Steering Rack Teeth Forming Reducing Die Load
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Solution Overview
Problem
Conventional methods for manufacturing steering racks are costly, require complex dies, result in insufficient material filling, and compromise the strength and accuracy of the rack teeth due to high processing loads and burr formation.
Innovation Solution
The method involves using a hollow cylindrical first rack blank and a solid second rack blank with a specific cross-sectional shape, allowing the blank material to flow into the gap between them, enabling cold forming with reduced load and enhancing material filling, while simplifying the die structure and eliminating the need for a mandrel.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a solid round bar is used as a rack blank and rack teeth are formed by cutting, then the rack teeth can be formed with good strength, but the processing cost becomes high due to requiring an extra step for eliminating burrs
Solution Approach 1:
The invention changes the physical state of the blank material by heating it to a plastic state, enabling plastic working instead of cutting. This parameter change allows the formation of rack teeth without generating burrs, eliminating the need for additional burr removal steps and reducing manufacturing cost while maintaining tooth strength
Solution Approach 2:
The invention replaces the cutting mechanical system with a plastic working system using a die. By applying heat to achieve plastic state and then using die pressing, the process substitutes traditional cutting operations, eliminating burr formation and the associated post-processing steps
2Ease of manufacture
If a solid round bar is used as a rack blank and plastic working is used to form rack teeth, then the manufacturing cost is reduced, but a large load is applied to the die and burrs are formed
Solution Approach 1:
Heating the blank material to a plastic state changes its mechanical properties, making it more ductile and easier to deform. This parameter change reduces the force required for plastic working, allowing the die to form rack teeth with lower load while preventing burr formation through controlled material flow
3Ease of manufacture
If a hollow tubular rack blank is used and a mandrel is pressed into the bore hole to form rack teeth, then the rack can be formed, but a large processing force is required and multiple mandrels must be exchanged
Solution Approach 1:
The invention extracts and eliminates the mandrel from the process by using a die that directly forms rack teeth on the hollow tubular blank. This removal of the mandrel eliminates the need for mandrel exchange operations, reducing processing time and improving productivity while maintaining the capability to form rack teeth on hollow blanks
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 results in a lightweight steering rack with improved material filling, increased rigidity, and reduced manufacturing costs, as well as extended die lifetime and precision in forming the rack teeth.
Implementation Method 1
allowing the blank material to flow into the gap between them, enabling cold forming with reduced load
Data Source
Figure 1A
Figure 1B
Figure 2A
AI summary
When a punch is downwardly pressed, an inner circumferential surface of a first rack blank bites into a top surface of a second rack blank. A blank material upwardly flows due to a reaction force and is used to form rack teeth. Thus, a filling degree of the teeth with the material is enhanced. At the time when the forming of the rack teeth is finished, a gap is left between the inner circumferential surface of the first rack blank and the outer circumferential surface of the second rack blank. Thus, a die is not put into a sealed condition. Consequently, a forming load is small so that the lifetime of the die is lengthened. Also, the top surface of the second rack blank bites into a bore hole portion of the first rack blank so that the first rack blank and the second rack blank are joined together. Accordingly, the rigidity of the entire rack teeth is increased.