Abstract:
There is disclosed a spinstand for testing a head gimbal assembly. The spinstand includes a gripper operable to grip the head gimbal assembly and a load pick device operable to hold a head gimbal assembly and to move the head gimbal assembly into an exchange position where it can be gripped by the gripper. In the exchange position part of the load pick device registers with the gripper and another part of the load pick device is spaced from the gripper so as to form a space between, in which space at least part of the head gimbal assembly is located in use.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is the National Phase entry of PCT/EP2010/065686, filed Oct. 19, 2010, which claims the benefit of priority to U.S. application Ser. No. 61/235,998, filed Oct. 22, 2009, the content of these applications is incorporated herein by reference in their entirety. 
    
    
     BACKGROUND 
     The present invention relates to spinstands for testing a head gimbal assembly. 
     A so-called spinstand (also known as a head/media test apparatus or head tester) is a mechanical platform that can simulate the environment of a disk drive so that tests can be performed on the various components of a disk drive, such as the read/write head or the disk. Typically a spinstand comprises a high-mass deck on which is mounted a spindle for clamping and rotating a magnetic disk. Also provided on the deck is a mechanism commonly known as a test nest for holding and loading the head to the disk. Test data is then written to or read from the disk with the head. 
     Testing with a spinstand can be performed in a research and development setting or in a manufacturing setting. For instance, as part of the process of manufacturing most modern disk drive assemblies, the read/write head is subjected to a dynamic electrical test on a spinstand before being incorporated into the disk drive assembly to ensure that the performance of the head is acceptable. Usually the head is tested after having been incorporated into a head gimbal assembly (HGA), such as shown by  FIG. 1  and described in more detail below. 
     In order to test a HGA with a spinstand, the HGA to be tested must be received by the spinstand by attaching the HGA to the test nest. As part of the process of receiving the HGA in a spinstand, electrical connection must be made to the HGA. The head must also be aligned with high accuracy relative to the spinstand, a process commonly known as “precising” the HGA. After testing, the tested HGA is removed from the test nest. These steps can be performed by a human operator. Alternatively, some or all of these steps can be automated. 
     In handling the HGA during the process of attaching the HGA to the test nest, it is important to do so without causing damage, deformation or marking to the HGA. It is desirable that the attachment process is fast so as to optimise test process speeds. The attachment process must of course grip the HGA firmly during testing. The attachment process should be precise, reliably and repeatable. It is also desirable to keep the apparatus involved in attaching the HGA to the test nest as simple as possible, both to improve reliability and to reduce cost. During test, the HGA must be moved with great precision and preferably with great speed. It is therefore desirable that the attachment parts of the spinstand that hold the HGA during testing allow for precise and fast movement profiles for the HGA. The attachment process should preferably also lend itself to being automated. 
     Various schemes are known in the prior art for attaching a HGA to a test nest in a spinstand. For example, US2007/0143056 (“Head Gimbal Assembly Loader”), US2005/0056337 (“Method And Apparatus For Head Gimbal Assembly Testing”) and US2007/0136022 (“Alignment Of Unmounted Head Gimbal Assemblies For Testing”) teach a test nest having a collet mechanism for centering and clamping the HGA to the test nest. A separate mechanism called a precising nest is provided away from the test nest for precising the HGA. The precising nest comprises two tapered pins which engage respectively with the boss hole and the tooling hole of the HGA when the HGA is positioned on the precising nest to precise the HGA. A linear motion positioning stage is provided to move the HGAs from the precising nest to the test nest. 
     US-A-2008/0061776 (“Method And Apparatus For Loading A Read/Write Head To A Spinstand”) discloses a spinstand having separate precising stations that precise a HGA away from the test nest before the HGA is transferred to the test nest by a linear actuator. 
     SUMMARY 
     These prior art schemes each provide a separate precising assembly for precising the HGA away from the test nest and then transfer the HGA to the test nest with a precise linear actuator so that the precise orientation of the HGA achieved by the precising operation is kept when the HGA is transferred to the test nest. These schemes tend to be complicated and expensive to implement. 
