Long Cartridge Case Forming with Backward and Hooker Extrusion
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Solution Overview
Problem
The traditional method of manufacturing rifle cases involves multiple steps, high scrap ratios, energy consumption, and dimensional variability, with significant stress on tooling and space requirements, necessitating a more efficient and less stressful process.
Innovation Solution
A method involving cutting a blank from solid round metal wire, performing backward extrusion to create a hollow sidewall, and using modified Hooker extrusions to achieve the desired wall thickness without additional backward extrusions, reducing forming load and energy consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If multiple backward extrusions are used to form long cartridge cases, then the desired hollow shape and wall thickness can be achieved, but the forming load and stress on tooling increase significantly
Solution Approach 1:
The patent divides the wall thickness reduction into multiple sequential Hooker extrusion steps rather than attempting to achieve the final thickness in a single backward extrusion. Each Hooker extrusion step progressively reduces the wall thickness by a controlled amount, distributing the total deformation across multiple lower-force operations. This segmentation of the forming process allows achievement of precise wall thickness while keeping individual step loads manageable.
Solution Approach 2:
The patent inverts the conventional sequence by performing backward extrusion first to create the basic hollow shape, then using forward Hooker extrusions to reduce wall thickness. This reversal of the traditional approach (which would use forward extrusions to create the hollow shape followed by backward extrusions for thickness control) allows the tooling to work in tension during thickness reduction rather than compression, significantly reducing tooling stress.
2Length of moving object
If conventional cup and draw process is used to manufacture rifle cases, then long cartridge cases can be produced, but numerous wash and annealing steps are required between drawing operations
Solution Approach 1:
The patent employs continuous cold forming operations (backward extrusion followed by sequential Hooker extrusions) to transform the solid blank into the final hollow product with controlled wall thickness. This continuous cold working process eliminates the need for intermittent annealing and washing steps that are mandatory in hot working conventional cup and draw processes, thereby reducing the total number of processing steps and equipment requirements while maintaining the ability to produce long cartridge cases.
3Manufacturing precision
If multiple backward extrusions are performed to achieve desired wall thickness, then hollow parts can be formed, but tool life decreases due to high forces involved
Solution Approach 1:
The patent inverts the conventional sequence by performing backward extrusion first to create the basic hollow shape, then using forward Hooker extrusions to reduce wall thickness. This reversal of the traditional approach (which would use forward extrusions to create the hollow shape followed by backward extrusions for thickness control) allows the tooling to work in tension during thickness reduction rather than compression, significantly reducing tooling stress and extending tool life while maintaining precise wall thickness control.
Solution Approach 2:
The patent changes the fundamental parameter of extrusion direction from backward (compressive) to forward (tensile) for the wall thickness reduction steps. This parameter change transforms the stress state on the tooling from high-compression to lower-tension, thereby reducing tool wear and extending tool life while achieving the same wall thickness precision through the Hooker extrusion mechanism.
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
Improves tool life and allows for the use of smaller, faster machines with reduced forming loads and energy consumption by up to 50% and 40%, respectively, while maintaining tool integrity.
Implementation Method 1
backward extruding an axial hole in the blank to produce a hollow sidewall with a thickness
Implementation Method 2
backward extruding an axial hole in the blank to produce a hollow sidewall
Implementation Method 3
The forward extrusion of the outside diameter of a hollow part with a mandrel used to maintain the inside diameter of the extruded part
Implementation Method 4
reducing the sidewall thickness by using a Modified Hooker extrusion
Data Source
Figure 1
Figure 2~3
AI summary
A method of forming a closed end metal tube comprising cutting a blank 10 from a solid round metal wire, backward extruding an axial hole 11 in the blank 10 to produce a hollow sidewall 12 with a thickness, and reducing the sidewall thickness by using one or more Modified Hooker extrusions.