Micro-forging is actually a special method of manually flattening and sharpening the blade on a scythe or sickle through the act of hammering and is commonly used in rural areas. In the process adopted by Starrag, a special, electrically powered tool is used instead of a hammer. Placed within a machining centre, this tool shapes components to the final contour with μm precision. “In principle, the micro-forging tool is like any normal tool that can be inserted into the machine and subsequently controlled by the CNC,” Product Manager Michael Koller explains. “On an LX 051, we can demonstrate how this process can be used to ultimately replace the act of polishing.” The fact that roughness values of 0.2 μm (Ra) can be achieved in a reliable process with a high level of repeating accuracy is a point in favour for this alternative to grinding.

During machining, a pulsed impact ball hammers rapidly (up to 600 Hz) with high power. Micro-forging compresses the boundary surface layers to a depth of 10 mm. Initial practical tests show that the process is significantly more precise, more targeted and more controlled than the widely used shot-blasting method. “We are currently working hard on retrofitting all machines used to produce turbine blades – in other words, all LX series machines,” says Koller. This upgrade will enable all turbine blade manufacturers to replace polishing, frictional grinding and shot-blasting tasks with the micro-forging process, thus significantly shortening their process chain and cycle times. It is astonishing how Starrag has breathed new life into the well-known micro-forging process by drawing on cutting edge technology.