JEC COMPOSITES MAGAZINE - Issue #77 - December 2012 - 51

tools

PCD vein technology facilitates composite machining
Everyone knows that to machine composite materials, you have to pay a lot of attention to the material and method used for each operation. This is why finding specific machining solutions represents such progress. Sandvik Coromant and Precorp offer tooling solutions that give higher performance and quality for power feed machines and CNC machine tools, whether you are working with CFRP materials or with CFRP/metal laminates (e.g. CFRP/aluminium and/or titanium).

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A strategic position

ne of the most remarkable recent innovations for drilling composites is the PCD (polycrystalline diamond) vein technology. To understand the concept, you first have to understand conventional PCD and its limits. PCD is usually produced in the form of discs with a carbide substrate. The tools are made by taking segments of the PCD discs and brazing them onto the tool bodies. This concept has two major drawbacks: one, the tool geometry is limited to what can be achieved using flat segments; and two, the brazing of the PCD segment onto the tool is done close to the cutting edge, so the heat produced later during the machining process can create a risk for the joint if the temperature approaches the braze melt point.

To avoid these drawbacks and obtain all the advantages of PCD properties, Sandvik Coromant and Precorp focused on producing PCD tool blanks provided with strategically placed veins of PCD. This type of blank is fabricated by compressing diamond powder into grooves on the carbide tool body and then sintering at high temperature and pressure. The PCD-veined blank is then brazed on a tool holder, and the PCD veins are exposed to create the tool’s cutting edges. The appeal for machining is that the PCD veins can be created in all types of configuration as a function of the desired cutting edge. It is also possible to create helical cutting edges and edges with complex geometries that are not obtainable with brazed PCD segments. The company can provide optimum cutting geometries that are specifically adapted for the machining conditions or for high-volume applications where high precision is required. With PCD vein technology, there is no problem with ruptured joints between

PCD segments and tool body. Of course, veined tools also have a brazed joint, but it is placed well away from the cutting edges and out of range of the heat from machining.

Special geometry
PCD-veined tools offer cutting geometries with sharp edges that stay sharp even in the most abrasive composite materials. With this technology, you can also obtain improvements such as angle reinforcements, to allow higher cutting speeds without sacrificing the surface quality or sizing tolerances. For composite laminates that include metal layers, high-strain areas on PCD-veined tools can be micro-ground in strategic places to protect edge sharpness and increase the service life. The edges cut the fibres in composite materials at low shear force, reducing the risk of delamination, overheating – or even melting – of the matrix, fibre tearing, or surface chipping.

A key operation
Drilling is the most common machining operation used on composite materials. To take one example, in the aerospace industry, joining preparation for composite structural aircraft parts takes a significant

CoroDrill859V offers an optimised geometry

No77 December 2012

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JEC COMPOSITES MAGAZINE - Issue #77 - December 2012

Table of Contents for the Digital Edition of JEC COMPOSITES MAGAZINE - Issue #77 - December 2012