Thin Flushless Ribs
To make deep pockets and flushless rib cuts possible you need pulsing functionality. However, a pulser alone will not always make those cuts easy but the ability to pulse rapidly is the key to success. When the ram retracts away from the part it creates a vacuum. That vacuum pressure sucks flush down into the cut to wash debris away. Conversely, when the electrode is pushed back into the cut it displaces that flush causing it to exit the cut, carrying away the debris.
The more rapidly the ram can retract and advance, the more effective it is at flushing debris out of the cut and reducing arcing. It would not be uncommon for a hydraulic cylinder on an older EDM machine to achieve speeds of only 10 to 20 inches per minute (typically the larger the weight capacity of the machine the slower they move). In contrast there are modern servo driven actuators that can move at speeds of 300 or more inches per second.
If you do not want to invest in an electric servo motor conversion upgrade there are a few things you can do to help you achieve success. Make sure your EDM oil is as clean as possible at all times, keep your electrode and fixturing weigh as light as possible, adjust the pulser settings to determine the optimum retract speed, duration and distance for the job and you may need to lower your anti-arc sensitivity if your power supply has anti-arc protection circuitry.
For older EDM’s such as the Elox, the EDM Zap Ram Pulser is an electronic timer that improves cutting conditions in the EDM gap.