Gears may be one of the earliest materials used by humans. They are present in almost all modern machinery. To withstand harsh operating environments, gears must be well-built, reliable, efficient and durable. Gears must reduce stress and strain to avoid failure, which can lead to conditions. To meet all these demands, gear manufacturing has developed into a highly specialized industry.
Depending on the parameters, different materials can be used to manufacture the gears. While non-ferrous materials such as plastics and composites are used in some applications, steel is the most commonly used material in other applications.
Gears are usually made from steel (the most common material) and a variety of non-ferrous materials including plastics and composites. According to the design requirements, the gear material should have the following properties: high tensile strength under static load, high lasting strength under dynamic load, low friction coefficient, and good manufacturability.
Gears can be manufactured using a variety of methods, including casting, forging, extrusion, powder metallurgy, and stamping. Among them, machining is the most commonly used production method.
Common machining operations include:
3. Rack planing
4. Cutting with disc cutter
Electrical Discharge Machining (EDM)
EDM is a manufacturing process that removes material from a workpiece by applying a series of electrical discharges between two electrodes separated by a dielectric bath.
EDM excels at cutting complex geometries of all sizes, but has its limitations. If you don't have good controls and programs, it's easy to damage part surfaces, especially for tooth profiles that are challenging to CNC program execution. But high-quality and intuitive 3D modeling and CAM software, such as Feature CAM, Autodesk Fusion, Master CAM, etc., can produce the smooth motion needed to cut the helical teeth.
In recent years, EDM machines have improved. Early EDM machines and the use of this process had limitations, but they have continued to evolve. This evolution maximizes the issue of surface finish, improved cutting accuracy and resulting material properties (microstructure, mechanical properties, etc.). The process can achieve tolerances accurate to one thousandth of an inch and produce pinions (less than a 2mm in diameter) and large gears (over 600mm in diameter). The process can be used both for precision applications in timepieces and for cutting stronger gears, such as those used in racing cars.
Rolling is one of the oldest forming processes. It hot-rolls or cold-rolls a blank workpiece through two or three dies to form the gears, as shown in the figure below.
How to save material is a key issue in the manufacturing process, and rolling is a good choice because no chips are generated. However, for an efficient process, you must consider rolling parameters, deformation and microstructural effects before increasing throughput.
Casting is a forming process used to manufacture gear blanks (which are then machined) and complete gears with cast tooth profiles. Tolerances and precision are key considerations when casting gears, and creating molds requires significant upfront costs. However, once the mold and process parameters are determined, mass production justifies the investment.
Sand casting is mainly used to produce gear blanks for other processes. Fully functional spur, worm, and bevel gears are cast from gears for washing machines, small appliances, hand tools, toys and cameras.
Powder metallurgy is a high-precision forming method and a cost-effective alternative to traditional machining of steel and cast iron gears. However, this method is not suitable for larger gear sizes, but is good at making small, high-quality spur, bevel and helical gears. Larger gears have lower fatigue and impact resistance due to the porosity of the molding material, although a sintering process can be used to improve their mechanical properties.
Powder metallurgy is also particularly useful when gear designs include holes, depressions, and different surface levels or protrusions. You'll find these gears in appliances, farm, lawn and garden equipment, cars, trucks and military vehicles.
Additive manufacturing, also known as 3D printing, builds three-dimensional objects layer by layer from a CAD 3D model. Due to the nature of the process, additive machines can form complex designs with lattice structures. These structures can be modeled to achieve lightweighting not easily attainable through traditional methods. Geometries of this type are often created using 3D topology optimization and computer design software.
Both conventional and non-circular gears can be manufactured through additive manufacturing processes, and high-quality 3D printers are relatively inexpensive and widely available. Because of this availability, it has become the choice for repairs and mechanical projects, such as educational toys or other gadgets that require full-featured gear. You can also include other features and even combine geometry with gear shapes to add custom shafts, keys or grooves into the same solid.