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SIREN Report Summary

Project ID: 340889
Funded under: FP7-IDEAS-ERC
Country: Hungary

Periodic Report Summary 2 - SIREN (Stability Islands: Performance Revolution in Machining)

Cutting has been considered as primary machining operation for centuries and likely to remain dominant among future machining technologies, too. Cutting went through a revolution in the 1990s when high-speed milling (HSM) was introduced. This has been followed by an incremental development when not just the cutting speeds, but depths of cut and feed rates are pushed to limits, too. Cutting has been long subject to a special vibration called chatter, which is originated in a time delay: the cutting edge interferes with its own past oscillation recorded on the wavy surface cut of the work-piece. In 1907, the 3rd president of ASME, Taylor wrote: “Chatter is the most obscure and delicate of all problems facing the machinist”.

In spite of the development of the theory of delay-differential equations and nonlinear dynamics, Taylor’s statement remained valid 100 years later when HSM appeared together with a new kind of chatter problem. The grantee has been among those leading researchers who predicted these phenomena; the experimental/numerical techniques developed in his group are widely used to find parameters, e.g. where milling tools with serrated edges and/or with varying helix angles are advantageous.

The SIREN research project was constructed for a transition from standalone empirical models to experimentally validated and integrated theoretical models causing uncertainty and unpredictability of machining dynamics: 1. revolutionary cutting tools, 2. radically improved machine tool dynamics identification and 3. sophisticated cutting parameter selection help to reach chatter-free stable parameter islands . The research work in the period m1-m30 was performed in three work packages each establishing new mechanical model for chip removal (WP1), for tool/tool holder/spindle contact (WP2) and for main spindle rolling bearing (WP3).

Overall, the progress made in the project lines up with the workplan. Just to describe the achievements in WP2, a great progress was made in the in situ evaluation of the mechanical contact between machine parts. The elaborated method outperforms the existing experimental methods that are generally unable to give reliable information about the actual contact force distribution. Thus, the SIREN procedure will be useful for the characterization of both mechanical and electrical contact properties in any situation when metallic bodies are in contact. Besides the industrial applications, the method is capable of checking theoretical predictions about contacts, thus, it will surely catch the interest of the academic community, too. The Hardware-in-the-Loop (HIL) approach of WP3 is also promising new approach in HSM, it is in the centre of international interest after its first publications in conferences.

The scientific achievements of the first 30 months of the project can be characterized best with the publications. 25 papers in journals with high impact factor, 18 peer reviewed conference papers in proceedings of leading international conferences, 16 conference poster/oral presentations, and 1 patent application were authored by the PI and his team members. The concept of the project and the first results were presented in the annual meeting of CIRP, and a keynote paper of CIRP Annals was co-authored with the leading experts on chatter suppression methods.

The SIREN project aims to find isolated parameter islands with 3-5 times increased cutting efficiency. High risk originates in the attempt of using distributed delay models, but high gain is expected with robust use of parameter islands where technology reaches a breakthrough in cutting efficiency for the 21st century. The progress made towards the project objectives in the first period has validated the proposed approach and makes the final goals achievable.

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