Magnetic Disk Glass Substrate Inner Hole Roundness Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
High-speed rotation of magnetic disks in HDDs leads to increased fluttering due to slight distortions caused by the spindle's thermal expansion mismatch with the glass substrate, resulting in inaccurate data track positioning and potential mechanical issues.
Innovation Solution
A magnetic-disk glass substrate with a circular hole having a roundness of 1.5 μm or less and a specific thermal expansion coefficient, combined with precise three-dimensional shape evaluation and surface roughness control, to minimize distortion and ensure surface contact with the spindle, reducing fluttering.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If the roundness of the inner hole is reduced to 1.5 μm or less, then the magnetic disk stability is improved, but the manufacturing precision requirement becomes more stringent
Solution Approach 1:
The patent applies parameter changes by establishing specific numerical thresholds for inner hole roundness (1.5 μm or less) and three-dimensional shape precision to resolve the contradiction between magnetic disk stability and manufacturing precision requirements
Solution Approach 2:
The patent replaces traditional mechanical measurement methods with three-dimensional shape measurement technology to achieve more precise characterization of the inner hole geometry, enabling better control of both stability and manufacturing precision
2Stability of the object's composition
If the three-dimensional shape precision of the inner hole is improved, then the fluttering is reduced, but the measurement and evaluation complexity increases
Solution Approach 1:
The patent replaces conventional two-dimensional roundness measurement with three-dimensional shape measurement technology, enabling comprehensive evaluation of the inner hole geometry including depth, diameter variations, and surface irregularities that affect fluttering
Solution Approach 2:
The patent transitions from two-dimensional roundness measurement to three-dimensional shape measurement, adding the depth dimension and enabling more comprehensive assessment of the inner hole's geometric precision and its impact on magnetic disk stability
3Reliability
If the surface roughness of the inner hole is controlled, then the contact with spindle is improved, but the manufacturing complexity increases
Solution Approach 1:
The patent applies parameter changes by establishing specific surface roughness thresholds for the inner hole to ensure reliable contact with the spindle while maintaining manufacturing feasibility
Solution Approach 2:
The patent applies local quality by controlling surface roughness specifically at the inner hole location where spindle contact occurs, rather than uniformly across the entire magnetic disk substrate, thereby improving reliability while minimizing manufacturing complexity
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 controlled substrate design significantly reduces fluttering during high-speed rotation, enhancing data track positioning accuracy and mechanical stability of the magnetic disk.
Implementation Method 1
the spindle's thermal expansion mismatch with the glass substrate
Data Source
AI summary
A magnetic-disk glass substrate has a circular hole at a center, and includes a pair of main surfaces and a side wall surface orthogonal to the main surfaces. A roundness of the circular hole is 1.5 μm or less. A difference between a maximum value and a minimum value of radii of three inscribed circles that are respectively derived from outlines in the circumferential direction at three positions spaced apart by 200 μm in a substrate thickness direction on the side wall surface of the circular hole is 3.5 μm or less.