Linear Motion Guide Raceway Groove Curvature Optimization
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Solution Overview
Problem
Conventional linear motion guide devices experience increased contact surface pressure and edge loads when subjected to pressing, tensile, or lateral loads due to asymmetric raceway groove sectional shapes, leading to potential plastic deformation and reduced smooth ball circulation.
Innovation Solution
The design incorporates raceway grooves with main arc portions and sub-arc portions on the guide rail and slider, where the curvature radii of the groove shoulder and bottom side sub-arc portions differ, and the arc central angles of these sub-arc portions are specifically defined to reduce contact surface pressure, preventing edge loads by ensuring smooth connections and optimal curvature radii values.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a gothic-arc groove with single-arc sectional shape is used as the raceway groove, then manufacturing accuracy is easily secured, but contact surface pressure between ball and raceway groove increases leading to edge loads
Solution Approach 1:
The raceway groove is segmented into multiple arc portions with different curvature radii along the width direction. Specifically, the groove includes a first arc portion, second arc portion, third arc portion, and fourth arc portion, where the first and second arc portions have a first curvature radius and the third and fourth arc portions have a second curvature radius. This segmentation allows different regions of the groove to have optimized curvature radii for reducing contact pressure while maintaining manufacturing feasibility.
Solution Approach 2:
Different portions of the raceway groove are given different local properties through varying curvature radii. The first and second arc portions (typically near the groove shoulders) have one curvature radius optimized for reducing edge loads, while the third and fourth arc portions (typically near the groove bottom) have another curvature radius optimized for ball contact pressure distribution. This local differentiation addresses the specific stress conditions at different locations within the groove.
2Stress or pressure
If a combined-arc groove with asymmetric sectional shape is used, then contact surface pressure is reduced under symmetric loading, but edge loads occur under asymmetric loading conditions such as tensile or lateral loads
Solution Approach 1:
The raceway groove employs intentional asymmetry in its curvature radius distribution to counteract the effects of asymmetric loading. By having different curvature radii in different portions of the groove (first/second portions with first curvature radius, third/fourth portions with second curvature radius), the groove creates a non-uniform contact stress distribution that compensates for asymmetric load conditions, preventing edge loads even when tensile or lateral forces are applied.
Solution Approach 2:
The curvature radius parameter is varied across different portions of the raceway groove to optimize performance under various loading conditions. The first curvature radius (for first and second arc portions) and second curvature radius (for third and fourth arc portions) are specifically selected to change the contact stress distribution, thereby maintaining reliability and preventing edge loads across symmetric and asymmetric loading scenarios.
Data Source
Figure 1~2
Figure 3
Figure 4
AI summary
There is provided a linear motion guide device that is reduced in a contact surface pressure between a ball and a raceway groove so that an occurrence of an edge load can hardly occur, even when any of a pressing load, a tensile load, and a lateral load is applied to a slider. Upper flanks (20U) and lower flanks (20L) included in raceway grooves (10, 11) of a guide rail (1) and a slider (2) each include: a main arc portion (21) having an arc-shaped section and placed generally in a center of the flank (20U, 20L) in a width direction; a groove shoulder side sub-arc portion (23) having an arc-shaped section and formed continuously from a groove shoulder side of the main arc portion (21) ; and a groove bottom side sub-arc portion (25) having an arc sectional shape and formed continuously from a groove bottom side of the main arc portion (21). Further, a curvature radius (r2P) of the groove shoulder side sub-arc portion (23) is different from a curvature radius (r2m) of the groove bottom side sub-arc portion (25)..1