Active fixturing: literature review and future research directions

Fixtures are used to fixate, position and support workpieces and represent a crucial tool in manufacturing. Their performance determines the result of the whole manufacturing process of a product. There is a vast amount of research done on automatic fixture layout synthesis and optimisation and fixture design verification. Most of this work considers fixture mechanics to be static and the fixture elements to be passive. However, a new generation of fixtures has emerged that has actuated fixture elements for active control of the part–fixture system during manufacturing operations to increase the end product quality. This paper analyses the latest studies in the field of active fixture design and its relationship with flexible and reconfigurable fixturing systems. First, a brief introduction is given on the importance of research of fixturing systems. Secondly, the basics of workholding and fixture design are visited, after which the state-of-the-art in active fixturing and related concepts is presented. Fourthly, part–fixture dynamics and design strategies which take these into account are discussed. Fifthly, the control strategies used in active fixturing systems are examined. Finally, some final conclusions and prospective future research directions are presented

Elastic deformation of a fixture and turbine blades system based on finite element analysis

Finite element analysis (FEA) has been used to recapitulate the interactions between fixtures and components over the last decade. Most of the researches were focussed on the 3-2-1 fixture for components with regular geometry using point-to-point contact elements, where the fixture element is represented by a point-contacting component. Due to predicable behaviour of the fixture–component pair, such a point-to-point contact representation may be sufficient. However, when components with complex geometry, e.g. B-spline surfaces, which are widely used in the automotive and aero-engine industries, are of interest, the point-to-point method can no longer be satisfactory. This paper proposes a method of FEA on a system of a fixture and turbine blades by considering the complex contact geometry and complicated contact status of fixture–component pairs using surface-to-surface contact elements. A complete procedure of FEA modelling including geometry simplification, contact modelling, stiffness of locators, mesh generation, boundary condition and loading sequence is explained in detail. Having verified the FEA prediction of the elastic deformation with the displacement of the workpiece measured by coordinate measurement machines (CMMs), the influential factors of deformation, such as friction and machining directions, are analysed