With 24 million vehicles purchased in 2015, China is now the largest automobile market in the world, and has become a core business for many well known automotive manufacturers and suppliers. To assert itself in this promising but fiercely competitive environment, the Schlote Group, a German series production supplier for the automotive and supplier industry, uses highly automated machine solutions to guarantee faster and therefore more efficient manufacturing of quality products. The company, which specializes in the mechanical processing of complex components of engines, chassis and transmissions, set up 48 high precision machining centers from Schwäbische Werkzeugmaschinen GmbH (SW) for its production site in Tianjin, China, founded in 2013, which enabled them to cut machining times in half.Two different types are in use – the one-spindle BA one6and also the multi-spindle BA W06-22, which is the fastest machine of its size on the market with a feed rate of up to 100 m/min and an acceleration of 2 G. The design of these highly automated systems ensures a significant reduction of loading and clamping processes, which also cuts the amount of work and expenses required.
In 2013 the Schlote Group, a principal supplier of well known automobile manufacturers including VW, BMW, Audi and Porsche, opened its own manufacturing facility in northern China to expand in the largest automotive market in the world while simultaneously being able to develop closer connections with its customers. The anticipated rise in order volume from the existing customer base and new Chinese clients required especially high machining capacities, which were filled in part with the help of a highly automated and powerful machining and production line from SW: "Schlote is especially well noted for producing difficult automotive parts such as transmission. We are able to guarantee that quality products will be produced faster, which has given us an enormous competitive advantage," explains Heiko Thuene, project manager of Schlote Automobile Parts (Tianjin) Co. Ltd. To provide the necessary high production output with high quality and efficiency – VW alone purchases about 900,000 transmissions a year – we have to use machining equipment with outstanding performance while constantly boosting our level of automation and production.
High precision, lower costs
"We use a total of 48 SW machining centers in Tianjin," says Thuene. "Two different types are in use, the BA W06-22 and the BAone6." The BA W06-22 is a "two-spindle + two-station" type and thus a multi-spindle machining center. With its fast feed rate of up to 100 m/min and an acceleration of 2 G, it is currently the fastest machine of this size on the market. "In contrast to machines with only one spindle, it is always able to process two workpieces in parallel," notes Thomas Mäntele, Key Account Manager at SW and responsible for the project. The clamping fixture can be mounted on the fourth or fifth axis, both of which are driven by a torque motor. It is equipped with its own direct measuring system. In addition to its high machining accuracy and dynamic features, the BAW06-22 also offers the advantage that it can be loaded and unloaded with no effect on the main processing time. This reduces work overhead and costs considerably.
"SW two-spindle machines improve efficiency significantly compared to one-spindle machines: While a conventional machine produces a workpiece in 5 minutes, the SW machines needs only 2.5 minutes. This efficiency equates directly to profit for us," explains Thuene. The systems also save space and energy, cut maintenance and salary costs and considerably reduce average manufacturing costs per workpiece due to their efficiency and improved production flow.
Automatic loading and unloading
The BA one6, the new high-precision one-spindle machining center from SW, was adapted to the specific requirements of Schlote.
It is used to supplement the company's BA W06-22 machines.
Since the two machines are structured identically, the BA one6 is ideally suited for combined interlinking. The spindle speed is up to 17,500 rpms, while acceleration to maximum speed lasts less than 0.7 s. Linear and torque motors in the feed axes guarantee maximum precision here as well with a position tolerance of less than 0.005 mm, together with maximum dynamics and short auxiliary process times. The chip-to-chip time is just 2.5 seconds.
The BA one6 is equipped with a double swivel carrier, which is typical for SW. This design concept allows for loading and unloading of a workpiece in parallel to machining time. Because of this, the machine does not have to wait when the blank is being loaded, which allows for uninterrupted machining of the workpiece as well as automatic loading and unloading. This ensures a high level of stability and reliability while improving production efficiency.
Development of integrated solutions
SW also provides support for Schlote in production planning: "Making use of the advantages of shorter cycle times is becoming increasingly important in the automated parts production sector as a way to be able to secure major projects. At the same time, however, the price per workpiece has to be reduced," explains Jiangang Gao, Director of Schlote Automobile Parts (Tianjin) Co. Ltd. "Because of this, SW is also working closely together with Schlote in the area of cost calculations for parts." In this way the production time that will be required for one year is already calculated at the time when the customer reports the quantity of parts to Schlote. "The relevant calculation is very detailed," notes Mäntele. "For example, if 10,000 parts need to be produced for one year, Schlote and SW calculate how many days this will take and how many minutes per day are required." To be able to complete the production assignment according to this calculation, the processes must be designed as automated manufacturing, which represents a great challenge for many suppliers of machining centers.
In addition to high-performance machining centers, SW also provides automated integrated solutions: "In cooperation with our subsidiary SW Automation GmbH, we develop an extensive range of products for our clients for production processes up to and including the finished product," explains Mäntele. This makes it possible for the loading door to remain closed, for example, while the robot portal can load and unload the machine from above on the seventh axis, which is located on top. This has the enormous advantage that the entire machine remains freely accessible. The special gripping technology that was developed for this project is also able to deposit and rotate parts through the temporary storage. A separate line was set up to perform the tasks of deburring, mounting, checking for leaks and fine washing, so that completely finished parts are available at the end.
Plans for shortening the production cycle
The solution installed by SW includes a total of eight highly automated production units which range from picking up the blank to the final optical detection of the finished part. Furthermore, an employee is currently needed at only two stations along the entire production line. To ensure this smooth process and the reliability of products, SW engineers are regularly on site in Tianjin to train employees, update programming or for preventive maintenance of the equipment. "To be able to offer this on-site service to our customers located in China, SW opened a plant in Suzhou at the end of October 2016," explains Mäntele. The company will be working together with Schlote in the future to improve production efficiency continuously: "Our plan for the next project is to reduce the production cycle by 15 percent," says Thuene. "We have set ourselves the ambitious goal of becoming the largest plant in the Group and for the emerging Chinese market."
The SCHLOTE GROUP is made up of eight companies that work together as development partners and series production suppliers for the automotive and supplier industry, casting technology and machine construction. In addition to mechanical processing of products, the range of services includes assembly of components ready for installation as well as design and manufacturing of cast dies, tools and devices. Cast parts from a wide range of different material alloys – essentially aluminum, iron, steel and forged materials – are processed in the CNC machining centers and automated production lines of the Group SCHLOTE products are manufactured primarily using machining processes and a variety of production procedures and technologies. The production lines are designed for small, medium and large series, but individual part manufacturing and prototypes are also available. The Group currently has a total of 1500 employees and 50 trainees.