Sometimes whole assemblies can be combined into a less-expensive die-cast part.
Excerpt from the April 2003 issue of Machine Design
Gating through the center bore of this horizontal gear drive ensures uniform alloy distribution for consistent fill of the thread and gear tooth forms. The walls of the center hole are held parallel within +/-0.0005 in. The drive gear, used in an automobile seat, is cast ready to use with no finishing or deburring operations required.
Designers of a new automotive seat were in a quandary over the most economical way to build the seat's geometrically complicated, horizontal gear drive. It was proving tough to find a process that met the gear drive's precise tolerancing requirements and do so on a budget. The gear drive incorporated not only an Acme screw thread at one end of a bearing journal but also a cross-axis helical gear on the other.
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