From prototyping to manufacturing, boost productivity with the AT960, LAS-XL and T-Scan 5
Volvo Car Body Components (VCBC), based in Olofström, is an automotive plant with 2,400 employees that manufactures millions of body parts every year. The unit produces large assemblies of deep-drawn parts for vehicles, such as hoods, roofs, doors and other sub-assemblies, and ships them assembled (in whole or in part) to Volvo plants around the world for final assembly and finishing.
The modern, high-tech and environmentally-friendly Olofström plant has a history of almost 300 years. It was established as an ironworks in 1735 and has supplied body parts for all Volvo cars since 1927. Purchased by Volvo in 1969, the facility has been dedicated for 50 years to the stamping and partial assembly of parts for the entire Volvo vehicle range, and for external customers such as Volvo Trucks, Ford and Land Rover. The early stages of vehicle design at Volvo are largely based on the development of sheet metal working tools, designed and produced by the Tool & Die team at Olofström. The team is primarily responsible for tool prototyping. Given that a set of up to 80 tools is required for a vehicle, a job can take four to five months. Each project usually lasts a year. The rest of the time is devoted to manufacturing the final tools, used to stamp hundreds of thousands of body parts.
In 2018, the team decided it was time to introduce a modern metrology solution for prototyping and toolmaking, to improve productivity. It identified several design, manufacturing and validation stages that could benefit from the application of advanced measurement systems. With a large, well-equipped quality assurance laboratory, the team was already familiar with a wide range of metrology equipment, from horizontal arm CMMs to structured light scanners. They looked at different systems available on the market, but one of the key criteria was to find a solution that could be used both on the shop floor and in the quality assurance laboratory. As the team already applies several Absolute Tracker systems in the main parts production areas at Olofström, and is familiar with this technology as well as the portability and flexibility of Absolute Tracker systems, the choice of additional laser tracker systems from Hexagon seemed a natural one.
Improving initial molding
The first step in manufacturing a designed prototype or final tool is the precision milling of a molded block of raw material. Casting is not a precise operation, and the molded part usually contains an excess of raw material, which must be milled to the specified size and shape using a CNC milling machine. As both the milling machine and the machined part move prior to milling, avoiding collision between the two is a key machining preparation step. Such a collision could cause costly damage and downtime to the CNC milling machine. That's why the operator must take a safety factor into account when setting up, and position the machine far enough away from the raw material to avoid a collision. This operation is not easy to perform with the naked eye, and often amounts to running the machine without machining for some time at the start of the milling program. " This initial scan data saves timesays Kim Tingstedt, operator in the Tool & Die department at VCBC's Olofström plant. If you optimize the milling program to obtain the desired material size, you save a great deal of time, because the processing speed is the same whether the machine is idling or machining the material. Our milling machines now have better processing times, enabling us to accept more parts and tools.. " This optimization had been done before, but the comprehensive scan data provided by the LAS-XL simplifies processes. " When scanning, our constructors get more information than with the previous CMM solution, which only provided points. So they can see a lot more with the scans. "explains Kim Tingstedt. " They can use this data with the CNC machine and optimize milling more easily, because they can actually see the part. "This mold scan data can be used in other ways to improve production. Tool castings are extremely heavy and difficult to move. Any possibility of lightening them therefore improves usability and reduces the amount of raw material needed to make them. Their size should be as small as possible, but not too small either. If there isn't enough material between the outside of the tool and the inside of the precision mold, the part won't be strong enough to withstand repeated high-power machining. By using post-mold scan data, we can fine-tune the molding of consecutive prototypes and final tools, to keep weight and raw material usage to a minimum, without diminishing the tool's structural integrity. This also enables the milling machine to machine the part at a closer distance with each iteration, saving operators time at every stage. The Leica Absolute Scanner LAS-XL is the perfect tool for this scanning task. Its wide scan line and long working distance enable the molded part to be scanned very quickly. This makes scanning an interesting solution, faster than simply taking into account a large safety factor when milling. Thanks to the LAS-XL's working distance, the longest on the market, it is possible to measure points inside tool cavities, thus reducing the material used and the final weight. A long working distance scanner like the LAS-XL enables precise measurement of these cavities, so that the Tool & Die team can continue to reduce the raw material used and the weight without compromising tool functionality.
Quality assurance of the final tool
After the milling phase, the accuracy of the final tool must be checked. This stage requires finer measurements than with the LAS-XL. However, as the Absolute Tracker AT960 offers a number of compatible scanning solutions, the team was content to invest in an ultra-dynamic scanner to meet these needs. The Leica T-Scan 5 can be used to quickly check the accuracy of both the moulding area of the milled tool and any test stamping, by comparing the data with a CAD model. This process is much faster than in the past, and reduces the prototyping phase by guaranteeing design-compliant production in a much shorter time. "The tool is taken to the production shop to machine the first part," says Johanna Persson, from the Quality Assurance department. " We scan the part to check that it is correct and, if not, to determine the cause of the problem. The tracker and scanner allow us to identify the problem very easily. This scan data gives us more information at an early stage, so we don't have to rebuild a part. "The scanner can also be used in other manufacturing phases, to check part accuracy and for tool maintenance. The Tool & Die team periodically ensures part quality assurance, using the T-Scan 5 to obtain fast scans. And if another team is responsible for ongoing tool maintenance, it now relies on the Tool & Die team's new equipment to diagnose problems: a tool that has already been on the production line and is not producing satisfactory parts can be quickly inspected on the shop floor, thanks to the portability of the Absolute Tracker and T-Scan 5.
This rapid identification of the causes of manufacturing defects saves a great deal of time compared with a fixed installation in the quality assurance laboratory, particularly when dealing with parts as difficult to move as sheet metal automotive machining tools. The ability to switch between different scanners, and use these systems for a wide range of inspection applications, is one of the key benefits that prompted the Tool & Die team at Olofström to invest in an Absolute Tracker. " We looked at many scanning systems, and flexible use was an important criterion for us. "Håkan Nilsson, IT R&D and Purchasing Manager for the Volvo Group. The Tool & Die team was even able to use the Absolute Tracker AT960 for the initial alignment of the large press. This unique process was extremely easy to perform with the AT9's tracker, reflectors and Verticality function.
Learning by doing
After receiving the tracker and scanners, the team was able to operate the equipment without much assistance from Hexagon. " [Absolute Tracker] is well known at Volvo. We've been using it for a very long time, so we had the necessary expertise. ", notes Fredrik Sjöberg, engineer in the prototype department at Volvo Car. " Hexagon was involved in the basic training, but we knew what we were doing right from the start. We already had a hand-held scanner with PolyWorks, and this additional acquisition was just a new system with the same operating principle.. " Since then, new team members have been easily introduced to the system through exclusively in-house training courses. The equipment is so easy to use that the team doesn't need a codified training system. All they have to do is attend a demonstration. Beginners learn on the job, always working with more experienced users who monitor operations and can offer advice.
The future of measurement
The Tool & Die team at the Volvo Car Body Components center in Olofström has been very impressed by the performance of Hexagon's new scanner systems, and is already planning to introduce other advanced measuring systems into the department. She uses several large CMMs for quality assurance, and sees potential in the use of programmable automated systems for a number of applications. With structured light scanners and robotic systems controlled by an Absolute Tracker, among others, the team has plenty of scope for further productivity gains with Hexagon.