Reconnecting with its rich pre-WWII history, over the past 15 years as part of the VW Group Škoda has transformed itself into a modern automaker offering a complete lineup of passenger vehicles, sharing engines and mechanical components across the board with its corporate brethren. It has also become a sort of new model playground, often being used to launch the first model in a particular VW Group vehicle family. For example, the just-released Škoda Fabia is the first vehicle to sport VW’s new subcompact platform, to be shared later by the forthcoming VW Polo and Seat Ibiza.
The plant in Mladá Boleslav is home to Škoda’s Prototyping Department under the leadership of Jan Novák. When it comes to metrological tasks, the department operates as a service provider to the entire technical development structure within the company. Until 1993 the department relied solely on traditional probing methods of inspection, but these provided too few reference points, especially when dealing with curvatures, so Škoda decided to branch out to photogrammetry, whereby the pictures were either of large parts or of specific vehicle parts where higher tolerances were necessary, such as vehicle interiors.
As technology advanced, Mr. Novák’s department started looking for new equipment that would expand the capabilities of their light projection equipment. For some measurement tasks, such as inspecting tooling, mobile probing would be optimal, while applications such as inspecting vehicle interiors called for digitizing surfaces as the logical choice.
Monika Grubnerová from the Prototyping Department talks about the equipment selection process: “Earlier in the process, another manufacturer of laser trackers was considered, but their proposed solution for inspecting vehicle interiors was to implement an articulated arm from their product portfolio. This solution did not comply with our requirement for digitizing surfaces.
Besides, an articulated arm was out of the question for us due to its measurement volume limited to just a couple of meters. In addition, frequent repositioning of the articulated arm adds to the general discomfort of use. That’s why we decided to obtain the newest three-in-one Portable CMM system from Leica Geosystems consisting of a Leica Laser Tracker, a wireless, armless Leica T-Probe and a hand-held high-speed Leica T-Scan, leading the pack in the VW Group. The benefit that immediately sprung to mind was the fact that we could simply bring the CMM to the part rather than the other way around.”
The system was delivered in the Summer of 2005, and since then it has been gathering no dust. In their role as a service provider to other departments, Mr. Novák’s team utilizes their portable CMM equipment in a plethora of different ways. The main areas of use include but are not limited to verifications of welding tools, surface verification of drawing tools, digitalizations of physical models, virtual assembly and inspections in the final vehicle assembly.
Monika Grubnerová explains: “When we are finished with setting up welding tools, we are able to quickly inspect them with the Leica T-Probe and implement modifications where necessary. In our capacity as an internal service provider, it is our explicit task to sign off all of our welding tools and ’release’ them into production. Thanks to the Leica T-Probe system’s portability, we can easily move it around within the plant’s premises, eliminating the need for time-intensive transportation of the tools themselves.”
Another application is the verification of the drawing tools. After being manufactured according to the CAD files, hand-made modifications are done on a per-need basis. In the next step, surfaces are verified using the Leica T-Scan, so that possible changes can be made to the original tools. The “showcase” application of the Leica T-Scan is the inspection of interiors and digitizing scale models of vehicles. David Vanek, who works in constructing prototypes and scanning models, elaborates: “Before we migrated to the Leica T-Scan, inspecting vehicle interiors was a challenging task due to the tight space in which we have to measure, placing limitations on the size of the equipment we are able to bring inside a vehicle. Besides, many surfaces we need to inspect are hard to reach. Neither an articulated arm nor a traditional CMM machine are suitable for this. With the Leica T-Scan, we can inspect in the tightest of quarters, ’reaching’ even minute gaps at the points where different surfaces meet.
An additional argument that spoke in favor of the Leica T-Scan was the fact that the laser beam automatically adjusts the intensity of light for each point, seamlessly adjusting to the varying characteristics of the surfaces being scanned. This makes it possible to digitize parts that differ in color or reflect light differently. Plus, when we digitize final models, we are absolutely not allowed to spray or powder them because these models are going to be shown in various presentations, so we have to be able to scan them without modifying them in any way.”
Virtual assembly will probably be the next growing field of application. A scan of a metal sheet part can be imported into the CAD data of the vehicle, including the information about gap requirements. The software can then give the user feedback about the plausibility of assembly or if there are some collision issues to first work out.
In the past, the only option to solve a measurement issue in the assembly was to transport the entire measurement object and bring it into the metrology lab. Jan Novák: “This process could easily rob us of one to two work days. But we wanted to be able to measure in one part of the building today and be somewhere completely different tomorrow, without having to move any of the parts because that would cause a workflow interruption. Secondly, we needed a machine that can measure points and can digitize surfaces. In practice, we first gather just a couple of preliminary points with the Leica T-Probe to get a rough idea how individual parts fit to one another. To conduct a detailed analysis of individual sheetmetal parts, we use the Leica T-Scan. This is a time-efficient way to look for sources of errors that causes minimal disruption to the manufacturing process and yields very accurate results.”
David Vanek provides the final thought: “If one thinks about what it means to develop a car, it all starts in the design stage. At that stage, it is extremely useful to be able to digitize surfaces to get the preliminary information about the model. Once a life-size clay modem is made, being able to digitize it becomes particularly interesting, and we also need to inspect hard-to-reach spaces like the interior. After that, the next step is to build a prototype, and for that we need to build welding and drawing tools that also require inspection. Finally, the next level is to bring the system to the assembly plant and inspect how different parts fit to one another. The flexible nature of the Leica Geosystems equipment lets us perform both tactile inspection and digitize surfaces without having to worry about the measurement object’s size or reachability. From the logistical point of view, it is much easier to move the CMM machine, and that’s why we needed a portable CMM machine. Yet despite all this moving, the system is so stable, we haven’t needed to perform any intermediate alignments so far, which speaks volumes about its robustness.”