High-speed spindle dynamic error separation technique

The accuracy of a subtractive machining process is affected by the error motions of the machine tool spindle. Excessive error or concern over the spindle condition can cause unscheduled downtime, scrap or rework, unexpected production delays, and customer disappointment. There are various techniques and measurement systems available for spindle error motion measurement. They typically include the use of several displacement sensors and a test bar. Different methods are available for the separation of spindle error motion from the roundness error of the test bar. The three main types of spindle error separation techniques are reversal, multi-probe, and multi-step approaches. The Donaldson reversal method is a common technique used for spindle error separation. In this method the artefact (test bar) and displacement sensor needed to be physically rotated to obtain each measurement.
In this research, a new implementation of the Donaldson reversal technique with multiple probes is developed so that the manual rotation of the measurement setup is not required. The artefact and spindle error motions are simulated in a computer-generated model. Various thermo-mechanical errors were introduced to evaluate the performance of the error separation algorithm for high-speed applications. The simulation result indicates that the effect of test bar roundness error along with external random errors has been separated and most of the system effects have been reduced. The outcome of this research can be used in an industrial spindle error measurement system.