While much has changed in die sinking technology, one of the foremost advancements is the development and continual improvement of adaptive control, or fuzzy logic, to eliminate the guesswork and allow the machine to take control of the metal erosion process.
Historically, the EDM operator was required to be diligent in monitoring the EDM application and have the necessary skills to correct any complications in the EDM cut. These talents are hard to find in the current labor market and come at a high price. This facilitates the need for improved capabilities in EDM CNC control. With the caliber of adaptive control in today’s EDM sinker, the machine continuously monitors the EDM gap in search for signs of impending failure. Once identified, the sinker automatically adjusts the machining conditions to overcome the threat; therefore, allowing the operator to focus on other tasks.
Unfortunately, this often results in complacency of the operator while believing the adaptive control of an EDM sinker will also provide the most efficient means possible to complete an application.
With this, a common occurrence is to use a more economical, lesser quality electrode material. After all, the sinker has the ability to overcome any complication in the cut and will be able to complete the task at hand, right? While this may be true in some cases, the fact is that the electrode material will affect the machine’s ability to fully optimize the EDM process and provide the most cost-effective means of completing the application. In other words, the adaptive control of the EDM sinker will optimize the application only to the level of what it has to work with.
The purpose of the adaptive control in an EDM sinker is to read the conditions of the EDM spark and translate these conditions into digital signals that are fed into the machine’s controller. The controller translates these signals, determines the efficiency of the EDM cut and makes adjustments accordingly. One of the conditions monitored by the machine’s adaptive control technology is contamination in the gap. If excess contamination in the gap is present, this creates the potential for an EDM arc or diminished performance. The controller must then make adjustments that do not affect the overburn or surface integrity of the workpiece. This generally involves changes in the gap voltage, increasing the off-time, altering the jump cycle or a combination of any of these.
While this may rectify the issue, the problem is that none of these are conducive to truly optimizing the EDM performance. Using lesser quality electrode materials often creates the need for the machine’s controller to make continual adjustments; therefore, slowing down the EDM cut.
The old adage, “If it ain’t burning, it ain’t earning” comes to play here. For example, as the controller increases the off-time in an EDM cut to overcome excessive contamination in the gap, the corresponding duty cycle of the electrode material is reduced and the EDM cut is slowed.