     According to a first aspect of the present invention, there is provided a spinstand for testing a head gimbal assembly, the spinstand comprising: a gripper operable to grip a said head gimbal assembly; and, a load pick device operable to hold a head gimbal assembly and to move the head gimbal assembly into an exchange position where it can be gripped by the gripper, wherein in said exchange position part of the load pick device registers with the gripper and another part of the load pick device is spaced from the gripper so as to form a space between, in which space at least part of a said head gimbal assembly is located in use. 
     This arrangement in effect provides a space or cavity between the load pick device and the gripper. The registration of part of the load pick device and the gripper means that the size of the cavity can be accurately controlled. Preferably, the cavity is arranged to receive the base plate of the head gimbal assembly. The preferred cavity is arranged so that the head gimbal assembly is generally constrained in its position to avoid misalignment, but so that it allows small amounts of movement to allow the HGA to be precised and clamped in the correct position. 
     For example in preferred embodiments, the cavity means that the HGA is positioned with enough accuracy that the engagement member may locate the boss hole and so that the head gimbal assembly does not miss the stops when it is urged by the engagement member. However, the cavity is preferably arranged so that when small amounts of movement are possible for the head gimbal assembly, i.e. enough movement is possible to allow the head gimbal assembly to be urged against the stops of the gripper so that it may be precised. Without the cavity, if the pick was not disengaged with the head gimbal assembly, it would be too constrained in its movement to be accurately precised by the engagement member, and if the pick was disengaged with the head gimbal assembly and moved away, there would be a risk that the unconstrained head gimbal assembly shift in position enough that the engagement member could not engage with the boss hole, or that the head gimbal assembly could miss the stops. 
     In a preferred embodiment, the load pick device has a surface against which the head gimbal assembly is held when the head gimbal assembly is held by the load pick device and at least one protrusion, which extends from said surface for registering with the gripper. This in effect provides a recessed portion in the load pick device for containing the head gimbal assembly. As well as registering with the gripper so as to define the depth of the cavity, the protrusions can be arranged to limit possibly lateral movement of the head gimbal assembly when the pick device has registered with the gripper and released the HGA. This can help prevent possible misalignment of the head gimbal assembly when precising and clamping the HGA. 
     By urging the HGA against the stop of the gripper, the HGA is given a precise positioning in the x-y-plane. Then by clamping the HGA against the base portion of the gripper, the HGA is given a precise positioning in the z-direction as well as being securely gripped by the gripper, i.e. the test nest. This arrangement provides a simple and convenient way of precising and attaching a HGA to a spinstand. In contrast, prior art spinstands such as the spinstand disclosed by US2007/0143056 (“Head Gimbal Assembly Loader”) and US2007/0136022 (“Alignment Of Unmounted Head Gimbal Assemblies For Testing”) teach test nests incorporating relatively complex collet mechanisms for gripping the HGA and separate mechanisms for precising the HGA. These add complexity and cost. 
     Preferably said surface against which the head gimbal assembly is held is in communication with at least one fluid port via which low fluid pressure, i.e. a vacuum or near vacuum, can be applied to hold said head gimbal assembly. This provides a convenient way of holding the HGA with the pick device. 
     The spinstand may comprise an unload pick device for picking up a said head gimbal assembly from the gripper, wherein the unload pick is arranged not to register with the gripper when picking up a said head gimbal assembly. The unload pick device does not need to register against the gripper. The unload pick device preferably has a generally flat surface for contacting or coming into close proximity with the HGA when picking up the HGA. Again, fluid ports may be provided on the surface via which a vacuum may be applied to pick up and hold the HGA. 
     Preferably, a first end of one or both pick devices is compliantly attached to the second end of that pick device and, and wherein at least one guide member is attached between the first and second ends of that pick device so that relative movement between the first and second ends of that pick device is substantially limited to only one direction. For example, a compliant layer of material, such as an elastomer, can be sandwiched between the two ends of either or both pick devices. The compliant means helps reduce shock and vibration when the pick device engages with the test nest or another nest. A pin or other member or members can be disposed between the ends so that the ends are constrained to move in the direction of the pin, i.e. the direction in which the pick moves, which is the z-direction in the examples described herein. This allows the compliant means to reduce shock and vibration due to the movement of the pick when contacting the nest, whilst reducing movement in other directions so as to maintain precision in the positioning of the HGA in the x-y plane. 
