New machining method for ‘fir-tree’ profiles

Birmingham-based Delcam plc is working with Iruba (a German provider of engineered solutions) and the machine tool manufacturer Hermle to develop a five-axis machining method — programmed with the PowerMill CAM system — for creating ‘fir-tree’ profiles in components for turbo machinery. The new process is based on the trochoidal machining (milling) strategies in PowerMill and has been patented by Iruba. It allows complex ‘fir-tree’ profiles to be produced on milling machines, such as the Hermle C60 five-axis machining centre, rather than having to use specialist broaching equipment.

The use of the trochoidal strategies in Delcam’s PowerMill offers a number of benefits, in particular giving high material removal rates with lower — and more consistent — cutting forces (this consistency ensures higher accuracy in the position and shape of the slots, with minimal thermal effects on the surface of the profiles). The process also reduces the number of specialist cutting tools that are required — and cuts the machining time for steel alloys by 30-40% compared to alternative standard milling solutions, giving a time almost equal to broaching.

Mattias Rutschinski, managing director of Iruba, said: “At IMTS, we presented — with Hermle and Delcam — a world premiere by milling small fir-tree geometries in IN718, which is a typical material for aero-engine parts. The presentation made it very clear to visitors that milling is the more-effective technology, since we could mill curved slots, deburr them and measure them in one process on Hermle’s smallest five-axis machine, the C22.”