Double-Die Deep Drawing for Uniform Pressure Vessel Cups
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Solution Overview
Problem
Conventional deep drawing methods struggle with microcracking and defects in lower grade metals, particularly when forming pressure vessels, and require secondary machining that can introduce further defects, limiting the use of high strength, low alloy materials.
Innovation Solution
A double die configuration using a top die with a tractrix profile and a bottom die with specific spacing and draw lines to achieve simultaneous shaping and thinning of metal blanks in a single operation, followed by a smash operation to prepare the cup for welding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional deep drawing methods are used to form metal cups, then the cup shape is formed, but microcracks and defects are introduced into the material, particularly in lower grade metals
Solution Approach 1:
The deep drawing process is divided into two distinct stages: first drawing the cup shape, then performing ironing to thin and uniform the walls. This segmentation allows each stage to be optimized independently, preventing microcracks while achieving the desired cup geometry and uniform wall thickness.
Solution Approach 2:
The tractrix profile in the first die is designed to pre-condition the metal blank during the initial drawing stage, preparing the material flow and stress distribution for the subsequent ironing stage. This preliminary action ensures that the material is properly positioned and stressed before the critical wall-thinning operation.
2Manufacturing precision
If conventional deep drawing is used to form pressure vessel cups, then the cup shape is achieved, but secondary machining is required to prepare welding surfaces, which introduces additional defects
Solution Approach 1:
The deep drawing and ironing operations are merged into a single integrated process using a specialized two-stage die. This combination eliminates the need for separate machining operations to prepare welding surfaces, as the ironing process naturally produces the required surface quality and geometry in one step.
3Strength
If conventional deep drawing methods are used, then high strength low alloy materials cannot be utilized due to microcracking, but these materials are needed for pressure vessel applications
Solution Approach 1:
The patent changes the critical parameters of the deep drawing process by implementing the two-stage die with tractrix profile and controlled ironing. This parameter change transforms the stress and strain distribution during forming, allowing high strength low alloy materials to be successfully formed without microcracking, thus enabling their use in pressure vessel applications.
4Device complexity
If a single die is used for deep drawing, then the process is simpler, but uniform wall thickness cannot be achieved
Solution Approach 1:
The single die is segmented into two functional stages: the first stage draws the cup shape using a tractrix profile, and the second stage irons the walls to achieve uniform thickness. This segmentation within a single die component achieves precise wall thickness control while maintaining relative structural simplicity.
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 method produces deep drawn cups with uniform thickness and reduced defects, enabling the use of high strength, low alloy materials and ensuring the cups are suitable for welding without additional machining, thus enhancing the integrity of pressure vessels.
Implementation Method 1
the tractrix profile region has a tractrix curvature configured based on the outer diameter of the metal blank and outer diameter of the to be formed cup
Implementation Method 2
a punch for applying a pressure to the metal blank to draw the metal blank into the top and bottom dies
Implementation Method 3
a first ironing of a sidewall thickness occurs as the metal blank is drawn through the first draw line and a second ironing of a sidewall thickness occurs as the intermediate cup is drawn through the second draw line
Data Source
Figure 1A~1B
Figure 1C
Figure 2A~2B
AI summary
An apparatus for forming a deep drawn cup can include a double die that is adapted to form a cup shape and iron a wall thickness of the drawn cup in a single operation.