Introduction
Gear cutting is a machining process used to shape and accurately size metal gears. This process has evolved significantly over time from simple manual procedure to highly specialised automated processes. Dry cutting, such as dry hobbing or dry shaping, has become a popular method for gear cutting. This process is known for its many benefits, including improved accuracy and efficiency, reduced tool wear and better surface finish. This article will provide an overview of dry cutting for gear cutting, including its principle, benefits and applications.
Principle of Dry Cutting
Dry cutting uses a single-point cutting tool that is traversed around the gear blank’s outer diameter, its pitch diameter or both in a coordinated program sequence. During dry cutting, a lubricant is not applied to the cutting tool, resulting in improved surface finish and increased tool life. The tool may run at a low rpm speed as the cutting force is relatively low due to the lack of lubrication. In some cases, high spindle speeds can be used, depending on the hardness and toughness of the material.
The cutting forces are transferred to the part being machined, not to the cutting tool, resulting in higher part accuracy and a better surface finish. In addition, the cutting forces are dispersed over a larger area resulting in less wear to the cutting tool. It may be necessary to reduce feed rate when machining difficult materials in order to reduce edge build-up and chip packing.
Benefits of Dry Cutting
The benefits of dry cutting for gear cutting include improved accuracy and better surface finish. The accuracy of the gear blank is improved due to the minimized cutting forces being transferred to the blank - as opposed to wet cutting, where cutting forces must be distributed to both the workpiece and the cutting tool. This results in less cutting force on the part and more repeatable results. The lack of lubrication results in less edge build-up, which can cause inaccuracies in parts with complex shapes.
Manufacturing processes such as dry hobbing and dry shaping also result in less tool wear due to the minimal cutting forces. This helps to reduce tool change-out time and increases overall tool life. In addition, dry cutting results in improved surface finish. This is mainly due to the lack of lubrication, which reduces wear on the cutting material.
Applications of Dry Cutting
The improved accuracy and superior surface finish of dry cutting make it a popular choice for many gear cutting applications, including dry hobbing and dry shaping. Dry hobbing is a machining method used to create spur and helical gears. The process involves a single-point cutting tool that is traversed around the gear blank’s outer diameter, its pitch diameter or both. This method produces exceptionally accurate gears with a superior surface finish.
Dry shaping is another cutting method used to produce gears, such as spur and helical gears, bevel gears and sprockets. This process uses a single-point cutting tool that is traversed around the gear blank, either in a straight line or helical pattern. Dry shaping can produce superior quality, accurate parts with smooth surface finishes and small tolerances. This method is often used for short-run or prototyping applications, and can be used for small to medium size parts.
Conclusion
Dry cutting is a popular method for gear cutting due to its many benefits, including improved accuracy, less tool wear and superior surface finish. Dry hobbing and dry shaping are two popular dry cutting methods used to create spur and helical gears, bevel gears and sprockets. These methods produce highly accurate parts with superior surface finishes with minimal tool wear. Dry cutting is often used for small-run applications or prototyping and is suitable for a variety of materials.
