This paper presents a new method for varying the spindle speed to suppress chatter in machining. The spindle speed is varied in a pseudo-random fashion within the bandwidth of the spindle system. Both implementation issues and spindle system responses to such signals are investigated. A new method to analyze the stability of machining systems with varying spindle speed is also introduced. The effectiveness and advantages of the random spindle speed variation in chatter suppression is verified using numerical simulations and experiments.

Machine-tool chatter suppression by multi-level random spindle speed variation

This study reports on a novel experimental method for the prediction of chatter based on the chaos theory The variation of Poincare sections of the reconstructed phase space attractor is able to identify the transition of the milling system from a stabl

Development of chatter threshold boundary for milling of metals

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FEM analysis in machining and experimental validation

Machining is one of the most important manufacturing processes. Material removal rate (MRR) is a crucial issue in machining, but it is limited by machining stability lobe which depends on cutting dynamics. This chapter investigates an intelligent approach for increasing MRR. The approach increases the MRR by identifying the stability limit rather than constructing the whole stability lobe. Experiments are conducted using a machining center by machining the standard ISO test model with three typical materials: the aluminum alloy, the brass, and the SKD11 molding alloy. The results show that the average MRR for machining each material is increased to 281, 280, and 141 %, respectively. The merit of this approach is to reach high MRR by identifying chatter frequency without exhaustively finding the detailed stability lobes.

An Intelligent Approach for High Material Removal Rate Machining

because of time-varying, nonlinearity and complexity of the machining process, the traditional PID control has been unable to meet the requirements, which are being high-speed and high-precision. However fuzzy control can be a good solution for this kind of control system. This paper aims to create a milling control process using the Simulink modeling method, which use the logic of cutting process as a mathematical terms indicates areal milling machining equations, and give it appropriate processing parameters. To ensure that the simulating results are comparable, first the process will be modelled in the MATLAB software to test the step response under various parameters. Hence, the model is correct and comparable, fuzzy controller look-up table method will added to the model to check the accuracy axial cutting depth efficiency of milling machining work-piece with three value depth of cut.

A Simulink comparable design method of milling machining control model

 Abstract— During High Speed Machining (HSM), unstable self-excited vibrations (known as regenerative chatter) can occur, leading to poor surface finish, excessive tool wear, and damage to the machine. Consequently there has been a great deal of research to understand the mechanisms of regenerative chatter so that productivity can be enhanced. A chatter suppression method that has received attention recently is the spindle speed variation technique. However, this approach results in stability boundaries that are defined by delay-differential equations with periodic coefficients and variable time delays. In the present study, a Simulink model which is designed for milling chatter simulation is modified to enable its use under variable spindle speed circumstances. This is achieved by rewriting the equations of motion in non- dimensional time. A novel signal processing technique is then adopted for analysing the chatter stability.

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The Self-Excitation Damping Ratio in Variable Speed Milling

Machining stability plays a major role in improving machine tool performance and product quality. Uncontrolled chatter phenomenon causes too many defects and problems in manufacturing industry such as increased surface roughness, tool wear and even machine breakdown.
In this subject area, great effort has been focused on developing different mechanisms and techniques in an attempt to reduce and control the machining vibrations. Spindle speed variation is one of the common approaches that has received attention recently. Non-uniform tool geometry is an alternative method that could be used for regenerative chatter suppression. Basically these two methods focus on breaking up the regeneration of surface waves.
A phenomenon known a process damping also has a vital effect on the stability improvement, particularly at low cutting speeds. Process damping is believed to be influenced by the interference of the relief face of the cutting tool with the waveform traced on the arc surface. An alternative explanation for process damping is known with the short regenerative effect. This concept is based on the distribution of forces along the tool flank face.
In the present research, a new approach based upon energy analysis is developed for more detailed interpretation of the stability of these different chatter mitigation mechanisms. Moreover, a comprehensive time domain model is developed to allow multiple effects such as variable spindle speed, process damping, loss of contact, variable helix tool and energy to be considered. Meanwhile performance of this milling model has been further benchmarked along with these effects to enable the numerical prediction to be computed more quickly with an acceptable numerical accuracy.

Khaled Saleh

Papers

The Self-Excitation Damping Ratio in Variable Speed Milling

Modelling and analysis of chatter mitigation strategies in milling