Drill EDM Guide

About EDM Drilling

EDM Drilling is a technology used for fast, accurate drilling of small and deep holes. Small holes that once were almost impossible to drill with conventional machine tools are now made easy with an EDM hole drilling machine. Thanks to the possibility of drilling virtually any conductive material, the use of this technology is constantly evolving.

Initially, workshops used this technology specifically to drill holes in electrical discharge work. Heat-treated materials are shipped before drilling the initial hole. This eliminated two problems:

(1) The need to program, locate and drill the initial hole by conventional machine methods in a soft object before heat treatment.

(2) Sending the object for heat treatment before drilling the initial hole. All stresses were removed from the workpiece before using the EDM process. 

As this process became more known, trial burns were carried out in more than just hardened tool steel; tungsten carbide, aluminum, brass, and Inconel were all tested. Rapid drilling of holes in EDM began to expand into injection nozzles for the production of molds and parts, oil drain holes, hydraulic cylinders, and locating pins, as well as turbine blades, ball bearings, and protective wire holes in the hex nuts.

Figure 1. EDM Hole Drilling Machine, Exetek

EDM Machines Explained

An erosion drilling machine involves creating a spark between the workpiece and the electrode tube when it starts drilling into it. The spark from the drill produces an intense amount of heat and jumps through the gap between them and erodes the workpiece. This device is specially designed for drilling hard materials such as hardened tool steel or alloys, tungsten carbide. The size of the holes is usually from 0.012 (0.3 mm) to 0.118 (3.0 mm). The smallest holes cannot be made with a traditional drill bit.
 

EDM Drilling Process

This process involves using a precision tubular electrode (usually brass or copper) mounted in a drill chuck, which is located on the Zaxis and held in place at the top of the workpiece with a ceramic guide. The upper part of the workpiece is placed and the drilling depth is set. The rotation of the electrode is switched on and the deionized water solution, which is usually under a pressure between 50 and 100 kg / cm2, is sent through a tubular electrode as a rinsing agent. 

The power supply parameters are also set, which usually consist of on-time, off-time, peak current, and capacity. At this point, the discharge is activated to start the drilling cycle. At the end of the drilling cycle, the discharge is switched off and the Zaxis is retracted over the workpiece. Check out the video below to see how quickly you can drill a hole using EDM technology:
 

Drilling Time Explained

Drilling time depends on the hole size and material type. But EDM technology can achieve even faster drilling time than conventional drills. This explains why rapid drilling of EDM holes has become an alternative to conventional machining in mold making. 

In addition, this drilling method produces burr-free holes, which eliminates secondary deburring processes. Larger power supplies and drill chucks/collets have expanded the diameter range of standard drill hole sizes to 0.010 "to 0.36". Drilling EDM holes can now be done on a manual machine, ZNC, or CNC machine.
 

Applications of EDM Drilling

Currently, many EDM methods use distilled water as a rinse agent, which opens new possibilities for the medical industry. Thanks to the continuous improvement of EDM technology, more and more applications are appearing on the horizon – it has become a completely new method of producing molds and parts.

Small hole EDM drilling is ideal for creating injection nozzles in molds and coolant holes in tooling, as well as initial holes for wire EDM operations. Because both are EDM processes, it is often more economical to apply this combination to hardened materials. A Sinker EDM is also hypothetically capable of producing small holes, but it would be more expensive and is usually 10 times slower than a small hole EDM

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