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composite material milling and chamfering with pcd inserts

Composite material milling is now one of the fastest growing areas of application for pcd diamond inserts. Materials like carbon fiber reinforced plastic (CFRP), green ceramic, fiberglass, Kelvar, stacked metal composites, and super alloys of aluminum and titanium, create unique challenges for precision machining. However, with the use of specially designed or standard polycrystalline diamond pcd inserts, and the careful assessment of the qualities of each composite material, it is possible to achieve high precision machining, with high quality surface finish. Here are some important points to note when choosing full faced milling inserts and tipped pcd inserts for machining and chamfering of composite materials.

Features of Composite Materials that Affect Machining
One of the major challenges posed by composite materials is that they are not homogenous. For instance, carbon fiber composites have fibers mixed with thermostatic resins. So unlike what happens when machining a pure metal like aluminum or copper, as the cutting tool removes material from the surface, subsequent layers of material may not come off as smoothly as the first layer. Hence, the setting of cutting speed, feed rate and depth of cut most done with care. Preferably, some of the material will have to be tested first to determine the optimum cutting speed. Such milling operations may require frequent interruptions and the stop and start times must be pre-determined at the beginning of the operation.

Some roughing milling operations may require the removal of a large amount of material at high rpm. During such operations, it is vital to guard against the occurrence of both splintering and delamination of the finished surface. In such cases the operator may have to make use of indexable inserts. This will prevent the cutting inserts from getting worn out due to the high level of abrasiveness exhibited by some composite materials. In addition, the pcd inserts used for milling should enhance the efficient removal of chips and provide excellent surface finish without any burrs.

Standard PCD Inserts for Milling Composites
In order to meet the peculiar challenges posed during composite material milling, it is better to use full surface inserts with or without chip breakers. The most commonly used pcd inserts for face milling of composites include the full face square and diamond shaped pcd diamond inserts. For example the SCGW/SCMW and the SEHN series have been tested on non-metallic and metallic composites include alloys of titanium and aluminum.

The grades of these tools, designed with a wiper flat length ranging from 1.6 mm to 8 mm, provide good surface finish. The nose/corner angle at the cutting edge is 90 degrees for the square shaped insert while the diamond shaped inserts are offered in various angles including 80 and 55 degrees. For higher accuracy, the micro structure of the grains of the pcd inserts can be altered to suit the nature of the material to be machined. For instance, the 10 – 20 μm grade is suitable for milling aluminum with high silicon as well as fiberglass, and CFRP. But copper and hard rubber will have a better surface finish with the 20 – 50 μm grade.

Conclusion
Using full faced polycrystalline diamond inserts for composite material milling will help to overcome many of the challenges posed by these non-metallic components. Before you make a final choice of tool insert, do some preliminary research to discover the characteristics of the work material and how it will behave under various cutting speeds and feed rates.

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