     In a preferred embodiment, the gripper comprises an engagement member which is movable to fix in place the head gimbal assembly. The preferred engagement member can provide a simple mechanism that can be implemented by relatively low mass components which allow the HGA to be moved with fast and precise movement profiles during testing. In contrast, prior art mechanisms tend to have a relatively high mass due to their complex natures which leads to reduced acceleration and longer settling times when moving the HGA. This means that the present invention allows faster and more precise testing of heads, which is highly desirable in a manufacturing setting. 
     Preferably the spinstand comprises a positioning device having a base portion and a movable portion which is movable relative to the base portion, the gripper being supported by the movable portion so that the gripper is positionable by the positioning device; and, an actuator operable to engage with and move the engagement member, the actuator being supported by the base portion of the positioning device and not by the movable portion of the positioning device. 
     According to a second aspect of the present invention, there is provided a spinstand for testing a head gimbal assembly, the spinstand comprising: a gripper operable to grip a said head gimbal assembly, wherein the gripper comprises a movable engagement member which, when a head gimbal assembly is offered up to the gripper, is movable to fix in place the head gimbal assembly; a positioning device having a base portion and a movable portion that is movable relative to the base portion, the gripper being supported by the movable portion so that the gripper is positionable by the positioning device; an actuator operable to engage with and move the engagement member, the actuator being supported by the base portion of the positioning device and not by the movable portion of the positioning device. 
     The actuator can be for example a pneumatic actuator or a solenoid or other suitable device or devices. By this arrangement, the typically relatively high mass of the actuator does not have to be moved by the positioning device that moves the gripper and thus the HGA during operation of the spinstand. This means that the movable portion of the positioning device has less mass to move. This allows increased accelerations and shorter settling times to be used and therefore improves the performance of the spinstand in making fine adjustments to the position of the head during testing. 
     Preferably the actuator is disengageable from the engagement member. This means that the actuator can be moved away from the test nest and moving part of the positioning device during testing so that it has no influence on the movement of the HGA moved by the positioning device. 
     Preferably, the engagement member is biased to be in a position where it fixes in place the head gimbal assembly, wherein the actuator is operable to move the engagement member against the bias. The biasing can be accomplished by any suitable member, such as a spring. Importantly, the member used for biasing can easily be implemented by a member having a low mass compared with the actuator, which are typically more bulky and have a higher mass. Thus, the spring rather than the actuator is used for clamping the HGA during testing. 
     Preferably, the gripper comprises a base portion to which the engagement member is movably attached, at least one stop extending from the base portion; wherein the engagement member is arranged and configured to move such that the engagement member urges the head gimbal assembly against the stop and clamps the head gimbal to the base portion of the gripper. 
     Preferably, the or each stop presents a planar surface against which the head gimbal assembly is urged. 
     Preferably, the engagement member is arranged and configured to move in a direction generally perpendicularly towards said planar surface to urge the head gimbal assembly against the at least one stops. 
     Preferably, the engagement member comprises a stem portion and a head portion, the head portion having a greater diameter than the stem portion so as to provide a shoulder therebetween, wherein the engagement member is arranged and configured to move such the stem portion acts against the side of the boss hole of the head gimbal assembly to urge the head gimbal assembly against the stop and the shoulder clamps the head gimbal assembly against the base portion of the gripper. 
     Preferably, the engagement member stem contacts the side of the boss hole closest to the planar surface when urging the head gimbal assembly against the at least one stop. 
     These arrangements for urging the head gimbal assembly against the stops allow the head gimbal assembly to be precised in the x-, y- and theta directions before being clamped against the base of the gripper. 
     Preferably, the engagement member is pivotably mounted, for example to the gripper. This provides a simple convenient mechanism for the engagement member. 
     Preferably, the engagement member has a mushroom shape. Other shapes for the engagement member are possible. For example, the engagement member may have a hooked shape or a pawl shape. In any case, it is preferred that the stem of the engagement member is circular which helps in aligning the head gimbal assembly on account of the circular boss hole with which it engages when aligning the head gimbal assembly. 
