EDM operators may feel a bit of envy when they compare the high throughput rates and precision of small units to their large sinker machines. Most EDM sinkers designed for big parts are slower than smaller models and may not achieve the same degree of precision when it comes to machining ribs and similar features in workpieces.
These differences may become things of the past. Makino has added a high-speed Z-axis head for use on its EDNC Series of large-part sinker machines that reportedly provides speed, high precision and automatic adjustment of power settings to assure clean, even burns on features such as ribs, as well as improved surface finishing.
The unit incorporates the company's new HS-Rib high-speed Z-axis technology, which Brian Pfluger, EDM product manager for the Mason, Ohio, manufacturer, says provides "sports car performance in a tractor-trailer package."
What he means by this is that the Z-axis unit accommodates the size and weight of large workpieces and machines them rapidly, with minimal electrode wear depending on the process setting.
The unit has a jump speed of 20 m (65.6 ft)/min and Z-axis acceleration of 1.5 g. The jump speed is four times greater and the acceleration rate 30 times faster than with previous technologies, Pfluger says. As a result the jump speed and acceleration generate sufficient hydraulic force during processing to clean debris from the spark gap, even in parts with deep ribs or similar features.
The Z-axis unit operates with Makino's SuperSpark IV, an adaptive power control with new settings that optimize sinker EDMs for automation. Pfluger says that once cutting parameters for ribs, seal slots or other workpiece features are programmed, the control automatically calculates cutting depth during machining and continually adjusts power settings to maintain an exact burn. This frees an operator from making such calculations, he notes, and facilitates automation.
The SuperSpark technology, available since 2001, has been upgraded in recent years. The current iteration is said to reduce roughing times in deep-rib applications by as much as 30 percent. The control also achieves shortened jump heights, which reduces by 50 percent the amount of time an electrode spends out of the cut.
The types of applications that Makino envisions for the Z-axis unit include large automotive parts, injection molds, consumer products and aerospace components, especially for engines.
"Customers always want faster speeds while maintaining quality," Pfluger says in explaining why Makino is adding the technology. "Our customers want their big sinker machines to work as well as the little machines."
The Z-axis unit features direct-drive motor technology and liquid cooling for thermal stability and precise depth control. It supports electrodes weighing up to 100 kg (220 lb). Z-axis strokes range from 500 to 800mm (19.6 to 31.5 in) and can be programmed with menu-driven 2D and 3D orbital machining patterns with no amperage limitations, Makino says.
According to Makino, four settings are available for machining with the Z-axis unit:
(Photo credit: Makino)Makino's new HS-Rib high-speed Z-axis technology is available on the company's EDNC Series sinker machines for large parts.
The EDNC Series of sinker EDM models, meanwhile, has such features as automatic tool change, adaptive controls for unattended operation and automatic jump-machining controls for efficient debris removal without external flushing.
Makino describes the EDNC Series machines as compact - the dielectric reservoir is in the base casting, which reduces floor space. They also offer ergonomic access for setup and operation, and have automatic fire-suppression systems. Programming is by menu-driven touchscreen or an MPG conversational format system.
The EDNC Series sinker machines can also be equipped with Makino's High-Quality Surface Finish (HQSF) technology that reportedly produces results that are 50 percent better than with conventional techniques. HQSF can also produce double-digit savings in cycle time, the company maintains.
- Low wear, which provides a single-electrode rough-and-finish process;
- Advanced orbit and jump settings, for improved machining speed and consistent surface finish;
- High-speed Z-axis operation, for improvements in speed and accuracy;
- Aggressive power settings, which provide optimum machining speed, though with much higher electrode wear.