Involves selecting tools for the semifinishing and finishing of the blade contour. These are based on blade-size, machinery and methods. To achieve optimum results, the choice of tool needs to be in relation to the amount of material and the sculptured surface. The CoroMill 300 round insert cutter is an excellent profiling cutter for five-axis machining, with good clearance, light cutting action and a broad range for semi-finishing. It is capable of high-feed semi-finishing with an extra-close pitch version with, if any, only minimal vibration tendencies. The 12 and 8 mm IC inserts, in different geometries, can be selected along with diameter and pitch for optimum performance.
Semi-finishing and finishing the aerofoil is profiling passes with CoroMill Plura solid carbide end mills or with exchangeable heads in CoroMill 316. The semi-finishing operation will influence the surface finish achieved in the final finishing operation. The aim should be to generate a very regular, uniform level of residue material, if necessary through two semi-finish operations. Vibration tendencies are another factor that affects the quality result which can be affected by the cutter engagement, feed, approach and cutting action of the tool employed.
The CoroMill Plura programme is a modern development of solid carbide end mills in advanced grades for all component materials. The geometry development has taken the demands of milling in today’s machines. Flute depth is varied and has been adapted to suit cuts providing best core stiffness and space for efficient chip evacuation in blade machining.
End milling operations have been largely dominated by two somewhat overlapping application areas as regards tool types – indexable insert cutters and solid carbide cutters. These areas have been segregated mainly by tool-diameter, operation type and the component finish required. Indexable insert end mills have no upper diameter limit but, for practical reasons, have a lower diameter limit – often 12 or 16 mm. Solid carbide end mills, on the other hand, can be of diameters down to tenths of a mm but usually have an economical upper diamater-limit around 25 mm.
As regards type of operations and finish, indexable insert cutters are flexible, high metal removal rate tools, well suited for most operations while solid carbide cutters have close tool-tolerances and can provide high finishes and accuracy, especially at large axial depth of cut thanks to long radial cutting edges.
While a solid carbide tool is one, complete precision tool, integrated from shank to cutting edge, an indexable insert tool is made up of two tool elements which means broad variation and optimization possibilities. In between the two areas provided by the indexable insert and solid carbide tools, there is a potential area for an alternative tool solution which overlaps both. One that provides both cutting edge indexability and the benefits of solid carbide tooling for small to medium size end mill diameters.
The CoroMill 316 exchangeable head milling system has the sophistication of Plura solid carbide cutting edges combined with an advanced coupling between head and tool shank. It offers very extensive capability with a programme of Plura heads where the range of shanks provide broad machine tool suitability. The CoroMill 316 tooling is balanced by design and so capable of relatively high spindle speed. It combines the advantages of tool-cost efficiency with tool-handling efficiency. The combination of high speeds and multi-tooth head options provide the capability of very high feed rates as well as high cutting speed. The exchangeable-head concept also makes it easier to adapt the cutter geometry to various workpiece materials and conditions. The design of heads provides good machining stability and minimized tool deflection tendencies through helix and differential pitches.