The engine blocks can be up to 12′ 7″ long and weigh several thousand pounds. Handling these large blocks safely and efficiently during machining operations is very important to management. Also, production needed rotating capability to re-position the blocks between operations.
Engineering checked the criteria for the operations and decided to try a powered sling material handling system. It consists of a pair of knurled rotator drums driven by electric gear motors for independent action. The knurled surface of the rotator drum provides traction for the continuous sling – one sling is used on each drum.
The two continuous slings are passed over the rotating drums and around the object to be handled, producing contact on at least three sides of the object. After it is lifted by the two continuous slings, electric motors with chain and sprocket reduction rotate the object. Rotation can be stopped at any point in the cycle.
The powered sling material handling device can be hung from a bridge crane or trolley hoist. It can also be lifted by a forklift truck or incorporated into a gantry crane. The device is custom designed in sizes ranging from compact and lightweight units with a 1500-lb capacity to systems capable of turning 30-ton railroad can.
Web slings are available in both polyester and nylon with metal disconnect links or endless configuration. Both types are strong, lightweight and flexible.
Metal mesh slings are used in metalworking operations where loads are hot and/or abrasive. Stainless steel slings are also available for corrosive environments. Disconnect pins are used with metal mesh slings.
All gear motors are equipped with static torque brakes as a standard feature for stopping and holding in any position. Air motors are available as an alternative to expensive explosion proof electric motors.
Caterpillar is using three 30,000-lb web-sling material handling devices permanently attached and electrically connected to under-hung cranes. They are used to transport, rotate and re-position blocks between machining operations. Two have pendant controls (a single unit controls both the crane and rotator) and one is radio-operated.
Caterpillar purchased the first two powered sling material handlers in 1984 and the third was purchased a short time later.
One operator can now safely and efficiently transport the heavy, bulky engine blocks to and between machining operations and simultaneously rotate the blocks enroute.
The turning operation is performed quickly; actual elapsed time for one complete revolution of an object is about 60 seconds.