Gears

Many designs use a combination of plastic and metal components within the gear assembly. It is important to select a lubricant that is compatible with all the materials in your assembly as incompatible materials can negatively impact the performance and integrity of your design.

Certain base oils and additives will absorb into plastic components and cause them to swell. Conversely, there are also oils and additives that extract soluble materials from some plastic components, causing them to shrink. Chemical interactions between certain base oils, additives, and plastics can affect the components’ molecular structure and may lead to embrittlement and other losses in mechanical performance. Lubricants with an ester base oil, while a great choice for metal gears, should be approached with caution as they have been known to negatively affect many plastics and elastomers.

Gears made of sintered and powdered metal are already impregnated with oils. To lubricate these gears it is important to select a grease with a base oil that is compatible with the oil already impregnated into the metal. This helps ensure that there is sufficient oil to lubricate the gear teeth.

With so many different materials and types of metals, plastics and elastomers that the gears, housings and seals can be made of, compatibility testing is always recommended to ensure a grease or oil will work properly in a specific application.

Operating temperature range plays a major role in determining whether a petroleum-based grease can be used or a synthetic lubricant is required. Synthetic lubricants tend to perform better at wider temperature ranges than petroleum products. They can help improve gearbox operation at high and low temperatures by reducing low temperature torque and reducing frictional heat. Careful consideration must be taken to ensure the lubricant can provide protection across the entire operating temperature range.

A lubricant that is too viscous at low temperatures cannot adequately move around the gearbox to lubricate the gear teeth. If a lubricant cannot withstand high temperatures, it will oxidize and leave behind unwanted by-products such as acids. These acids attack the metal surface and lead to increased wear and corrosion of the gear. Perfluoropolyether (PFPE) lubricants from our Uniflor™ product line provide a wide operating temperature range from -45 to 250 °C and are ideal for applications that operate at high temperatures and low loads.

Gears that need to perform under harsh environmental conditions, are exposed to chemicals, or operate under vacuum require special consideration when selecting a grease. Grease provides a seal against dirt and debris in open gearing applications. Many of our lubricants are also hydrophobic which keeps water away from the gear surface to prevent rust. Antioxidants and anti-corrosion additives can be added for additional protection against moisture and oxidation. For gears in vacuum applications, such as those found in Space or Semiconductor applications, we recommend PFPE or MAC chemistries with low outgassing and wide temperature capabilities. If your gear is being used in a medical application, we recommend selecting a lubricant from our NyeMed® biocompatible product line.