High Energy Applied Technology (H.E.A.T.) was developed to address the need for high-speed cutting of wire EDM applications where good, sealed flushing cannot be achieved, while at the same time providing high accuracy, unparalleled part straightness, and good surface finishes. The desire to be able to use the most common EDM wires in today’s market was also taken into consideration in the development of this new system.

When the flushing nozzles cannot seal off on the top and bottom surfaces of a workpiece, flushing pressure will be lost due to the de-ionized water stream losing pinpoint focus to the cut area, especially in taller work. This can result in a loss of pressure, less efficient removal of eroded material particles from the spark gap, and numerous wire breaks—causing the burn to be less efficient. These poor flushing conditions can come about from uneven workpiece surfaces, interrupted cut paths, spaces between stacked parts, or workholding devices that make it impossible for the nozzles to be close enough to the work surface to seal properly. H.E.A.T. addresses these less than perfect conditions, and allows highly efficient wire EDM’ing of parts without sacrificing accuracy, straightness or surface finish.
On earlier machines, flushing pressure had to be developed and maintained by a good seal between the workpiece and nozzle face, much like putting your thumb over the end of a water hose. By restricting the opening at the end of the water hose, the water is forced through a smaller opening and pressure increases. Similarly, as a flushing nozzle seals on the work surface, water flow is restricted from escaping around the sides of the nozzle and is instead focused through the wire cut path and pressure increases. If a space occurs for any reason in the cut path, pressure will be lost, and burn efficiency will be reduced.

One design requirement of H.E.A.T. was to present a solution for these poor flushing conditions and find a way to maintain flushing pressure without being able to seal the nozzles on the work surface. In other words, pressure needed to be forced through the flushing system, instead of being developed by sealing off the flush nozzles.

The solution to these requirements was to increase the flow from the twin flushing pumps and then restricting that flow with a smaller nozzle opening. To make this happen, the pump parameter software that controls the frequency or output of the flushing pumps was modified to allow a higher volume of water to reach the nozzles. The smaller nozzle opening restricts this increased flow, increases the pressure of the water coming from the pumps, and directs a smaller, higher pressure water jet into the gap to remove debris more efficiently.

This solved one problem, but caused another. With a higher volume of water being forced through the flushing system in a shorter amount of time, it would now be possible for the level of the water reservoir to drop so low that flushing would become erratic and eventually stop. This would cause a very slow and unstable burn, would eventually cause the machine to alarm out, and if the pumps continued to run with no water flowing through them they could be damaged by running “dry”.

A solution had to be developed that did not require increasing the size of the water supply tank. This was resolved by modifications to the plumbing of the flushing system that allow the pumps to operate at the higher flow rates and maintain higher pressure without depleting the water supply.

Adjustments also were made to existing technology libraries in the machine’s software set to make the cutting conditions more aggressive, thus allowing H.E.A.T. to take full advantage of the two pump system.

Along with more aggressive cutting parameters within the software, already proven control and monitoring software—with unmatched part straightness, excellent geometry control and superior wire break prevention/machining speed and flushing controls optimization—were also incorporated in the technology. All of this contributes to H.E.A.T. being able to maintain accuracy, straightness and surface finish in high speed, non-sealed conditions.

Control and Monitoring Software
Outstanding part straightness is achieved via the use of active software control to compensate for changes in the wire caused by erosion and wire lag to reduce or eliminate belly, bow or taper in a part during the initial rough cut. By producing a straighter part during the roughing pass, fewer skim passes are needed, and are used to achieve a better finish, instead of correcting for error (belly or bow) left by the roughing pass.

Excellent geometry control is obtained by technology that automatically adjusts servo speed during the rough and skim passes in order to optimize material removal in corner geometry. This improves corner geometry accuracy by compensating for wire deflection going into and out of corners, and maintains consistent material removal during finishing passes.

Superior wire break prevention/machining speed and flushing controls optimization improves machining performance and efficiency by delivering consistent spark pulses to the cut. This technology monitors and adjusts machining current according to changes in flushing pressure and workpiece material thickness, which produces a more stable machining condition—providing more consistent cutting speed, surface finish and accuracy. In workpieces with sudden changes of thickness, this technology also helps reduce wire breaks at these transition points.