Bunter Indicia Cold Forming Process
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Solution Overview
Problem
Existing methods for forming raised indicia on bunters used for ammunition cartridge cases result in surface roughness and require substantial time, with EDM and engraving techniques not providing a workhardened surface.
Innovation Solution
A cold forming process using a bunter blank with a radial center protrusion and an outwardly rounded working face, where the blank is assembled with a hub to deform material into indicia recesses, forming raised indicia on the bunter's surface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If EDM or engraving techniques are used to form raised indicia on the bunter face, then the indicia can be formed, but the bunter face acquires considerable surface roughness that is transferred to the cartridge case
Solution Approach 1:
The patent replaces EDM (electrical discharge machining) and engraving techniques with a cold forming process. A hub with recessed indicia is pressed against the bunter blank, causing the metal to plastically deform and form raised indicia through mechanical pressure rather than electrical erosion or cutting. This substitution eliminates the surface roughness problem inherent in EDM and engraving while achieving the desired indicia formation.
Solution Approach 2:
Instead of directly forming raised indicia on the bunter face through removal or addition of material, the patent uses an inverse approach: a hub with recessed indicia is pressed into the bunter blank, and the metal flows into these recesses to create the raised features. This inversion of the forming concept allows the smooth surface to be maintained while achieving the raised indicia.
2Productivity
If EDM or engraving techniques are used to form raised indicia on the bunter, then the indicia can be created, but the process requires a substantial amount of time
Solution Approach 1:
The hub with recessed indicia is prepared in advance, and the bunter blank is cold formed in a single pressing operation. This preliminary preparation of the hub mold allows the indicia to be formed rapidly without the time-consuming step-by-step material removal or deposition required by EDM and engraving processes.
Solution Approach 2:
The replacement of slow EDM and engraving processes with a rapid cold forming operation significantly reduces the time required to form indicia. The mechanical pressing operation forms all indicia simultaneously in one step rather than requiring sequential processing.
3Strength
If EDM or engraving techniques are used to form indicia on the bunter, then the indicia can be formed, but the bunter is not workhardened during the process
Solution Approach 1:
The cold forming process changes the physical state and mechanical properties of the bunter blank through plastic deformation. The high pressure applied during forming workhardens the metal surface, increasing its strength and durability. This parameter change in the material's mechanical state simultaneously achieves both surface hardening and precise indicia formation.
Solution Approach 2:
The substitution of non-workhardening EDM and engraving processes with a cold forming process that applies substantial mechanical pressure results in workhardening of the bunter surface. The plastic deformation inherent in cold forming naturally workhardens the metal while forming the indicia.
4Manufacturing precision
If a cold forming process is used to form raised indicia on the bunter blank, then a smooth workhardened surface is achieved, but the bunter blank requires a specific outwardly rounded configuration
Solution Approach 1:
The bunter blank is pre-formed with an outwardly rounded configuration before the cold forming operation. This preliminary shaping of the blank ensures that during the pressing operation, the metal flows uniformly into the hub recesses without creating defects or requiring complex tooling. The pre-configured blank simplifies the overall process despite the additional initial forming step.
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 achieves a smooth, workhardened surface with fully formed indicia while minimizing distortion, offering a faster and more efficient method compared to traditional techniques.
Implementation Method 1
applying enough force to the thus assembled bunter blank and hub that material defining the outwardly rounded configuration of the bunter blank's working face is deformed into the hub's indicia recesses so as to form raised indicia on the working face
Implementation Method 2
The process achieves a smooth, workhardened surface with fully formed indicia
Data Source
Figure 1A~1B
Figure 2A~2B
Figure 3A~3C
AI summary
The invention provides methods for making bunters used to form headstamp indicia into ammunition cases. The invention also provides bunter blanks that are specially configured to yield high quality bunters.