Gear Machining Guide Explain with Video, Machining Methods and Processes
Last updata 06/11
In the manufacturing and operation of machinery, gears as an important component, for mechanical rotation, to ensure the normal operation of machinery plays a key role, gear manufacturing is to a certain extent determine the overall quality of machinery and operational efficiency.
This article introduces six scenarios of gear processing methods. Gear manufacturing process processing methods, machining processes and their requirements are discussed, combined with the gear manufacturing process in the application of common problems in the processing process and solution strategies, to provide a simple guide for your gear processing and manufacturing, so that you can choose the right process, you can also contact our engineers to obtain gear manufacturing-related information.
1 Illustration of 6 types of gear mechanical machining
2 Gear manufacturing process machining process and its requirements
3 Common problems and solutions in the application of machining processes in the gear manufacturing process
1 Gear Mechanical Processing Method
Gears have various forms of tooth shape, of which involute tooth shape is the most common. There are two major types of machining methods commonly used for involute tooth shapes, namely the forming method and the spreading method.
Milling teeth with disc-shaped modulus milling cutter belongs to the forming method, and the shape of the cutter cross-section corresponds to the shape of the gear teeth. The teeth are machined out. After milling one tooth tip of the gear, the indexing mechanism is manually indexed to turn a tooth, and then another tooth slot is milled, and so on, until the end of all milling.
Gear machining by milling method
This method has low processing efficiency and accuracy, and is only suitable for single piece and small batch production.
Also belongs to the forming method processing, grinding wheel is not easy to dress, so less use.
Forming and grinding gears
The tool for cutting the gear blanks during hobbing is a hob, which is a worm because of the large spiral lift angle of the hob. The hob is slotted in the direction perpendicular to the spiral groove, forming a number of cutting edges, and its normal profile has a rack shape.
Therefore, when the hob rotates continuously, the gear wheels can be regarded as the movement of an infinitely long rack. At the same time, the cutter gear cuts from top to bottom, keeping the meshing relationship between the rack (hob) and the gear blank, and the hob can process the involute gear shape on the gear blank.
Principle of gear hobbing
- Process characteristics
(1) The hobbing processing of the spreading method has high processing accuracy, and there is no theoretical error in the gear curve of the shaping method of milling, so the splitting accuracy is high, and it can generally process gears with 8~7 levels of accuracy.
(2) A hob can process cylindrical gears with the same module and pressure angle as the hob but with different tooth numbers.
(3) High productivity hobbing is continuous cutting, no auxiliary time loss, productivity is generally higher than milling and inserting gears.
Hobbing is suitable for single-piece small-lot production and mass production.
In mass production, gear shaving is a common finishing method for non-hardened tooth surfaces. Its working principle is to use the shaving knife and the gear to be processed for free meshing movement, with the help of the relative slip between the two, from the tooth surface shaving very fine chips, in order to improve the accuracy of the tooth surface. Shaving can also form drum-shaped teeth to improve the position of the tooth contact area.
- Process characteristics
1. Shaving accuracy is generally 6 to 7, surface roughness Ra is 0.8 to 0.4μm, for the finishing of unquenched gears.
2. High productivity of shaving, processing a medium size gear generally only 2 to 4 min, compared with grinding, can improve productivity by more than 10 times.
3. Because the shaving process is free meshing, the machine does not spread into the motion of the drive chain, so the machine structure is simple, easy to adjust the machine
Shaving is a widely used method for finishing gear teeth, especially for continuous production of large quantities, and is generally used for finishing unhardened gears because of its high-cost performance. Shaving is currently used mainly for finishing cylindrical gears, but this method was initially used for shaving worm gears. In the early days, there were also bar shaving cutters, which were also used for finishing cylindrical gears, but due to their overly complex structure, they are rarely used at present.
Gear shaping is a kind of gear cutting process that is commonly used in addition to hobbing. When shaping, the gear shaper and the workpiece are equivalent to the meshing of a pair of cylindrical gears. The form of movement of the workpiece and the gear shaper is shown in Figure a. During gear shaping, the tool makes a high-speed reciprocating linear motion in the direction of the workpiece axis and processes all the gear tooth profiles on the workpiece. In the process, the tool only cuts out a small part of the workpiece tooth groove with each reciprocation, and the tooth surface curve of the workpiece tooth groove is composed of the envelope of the cutting edge of the inserting knife, as shown in Figure b.
