Punching Tool Crown Geometry for Sheet Metal Flatness
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Solution Overview
Problem
Sheet metal deformation during punching on punching machines leads to inaccuracies and increased tool wear due to tensile stress, which existing methods like crowned dies and post-processing straightening machines cannot fully address, especially for slot-type tools and already formed sheets.
Innovation Solution
A punching machine design with a C-frame structure, hydraulic ram, and a specialized tool set featuring a lower tool holder and stripper with varying stiffness areas to reduce tensile stress by bending the sheet metal upwards, using a disc-shaped stripper with a recess to distribute deformation and generate compressive stresses, thereby maintaining sheet metal flatness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If crowned dies are used to reduce sheet metal deformation, then manufacturing precision is improved, but device complexity and production cost increase due to special cylindrical grinding machines required
Solution Approach 1:
The patent applies local quality by creating a crown only in the central area of the punch tool, while the peripheral areas remain flat. This is achieved by selectively removing material from the central region through controlled punching operations, resulting in a localized curved surface that generates the necessary compressive stress exactly where needed to counteract tensile stress and maintain sheet metal flatness, without requiring complex full-surface crowning machinery
Solution Approach 2:
The patent implements self-service by enabling the punching tool to automatically generate its own crown geometry through a series of controlled punching operations. The tool punches its own shaping features into the workpiece, and through repeated operations with varying parameters, the central area naturally forms a crowned shape that provides the stress distribution needed for flat sheet metal output, eliminating the need for external specialized grinding equipment
2Manufacturing precision
If post-processing straightening machines are used to restore sheet metal flatness, then manufacturing precision is improved, but productivity decreases due to additional machines and operations required
Solution Approach 1:
The patent applies preliminary action by pre-shaping the punch tool with a crowned geometry before the actual punching operation. This pre-configured crown on the punch tool automatically generates the necessary compressive stress during punching to counteract tensile stress and prevent sheet metal deformation from occurring in the first place, eliminating the need for subsequent straightening operations and maintaining high productivity
Solution Approach 2:
The patent merges the functions of punching and stress control into a single integrated operation. By incorporating the crown geometry directly onto the punch tool, the same tool that performs the cutting function also simultaneously provides the stress distribution needed to maintain sheet metal flatness, combining what would traditionally require separate punching and straightening machines into one efficient process
3Manufacturing precision
If active stripper is used to press sheet metal down against die, then manufacturing precision is improved, but device complexity increases
Solution Approach 1:
The patent extracts the stress control function from separate auxiliary devices like active strippers and integrates it directly into the punch tool itself. By incorporating the crown geometry onto the punch, the stress distribution function is built into the primary tooling, eliminating the need for additional active stripper mechanisms and reducing overall tooling complexity while maintaining manufacturing precision
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 effectively reduces tensile stress and maintains sheet metal flatness during punching, reducing inaccuracies and tool wear, and can be applied to various sheet metal types without the need for additional machines or complex processes.
Implementation Method 1
a hydraulic unit (3) with which a ram (4) is hydraulically driven
Implementation Method 2
the metal sheet (15) is bent upwards and thereby plastically deformed
Data Source
Figure 1
Figure 2
Figure 3
AI summary
The tool kit has a deflector for a punching machine with a plunger (4) having an upper tool holder. The deflector has a section with a lower surface having areas with high rigidity and the area with lower rigidity. The areas with high rigidity are arranged relative to a central axis outside another area with low rigidity. A tool insert has a tool upper part (16) and tool lower part. The tool upper part has a cutter, and the tool lower part has an opening complementary to the cutter. An independent claim is also included for a method for correcting the deformation of a plate processed in a punching machine by stamp.