Cold Forging Hub Body Step Section Precision

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Solution Overview

Problem

Conventional methods face challenges in processing the small-diameter step section of hub bodies for wheel support bearing ring members with high precision and low cost, particularly due to issues with thermal expansion and decarburization, which affect the accuracy and material yield.

Innovation Solution

A cold forging process using floating dies is employed to form the small-diameter step section without heating the metallic material, allowing for precise processing and reducing deformation, while the outward facing flange and positioning cylinder can be formed using hot or cold forging methods, enabling flexible processing sequences.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If hot forging is used to process the small-diameter step section, then processing cost is reduced, but dimensional precision deteriorates due to thermal expansion

Engineering Contradiction:

Improveprocessing costVSAvoiddimensional precision

Core Design Contradiction:

Ease of manufactureVSManufacturing precision

Solution Approach 1:

The processing is divided into two stages: first, hot forging is used to form the general shape of the hub body; second, cold forging is used to precisely form the small-diameter step section. This segmentation allows each process to be optimized for its specific function, resolving the contradiction between cost and precision.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The hot forging process is performed first to create the preliminary shape and reduce the overall dimensions, preparing the workpiece for the subsequent cold forging process. This preliminary action enables the final precision process to focus only on the critical small-diameter step section.

Inventive Principle:

Principle #10Preliminary action

2Object-affected harmful factors

If cutting is used to remove the decarburized layer, then surface quality is improved, but material yield deteriorates

Engineering Contradiction:

Improvesurface qualityVSAvoidmaterial yield

Core Design Contradiction:

Object-affected harmful factorsVSLoss of substance

Solution Approach 1:

The decarburized layer formed during hot forging, which is normally harmful, is converted into a beneficial feature by performing cold forging at a controlled stage. The cold forging process consolidates the surface layer and creates the precise small-diameter step section without requiring removal of the decarburized layer, thus eliminating material waste while maintaining surface quality.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

3Manufacturing precision

If cold forging is used to process the small-diameter step section, then dimensional precision is improved, but processing complexity increases

Engineering Contradiction:

Improvedimensional precisionVSAvoidprocessing complexity

Core Design Contradiction:

Manufacturing precisionVSDevice complexity

Solution Approach 1:

Cold forging is applied locally only to the small-diameter step section rather than the entire hub body. This localized application maintains high dimensional precision for the critical feature while minimizing the overall processing complexity and equipment requirements.

Inventive Principle:

Principle #3Local quality

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 enables stable and precise processing of the small-diameter step section, minimizing dimensional errors and maintaining high precision, while allowing for cost-effective production and improved material yield by optimizing the processing sequence and finishing processes.

Implementation Method 1

a base end surface of the metallic material is pressed toward the receiving punch by a pressing punch to press the cylindrical surface section into the receiving punch and form the small-diameter section by plastic working in a cold state

Methodology Applied

Scientific EffectPlasticity: Plasticity

Implementation Method 2

at least a part of an outer peripheral surface of the cylindrical surface section is supported by an inner peripheral surface of a floating die, which is supported so as to be movable in an axial direction of the cylindrical surface section and which is in a state that elastic force is applied thereto in a direction toward the outward facing flange

Methodology Applied

Scientific EffectElasticity: Elasticity

Data Source

PatentUS8635775B2Process for manufacturing a bearing ring member as a constituent of a rolling bearing unit for wheel support

Publication Date: 2014.01.28 NSK LTD

AI summary

This invention provided a manufacturing method to process a small-diameter step section 18 on an inside end section of a hub body 13a that comprises an outward facing flange 15 and a positioning cylinder 16 stably and with high precision. In this invention, an intermediate material 40 is pressed between a lower punch 36 and an upper punch 46 with an outer peripheral surface of the intermediate material 40 being held by a lower die 37 and an upper die 43, and then a part of the intermediate material 40 is pressed into the lower punch 36 such that the small-diameter step section 18 is formed by cold plastic working.