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Our new axis, measured, the full-length actual round runout is 0.10mm, far less than 1.09 to 1.82mm. The allowable deflection value is the crack on the foundation of the installation. We transferred the problem to the concrete foundation. Through the scanning test of the concrete crack state of the installation foundation, it was found that there was no problem in the foundation. In order to reduce the vibration problem of the foundation, we had to reinforce the foundation beam at the installation position of the equipment, that is, 10 F219 rounds in the lower beam of the foundation seat. The tube is supported and reinforced. After such treatment, the vibration phenomenon of the equipment foundation has improved, and the speed of the vehicle has improved slightly, but it has not met our needs. The original long-gear transmission shaft processing diagram II. Problem analysis and problem solving are neither On the basis of the installation, vibration due to insufficient strength and rigidity of the shaft is also excluded. Where is the problem verified by many aspects, the problem is that on this axis, we know that the shaft is an elastic body. When it rotates, due to the uneven material structure of the shaft and the parts on the shaft, the manufacturing has errors, or In the case of bad, etc., it is necessary to generate a periodic disturbance force characterized by centrifugal force, thereby causing bending vibration (or lateral vibration) of the shaft. If the frequency of this forced vibration coincides with the bending of the shaft from the vibration frequency, a bending resonance phenomenon occurs. Torsional vibrations are caused when the shaft undergoes periodic torsional deformation due to periodic changes in the transmitted power. If the forced vibration frequency coincides with the torsional natural frequency of the shaft, it also produces torsional resonance that has a destructive effect on the shaft. If the shaft is subjected to periodic axial disturbances, it will naturally also produce longitudinal vibration and longitudinal resonance under the corresponding conditions. The speed at which the shaft causes resonance is called the critical speed.
If the speed of the shaft stagnates near the critical speed, the deformation of the shaft will increase rapidly to the extent that the shaft or even the entire machine is damaged. Once away from the critical speed, the rotor runs smoothly without vibration. To avoid the critical speed, the operating speed should be n<0.75nci.
According to the analysis of the on-site measurement data, the reason for the vibration is not the insufficient rigidity of the shaft, and it is likely that the resonance is caused by the working speed approaching the critical speed. Through calculation and analysis, our vacuum roller drive shaft belongs to this type of high-speed rotary shaft. When the speed of the net section is 670m/min, its speed is up to 1200rpm. Next, we turn the problem to solving and verifying the vibration frequency of the shaft.
It is understood that although this paper machine has undergone many technical transformations abroad, the design speed of the theoretical Internet department can reach 671m/min, but in foreign countries, the highest speed that was opened at that time was around 450m/min, and it has not yet opened to 500m. /min or more, so the above-mentioned resonance damage problem has not occurred in this axis. This problem only manifested when we increased the speed to 500m/min.
Conclusions (1) When designing mechanical equipment, the shaft with high rotational speed should not only check the strength and stiffness of the shaft, but also fully consider its resonance characteristics, and reasonably calculate the influence of resonance on the rotating shaft. For a rigid shaft to operate at a speed of n < (0.75 ~ 0.8) nc1, when designing the shaft without affecting mechanical properties and working requirements, the first-order critical speed should be higher, so that when the shaft is in operation, Regardless of how the speed changes, the probability of approaching the critical speed is less, to ensure the safety of the machine.
(2) When designing the shaft, if the rationality of the shaft is considered, the following problems should be noted: 1 Under the premise of not affecting the ergonomics, try to reduce the speed, minimize the length span, and length the overhang. Also shorten. 2 Use a material with a large modulus of elasticity to minimize the weight of the shaft itself. 3 From the perspective of the transmission, the force of the shaft should be evenly distributed. The support form of the 4-axis changes, and the calculation mode of the critical speed nc1 also changes accordingly.
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