Gear Manufacturing: A guide to the gear production process

Gear manufacturing is a precise and critical mechanical manufacturing process that plays a crucial role in the performance and reliability of mechanical transmission systems.

Common gear manufacturing methods include:

Cutting processing: such as hobbing, gear shaper, shaving, etc.

• Hobbing is to cut tooth shape by relative rolling between hob and gear blank, which is widely used in mass production of cylindrical gear.
• Gear shaper is suitable for machining internal gears and multiple gears.

Forging: Used to manufacture large gears or gears with high strength requirements.

• Examples include the manufacture of large gears in heavy machinery.

Casting: Suitable for gears with complex shape, large batch and not particularly high precision requirements.

In the gear manufacturing process, the following aspects need to be strictly controlled:

1. Dimensional accuracy: Ensure that the module of the gear, the number of teeth, the diameter of the tooth tip circle, the diameter of the root circle and other dimensions meet the design requirements.
2. Profile accuracy: including profile shape and direction accuracy to ensure good transmission performance and low noise operation.
3. Surface quality: Smooth surfaces help reduce wear and improve fatigue life.

The quality of gear manufacturing directly affects the transmission efficiency, stability and life of the mechanical system. For example, in automotive transmissions, high-precision gears enable smooth shifting and lower energy consumption; In industrial retarders, high-quality gears can ensure long-term stable operation and reduce maintenance costs.

Gear manufacturing process mainly includes the following:

Gear hobbing

This is a commonly used gear machining method. The hob on the gear hobbing machine rotates relative to the gear blank according to a certain transmission ratio, and the hob gradually cuts out the tooth shape during the rotation process. Gear hobbing has high production efficiency and accuracy, which is suitable for mass production of gears with medium modulus and precision requirements.

Advantages:

• High production efficiency, suitable for large-scale production.
• High precision gear can be processed.

Example: Gearbox gears in the automotive industry are often hobbing.

Gear shaping

The gear shaper moves up and down reciprocating, and makes a circular motion relative to the gear blank to gradually cut out the tooth shape. Gear shaper is suitable for machining internal gears, multiple gears and sector gears.

Advantages:

• High precision gears can be machined.
• For some special shape gear has a better processing effect.

Example: The gear shaper process is used in some precision gears in the aerospace field.

Shaving processing

The gear shaving cutter engages with the gear without side backlash. By the relative slip between the gear shaving cutter and the gear, the trace metal on the tooth surface is shaved, thus improving the precision and surface quality of the gear.

Advantages:

• It can effectively correct the tooth shape and tooth direction error of the gear.
• Improve the gear surface finish.

Example: Transmission gears in high-precision machine tools may undergo a shaving process.

Gear honing

Gear honing is similar to shaving, using the free meshing of the honing wheel and the gear to be machined to finish the gear, mainly used to improve the surface roughness of the gear.

Advantages:

• Further improve gear surface quality.

Grinding processing

Grinding wheel is used to grind the tooth surface of the gear to obtain a high precision and high surface quality tooth profile.

Advantages:

• A high level of accuracy can be achieved.

Example: Gears in precision instruments usually require grinding.

Die casting and injection molding

For plastic gears or some small metal gears with low precision requirements, die casting or injection molding can be used.

Advantages:

• High production efficiency and relatively low cost.

Example: Plastic gears in some small household appliances are often injection molded.

Different gear manufacturing processes have their own characteristics and scope of application, in actual production, it is necessary to choose the appropriate process according to the use of gear, precision requirements, batch size and other factors.

Common gear types are as follows:

Cylindrical gear

1. Straight cylindrical gear: the tooth line is parallel to the axis, the transmission direction of the force is unchanged, the transmission smoothness is general, and it is suitable for the transmission with low speed and small load.

• Application: General mechanical transmission, such as machine tool transmission mechanism.

2. Helical cylindrical gear: the tooth line is inclined to a certain Angle relative to the axis, smooth transmission, strong bearing capacity, suitable for high-speed and heavy-duty transmission.

• Application: automobile transmission, industrial reducer.

Bevel gear

1. Straight bevel gear: used for transmission between intersecting axes, transmission efficiency is higher, but the noise is larger.

• Application: Automotive rear axle differential.

2. Curvilinear bevel gear: smooth transmission, low noise, high bearing capacity.

• Application: Transmission systems for heavy machinery.

Worm gear

• Features: large transmission ratio, compact structure, but the transmission efficiency is low, with self-locking.
• Application: lifting machinery, elevator transmission system.

Herringbone gear

• It is composed of left and right oblique teeth with symmetrical rotation, high bearing capacity and smooth transmission.
• Applications: propulsion systems for large ships, heavy machinery.

