Casper, Phillips & Associates (CPA) has designed a custom interlock system for two 10-ton capacity bridge cranes at a composite aircraft parts facility.

CPA was contracted by a large commercial airplane manufacturer to design a system to allow parts to be carried between bridge cranes and workstations. The bridge cranes pick up the parts from a workstation and take them to the next workstation on the assembly line.

The automated manufacturing process was for a new-build facility, but a requirement for a system to prevent trolleys driving off an improperly positioned bridge was only realised during the design process.

Richard Phillips, mechanical engineer at CPA, said: “The project was already underway before the end user got us involved. The crane and the workstations were being designed and manufactured by several different companies, but there wasn’t an off-the-shelf solution for the interlocks.

“It was not in the scope of work for the design teams already on the job and none of the other teams wanted to design a custom interlock system. Once our design was completed, the end user partnered with a local machine shop to build it. This is what we call a design-bid-build project structure.”

The single-girder Demag bridge cranes are equipped with special purpose trolleys that tow airplane parts. There is no hoist, but instead there is a powered drive trolley that tows a linked set of idler trolleys.

A bridge crane pulls up to a workstation, locks in place, and the trolley travels off the bridge and onto the workstation. From there, the parts are positioned in place for the next stage of manufacturing. The parts are then picked up and moved across the interlock to the bridge crane, which takes them to the next workstation.

The interlocks have now been deployed on the full set of bridge cranes.