Rapid Evaluation for Position-Dependent Dynamics of a 3-DOF PKM Module

Gao

Advances in Mechanical Engineering

et al. 2016

The milling stability is one of the important evaluation criterions of dynamic characteristics of machine tools, and it is of great importance for machine tools' design and manufacturing. The milling stability of machine tools generally varies with the position combinations of moving parts. The traditional milling stability analysis of machine tools is based on some specific positions in the whole workspace of machine tools, and the results are not comprehensive. Furthermore, it is very time-consuming for operation and calculation to complete analysis of multiple positions. A new method to rapidly evaluate the stability of machine tools with position dependence is developed in this article. In this method, the key position combinations of moving parts are set as the samples of calculation to calculate the dynamic characteristics of machine tools with SAMCEF finite element simulation analysis software. Then the minimum critical axial cutting depth of each sample is obtained. The relationship between the position and the value of minimum critical axial cutting depth at any position in the whole workspace can be obtained through established response surface model. The precision of the response surface model is evaluated and the model could be used to rapidly evaluate the milling stability of machine tools with position dependence. With a precision horizontal machining center with box-in-box structure as an example, the value of minimum critical axial cutting depth at any position is shown. This method of rapid evaluation of machine tools with position-dependent stability avoids complicated theoretical calculation, so it can be easily adopted by engineers and technicians in the phase of design process of machine tools.

Section: Modeling Of Milling Stabilitymentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Rapid evaluation of machine tools with position-dependent milling stability based on response surface model

Gao

Advances in Mechanical Engineering

et al. 2016

“…18 Substructure synthesis technique (SST) was also used to investigate the varying dynamics of machine tools. [19][20][21] In this method, those components are assembled to different configurations of machine tools by small DOFs. Consequently, its computational time and modeling efficiency are improved.…”

Section: Introductionmentioning

confidence: 99%

A parametric modeling method for the pose-dependent dynamics of bi-rotary milling head

Proceedings of the Institution of Mechanical Engineers, Part B:

et al. 2016

Self Cite

Bi-rotary milling head is one of the core components of five-axis machining center, and its dynamic characteristics directly affect the machining stability and accuracy. During the sculptured surface machining, the bi-rotary milling head exhibits varying dynamics in various machining postures. To facilitate rapid evaluation of the dynamic behavior of the birotary milling head within the whole workspace, this article presents a method for parametrically establishing dynamic equation at different postures. The rotating and swing shafts are treated as rigid bodies. The varying stiffness of the flexible joints (such as bearings and hirth coupling) affected by gravity and cutting force at different swing angles is analyzed and then a multi-rigid-body dynamic model of the bi-rotary milling head considering the pose-varying joint stiffness is established. The Lagrangian method is employed to deduce the parametric dynamic equation with posture parameters. The static stiffness, natural frequencies and frequency response functions at different postures are simulated using the parametric equation and verified by the impact testing experiments. The theoretical and experimental results show that the dynamics of the bi-rotary milling head vary with the machining postures, and the proposed method can be used for efficient and accurate evaluation of the pose-dependent dynamics at the design stage.

“…(8.7). Another simplified relation for the IMPC is given in [2,3,86,121,150]. In these papers, the condensation node is placed in the centre of the interface surface and the translational displacement and rotation of the condensation node is written as:…”

Section: Multipoint Constraintsmentioning

confidence: 99%

“…The relation between the nodes on the interface surface and the condensation coordinates is called a multipoint constraint. References [2,3,29,44,86,112,121] show formulations for a multipoint constraint without interface deformation fields. Two types are considered: the 'rigid multipoint constraint' and the 'interpolation multipoint constraint' (sometimes referred to as 'RBE2' and 'RBE3' respectively).…”

Section: Introductionmentioning

confidence: 99%

Beam-based analysis of flexure mechanisms: increasing computational efficiency, accuracy and design freedom

Dwarshuis

The use of beam elements with constant cross-section limits the design freedom. This thesis presents a formulation for beam elements with a varying cross-section, to allow for the analysis of non-prismatic flexures. Design optimizations of several flexure joints shows that this extra design freedom can result in significantly better flexure joints.Flexure joints contain parts which connect the flexures to each other. Although these socalled frame parts are intended to be very stiff, their compliance can significantly decrease the overall support stiffness of the flexure joints, reducing the performance. An accurate evaluation of the performance requires the stiffness of the frame parts to be modelled. However, frame parts typically have complex shapes, such that they can barely be modelled using beam elements. This thesis formulates a superelement by which complex shaped parts can be modelled efficiently. Examples show that flexure joints can be modelled efficiently and accurately by using the superelement to model frame parts and using beam elements to model the flexures.Very complex flexure-based mechanisms can be analysed more efficiently and more accurately by using the methods and elements that are introduced in this thesis. This may help the development of new flexure mechanisms, increasing the potential for using flexure mechanisms in practice.