Electrical Discharge Machining
EDM represents the thermal erosion process that removes metal by a series of recurring electrical discharges between a cutting tool acting as an electrode and a conductive workpiece, in the presence of a dielectric fluid. In the gap between the electrode and the workpiece occurs a voltage discharge and parts from the workpiece vaporize from the heat of the discharge, this particles ar washed from the gap by the dielectric fluid that flushes continuously. High-Speed EDM Drilling is used to produce very small and accurate parts as well as large items.
Invest in High-Speed EDM Drilling for:
What was once almost impossible to drill by conventional machine tools it is now easily performed with High-speed EDM hole drilling that was designed especially for accurate small and fast deep-hole drilling.
Due to the continuously expanding technology, this kind of EDM machines have the capability to drill to any conductive material and because of this technology using a High-Speed EDM Drilling Machine has removed two major problems:
- using this technology specifically for start holes in wire EDM jobs
- having to locate, program and drill the holes by conventional machines methods in the “soft” workpiece prior to heat treat and by heat treat the workpiece before drilling, all the stresses are being removed prior to the drilling process.
High-speed EDM hole drilling applications began to expand and burn tests were done not just in hardened tool steel; tungsten carbide, aluminium, stainless, titanium, brass and inconel but also expanded to mould and part manufacturing-injection nozzles, oil drain holes, hydraulic cylinders and dowel pins, as well as turbine blades, ball bearings and safety wire holes in hex nuts, etc.
To understand better the High-Speed EDM Drilling the process consists of using a precision tubular electrode, generally brass or copper, that is mounted into the drill chuck that is located on the “Z” axis and held in location on top of the workpiece by the ceramic guide.
After the drilling depth is set and the workpiece is located the electrode rotation is turned on and the pressurized deionized water solution is sent through the tubular electrode as a flushing agent. The power supply parameters normally consist of on-time, off-time, peak current and amount of capacitance.
At the end of the drilling cycle, the discharge is turned off and the “Z” axis is retracted above the workpiece.
2. High-Speed EDM Drilling Times
To establish the drilling time we need to take into consideration the hole size and type of material.
For reference, you’ll see in the table a few samples of possible speeds.
The Novidrill from Novick can reach up to 30 – 60 mm/min, depending on the material.
〉 This method of drilling produces burr-free holes ⇒ which results in the elimination of secondary deburring processes.
The combination of spark duration and flushing efficiency are factors that determinate the amount of time the power is off. Since during off time no material is being removed it showld be kept at a minimum. The better the flushing conditions, the less off-time is required, and the efficiency of the entire operation is increased.
3. Super High-Pressure Pump
A very important function in any EDM operation is the process of flushing because it serves to remove the eroded debris from the spark gap region and also has the function to influence the outcome of the machining process.
Not having a good flushing will lead to too much debris in the discharge gap and cause arc and/or short circuit that makes the process unstable and ends up with a bullet noising.
Improper flushing can result in uneven and significant tool wear, and it also affects accuracy and surface finish.
Other than knowing the fundamentals of on-time/off-time and basic electrode material selection, the three most important things in High-Speed EDM Drilling are Flushing, Flushing, and Flushing.
The most common and preferred method of flushing si pressure flushing. It can be performed through the tool or through the workpiece.
In the image is showed the pressure flushing through the electrode.
Another advantage of this method of flushing is that the high flushing pressure through the center of the electrode tends to stiffen it, and also produces a centering effect upon the electrode.
Efficient flushing requires a balance between pressure and volume.
- for roughing operations, where there is a much larger gap, high volume, and low-pressure flushing is advised.
- for small arc gap operations, higher pressure is needed to ensure proper flow.
4. Use of Ordinary Tap Water as dielectric
Today we can talk about a new generation of High-Speed EDM Drilling Machines that uses distilled water/tap water as the flushing agent. This opens new possibilities and economically applications in drilling field.
- It helps in initiating discharge by serving as a conducting medium when ionised, and conveys the spark. It concentrates the energy to a very narrow region.
- Helps in quenching the spark, cooling the work, tool electrode and enables arcing to be prevented.
