Double-Die Deep Drawn Cup Forming With Integrated Wall Ironing
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Solution Overview
Problem
Conventional deep drawing methods struggle with forming uniform thickness and avoiding defects in high strength, low alloy metals, particularly in pressure vessels, due to microcracking and material hardening during the drawing process, necessitating custom materials and secondary machining that can introduce further defects.
Innovation Solution
A double die configuration using a top die with a tractrix profile and a bottom die with specific draw lines, allowing simultaneous shaping and ironing of metal blanks into deep drawn cups, utilizing high strength low alloy materials like carbon steel, and a subsequent smash operation to prepare cups for welding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional deep drawing methods are used on high strength low alloy metals, then the drawing process can be completed, but microcracking and material hardening occur causing non-uniform thickness and defects
Solution Approach 1:
The deep drawing process is segmented into two distinct stages: first forming the cup shape, then ironing the walls to achieve uniform thickness. This segmentation allows each stage to be optimized independently, preventing microcracking during shaping and achieving uniform thickness during the separate ironing stage.
Solution Approach 2:
The cup shape is formed in advance as an intermediate product before the ironing operation. This preliminary action allows the material to be shaped first, then uniformly thinned in a controlled manner, avoiding the simultaneous stress that causes microcracking in conventional single-stage drawing.
2Ease of manufacture
If conventional deep drawing is used to form pressure vessel components, then the cup shape is formed, but secondary machining is required which introduces additional defects
Solution Approach 1:
The ironing operation is merged with the deep drawing process to combine shaping and thickness uniformization in a integrated flow. This eliminates the need for separate secondary machining operations that would introduce additional defects, achieving both form and uniform thickness in one continuous process.
3Strength
If high strength low alloy materials are used in conventional drawing, then material strength is achieved, but the drawing process induces microcracking and requires custom materials
Solution Approach 1:
The process segments forming and ironing into separate stages, allowing high strength low alloy materials to be shaped without the excessive stress of single-stage drawing. The subsequent ironing stage uniformly thins the walls in a controlled manner, preventing microcracking while maintaining the material's high strength properties.
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 achieves uniform cup thickness and reduces defects by thinning and shaping in a single operation, enabling the use of high strength low alloy materials without secondary machining, and prepares cups for strong welds by flattening the top edge without inducing new defects.
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 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
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.