HDD Base Member Casting Cavity Sealing
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Solution Overview
Problem
Hard disk drive devices filled with low-density gases like helium face leakage issues due to exposed casting cavities, and the application of labels on convex surfaces formed by die casting mold erosion leads to peeling, compromising sealing performance.
Innovation Solution
A method involving machining to form a first machined surface that seals casting cavities with a coating film, followed by secondary machining and impregnation to further seal exposed cavities, preventing gas leakage and ensuring label adhesion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If machining is performed to expose metal surface from coated surface for dimensional accuracy, then manufacturing precision is improved, but casting cavities become exposed and gas leakage occurs
Solution Approach 1:
The patent applies preliminary action by performing impregnation treatment with resin before final machining. The resin is impregnated into the metal surface while it is still coated, sealing the casting cavities in advance. This allows subsequent machining to expose the metal surface for dimensional accuracy without creating gas leakage paths, as the cavities are already sealed by the resin.
Solution Approach 2:
The patent applies local quality by selectively treating different regions of the base member. The impregnation treatment is applied to specific areas where casting cavities are present, while other areas maintain their original coated surface. This localized treatment seals cavities in critical areas without affecting the overall surface quality or requiring extensive additional processing.
2Reliability
If impregnating agent is applied to seal casting cavities, then gas leakage is suppressed, but label adhesion deteriorates due to convex portions from mold erosion
Solution Approach 1:
The patent performs preliminary machining to remove convex portions formed by mold erosion before applying the impregnating agent and subsequent label. By eliminating the convex portions in advance, the surface becomes flat and uniform, ensuring proper label adhesion. The impregnation then seals cavities on this prepared surface without creating adhesion problems.
Solution Approach 2:
The patent segments the surface treatment process into distinct steps: first removing convex portions through machining, then applying impregnation treatment to seal cavities, and finally applying labels. This segmentation allows each step to be optimized independently - machining for surface flatness, impregnation for gas sealing, and labeling for identification - without interfering with each other.
3Manufacturing precision
If gate area is reduced to increase injection pressure for high density casting, then manufacturing precision is improved, but mold erosion around gate increases
Solution Approach 1:
The patent extracts the harmful convex portions formed by mold erosion through targeted machining. By removing these eroded areas after casting, the negative effects of high injection pressure and mold erosion are eliminated, while the benefits of high density casting are retained. This extraction approach allows the use of reduced gate area for high density casting without the detrimental surface defects.
Data Source
AI summary
A base member serves as a part of a housing of a hard disk drive device. The base member includes a base body being a cast product, a first machined surface obtained by machining a portion formed with a convex portion of the base body, and a coating film covering a surface of the base body. The base body includes a coated surface obtained by covering the first machined surface with the coating film, and a second machined portion obtained by machining a part of the base body other than the first machined surface.