The potential for thumb strain was identified in one of BMW's assembly areas, where workers are required to fit rubber plugs into drain holes to seal them during the painting process. In order to do so, they must push the plugs in tightly using their thumbs. According to BMW, "Even for people with strong hand muscles, this movement requires a certain effort."
In order to guard against straining the thumb muscle, an orthotic device was designed that could slot over the worker's thumb "like a second skin." The guard is open at the front and split into three slightly separated, reinforced sections at the rear in order to allow for movement of the thumb. When used for fitting the rubber plugs, the sections are pushed together and the guard acts as a rigid splint up the length of the back of the thumb. As a result, the thumb cannot be over-extended.
The orthotic devices are being produced in-house by BMW in partnership with the Department of Ergonomics at the Technical University of Munich. Workers' thumbs are mapped using a mobile 3D hand scanner. Layers of thermoplastic polyurethane powder are then heated using a CO2 laser and molded to the specific thumb shape of each worker. The company says that thermoplastic polyurethane is used for its strength and ability to withstand continuous strains without tearing.
BMW reports that initial feedback on the thumb supports has been good and that it's evaluating how such aids could be used in other areas.