     According to a third aspect of the present invention there is provided a spinstand for testing a head gimbal assembly, the spinstand comprising: a gripper operable to grip a said head gimbal assembly; and, a movable clamp that can be actuated to clamp a said head gimbal assembly when gripped by the gripper, wherein the movable clamp has a first portion for clamping the electrical contacts of the head gimbal assembly against electrical contacts of the spinstand to make electrical connection between the spinstand and the head gimbal assembly, and a second portion for clamping the flex circuit of the head gimbal assembly against a surface of the spinstand. 
     This provides a simple mechanism to make secure electrical contact from the head gimbal assembly to the spinstand and also securely clamping and thus flatten the flex circuit of the head gimbal assembly to prevent possible fluttering of the flex circuit due to the effects of “windage” when the disk of the spinstand is spinning. Windage is the name given to air fluctuations caused by the spinning disk. In prior art schemes, it is known to vacuum the flex circuit to the test nest. However, it is difficult to get the flex circuit completely flat with this arrangement, meaning that the air movement caused by windage can get under the flex circuit and lift up the flex circuit causing fluttering of the flex circuit, which can adversely affect the accuracy of the precision testing carried out by the spinstand. The mechanism of the present invention avoids or reduces these problems. 
     The first and second portions may be provided by different parts of the same member. In a preferred embodiment, the clamp member comprises a triangular plate part of which clamps the flex circuit and part of which clamps the electrical contacts. 
     Preferably, the spinstand has a grooved member and the clamp has a cam disposed in the groove of the grooved member in which it can move so as to guide the movement of the clamp in clamping the head gimbal assembly. Because the HGA is preferably delivered to the gripper from above, it is preferable to be able to move the clamp down to clamp the HGA from the side. The cam provides a simple and convenient way of controlling the motion of the clamp. 
     In an embodiment, the movable clamp is arranged to clamp both a head gimbal assembly having an up head configuration and a head gimbal assembly having a down head configuration. Preferably, the clamping portions extend both sides of the test nest so as to be able to clamp the flex circuit and electrical contacts whichever side of the test nest the flex circuit is located according to whether the HGA has an up head or down head. In reconfiguring the spinstand to test an HGA of a different type (i.e. up or down head), the cam may be swapped to provide suitable clamping functionality. 
     Generally, the preferred embodiments of the present invention provide an advantageously fast, precise and repeatable way of precising and gripping a HGA with a gripper, e.g. a test nest, without causing damage, deformation or marking to the HGA. 
     It should be noted that references in this document to the x-y plane and to the x- and y-direction (or axes) relate to directions parallel to the deck of the spinstand, and references to the z-direction or “raising” or “lowering” a part relate to directions perpendicular to the deck. 
    
    
     
       DESCRIPTION OF DRAWINGS 
       Embodiments of the present invention will now be described by way of example with reference to the accompanying drawings, in which: 
         FIG. 1  shows a typical head gimbal assembly; 
         FIG. 2  shows schematically an example of a spinstand according to an embodiment of the present invention; 
         FIG. 3  shows a detail view of the spinstand of  FIG. 2 ; 
         FIG. 4  shows a detail view of the carriage of  FIG. 2 , 
         FIG. 5  shows a detail view of the linear actuator and pick of  FIG. 2 ; 
         FIG. 6  shows a detail view in cross section of a HGA being received by the test nest from the pick; 
         FIG. 7  shows a cross section view in the y-z plane of the test nest of  FIG. 2 ; 
         FIGS. 8A and 8B  show a HGA being received and precised by the test nest of  FIG. 2 ; 
         FIGS. 9 and 10  show the test nest prepared to receive HGAs in the down head configuration and up head configuration respectively; and, 
         FIGS. 11 and 12  show the test nests of  FIGS. 9 and 10  respectively with the FOS clamp in the clamping position. 
