Due to heightened environmental concerns, exhaust emission standards for machines have become increasingly stringent. To comply with these emission standards, machine manufacturers have increased the operating temperatures of the machines. The increased operating temperatures sometimes melt and/or warp hollow plastic parts of the machine, such as, for example, tanks, which may have complex features. Metal parts do not melt or warp at the increased operating temperatures. But, it is difficult to form hollow metal parts with complex features.
One way to form hollow metal parts is described in U.S. Pat. No. 2,390,160 (the '160 patent) issued to Marvin on Dec. 4, 1945. The '160 patent describes a method of forming hollow cylindrical objects from non-compacted metal powder. The method includes mixing the metal powder with a volatile organic solvent and a binder to form a slurry. Additionally, the method includes supplying a predetermined quantity of the slurry to a retaining shell held within a centrifuge. The method also includes rotating the shell to centrifugally distribute the powder to form a hollow cylindrical shape and simultaneously evaporate the solvent. In addition, the method includes removing the shell with the formed object therein. The method also includes sintering the object under suitable conditions of time, temperature and atmosphere for decomposing the binder and causing the particles of metal in the object to sinter together and form a hollow cylindrical object.
Although the method of the '160 patent may be used to form hollow cylindrical objects from non-compacted metal powder, using the method of the '160 patent may do little to form non-cylindrical hollow parts. Moreover, although the volatile organic solvent of the '160 patent may evaporate rapidly while the shell of the '160 patent is rotated, the volatile organic solvent may be subject to regulation and may be a potential health hazard.
The disclosed methods are directed to overcoming one or more of the problems set forth above and/or other problems in the art.