To enhance milling performance on ISO S materials, Halesowen-based Sandvik Coromant (www.sandvik.coromant.com) has introduced a new series of end mills.

CoroMill Plura HFS (high-feed side) milling cutters are intended for use on workpieces made from titanium and nickel-based alloys, bringing benefits to both aerospace engine and frame applications.

This new cutter range comprises two end-mill families for titanium alloys, and one for nickel alloys.

As chip evacuation and heat are specific challenges when machining titanium, Sandvik has developed a solid version for normal chip evacuation conditions, and another featuring internal coolant and a new ‘cooling booster’ (patent pending) for swarf and temperature control.

The end mills for titanium are available in the grade GC1745, which is based on a fine-grained (sub-micron) cemented-carbide substrate.

A new multi-layer coating that contains silicon is said to provide good wear-resistance and low thermal conductivity. The geometry of the cutters is based on a six-flute concept with no centre cut and an uneven tooth pitch.

Furthermore, the core dimension has been optimised for higher stiffness when machining titanium alloys, while the corner radius, rake angle and relief are all designed specifically for machining ISO S materials.

For nickel alloys, grade GC1710 is used; this features a wear-resistant fine-grained substrate designed to withstand high working loads when machining hard and highly adhesive work-hardened materials such as aged Inconel 718.

Here, a new coating produced using HIPIMS (high-power impulse magnetron sputtering) technology offers adhesion-reducing properties to avoid the formation of built-up edge and increase tool life.

The new cutters are designed to offer high-feed side milling with large axial depths of cut and low radial depths of cut, along with a controlled maximum chip thickness, so that the cutting forces are managed to provide a smooth cutting action.

According to Sandvik Coromant, the result is two-fold: increased productivity provides higher output, while greater tool life and reliability serve to reduce scrap rates in what are typically high-value components.

Further customer benefits include reduced tool cost per component and higher levels of safety.

Target aerospace components include wing and pylon parts made from titanium, as well as engine cases made from Inconel 718.

Applications in sectors such as oil and gas, medical and motor-sport, where titanium and nickel alloys are becoming increasingly prevalent, will also benefit.

To highlight the potential gains available, a customer trial was undertaken on a low-pressure turbine case made from aged Waspaloy 420 — a nickel-based alloy.

Using a horizontal machining centre, the axial depth of cut was increased and the radial depth of cut was reduced (high radial forces are known to create deflection issues).

Comparing a 12mm-diameter CoroMill Plura HFS end mill against a competitor cutter of the same size, the metal-removal rate increased substantially, leading to a 198% increase in productivity.