     
    
    
     DETAILED DESCRIPTION 
     Read/write heads for use in a hard disk drive assembly are usually tested once the slider has been mounted on the suspension, i.e. once they have been incorporated into a head gimbal assembly (HGA).  FIG. 1  shows a typical HGA  100  of the type testable by a spinstand. The HGA  100  has a magnetic read/write head  101  for reading from and writing to a disk. The head  101  is supported on a slider which in turn is mounted via a gimbal  102  to a suspension arm  103 . These are arranged to “fly” the head  101  over the surface of the disk at an appropriate height for reading from and writing to the disk. The suspension arm  103  also has a tooling slot  104  formed in it. The suspension arm  103  is attached to a base plate  105 . The base plate  105  has a boss hole  106  in its centre by which the HGA  100  can be held. Two locating tabs  107  extend from the edge of the base plate  105  furthest from the head  101 . A flex circuit  108  (also known as a flex-on-suspension (FOS) or FOS tail), which is a flexible thin strip containing the connecting wires, connects to the head  101  at one end and terminates in an array of electrical contacts  109  (also known as a pogo pin block) at its other end allowing connections to be formed to the HGA  100  by the spinstand electronics. 
       FIG. 2  shows schematically an apparatus for testing a read/write head (also known as spinstand)  1  in accordance with aspects of the present invention. The spinstand  1  comprises a deck  2  surrounded by a safety enclosure  3 . The spinstand  1  has a spindle assembly  4  for holding and rotating a disk  5  to be tested. The spinstand  1  also has a test nest  20  or gripper for holding the HGA  100  during testing. The test nest  20  is supported by a puck  30  which is movable over the surface of the deck  2  and can make connection to the HGA  100  and load it to the disk  5 . The spinstand  1  also comprises automation for loading and unloading a HGA  100  to and from the test nest  20 . These features of the spinstand  1  as described so far are generally known per se in the prior art. 
     Various automation schemes are known in the art. In the present example, the automation comprises a carriage or shuttle  50  for transporting HGAs  100  into and out of the safety enclosure  3  and a pick  10  for exchanging HGAs between the carriage  50  and the test nest  20 . A suitable form of automation for operation with the present invention is described in the commonly owned U.S. Ser. No. 61/176,335 filed 7th May, 2009 entitled “Apparatus And Method For Receiving And Positioning A Read/Write Head To A Disk For Testing And Method Of Removing A Tested Read/Write Head From A Test Apparatus”, the entire contents of which are incorporated herein by reference. The operation of this spinstand of the present example is described in more detail below and is the same as U.S. Ser. No. 61/176,335 except where otherwise described in this description. It will be appreciated that the present invention is not limited to being used with this particular automation scheme however. 
       FIG. 3  shows an elevated view of the spinstand  1  (the spindle  4  and disk  5  not being shown for clarity). The deck  2  has a high mass, for example being made from a block of granite. The deck  2  is compliantly mounted to a frame (not shown) by pneumatic or other vibration damping mounts so as to “float”. This isolates the spinstand  1  from external vibrations and provides a very stable mechanical platform on which testing may be performed. As will be appreciated, it is important to isolate the spinstand from external vibrations as much as possible, as these can adversely affect the delicate testing being performed by the spinstand. 
     The safety enclosure  3  comprises walls  3   a  made from plexi-glass or some other suitable material and is preferably mechanically isolated from the deck  2 , for example being attached to the frame (not shown). The safety enclosure  3  is arranged to protect the operator of the spinstand  1  from injury when the spinstand is in use, such as might be caused for example by contact with the automation of the spinstand or from flying glass in the event that a disk  5  having a glass substrate shatters whilst being spun. 
     As shown by  FIG. 4 , the carriage  50  has two HGA receiving portions  52 ,  53 , or nests, thereon each for receiving and holding a HGA  100 . The first HGA receiving portion is known as the load nest  52 , in which the operator places HGAs  100  to be tested. The second HGA receiving portion is known as the unload nest  53 , from which the operator removes HGAs  100  after they have been tested. A sleeve  54  extends through an aperture  55  in the safety enclosure  3 , through which the carriage  50  moves in a manner similar to a matchbox. One or more baffles  54   b  are provided so that there is no line of sight through the sleeve  54  in any position of the carriage  50 . The carriage  50  is mechanically isolated from the deck  2 , for example being attached to the frame (not shown), to avoid introducing vibration to the spinstand  1  through movement of the carriage  50 . This arrangement allows HGAs  100  to be changed without having to stop the media disk spinning, or without stopping testing due to shock and/or vibration. 
