Western Digital Technologies, Inc.

Boworn Panyavoravaj

Brian P Rigney

Yakov M Lifchits

Jern Khang Tan

Steven C Smith

Chaisit Siricharoenchai

Amar Nath

Maneerat Suthampitak

A method is disclosed for selecting a rotation speed when servo writing a disk of a disk drive. A gas is injected into a head disk assembly (HDA) comprising the disk. The disk is rotated while reading data from the disk using a head to generate a read signal. A fly height modulation (FHM) of the head is measured in response to the read signal. When the FHM exceeds a threshold, the rotation speed is adjusted. The disk is servo written at the adjusted rotation speed. After servo writing the disk and evacuating the gas from the HDA, the disk is rotated at a normal rotation speed lower than the adjusted rotation speed used to servo write the disk, and manufacturing data is written to the disk at the normal rotation speed.

Adjusting rotation speed of disk to reduce fly height modulation when servo writing in gas

A disk drive is disclosed comprising a head actuated over a disk comprising a plurality of spiral tracks. A first sync frame is first opened in response to a first frame offset during a first revolution of the disk, wherein the first sync frame corresponds to the head approaching a first sync mark in a first spiral track crossing. A first sync frame position error signal (PES) is generated representing a difference between a target framing of the first sync frame around the first sync mark and a detected framing of the first sync frame around the first sync mark. The first frame offset is adjusted in response to the first sync frame PES, and during a second revolution of the disk the first sync frame is second opened in response to the adjusted first frame offset.

Disk drive centering sync frames on sync marks of a spiral track

A method to balance spindles in a plurality of disk drives is disclosed and claimed. An initial imbalance and initial phase for one of the plurality of disk drives is determined, the determination depending upon an amplitude and phase calibration. One of a plurality of balancing masses is selected based on the initial imbalance and attached at an angular position selected based upon the initial phase. A final imbalance after attachment is similarly determined. These determinations are repeated for each of the plurality of disk drives, with the final imbalance and the initial imbalance recorded for each. The amplitude calibration is adjusted based on a comparison of a measured distribution and a theoretical distribution of the final imbalance versus the initial imbalance.

Method to balance spindles in a plurality of disk drives

A disk drive is disclosed comprising a head actuated over a disk comprising a plurality of spiral tracks, wherein each spiral track comprises a high frequency signal interrupted by a sync mark at a sync mark interval. The head is positioned over the disk and used to read the spiral tracks to detect a plurality of spiral-to-spiral times each representing a time between consecutive spiral crossings. A velocity of the head is estimated in response to the spiral-to-spiral times, and velocity feedforward compensation values are generated from the estimated head velocity. A control signal is generated to position the head over the disk in response to the velocity feedforward compensation values. When the detected spiral-to-spiral times are substantially constant, position feedforward compensation values are initialized in response to the velocity feedforward compensation values.

Disk drive initializing position feedforward compensation with velocity feedforward compensation

A method of driving screws into a workpiece using an automatic screw driving tool having first and second components, the first component including a screw bit. The method may include steps of measuring a relative displacement between the first and second components; driving, in a first phase, a first screw partially into the workpiece at a first speed until a target relative displacement value is reached; after the first phase, driving, in a second phase, the first screw further into the workpiece at a second speed that is different than the first speed; completing the driving process for the first screw; measuring a final relative displacement of the first and second components after the first phase to determine a final relative displacement value, and updating the target relative displacement value based on the final relative displacement value.

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Bangkok, Thailand

Boworn Panyavoravaj