Wall Ironing of Polymer-Coated Can Bodies Without Thread Formation

Solution Overview

Problem

The existing processes for producing can bodies from metal sheets with polymer coatings face issues such as polymer thread formation ('hairs') and excessive shear forces during wall ironing, leading to damage and unacceptable finishes.

Innovation Solution

A process using a punch with a smooth, gradual diameter transition and optimized wall-ironing ring angles, along with specific polymer coating properties, to prevent hair formation and ensure smooth deformation, eliminating the need for external cooling and reducing the risk of scuffing.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If wall ironing is performed on polymer-coated metal sheets using conventional punches, then the can body is formed, but polymer threads (hairs) are pinched and formed at the open end of the can body

Engineering Contradiction:

Improvecan body productionVSAvoidpolymer thread formation

Core Design Contradiction:

ProductivityVSObject-generated harmful factors

Solution Approach 1:

The punch transition portion is designed in advance with a specific gradual curvature radius to prevent polymer thread formation before it occurs during the ironing process. This preliminary geometric design ensures smooth material flow and prevents pinching of the polymer coating at the can body open end.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The invention changes the geometric parameters of the punch, specifically the transition portion curvature radius, to optimize the deformation process. By controlling the curvature radius to be between 0.5-5mm, the material flow is smoothed out, preventing polymer thread formation while maintaining production efficiency.

Inventive Principle:

Principle #35Parameter changes

2Productivity

If conventional wall ironing is performed, then the can body is formed, but excessive shear forces damage the polymer coating causing scuffing or rupture

Engineering Contradiction:

Improvewall ironing processVSAvoidpolymer coating integrity

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The invention changes the geometric parameters of the punch, specifically the transition portion curvature radius, to optimize the deformation process. By controlling the curvature radius to be between 0.5-5mm, the material flow is smoothed out, preventing polymer thread formation while maintaining production efficiency.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The transition portion of the punch is designed with a curved, spherical-like geometry instead of sharp edges or abrupt transitions. This curvature distributes the shear forces more evenly across the polymer coating, preventing localized stress concentrations that would cause scuffing or rupture.

Inventive Principle:

Principle #14Spheroidality (Curvature)

3Device complexity

If abrupt diameter transitions are used in the punch, then the punch structure is simple, but discontinuities cause disturbances in the wall ironing process and polymer layer damage

Engineering Contradiction:

Improvepunch structureVSAvoiddeformation smoothness

Core Design Contradiction:

Device complexityVSManufacturing precision

Solution Approach 1:

The transition portion of the punch is designed with a curved, spherical-like geometry instead of sharp edges or abrupt transitions. This curvature distributes the shear forces more evenly across the polymer coating, preventing localized stress concentrations that would cause scuffing or rupture.

Inventive Principle:

Principle #14Spheroidality (Curvature)

Solution Approach 2:

The punch is designed with different geometric characteristics in different zones: the transition portion has a specific curvature radius (0.5-5mm) to ensure smooth deformation, while other portions of the punch maintain their functional geometry. This localized optimization ensures smooth deformation without unnecessarily complicating the overall punch structure.

Inventive Principle:

Principle #3Local quality

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 process effectively prevents hair formation, maintains the integrity of the polymer coating, and achieves a smooth deformation behavior, resulting in high-quality can bodies without the need for external coolant or additional cleaning steps.

Implementation Method 1

the cup is then deep-drawn into a cup which has a polymer layer at least on the outside, after which this cup is formed into a can body by wall ironing

Methodology Applied

Scientific EffectPlastic deformation: Plasticity

Data Source

PatentUS11407022B2Process and apparatus for the production of a can body by wall ironing

Publication Date: 2022.08.09 TATA STEEL IJMUIDEN BV

AI summary

A process for the production of a can body including a base and a tubular body from sheet metal which is coated on at least one side with a polymer layer, in which process, firstly, a round disc is produced from the sheet metal, which disc is then deep-drawn into a cup which has a polymer layer at least on the outside, after which this cup is formed into a can body by wall ironing, the wall ironing taking place in a single stroke by moving the cup successively through a redraw die and one or more wall-ironing rings.