Planetary gears

• Multiple gears rotate around a central sun wheel for a large transmission ratio and compact construction.
• Application: Automatic transmission, planetary reducer.

For example, in industrial production, the transmission system of large fans may use bevel gears; In the spindle transmission of CNC machine tools, high-precision cylindrical gears are often used.

There are a variety of materials used to produce gears, common ones are the following:

Steel

• 45 steel: has good comprehensive mechanical properties, the price is relatively low, often used in the general transmission of medium and low speed light load gear.
• 40Cr: has good strength and toughness after tempering treatment, suitable for medium-speed and medium-load gear.
• 20CrMnTi: After carburizing and quenching, the surface hardness is high, the core toughness is good, and it is often used for important gears that bear impact loads, such as automotive transmission gears.

Cast iron

• Gray cast iron: such as HT200, HT250, etc., with good vibration damping and wear resistance, often used in low speed, light load, no impact of open transmission gear.
• Ductile iron: mechanical properties better than gray cast iron, can be used for more important gear.

Non-metallic materials

• Engineering plastics: such as nylon, polycarbonate, etc., with light weight, low noise, corrosion resistance and other advantages, often used in light load, low speed and accuracy requirements are not high occasions, such as the gear in the instrument.

Non-ferrous metals

• Copper alloy: such as tin bronze, aluminum bronze, etc., has good wear resistance and anti-friction, often used in heavy duty gear with high sliding speed.

For example, in the transmission system of ordinary machine tools, some unimportant low-speed gears may be made of gray cast iron; In high-performance automotive engines, the gears are usually made of high-quality alloy steel.

The manufacturing process and materials of gears have a significant impact on their performance, as follows:

Manufacturing process impact:

1. Accuracy and profile accuracy:

• Precise manufacturing processes, such as gear hobbing, grinding, etc., can ensure the gear profile accuracy and pitch accuracy, so that the gear is more stable in the transmission process, reducing vibration and noise.
• For example, the gear made by the high precision gear grinding process is applied to the precision transmission system of CNC machine tools, which can ensure the machining accuracy and surface quality.

2. Surface quality:

• Good manufacturing process can obtain smooth tooth surface, reduce friction coefficient, improve gear transmission efficiency, reduce wear.
• For example, gear surfaces that have been honed or polished can effectively extend their service life.

3. Strength and hardness:

• Appropriate heat treatment process, such as carburizing, quenching, etc., can increase the surface hardness and core toughness of the gear, improve its load bearing capacity and fatigue resistance.
• For example, the gears in the automobile gearbox are usually carburized and quenched to withstand large loads and frequent shifting impacts.

4. Residual stress:

• Machining methods and heat treatment during manufacturing can create residual stress inside the gear. Reasonable control of residual stress can improve the fatigue life of gear.

Material impact:

1. Strength and hardness:

• High-strength materials, such as alloy steel, can withstand greater loads and are suitable for gears with heavy loads and high-speed drives.
• For example, the gears of large mining machinery are usually made of high-strength alloy steel.

2. Wear resistance:

• Materials with good wear resistance, such as carburized steel, copper alloys, etc., can reduce tooth surface wear and maintain gear accuracy and transmission performance.
• Like the gear in some equipment that often starts and stops, better wear-resistant materials are needed to ensure long-term stable operation.

3. Toughness:

• The toughness of the material determines the fracture resistance of the gear under impact load.
• For example, in the case of large impact conditions, the selection of materials with better toughness can prevent sudden fracture of the gear.

4. Cost:

• The price difference between different materials is large, which will affect the manufacturing cost of the gear and the price of the final product.

In summary, the selection of manufacturing processes and materials needs to consider factors such as the use of the gear environment, load conditions, accuracy requirements and cost to ensure that the gear has good performance and reliability.

Gear manufacturing is a sophisticated and complex process designed to create high-quality gears for diverse transmission needs. The first is the design and planning process, according to the specific requirements of the transmission system to determine the gear parameters, and comprehensive consideration of the use of conditions to select materials and processes. Material preparation stage, commonly used steel, cast iron, copper alloy, etc., through forging, rolling or casting to obtain rough. Gear shape processing is realized by hobbing, gear shaper, shaving, grinding and other processes, and different processes have different application scenarios. Heat treatment enhances gear performance, finishing ensures installation accuracy, quality inspection is strictly controlled by professional tools and instruments, and surface treatment improves corrosion resistance and appearance. Gear manufacturing technology continues to evolve to meet higher transmission performance and reliability standards.Get a quote