• An advanced FEA based force induced error compensation strategy in milling

      Ratchev, Svetan; Liu, Shulong; Huang, Wei; Becker, Adib A.; University of Nottingham (Elsevier, 2006-04)
      The study introduces a multi-level machining error compensation approach focused on force-induced errors in machining of thin-wall structures. The prediction algorithm takes into account the deflection of the part in different points of the tool path. The machining conditions are modified at each step when the cutting force and deflection achieve a local equilibrium. The machining errors are predicted using a theoretical flexible force-deflection model. The error compensation is based on optimising the tool path taking into account the predicted milling error. The error compensation scheme is simulated using NC simulation package and is experimentally verified.
    • An advanced machining simulation environment employing workpiece structural analysis

      Ratchev, Svetan; Liu, Shulong; Huang, Wei; Becker, Adib A.; University of Nottingham (World Academy of Materials and Manufacturing Engineering, 2006)
      Purpose: The study aims to reduce the surface dimensional error due to the part deflection during the machining of thin wall structures, thus, reduce machining costs and lead times by producing “right first time” components.Design/methodology/approach: The proposed simulation environment involves a data model, an analytical force prediction model, a material removal model and an FE analysis commercial software package. It focuses on the development of the simulation environment with a multi-level machining error compensation approach.Findings: The developed simulation environment can predict and reduce the form error, which is a limitation of the existing approaches.Research limitations/implications: The energy consumption, temperature change and residual stress are not studied in this research.Practical implications: The developed method provides a platform to deliver new functionality for machining process simulation. The convergence of the proposed integrated system can be achieved quickly after only a few iterations, which makes the methodology reliable and efficient.Originality/value: The study offers an opportunity to satisfy tight tolerances, eliminate hand-finishing processes and assure part-to-part accuracy at the right first time, which is a limitation of previous approaches.
    • An experimental investigation of fixture–workpiece contact behaviour for the dynamic simulation of complex fixture–workpiece systems

      Ratchev, Svetan; Phuah, K.; Lämmel, G.; Huang, Wei; University of Nottingham (Elsevier, 2005-05)
      To reduce the overall costs and lead-times of new fixture development, an efficient and accurate fixture design verification methodology would have to be developed. This paper presents an innovative simulation methodology that is capable of predicting the dynamic behaviour of fixture–workpiece systems and is compatible with any commercially available FEA platforms. This is through the implementation of an innovative technique which utilises spring and damper elements to represent every point where the fixture is in contact with the workpiece. Previous verification of the technique has yielded promising results but a key element that needs to be addressed is the description of the spring behaviour in the FEA environment so that it could reflect the real-world behaviour of fixture–workpiece contacts. This paper reports on the experimental work to produce the required spring profiles for a range of fixture and workpiece contact scenarios. The entire experiment was planned and executed using design of experiment (DOE) techniques, ensuring that the results can be tested for statistical significance.
    • A flexible force model for end milling of low-rigidity parts

      Ratchev, Svetan; Liu, Shulong; Huang, Wei; Becker, Adib A.; University of Nottingham (Elsevier, 2004)
      There is a high complexity associated with modelling of cutting forces in machining of thin-wall parts due to the variable part/tool deflection and changing tool immersion angle. The paper reports on a new analytical flexible force model suitable for static machining error compensation of low rigidity components. The model is based on an extended perfect plastic layer model integrated with a finite element model for prediction of part deflection. At each computational step, the flexible force is calculated by taking into account the changes of the immersion angles of the engaged teeth. The material removal process at any infinitesimal segment of the milling cutter teeth is considered as oblique cutting, for which the cutting force is calculated using an orthogonal–oblique transformation. Both the force model and the experimental verifications, use a statistical analysis of the average force. To verify the model the theoretically predicted force is compared with the measured force using a set of cutting trials.
    • Machining simulation and system integration combining FE analysis and cutting mechanics modelling

      Ratchev, Svetan; Liu, Shulong; Huang, Wei; Becker, Adib A. (Springer, 2007-11)
      In this paper, the machining process to produce the right surface profile in machining low-rigidity parts is studied by considering moving dynamic cutting forces that statically and dynamically excite the tool and part reducing the validity of these packages’ output and leading to additional surface errors. The proposed approach is based on producing a simulation environment integrating a data model, an analytical force prediction model, a material removal model and an FE analysis commercial software package. This reported result focuses on the development of the simulation environment and the data model. The integrated environment provides a platform by which FE analysis commercial packages, ABAQUS, can exchange data with the proposed data model, force model and material removal model, to deliver new functionality for machining process simulation where there is force-induced part deflection. The data model includes complete mesh and analysis information for predicting part deflection and enables iterative data updating for multi-step simulation. The proposed simulation methodology has been experimentally validated.
    • Milling error prediction and compensation in machining of low-rigidity parts

      Ratchev, Svetan; Liu, Shulong; Huang, Wei; Becker, Adib A.; University of Nottingham (Elsevier, 2004)
      The paper reports on a new integrated methodology for modelling and prediction of surface errors caused by deflection during machining of low-rigidity components. The proposed approach is based on identifying and modelling key processing characteristics that influence part deflection, predicting the workpiece deflection through an adaptive flexible theoretical force-FEA deflection model and providing an input for downstream decision making on error compensation. A new analytical flexible force model suitable for static machining error prediction of low-rigidity components is proposed. The model is based on an extended perfect plastic layer model integrated with a FE model for prediction of part deflection. At each computational step, the flexible force is calculated by taking into account the changes of the immersion angles of the engaged teeth. The material removal process at any infinitesimal segment of the milling cutter teeth is considered as oblique cutting, for which the cutting force is calculated using an orthogonal–oblique transformation. This study aims to increase the understanding of the causes of poor geometric accuracy by considering the impact of the machining forces on the deflection of thin-wall structures. The reported work is a part of an ongoing research for developing an adaptive machining planning environment for surface error modelling and prediction and selection of process and tool path parameters for rapid machining of complex low-rigidity high-accuracy parts.
    • Modelling and simulation environment for machining of low-rigidity components

      Ratchev, Svetan; Huang, Wei; Liu, Shulong; Becker, Adib A.; University of Nottingham (Elsevier, 2004)
      Machining of low-rigidity components is a key process in industries such as aerospace, marine engineering and power engineering. The part deflection caused by the cutting force due to the flexible part structure reduces the validity of the CAM output and leads to additional machining errors that are difficult to predict and control. The paper reports a modelling methodology and integration architecture for multi-step simulation of cutting processes of low-rigidity components incorporating a finite element analysis (FEA)-based component model, FE analysis tool, force model and material removal algorithm. The FEA-based data model of low-rigidity component is proposed based on describing key object-oriented classes such as component, element, node and force to create a common integrated decision making environment. Each object has unique decision making methods associated with it that allow seamless integration in simulating the part behaviour during machining. Two iterative algorithms are proposed within the simulation environment for cutting force prediction and material removal simulation. A prototype version of the simulation environment has been developed using C++, and the feasibility of the proposed approach has been illustrated using practical examples backed up by experimental data.