Head Stack Assembly Arm Notch Design for Baseplate Deformation Control
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Solution Overview
Problem
The displacement of the baseplate during ball swaging in head stack assemblies of magnetic disk drives affects the flying height and loading-unloading characteristics of magnetic heads, and reducing the fastening force to minimize this displacement increases the risk of disengagement, while increasing arm rigidity makes it heavier.
Innovation Solution
The arm's distal end portion is made less rigid than the rest by forming a notch or cut, reducing the cross-sectional area, which minimizes baseplate deformation without compromising fastening force, thereby maintaining reliable head positioning.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the fastening force between baseplate and arm is reduced to minimize baseplate displacement during ball swaging, then baseplate deformation is reduced, but the possibility of disengagement increases
Solution Approach 1:
The arm is designed with non-uniform rigidity: the distal end portion has reduced rigidity (smaller cross-sectional area) to minimize baseplate deformation during ball swaging, while the proximal end and other portions maintain sufficient rigidity to provide reliable fastening force and prevent disengagement. This local differentiation of mechanical properties resolves the contradiction between minimizing deformation and ensuring reliability.
2Manufacturing precision
If the rigidity of the arm is increased to reduce displacement during ball swaging, then baseplate deformation is reduced, but the arm becomes heavier
Solution Approach 1:
Instead of uniformly increasing the arm's rigidity throughout, the invention applies increased rigidity only where necessary (proximal end and body portions for fastening stability) while reducing rigidity at the distal end portion to minimize baseplate deformation. This localized approach achieves the desired precision without the penalty of overall weight increase.
Solution Approach 2:
The arm is segmented into portions with different rigidity characteristics: a proximal end portion for reliable fastening, a body portion for structural support, and a distal end portion with reduced rigidity for minimal deformation during swaging. This segmentation allows each portion to be optimized for its specific function without compromising the whole.
3Manufacturing precision
If the cross-sectional area of the arm distal end is reduced to minimize baseplate deformation, then manufacturing precision is improved, but the fastening force may be compromised
Solution Approach 1:
The arm's cross-sectional area is locally optimized: the distal end portion has a smaller cross-sectional area to minimize baseplate deformation during ball swaging, while the proximal end and body portions maintain larger cross-sectional areas to provide sufficient fastening force. This local differentiation ensures both precision and force requirements are met simultaneously.
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 configuration reduces baseplate deformation by 25% while maintaining the fastening torque, enhancing the reliability of the head stack assembly and hard disk drive by stabilizing the flying height of the magnetic heads.
Implementation Method 1
an annular protrusion formed on the baseplate is crushed against the arm and plastically deformed so that these two portions are joined together
Data Source
AI summary
According to an embodiment, a head stack assembly includes an arm including a swaged seat surface with swaged hole, a load beam supporting a head, and a baseplate secured to a proximal end portion of the load beam, including an annular protrusion secured to the swaged hole of the arm by swaging, and secured to the swaged seat surface. The arm includes a distal end portion located on a longitudinal end side of the arm with respect to the center of the swaged hole and being less rigid than the other portion of the arm around the swaged hole.