Japanese machine tool builder, Makino, has developed new technology for drilling cooling holes in nickel alloy engine blades and vanes more quickly and efficiently. It has resulted in the launch of the EDBV3 electric discharge machining (EDM) drilling machine, which is available in the UK through sole agent, NCMT.

The CNC machine provides aerospace manufacturers with the speed, flexibility and reliability to produce in a single set-up a wide range of hole sizes and shapes, significantly reducing the variety of tools needed and overall cycle times. The ability to machine holes of different shapes increases cooling efficiency, allowing jet engine combustion temperature to be raised to 1,500°C or more, boosting fuel efficiency.

By combining each pipe electrode, electrode holder and positioning guide in one assembly, Makino has eliminated the need to insert the electrode during automatic tool change, which takes 30 seconds. Automatic exchange allows holes of different diameter to be produced at freely programmable angles and positions during unattended operation.

The usual restrictions of multiple-electrode comb-machining are thus avoided. The standard machine configuration includes a 24-station tool carousel system which itself can be exchanged robotically for extended automated operation.

A rigid arm assembly holds, locates and supports the die guide. An integrated middle guide can be deployed for smaller diameter electrodes, preventing whipping, bending and vibration. The middle guide fingers automatically retract as the rotating, tubular electrode reduces in size, maximising electrode length usage. A length management system provides electrode wear tracking and automatically instigates tool change when it becomes too short.

The rotary C-axis head accepts electrode diameters down to 0.2 mm. The EDM drill rotates at 1,000 rpm and is designed to withstand internal pressures of up to 10 Mpa, ensuring effective flushing and high material removal rates. Drilling is performed fully submerged in a water-based dielectric for high part quality, improved stability and faster processing speeds than are possible using conventional technologies.

As a result of the submerged machining and newly developed generator technology, the EDBV3 can drill cooling holes seven times faster than pre-existing EDM drilling technology, according to Makino. Despite such a high machining speed, the heat-affected zone in the workpieces is within permitted tolerance limits for aircraft engine construction.

Makino's proven EDM drilling software is integrated into the control, providing user-friendly input screens with direct G- and M-code programming formats. To prevent back-wall impingement when penetrating cavity-wall blades and vanes, the EDBV3 includes sensitive breakthrough detection using a combination of adaptive process monitoring techniques that is effective even when machining parameters are set to maximum.

The EDBV3 has X-, Y- and Z-axis travels of 370 mm, 270 mm and 500mm respectively, and the 2-axis, 250 mm x 270mm table supports a maximum workpiece load of 5kg (optionally 15kg). The high-precision EDM sinking technology can also be employed in other industrial applications, such as the manufacture of medical parts, fuel injector nozzles, filters and die plates.