BMW motorcycles are known for their reliability, quality, performance and safety. This is not achieved by chance, however. BMW’s motorcycle plant in Berlin, Germany, uses a variety of tools to create numerous key components on-site, from frames and valve shafts to connecting rods and cylinder heads. Among the tools used are Grob’s horizontal five-axis G550 machining centers featuring Siemens’ Sinumerik 840D controllers, used to manufacture cylinder heads for flat and four-cylinder engines.
When BMW invests in new machining centers, it compares among various suppliers to ensure that the machining center will enable the company to manufacture components more cost-effectively than external contractors.
Grob’s five-axis G550 horizontal machining center was the right choice for BMW, which was looking for a reliable machining center with familiar Siemens controls to manufacture cylinder heads for its motorcycles.
One of BMW’s primary reasons for choosing the G550 was because it was equipped with a Siemens CNC. Thanks to previous positive experience with Siemens, the manufacturing specialists in Berlin already employed the company’s CNCs for 90 percent of their controllers. This offered both operators and tool setters the flexibility to work on practically any of the machines in the plant. Other key machine spec requirements included adequate space for manufacturing all relevant components, high levels of precision and surface finish, compliance with predefined cycle times, and the ability to reuse all current tools and equipment.
Before committing to the new investment, BMW production engineers worked to investigate the effectiveness of the Grob machines in cylinder head production. Initially, it was the G550’s near-identical sibling, the G350, that was under consideration. However, the working space available was deemed too small to accommodate all the required processing tasks. The G550, on the other hand, satisfied that requirement. Among other factors, the horizontal design of the G550, which has both rotary axes in the work area, contributes significantly to its high rigidity. As a result, axial deviation remains under 10 micrometers. The level of precision that can be achieved is correspondingly high, even when processing hard materials such as those used for valve seat inserts. The machine also produces a high-quality surface finish, with roughness ranging to 2 micrometers.
According to Christian Heiß, applications engineer at Grob, another benefit of the horizontal design was that “tool life can be increased by approximately 30 percent compared with that of vertical machining centers. The problem of jammed slivers is almost completely eliminated because they are not able to fall onto the workpiece in the first place, but instead fall right through to the ground.”
One of the G550’s strengths is its compact footprint of 3,800 × 6,300 mm. Despite its size, the machining center features a Z-axis stroke of 1,020 mm, meaning that tools as long as 500 mm can be retracted completely out of the work area and into the spindle tunnel. The swivel-mounted shuttle table is another feature that helps deliver high levels of productivity. While one workpiece is being processed, the next can be clamped and set, minimizing downtime.
Thanks to its usability and intuitive operation through various technology cycles, measurement cycles and setting functionality, G550 machines can be set up for new batches quicker than what BMW used before. According to Heiß, setups that would have previously taken several hours can now be accomplished in a matter of minutes.
According to the company, employees have found the G550’s Sinumerik 840D controls easy to use and intuitive.
Along with the tools and equipment from the current machines, the German motorcycle manufacturer was able to reuse all its existing programs as well. It took a single employee only two days to upgrade these programs to be compatible with the latest software, which can be loaded onto the relevant machine as required either over the network or from a USB flash drive. The modern Windows Explorer-style program manager means that complex programs can be managed either on the Compact Flash (CF) card or directly on the CNC.
If problems arise while the machine is operational, BMW Production Engineer Taner and his colleagues use the network-based remote maintenance functionality provided by Grob. Although Ögretmen reports that it has rarely been required so far, the process has proved to be extremely smooth and efficient.
Grob can also perform minor optimizations together with Siemens using the teleservice. This is usually done automatically and without any disruption to ongoing production.
The Sinumerik-controlled Grob machines have met every expectation in full, which is why BMW has already ordered an additional four G550s.