Automated Series Control for Pressed Parts
Series Control (Sample Checks) for Pressed Parts
BMW Group, location: Regensburg, department: Press shop
JOB DEFINITION / STARTING SITUATION
The BMW plant in the south of Regensburg employs approximately 9,000 people. Every day, more than 1,100 vehicles are produced over a total area of 140 hectares. Since the plant went into operation in 1986, total production has increased to 5.4 million units per year. The production program includes the BMW 1 Series (3 door, 5 door), the BMW 3 Series and BMW M3 Saloon, the BMW 4 Series as well as the M4 Convertible and BMW Z4.
In the press shop, up to 550 tons of steel are processed every day into large car shell parts as well as structural and reinforcement parts for the range of vehicles manufactured at the site. The quality of components plays a particularly important and central role in the automotive industry. Therefore, the components formed must be checked after the manufacturing process for surface quality and dimensional accuracy.
In 2010, this requirement led to the first conversion measures and investments in quality assurance, and, in particular, optical measuring technology from ZEISS Optotechnik, for instance for the series production of the second-generation BMW 1 Series.
For the production of the sixth-generation BMW 3 Series, further extensive investments were made in 2012 in the pressing plant, in bodyshell construction and in logistics. The measuring system described below is the second-generation, fully automated measuring technology currently in operation in Regensburg pressing plant.
The aim pursued by the use of the optical measuring method was to check samples of the sheet-metal parts as quickly and completely as possible for characteristics relevant to quality. 3D digitizing, in other words the creation of a digital image of the object to be checked and downstream analysis against the CAD reference, appeared the method most suitable for achieving this objective.
Having already entered the field of fringe projection technology in 2010, 2012 saw the company build on the experience it had gathered so far, which resulted in it setting new goals for a next-generation measuring system. The main field of application for this system was still to be series control (sample checks) for pressed parts. However, analyses and sampling also needed to be possible. The system was to check individual components of 200 x 200 x 200 mm, such as strike plates and reinforcements, right through to side frames made from aluminium, steel or high-strength steels, with differing levels of lubrication and sizes of up to 3500 x 1500 x 500 mm.
In addition, one absolute exclusion criterion was that the components should not have to be prepared beforehand with white contrast spray, which can be required in scanning procedures now and again for shiny surfaces.
BMW Regensburg's requirements regarding sensor accuracy were as follows:
• System accuracy: < 0.1mm
• Repeat accuracy: Temperature +/- 2 K, range < 0.1mm
• Absolute accuracy: Reference standard (measurement uncertainty < 0.1mm)
The system was to be built in a new measuring room, located directly between the press outfeeds. The system chosen was the sensor COMET®Automated, which had been developed specifically for robot operation, mounted on KUKA robots and a linear axis. With this decision, BMW Regensburg stepped up its already strong collaboration with the high-tech company from Neubeuern, near Rosenheim.
In 2013, a new measuring room was set up in the pressing plant at BMW Regensburg, positioned directly between the press outfeeds. The centerpiece of this measuring room is a robot-assisted system, which is split into two separate measuring areas. The decision was made to use an automated 3D digitizing system, again from ZEISS Optotechnik, because of the previously successful collaboration and its innovative system solutions.
SOLUTION AND PRODUCT
Based on the considerations above and extensive tests and analyses of various suppliers, an automated 3D digitizing system from Carl Zeiss Optotechnik GmbH was installed in 2010. This was a robot-mounted COMET 5 for process optimization and work reduction in initial sampling. The successor measuring unit designed in 2012 will now be described in more detail:
The measuring unit was positioned directly at the press outfeeds in a new measuring room. The centerpiece of the system is the aforementioned sensor COMET®Automated, which boasts an innovative, virtually maintenance-free, extremely slim and flexible sensor concept, as well as bright LED illumination technology. It is a device for a wide variety of applications in the field of automated 3D digitizing. The tried-and-tested one-camera technology of Carl Zeiss Optotechnik GmbH ensures the best possible data quality, leading to the very highest level of accuracy in the measurement results. Furthermore, the sensor can be adapted very flexibly (depending on measuring task) to all conventional robot systems thanks to two flanged parts.
The photogrammetry system (measurement of marks and reference points) used here as a supporting system for large objects before the actual scanning process is slim and fully integrated in the sensor. The sensor therefore remains especially compact, despite its numerous technical features, which means that it can be used generally for almost all applications, also where access is difficult, e.g. in vehicle interiors.
The system itself is split into two separate measuring areas with two locking plates each, where one is operated lying down and one standing up. These locking plates are each 1800 x 4000 mm in size. One of the many advantages of this robotic measuring system is therefore that optical measurement may be performed in one work area, while the other is already being retooled. These two areas are connected via a linear axis, on which the KUKA robot can move. This leads to considerable time savings. This system also takes occupational health and safety factors into consideration. For instance, modern and slim light curtains are installed to protect the work areas. These were chosen instead of a fixed enclosure, for optical reasons among others. This gives the system an attractive appearance and means that it does not dominate the measuring room.
The system is activated and operated using the simulation and offline and online programming software VISIO 7, developed by ZEISS Optotechnik. The downstream analyses also run fully automatically via the analysis software INSPECTplus, which comes from ZEISS Optotechnik as well.
RESULT / BENEFITS FOR THE CUSTOMER
Since 2013, measuring technicians have been testing components using the COMET®Automated system in two-shift operation. At present, for example, they are inspecting the engine bonnets of the current generation of the 3 Series Saloon. The main advantage over the conventional method using coordinate measuring equipment, which is also used in the measuring room, is that it delivers quick information about a component in its entirety. Thanks to the full-surface measurement, presentation and analysis of the object, trends in the production process can be identified and analyzed rapidly.
In addition to automated operation, a stand-mounted COMET system is also operated in the measuring room. This sensor too offers the highest level of detailed precision and considerable flexibility when scanning. The sensor is also currently being used for sample checks.
ADVANTAGES / STATEMENT
• innovative maintenance-free yet also cost-effective LED lighting technology with long service life
• excellent data quality and highly accurate measurement results
• short working distance for fast, efficient inspections
• adaption to several robot types / manufacturers
"Using the ZEISS Optotechnik 3D Digitizing system, we are now able to perform geometry validations of our components effectively and very fast. The layout of the automated system, realized by ZEISS Optotechnik, allows sample checks on two separate measuring areas. Using the COMET Automated sensor is very efficient. Thus, we can also increase the number of pressed parts being analyzed."
Measuring technician, press shop, BMW Regensburg
Watch the video: COMET Automated at BMW Regensburg - Automated optical 3D Digitizing