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face milling of automobile engine cylinder head with pcd inserts

The cylinder head in an automobile engine is coupled to the top of the cylinder block. It has holes for valves and spark plugs and it contains part of the combustion chamber. Some vital aspects of engine performance including fuel efficiency depend on the condition of the cylinder head which is usually made of aluminum. To provide high speed machining with superb surface finish, polycrystalline diamond (PCD) inserts are used in virtually all machining centers and automobile shops for roughing, finishing and re-surfacing of this vital car component. Here are some cutting conditions and inserts used for face milling of cylinder heads.

Top Face Milling
The areas that require milling on the top face are concentrated at the edges of the cylinder head. Hence, face milling should be done at relatively low cutting speed, with a small cutting depth, using a tool grade that is suited for interrupted cutting. With a cutting speed of 1,500 m/min, a cutting depth of 0.3mm and a feed rate of 0.15 mm/tooth, a high quality surface finish can be achieved. The square-shaped tipped polycrystalline diamond insert, SCGT 0602, is suitable for roughing while the finishing operation may be completed using the SNEW 0602 pcd insert with a wiper cutting edge.

Bottom Face Milling
The bottom face of the cylinder head will be in direct contact with the top of the cylinder block. So it should have a surface finish quality of 2 μm. To achieve this, the roughing operation can be done with a cutting speed of 1000 m/min, feed rate of 0.25 mm/tooth and a cutting depth of 3.0mm. For better precision during the finishing milling operation, increase the cutting speed, and reduce the depth of cut and feed rate. The square-shaped insert, SDET1204 or SCET1204 may be used for rough milling. Each insert offers high wear resistance and efficient chip removal. For the high speed finishing operation, use the SNEW 1204 or SNEW 09T3. SNEW 1204 works better for longer cutting depth with a slower speed while SNEW 09T3 works better at a higher speed with a shorter cutting depth.

End Face Milling
The two end faces should be milled carefully to ensure proper alignment with the cylinder block. The cutting speed may be 1000 m/min or lower, while the cutting depth should not exceed 3mm. A diamond tipped pcd insert like the WPGT 0402 may be used for roughing since it has an 11 degree clearance angle and a chip breaker. The WCGW 0402 with a wiper design may be used to produce the desired surface finish. This wiper design allows the cutting speed and feed rate to be increased without any adverse effects on the surface finish. Thus, the overall efficiency of the milling operation will be enhanced since machining at a high feed rate improves productivity. The wiper offers a better surface quality than the conventional chip breaker so it is better to use the WCGW 0402 pcd insert for finishing.

Conclusion
Using these polycrystalline diamond inserts will help to improve cutting efficiency and lead to a more economical machining process. All the pcd inserts discussed above are standard ISO inserts which will perform well under the suggested machining conditions.

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