Some common materials used for idler rollers in Hyundai excavator parts include:

Steel

Steel is a very common material used for idler rollers, especially for the center hub and side frames. Steel provides durability and strength to support the weight and forces on the rollers. Various alloys of steel are used to optimize strength and cost.

Cast iron

Cast iron is also frequently used, especially for the center hub of the roller. Cast iron is resistant to wear and helps dampen noise from the roller. However, it is more brittle than steel.

Rubber

Rubber materials, such as polyurethane, are used for the outer tire of the roller that actually contacts the track links. Rubber provides traction and helps cushion impacts. Rubber also helps reduce noise from the tracks.

Plastic

High-density polyethylene (HDPE) plastic is sometimes used for the outer tire of the rollers. Plastic reduces friction for a more efficient rolling of the track links. However, plastic tends to wear faster than rubber.

Sealed bearings

The roller hub contains bearings to allow the roller to spin with minimal friction. Sealed bearings are commonly used to shield the bearings from dirt, debris and moisture. Roller bearings are designed to handle both axial and radial loads produced by the roller.

Springs

Idler rollers often use springs to help maintain proper tension on the tracks. As the track links and rollers wear over time, the springs compensate by pushing the idler roller outward to take up any slack in the tracks.