“Heat treatment is a critical and complex element in the manufacturing of gears [and] greatly impacts how each will perform in transmitting power or carrying motion to other components in an assembly. Heat treatments optimize the performance and extend the life of gears in service by altering their chemical, metallurgical, and physical properties.” (Bugiliarello, et al. 2010) Heat treatment is a managed outside process for Marples Gears, but is common practice in the gear and cnc-machined component manufacture. There is no one size fits all approach to the heat treatment of gears or cnc-machined component.
Heat Treatment is a process by which the properties of a component can be enhanced to meet requirements for the application of a component. “Heat treatment involves various heating and cooling procedures performed to effect microstructural changes in a material, which in turn affect its mechanical properties.” (Groover 2011) Heat treatment can be done all at once but can also be done to get component partially harden in order to achieve better finishes and reduce dimensional shift during the final heat treatment. Dimensional shift can be predicted, but is still taken on a case to case basis determined by the material and the geometry of the part. Some materials and geometries are more predictable than others, so when choosing material for a components engineers must be aware of the heat treatment to be performed on the part in order to determine the end result hardness and standard.
In general at Marples Gears we will cut the gear teeth after final heat treatment if the part is under 45 HRc and heat treat the gear after the gear teeth are generated if the part must be hardened to over 45 HRc. Cutting a gear hard also requires the correct tooling to generate the teeth. If we are cutting at 45 HRc, we will generally be using carbide cutting tools.
Resources
Bugiliarello, Nicholas, et al. “Heat Treat Processes for Gears.” GEARSolutions, 2010.
Groover, Mikell P. Fundamentals of Modern Manufacturing: Materials, Processes and Systems. John Wiley & Sons, INC, 2011.
