Open-Cavity Composite Extrusion for Deep Blind Hole Forming
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Solution Overview
Problem
Traditional forward and backward extrusion methods are limited in forming components with deep blind holes due to shallow hole formation and instability issues with large height-diameter ratios, which restrict the length-diameter ratio of the inner hole in alloy steel.
Innovation Solution
A composite forming method using an open inner mould cavity, incorporating both backward and forward extrusion processes with specific ejector pin configurations and clearance fits to manage metal flow and deformation, allowing for increased length-diameter ratios without mould instability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If traditional backward extrusion is used, then the forming process is simple, but the hole depth is limited and the length-diameter ratio is only about 3
Solution Approach 1:
The forming process is divided into two separate extrusion operations: backward extrusion first to create a shallow hole, then forward extrusion to deepen the hole. This segmentation allows each operation to be optimized independently, achieving a total length-diameter ratio of 6 or more while keeping individual process steps manageable and stable.
Solution Approach 2:
The backward extrusion is performed as a preliminary action to create an initial hole structure before the forward extrusion. This preliminary hole formation provides a foundation for the subsequent deepening operation, enabling the final product to achieve greater depth than either operation could accomplish alone.
2Length of moving object
If traditional forward extrusion is used to increase blind hole depth, then the hole depth increases, but the core mould becomes unstable when the height-diameter ratio is too large
Solution Approach 1:
The deep hole formation is segmented into two parts: backward extrusion creates the initial shallow hole with stable mould conditions, and forward extrusion then deepens the hole. By splitting the total depth requirement across two operations with different mould configurations, the core mould in each operation maintains a manageable height-diameter ratio and remains stable.
Solution Approach 2:
Instead of using only forward extrusion to create the deep hole (which causes core mould instability), the invention uses backward extrusion first to create the initial hole structure, then follows with forward extrusion. This inverted sequence allows the core mould to remain stable throughout the process while achieving the desired deep hole geometry.
3Length of moving object
If traditional forward and backward extrusion methods are used, then the process is conventional and simple, but they cannot meet the requirement of forming components with blind holes having certain depth
Solution Approach 1:
The manufacturing process is segmented into backward extrusion followed by forward extrusion, with each operation using appropriately designed moulds. This segmentation enables the formation of deep blind holes (length-diameter ratio of 6 or more) that cannot be achieved by traditional single-operation methods, while keeping each individual operation relatively simple and manufacturable.
Solution Approach 2:
The invention uses a composite forming approach combining two different extrusion methods (backward and forward) in sequence, rather than relying on a single conventional method. This composite process integrates the advantages of both techniques to achieve deep hole formation while maintaining manufacturing feasibility.
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 method enhances the length-diameter ratio of blind holes significantly by adding a wall thickness reduction step in backward extrusion and incorporating novel necking in forward extrusion, improving the forming capability beyond conventional limits.
Implementation Method 1
the male mould continues to go down and press the billet down to fill the bottom of the cavity, the metal flows upward along the inner wall of the core mould
Implementation Method 2
The outer lower ejector pins evenly distributed along the central axis drive the female mould to move upward
Implementation Method 3
a punch of the male mould passes through an inner hole of a first male mould sleeve and forms a clearance fit with the first male mould sleeve
Implementation Method 4
the wall thickness of the metal is reduced by the stepped surface of the core mould
Data Source
AI summary
The present invention discloses a forward and backward extrusion composite forming method using a mould having an open inner cavity, including the following steps: (1) the structural design and assembly of the forward and backward extrusion composite mould having the open inner cavity; (2) the preparation of the initial billet; and (3) forward and backward extrusion composite forming. The present invention can greatly improve the length-diameter ratio of the blind hole and is widely used in alloy steel, aluminum alloy, magnesium alloy, copper alloy and other components.