This is why the machining of these complex workpieces usually requires two separate, specialised machine tools. WaldrichSiegen and UnionChemnitz have now developed a universal rotor slotter that allows for the efficient machining of both workpieces on a single machine.
The innovative machine concept, available in the UK from agent MT Squared, is the result of a collaborative effort between the experts in heavy-duty machine tools for this application, WaldrichSiegen, and its sister company UnionChemnitz, a specialist in manufacturing horizontal boring and milling machines with more than 160 years’ experience.
The rotor slotter is specifically tailored to the requirements of a large American power plant manufacturer. It is based on UnionChemnitz’s most powerful horizontal boring and milling machine, the PCR 260, with a spindle diameter of 260mm, a power of 128kW and a torque of 19,000Nm, combined with a sophisticated, CNC-controlled set-up system designed by WaldrichSiegen and UnionChemnitz.
The rotor slotter machines rotors with a length of up to 15,500mm, a diameter of up to 2,400mm and a maximum weight of 150 metric tons. It is equipped with a Fanuc 30i control. Depending on the workpiece, it adapts to the various machining tasks required with a range of boring and milling units which can weigh up to four tons. Outstanding stability is therefore one of the machine’s most vital qualities. The machine bed is made of extremely robust, vibration-absorbing cast iron. A fully hydrostatic guidance system guarantees high precision and protection from wear even when performing heavy-duty machining.
Both the heavily ribbed column and the RAM are designed for extra stiffness. Double hydrostatic guideways enclose the RAM completely, resulting in excellent vibration damping and reliable long-term stability. When slotting generator shafts, a disk cutter with a diameter of 1,250mm slots is mounted which can mill grooves with a depth of 125mm in a single cut, applying 111kW of spindle power at a torque of 33,000Nm, and removal rate of about one ton per hour.
A major challenge in machining rotors is aligning the workpieces in the machine tool, a time-consuming process which often takes up as much as eight hours’ valuable machining time. The set-up system automatically adjusts the rotor once it has been placed into a highly precise clamping device, reducing the set-up time to approximately an hour. Based on data gathered by state-of-the-art measuring devices, numerically controlled, hydrostatic steady rests position the rotor with micron accuracy, while bearing a weight of up to 80 tons each. Absolute set-up precision is crucial for various demanding machining tasks performed with the rotor slotter – for example when machining flange bores which form the connection between turbine and generator, to tolerances of 10µm.
The rotor slotter meets each specific machining challenge with customised spindle units, milling heads and tools and the appropriate NC programming solutions – curved fir tree grooves in turbine rotors for example, an extremely complex machining task, are pre-machined with a large bell cutter and finished with a finger cutter. An automatic tool changer allows for quick and efficient switching between machining applications.
WaldrichSiegen and UnionChemnitz are specialists in integrating custom solutions and believe that process integration is the key to success; flexible machining concepts allow for a broad range of applications with a single machine.
Solutions specifically tailored to customers’ requirements by UnionChemnitz include a boring mill with a high-speed rotary table for turning operations and a boring mill equipped with a grinding unit. WaldrichSiegen recently built a mill turning machine with an integrated grinding unit.
By combining their expertise in developing innovative machine concepts, WaldrichSiegen and UnionChemnitz have advanced the flexible machining of workpieces for the energy industry. The rotor slotter is distinctive in its universality, allowing for complete machining of both generator and turbine rotors.
MT Squared www.mtsq.co.uk
