Overcoming material challenges: Design & Engineering

Diamond-Plus, Walter’s tool erosion software, enables an optimal erosion process independent of disturbances, such as differences in material, electrode shape or tool profile, according to the company. Image courtesy United Grinding North America.

Companies that make cylindrical cutting tools from PCD and other materials face two key challenges: meeting the surging demand for PCD tools while retaining the ability to produce HSS, carbide, ceramic and cermet tools.

Being superhard, PCD cutting tools provide long tool life when machining abrasive, gummy materials, such as composites and aluminum alloys. The use of PCD tools is expanding as aerospace manufacturers seek to improve fuel economy by increasing the proportion of lightweight composite and aluminum parts in new aircraft.

Also in pursuit of lighter, more fuel-efficient vehicles, the automotive industry is machining more composite and aluminum workpieces. The extended tool life and clean cutting action provided by PCD tools for these materials outweigh their higher costs.

Toolmakers are producing PCD tools with complex cutting edge geometries to efficiently cut these advanced workpiece materials. However, creating those geometries in PCD is the real challenge.

Grinding PCD with diamond wheels presents the conundrum of grinding diamond with diamond, and it requires careful management of cutting parameters and close attention to wheel wear. An alternative to grinding is the noncontact EDM process. Wire and sinker EDMs can erode PCD, but there are restrictions on the tool features either can produce.

A wire EDM can produce the OD geometry of a PCD tool, for example, but forming some geometric details may not be possible because of the continuous nature of the wire. Similarly, the ability of a sinker EDM to follow a helical contour is limited. Both types of EDMs tend to be dedicated equipment without any grinding capabilities.

To grind the full array of tool materials, Walter developed the Helitronic Diamond Evolution grinding and erosion machine. This two-in-one machine grinds features of rotationally symmetrical carbide, HSS, cermet and ceramic tools while being able to erode PCD and PCBN tools with a rotary-disc EDM electrode.