What do drilling platforms, natural gas storage facilities, offshore work vessels and industrial power plants have in common? They all depend on the energy supply provided by gas and diesel engines. In these demanding fields of application, high efficiency and absolute reliability of such engines are crucial. Jinan Diesel Engine Co., Ltd. (JDEC) manufactures highquality gas and diesel engines and generators in Jinan City in the Chinese province of Shandong. A recent addition to the company's product range posed an unprecedented machining challenge: rough milling, semi-finishing and finishing of MAN engine blocks. This prompted a successful cooperation between JDEC and the German heavy-duty machine tool expert WaldrichSiegen.
Two WaldrichSiegen ProfiMill portal milling machines proved the perfect solution for the task at hand: they reduce the machining time by more than half. When JDEC became a licensed manufacturer of MAN 32 V and 32 L motors in 2010, it was clear that merely finding a machine supplier for the processing of motor block castings would not be enough. "What we needed was a turnkey solution," recounts Mr. Yu Haibo, Vice Managing Director of JDEC's Plant No. 01. "We were looking for a partner to provide the necessary equipment, the entire application technology, machining methods and CNC programming to turn the castings into finished engine blocks. We knew this would require vast experience in the field." WaldrichSiegen, one of the worldwide market leaders in the manufacturing of heavy-duty machine tools for milling, turning, grinding and texturing, has been an expert in designing and building customized machine tools for diesel engines for many decades. In the tender process, two of its state-of-the-art ProfiMill portal mills with a setup width of 3,000 mm, a setup length of 8,000 mm and 6,000 mm respectively, and a clearance of 4,000 mm between the columns left the competition far behind.
"A diesel engine block is one of the most demanding cubic workpieces. It can weigh more than 20 tons with a complicated shape and very high requirements in terms of accuracy. The cylinder bore, for example, is up to 610 mm deep. It must be perfectly positioned in relation to the bearing bore," Yu Haibo explains. The ProfiMill portal mills with a milling power of 100 kW at the tool center point combine a number of features to meet these requirements: the major components are made of high-quality cast iron and all machine axes are hydrostatically guided. A backlash-free hydrostatic worm drive in the X-axis ensures dynamic stiffness and high positioning accuracy. The Y-axis (saddle on cross rail) is driven by an electrically preloaded master/ slave drive for outstanding accuracy in terms of positioning and feeding forces. Controlled vertical and horizontal head clearance results in excellent cutting performance and surface qualities. "When machining MAN 32 diesel engines, the increase in efficiency and accuracy is immediately noticeable," Yu Haibo reports.
One of the main challenges in manufacturing motor blocks is the machining of surfaces and bores that are very difficult to access. "This is why we complemented the machines with special equipment," Knud Müller, Head of Sales at WaldrichSiegen, explains. "They feature eight special milling units each. These can be switched easily by the help of an automatic changing system." The units are attached at the unique WaldrichSiegen Masterhead interface. The Masterhead concept, with only the drive shaft integrated in the RAM while the bearings and milling spindles are located in the attachments, features several advantages, among them prevention of heat generation and thus geometrical problems, as well as extremely high stiffness at the Masterhead interface. In addition, the machines are equipped with automatic tool changers with 192-pocket racks. In combination with the sophisticated measuring and control technology, the various tools and milling units fulfill even the most complicated machining duties competently and efficiently: "During critical machining tasks, as for example at the bearing hole for the crankshaft, elaborate measurements are no longer necessary. They only have to be performed sporadically now, which results in shorter machining times," Knud Müller explains. According to Yu Haibo, the flexibility of the portal mills is a major advantage in his production facility: "The machines use many different tools and attachments for the machining of different areas, which directly improves the machining efficiency. Compared with other machines, the machining time is reduced by more than half."
In late 2012, the milling machines were put to the test in WaldrichSiegen's headquarters in Burbach, Germany: four MAN 32 V engine blocks had to be machined, meeting the performance standards defined by JDEC. The result: "The machines fulfilled our high demands in terms of accuracy in the acceptance test, especially during heavy-duty metal cutting involving great stock removal," Yu Haibo states. Two teams of JDEC staff received extensive training in Germany for ten weeks each in order to start machine operation immediately after commissioning. After the machines have been in operation at the Jinan City headquarters for well over a year, Yu Haibo reports that the ProfiMill portal mills continue to save considerable machining time: "The special equipment allows for fiveside machining in one single setup.
Sufficient experience to provide a turnkey solution, outstanding precision and flexibility to perform the complex machining tasks at hand and efficient operation were among the deciding factors for the successful cooperation between JDEC and WaldrichSiegen. But yet another important condition had to be met to seal the deal: local aftersales service, specifically perennial technical support, maintenance service and quick access to spare parts were paramount. German Machine International Trading, WaldrichSiegen's service and spare parts unit near Shanghai, meets these requirements to JDEC's full content: "We are thoroughly satisfied with the WaldrichSiegen team in this regard," Yu Haibo concludes. "We always receive feedback very quickly and WaldrichSiegen also offers helpful suggestions for the maintenance and operation of the machines."