The principle of gear shaping
Generally speaking, the productivity of hobbing is higher than that of shaping, because shaping is a reciprocating motion and the return stroke does not cut. The gear shaping system is less rigid and the cutting amount cannot be too large. However, for small modulus gears (m<2.5 mm), the productivity of shaping may be higher than that of hobbing. For thin gears, single piece production, hobbing cutting length is large, may not be as productive as shaping.
6） Gear grinding by spreading method
The cutting motion of the spreading method is similar to that of hobbing and is a tooth finishing method, especially for hardened gears, which is often the only finishing method. The spreading method can be used to grind teeth with worm gears or with conical or disc grinding wheels.
2 Gear manufacturing process machining process and its requirements
1）Forging of blanks
The forging of blanks process in gear manufacturing is widely used, usually in the form of forging and hot embossing. With the gradual development of gear manufacturing and processing technology, the cross-rolling technology has gradually started to be widely used in the production of mechanical shafts, especially in the processing and manufacturing of stepped shaft type workpieces. The rough forging process requires high processing efficiency and accuracy to reduce the cost of gear manufacturing and reduce the waste of resources.
Forging of blanks
Gear manufacturing is difficult to control the cooling rate of the workpiece, which is influenced by the surrounding environment, equipment problems, manual operation and other factors, causing certain obstacles to the uniformity of the organizational structure, so it is necessary to heat treat the metal cutting. This process applied to the isothermal normalizing process refers to the problem of avoiding thermal deformation of gear steel materials at a suitable temperature after gear cutting hardness and heat treatment processing.
Gear manufacturing and processing for gear positioning accuracy requirements are high, at present in the processing of gear blanks usually need to apply to the CNC lathe, according to the requirements of the end face and bore for verticality, improve the accuracy of the tooth blank, to ensure the quality of gear manufacturing and processing, including bore, end face, outer diameter processing quality, etc.. Improve the processing efficiency of CNC lathe effectively guarantee the economic benefits and reduce the number of equipment.
4）Hobbing and inserting
In order to improve the service life of the tool, after the hobbing, inserting knife sharpening, with the role of re-coating technology, reduce the number of tool replacement, effectively ensure the life of the tool, to provide a guarantee of stable processing, and promote the economic efficiency of production.
In the finishing process of gear manufacturing, shaving is one of the very common processing methods, is widely used in gear manufacturing production, as a key production process, shaving has strong advantages, not only high efficiency, and has the advantage of easy to achieve the tooth shape and tooth orientation requirements.
Heat treatment process, in the gear manufacturing processing methods, the most common to nitriding, carburizing, quenching heat treatment in these ways. After this process, the surface hardness of the gears is greatly increased, and the plastic toughness of the center is greatly enhanced, which promotes the extension of gear life and effectively strengthens the fatigue resistance and wear resistance of the gears.
The grinding process in gear manufacturing refers to the finishing process for certain positions, including the outer diameter, inner lining and end face of the gear, in order to promote the improvement of assembly and installation accuracy.
Inspection is a critical part of the gear manufacturing process and refers to the inspection and cleaning of the teeth, which is usually carried out before the gear is assembled. Comprehensive observation and analysis of tooth fit deviation, the application of comprehensive inspection instrument, improve the effectiveness of the inspection to prevent problems such as gear noise.
3 Common problems and solutions in the application of machining processes during gear manufacturing
Q: Inaccurate number of teeth
A: When the tooth number is inaccurate, more attention should be paid to the rational selection of hobs, and the hobs with similar helix angle, the same hob pressure angle and the same hob module should be used.
Q: Large tooth shape error
A: When the problem of large tooth shape error occurs, then adjust the hob installation angle in time. Determine whether the gear blank size and additional movement direction are accurate to ensure the quality of gear manufacturing.
Q: Tooth shape asymmetry
A: The common tooth shape asymmetry problem can be solved by adjusting the hob. Use a hob sharpening grinder with high accuracy and choose a reasonably priced and easy-to-operate hob sharpening grinder to promote the hob installation accuracy and hob sharpening quality. All-around check the installation and operation of the exchange gear, strengthen the stability of lathe operation, and improve the overall quality and processing efficiency of gear manufacturing.
Post time: May-17-2022