Sensing linear roller guide carriages for condition monitoring applications

Insufficient lubrication is a common cause of rolling guide failure. Especially high process forces during machining of high-strength materials such as titanium-based alloys cause strong loads on these machine components. That is why maintenance is particularly important during the manufacturing of aerospace components. Especially here, scrap parts lead to high costs. Furthermore, rework, e.g. in order to maintain tolerances, is often not possible. An approach to avoid unnecessary machine tool downtimes due to maintenance is to use condition monitoring systems. The aim is to draw conclusions about the condition and remaining service life of machine components through continuous data collection and evaluation of sensor signals during operation. This means that maintenance intervals and thus downtimes can be planned and unexpected downtimes are avoided. In this paper, an approach is presented to evaluate the grease condition of linear roller guide carriages by integrated sensors. The measured signals are analyzed in its frequency domain to detect lubrication-dependent signal characteristics. Differences in the characteristic frequencies are used to identify a change in the lubrication condition. It is examined whether semiconductor strain gauge sensors or conventional rosette strain gauge sensors are more suited for this approach. The results show that both strain gauge types are able detect lubrication-related differences in the strain signal. But in contrast to rosette strain gauge, semiconductor strain gauge lubrication-related signal changes are more definite. Thus, the use of semiconductor strain gauges for lubrication condition monitoring requires less signal data processing.