CV Joint Shaft Forging with Split Dies for Accurate Enlarged Sections
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Solution Overview
Problem
Existing forging methods for shaft members with multiple enlarged diameter portions, such as those used in constant velocity universal joints, face issues with material yield, accuracy, and manufacturing cost due to the need for complex and expensive dedicated machines, which result in inefficiencies like material flow into gaps and shifting during processing, leading to post-processing requirements like burr removal and increased machining allowances.
Innovation Solution
A forging method utilizing split dies and a closing ring with a pressure mechanism to apply force, allowing for precise formation of enlarged diameter portions using general-purpose equipment, eliminating the need for complex machines and reducing post-processing steps by stabilizing the length dimension and minimizing material flow into gaps.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If gripping dies are used to apply pressure to the billet, then the enlarged diameter portion can be formed, but material flows into the gap between gripping dies causing projecting portions that require removal processing
Solution Approach 1:
The die is divided into two separate halves (first die and second die) that close from opposite directions toward the center line. This segmentation eliminates the need for a gap between gripping dies, preventing material flow into gaps while still enabling the forming of enlarged diameter portions.
Solution Approach 2:
Instead of having a single die grip the billet from one side with an opening, the invention inverts the approach by using two separate dies that close from opposite directions. The dies approach each other symmetrically, eliminating the gap issue while maintaining gripping capability.
2Ease of manufacture
If gripping dies with gap are used to apply pressure, then the enlarged diameter portion can be formed, but the semi-finished member may shift during formation requiring large machining allowances
Solution Approach 1:
The die system is segmented into two independent halves that close symmetrically from opposite directions. This segmentation provides balanced gripping force that prevents shifting of the semi-finished member during formation, eliminating the need for large machining allowances.
Solution Approach 2:
The invention uses symmetric closure of dies from opposite directions, which is a form of controlled symmetry. The bilateral symmetric approach ensures equal and opposite forces that prevent lateral shifting, improving length dimension accuracy.
3Ease of manufacture
If upset forging machine is used to form enlarged diameter portions, then the forming can be completed, but the complex mechanism results in expensive equipment cost
Solution Approach 1:
The complex upset forging machine is replaced by a simpler segmented die system consisting of two separate dies that can be used with general-purpose pressing equipment. This segmentation simplifies the mechanism while maintaining the capability to form enlarged diameter portions.
Solution Approach 2:
The segmented die system is designed to be compatible with general-purpose pressing equipment, making the forming process universal and not requiring dedicated complex upset forging machines. This multi-functionality reduces equipment cost while maintaining forming capability.
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 method increases yield and accuracy while reducing manufacturing costs by enabling the use of inexpensive equipment and minimizing post-processing steps, such as burr removal, and eliminates the need for normalizing or shot peening, thereby enhancing productivity.
Implementation Method 1
a closing ring configured to apply a force of closing the split dies, and wherein pressure is applied to the closing ring
Implementation Method 2
filling the semi-finished member into the forming surfaces of the split dies by the pressure applied by the punch
Implementation Method 3
cramping the semi-finished member in a radial direction of the semi-finished member by closing the split dies
Data Source
Figure 1
Figure 2a~2b
Figure 3
AI summary
Provided is a forging method for a shaft member (13a) of a constant velocity universal joint (10, 20) including a plurality of enlarged diameter portions (61, 62) on a shaft section (60) of the shaft member (13a), the method including: preforming at least one (61) of the plurality of enlarged diameter portions (61, 62) to obtain a semi-finished member (B"); and forming a remainder (62) of the enlarged diameter portions in the semi-finished member (B") using a mold, the mold including: a punch (81); split dies (83), which are configured to accommodate the at least one (61) of the enlarged diameter portions and the shaft section (60) of the semi-finished member (B") therein, and each include a forming surface (83a); and a workpiece receiving member (84), which is configured to allow the at least one (61) of the enlarged diameter portions of the semi-finished member (B") to be placed thereon, and receive pressure applied by the punch (81), the forming a remainder (62) of the enlarged diameter portions comprising: allowing the semi-finished member (B") having the at least one (61) of the enlarged diameter portions to be placed on the workpiece receiving member (84); cramping the semi-finished member (B") in a radial direction of the semi-finished member (B") by closing the split dies (83); and filling the semi-finished member (B") into the forming surfaces (83) of the split dies by the pressure applied by the punch (81) under the state in which the semi-finished member (B") is cramped.