     The load nest  52 , and optionally the unload nest  53 , has a coarse precisor  57  arranged to receive a HGA  100  and give it a general positioning. The coarse precisor  57  includes a boss pin  58  and a pair of “goalposts”  59  in the form of a pair of pins projecting upwards from the uppermost surface of the carriage  50 . When a HGA  100  is placed on the coarse precisor  57 , the boss hole  106  in the base plate  105  of the HGA  100  engages with the boss pin  58 , thereby coarsely positioning the HGA  100  in the x-y direction, and the suspension arm  103  is received between the goalposts  59 , giving a rough theta positioning to the HGA  100 . 
     During operation of the spinstand, the carriage  50  is moved between a first position, where it is positioned so that the load and unload nests  52 ,  53  are accessible to an operator outside the safety enclosure  3  and a second position, where it is positioned so that the load and unload nests  52 ,  53  lie underneath the pick  10  so that the pick  10  can transfer HGAs  100  to and/or from the carriage  50 . 
     The pick  10  is shown in more detail by  FIG. 5 . The pick  10  is attached to a linear actuator  11  which is mounted to the deck  2 . The linear actuator  11  is operable to move the pick  10  laterally relative to the surface of the deck  2  (i.e. in the x-y plane). The pick  10  comprises load and unload kickers  12 ,  13  (or pick devices), each having a vacuum end effector  14 ,  15  disposed at its lower end. The load kicker  12  is for transferring HGAs  100  to be tested from the load nest  52  of the carriage  50  to the test nest  20 , and the unload kicker  13  is for transferring HGAs  100  once tested from the test nest  20  to the unload nest  53  of the carriage  50 . The pick  10  is capable via air actuation or a servo controlled motor or other appropriate actuator of moving the kickers  12 ,  13  in the z-direction, i.e. to be vertically raised or lowered. In the present example, the kickers  12 ,  13  are joined so that they are moved in the z-direction together, though the kickers  12 ,  13  may be independently movable in other examples. 
     Thus, with a HGA  100  positioned beneath either or both end kickers  12 ,  13 , the pick  10  can be actuated to lower the kickers  12 ,  13  so that the end effectors  14 ,  15  are in contact with or positioned closely above the base plate of the HGA  100  when held by any one of the test nest  20 , the load nest  52  and the unload nest  53 . The end effectors  14 ,  15  have vacuum ports  18  (shown in  FIG. 6 ) in their lower surfaces  14   b ,  15   b  through which a vacuum can then be applied so that ambient air pressure causes the base plate  105  to be forced against said lower surfaces. In other words, the HGA  100  is “vacuumed” or “suctioned” onto the end effector  14 ,  15  to hold it in place. The pick  10  can then be actuated to raise the kickers  12 ,  13 , thereby picking up the HGA  100 . The HGA  100  can be put down by the kickers  12 ,  13  by a generally similar process in reverse. It should be noted however, that there are important differences between the load and unload end effectors  14 ,  15  which are described in more detail below. 
     As well as being movable to position the head  101  under the disk  5  as described above, the puck  30  can be moved such that the test nest  20  lies underneath either of the kickers  12 ,  13 . Thus, by appropriate positioning of the carriage  50  and the puck  30  and by appropriate operation and positioning of the pick  10 , HGAs  100  can be transferred between the carriage  50  and the test nest  20  via the pick  10 . The pick  10  is positioned by the linear actuator  11  in different locations over the deck  2  for exchanging HGAs  100  with the carriage  50  and with the test nest  20 . This is so that when transferring a HGA  100  from the carriage  50  to the test nest  20 , it is not necessary to move the carriage  50  out of the way before the test nest  20  can be moved underneath the kickers  12 ,  13 , and visa versa. 
     A potential complication arises from the fact that the deck  2  on which the puck  30  moves is compliantly mounted relative to the frame, in order to reduce the amount of vibration transmitted to the deck  2  and all the apparatus mounted on it, which includes the kicker and its transport. The carriage  50 , however, is mounted on the frame, and therefore movement can occur between the carriage  50  and the kicker  12 . This means that, without special arrangements, the load kicker  12  might not be positioned relative to the HGA  100  with enough precision to be able to pick up the HGA  100  from the load nest  52  or to pick up the HGA  100  with enough accuracy to allow the HGA  100  to be subsequently transferred to the test nest  20 , as described later. 
