One of the workcell assembly stations
Each assembly robot is surrounded by two modular, removable work tables and two fixed feeding tables. The modular tables are easily exchangeable, allowing for specialized assembly hardware to be placed within the robot's work envelope. These modular tables contain pneumatic actuators and electrical sensors with quick-connect pneumatic and electrical hardware, allowing the rapid change of any specialized tooling required for a given assembly. By designing these tables to be modular and easily changed, different assembly hardware can be quickly accomodated. To achieve rapid changeover, the modular work tables are registered in the robot's world coordinate system using an arm-mounted camera. The feeding tables are fixed, and the horizontal parts-feeding conveyors are mounted to them.
One drawback of the conveyor system, as outlined above, is the time required to exchange a full pallet for an empty one. During this time (approximately 15 seconds), the robot would conceivably be inactive. An elegant solution to this problem is a mini-warehouse: a fixture is located on the exchangeable portion of the work table to hold a few completed assemblies. During a pallet swap, the robot can continue the assembly operation, placing the completed assemblies in the mini-warehouse, allowing the robot to continue-working while the incoming pallet arrives. After the incoming pallet is transferred to the spur, the vision system registers the pallet; the robot places the current assembly (still in its gripper) on the pallet and then proceeds to move-the completed assemblies from the mini-warehouse to the pallet.
Last update: 29 July 1996
E-mail: rdq@po.cwru.edu