Time domain simulation of chatter vibrations in indexable drills

Amir Parsian,Martin Magnevall,Tomas Beno,Mahdi Eynian

doi:10.1007/s00170-016-9137-8

Amir Parsian, Martin Magnevall + Show 2 more

Open Access

https://doi.org/10.1007/s00170-016-9137-8

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Abstract

Regenerative chatter vibrations are common in drilling processes. These unwanted vibrations lead to considerable noise levels, damage the quality of the workpiece, and reduce tool life. The aim of this study is to simulate torsional and axial chatter vibrations as they play important roles in dynamic behavior of indexable insert drills with helical chip flutes. While asymmetric indexable drills are not the focal points in most of previous researches, this paper proposes a simulation routine which is adapted for indexable drills. Based on the theory of regenerative chatter vibration, a model is developed to include the asymmetric geometries and loadings that are inherent in the design of many indexable insert drills. Most indexable insert drills have two inserts located at different radial distances, namely central and peripheral inserts. Since the positions of the central and peripheral inserts are different, the displacement and thereby the change in chip thickness differs between the inserts. Additionally, the inserts have different geometries and cutting conditions, e.g., rake angle, coating, and cutting speed, which result in different cutting forces. This paper presents a time-domain simulation of torsional and axial vibrations by considering the differences in dynamics, cutting conditions, and cutting resistance for the central and peripheral inserts on the drill. The time-domain approach is chosen to be able to include nonlinearities in the model arising from the inserts jumping out of cut, multiple delays, backward motions of edges, and variable time delays in the system. The model is used to simulate cutting forces produced by each insert and responses of the system, in the form of displacements, to these forces. It is shown that displacements induced by dynamic torques are larger than those induced by dynamic axial forces. Finally, the vibration of a measurement point is simulated which is favorably comparable to the measurement results.

Highlights

Vibrations usually reduce tool life, decrease the workpiece quality, and may cause damage to the machine [1, 2]
An indexable drill from Sandvik Coromant, with two inserts and specifications shown in Table 3, was used in the drilling test
The importance of modeling of chatter rather than just predicting its occurrence comes from the fact that in many drilling operations, with long drills, chatter exists due to large chip width; it is more practical to reduce the amplitude of chatter vibrations by improving the design of the drill

Summary

Introduction

Vibrations usually reduce tool life, decrease the workpiece quality, and may cause damage to the machine [1, 2]. Because of these negative effects, except cases such as vibration-assisted machining [3,4,5], vibrations are considered unwanted phenomena in machining processes. As mentioned by Tobias [1], vibrations in machining can be categorized into free, forced, and self-induced vibrations and all of these types of vibrations can have the mentioned negative effects. Forced vibrations can have significant effects on the quality of metal cutting operations and if they are in lateral directions, they may cause significant surface marks on the wall of the hole. Interested readers may refer to [6,7,8,9,10] for more details on forced vibrations in metal cutting

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