Lost Pattern With Layered Recesses For Gas Evacuation
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Solution Overview
Problem
The existing foundry molding techniques using lost models often result in defects such as 'puff holes' or porosity in metal parts, particularly in complex shapes like engine cylinder heads, due to gas release during the casting process, which increases the scrap rate.
Innovation Solution
Incorporating closed recesses in the lost model, defined by multiple strata, to better channel gas evacuation and reduce gas release, especially in thick areas prone to blowhole formation, thereby improving the quality of the metal parts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If lost patterns are made from stacked layers of sublimable material, then complex shapes can be formed, but gas release during casting causes blowholes and porosity defects
Solution Approach 1:
The lost pattern is divided into multiple stacked layers of sublimable material, each layer being moldable independently. This segmentation allows complex shapes to be formed by assembling simpler layers, while the layered structure itself creates controlled gas evacuation pathways that prevent blowholes and porosity defects during metal casting.
Solution Approach 2:
The stacked layer structure acts as an intermediary mechanism between the sublimable material and the molten metal. The layers provide controlled gas release pathways that mediate the interaction between vaporizing polystyrene and the aluminum casting, preventing direct gas entrapment that would cause blowholes while still allowing complete pattern vaporization.
2Strength
If thick areas are used in lost patterns, then structural integrity is improved, but gas release in these areas increases blowhole formation
Solution Approach 1:
Different regions of the lost pattern have different layer configurations tailored to local requirements. Thick areas that require structural integrity are constructed with multiple stacked layers that provide both the necessary strength and controlled gas evacuation pathways, while thinner areas use fewer layers. This local optimization ensures structural integrity where needed while preventing blowhole formation through controlled gas release.
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 use of closed recesses in the lost model significantly reduces the occurrence of blowholes and scrap rates in metal parts, particularly in complex shapes like engine cylinder heads, by effectively managing gas release during the casting process.
Implementation Method 1
The lost-wax casting is made of a sublimable material, such as polystyrene, polyurethane, or polyethylene. The lost-wax casting is placed inside a sand matrix, which receives the molten metal. Upon contact with the molten metal, the sublimable material is sublimated, leaving the metal behind.
Implementation Method 2
Incorporating closed recesses in the lost model, defined by multiple strata, to better channel gas evacuation and reduce gas release, especially in thick areas prone to blowhole formation
Data Source
Figure 1~2
Figure 3
AI summary
The invention relates to a lost pattern (M) intended for use in casting for obtaining metal parts and comprising a stack of layers (1,2,3,4,5) assembled together by glueing. Said lost pattern comprises at least one enclosed recess (6,7) which is jointly defined by two recess portions belonging respectively to two successive layers (3,4), termed respectively the lower layer (3) and the upper layer (4), of the stack.