EDM Cutting of Carbide, PCD, and CBN

July 6, 2010

Makino has released the UPV-3 and UPV-5 wire EDMs designed with an oil-based dielectric fluid system for high-accuracy machining of hardened materials and mirrorlike surface finishing capabilities.

The thermal control system maintains constant dielectric and casting temperatures, and the company’s latest SPG II circuit improves finishing operations. Together these features create a rigid, reliable, high-accuracy machining platform capable of producing surface finishes to 0.08 µm Rz, the company states.

These machines feature a fixed table design in which axis movements are controlled by machining heads.

Included in the design are ceramic insulators placed between the worktable and machine casting to reduce stray electric capacitance and enable the SPG II machining circuit to stabilize microelectrical discharges. Utilizing these capabilities under standard machining conditions for a 0.79-in.-thick workpiece measuring up to 3.93 by 3.93 in., users can achieve 0.2-µm Rz surface finishes.

The table’s electrically conductive machining area also can be limited for jobs requiring a surface finish better than 0.2 µm Rz. This further reduces stray electric capacitance for surface finishes down to 0.08 µm Rz (actual measured value).

In similar performance tests using carbide, these machines performed up to 22 percent faster than water-based machines, and up to 78 percent faster than prior oil-based technology with good sealed flushing, the company states.

The machines’ oil-based dielectric fluid systems create a smaller spark gap between the electrode and workpiece than standard water-based fluid systems. This facilitates precision machining of narrower slot widths and smaller corner radii in a variety of materials, including hardened metals and polycrystalline diamond (PCD).

Using oil-based dielectric fluid also eliminates the soft layer that can result from the EDM process and surface corrosion caused by electrolytic action. According to Makino, in long-run applications in which machined parts remain submerged for extended periods, this can be critical in controlling corrosion or oxidation layers susceptible to these effects.

For more information, visit www.makino.com.