure inline, both the pallets and the tools, and this is where the Leica T-Scan system will come into play.

Another application of interest to us is the inspection of the entire robot path, and this is something we plan on doing in the near future." Asked about what has changed since the implementation of the Leica T-Scan system, Siemers is very specific: "By relying on scanning, I am in the possession of much more useful information.

The quality of part analysis has improved, we are able to get to the root of a problem much more quickly, therefore coming up with targeted solutions for what needs to be changed, for example intervening at the tools at such and such point and changing the parameters based on the results seen in PolyWorks." And benefits of using the Leica T-Probe/T-Scan system are manifold.

"We really appreciate the portability.

With the Leica Geosystems equipment, I can gather all the information I need in just 2-3 hours and perform the analysis later.

This way, I am not blocking production for too long because the system lets us work in parallel: while one operator is taking the measurements, another one can already be working on sorting out the results." The fact that the system is modular is important to Siemers' team.

"We purchased a Leica T-Probe at the same time we got the Leica T-Scan.

Tactile wireless measurement is of great value to us when we measure easily twistable parts like the hood.

We perform a quick measurement with the Leica T-Probe to get a rough idea about the condition of the part.

If we were to start scanning immediately, it would take longer to realize that the hood is twisted.

With the Leica T-Probe, collecting just a few points will let us know fairly immediately how we are doing.

And we are performing this within the same software, merely switching between the Leica T-Probe and the Leica T-Scan." The Leica T-Probe/T-Scan combo measures within a range of 15m, giving the technicians a volume of 30m in which they can operate.

This give Henning Siemers and his team peace of mind in knowing that should the measurement requirements change in the future, they are well equipped for working in a measurement volume large enough to accommodate several BIWs at once.

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