Hollow Rack Bar Preforming With Variable Wall Thickness
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Solution Overview
Problem
Existing methods for manufacturing hollow rack bars do not provide a specific process for forming relatively thick toothed sections and thin shaft sections, which are necessary to reduce weight and material usage effectively.
Innovation Solution
A manufacturing method and apparatus that utilize a die and plug to preform hollow shaft material, with distinct working sections to define different thicknesses for toothed and shaft sections, and a mandrel to form the rack by plastic flow, achieving a reduction in sectional areas of 10% to 35% to create a hollow rack bar with a rack on the outer surface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If the shaft material thickness is reduced to save material and reduce weight, then weight and material usage are reduced, but the structural strength and integrity may be compromised
Solution Approach 1:
The invention applies different wall thicknesses to different sections of the hollow shaft material: the toothed section has a first thickness while the shaft section has a second thickness that is thinner than the first. This local differentiation allows weight reduction in non-critical areas while maintaining sufficient strength in load-bearing regions.
Solution Approach 2:
The hollow shaft material is divided into distinct sections (toothed section and shaft section) with different thickness requirements. The preforming process segments the forming operation to apply different reduction rates to different sections, optimizing both weight and strength for each functional region.
2Loss of substance
If the shaft material is drawn through a die and plug to preform different thickness regions, then weight and material usage are reduced, but the manufacturing process complexity increases
Solution Approach 1:
The preforming step is performed before final rack formation to pre-establish the different thickness regions in the hollow shaft material. This preliminary action simplifies subsequent processing by preparing the material in its optimal shape before the actual rack teeth are formed.
Solution Approach 2:
The plug is designed with movable working sections that can change their effective diameter during the drawing process. The first working section has a smaller diameter for the toothed section while the second working section has a larger diameter for the shaft section, allowing dynamic adaptation to different forming requirements within a single continuous operation.
3Manufacturing precision
If the reduction rate from sectional areas before preforming to after preforming is optimized to 10%-35%, then manufacturing precision and material utilization are improved, but excessive reduction may cause material defects
Solution Approach 1:
The invention specifies an optimal reduction rate range of 10%-35% for the preforming operation. This parameter optimization ensures sufficient thickness differentiation between sections for weight savings while staying within limits that prevent material defects such as thinning, necking, or cracking during the plastic deformation process.
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 allows for the efficient reduction of weight and material usage in hollow rack bars by forming the shaft section thinner than the toothed section, enhancing material savings and weight reduction while maintaining structural integrity.
Implementation Method 1
a material of the toothed section forming region is caused to plastically flow towards the tooth die to form the rack
Data Source
AI summary
A manufacturing method is provided for a hollow rack bar made of a hollow shaft material and including a toothed section which has a rack on an outer surface and a shaft section which is thinner than the toothed section. The manufacturing method includes: (i) drawing the hollow shaft material using a die and a plug, and preforming regions of the hollow shaft material including a toothed section formation region configured to become the toothed section and a shaft section formation region configured to become the shaft section so as to have thicknesses according to the respective regions; and (ii) forming the rack at the toothed section formation region of the hollow shaft material which is preformed.