Advancing Reconfigurable Manufacturing: Length-Adjustable Feed Axis and Stiffness-Adjustable Module for Modular Reconfigurable Machine Tools

In today's manufacturing, rising demand for customized products and shorter product cycles challenges traditional systems, which adapt poorly to changing workspace needs and process dynamics. Reconfigurable manufacturing systems based on modular reconfigurable machine tools (MRMT) are promising, but current adaptability is mostly limited to swapping whole modules instead of tuning a single module's properties. This paper investigates the adaptation of two key MRMT properties at module level: the travel range of a feed axis and the chatter stability of a milling process. Two hardware demonstrators are used for this investigation: a length-adjustable rack-and-pinion feed axis that can be extended with attachable segments and a stiffness-adjustable interface that can vary static and dynamic stiffness via a preloaded spring plate. Laser-tracker measurements show that the travel range can be extended while keeping the maximum straightness deviation at \SI{175.88}{\micro\metre} and rotational deviations within \SI{0.1}{\degree}. Static load tests yield stiffness ranges of \SIrange{644.47}{2089.35}{\newton\per\milli\metre} (\SI{4}{\milli\metre} spring plate) and \SIrange{694}{2613.93}{\newton\per\milli\metre} (\SI{5}{\milli\metre} spring plate),
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and impact-hammer tests show a shift of the dominant natural frequency of the module of \SI{56.45}{\percent}. Stability lobe diagrams computed from the measured frequency response functions confirm that the module deliberately shifts the lobe positions along the spindle-speed axis, enabling in-situ adaptation of process stability limits.