Linear backlash-free tappet-drive

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Linear drive systems in machine tools should transmit high forces in order to achieve high dynamics. At the same time, the positioning should be as accurate as possible. Different drive systems have specific advantages and disadvantages. The established systems with mechanical power transmission such as ball screws and rack and pinion drives have the primarily problem of backlash in the drive train, which reduces positioning accuracy. In order to compensate for or avoid the backlash, additional mechanical components or additional control engineering approaches are required. Furthermore, the point or line shaped contact spots limit the maximum transmittable force. In addition, ball screws have a limited operating range due to their length-dependent rigidity. As an alternative to existing systems, a novel drive system is proposed which is backlash-free, has increased rigidity and can be used for feed axes of any length. The novel system is a rack drive with individually driven and controlled teeth (tappet) with straight tooth flanks. This leads to a real surface contact between the single tooth and the rack, which enables an increased power transmission. A suitable number of individual teeth and their arrangement can ensure freedom from backlash in the system. Possible implementations were designed in advance. Within the research project, a variable test bench shall be set up, which will allow various mechanical and control concepts to be tested and their potential to be assessed. The novel concept promises a new alternative for linear drive systems with very high demands on the drive unit in terms of positioning accuracy, maximum force and rigidity.