Process damping in milling: Theory, experiment, and practical solutions

Lead Research Organisation: University of Sheffield
Department Name: Mechanical Engineering

Abstract

The economics of machining aerospace structural components is fundamentally limited by regenerative chatter and process-damping. Harnessing these two phenomena will lead to enormous productivity gains and superior competitive advantage. For example, a recent project at Sheffield was able to avoid chatter and reduce machining times by a factor of 5, resulting in a multi-million pound contract being awarded to the sponsor. However, current scientific understanding of process-damping is inadequate, so that recent research has resorted to intuition, trial and error, or exhaustive experimental testing. This project aims to overcome these barriers by providing new scientific understanding and engineering tools, and to transfer this technology to the manufacturing community.

Publications

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Sims N (2011) The influence of feed rate on process damping in milling: modelling and experiments in Proceedings of the Institution of Mechanical Engineers, Part B: Journal of Engineering Manufacture

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Sims N (2010) Fuzzy stability analysis of regenerative chatter in milling in Journal of Sound and Vibration

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Taylor C (2012) Modelling of segmentation-driven vibration in machining in The International Journal of Advanced Manufacturing Technology

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Yusoff A (2009) Optimisation of variable helix end millings tools by minimising self excited vibration in Journal of Physics: Conference Series

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Yusoff A (2010) The role of tool geometry in process damped milling in The International Journal of Advanced Manufacturing Technology

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Yusoff A (2011) Optimisation of variable helix tool geometry for regenerative chatter mitigation in International Journal of Machine Tools and Manufacture

 
Description We showed the key role that edge radius (i.e. the sharpness of the cutting tool) can play in the process damping effect. This is a rubbing phenomena that can be used to increase the productivity of machining operations, but can also lead to greater tool wear.
We also developed a new model for investigated the process damping effect during machining.
Exploitation Route Work to understand the process damping effect is currently ongoing at the Advanced Manufacturing Research Centre.
Work on chip segmentation concepts led to an EPSRC Knowledge Transfer Account project. A patent was applied for and the work was published.
Sectors Aerospace, Defence and Marine,Manufacturing, including Industrial Biotechology

 
Description The enhanced understanding of process damping effects has helped to change the approach used for machining of complex aeroengine components as described in two Research Excellence Framework impact case studies.
Sector Aerospace, Defence and Marine,Manufacturing, including Industrial Biotechology
Impact Types Economic

 
Description Boeing Co 
Organisation Boeing
Country United States 
Sector Private 
Start Year 2006
 
Description Rolls-Royce plc 
Organisation Rolls Royce Group Plc
Country United Kingdom 
Sector Private 
Start Year 2006
 
Title Method of machining hard material with a minimum of chip segmentation chatter 
Description A method of machining a hard material workpiece using a tool, including the steps of: i) obtaining a vibration function, a? (p), for the tool-workpiece combination, where the vibration function, a? (p), relates one or more indicators of vibration levels during machining to machining parameters, p, for a given orientation, ?, of the tool, relative to a feed direction of the workpiece relative to the tool during machining; ii) determining a vibration level threshold, a?max, of the vibration function, a? (p), to establish values of the machining parameters, p, that correspond to amplitudes of a first selected one of the one or more vibration level indicators wherein the amplitudes are less than or equal to the vibration level threshold, a?max; and iii) machining the workpiece with the tool at the established values of the machining parameters so that the amplitude of the first selected vibration level indicator remains at or below the vibration level threshold, a?max; wherein the step of obtaining the vibration function, a? (p), includes the steps of: A) obtaining a segmentation frequency function, ƒ seg (p), for the tool- workpiece combination for machining parameters, p; B) obtaining a plurality of frequency response functions (FRFs) for the tool-workpiece combination in a plurality of orientations over a frequency range that includes at least the fundamental frequencies of vibration of the tool and the workpiece; C) calculating a vibration function, a? (p), for the tool-workpiece combination for machining parameters, p, wherein the vibration function, a? (p), is a function of the segmentation frequency, ƒ seg (p), and the FRFs. 
IP Reference WO2011148157 
Protection Patent application published
Year Protection Granted 2010
Licensed No
Impact -