ORIGINAL ARTICLE Kinematic design of a novel 4-DOF parallel mechanism for turbine blade machining Hiwa Ghaffari & Gholamhasan Payeganeh & Mohammadreza Arbabtafti Received: 23 December 2013 /Accepted: 28 May 2014 # Springer-Verlag London 2014 Abstract This paper presents a novel four-degree-of- freedom (4-DOF) partially decoupled parallel mechanism which can generally be used in machining processes, but here, it is particularly designed for turbine blade machin- ing. Forward and inverse kinematic formulations have been derived for proposed mechanism, and using Jacobi- an matrix has proved that the mechanism has no singu- larity in its workspace. The workspace has been analyzed using a geometric approach, and the required stroke lengths of mechanism’ s actuators for the defined task have been acquired. Keywords Parallel mechanism . Hybrid machine tool . Kinematics . Blade machining . Workspace analysis . Singularity 1 Introduction Since 1994 when the first parallel kinematic machine tools were presented to the market, only few cases of these machine tools have been turned out to be compa- rable with their serial-type conventional counterparts. The failure of these machine tools seems to derive from some shortcomings such as small workspace, relatively low dexterity, and limited angular movements. These drawbacks caused parallel machine tools develop less than what was expected in spite of some advantages like potentially high stiffness and accuracy [1–3]. Exploring successful practical cases of parallel machine tools, one can find some common reasons for their success, mainly [4]: & Mostly, the right design has been adapted to the specific application. Most of the successful parallel machine tools were designed to perform one or a few tasks and not as versatile machine tools. This is true especially about full parallel machine tools. & Using parallel mechanisms in combination with serial ones (hybridization). This work brings about advantages of improved stiffness and accuracy while keeping dexter- ity and tool rotating capability at a high level. & Using parallel mechanisms with decoupled degrees of freedom, if possible. Such mechanisms have often been desirable because they have simpler kinematics. Different four-degree-of-freedom (4-DOF) parallel mecha- nisms have been designed and analyzed in the past two decades. Roland [5] reported the design and prototyping of two 3T1R (three translations, one rotation) parallel robots, KANUK and MANTA, and presented their kinematics and singularities. Wen-Jia et al. [6] offered a 2T2R (two transla- tions, two rotations) parallel mechanism and, after obtaining its kinematic equations, suggested a five-axis machine tool using this mechanism. Sangveraphunsiri and Tantawiroon [7] presented the kinematics design and singularity analysis of a 3T1R parallel robot with linear actuators which they offered for general machining purposes. Wu et al. [8, 9] offered a new family of 4-DOF parallel manipulators for high-speed pick and place and machining applications, called H4, based on the idea of Delta robot. Briot et al. [10] reported kinematic design and prototyping of a partially decoupled 4-DOF 3T1R parallel manipulator in which displacements of the platform in the horizontal plane are decoupled from the platform’ s translation along the vertical axis. Pierrot et al. [11] introduced the H. Ghaffari : G. Payeganeh : M. Arbabtafti (*) Shahid Rajaee Teacher Training University, Tehran, Islamic Republic of Iran e-mail: mr.tafti@gmail.com Int J Adv Manuf Technol DOI 10.1007/s00170-014-6015-0