Sandvik Coromant’s CoroMill® 790 provides new edge to aluminium milling

The machining of aluminium parts such as aerospace frames, involves the roughing and finishing of cavities, shoulders and edges, demands both high metal removal rates and good quality surfaces. Until now, indexable insert tooling has not provided the comparably small cutting forces and the soft entry into cut offered by the helix of a solid carbide cutter.

Now however, extensive calculations, Finite Element Method (FEM) simulations and testing, along with new grinding and measuring technology, has created a unique combination of new insert geometry features for use with CoroMill 790. These include:

An optimized rake angle that makes the edge sharper but retains strength
A more flowing cutting edge that lowers the initial shock of edge entry
A chip former that results in less frictional contact and better chip direction
A primary relief land that acts as a buffer and dampens vibrations as they arise.
Radial cutting forces are responsible for much of the tool deflection in radial finish milling. The carefully designed primary relief land has a significant steadying effect, breaking the force amplitude that results in tool chatter. In combination with the larger rake angle and sharper cutting edge, the reduction in force magnitude is considerable.

Furthermore, the fact that aluminium has a low melting point means that temperatures in the cutting zone will never rise to those that threaten cemented carbide inserts, thus opening up the way for very high cutting speeds. However, with higher spindle speeds come higher power requirements, so any force-limiting effect is of considerable value. The new insert geometry for CoroMill 790 offers a distinct reduction of power.

Axial cutting force, directed down against the surface machined under the end mill and thus critical for the many thin-walled aluminium structures used in the aerospace sector, is also reduced considerably.