Maximum quality with the best possible cost per part

The Spanish automotive supplier Fagor Ederlan S. Coop. has been producing DCT-300 transmission and clutch housings for transmission manufacturer GETRAG for installation in Renault vehicles since June 2017. To meet the especially high quality requirements for workpieces, the manufacturer has purchased high-precision machining centers from Schwäbische Werkzeugmaschinen GmbH (SW) for its machining. The company specializes in challenging, workpiece-specific manufacturing systems for metalworking. The two-spindle BA W06-22 machines that are used not only feature especially precise machining, but also have extremely short cycle times. Among other factors, this is ensured by linear motors in the feed axes, which make it possible to achieve speeds of 100 m/min and acceleration rates up to 22 m/s², as well as the horizontally arranged synchronous motor spindles. To ensure the highest possible productivity and reduce downtimes, Fagor Ederlan uses SW's Remote Service. This service allows for remote diagnostics and online error rectification by SW service engineers when needed. The systems are also already equipped for individual status monitoring for the SW life data services. Fagor Ederlan is currently testing the use of these services as part of its launch of Industry 4.0.

To manufacture DCT-300 clutch and transmission housings for GETRAG in 2017, Fagor Ederlan needed the right machining centers to be able to produce in the required delivery quantities. "Our in-house team, which is responsible for defining the Machining Industrial Model (MIMEK), had previously already defined type SW BA W06 machines as the most suitable machining centers for machining aluminum powertrain and suspension parts," explains Inaki Duandikoetxea, Purchasing Manager at Fagor. "

Higher workpiece output thanks to two-spindle machining

"The essential challenge in machining metal parts is to produce the required quality for the component in the shortest possible cycle time," explains Matthias Dreher, Key Account and Regional Sales Manager at SW. "The advantage of two-spindle SW machines is that two parts can be machined in parallel during one work cycle. The quality requirements for transmission and clutch housings are very high," explains Dreher. As part of a feasibility analysis, SW therefore verified in advance whether the workpieces can be manufactured in two-spindle operation, especially within the required tolerances. An analysis of the machining process showed that the two-spindle W06 more than met Fagor Ederlan's requirements for accuracy and quality. According to calculations, the cycle time could also be achieved for each cycle and thus the best possible cost per part.

The special fundamental concept on which the application of the selected BA W06-22 at Fagor Ederlan is based also contributes significantly to this: The machining center, which has two horizontal working spindles with a low startup time and high acceleration in the feed axes, is designed essentially for 4- and 5-axis machining of light metal workpieces. The monoblock as the bearing machine bed minimizes sagging and ensures optimum flow of force between the workpiece and tool.

To allow for the high acceleration rates of the machining unit with a minimum machining installation surface of 19.87 m², the monoblock is designed as a steel construction. Duandikoetxea explains the advantages of the design: "The monoblock construction was very interesting for Fagor Ederlan because it not only ensures even temperature stability, but also greatly facilitates transport and installation at the operating location with a crane hook solution." In addition, the machining unit was also designed with a "box-in-box" concept, which ensures high rigidity with low weight. The entire rear end of the machining unit is inserted into the monoblock and the machine area with the freely accessible components is protected against swarf ejected from the working area by a combination of steel and textile covers.

The use of linear motors in the feed axes X, Y and Z makes it possible for the BA W06 to achieve speeds of 100 m/min and acceleration rates up to 22 m/s². Linear motors have significant advantages over conventional drive via ball screws in terms of energy, wear and noise emission. SW was able to achieve this reliability and precision in part due to the gantry drive of the Y-axis used for the BA W06-22: "We connected two physically separated feed drives Y1 and Y2, each consisting of a linear motor, a direct absolute distance measuring system and a drive controller, coupled electronically on the control side," explains Dreher. "This guarantees optimum positioning accuracy, even with eccentric loading." An overall positioning tolerance (Tp) of 0.008 mm can be guaranteed, even at maximum machining speeds.

The two synchronous motor spindles of the BA W06, each with 35 kW of power, have a core spindle with a very low mass moment of inertia. This not only allows for the high torque of 80 Nm, but also a spindle startup time of just 0.7 seconds to the maximum speed of 17,500 rpm. This results in a nearly constant chip-to-chip time of 2.5 seconds for the entire speed range.

Even if the quality requirements and tolerances should change, Fagor Ederlan will still be well equipped with the SW machines: "The two independent Z-axes of the BA W06-22 are a critical part of this. If quality requirements should become so high in the future that they can no longer be implemented with two-spindle machines, it is possible to perform more precise machining with one spindle while the second spindle waits in the background," explains Dreher.

SW is currently consulting with Fagor Ederlan regarding possibilities for embedding the machine park in an Industry 4.0 environment. At present, Fagor Ederlan is using the Remote Service of Schwäbische Werkzeugmaschinen GmbH and is considering also using the life data services offered by SW. This makes it possible to monitor and document all processes and work steps in real time using the SW CloudPlatform. The data derived in this manner is made available to the customer to optimize processes and also to improve work sequences. After the necessary sensors have been installed, energy data such as consumption of electrical power or compressed air can also be visualized and evaluated for sustainable energy management.

Fagor Ederlan is very pleased with the collaboration: "Machining centers from Waldmössingen have been part of our machine park since the end of the 1990s, and we have always been fully satisfied with how they work. The first machines were implemented with commercial agent Daunert Maquinas Herramientas from Barcelona. Ever since then, the productivity of our machining processes has steadily increased, while maintenance and replacement costs have been considerably reduced. We now have a significant number of SW machines in use around the world. Duandikoetxea sums up: "SW is not just a supplier for us, they are a partner contributing to our worldwide growth." In May 2019 SW will celebrate its 20-year anniversary with Daunert.