- It carries away the eroded metal along with it.
Water is used for wire-EDM and high-definition die-sinking EDM where is an advantage to have low-viscosity and carbon-free.
The main factors for water quality are:
- Filtration: Filters should have the finest mesh for the job. The advantage is that allows faster cutting due to the clean cutting conditions. That also means less secondary discharge. Having fine-mesh filters will ensure longer and more efficient life from the de-ionising resin.
- De-ionisation: As the ionisation level increases so does the number of ions, so this is important because it becomes easier for a spark to pass across the gap between the work-pice and the electrode and can lead to wire breakage.
As the ionisation falls the number of ions decreases and is harder for the sparks to cross the gap and the potential voltage rises to maintain the same current flow.
3. Temperature Control: A wire EDM machine will cut faster and produce more if the temperature is controlled.
Using water, metal removal will be much faster as a dielectric because it is a much better flushing medium. Water dielectric sink heat from the spark gap much better than oils that insulate and retain heat in the spark gap.
Water possesses a better gap penetration because is naturally thinner and spark gaps are so small and water does this faster and better than oil.
Cutting speeds in spark EDM operations can be increased up to five times using a water.
5. User-Friendly Control
Easy to learn operation where parameters are entered directly in the control panel and can be easily optimized.
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 quantity 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.
The digital technology has advanced the functionality to the point where you can now precisely control and manipulate the EDM spark. Such control allows you to reduce maintenance costs, optimize the process and extend electrode life.
High-Speed EDM Drilling has a system that can be operated by any person in the workshop, without any high-level programming skills. Simplicity is here the rule.
6. High-Speed EDM Drilling Results
High-Speed EDM Drilling keeps up with the increasing customer demands in hole quality and integrity.
If you need hole quality and precision, EDM is the better option. Also, EDM is less affected by material thickness or aspect ratio then laser drilling.
Using a High-Speed EDM Drilling machine you’ll have smaller, deeper and more precise holes produced as fast as possible. Now the same hole can be drilled faster and as twice as deep with only one electrode and little operator intervention.
This EDM is more efficient, has higher output, delivers speed, consistency, and precision. It consumes less energy and has less wear on electrodes allowing them to cut faster and more accurately by eliminating bullet nosing of their tips.
7. Economical Price
An example of such a high-speed drilling machine is Novidrill from Novick that is also at an economical price.
Novidrill promises to offer an evolutionary alternative to the conventional EDM drilling machines and to bring you one step closer to the latest EDM technology.
- Travel(X/Y/Z) – 300×400×350 mm
- Diameter of electrode – Φ0.3-Φ3 mm
- Standard configuration – 380V / 50 Hz
- Size of worktable – 400 x 600 mm
- Travel Z – 350 mm
- Max machining current – 30 A
- Travel W – 300 mm
- Travel of Working Table – 300 x 400 mm
- Working liquid – Water
- Digital display – Three axes digital
- Distance director to Work Table – 100 – 400 mm
In need of producing Smaller, Deeper, More Precise Holes?
- 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 to-day’s applications, it’s important to look for a system that can drill a 15-mm deep hole as small as 0,20 mm in diameter in hardened steel and at the same moment to be able to drill a cooling hole of 2,5 mm in diameter 250-mm deep in mould steel, and this with minute variations in size and straightness from its entrance to exit.
- Most experts recommend selecting an EDM hole 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 quantity 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 be operated by any person in the workshop, without any high-level programming skills. Simplicity is here the rule.
- High-quality surface finish capability is a must. A growing amount of shops now use EDM drilling machines for generating finished holes that will not require any secondary finishing operations.
- Keep in mind that uneven wear increases a drilling electrode’s tendency to “walk” off center, resulting in crooked and angled holes instead of straight ones. Because they help reduce wear, Supper high-pressure coolant/flushing system 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 200mm deep hole drilled with a 1 mm electrode on a digital generator-equipped EDM system will vary in size from top to bottom, usually less than 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 only with a super high-pressure coolant/flushing system with sufficient debit to take the heat immediately away from the working zone.