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Noise Analysis Report of Injection Tensioner

2020.3.3

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1、Problem description:

In Feb., 2020, received 2 wheel bearing samples, the technical problems are as follows：
Sample A: after 62 hr made loud sound 
Test conditions: rotate speed 10000 rpm, load 50 kg, running 110hr, 100 °C

Sample B: after 160 hr made loud sound 
Test conditions: rotate speed 5000 rpm, load 50 kg, running 500hr, 100 °C

DYS technician systematically analyzes the bearings of samples A and B to find out the cause of noise out of tolerance under the test time.
After the test, the bearing is shown in Figure 1.

2、Cause analysis:

2.1 According to the appearance of the bearing after the test, the surface is as clean as new, the hand feeling bearing is not stuck, and there is no grease exudation on the surface of the bearing. BVT and S0910 are respectively used to test the bearing vibration with rubber wheel, and the test results are shown in Table 1：

2.2 Check the radial runout and axial runout of the whole set of bearings together with the pulley. The measurement method is shown in Fig. 3, and the measurement results are shown in Table 2

From the measurement results in Table 2, it can be seen that the axial runout of DK6203-2RS wheel is significantly larger, but because there is no relevant standard for radial and axial runout of the wheel after injection molding in the industry, this data can only be used as a reference for evaluation

2.3 Remove the outer wheel and check the vibration of the bearing again. See Table 3 for the test results.

According to the test results, both the velocity type vibration value and acceleration type vibration value meet the requirements of Z2 group and V2 group before delivery.

2.4 Check the clearance of the bearing, wash off the grease of the bearing at the same time, and calculate the greasing amount of the bearing. See Table 4 for the measurement results

The results showed that the grease amount of DK6203-2RS decreased slightly, and exceed downward rate 7.5%.

 2.5 Disassemble the bearing, and test the roughness, roundness, groove curvature and waviness of the inner and outer rings respectively. See Table 5 for the test results

According to the test results, the inner and outer ring waviness of DK6203B14-2RS and the inner ring waviness of DK6203-2RS are out of tolerance. But there is no difference between other parameters  before delivery

3、Analysis conclusion:

3.1  The decibel value of the outer wheel with and without the outer wheel is less than 36 decibels, which meets the quality requirements before delivery, and the vibration value of speed type also meets the requirements of V2 group, and the sound is very uniform, without abnormal sound

3.2  The residual grease amount of DK6203-2RS is 0.6g, which is less than the lower limit of 0.65g compared with the amount of grease filling before delivery, and the grease loss rate is 7.5%. However, since the bearing has been tested for 160 hours, this reduction is normal.

3.3  After the bearing is disassembled, the internal parameters of the bearing are tested. The corrugations of the inner and outer rings of DK6203B14-2RS and the inner rings of DK6203-2RS are all 0.2 μ higher than the standard value, but the surface of the bearing raceway is still bright as new, especially the roughness is only 0.02, which is still the level before delivery. This shows that there is no wear in the raceway after the test. The excessive corrugations are related to the long-term deformation of the outer ring after the bearing injection molding.

Result analysis:
1.The bearing and the wheel after injection are not found to be abnormal.

2. Determine if the bearing noise problem is measured by the senses or sensors, there will be certain errors (such as objective noise generated by the test environment). If the belt of the testing machine is loose, the motor that provides power will bring noise interference.

3. DYS judges the bearing noise in the internal test tensioner bearing by monitoring the temperature change of the bearing.
The above conclusions are for customers' reference.

                                                                       DYS Technical Department. Feb. 25, 2020

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