Steering-wheel Core Recess for Casting Surface Quality
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Solution Overview
Problem
Conventional methods of casting steering-wheel cores using magnesium alloy result in surface roughness issues, necessitating finishing processes like grinding, which increase manufacturing costs.
Innovation Solution
A steering-wheel core design featuring a boss core portion with an annular recess on the nut seat surface, which redirects the flow of molten magnesium alloy during casting to minimize direct contact with the die surface, reducing surface roughness and eliminating the need for post-casting finishing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If molten magnesium alloy is used for casting the steering-wheel core, then productivity and weight reduction are improved, but surface roughness deteriorates due to direct contact with the die surface
Solution Approach 1:
A protrusion is formed on the die surface at the position corresponding to the nut seat surface before casting. This protrusion prevents direct contact between the molten magnesium alloy and the die surface during filling, thereby preventing the formation of a rough casting surface. The protrusion acts as a preliminary protective structure that redirects the molten metal flow away from the critical nut seat area.
Solution Approach 2:
The protrusion on the die surface serves as an intermediary element between the molten magnesium alloy and the die. It redirects the flow of molten metal away from the nut seat surface, preventing direct contact and the resulting surface roughness. This intermediary structure allows the use of magnesium alloy casting while maintaining surface quality.
2Ease of manufacture
If conventional casting without surface protection is used, then manufacturing cost is reduced, but surface roughness increases requiring additional finishing processing
Solution Approach 1:
The protrusion is formed on the die surface before casting to prevent direct contact between molten metal and the die. This preliminary protective structure eliminates the need for post-casting finishing operations such as grinding, thereby maintaining low manufacturing costs while achieving acceptable surface roughness directly from casting.
Solution Approach 2:
The die structure itself provides the protective function through the protrusion, eliminating the need for separate finishing operations. The casting process inherently produces the required surface quality when the protrusion is present, making the process self-sufficient and reducing additional manufacturing steps.
3Reliability
If the nut seat surface requires high precision to control nut torque, then reliability is improved, but manufacturing complexity increases due to required finishing processing
Solution Approach 1:
The protrusion is formed on the die surface before casting to ensure the nut seat surface does not come into direct contact with molten metal. This preliminary protective measure guarantees acceptable surface roughness that is sufficient for torque control, eliminating the need for additional finishing operations and reducing manufacturing process complexity while maintaining reliability.
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 effectively decreases surface roughness by 39% to 71% compared to conventional methods, eliminating the need for finishing processes and lowering manufacturing costs.
Implementation Method 1
When a high-temperature and high-pressure molten magnesium alloy is caused to flow into a die
Implementation Method 2
A recess that is preferably depressed toward a back surface side of the boss core portion is formed in the nut seat surface
Data Source
AI summary
A steering-wheel core eliminating or reducing the need to perform finishing processing after casting and decreasing a manufacturing cost even when the steering-wheel core is cast using a molten metal process. The steering wheel core includes a boss core portion coupled to a steering shaft, a rim core portion and a spoke core portion. The boss core portion forms a nut seat surface that makes contact with a nut when the nut is fastened to a distal end of the steering shaft. A recess is formed in the nut seat surface depressed toward a back surface side of the boss core portion. The recess is preferably provided in an annular form so as to surround the circumference of the nut seat surface.