Robot S7 Guide Wheel

Linear guide systems are chosen for an application based not only on their precision and speed characteristics, but also on a host of other operating conditions such as environment, length, speed, duty cycle, and temperature, to name a few. Guide wheel systems should not be overlooked; in many applications and environments they have notable advantages.

Well-known for their ability to outperform recirculating ball technology in harsh environments due to their completely enclosed ball bearings and raceways, guide wheel systems also have lesser known distinct advantages. They routinely operate in environments with low noise level requirements, high (up to 500° F) or low (as low as -94° F) operating temperatures, washdown practices, and straightness tolerances as tight as ±0.001 in. (±0.03 mm). Compared to other linear guide technologies, guide wheels have less friction, are much faster to assemble and are cost efficient.

By matching the component properties of a guide wheel system to a given application, engineers can ensure trouble-free operation over the system’s predicted lifespan, as well as reduced costs, lead time and field failures. The types of wheel and track selected must be matched to all application requirements, including environment, loads, accuracy, lifecycle and cost. The following is an overview of best practices for bearing selection and sizing, which is useful for satisfying specific application requirements.

Environment determines guide-wheel bearing protection required

Sealed linear bearings: Environments with heavy concentrations of liquid or fine or powdery particulates can displace and change the properties of the bearing lubricant, causing premature wear and failure of the bearing balls and raceways. Specifying a sealed bearing for this operating environment can prevent damage to the bearing elements, ensuring the predicted lifespan of the system.

Shielded linear bearings: Generally, shielded bearings are used in environments with heavy concentrations of large particulates such as metal flakes that can work their way between the balls and bearing raceways. The larger debris can cause premature wear and damage such as brinelling or spalling.

Sealed and shielded: Bearings that feature shields and seals combine the advantages of both sealed and shielded wheels. The shield protects the seal from damage by large particulates, while the seal protects the bearing elements from the fine particulates and liquid that the shield is less effective against.

Special linear-bearing configurations: One example is a washdown bearing including a patented inner seal and outer shield design. The design of the outer shield allows it to act as a momentary seal when subjected to pressure from high velocity fluid such as washdown spray. The pressure causes the shield to deflect and conform to the wheel’s metallic surface. When the pressure is removed, the shield returns to its normal position, allowing liquid and debris that entered between the shield and seal to drain out or be spun out by centrifugal force when the wheel rotates.

Note that in contaminated environments, a derating factor based on the severity of the contamination must be used for proper sizing.