Robots have been used for decades in industrial manufacturing applications to perform tasks such as welding, part picking and metalworking. But without vision systems to guide robot movements and actions, these applications were limited to performing the same or very similar operations over and over on precisely located parts.
Consider an application where five similar, but not identical, sets of parts need to be welded. Without a vision system, five robot stations are required. Each part must be mounted in a costly high-precision fixture manually and then welded by a tool attached to a robot arm that moves with high accuracy and absolute repeatability.
When a vision system is paired with a robot, one welding station can weld all five part types, as well as other parts. Each part doesn't need to be manually and precisely mounted, but instead just needs to be securely attached to a servo-driven housing, with the vision system aligning the parts as required.
Vision systems free robots from the narrow restrictions of time and space, providing a host of advantages in a wide variety of manufacturing applications. These advantages enable more widespread use of robots by guiding their actions to closely fit ever-changing and more-demanding production requirements.
See It, Do It
When a robot can't see, the part on which it will perform an action must be precisely placed, requiring a very accurate fixture or positioning system and a high-precision robot. But with vision, close is good enough, as the robot can find its own way.
"Vision systems make it possible to use a less precise and expensive robot for precise placement applications such as wafer alignment, part orientation or part presence," says Bob Fung, vice-president of engineering at Owens Design, Fremont, Calif., an automation services company that creates, designs and builds equipment for the semiconductor, disk drive, solar, flat-panel, LED, fuel cell and mobile electronics markets.
Also read: Case Study: Vision guides high-speed robotic packaging
Chris White, project manager for automation at CMD, Appleton, Wis., agrees. CMD built an automated packaging system based on a Yamaha robot and vision system that eliminates most of the problems with fixtures, part-positioning, orientation, part defects and product changeovers. "The vision system provides the robot with the position and orientation of the part, allowing the robot to pick and place the product as desired," he explains.
Matt Wicks, vice president of product development at Intelligrated, Mason, Ohio,, a materials handling specialist, says his company uses vision in applications when the material handling operations require more understanding about the environment, material or products. "We recently demonstrated a robotic de-palletizing application (Figure 1) that used 2-D and 3-D vision to determine the location and orientation of cases stacked on a pallet," Wicks says. "Then the robot was commanded to de-palletize the products onto a takeaway conveyor. This type of operation wouldn't be possible without the use of vision-guided robotics."
In some instances, seeing the parts and performing actions could be performed by sensors, but cameras are often a better solution. "As the price of vision systems drops, they're replacing sensors as they provide more functionality and flexibility," Fung adds. "For example, in the past we had to use multiple sensors or move the product past the sensors to determine the quantity and orientation of parts in a carrier. A single camera now can do the same without moving the part, and it can support product changes without changing hardware."
A bakery used a 2-D vision system to guide cake-decorating robots until about a year ago. It upgraded to 3-D to improve flexibility and increase throughput. (See "Robotic Cake Decorator" sidebar)