10 aeroSPaceManUFactUring | noveMber 2009
GettinG creative with
carbide tooling
Cavity milling: The CoroMill 790 reaches the parts other endmills cannot reach
Solid carbide tools have largely taken over from high speed steel (HSS) end mills
for aluminium cutting due to their especially sharp edges and geometries that
provide low cutting forces and plenty of chip space for unobstructed material
evacuation. But, as tooling manufacturer Sandvik Coromant explains, the
technology can be taken even further.
T
he benefits of using carbide have new edge, insert, insert seating and location and clamping.
made it the dominant technology clamping technology. The establishment of a satisfactory
in the market. For example Conventional indexable inserts have model that calculates and predicts
it is three times stiffer than HSS, tended to be comparatively blunt for cutting forces accurately was one of
reducing deflection to a third of that aluminium, often leading to a ploughing the main foundations of the new insert
demonstrated by indexable insert tools. effect, cutting thin chips when finishing. geometry. Advanced FEM simulation
Carbide tools can also be given a helix to The entry of the edge into the cut has presented many of the answers to the
provide a very smooth entry and exit into also tended to be abrupt, leading to a combined design of edge line, rake
and out of cuts and yield a smoother chip sudden rise in cutting force magnitude. angle and chip former, as well as the
flow. This all amounts to a minimised Together, these properties result in development and optimisation of a new
cutting force variation and vibration. cutting forces that introduce excessive edge feature on the insert clearance face
Indexable insert tooling still tool deflection and power requirements. – a precision primary relief land – based
has a place in the rough machining on calculations of vibration wave shapes
of aluminium when medium to large A new approach from measured modal parameters.
diameter tools are used. Tool regrinding The issue is made more complicated by It is a well known phenomenon that
is eliminated and the security, versatility the need for an edge that needs to be in cast iron milling, the formation of
and metal removal capacity of end both sharp and positive for finishing, flank wear on the clearance face of the
mills with inserts provide aluminium and capable of high removal rates when cutting edge leads to some dampening of
machining with unequalled capability. roughing. Consequently, there is a vibration. The worn ‘land’ starts to grind
Finishing, however, has in many cases genuine requirement for a new approach against the machined surface, absorbing
been problematic, but this has now to indexable inserts, focusing on energy and resulting in the vibration
been addressed by Sandvik Coromant’s resultant cutting forces, edge entry, chip amplitude being modulated. With the
CoroMill 790 tooling, which features formation and stability, as well as insert CoroMill 790 tooling the challenge has
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