Segmented Punching Crown With Undercut For Multi-Layer Sheet Metal
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Solution Overview
Problem
Punching holes in multi-layer metal sheets, particularly in vehicle body panels, is inefficient due to high forces required and the risk of the punch getting stuck, leading to tool wear and increased costs, as the high-strength steel intermediate layer does not deform and the softer cover layers like aluminum can cause the punch to jam and break.
Innovation Solution
A punch design with an undercut, where the punch is divided into two parts, with the front part having a larger diameter than the rear, allowing it to fall out after punching, reducing jamming risks and incorporating a punch mandrel with a tip to ease material displacement, and a punching crown made of hardened steel for reduced costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If high forces are applied to punch through thick multi-layer sheet metal, then the punching capability is improved, but the risk of punch jamming and breakage increases
Solution Approach 1:
The punch is divided into multiple segments: a front punching portion with larger diameter for cutting, a intermediate portion with smaller diameter forming an undercut, and a rear portion. This segmentation allows the punched material to be retained in the front portion while the intermediate portion can be withdrawn, preventing jamming during retraction
Solution Approach 2:
The punch design incorporates an undercut geometry where the intermediate portion has a smaller diameter than the front punching portion. This dimensional change creates a tapered retention zone that holds the punched slug during the punching process but allows easy withdrawal during retraction, solving the jamming problem
2Strength
If the punch is made of highly hardened steel to prevent breakage, then the strength is improved, but the wear resistance decreases and tool life is reduced
Solution Approach 1:
The punch is segmented into a front punching portion made of highly hardened steel for strength and wear resistance, and a rear portion that can be made of different material. This allows the critical cutting edge to have optimal hardness while the rest of the tool can be optimized for other properties
Solution Approach 2:
The front punching portion is designed as a replaceable component that can be worn or damaged independently of the main punch body. This allows replacement of only the worn cutting edge rather than the entire expensive punch tool, effectively extending tool life
3Device complexity
If a single-part punch design is used, then the device complexity is reduced, but the risk of punch jamming increases
Solution Approach 1:
The punch is divided into functional segments with different diameters along its length, creating an undercut geometry. This segmentation is achieved through simple geometric design rather than physical separation, maintaining structural simplicity while preventing jamming
Solution Approach 2:
Instead of making the punch uniformly thick for strength, the design inverts the expectation by making the intermediate portion thinner than the front portion. This creates the undercut that prevents material from jamming around the punch during retraction
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 allows for efficient punching of thick multi-layer sheets without jamming, significantly reducing the risk of punch breakage and tool wear, and lowers the cost per hole by extending the tool's lifespan and minimizing material buildup on the punch.
Implementation Method 1
the tip of the punching mandrel first penetrates the piece of sheet metal and begins to displace the material. The punching forces are significantly reduced by the tip of the punching mandrel, as this has a positive effect on the flow properties of the object to be punched
Implementation Method 2
The punching crown consists in particular of hardened steel, for example high-speed steel, and can be coated with a hard material layer, for example with a nitrite layer
Data Source
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AI summary
The invention relates to a method and a device for punching holes in body panels, wherein a punching die (1)l has a removable punching crown (5) which falls out on the die side after completion of the punching process.