Abstract:
An automated system for setting the linear distance from a mounting surface of a pivot cartridge to critical features on actuator arms is disclosed. This distance is set to eliminate the tolerance incurred via normal manufacturing of these components. The system adjusts for every component to customize each actuator and/or pivot assembly to meet the functionality requirements for disk drives.

Description:
BACKGROUND OF THE INVENTION 
   1. Technical Field 
   The present invention relates in general to an improved disk drive subassembly technique and, in particular, to an improved system, method, and apparatus for disk drive actuator pivot set height tooling with active servo compensation. 
   2. Description of the Related Art 
   Data access and storage systems generally comprise one or more storage devices that store data on magnetic or optical storage media. For example, a magnetic storage device is known as a direct access storage device (DASD) or a hard disk drive (HDD) and includes one or more disks and a disk controller to manage local operations concerning the disks. The hard disks themselves are usually made of aluminum alloy or a mixture of glass and ceramic, and are covered with a magnetic coating. Typically, one to five disks are stacked vertically on a common spindle that is turned by a disk drive motor at several thousand rpm. Hard disk drives have several different typical standard sizes or formats, including server, desktop, mobile, and microdrive. 
   A typical HDD is shown in  FIG. 1 . An information storage system, such as a magnetic hard disk file or drive  111  for a computer system, has an outer housing or base  113  containing at least one magnetic disk  115 . Disk  115  is rotated by a spindle motor assembly having a central drive hub  117 . An actuator  121  comprises a plurality of parallel actuator arms  125  (one shown) in the form of a comb that is pivotally mounted to base  113  about a pivot assembly  123 . A controller  119  is also mounted to base  113  for selectively moving the comb of arms  125  relative to disk  115 . 
   Each arm  125  has extending from it at least one cantilevered load beam and suspension  127 . A magnetic read/write transducer or head is mounted on a slider  129  and secured to a flexure that is flexibly mounted to each suspension  127 . The read/write heads magnetically read data from and/or magnetically write data to disk  115 . The level of integration called the head gimbal assembly is head and the slider  129 , which are mounted on suspension  127 . The slider  129  is usually bonded to the end of suspension  127 . The head is typically pico size and formed from ceramic or intermetallic materials. The head also may be femto size and is pre-loaded against the surface of disk  115  by suspension  127 . 
   Suspensions  127  have a spring-like quality which biases or urges the air bearing surface of the slider  129  against the disk  115  to enable the creation of the air bearing film between the slider  129  and disk surface. A voice coil  133  housed within a conventional voice coil motor magnet assembly  134  is also mounted to arms  125  opposite the head gimbal assemblies. Movement of the actuator  121  (indicated by arrow  135 ) by controller  119  moves the head gimbal assemblies radially across tracks on the disk  115  until the heads settle on their respective target tracks. The head gimbal assemblies operate in a conventional manner and always move in unison with one another, unless drive  111  uses multiple independent actuators (not shown) wherein the arms can move independently of one another. 
   Currently, the installation of pivot assemblies in the block of the actuator is limited by the achievable machining tolerances of each component (e.g., the actuator and pivot cartridge assembly). Unfortunately, the stack-up tolerance increases with respect to the z-axis (i.e., the axis of the pivot and actuator) to pivot mounting surface which, in high density hard disk drives, drives much of the head instability seen in current disk drives. This would improve current efforts on arm-to-disk height measurements which has been linked to screening head instable drives. 
   Prior art solutions include shims of thin metal or plastic that are used to offset parts via the thicknesses of the shims. Shims have limitations in that the addition of more parts to solve tolerances only can minimize the tolerance incurred, but not eliminate it since it, too, is a fixed height. Adjusting tooling to compensate for trends based on basic measurements can only average out the tolerance on a population of parts. However, adjusting tooling cannot eliminate or actively customize each mating part since it is static and not dynamic as in the case of the present invention. As will be described for the present invention, an adjustable or dynamic set height is required to improve the yield loss due to instable heads, as well as reduce overall cost losses from both internal manufacturing processes and incoming supplier parts. Thus, an improved solution for adjusting the set height for actuator pivots would be desirable. 
   SUMMARY OF THE INVENTION 
   One embodiment of a system, method, and apparatus for a tooling concept for automated location system for setting the distance from the mounting surface of a pivot cartridge to the critical features on the actuator arms. This distance is set to always eliminate the tolerance incurred via normal manufacturing of these components, or set to a prescribed height that meets the hard disk drive (HDD) functionality requirements. This is done automatically to adjust for every component giving the present invention full capability to customize each actuator and/or pivot assembly to meet the functionality requirements for each HDD. As a result, the reliability and robustness of the HDD product is improved. 
   One advantage of using this idea for assembly tooling is that it&#39;s quite inexpensive and highly accurate. Typically, most pivot assemblies use either a hard stop (e.g., a flange-type design) or a screw attach (e.g., set screw or pull screw) that have their drawbacks. Flange-type pivot assemblies require specialized shims to adjust their height relative to the actuator arms. Even shims are static rather than dynamic so the tolerance incurred is always a function of how accurately the shims can be made. In addition, shims add cost to the overall design since it is an additional part number to the drive. 
   Screw attach pivot assemblies allow for adjustability, but the current tooling incurs tolerance again based on a fixed point on the tooling that is not dynamically adjustable like the present invention. Adjustable tooling via micrometers does not have the resolution to accurately dial tolerances in a high production setting. In addition, both of these prior art solutions add cost to the parts as well as the overall manufacturing cost. 
