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Offset machine noise operation at high speeds always, and as the
printing speed increases, the noise increases accordingly. However, noise can be harmful to the health of the operator. Therefore, when designing and producing offset presses, efforts should be made to study the source of noise and effectively control the noise.
Gears are one of the main sources of noise generated by offset presses. The factors affecting gear noise include the following aspects.
Gear type
Different types of gears have different meshing forms. When the load and speed are the same, the noise generated by the helical gear during the meshing process is 3 to 10 dB lower than that of the spur gear. Therefore, the offset power transmission system mostly uses helical gears.
2. Pressure angle
Gear transmission systems must maintain a constant force in order to deliver a certain amount of power. If the gear pressure angle increases, the normal force of the tooth surface will increase, so that the pitch impulse and the meshing momentum of the gear on the actual tooth surface will also increase, resulting in gear vibration and noise. The gear pressure angle will change periodically due to the variation of the gear center distance error. If the gear is eccentric on the shaft, the gear transmission will generate vibration and affect the noise frequency. The amplitude of the vibration will depend on the amount of eccentricity. .
3. Coincidence
When the gear teeth transmit the load, different degrees of deformation occur. At the moment when the gear is engaged and engaged, the meshing force is generated along the meshing line of the gear, which causes certain torsional vibration and noise during the gear transmission. If the gear coincidence degree is increased, that is, the average number of teeth at the moment of meshing, the load can be distributed to more gear teeth, and the tooth surface unit pressure can be reduced, thereby reducing the deformation of the gear teeth and improving the impact of the moment of engagement and engagement. The phenomenon, in turn, reduces the torsional vibration during gear transmission and reduces noise. When the gear coincidence is increased from 1.19 to 2.07, the 4dB noise can be reduced when the gear speed is 1000rpm, and the 6dB noise can be reduced when the speed is 2000rpm.
For the helical gear, changing the helix angle and the tooth width of the gear can increase the degree of coincidence, but the helix angle should not be too large, otherwise the helical gear will generate axial vibration. In addition, by increasing the number of gear teeth, increasing the height of the tooth tip or reducing the gear pressure angle, the gear coincidence can be increased, thereby achieving the purpose of reducing noise.
4. Gear precision
Gear accuracy has a great impact on gear noise, and the first step in reducing gear noise is to improve gear accuracy. In a single error, the pitch (base or circumference) and tooth profile have the greatest impact on gear noise.
(1) Pitch. In the range of one gear rotation, even if only one pitch error is large, the gear will produce significant noise. Moreover, as the gear speed or load increases, the gradient of gear noise increases and decreases.
(2) Tooth shape. Only based on the size of the tooth shape error can not determine whether it has an impact on the gear noise, the focus should be on the shape of the tooth shape error, such as the appearance of "concave" near the gear node, it will significantly increase the gear noise.
(3) Ring gear radial runout. The radial runout of the ring gear causes the cumulative error of the pitch, which affects the stability of the gear transmission and increases the noise during gear transmission.
5. Gear parameters, structural shape
(1) Gear diameter. If the spur gear is regarded as a circular plate, according to the acoustic principle, the noise radiated around the gear depends on the area of ​​the sound radiation, so increasing the gear diameter will not help to reduce the gear noise.
(2) Tooth width. Gear noise will decrease as the tooth width increases, but increasing the tooth width tends to increase the toothing error when manufacturing and mounting the gear, which is not conducive to reducing the meshing momentum and noise of the gear.
(3) Structure of the tooth blank. The structure of the spur gear blank is generally of the integral type and the spoke type. Among them, the gear blank structure is a spoke type gear with high noise, and the damper ring can appropriately reduce the noise.
6. Gear processing technology
(1) Shaving process. In the shaving process, the gear is shaped by a shaving cutter to improve gear transmission stability, reduce meshing shock, and reduce gear noise.
(2) Dental caries process. The caries process is mainly to improve the surface finish of the tooth profile, and the cutting amount is preferably 0.01 to 0.02 mm, otherwise the precision of the machining process in front of the gear will be destroyed.
7. Gear teeth deviation and elastic deformation
Due to the deviation of the tooth and the base section and the elastic deformation of the tooth, when the gear is engaged or bitten, the impact and the angular velocity change, that is, the interference of the top edge interferes. When the passive wheel circumference or base is larger than the nominal value, the top edge meshing phenomenon will occur at the top of the passive gear tooth, thereby generating vibration and noise. In this regard, the teeth should be trimmed into drum-shaped teeth so that the load first contacts the area near the middle of the tooth width and then gradually expands to the entire tooth width to improve the distribution of the load, thereby reducing vibration and reducing noise. (Liu Yidong finishing)
The above content is selected from the section of "Printing" Technology ·Packaging and Decoration 》2012, No.12, more journal content please pay attention to the journal channel, the latest journal content click to enter the Keyinwang electronic journal channel.
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