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From prototyping to manufacturing, increase productivity with AT960, LAS-XL and T-Scan 5
Volvo Car Body Components (VCBC) is an automotive factory with 2,400 employees and manufactures millions of body parts each year. The unit produces large sets of stamped parts for vehicles such as bonnets, roofs, doors, other subsets, and ships them assembled (in whole or in part) to Volvo plants around the world, for the latest assembly and finishing.
The modern, high-tech, environmentally friendly olofstrom plant has a history of nearly 300 years. It was established as a steel plant in 1735 and has been supplying body parts for all Volvo cars since 1927. Purchased by Volvo in 1969, this structure has been dedicated for 50 years to stamping and partial assembly of parts for the entire volvo vehicle lineup, and for external customers such as Volvo Trucks, Ford and Land Rover. The first steps in Volvo's vehicle design are largely based on the development of sheet metal machining tools developed and produced by the Tool-Die team in Olofstrom. The team is primarily responsible for prototyping the tools. Knowing that a set of up to 80 tools are needed for a vehicle, a task can take four to five months. Each project usually lasts one year. The rest of the time is dedicated to the manufacture of 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 tool manufacturing to improve productivity. It has identified several stages of design, manufacturing and validation 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 MMTs to structured light scanners. She studied different systems available on the market, but one of the key criteria was to find a solution that could be used both in the manufacturing workshop and in the quality assurance laboratory. Since the team already applies several Absolute Tracker systems in the main parts production areas in Olofstrom, and is familiar with this technology, as well as the portability and flexibility of Absolute Tracker systems, the choice of additional Hexagon laser tracker systems seemed natural.
Improved initial moulding
The first step in manufacturing a prototype designed or the final tool is the precision milling of a molded block of raw material. Casting is not a specific operation, and the molded part usually contains an excess of raw material, which must be milled in size and shape with a digitally controlled mill. As the milling machine and the machined part move before milling, the absence of a collision between the two is a key preparation step for the machining. Such a collision could cause costly damage and downtime on the digitally controlled mill. This is why the operator must take into account a safety factor when making the adjustments, and place 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 it amounts to running the machine without machining for a while at the beginning of the milling program. "This initial scan data helps to avoid a waste of time,"says Kim Tingstedt, operator in the Tool-Die service at the VCBC plant in Olofstrom. If you optimize the milling program to get the desired size of the material, it saves you a lot of time, because the processing speed is the same when the machine runs empty or plants the material. Our millers now have better processing time, which allows us to accept more parts and tools. This optimization had been done before, but the complete scan data provided by the LAS-XL simplifies the processes. "When scanning, our manufacturers get more information than with the previous MMT solution, which only provided points. So they can see a lot more with the scans," says Kim Tingstedt. "They can use this data with the digital control machine and optimize milling more easily because they really see the part." This cast scanning data can be used in another way to improve production. Tool casts are extremely heavy and difficult to move. Any possibility of lightening therefore improves usability and reduces the amount of raw material needed to make them. Their size should be as small as possible, but also not too small. If there is not enough material between the outer part of the tool and the inside of the precision mold, the piece will not be robust enough to withstand repeated high-power machining. Using the scan data after moulding, the moulding of consecutive prototypes and end tools can be refined to minimize the weight and use of raw material, without diminishing the structural integrity of the tool. This also allows the miller to machine the part at a closer distance with each iteration, saving operators time at each stage. The Leica Absolute Scanner LAS-XL is the perfect tool for this scanning. Its wide scanning line and long working distance allow the molded part to be scanned very quickly. Scanning is thus an interesting solution, faster than simply taking into account a large safety factor when milling. Thanks to the working distance of the LAS-XL, the largest on the market, it is possible to measure points inside the tool cavities, which reduce the material used and the final weight. A long-distance working scanner like the LAS-XL allows accurate measurement of these cavities, so the Tool-Die team can continue to reduce the raw material used and weight without compromising the functionality of the tool.
Quality assurance of the final tool
After the milling phase, the accuracy of the final tool must be checked. This step requires finer measurements than with the LAS-XL. But because the Absolute Tracker AT960 offers many compatible scanning solutions, the team was able to simply invest in an ultra-dynamic scanner to meet these needs. The Leica T-Scan 5 quickly verifies both the accuracy of the moulding area of the milled tool and any test stamping, by comparing the data with a CAD model. This process is much faster in the past and reduces the prototyping phase by ensuring design-compliant production in a much shorter time frame. "The tool is brought to the manufacturing workshop to manufacture the first part," says Johanna Persson, from the Quality Assurance department. "We scan the part to see if 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 and prevents us from rebuilding an element. The scanner can also be used in other manufacturing phases, to control the accuracy of the part and for tool maintenance. The Tool-Die team periodically provides quality assurance for parts by using the T-Scan 5 for quick scans. And if another team is responsible for the continuous maintenance of the tools, it now relies on the new equipment of the Tool-Die team to diagnose problems: a tool that has already been on the production line and does not produce satisfactory parts can be quickly inspected in the workshop thanks to the portability of the Absolute Tracker and T-Scan 5.
This quick identification of the causes of manufacturing defects saves a lot of time compared to a fixed installation in the quality assurance laboratory, especially when it comes to parts as difficult to move as sheet metal auto parts machining tools. The ability to switch between different scanners and use these systems for many inspection applications is one of the key advantages that has driven the Tool-Die team in Olofstrom to invest in an Absolute Tracker. "We've studied a lot of scanning systems, and flexible use was an important criterion for us," says H-kan Nilsson, Volvo Group's Director of Research and Purchasing. The Tool-Die team was even able to use the Absolute Tracker AT960 for the initial alignment of the big press. This unique process was extremely easy to perform with the AT9 tracker, reflectors and Verticality function.
Learn by doing
After receiving the tracker and scanners, the team was able to operate the equipment without much assistance from Hexagon. "[The Absolute Tracker] is well known at Volvo. We've been using it for a very long time and therefore had the necessary expertise," notes Fredrik Sjoberg, an engineer in the prototype department at Volvo Car. "Hexagon intervened in the basic training, but we knew what we were doing from the start. We already had a portable scanner with PolyWorks, and this additional acquisition was just a new system with the same principle of use. Since then, new team members have been easily introduced to the system through exclusively internal training. This equipment is so easy to use that the team does not need a codified training system. All you have to do is attend a demonstration. Beginners learn on the job by always working with more experienced users who monitor operations and can give advice.
The future of measurement
The Tool-Die team at the Volvo Car Body Components centre in Olofstrom has been very impressed with the performance of Hexagon's new scanner systems, and is already considering introducing other advanced measurement systems into the service. It uses several large MMTs 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, the team has many opportunities to achieve additional productivity gains with Hexagon.