     To overcome this problem the load and unload nests  52 ,  53  are mounted on the carriage  50  in such a way, for example via some intermediary layer of compliant material, as to allow a small amount of lateral movement, which is of the order of the amount that the deck  2  can move relative to the frame. Between the load kicker  12  and the load nest  52  is an alignment aid for aligning the load kicker  12  and load nest  52  when the load kicker  12  descends to pick up an HGA  100 . A suitable method of alignment is a shaped pin on the carriage  50  entering a hole on the kicker  12 . Other, more sophisticated means, for example using cams, can be used to ensure correct positioning between the nests  52 ,  53  and the kicker  12 , as will be known to those skilled in the art. When this has happened the nests  52 ,  53  and the kicker  12  are sufficiently precisely aligned to allow the load kicker  12  to pick up an HGA  100  correctly. 
     Referring again to  FIG. 3 , the puck  30  is mounted on the deck  2  by an air bearing (not shown) and is movable in two orthogonal directions on the surface of the deck  2  by a highly accurate x-y positional stage  31 . The puck  30  can be vacuumed down to the deck  2  in a desired position. Thus, as known in the art per se, the puck  30  is movable to position the head  101  to a test track on the disk  5  to test the HGA  100 . A positioning device, in this example a nanopositioner  35  (shown in more detail in  FIG. 7 ), is disposed between the puck  30  and the test nest  20 , which allows very fine positional changes of the head  101  to be made relative to a test track on the disk  5 . The puck  30  is also movable to position the test nest  20  under the load kicker  12  so that a HGA  100  to be tested can be transferred to the test nest  20  from the load kicker  12 ; and to move the tested HGA  100  under the unload kicker  13  so that the tested HGA  100  can be removed and transferred to the carriage  50 . 
       FIG. 6  shows a cross section of the kickers  12 ,  13  with the load kicker  12  transferring a HGA  100  to the test nest  20 . The lower surface  14   b  of the load end effector  14  is generally flat and has vacuum ports  18  formed in it. The base plate  105  of the HGA  100  is held against this surface  14   b  by the action of the vacuum. The load end effector  14  also has portions  14   a  extending downward from the surface  14   b . (The unload end effector  15  optionally does not have such extending portions, as shown in  FIG. 6  and as described in more detail below.) Thus, a depression is formed in the end of the load kicker  12  in which the base plate  105  of the HGA  100  is received when held by the end effector  14 . This depression is slightly deeper than the thickness of the base plate  105  of the HGA  100 . This means that, when delivering an HGA  100  to the test nest  20 , the load kicker  12  is actuated downwards until the extending portions  14   a  make contact with top surface  20   a  of the test nest  20 , at which point the HGA  100  is not yet in contact with the test nest  20 . The vacuum holding the HGA  100  is then released so that the HGA  100  falls a very small distance onto the test nest  20 . 
     In order to reduce the shock transmitted to the deck  2  via the test nest  20  when the kickers  12 ,  13  descend and make contact with the test nest  20 , the upper parts  12   a ,  13   a  of the kickers  12 ,  13 , i.e. the part that is actuated vertically, is isolated by a compliant layer of material  16  from the lower parts  12   b ,  13   b  of the kickers  12 ,  13 , i.e. the parts having the end effectors  14 ,  15  which contact the test nest  20 . One or more guide members  17 , such as guide pins, are provided to ensure that the lower parts  12   b ,  13   b  cannot move laterally with respect to the upper parts  12   a ,  13   a , while allowing some vertical movement between the parts. 
     As shown in  FIG. 7 , the test nest  20  comprises an engagement member, which in this example is provided by a mushroom-shaped pawl  21  (shown in cross section in  FIG. 6 ) having a head portion  21   a  and a stem portion  21   b  which protrude from the top surface  20   a  of the test nest  20 . The stem portion  21   a  has a smaller diameter than the head portion  21   a . As can be seen from  FIG. 7 , the leading surface  21   c  of the pawl  21  is slanted downwards. The pawl  21  also comprises an pivot member  21   d , the lower end of which is pivoted to the test nest  20  by a pivot  21   e  and the upper end of which supports the stem  21   b  and head  21   a . Thus, due to the pivoted mounting of the pawl  21 , the head and stem portions  21   a ,  21   b  move in a shallow arc as the pawl  21  pivots. As will be appreciated, when the head  21   a  is above the pivot  21   e , the movement of the head  21   a  is effectively horizontal. As the head  21   a  moves past the pivot  21   e , the movement of the head  21   a  has an increasing downward component as well as a horizontal component. 
