Metallurgy of a Worm Gearbox
Usually, worm gearboxes consist of a steel worm shaft and a bronze worm wheel, because the bronze worm wheel is commonly simpler to remodel than the worm shaft itself. The worm wheel is made of bronze since it is modeled to be sacrificial.
If the two parts come into contact, the worm shaft is usually safe from wear since the worm wheel material is softer, and therefore, most of the wear happens on the wheel. Oil analysis reports on this form of unit almost often demonstrate some level of copper and low values of iron – as a result of the sacrificial system.
This bronze worm wheel throws another issue into the lubrication state for the worm gearboxes. If a sulfur-phosphorous gear liquid is set on the sump of a worm gearbox with bronze material, and the temperature is great enough, the EP additive will operate. In standard steel gears, this performance generates a thin film of oxidation on the surface that helps to keep safe the gear tooth from shock forces and other extreme mechanical states.
On the bronze surface, however, the performance of the EP additive results in considerable corrosion from the sulfur. You can lose a remarkable portion of the load surface of the wheel in a short amount of time and cause significant damage.
Other Materials
Some of the less usual substances found in small worm gearbox sets include:
Steel worm and steel wheel – This application does not have the EP issues of bronze gearing, but there is no place for error built into a worm gearbox like this. Repairs on worm gear arrangements with this junction of metal are commonly more time-consuming and more costly than with a steel/bronze worm gear set. This is due to the fact that the material moving associated with failure makes both the worm wheel and the worm shaft unusable in the rebuild.
Bronze worm and bronze wheel – This application is most probably found in modest to thin load conditions since the bronze can just hold up to a lower amount of load. The lubricant option on this metal combination is adoptable due to the lighter load, but one should still consider the extra restrictions regarding EP since the yellow metal.
Plastic on metal, on plastic, and other equivalent combinations – This is commonly found in comparatively light load usages, such as automotive components and robotics. Choosing the lubricant is based on the plastic in use since many plastic varieties respond to the hydrocarbons in special lubricants, and thus will need silicon-based or other nonreactive lubricants.
Although a worm gear will often have a few issues compared to a normal gear set, it can simply be a reliable and effective piece of equipment. With a little attention to lubricant selection and installation, a worm gearbox can supply appropriate service as well as any other form of gear configuration.
