Sheet-Metal Preform Calibration for Flangeless Spring-Back Control
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Solution Overview
Problem
Existing methods for producing sheet-metal parts without flanges are inadequate, as they lack a satisfactory concept for calibrating parts with substantial regions without welding flanges, leading to issues like spring-back and tool damage.
Innovation Solution
A method involving two stages: preforming a sheet into a metal preform with an open profile and flangeless portions, and final forming using a calibration tool with a punch shoulder, where the edge of the preform rests on the punch shoulder to achieve compressive stress superposition and prevent clamping.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional calibration tools with side slides are used for sheet-metal parts without flanges, then the calibration process cannot be properly performed, but using preforms that substantially correspond to final geometry requires complex tool design with active faces at both preform and calibration tools
Solution Approach 1:
Instead of having the preform correspond to final geometry with complex tooling, the invention inverts the approach: the preform is designed with an open profile and flangeless portions that will rest on the punch shoulder during calibration. This simplifies the calibration tool structure while enabling proper calibration of flangeless sheet-metal parts.
Solution Approach 2:
The preform is preliminarily shaped with specific features (open profile, flangeless portions) that prepare it for the calibration process. The surplus sheet material is distributed in advance to enable compressive stress superposition during calibration, eliminating the need for complex side slide mechanisms.
2Manufacturing precision
If the calibration tool is closed during calibration of flangeless portions, then the metal preform may be clamped between the calibration punch and calibration die, but this leads to damage of the final-formed sheet-metal part and/or calibration tool
Solution Approach 1:
The punch shoulder acts as an intermediary element between the calibration punch and the metal preform. The flangeless portion of the preform rests on this intermediate surface, which distributes the compressive forces and prevents direct clamping between the punch and die that would cause damage.
Solution Approach 2:
The calibration tool is designed with a specific local feature (punch shoulder) that provides a resting surface for the flangeless portion. This localized structural modification enables proper force distribution and prevents damage without affecting the overall calibration process.
3Stress or pressure
If side slides are brought up to the calibration punch via wedge drivers, then compressive stress superposition is achieved for parts with flanges, but there is no satisfactory concept for parts without flanges
Solution Approach 1:
The punch shoulder design provides a universal solution that works for both flanged and flangeless portions of sheet-metal parts. The same calibration tool structure can accommodate different part geometries without requiring separate mechanisms like side slides for flangeless portions.
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 approach enables the production of precisely dimensioned, flangeless sheet-metal parts with a low wing opening angle, reducing the risk of spring-back and tool damage while ensuring accurate calibration.
Implementation Method 1
the surplus sheet material in the metal preform is compressed by a relative movement between the calibration punch and the calibration die
Implementation Method 2
the edge of the metal preform present at least in the flangeless portion comes into contact with a punch shoulder of the calibration punch, rests thereon and is pressure-loaded
Data Source
AI summary
The present disclosure provides a method and a device for producing sheet-metal parts with substantially reduced spring-back.