| Summary: | 碩士 === 崑山科技大學 === 機械工程研究所 === 103 === In this study, we studied the tribological performance enhancement on the toggle pin bearing of the plastics injection molding machine with the addition ultra-dispersed nano-diamond (UDD) additive. The criteria of the grease change period were also studied and tested.
The results showed that there are many advantages with the addition of UDD additive as compared to those without UDD additive: (1)The running-in period was reduced to only one half, (2)The coefficient of friction was reduced by 36.33%, (3)75.2% reduction in wear loss, (4)94.9% less in the ferrous debris concentration in the residual grease after the test, (5)18.3% reduction in vibration.
On the other hand, we established the grease change period by the signal processing acquired from the accelerometer. The vibrational signals were first processed by the empirical mode decomposition (EMD) and the first intrinsic mode function (IMF1) was thus derived. The fractal dimension (D) of the IMF1 was then calculated. Two criteria were set up for grease change period detection:
(1) The 5-point moving average of the standard deviation of the fractal dimension (D) is greater than 0.05;
(2) The difference between the most recent calculated D value and the D value of first one is greater than 0.1.
The two criteria had been effectively verified with the aids of other signals such as coefficient of friction, electrical contact resistance …etc. Besides, it’s found that the two criteria are independent of material types of the toggle pin bearing. Moreover, they can be used to detect the abnormal conditions of machine elements which will affect the vibration signals before these elements were out of order apparently.
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