Differential Thickness Pipe Extrusion Using a Stepped Core Bar
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Solution Overview
Problem
Existing manufacturing methods for differential thickness pipes are inefficient and costly, requiring multiple steps and high processing loads to achieve the desired mechanical strength and weight reduction.
Innovation Solution
The method involves using a core bar with a small cross-section portion at its tip end and a raw pipe with a thin-walled portion at its tip end, subjected to extrusion processing in a die with a small inner diameter, to form a differential thickness pipe with a thick-walled portion at the tip end or intermediate position.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If multiple steps including drawing, inserting core bars, and repeated extrusion are used to manufacture differential thickness pipe, then the desired mechanical strength and weight reduction are achieved, but the production efficiency decreases and manufacturing cost increases
Solution Approach 1:
The raw pipe is prepared in advance with a thin-walled portion at the tip end before the extrusion process. This preliminary preparation eliminates the need for multiple subsequent processing steps to create the differential thickness structure, thereby improving production efficiency while maintaining the desired mechanical strength characteristics
Solution Approach 2:
The extrusion process is segmented into two independent stages: first forming the thin-walled portion at the tip end, then forming the thick-walled portion at the base end. This segmentation allows each portion to be optimized independently without requiring repeated processing cycles, thus enhancing productivity
2Strength
If work hardening occurs in the thick-walled portion during processing, then the mechanical strength is improved, but the processing load increases significantly requiring very high processing loads
Solution Approach 1:
The thin-walled portion is formed in advance before the thick-walled portion processing. This preliminary formation reduces the overall processing load by breaking down the work hardening process into manageable stages, allowing the thick-walled portion to be processed with moderate loads while still achieving the desired mechanical strength through controlled work hardening
3Shape
If a mechanism for controlling positional relation between die and mandrel is used to achieve variable cross-section, then the desired cross-sectional shape is obtained, but the apparatus size increases and configuration becomes complicated
Solution Approach 1:
The die and mandrel are designed with locally varied geometries - the die has different diameter sections and the mandrel has corresponding dimensional variations. This allows the desired variable cross-sectional shape to be achieved through the inherent geometry of the tools rather than complex control mechanisms, simplifying the apparatus configuration
Solution Approach 2:
The positional relationship between the die and mandrel is predetermined by their fixed geometric configurations rather than requiring dynamic control mechanisms. The tools are designed to naturally maintain the correct relative positioning, eliminating the need for complex control systems while achieving the desired variable cross-section
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 and cost-effective production of differential thickness pipes with various configurations, achieving high production efficiency and low manufacturing costs.
Implementation Method 1
a first step in which a differential thickness pipe having a predetermined shape is molded by pressing a pair of a first raw pipe having a predetermined shape and the first core bar into the first die hole with the first drive mechanism to perform extrusion processing
Data Source
AI summary
In extrusion processing in which diameter reduction is performed by pressing a raw pipe having a core bar inserted therein into a die having a small inner diameter portion on its tip end side, a differential thickness pipe having a thick-walled portion at its tip end can be molded using a core bar having a small cross-section portion formed at its tip end. It is also possible to mold a differential thickness pipe having a thick-walled part at an intermediate axial position by using a raw pipe having a thin-walled portion at its tip end. For example, such a raw pipe can be molded by extrusion processing using a core bar having no small cross section portion at its tip end, prior to the above-described formation of the thick-walled portion. When higher dimensional accuracy is required, a so-called “counter punch” may be used in the formation of the thick-walled portion.