（1） Cylindrical gear machining
（2） Worm pair machining
（3） Bevel gear machining
（4） Special gear processing
（5） Gear machining method selection
All kinds of gear processing methods have one or more corresponding gear processing machine tools and cutters. Different industries (production batches) have different production conditions. According to the types, materials, heat treatment and accuracy requirements of gears, the processing methods can be reasonably selected with reference to tables 1-8 to 1-10. The selection of accuracy levels in the table is applicable to the following three situations:
1.The lower accuracy level has no special requirements for machining machine tools, cutting tools and gear cutting operations, which can be achieved in general.
2.The intermediate accuracy level requires that the machining machine, cutter and gear cutting operation are in the best condition to achieve the accuracy level.
3.The higher precision level can only be achieved under specific conditions by taking special measures.
Gear accuracy class: class 8-7-7dc new standard: 8-7-7kl GB / t10095
The accuracy of the gears in the forklift gearbox is generally in the range of 5, 6, 7, 8 and 9
8 – motion accuracy; 7 – working stability accuracy; 7 – contact accuracy; DC – backlash
Kinematic accuracy – the maximum error of the return angle of a gear in one revolution.
Kinematic accuracy – affects the accuracy of the transfer speed and indexing of the mechanism.
Working stability accuracy – the value repeated many times among all the error values of the internal rotation angle of a gear, that is, the change of its instantaneous transmission ratio is limited to a certain range.
Working stability accuracy – impact and noise of the mechanism are affected.
Contact accuracy – the proportion of the actual contact area.
Contact accuracy – affects the contact strength of the tooth surface
D-zero guaranteed backlash, used for reading drive gear in the instrument
DB – small guaranteed side clearance, used for gear transmission requiring forward and reverse rotation but not high speed.
DC – standard guaranteed side clearance, used for general machine gear, reducer, etc.
De – large guaranteed side clearance, used for gears in high-speed and high-temperature working environment, as well as open drive gears of heavy equipment, etc.
New standard: K (upper deviation) = – 12fpt L (lower deviation) = – 16fpt FPT – pitch limit deviation K, l, FPT are all determined by accuracy level, modulus and pitch circle diameter.
Selection of gear accuracy class:
Different accuracy levels should be selected according to different working conditions. When choosing different precision level combinations, the working stability precision level can be higher or lower than the motion precision level, but not higher or lower than the second level. The contact accuracy level shall not be lower than the working stability accuracy level.
When selecting the accuracy grade of gears, the main accuracy shall be determined as the basis for selection according to the purpose of transmission, working conditions, transmission power, peripheral speed and other technical requirements.
When determining the accuracy level, we should also consider the processing conditions and correctly handle the contradiction between the accuracy level and the processing conditions and the economy. For example, for the gears of high-speed transmission, the requirements for the working stability accuracy are the main; for the gears of indexing mechanism, the movement accuracy is the main; for the gears of heavy load transmission, the contact accuracy is the main; for the gears of high-speed and high-temperature transmission, the working stability accuracy and side clearance are the main.
Normally:
Selection of motion accuracy level:
|
Accuracy Grade |
Application Scope |
Tooth Surface Roughness |
|
5-6 |
Peripheral speed ＞ 15m / S (spur), ＞ 30m / S (bevel) |
Ra 0.4-0.8 |
|
7 |
Peripheral speed < 10 m / S (spur), < 15 m / S (bevel) |
1.6 |
|
8 |
Peripheral speed < 4m / S (spur), < 6m / S (bevel) |
3.2 |
|
9 |
Unimportant gear drive and low speed and heavy load drive |
6.3 |
Selection of working stability level:
|
Noise |
Circumference Speed |
Spur：＜3 m / S |
＞3-15 m / S |
＞15 m / S |
|
Bevel：＜5 m / S |
＞5-30 m / S |
＞30 m / S |
||
|
85-95 Decibel |
8 Level |
7 Level |
6 Level |
|
|
75-85 Decibel |
7 Level |
6 Level |
5 Level |
|
|
＜75 Decibel |
6 Level |
5 Level |
5 Level |
|
Selection of contact accuracy level:
|
Noise |
Load : |
Heavy |
Medium |
Light |
|
85-95 Decibel |
6 Level |
7 Level |
8 Level |
|
|
75-85 Decibel |
6 Level |
6 Level |
7 Level |
|
|
＜75 Decibel |
5 Level |
5 Level |
6 Level |
|
There are 23 tolerances for measuring gears.
The main factors affecting the stability, noise and vibration of gear transmission are as follows:
1.One tooth tangential comprehensive tolerance;
2. One tooth radial comprehensive tolerance;
3. Tooth profile tolerance;
4.Pitch limit deviation;
5. Base section limit deviation;
6. Helix waviness tolerance.
Therefore, the measurement of the above tolerance is particularly important.
At present, the actual situation of the company is that the “one tooth radial comprehensive tolerance” can be judged qualitatively only after some mandrels are equipped. To measure the tolerance data quantitatively, it is necessary to measure the standard gear. No other projects can be done. Because of the current testing methods, only one “one tooth radial comprehensive tolerance” can be used to determine whether the parts are qualified.