Tripod Joint Forging with Shear-Drop Suppression
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Solution Overview
Problem
In full-enclosed forging dies, the 'shear drop' issue occurs when forming shaft portions with varying raw material weights, leading to increased processing load and die wear, necessitating additional material and machining processes to achieve accurate dimensions and strength for constant velocity universal joints.
Innovation Solution
A forging method and apparatus that incorporates a shear-drop suppressing portion on the preliminary leading-end surface of the shaft portions and a relief portion between the leading end surface and the die cavity, reducing thickness reduction and securing a gap even with heavy raw materials, thereby stabilizing the die and enabling high-accuracy machining without pre-removal of the shaft leading end.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of stationary object
If a relief portion is provided at the shaft-leading-end portion to prevent die breakage, then die life is improved, but shear drop occurs causing manufacturing precision to deteriorate
Solution Approach 1:
The invention performs preliminary action by forming a preliminarily molded product with a preliminarily formed leading-end surface before the final forging process. This preliminary formation of the leading-end surface prevents shear drop during the subsequent full-enclosed forging, eliminating the need for a relief portion and thereby maintaining both die life and manufacturing precision.
Solution Approach 2:
The invention segments the forging process into two distinct stages: (1) preliminary molding to form the leading-end surface, and (2) full-enclosed forging to form the final product shape. This segmentation allows each stage to optimize for its specific function, preventing the shear drop problem that occurs when combining both functions in a single step.
2Length of moving object
If extra material is added to compensate for shear drop, then shaft portion length is secured, but material waste increases
Solution Approach 1:
The preliminarily formed leading-end surface is created in advance with the correct dimensions, eliminating the need to add extra material to compensate for subsequent shear drop. This preliminary action ensures the final shaft portion length is accurate without material waste.
3Manufacturing precision
If shaft leading end is removed by machining prior to heat treatment, then high accuracy machining is enabled, but device complexity and processing time increase
Solution Approach 1:
The leading-end surface is preliminarily formed during the molding process itself, rather than requiring separate machining operations. This preliminary formation eliminates the need for pre-heat treatment machining and subsequent high-accuracy machining, simplifying the overall device and process while maintaining high precision.
Solution Approach 2:
The invention merges the leading-end surface formation into the molding process, combining what were previously separate operations (molding and machining) into a single integrated process. This eliminates intermediate machining steps and reduces device complexity.
4Strength
If full-enclosed forging die is used to form shaft portions, then product strength is improved, but processing load increases causing die breakage risk
Solution Approach 1:
The forging process is segmented into preliminary molding (forming the leading-end surface) and full-enclosed forging (forming the final shape). This segmentation allows the full-enclosed forging to operate at optimized load levels since the material flow is already partially established, reducing the risk of die breakage while maintaining product strength.
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 method effectively reduces shear drop, prolongs die life, allows for compactification and weight reduction of universal joints, and eliminates the need for pre-heat treatment machining, reducing material and machining costs.
Implementation Method 1
the billet 10 is pressed with the punches 4 and 5 so as to be plastically deformed
Data Source
AI summary
After molding a preliminarily molded product as a material, the preliminarily molded product is put into a full-enclosed forging die so that a product is molded with the full-enclosed forging die. A shear-drop suppressing portion for suppressing thickness reduction on a boss-portion side of an outer peripheral portion of a leading end surface of each of shaft portions of the product is formed on the preliminary leading-end surface configuring a leading end surface of each of the shaft portions of the product in the preliminarily molded product. When the preliminarily molded product is put into the full-enclosed forging die and the product is to be molded, a relief portion is formed between the leading end surface of each of the shaft portions to be molded and a cavity of the full-enclosed forging die.