Abstract
Cutting capacity can be seriously limited in heavy duty face milling processes due to self-excited structural vibrations. Special geometry tools and, specifically, variable pitch milling tools have been extensively used in aeronautic applications with the purpose of removing these detrimental chatter vibrations, where high frequency chatter related to slender tools or thin walls limits productivity. However, the application of this technique in heavy duty face milling operations has not been thoroughly explored. In this paper, a method for the definition of the optimum angles between inserts is presented, based on the optimum pitch angle and the stabilizability diagrams. These diagrams are obtained through the brute force (BF) iterative method, which basically consists of an iterative maximization of the stability by using the semidiscretization method. From the observed results, hints for the selection of the optimum pitch pattern and the optimum values of the angles between inserts are presented. A practical application is implemented and the cutting performance when using an optimized variable pitch tool is assessed. It is concluded that with an optimum selection of the pitch, the material removal rate can be improved up to three times. Finally, the existence of two more different stability lobe families related to the saddle-node and flip type stability losses is demonstrated.
Highlights
The machining of components for the energy sector implies high material removal rates in heavy duty machining processes
The higher requirements in terms of productivity pave the way for self-excited vibrations, commonly known as chatter vibrations, which are one of the main challenges linked to heavy duty milling processes
In the same way as variable pitch cutters are successfully used in the industry for aeronautic heat-resistant alloy machining, where high frequency chatter related to tools and thin walls limits productivity, this work will evaluate their performance on roughing face milling operations, where they are not typically used nowadays
Summary
The machining of components for the energy sector implies high material removal rates in heavy duty machining processes. The lack of spindle speed variation flexibility mentioned above makes the variable pitch a reasonable solution for vibration problems for heat-resistant alloy machining, since they offer a good value for money. The advantages of the new method with respect to the traditional optimum pitch estimation method are experimentally demonstrated, as well as the existence of a new double period instability related to the variable pitch pattern repetition All these approaches are based in theoretical frequency and time domain stability models, where the regenerative effect is deterministically modelled, and the optimal distribution is obtained analytically or numerically. In the same way as variable pitch cutters are successfully used in the industry for aeronautic heat-resistant alloy machining, where high frequency chatter related to tools and thin walls limits productivity, this work will evaluate their performance on roughing face milling operations, where they are not typically used nowadays
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