THK-SCR-Series - Caged Ball Cross LM Guide

Nov 2, 2026

Caged Ball design principles explain how a ball cage eliminates direct ball-to-ball friction, reducing noise, heat generation, and wear while maintaining smooth motion and supporting long service life. The document compares conventional full-ball and needle structures with caged-ball approaches, describing oil-film retention and contact stress changes. It then introduces THK SCR LM Guide structures, including four-row raceway circulation, compact crossed integral design, equal-load capabilities across directions, and suitability for compact X-Y tables and applications such as hollow XY tables and NC lathes.

LanguageEnglish

CategoryTechnology

FormatPDF

Pages16

Reading Time40 min

AccessFree to download

Ball Cage Effect

Conventional vs. Caged Ball: Noise, oil film, wear

Caged Ball LM Guide

Grease pocket and oil-film minimization

Caged Ball Cross LM Guide (SCR)

Structure of Model SCR

Four-way equal-load type

High rigidity and compact design

Model SCR-Product Overview

Major applications

Drawing of use with inner saddle

Rated Loads in All Directions

Equivalent load equation

New Caged Ball Cross LM Guide Ball Cage Effect Cross-structured in a single piece with high rigidity SCR CATALOG No. 319E Ball Cage Effect The early forms of ball bearings were full-ball types without ball cages. Friction between balls caused loud noise, made high-speed rotation impossible and shortened the service life. Twenty years later, a Caged Ball design was developed for ball bearings. The new design enabled high-speed rotation at a low noise level, and extended the service life despite the reduced number of balls used. It marked a major development in the history of ball bearings. Similarly, the quality of needle bearings was significantly improved by the caged needle structure. With cage-less, full-ball types of ball bearings, balls make metallic contact with one another and produce loud noise. In addition, they rotate in opposite directions, causing the sliding contact between two adjacent balls to occur at a speed twice the ball-spinning rate. It results in severe wear and shortens the service life. In addition, without a cage, balls make point contact to increase bearing stress, thus facilitating breakage of the oil film. In contrast, each caged ball contacts the cage over a wide area. Therefore, the oil film does not break, the noise level is low and balls can rotate at a high speed, resulting in a long service life. Long Service Life and Long-term Maintenance-free Operation Superbly High Speed Low Noise, Acceptable Running Sound Smooth Motion Low Dust Generation Rotary ball bearing Conventional structure ●Adjacent balls contact each other at a point. As a result, contact stress is high and the oil film breaks due to friction. ●The service life becomes shorter. Caged Ball structure ●The service life is prolonged due to the elimination of wear caused by friction between balls. ●The absence of friction between balls results in reduced heat generation during high-speed rotation. ●The absence of friction between balls eliminates collision noise of the balls. ●The even spacing of the balls enables them to move smoothly. ●Retention of lubricant in the ball cage ensures a long service life. Caged Ball LM Guide Ball With the Caged Ball LM Guide, the use of a ball cage allows lines of evenly spaced balls to circulate, thus to eliminating friction between the balls. In addition, grease held in a space between the ball circulation path and the ball cage (grease pocket) is applied on the contact surface between each ball and the ball cage as the ball rotates, forming an oil film on the ball surface. This minimizes the risk of oil-film break. Conventional structure Caged Ball structure Compact, Highly Rigid Caged Ball Cross LM Guide SCR LM rail Grease nipple LM block Ball Ball cage Side seal End seal Endplate LM rail Structure of Model SCR Balls roll in four rows of raceways precision-ground on an LM rail and an LM block, and endplates incorporated in the LM block allow the balls to circulate. This model is an integral type of LM Guide that squares an internal structure similar to model SHS, which has a proven track record, with another and uses two LM rails in combination. Since an orthogonal LM system can be achieved with model SCR alone, a conventionally required saddle is no longer necessary, the structure for X-Y motion can be simplified and the whole system can be downsized. ● Four-way equal-load type Since each row of balls is arranged at a contact angle of 45˚ so that a uniform rated load on the LM block is achieved in the four directions (radial, reverse-radial and lateral directions), this model can be used in any orientation and in a broad range of applications. ● High rigidity Since balls are arranged in a well-balanced, four-row configuration, this model is robust against a moment and ensures smooth linear motion even under a preload to increase rigidity. Since the rigidity of the LM block is higher than a system

FAQs

How does the ball cage reduce noise and improve service life in ball bearings?

The cage eliminates friction between balls, reducing collision noise during high-speed rotation. It also supports retention of lubricant in the cage, minimizing oil-film break and wear.

What problems occur in cage-less, full-ball bearing types?

Balls make metallic contact and point contacts that increase contact stress, produce loud noise, and promote oil-film breakage. The sliding contact between adjacent balls at higher relative speed results in severe wear and shortens service life.

What is the key structural idea behind the THK SCR cross LM guide?

SCR integrates LM blocks crosswise on the XY axes using an orthogonal arrangement of four-row raceways on LM rails/blocks with endplates to allow circulation. This enables a compact X-Y structure without a conventionally required saddle while improving rigidity and load handling in multiple directions.

Nov 2, 2026

Uploaded by Dewi_Sukmawati