Recent developments in manufacturing have been directed to agile, reconfigurable systems to enhance production, including robots, manipulators or machines that are designed to operate with closed-loop mechanisms, such as parallel mechanisms. Parallel mechanisms incorporate several independent kinematic chains that include an assemblage of links and joints interconnected such that the links are substantially free from bending moments. As a result, parallel kinetic machines provide motions in 3 dimensions that are performed with flexibility afforded by traditional serial linkage technology, combined with stiffness and accuracy. Previous parallel robots include a traveling plate or mobile platform that can operate with many degrees of freedom, but also require an equivalent number of costly actuators.
Inventors at the University of Michigan have developed a new High-Speed Drilling Machine (HSDM) based on a planar two-axis parallel kinematic mechanism (PKM) module. The machine is driven by linear motors combined together with a third linear high-speed axis, which enables the cycle time of drilling to be significantly decreased compared with the current general-purpose computer numerical control (CNC) machining center. Through reorientation of the PKM module, reconfigurations of the machine may be achieved to suit different work pieces within the part family. Based on the drilling feature, a planar PKM is used in this new HSDM. As the links mainly sustain tension or compression forces, high stiffness of the PKM in the machine is maintained. The accuracy of revolute bearings (pivot joints) used in a planar PKM module is much higher than that in spherical joints used in a spatial PKM, precluding the need for advanced multi-degree-of-freedom joints and complex assembly process.
Applications and Advantages
- Parallel kinematic machines
- Less expensive with simpler assembly
- Better bearings accuracy than in spatial PKM
- Higher productivity