The concept of gears has been around for many decades, they are one of the oldest machineries in human history. The primary purpose of the gears is to transmit power with minimal wastage of energy and work. So, they must be designed and manufactured to withstand high residual stress and have minimal tolerance in geometry. The high precision machining of gear parts enables the engineers to create intricate geometries with high precision and accuracy with minimal fatigue and stress points.
This article will delve into the basics of gear high-precision machining through EDM techniques, by explaining their manufacturing process and the benefits that high precision machining services bring in comparison to traditional machining.
Wire EDM for Gear Tooth Profiles
Wire EDM is a highly precise machining process, its typical tolerance ranges from ±0.005 mm to ±0.025 mm accuracy. For this reason, it is used for highly complex geometries like gear tooth profiles for aerospace structures. The manufacturing process of gears through Wire EDM depends upon a thin wire electrode, CNC machinery, and relevant dielectric fluid path. The wire EDM electrode is made from brass or copper, and it is precisely guided by the CNC program as per the desired profile of the gear tooth.
For the high precision machining of gear parts, the engineers are required to code the desired shape of the product as per the 3-D dimensions from the drawings. The workpiece used in wire EDM is typically a metal or its relevant alloys which have conductive properties. As the name suggests electric discharge machining, is electric conductive machining. So, it is compulsory to build a strong electric connection between the electrode and the workpiece. For that purpose, dielectric fluid is used. The dielectric fluid acts as a medium through which electric discharges occur. This fluid also helps to flush away debris and make a consistent gap between the electrode and the workpiece. Otherwise, the workpiece may get damaged.
As the wire electrode reaches the workpiece, electric discharge sparks start generating. This spark vaporizes the material and starts making the desired shape of the gear. Wire EDM gives excellent results when you are dealing with sharp corners and surface finishing operations.
Sinker EDM for Internal Gear Cavities
Sinker EDM machining processes are commonly used when we have to deal with Complex internal cavities and curves in gear manufacturing. This EDM high precision machining technique is commonly used in the aerospace, automobile, and medical industries. The working process of sinker EDM is quite similar to the Wire EDM technique, however, it is more favorable with respect to a tight tolerance. The electrode used in sinker EDM is mostly made up of graphite and copper material.
In this technique, before the manufacturing process, the work is dipped into the dielectric fluid bath such as oil or deionized water. So that the conductive properties of the workpiece are enhanced. The electric discharge from the electrode produces heat and raises that temperature at the point of contact. The temperature rises up to 8000 to 12000 degrees Celsius (14432 to 21632 degrees Fahrenheit). That much temperature at a specific point precisely melts the material and vaporizes it with up to a millimeter of accuracy.
For the manufacturing of cavities, this process is repeatedly performed several times to get the desired shapes. One of the main advantages of EDM at this stage is that it avoids any unnecessary internal stresses in the gear structures. This will enhance the durability and structural integrity of the gears.
EDM Drilling for Gear Holes and Shafts
EDM drilling, which is also known as hole-popping technology, is used to build precise holes in gears and shafts. EDM drilling is a contactless drilling process, that relies on electrode and dielectric fluid which act as a second electrode in this case. The importance of EDM drilling manufacturing is evident from creating cooling holes in turbine blades. These holes have highly precise dais and they are used for regulating temperature during engine operations. Traditional drilling processes are not favorable in this case, as they are not able to drill the required depths for those.
For manufacturing of these colling holes, a conductive electrode which is mostly made from brass or copper is set to be rotated at high speed near the workpiece. When the gap between the electrode and the workpiece is small up to 0.005 mm to 0.1 mm. The electric discharge is generated, which erodes away the material, and the hole is created. The shape of the hole gradually aligns with the shape of the electrode, and the material is removed in a layer-by-layer structure. The EDM drill is able to create holes with aspect ratios (depth-to-diameter ratios) exceeding 100:1. This ratio makes it ideal for turbine and engine components drilling.
Multi-Axis EDM for Complex Gear Forms
Gears having complex geometries, such as asymmetric tooth profiles, helical gears, or irregular shapes are very difficult to machine through traditional machining processes. To manufacture these custom decisions multi-axis EDM machines, are preferable. With the help of Multi-axis EDM machinery, engineers can easily machine internal splines, pockets, and grooves with tight tolerance. These features are vital for automotive industries, where smooth gear engagement and efficient power transmission are the main focus.
For instance, for helical gear which has an asymmetric tooth profile traditional machining practices are difficult to implement. However, with the multi-axis EDM machines machinists are able to design and manufacture the tooth of the gear precisely. Multi-axis EDM machines give liberty and more precise control of the electrode movement. An electrode is able to tilt, rotate, and do axial movements, which facilitates intricate geometries.
Conclusion
Advanced EDM processes provide precise and efficient ways to manufacture gears with complicated geometries and tight tolerances. Especially for curves and grooves in the gear structures, the precision offered by EDM machines is unmatchable. Moreover, EDM machining does not cause or increase any unnecessary residual stresses in the final product, which increases the durability and life span of the gears even under extreme load conditions. As modern EDM technologies are dependent upon CNC coding, expert engineers and CNC machinists are a must to gain the desirable results.
