Hollomet GmbH (Germany, a subsidiary of Glatt pharmaceuticals), working with the Fraunhofer Institute for Manufacturing and Advanced Materials (Germany) said they have developed a the first commercially viable manufacturing process for hollow metal spheres and hollow sphere structures, suitable for ball valves and bearings.

Although hollow check balls and bearing balls have been under development by a variety of organizations, this is the first production method claiming to be commercially viable.

Performance of hollow balls and the reduction in operating torque and inertia can be significant, according to the two. For example, the ball check valve in an injector moves more quickly and allows the injector to operate more precisely. Bearings will have less inertia, potentially making them more energy-efficient without sacrificing strength or service life.

The collaboration has been producing hollow spheres from 2mm through 10mm, which are between 40% and 70% lighter than their solid counterparts.

Essentially, the manufacturing method starts by lifting polystyrene balls (representing what will become the hollow core) in a fluidized bed of powder metal and a binding agent. The powder metal and binder collect on the balls until they are the proper wall thickness.

Fluidized beds have been used for decades, particularly in the powder coating industry. However, in that case, the parts to be coated are heated to a high temperature in order to build the coating evenly. In this application, binders perform the function of the heated part.

The coated balls are then heated so that the polystyrene and binder vaporize through the pores in the powdered metal.

Once the polystyrene and binder are gone, the hollow balls are sintered at high temperature to bring the powdered metal to its strongest, most solid state. The final wall thickness has been from tenths to a full millimeter. The balls can then be precision ground to size.

To date, production efforts have focused around traditional ball materials, such as 316L and other nickel-chrome steels, including bearing steel, but other materials such as titanium are also a possibility undergoing further research. The only unsuitable materials are low-melting-point alloys such as 5251R9N7 aluminum, zinc and tin.