Synera
Assembly Line
BMW goes bionic: A closer look at BMW's 3D printed robot grippers
Laura Griffiths speaks to Jens Ertel (JE), Head of BMW Additive Manufacturing, and Markus Lehmann (ML), Head of Installations Technique, Robotics, about BMW’s design and deployment of customised 3D printed robot grippers.
For the topology optimisation we first needed a so-called design space. This is the region or volume within which the optimisation algorithm is allowed to distribute material in order to find the optimal structural design. The design space represents the available physical space or domain where the structure can be placed. Additionally, the non- design spaces are defined. These are mostly mounting plates that are needed to later fasten add-on parts and to attach the gripper to the robot and that will be integrated in the bionic structure during the optimisation. After that, the forces and torsional moments acting on the gripper are estimated and the allowed deformation is defined. Also, the material properties and a minimum strut thickness are set. With all these values and some additional details the topology optimisation can be started. Through the clever combination of two different optimisation approaches, the resulting geometry of the optimisation is already of such high quality, that only minor manual editing of the design is necessary. The usually time intensive redesign of a topology optimisation result is replaced by an automised workflow, that accelerates the design process enormously. The optimisations of the bionic grippers were done in the software Synera.
The gripper for the CFRP roof production at the Landshut plant utilises a mix of different 3D printing processes to take advantage of the unique benefits that each technology offers. The selection of these processes was driven by the technical and economic considerations for the specific components of the gripper. The approach is not to simply ‘print everything’, but rather to use the 3D printing technology that provides the most benefits for each individual component. This strategic approach ensures that the overall gripper design is optimised for both technical performance and cost- effectiveness. For the vacuum grippers and the clamps of the needle gripper used to lift the CFRP raw material, the selective laser sintering (SLS) process was selected. SLS allows for the production of these intricate and complex parts with the required precision and durability.
On the other hand, the large roof shell and bearing structure of the gripper are manufactured using large-scale printing (LSP) technology. LSP is well-suited for producing large, stiff components in an economical and sustainable manner. Furthermore, in a subsequent optimisation step, the weight of the bearing structure was reduced even further. This was achieved by employing aluminium sand casting technology, where 3D printed shapes and cores were utilised. This approach allowed the full potential of topology optimisation to be exploited, leading to a significant reduction in the overall weight of the gripper.
BMW Group expands use of 3D-printed, customised robot grippers
The BMW Group now also manufactures many work aids and tools for its own production system in various 3D printing processes. From tailor-made orthoses for employees, and teaching and production aids, to large, weight-optimised robot grippers, used for such things as CFRP roofs and entire floor assemblies. At the “Additive Manufacturing Campus” in Oberschleißheim, the BMW Group’s central hub for production, research and training in 3D printing, more than 300,000 parts were “printed” in 2023. Furthermore, over 100,000 printed parts were produced per year across all the plants that form the global production network, from Spartanburg and the German plants to sites in Asia.
Additive manufacturing processes have been used on a daily basis for a long time at BMW Group Plant Landshut. For many years, these have included moulds for the manufacturing of aluminium cylinder heads, which are printed three-dimensionally using the sand casting process. Here, sand is repeatedly applied in thin layers and stuck together using binders. This makes it possible to create moulds for the manufacturing of very complex structures, which are then filled with liquefied aluminium.
For a number of years, the BMW Group’s Lightweight Construction and Technology Centre in Landshut has been using a particularly large gripper element, which was made using the 3D printing process. Weighing around 120 kilograms, the gripper for a robot can be manufactured in just 22 hours and is then used on a press in the production of all CFRP roofs for BMW M GmbH models. The press is first loaded with the CFRP raw material. The gripper is simply rotated 180 degrees to remove the finished roofs. Compared to conventional grippers, the version manufactured using 3D printing was roughly 20 percent lighter, which in turn extend the operating life of the robots and also reduced wear and tear on the system, as well as cutting maintenance intervals. The combined use for two steps also reduced the cycle time. A unique feature of the robot gripper is the ideal combination of two different 3D printing processes. While the vacuum grippers and the clamps for the needle gripper to lift the CFRP raw material are made using selective laser sintering (SLS), the large roof shell and bearing structure are manufactured using large scale printing (LSP). LSP can be used to produce large components economically and sustainably. The process uses injection moulding granules and recycled plastics, while CFRP residual material can also be used and recycled. Compared to the use of primary raw materials, CO2 emissions when manufacturing the gripper are roughly 60 percent lower.