Linear Roller Bearing Rack Electrochemical Machining

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Solution Overview

Problem

Existing linear roller bearing arrangements face limitations in achieving precise surface roughness, high load capacity, and efficient use of limited space due to conventional machining methods, which result in suboptimal performance and structural integrity.

Innovation Solution

The use of precise electrochemical machining (PEM) to produce rack-like areas with surface roughness less than 0.4 μm and small cross-section rails, enabling involute gearing and non-rotationally symmetrical indentations, thereby enhancing load capacity and preventing issues like white layers and decarburization.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If conventional machining methods are used to produce rack-like areas, then manufacturing is simpler, but surface roughness is poor (Ra > 0.4 μm) and white layers form

Engineering Contradiction:
Improvesurface roughnessVSAvoidmanufacturing complexity
Core Design Contradiction:
Manufacturing precisionVSEase of manufacture

Solution Approach 1:

The patent replaces conventional mechanical machining methods with electrochemical machining (ECM). This substitution eliminates mechanical contact between cutting tools and the workpiece, thereby avoiding white layer formation and achieving superior surface roughness (Ra < 0.4 μm) without compromising manufacturing feasibility

Inventive Principle:
Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent changes the fundamental process parameters from mechanical cutting to electrochemical dissolution. By controlling electrical current density, electrolyte composition, and pulse duration, the process achieves precise material removal with excellent surface finish while maintaining manufacturing efficiency

Inventive Principle:
Principle #35Parameter changes

2Reliability

If normal eroding processes are used, then material removal is achieved, but white layers and decarburization occur in the substructure

Engineering Contradiction:
Improvestructural integrityVSAvoidwhite layers and decarburization
Core Design Contradiction:
ReliabilityVSObject-generated harmful factors

Solution Approach 1:

The patent replaces thermal and mechanical eroding processes with electrochemical machining. This substitution eliminates the high temperatures and mechanical stresses that cause white layer formation and decarburization, preserving the metallurgical integrity of the steel rail material

Inventive Principle:
Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The electrochemical process creates an inert-like environment through controlled electrolyte chemistry and low process temperatures. This prevents oxidative decarburization and other thermally-induced harmful reactions that occur in conventional eroding processes

Inventive Principle:
Principle #39Inert atmosphere (Inert environment)

3Manufacturing precision

If traditional machining is used on small cross-section rails, then manufacturing is easier, but precision and load capacity are insufficient

Engineering Contradiction:
Improveprecision rail geometryVSAvoidmanufacturing difficulty
Core Design Contradiction:
Manufacturing precisionVSEase of manufacture

Solution Approach 1:

The patent applies electrochemical machining to small cross-section rails, replacing mechanical cutting tools that cannot achieve sufficient precision on tiny geometries. The ECM process delivers Ra < 0.4 μm surface finish and precise involute tooth profiles on rails with cross-sections less than 50 mm²

Inventive Principle:
Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent optimizes electrochemical process parameters for small-scale machining, including current density distribution, electrolyte flow rates, and pulse duration. These parameter adjustments enable high-precision manufacturing of small cross-section rails that would be infeasible with conventional methods

Inventive Principle:
Principle #35Parameter changes

4Strength

If space is not optimized in rail base, then manufacturing is simpler, but load capacity is reduced

Engineering Contradiction:
Improveload capacityVSAvoidindentation geometry
Core Design Contradiction:
StrengthVSDevice complexity

Solution Approach 1:

The patent employs asymmetric, non-rotationally symmetrical indentation shapes in the rail base to maximize space utilization. This asymmetric geometry allows optimized positioning of rolling elements and improved load distribution, increasing load capacity within the limited rail cross-sectional area

Inventive Principle:
Principle #4Asymmetry

Solution Approach 2:

The patent optimizes the geometric parameters of the indentations including depth, width, and angular orientation. These parameter optimizations enable better packing of rolling elements and improved mechanical leverage, thereby increasing load capacity without adding external components

Inventive Principle:
Principle #35Parameter changes

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

This approach allows for higher load capacities, improved surface finish, and efficient use of space, preventing decarburization and maintaining structural integrity at lower process temperatures, effectively addressing the limitations of conventional machining methods.

Implementation Method 1

The invention is based on the finding that using a method for precise electrochemical machining (also known as PEM or Precise Electrochemical Machining), in particular on precision rails, rack-like areas for forced control of rolling elements arranged between the rails can be produced

Methodology Applied
Scientific EffectElectrochemical machining: Electrolysis

Data Source

PatentEP1972806B1Linear roller bearing assembly
Publication Date: 2010.07.14 AB SKF SKF PATENT DEPARTMENT
  • EP1972806B1 patent drawingFigure 1
  • EP1972806B1 patent drawingFigure 2~4
  • EP1972806B1 patent drawingFigure 5

AI summary

The arrangement has two parts (10, 20) longitudinally movable with respect to each other via at least one series of roller bearings, a positive controller for the roller bodies (5) containing a gearwheel type element (32) for engaging in a rack type region (22) on at least one of the parts and surface roughness in at least recesses of the rack type region with a roughness coefficient of less than 0.4 microns, especially less than 0.3 microns.