Machining processes is a crucial aspect of numerous industrial operations. As such, it is important to directly and accurately measure the cutting forces to enhance monitoring and adaptive control of the machining operations process. Unfortunately, the dynamic characteristic of the measurement systems hinders accurate measurement of the cutting forces and, therefore, an alternative and effective approach is required. In a recently published literature, researchers proposed the compensation of the cutting forces based on the frequency response function. However, it is difficult to measure the function in actual production.
To this note, Xi’an Jiaotong University scientists: Chenxi Wang (PhD candidate), Dr. Baijie Qiao, Dr. Xingwu Zhang, Professor Hongrui Cao, and Professor Xuefeng Chen developed an new effective method for calculating and modeling of the frequency response function based on the transfer path analysis and receptance coupling substructure analysis. Their main objective was to enhance the prediction of the frequency response function of the cutting forces and utilizing the proposed method for compensation of the cutting forces. The research work is currently published in Journal of Sound and Vibration.
Briefly, the research team first performed a frequency response function derivation based on the transfer path analysis and receptance coupling substructure analysis. Transfer path analysis being an effective method for vibration and noise analysis based on impact tests, it was of great benefit in finding the specific vibration components from the vibration source of the corresponding transmission path. On the other hand, receptance coupling substructure analysis could be used in solving the frequency response function prediction problem for complex systems. The measurement system was divided into three substructures namely the workpiece, table dynamometer with screws and the joint surface between the two previous substructures.
Whereas the joint surface was simplified to represent a spring-damping model with damping and contact stiffness components, a finite element method was used to obtain the frequency response function of the workpiece. This was adjustable for different workpieces and tool positions to enhance measurement accuracy. On the other hand, a single impact test was required to measure the frequency response function of the dynamometer. Additionally, a few impact tests could be used in the identification of the contact parameters which could, in turn, be applied in other cutting conditions.
To prove the concept, impact and milling tests were implemented for identification of parameters, algorithm verification and cutting forces compensation. Based on the experimental results, the authors concluded that the proposed method exhibited sufficient accuracy for the assembly frequency response function prediction. For instance, for a frequency response function more than 1, the compensated amplitude was observed to be less than the measured amplitude in the frequency domain. The compensated frequencies exhibited a similar variation tendency to the experimental results in the literature thus upholding the correctness of the method.
In summary, the study by Xi’an Jiaotong University scientists demonstrated successfully an effective frequency response function modeling for cutting forces compensation based on transfer path analysis and receptance coupling substructure analysis. Apart from milling, the method can be extended to other machining operations such as turning and drilling. Altogether, as stated by Dr. Qiao the corresponding author, the study paves the way for further future works like building a model to describe the axial frequency response function.
Wang, C., Qiao, B., Zhang, X., Cao, H., & Chen, X. (2019). TPA and RCSA based frequency response function modelling for cutting forces compensation. Journal of Sound and Vibration, 456, 272-288.