Glass Substrate End Face Grinding for Magnetic Discs
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Solution Overview
Problem
Conventional glass substrate manufacturing methods for magnetic discs result in undulations on the outer peripheral end face, leading to particle generation, corrosion, and thermal asperity failures, which become significant issues with increasing recording density and capacity, and are difficult to eliminate within the required processing time for large-scale, cost-effective production.
Innovation Solution
A method involving the formation of first and second undulations on the outer peripheral end face of the glass substrate, where the second undulations have a different wavelength and are intentionally offset to cancel out the first undulations, using controlled rotational frequencies of the grindstone and substrate, allowing for short processing times and high roundness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a rotating grindstone is used to ground the outer peripheral end face of the glass substrate, then the end face can be smoothed to prevent chip generation, but undulations with fixed wavelength are formed on the end face
Solution Approach 1:
The invention applies periodic action by changing the rotational frequency of the grindstone in a specific sequence. First, the grindstone rotates at a frequency that generates undulations with a first wavelength to smooth the end face. Then, the rotational frequency is changed to generate undulations with a second wavelength that is different from the first. This periodic change in grinding conditions allows the second undulations to cancel out the first undulations, achieving a flat end face without residual periodic waves.
Solution Approach 2:
The invention employs parameter changes by modifying the rotational frequency parameter of the grindstone during the grinding process. The rotational frequency is changed from a first frequency (generating first undulations) to a second frequency (generating second undulations with different wavelength). This parameter change enables the transformation of the end face surface state from having undulations to being flat, resolving the contradiction between smoothing and flatness.
2Object-affected harmful factors
If the undulations on the outer peripheral end face are eliminated by conventional methods, then particle generation is prevented, but the processing time becomes too long for cost-effective mass production
Solution Approach 1:
The invention applies preliminary action by intentionally generating first undulations on the end face during the initial grinding stage. These first undulations are then eliminated in a subsequent stage by generating second undulations with different wavelength that cancel out the first ones. This preliminary generation of controlled undulations allows for their systematic elimination, achieving a particle-free end face within a reasonable processing time suitable for mass production.
Solution Approach 2:
The invention converts the harmful effect of undulations into a beneficial process. Instead of trying to avoid undulation generation, the method intentionally generates first undulations with a specific wavelength, then uses second undulations with a different wavelength to cancel them out. This approach transforms the potential harm of undulations (surface irregularities leading to particle generation) into a controlled process that ultimately eliminates particles while maintaining efficient processing time.
3Productivity
If the rotational frequency of the grindstone is increased to reduce processing time, then productivity improves, but the undulations become more pronounced and harder to eliminate
Solution Approach 1:
The invention applies segmentation by dividing the grinding process into two distinct stages with different rotational frequencies. The first stage uses a higher rotational frequency to quickly generate first undulations and remove material, improving productivity. The second stage uses a different rotational frequency to generate second undulations that cancel out the first ones, ensuring precision. This segmentation of the grinding process allows both high processing speed and accurate undulation control.
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 approach effectively eliminates undulations on the glass substrate's outer peripheral end face, preventing particle generation and corrosion, thereby enhancing the quality of the magnetic disc and enabling efficient, cost-effective mass production.
Implementation Method 1
a forming step of pressing a rotating grindstone against an outer peripheral end face while the glass substrate is rotated, thereby forming an outer peripheral end
Data Source
AI summary
The invention aims at providing a method for manufacturing a glass substrate for a magnetic disc capable of eliminating undulations of an outer peripheral end face of a glass substrate in a short processing time, and obtaining high roundness. In a method for manufacturing a disc-like glass substrate for a magnetic disc, the method includes a forming step of pressing a rotating grindstone against an outer peripheral end face while the glass substrate is rotated, thereby forming an outer peripheral end. In the forming step, processing is performed using a first condition (S106) on which first undulations are formed and a second condition (S108) on which second undulations having a different wavelength from the first undulations are formed.