   In one solution, a probe, such as a laser-based measurement system, has a voltage output that is linear along a tolerance of +/−0.015 mm. This voltage is monitored and corrected to obtain a nominal voltage equal to whatever offset that an application requires. Although a laser-based measurement system is mentioned, it is interchangeable with any device that can take measurements and translate it to an electrical output. This device allows for individual part designs to have looser tolerances since critical dimensions to function are customized to nominal or to any prescribed dimension. This system eliminates tolerance stack-up due to pivot set height. 
   In one embodiment, a potentiometer is used to adjust target set height via a change in current settings. The present invention can be implemented on an HDD manufacturing line at the pivot installation station. It works by using the height measured using a probe that can take height measurements and translate them to electrical output, and feeding this information to a controller. The controller regulates the power to the positioning system which adjusts the pivot relative to the output of the probe. Once the positioning system adjusts the pivot shaft to the correct or desired height, the system stops and signals the operator or machine to lock the pivot into place. 
   The foregoing and other objects and advantages of the present invention will be apparent to those skilled in the art, in view of the following detailed description of the present invention, taken in conjunction with the appended claims and the accompanying drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     So that the manner in which the features and advantages of the invention, as well as others which will become apparent are attained and can be understood in more detail, more particular description of the invention briefly summarized above may be had by reference to the embodiment thereof which is illustrated in the appended drawings, which drawings form a part of this specification. It is to be noted, however, that the drawings illustrate only an embodiment of the invention and therefore are not to be considered limiting of its scope as the invention may admit to other equally effective embodiments. 
       FIG. 1  is a plan view of a conventional disk drive. 
       FIG. 2  is a circuit diagram of one embodiment of pivot set height tooling constructed in accordance with the present invention. 
       FIG. 3  is a schematic block diagram of the tooling of  FIG. 2  and is constructed in accordance with the present invention. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   Referring to  FIGS. 2 and 3 , one embodiment of an apparatus, method, and system  11  for dynamically adjusting a set height of a pivot  123  relative to an actuator  121  is shown. One embodiment of the system  11  comprises a fixture  13  (shown schematically) for restraining the body or block of the actuator  121 . Fixture  13  also could be used to restrain the pivot  123  instead. 
   A positioning system  15  is used to move the pivot  123  relative to the actuator  121 . However, if pivot  123  is restrained, positioning system  15  moves the actuator  121  relative to the pivot  123 . The positioning system  15  sets a distance  19  (e.g., set height) from a mounting surface of the pivot  123  to a critical feature (e.g., an arm surface) on the actuator  121 , such that the distance  19  is set to eliminate a tolerance stack-up between the pivot  123 , the actuator  121 , and any other intervening components. 
   A measurement system  17  is used for measuring the set height  19  of the pivot  123  relative to the actuator  121 . The measurement system  17  may comprise, for example, a laser-based measurement system and has a voltage output that is linear along a tolerance of about +/−0.015 mm, for example, and is monitored and corrected by the controller  21  to obtain a nominal voltage equal to whatever offset (i.e., change in set height) is required between the pivot  123  and the actuator  121 . 
   A controller  21  is provided for receiving input  23  from a user or computer and automatically controlling the positioning system  15  and the measurement system  17  in response to the input  23 . A measurement feedback system  25  provides feedback from measurements between the pivot  123  and the actuator  121  to the controller  21 . The system  11  may further comprise a potentiometer  27  for adjusting a target set height via a change in the input. The system  11  also may further comprise adjusting the pivot  123  to a desired height, and sending a signal  29  to lock the pivot  123  in place relative to the actuator  121 . 
   The present invention also comprises a method of dynamically adjusting a set height  19  of a pivot  123  relative to an actuator  121 . One embodiment of the method comprises restraining one of the pivot  123  and the actuator  121 , and measuring the set height  19  of the pivot  123  relative to the actuator  121 . This latter step may comprise utilizing a laser-based measurement system  17  that has a voltage output that is linear along a tolerance of, for example, +/−0.015 mm, and is monitored and corrected to obtain a nominal voltage equal to whatever offset is required between the pivot  123  and the actuator  121 . 
   The method also comprises receiving input  23  and automatically moving one of the pivot  123  and the actuator  121  relative to the other in response to the input  23 . This step may comprise, for example, setting a distance from a mounting surface of the pivot  123  to a critical feature on the actuator  121 , such that the distance is set to eliminate a tolerance stack-up between the pivot, the actuator, and any other intervening components. Finally, the method comprises providing feedback  25  from measurements between the pivot  123  and the actuator  121  to confirm a desired set height  19 . 
   In addition, the method may further comprising adjusting a target set height via a change in the input  23 , and/or adjusting the pivot  123  to a desired height, and then sending a signal  29  to lock the pivot  123  in place relative to the actuator  121 . 
   The present invention advantageously uses an inexpensive and highly accurate probe that compensates for looser tolerances in various assembled parts. This system eliminates tolerance stack-up due to pivot set height. Once the positioning system precisely adjusts the pivot to the correct or desired height, the system stops and signals the operator or machine to lock the pivot into place. This solution offers a dynamic response rather than the static solutions of the prior art. 
   While the invention has been shown or described in only some of its forms, it should be apparent to those skilled in the art that it is not so limited, but is susceptible to various changes without departing from the scope of the invention.