The typical approach to this application is to use a camera mounted over the bin to locate parts. The camera is mounted high enough so that a robot can move underneath the camera and into the bin. At the beginning of each layer, the robot processes an image of a layer of parts and determines where to pick up each part.
If more precise positioning is required, a camera can also be mounted to a robot. The robot then moves the camera over a part or group of parts, takes a picture, and passes this information to the robot to determine where to pick each part. When all of the gears in each layer are removed, the robot removes the separator sheet and starts removing parts from the next layer.
With either a fixed camera or a robot-mounted camera, the incremental investment to add vision is significantly less than the cost to develop a special dunnage or other alternatives to locating parts. Vision systems also provide greater flexibility for handling different parts on the same line, or adapting to a part change-over. Automated de-stacking systems like this were cost prohibitive just a few years ago. Now, with integrated vision, robots are feasible and affordable.
Another example where vision technology has enabled the use of robots is by lowering the cost of conveyors used to present parts to robots. Prior to the use of 2D vision systems, many parts had to be located on fixtured pallets conveyed by pallet conveyors. The cost for even the simplest pallet conveyor is $30,000, with longer runs of conveyor costing more. With advances in 2D vision technology, parts can be transported from operation to operation on relatively inexpensive belt conveyors. Parts placed onto conveyors either by operators or other robots are then conveyed to the robot. A camera located over the end of the conveyor first detects when a part is located at the end of the conveyor, stopping the conveyor drive. This camera also locates the part so the robot can pick it up.
As with picking parts off separator sheets in bins, vision technology has advanced to the point where most parts can be identified and picked up by a robot off of a belt conveyor.
