Schabmüller Automobiltechnik GmbH has been manufacturing the Porsche Macan’s pivot bearings since 2013.
Schabmüller Automobiltechnik GmbH has been manufacturing the Porsche Macan’s pivot bearings since 2013. Machining is performed with the aid of the high-precision BA W06-22 and BA one6 machining centers from Schwäbische Werkzeugmaschinen GmbH (SW), which are specially designed for demanding tasks in series production. The high precision of the machines is essential, especially in the automotive industry, since the high quality requirements allow only low tolerances. While the two-spindle BA W06-22 is used for the main bearing bore, strut and wishbone connection, the brake caliper connection is performed in a second step on the single-spindle BA one6. In the case of the latter alone, it was possible to integrate and realize a significant increase in quality in the production process.
The fact that the machining of the 1,700 sets of swivel bearings produced weekly at Schabmüller for Porsche takes place on two different types of machines was a conscious, strategic decision by the automotive supplier from Großmehring: With the production of the main bearing bores, the gooseneck connection (suspension strut support) and the wishbones, 90 percent of the machining takes place within the cycle time required by the end customer Porsche in a hemisphere access from above on the two-spindle BA W06-22. The size of the component and the annual number of units to be produced determine the number of spindles. Since the machining of the brake caliper connection cannot be realized in the OP 10 due to the workpiece clamping and the machining portion is much lower, this machining step is performed on the single-spindle BA one6. “This means that the processing steps of OP 10 and OP 20 can be carried out in parallel,” explains Helmut Häckl, technical manager at Schabmüller. In addition, the BA one6 can also be used to compensate for production peaks if necessary.
In order to meet the strict criteria of the automotive supplier – among other things, the position tolerances in each axis may be only two to three hundredths in some cases – the SW machines are precisely matched to these fields of application. This virtually eliminates errors, as a pneumatic support control system checks whether the component is correctly clamped in the fixture – otherwise the process will not start. Deviations can thus be registered and corrected immediately. In addition, the tool planning system control increases process reliability by checking the tool at the HSK interface of the spindle. Linear drive technology in all axes, which in contrast to the ball screw drive exhibits extremely low wear, also enabled the cycle time required by the end customer to be realized and a permanently consistent workpiece quality to be achieved. The thermal expansion of the direct drives is also significantly lower than with conventional drives, so that high long-term accuracy can be guaranteed. In addition, the machines are partially or completely overhauled in-house at Schabmüller every three to five years in order to guarantee high-precision production in the long term.
One of the fastest machining centers: BA W06-22
The BA W06-22 used, with a spindle distance of 600 mm, is characterized among other things by its minimum chip-to-chip times of 2.75 s, which enable high-precision machining of light metal workpieces in the shortest possible time. Most importantly, it requires only 0.7 s ramp-up time from 0 to 17,500 rpm and achieves main drive axis acceleration values of up to 2 G, making it one of the fastest BAZs currently on the market. The working space per spindle is 600 x 600 x 500 mm.
In addition, the machine is designed in monoblock construction, which minimizes deflection and ensures optimum force flow between the machining unit and the workpiece carrier, and with a box-in-box 3-axis unit specially developed for highly dynamic machining operations in the light metals sector. This 3-axis unit is designed as a welded steel construction, so that the moving masses are kept low with maximum system rigidity. “It is inserted into the back of the monoblock, and the horizontal arrangement of the work spindles allows the chips to fall freely,” explains Matthias Maier, Sales Manager at SW. A double-swivel beam with integrated rotary axes (Torque) also enables loading and unloading to take place in parallel with production. In addition, the SW machines are designed to be ideal for loading and unloading with a robot, even from above via a gantry.
BA one6 delivers position tolerances of < 0.005 mm
The single-spindle BA one6, which like the BA W06-22 is designed for machining workpieces made of non-magnetic materials such as aluminum or titanium alloys, offers a work envelope of 600 x 650 x 500 mm. “The focus of this model type is on machining with the highest accuracy requirements,” says Maier. Linear and torque motors in the feed axes also guarantee maximum workpiece accuracy with a position tolerance of less than 0.005 mm with maximum dynamics and very short non-productive times. The chip-to-chip time is only 2.5 s.
The BA one6 is also equipped with a double swivel carrier for loading and unloading workpieces during machining. Since the design of the machine is identical to that of the BA W06-22, it is ideally suited for joint interlinking: It serves as a suitable supplement to multi-spindle production lines for single-spindle pre- or post-machining of large light metal workpieces, but also to compensate for production peaks when, for example, a two-spindle machine is not sufficient and a three- or four-spindle BAZ cannot be used due to the component size.
Expected savings through increased quality and integration of process-safe manufacturing
Overall, Schabmüller achieves high machining quality and a reproducible manufacturing process by using the SW machines. This has a significant impact on the resource of personnel in the areas of quality assurance and maintenance. In addition, the optimization of the cutting data reduces the processing time in the BA one6. In order to prevent machine downtime, SW also offers remote maintenance and diagnostics or preventive maintenance in the form of PULSE services, in which a specialist calls into the respective machine and informs the customer of the necessary steps. “In general, it is always a matter of preventing machine downtime – because this can have far-reaching consequences for the customer and result in high costs,” Maier summarizes. Service workshops are held regularly between Schabmüller and SW for this purpose. The resulting optimization proposals are then implemented by the machine manufacturer in terms of development. ” We pay particular attention to the problems and requirements of our customers and also develop specifically for the users,” says Maier, explaining SW’s work. In this way, technology is always worked out on an individual basis.
“We chose SW machines because the high quality provides the necessary peace of mind for the project,” reports Häckl. “This not only saves us time, but also money. In addition, we have been working with SW since 1994, so there is mutual trust and the necessary technology is already in house.” Another important factor is the smooth production expected with these machines within the project durations of four and a half to five years. “Viewed over this period, such
considerable costs are saved that we would certainly have had to invest in repairs or the like during this period if we had bought in ‘cheap’,” Häckl estimates.
Schabmüller currently has a total of 21 SW machines in operation. Several of these are automated by bartsch GmbH, which has been part of SW since 2015. By 2019, a second hall in Großmehring will be successively equipped with SW machines, in which another 17 automated machining centers will be used. Up to 680,000 cylinder head covers are to be produced there annually for the end customer Audi.
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