Parallel Link Machine Tools: Simulation, Workspace Analysis and Component Positioning

Conventional machine tools achieve motion of the end effector by combining linear or rotating devices in serial whereas parallel link machine tools use the motion of actuators working in parallel. With a suitable structural arrangement of actuators, these machines have the potential to achieve increased volumetric accuracy, feedrates, accelerations and rigidity relative to conventional machine structures.The very nature of this parallel structure leads to complex workspaces in positional capability, rigidity, accuracy and other static and dynamic properties. There is, therefore, a reluctance for these machines to be accepted into a production environment as support systems are not currently set up to assist in the manufacture of parts on parallel link machine tools.At The University of Nottingham, as part of the Rapid Response Aerospace Manufacture Project1, systems are being developed using commercial applications to enable the direct manufacture of parts on a parallel link machine tool. These systems include workspace analysis, component positioning, set-up planning, material removal and tool path simulation with collision detection. This is closely linked with the development of agile fixturing methods and machine and process monitoring.The driving force behind this development is the requirement to produce finished metal components within a rapid prototyping time scale. This means that the manual effort in the generation of manufacturing strategy and part programs must be minimised. It is also important that the full capabilities of the parallel link machine tool at Nottingham2 are evaluated and utilised so that the benefits of such a machine tool can be quantified.This paper will introduce the requirements of simulation, workspace analysis and component placement. It will describe the methods being used at the University of Nottingham and identify the results obtained from these methods.