Improving Bimetallic Block Face Milling

Lightweight bimetal engine blocks, where the main body is made of an aluminum-silicon alloy and the cylinder liner, exposed as it is to high mechanical and thermal loads, is made of grey cast iron (GCI), are a challenge to machine because the properties of the two metals differ widely.

When machining bimetal, the same cutting tool insert is engaged in the cutting of two materials with very different thermal and mechanical properties simultaneously. At elevated temperatures, the aluminum alloy becomes soft and sticky while the GCI material is brittle. Limited tool life, poor surface finish, burr formation, scratches on the face and flaking on the liner are common challenges.

Sandvik Coromant (sandvik.coromant.com) has developed two approaches to making a more stable, cost-effective process. The first is a new face milling tool, the M610, that features inserts which have radial and axial cutting angles and dedicated edge preparation, along with shapes that meet the surface finish and tolerance requirements when milling over the two materials. It is designed to provide high surface quality without requiring any adjustments.

According to Sandvik, it is applicable to operations where full engagement of the cutter diameter over the face is required. According to the company, run-out is close to zero, without burrs, chipping or scratches on the surface.

In cases where there is no need for the cutter diameter to be fully engaged over the face, a tool path can be used that has the M610 complete the machining of the GCI liner before moving over to the aluminum alloy. This approach minimizes instances of the inserts being engaged in both metals at the same time.