Linear Motion Guide Crowning Profile for Stress Reduction
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Solution Overview
Problem
Existing linear motion guide units face challenges in achieving high accuracy and durability, especially under high-speed and high-acceleration conditions, due to variations in crowning profile dimensions and steep sloping angles, which affect sliding resistance and noise, and require complex machining processes.
Innovation Solution
A linear motion guide unit with a crowning profile on the raceway groove that is gently curved, merging smoothly into rounded bevels, and having a depth equivalent to elastic deformation, allowing for reduced stress concentration and improved sliding performance, with a gothic arched groove design for four-point contact, enhancing accuracy and durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a steep sloping angle is used in the crowning profile, then the ingress/egress of rolling elements is improved, but stress concentration and noise increase
Solution Approach 1:
The patent applies curvature by replacing the conventional steep sloping angle with a gently curved profile in the ingress/egress areas. The crowning profile uses a radius of curvature R1 that is at least 0.05 times the diameter of the rolling element, creating a rounded transition zone that eliminates stress concentration while maintaining smooth rolling element ingress and egress.
Solution Approach 2:
The patent changes the geometric parameters of the crowning profile by defining specific radius of curvature values (R1 ≥ 0.05d) and slope angles (α ≤ 15 degrees). These parameter modifications transform the steep angular transition into a gentle curved transition, reducing stress concentration and noise while preserving operational smoothness.
2Manufacturing precision
If a complex machining process is used to achieve high precision crowning profile, then traveling accuracy is improved, but manufacturing complexity increases
Solution Approach 1:
The patent simplifies the machining process by defining the crowning profile through straightforward geometric parameters (radius of curvature R1 and slope angle α) that can be directly implemented using standard CNC machining operations. This approach achieves high traveling accuracy without requiring complex multi-step machining processes or specialized equipment.
Solution Approach 2:
The patent applies local quality by specifying that the curved profile with radius R1 is only required in the ingress/egress areas of the load race, while the major load area can maintain a simpler geometry. This localized application of curvature reduces overall manufacturing complexity while maintaining high precision where it is most needed for rolling element transition.
3Ease of manufacture
If conventional crowning profile with sharp edges is used, then machining is simpler, but stress concentration occurs at junctions
Solution Approach 1:
The patent eliminates stress concentration at junctions by replacing sharp edges with curved transitions. The crowning profile uses a continuous curved geometry with radius of curvature R1 that smoothly connects the ingress/egress areas to the major load area, removing discontinuous sharp edges that would otherwise create stress concentration points.
Solution Approach 2:
Instead of starting with a simple geometry and adding complexity to reduce stress, the patent inverts the approach by defining the geometry through its curvature characteristics from the outset. The crowning profile is designed with the required radius of curvature R1 as the fundamental geometric constraint, which naturally produces stress-free transitions while remaining manufacturable.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution provides improved traveling accuracy and durability by reducing stress concentrations and noise, while simplifying the machining process, resulting in a high-precision and long-lasting linear motion guide unit suitable for high-speed and high-acceleration applications.
Implementation Method 1
a depth equivalent to elastic deformation, allowing for reduced stress concentration
Data Source
AI summary
A linear motion guide unit is provided in which a crowning portion available extensively for standard specification is made easily. The crowning portion is comparatively small in depth, and rich in high accuracy and high durability. A raceway groove for a load race in a carriage is made at an ingress/egress area thereof with the crowning portion of a curved profile that varies gently to allow the rolling element to move in and out of the load race with smoothness. The carriage is provided at the forward and aft ends of the raceway groove with rounded bevels, which are made in a curved contour merging into the associated crowning portion without causing any discontinuity at a junction of the rounded bevel with the crowning portion.