What’s Empowering Machining Technology in Power Generation
Shops have many choices to handle large, heavy parts as well as small, delicate parts. Tight tolerances, tough alloys and complex geometry are the challenge.
Turbine casings are typical power-generation parts that are large and heavy, often requiring machines that feature adequate torque, high precision throughout a large work envelope and rigidity to avoid chatter.
Turbine casings. Blisks. Rings. Gears and gearboxes. Blades to repair or renew. Dealing with complex parts of many sizes in tough materials is a special challenge for companies involved with machining for power generation. The fact is, the need for energy is increasing and/or changing around the world. We want power generation to be environmentally clean and safe, readily connectable to distribution networks and responsive to fluctuations in demand. We want energy to be cheap and plentiful.
Typically, companies that machine components for power generation coordinate these operations with other manufacturing services requested by customers. These services may include inspection, nondestructive testing, welding and assembly. Because certification, documentation and customer support are overarching concerns, machining companies often take ownership of secondary processes such as coding, plating and heat treating by managing services provided by outside suppliers.
Large, heavy parts are common in power generation. Double-column gantry machines with five-axis capability (usually for 3+2 positioning) often handle the largest pieces. A bed long enough for one or more workpieces to be set up while another is being machined is a valuable feature to minimize downtime. Automatic exchange of machining heads in the vertical ram helps automate production. Inspecting parts in place with portable measurement systems such as a laser tracker reduces part handling and setups while ensuring the accuracy of the machining process.
Because power generation involves many parts of rotation, vertical turret lathes (VTLs) are popular for turning operations. Most parts that must be turned have features such as holes at odd angles, pockets and slots. Often, angle heads and a programmable rotating table can be used to complete these parts in one setup. Workholding to accommodate easily distorted workpieces with thin walls is a concern, as is the need for long-reach modular tooling to work around flanges and overhanging features.
Blades and blisks are generally processed on CNC machines with full five-axis machining capability. These parts are often handled in numbers large enough to warrant high-production techniques, such as automated pallet changing and multitasking capability. Specialized cutting tools, CNC programming for blade-milling tool paths and probes with advanced scanning capability distinguish these operations. Applications of additive processes that enable used blades to be restored to original stock conditions and then re-machined in one setup is a significant trend.
A surprising number of shops that focus on power generation have abrasive waterjet machines for cutting large and/or thick plates. Wide-bed machines with programmable tilting heads (for straight, perpendicular edges where required, as well as angles and tapers for gear-tooth shapes and the like) are preferred. The ability to cut many types of workpiece materials, including high-strength alloys with no special tooling is a big plus for abrasive waterjet machining in power-generation applications.