A strategy for minimization of thermal error in headstock assembly of CNC lathe

Abstract

The thermo-elastic behavior of the spindle system in a CNC lathe contributes significantly toward the undesirable displacement at the tool center point (TCP). Minimization of the thermal deformation of spindle has become progressively important for the development of ultra-precision machine tools. To serve the purpose of predicting the characteristics of the heat flow and the corresponding thermal deformation, a finite element model for the headstock assembly of CNC lathe is developed. Heat generation and heat dissipation in the components of headstock assembly of CNC lathe are estimated for free running as well as machining conditions using empirical models. The thermo-elastic behavior is investigated with the aid of numerical model validated by experimentation. The deformation of bed is found to possess a significant influence toward the spindle displacement in X-axis which results in form error in the machined component. The proposed strategy is validated effectively to have control over the heat flow between headstock and bed with the aid of a carbon/epoxy laminate that results in a near zero displacement along the X-axis of the spindle.

Keywords:

• Machine tool
• thermal error
• mathematical modeling
• finite element analysis
• composite material

Acknowledgments

The authors gratefully acknowledge the Government of India, Office of the Principal scientific adviser, New Delhi, for the grant of project (Prn.SA/ADV/MT/2/2007) as the present work is the continuation of the above research project. The authors would like to express their sincere thanks to Shri. L. Gopalakrishnan, Managing Trustee, PSG Institutions, Dr. P. Radhakrishnan, Director, PSG Institute of Advanced Studies, Dr. R. Rudramoorthy, Principal, PSG College of Technology and Dr. P.V. Mohanram, Principal, PSG Institute of Technology and Applied Research, for supporting the activities of the research work.