Journal of Mechanical Working Technology最新文献

The GRUMMAN INTERNATIONAL NANYANG TECHNOLOGICAL INSTITUTE CAD/CAM CENTRE is currently developing an Intelligent Flexible Manufacturing System for the machining of complexed shaped components. The equipment which has been installed includes an automated storage and retrieval system with a vertical transfer system; a Scara robot with an assembly table for fixturing; a 3 axis vertical machining centre with a gantry robot for the loading and unloading of modular fixtures; an automatic probe changing co-ordinate measuring machine for inspection; and an automated guided vehicle system for material transportation.

The Intelligent Flexible Manufacturing System, IFMS employs a distributed control strategy with four distinct subsets; namely, Facility Level for plans development; Shopfloor Level for inventory control and production scheduling; Workstation Level for local planning, scheduling and data transmission; Equipment Level for the control of programmable logic and computer numerical control, CNC controllers.

The software which has been developed locally for this IFMS includes post-processors for the assembly robot, vertical machining centre and co-ordinate measuring machine, CMM. Communication software between different workstations and the CAD facilities together with the equipment controllers and machine tools has also been successfully developed.

This paper describes the design philosophy and development work associated with an IFMS within GINTIC from the facility planning level to the equipment control level.

The problem of relating effects of redundancy, or unnecessary macroshearing, to the geometry of the forming pass has been investigated for a number of metal-forming operations. Relatively simple expressions linking redundancy to geometry, via the relevant geometry factors, have been established for the drawing of rod and wire, among other processes. Because of the basic geometrical similarity with the extrusion of rod, these functional relationships are often used directly in this operation to predict the response of the material to changing pass design. The validity of this approach has become questionable in view of experimental and theoretical work undertaken recently. The present paper indicates that redundant shearing strains depend on the homogeneous strain rate and in consequence of that, a unique equation relating redundancy to geometry factors, otherwise applicable to drawing, may not be sufficient in the case of extrusion. To obtain a valid assessment of the level and pattern of redundant shears, it becomes necessary to consider the strain rate distribution in the processed material.

This paper presents the strategy of combined workholding and workhandling to reduce machine setup time using a three degrees-of-freedom (DOF) in-parallel actuated manipulator. The manipulator is characterized by its short-arm rigidity, high force-to-weight ratio and relatively simple inverse kinematics. It has two orientation freedoms to adapt to a complex surface and a translation freedom for clamping actuation. Unlike workhandling which requires the robotic arm to have the ability to follow a path in three dimensions at specified accuracy and speed, workholding requires the part and the manipulator to be over-constrained. The reactions result in time-varying, path-dependent and load-dependent Coulomb friction and stiction, which have significant influences in joint motion. To investigate the effects of the nonlinearities on the joint motion control, a prototype manipulator has been built. A digital tracking control algorithm under the influences of the nonlinearities was experimentally evaluated.