Measuring And Modelling Heat Transfer And Thermal Errors On A Ballscrew Feed Drive System

Machine tool axes continue to employ rotary encoders mounted on the drive motors for position feedback. With this method the accuracy of the ballscrew determines the positional accuracy. Errors associated with expansion of the ballscrew caused by internally generated heat are well documented and have been found to be significant. The accuracy demands on even low cost machine tools continues to increase, requiring the manufacturing industry to invest more effort in understanding the capabilities of their machines. Many companies regularly calibrate machne tools using quick check Ballbar techques or, perhaps less frequently, laser interferometry to quantify the errors. However, thermal errors associated with operation of the machme are not normally indicated using these techniques. The IS0230 part3 standard details thermal error measurement including axis-heating checks. However, these are generally applicable and not duty cycle specific.