Metal Rack Preforming With Concave Groove for Lower Pressing Force
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Solution Overview
Problem
The existing manufacturing methods for metal racks in rack and pinion steering gear units face high costs and challenges in maintaining strength and rigidity due to high surface pressure and friction during the teeth-forming process, which requires large pressing forces and can lead to increased device size and manufacturing costs.
Innovation Solution
A method involving a preforming process to create an intermediate material with a concave groove, followed by teeth-forming using a split die to constrain only the sides of the groove, reducing excess material displacement and surface pressure, and a finishing process to form rack teeth, which includes using a knockout pin to manage the concave groove and minimize material movement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the rack teeth are formed by plastically deforming metal material, then the manufacturing cost is reduced and the strength and rigidity of the rack teeth are maintained, but the surface pressure and friction during the teeth-forming process become excessively high, requiring large pressing forces that increase device size and manufacturing cost
Solution Approach 1:
A preforming process is performed before the teeth-forming process to preliminarily shape the metal material into an intermediate form with reduced cross-sectional area. This preliminary action reduces the volume of material that needs to be displaced during subsequent teeth-forming, thereby reducing the surface pressure and friction, and allowing the use of smaller pressing forces and equipment.
2Strength
If the entire rack body is formed with a small radius of curvature to maintain strength and rigidity, then the structural integrity is improved, but the weight of the rack increases
Solution Approach 1:
The rack is designed with different radius of curvature values in different sections: a smaller radius of curvature (r13) in the rack teeth section where strength and rigidity are critical, and a larger radius of curvature (R12) in the other sections where weight reduction is prioritized. This local differentiation allows the rack to maintain necessary mechanical properties in the teeth section while reducing overall weight through material removal in less critical areas.
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 reduces manufacturing costs by minimizing resistance and device size, allowing for efficient production of racks with maintained strength and rigidity while preventing die damage and burr formation.
Implementation Method 1
In the preforming process, the metal material is pressed into a preforming die cavity by a preforming punch to form an intermediate material
Implementation Method 2
the intermediate material is pressed into a teeth-forming die cavity by a teeth-forming punch to form a raw rack
Implementation Method 3
the raw rack is pressed into a finishing forming die cavity by a finishing forming punch to form the rack
Data Source
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AI summary
To provide a method for manufacturing a rack that can reduce the manufacturing cost, the method comprises the following processes. An intermediate material 18a having a concave groove 42y in part in the radial direction of the outer circumferential surface that extends in the axial direction and is recessed inward in the radial direction is obtained. A plurality of rack teeth 10z are formed on an opposite surface to the concave groove 42y with respect to the radial direction of the outer circumferential surface of the intermediate material 18a by pressing the teeth-forming concave and convex section 28 that have a concave and convex configuration with respect to the axial direction in a state where the portions on both sides of the concave groove 42y of the outer circumferential surface of the intermediate material with respect to the circumferential direction are constrained and the inner surface of the concave groove 42y is not constrained.