Scope and Objectives

Machine tool performance is fundamentally limited by process-induced vibrations that limit productivity and result in poor part surface quality. To avoid vibration related instabilities, machines are operated conservatively, resulting in their underutilization by a factor of two or more. To fully harness a machine's potential, this project will monitor, evaluate and renew machine performance by using structure integrated sensors and actuators. Real-time condition monitoring and system identification will be performed. Vibrations detected will be damped using structure integrated active damping devices. A hardware-in-the-loop simulator will be developed to test solutions before their implementation on real machines. Four investigators across two IITs will contribute their expertise to realize the project.

Deliverables

A number of technologies will be developed in this project which will significantly improve machine tool performance and productivity. The developed technologies will benefit all machine tool developer and user industries alike. Specifically, on successful completion of the project, we will have: 1. Improved performance of in-use machine tools by retrofitting them with sensors and actuators 2. Indigenously developed active damping devices that will have a compact design with high force throughput. We will develop three new solutions: a. A new and improved electrohydraulic damper, b. A new and improved light-weight electromagnetic damper, and c. A new eddy current damper capable of damping tool vibration modes 3. Developed active vibration control integrated with system identification to identify and damp unstable vibrations 4. Performed condition monitoring to detect machine tool wear and spindle bearing damage 5. Successfully demonstrated technologies at the Laboratory and Industrial levels 6. Trained our research associates for them to become highly qualified professionals 7. Integrated into laboratory exercises for our undergraduate and postgraduate level courses, the new technologies developed through this project will be. This will help train our students better. 8. Papers in International journals and conferences, and patents, if applicable

Scientific Output

Summary of major scientific progress: WP1 major progress: Time and frequency domain methods have been developed to estimate system dynamics using in-process measurement signals WP2 major progress: An actuator and a damper were integrated with a machine tool to excite, sense and damp vibrations. A real time control interface was developed entirely at IITK. As per our knowledge, this is the first such setup in the country. An improvement in damping was demonstrated. WP3 major progress: A HiL simulator for orthogonal cutting was developed. As per our knowledge, this is the first such setup in the country. WP4 major progress: A new electohydraulic actuator has been indigenously developed. The actuator specifications make it better than any other such device available commercially. A new eddy current damped boring bar has also been prototyped, and preliminary investigations suggest a considerable reduction in vibration amplitudes.

Results and outcome till date

Societal benefit and impact anticipated

The research plan is designed to monitor the states of a machine followed by experimentally characterizing and evaluating machine tool cutting performance with and without off the shelf active damping devices. Results of these findings will guide and instruct the development of new actuators. Since it is not possible to extensively characterize cutting performance of machines under all variations in operational parameters, we will also develop a hardware in the loop simulator to test solutions before their implementation on real machines. This systematic approach will help deliver solutions to machine tool user and builder industries to renew performance of their machines as well as expand functionality of their machine tools. Retrofitting old machines with new actuators to expand their functionality is new. Furthermore, indigenisation of low cost high performance active damping devices too has not been attempted before, and when successful it will enable these plug and play devices and solutions which will be easy for Industry to absorb. An instrumented hardware in the loop simulator that will use a real milling head of a machine tool will be new and representative of real conditions than any previous such investigations. Structure integrated actuators will also enable a light-weight machine tool designs, since any accuracy lost due to light-weighting will be replenished by actuators.

Next steps

Summary of challenges yet to be addressed: WP1 challenge to be addressed yet: Time domain methods are being developed that also allow for output only analysis, making them more practically implementable than frequency domain methods WP2 challenge to be addressed yet: Integration of an electromagnetic and electrohydraulic actuators and dampers on a large machine tool at IITK WP3 challenge to be addressed yet: The HiL is being tested for robustness to delays, filters, and their orders and cut-off frequencies. Integration of an active damper within the HiL is ongoing. Learnings form the HiL simulator for orthogonal cutting are being transferred to design the HiL simulator for milling, which is the main deliverable of this WP. WP4 challenge to be addressed yet: Development of an electromagnetic actuator is ongoing

Publications and reports

Some early work has been presented at conferences: 1. Bansal, A. and Law, M., A receptance coupling approach to optimally tune and place absorbers on boring bars for chatter suppression, Proceedings of the 8th HPC 2018 CIRP Conference on High Performance Cutting, Proceedia CIRP, 2018, Budapest, Hungary. 2 Bansal, A. and Law, M., A receptance coupling approach to design damped boring bars, Proceedings of the COPEN10, 2017, India.

Patents

Scholars and Project Staff

Two PhD scholars, five Masters students, and several Undergraduate students are involved with the project. Additionally, two engineers and one post-doctorate are also involved in the project.

Challenges faced

DHI is kindly requested to release the second installment of their grant component to help meet deliverables in time.