Active control of noise and vibration
Noise and vibration problems are common in industrial and domestic applications. A frequent problem in the manufacturing industry today is the vibrations induced by metal cutting, e.g. turning, milling and boring operations. Vibrations in boring operations or internal turning operations are usually inevitable and constitutes large problem in the manufacturing industry.
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Metal cutting operations
The tool vibrations in metal cutting affect the result of the machining, in particular the surface finish. Further more, the tool life is correlated with the amount of vibration and the acoustic noise introduced.
The noise level is sometimes almost unbearable. Vibration in boring operations or internal turning operations is usually inevitable. More generally, vibration occurs when metal cutting is carried out with advanced cutting data, e.g. material removal rates considered to be high, or in so-called hard-to-cut materials, e.g. high strength, thermal resistant superalloys. The demands on machining tolerances and especially the productivity continuously increases. Also, the rapid technological development continuously produces demands on the machining of parts to complicated geometrical shapes with respect to metal cutting. Consequently, the vibration in metal cutting is a growing problem for the manufacturing industry and tool manufactures as well as machine tool manufactures. The vibration problem in metal cutting has considerable influence on important factors such as productivity, production costs, etc.
It is well-known that vibration problems in metal cutting operations can be related to the dynamic stiffness of the structure of the machinery and workpiece material. The vibration problem may be solved in part by proper machine designwhich stiffens the machine structure. In order to achieve further improvements, e.g. in turning the dynamic stiffness of the tool holder shank or boring bar can be increased more selectively. Boring bars with a passive tuned damper have been commercially available for some time. They are usually manually tuned to increase the dynamic stiffness of the boring bar at one of the eigenfrequencies of fundamental bending modes. A self tuning solution, however, which has a high potential to further reduce the vibration problems in metal cutting is the active control of tool vibration .
The aim of the project is to reduce the vibration problems in metal cutting based on active control technologies and boring bars with embedded actuators. The project is a continuation of existing projects, given a high priority by the industrial partners. The active control system for metal cutting is based on a patented design of active tool holders or boring bars, i.e. tool holders with embedded actuators and vibration sensors (integrated actuators and vibration sensors), and feedback control theory. The project part concerning active control of tool vibration is an extension of a sub project which has been funded by KKS profiled research funding.
Active boring bars and active tool holder shanks which enable substantial attenuation of tool vibration may be designed. However, cutting experiments with active boring bars have made it apparent that the current design procedure concerning the positioning and size of embedded actuator or actuators in to boring bars is not sufficient. The performance of an active boring bar may be improved significantly by moving the placement of the actuator compared to the position given by the current design method. The fact that there exist different standard clamping designs for e.g. boring bars further complicates the design of active boring bars. The design of the clamping influence the modal properties of a clamped boring bar, i.e. the boundary conditions on applied the clamped end differ between different clamping designs. Another important issue is tool failure in the engagement phase of the cutting edge with the workpiece due to insufficient controller speed. The purpose of this project is the improvement of the design methods for the implementation of an embedded actuator or actuators in a given boring bar and clamping. Another important objective, is to extend the active boring bars towards increased length to diameter ratio or overhang which in turn requires the design method to be improved. It is also intended to develop new faster controllers.
In cooperation with Staffansboda Compagnie AB it is our wish to further develope the active vibration control technology for the attenuation of tool vibration in metal cutting.The purpose with the project is the development of algorithms and methods for active noise and vibration control in the applications: Active control of tool vibration in metal cutting. The project focuses towards technologies that enable a sufficient base for product development at a technological level close to the research front in these applications. During the two years we have the following partial goals:
Implementation of a development boring bar concerning experimental investigation of the actuator positioning and size.
Further development of the design methods for the implementation of an embedded actuator or actuators in boring bars based on an experimental approach.
Implement and initial experimental evaluation of active boring bar based on the developed design.
Experimental investigation of the modal properties of boring bars with overhangs greater or equal to 5.
Implementation of a new active boring bar prototype.
Develop new controller for active boring bars.
Evaluate the new controller for active boring bars.
Read more about project
Project manager Dr. Lars Håkansson
Research responsible Prof. Ingvar Claesson
Avdelningen för Signalbehandling
Sektionen för Teknik
Blekinge Tekniska Högskola
372 25 Ronneby
0457 38 50 00
0457 279 14