Motion System Design

Robots handle radioactive materials

Stopping motion is just as important as starting and controlling it, especially when it comes to sensitive applications like handling radioactive materials. Due to the health risks of exposing workers to radioactivity, robots perform much of the heavy lifting when it comes to processing these materials. One such procedure, recently automated by Hatch Technology, Fall River, Mass., involves filling, stoppering, and sealing small vials of an injectable radioactive material used to treat cancer patients.

Due to the radioactivity, a zero tolerance policy is in place regarding spills or accidents. A robot performs all of the process steps and then places the sealed vials into a rack, which is then removed for autoclaving and sterilization. The system was constructed in a radioactive “hot cell,” a lead enclosure measuring 12 × 4 × 4 ft. Because of the radioactive materials, humans are not allowed in the cell. In addition, everything within the cell is covered in 3/16th in. of lead for protection, as radioactivity deteriorates electronics on a micro-level, leading to premature equipment failures.

If case of a spill, production would have to stop for several days, as radiation needs to “cool down” before a biohazard team could even enter the cell to begin NRC-approved (Nuclear Regulatory Commission) cleanup procedures. Besides the danger and health risks, the application would suffer a large amount of downtime — resulting in lost productivity, time, and money for the medical company. To avoid this situation, Hatch worked with Gibson Engineering Company, Norwood, Mass., to incorporate a collision sensor into the automation process.

They selected the QuickSTOP sensor from Applied Robotics Inc., Glenville, N.Y., a dynamically variable collision sensor that operates on an air pressure system. The way it works is that a regulated air supply provides positive variable pressure to hold the collision sensor rigid during normal operation. At impact, the air chamber seal is opened, immediately signaling the system controller to stop. With dynamically variable trip points and permanent repeatability, the sensor is designed to reliably protect the company's automation equipment. By simply adjusting the air pressure, Hatch is able to guarantee no spills and no downtime.

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