by Ken Baeszler
Produce smaller, deeper, more precise holes with EDM drilling
Demand for smaller, deeper and more precise holes produced as fast and as consistently as possible has created a need for more advanced, new electrical discharge machine (EDM) drilling technology in holemaking operations. Here are some tips on how to select the EDM drilling system that will help your shop achieve these holemaking goals.
Look for an EDM system that is fast, reliable and simple to operate. It should have enhanced drilling capabilities for extremely small hole sizes, but at the same time maintain good surface finish quality and accuracy at greater depths. Considering some of today’s applications, it’s important to have a system that can drill a hole, for instance, as small as 0.006 in. (0.150 mm) in diameter, 0.250 in. deep in hardened steel using a 0.004 in. (0.101 mm) diameter electrode. However, that same system should also be able to drill one 0.040 in. (1 mm) in diameter, 6 in. (152.4 mm) deep, and do so with minute variations in size and straightness from its entrance to exit.
Most experts recommend selecting an EDM drilling system that utilizes the latest in digital generator technology. Digital generator technology gives EDM drilling machines more precise spark control. It is this functionality that also helps reduce electrode wear. For optimal productivity, the goal is to generate as many holes as possible or drill as deep as required using the least amount of electrodes. Thus, the more a generator can help reduce electrode wear the better. Plus, less wear on electrodes allows them to cut faster and more accurately by eliminating the “bullet nosing” of their electrode tips.
Seek out an EDM drilling system that can function with little, if any, operator intervention. Because they incorporate more of the design qualities of sinker-EDM technology, today’s advanced EDM drilling systems are built for continuous unattended, lights-out operations.
High quality surface finish capability is a must. A growing amount of shops now use EDM drilling machines for generating finished holes–those that are actually part features–that will not require any secondary finishing operations.
Keep in mind that uneven wear increases a drilling electrode’s tendency to “walk” off centre, resulting in crooked and angled holes instead of straight ones. Because they help reduce wear, digital generators thus prevent such a scenario and contribute to producing straighter holes and ones that can be held closer to size from top to bottom. For instance, a 5.905 in. (150 mm) deep hole drilled with a 0.040 in. (1 mm) electrode on a digital generator-equipped EDM system will vary in size from top to bottom, usually only 0.001 in. (0.025 mm).
Find an EDM drilling system that provides control over heat-affected zones for generating surface finishes comparable to those typically attained using a wire-type EDM. Such surface finishes are possible on conventional hole-popper machines, but achieving them would require an extremely skilled operator and a considerable amount of time. With the latest digital generator-equipped drilling systems, however, the process is consistent, much quicker and accomplished automatically.
Today’s technically advanced EDM drilling systems essentially put holemaking accuracy in the technological hands of the machine tool. And while existing hole-popper systems are
quite capable of generating very small accurate holes with good surface quality, advanced EDM drilling systems dramatically increase a shop’s capability to consistently produce tiny holes that are even more accurate and with higher quality surface finishes. SMT
Ken Baeszler is product manager at GF Machining Solutions, Lincolnshire, IL.
