| A five-axis machine tool because of its two rotary axes is more flexible in positioning and orienting the workpiece and the tool which in turn reduces the unproductive time of the machine. However, five-axis machine tools, having more moving components and lower stiffness exhibit more geometric and kinematic error sources than a three-axis machine. Measuring instruments and methods are then vital to evaluate machine performance, find error sources and estimate errors for maintenance planning and compensation purposes.;In the first part, five new and simple tests for a rotary axis are prepared using a DBB. Studying sensitivity Jacobian matrix and its singularity, error sources in the five developed tests are investigated, and the possibility of separating rotary axis motion errors from tests results is demonstrated. By using the Jacobian matrix, the motion errors can be calculated but when there are too many measuring points and data, the calculation takes excessive processing time. Consequently an analytical mathematical method is developed for the calculation purpose. The advantages of this measuring and analysis method are: 1- the DBB is widely used in industry for linear axes, it is easy to use, accurate and inexpensive, 2- there are two simple setups and setup errors are detected and separated from rotary axes errors easily 3- it is a continuous measurement and provide a full error map and 4- the method takes between 15 to 30 minutes for each rotary axis measurement. This method is verified in simulation as well as in practice.;The second part concerns a new instrument called "CapBall", and the necessary method to investigate five-axis machine tool errors. The CapBall uses three orthogonally mounted capacitive transducers to measure the change in relative position between the tool and a point (ball centre) on the workpiece (machine table). The concept allows synchronised five-axis motion and the non-contact sensors render possible quasi-static as well as high speed motions for dynamic assessment. Furthermore, the availability of the 3D error at each machine position facilitates the estimation of machine error parameters. Practical tests results are presented for an XYC combined motion on a horizontal five-axis machine tool. The volumetric errors are used to estimate error parameters using the Jacobian matrix approach. The comparison of some identified error parameters with those obtained through a magnetic double ball bar tests shows a generally good agreement between the CapBall and the ball bar results.;Keywords: Five-axis machine tool, Rotary axis, Geometric errors, Ball bar, Capacity sensor.;Instruments and methods are well developed and commercialized in the case of the linear axes. In this regard, the two most important instruments are the laser interferometer and the double ball bar (DBB). For rotary axes however, some work has been done but the lack of a robust and simple method or instrument persists. This thesis concerns the rotary axis errors. |
