Evaluating the positional error of a slant bed turning centre induced by a tool-turret mounted static load

摘要

Turning centres are invariably loaded with a range of tooling situated around the turret in a non-uniformly distributed manner which can impose an out-of-balance load condition. In order to investigate the effect on the positional accuracy of the slant-bed turning centre, a substantial mass of approximately 40kg was positioned out-of-balance on the turret. The mass was used to establish whether such a load should be recognised as a source of machine tool error and hence, if any form of compensated measures need to be implemented as a result of such uneven loading. The technique used to expose the possibility of positional errors was laser interferometry, with typical tests being for linear displacement, straightness and angularity of both axes of the machine tool. Tests were performed on the turning centre in both the loaded and unloaded condition providing a comparison between the machine's positional performance under differing conditions. This paper indicates that by taking such factors as the variability of thermal conditions and experimental errors into account, the effects on the machine's positional accuracy were negligible and compensation for this type of tool loading condition was not necessary. This work describes the limits of static positional calibration errors and points the way to the need for further dynamic performance assessment, in order to attribute whether such out-of-balance mass factors become significant and require calibration during cutting operations.