     The test nest  20  also has two stops  22  extending from its top surface  20   a . The pawl  21  is moved by an actuator  23  and a spring  24 . The spring  24  is fixed between the test nest  20  and the pawl  21  and biases the pawl  21  in the y-direction towards the stops  22 . The actuator  23 , in this example a pneumatic cylinder, is mounted to the puck  30 . Actuation of the actuator  23  causes a protruding part  23   a  of the actuator  23  to push against a protruding part  21   e  of the pivot member  21   e  causing the pawl  21  to pivot against the bias of the spring  24  and thus to move the pawl  21  in the y-direction away from the backstops  22 . 
     Referring now to  FIGS. 8A and 8B , to receive a HGA  100  in the test nest  20 , the pawl  21  is first actuated by the actuator  23  to move against the bias of the spring  24  to a preload position. A HGA  100  is then placed in position on the test nest  20  by the load kicker  12  as previously described. So positioned, the head portion  21   a  and some of the stem portion  21   b  of the pawl  21  pass through the boss hole  106  of the HGA  100 . 
     Next, the actuator  23  is deactivated, allowing the spring  24  to move the pawl  21  towards the stops  22 . Due to the horizontal component of the motion of the pawl  21 , the stem  21   b  contacts the edge of the boss hole  106  of the HGA  100  and pushes the HGA  100  in the y-direction until its two locating tabs  107  both press against the stops  22 . Once registered against the stops  22 , the HGA  100  is precisely located in the y-direction and in its angular orientation. Because the diameter of the stem of the pawl  21  is less than the diameter of the boss hole  106 , the movement of the pawl  21  in the y-direction also causes the HGA  100  to move in the x-direction to ensure precise alignment in that direction, which is achieved when the centre of the boss hole  106 , the centre of the pawl  21  and the point of contact between the pawl  21  and the boss hole  106  are in a straight line parallel to the direction in which the pawl  21  moves, i.e. the y-direction. The stem portion  21   a  and the boss hole  106  preferably have a circular cross section to aid this alignment process. 
     As the stem  21   b  of the pawl  21  pushes the HGA  100  against the stops  22 , the downward slant of the leading surface  21   c  pushes the HGA  100  downwards against the top surface  20   a  of the test nest  20  as the HGA  100  is registered against the stops  22 . Also, as previously described, as the pawl  21  moves towards the stops  22 , the motion of the head  21   a  of the pawl  21  develops a component in the z-direction due to the pivoted mounting of the pawl  21 , which may additionally or alternatively contribute to clamping the HGA  100  against the top surface  20   a  of the test nest  20 . 
     Thus, by this process the HGA  100  is precised and clamped to the test nest  20 . The depression under the load end effector  14 , keeps the HGA  100  loosely in position during this process, locating the HGA  100  with enough precision for the pawl  21  to accurately engage the boss hole  106  and for the HGA  100  to accurately engage with the stops  22 , whilst allowing sufficient movement to allow precising of the HGA  100  by the pawl  21 .  FIGS. 8A and 8B  show the HGA  100  before and after the precising operation. 
     As can be seen from  FIG. 7 , the nanopositioner  35  has a fixed part  35   a  attached to the puck  30  and a moving part  35   b  to which the test nest  20  is attached. As previously described, the actuator  23  is attached to the puck  30  and not to the test nest or moving part  35   a  of the nanopositioner  35 . After the HGA  100  has been clamped by the spring  24 , the actuator  23  is retracted away from the pawl  21  and test nest  20  so that there is no contact between actuator  23  and any part of the test nest  20  or the moving part  35   a  of the nanopositioner  35 . Thus, when retracted, the actuator  23  is not supported by the moving part  35   a  of the nanopositioner  35  and does not interfere with the movement of the test nest  20  by the nanopositioner  35 . This is advantageous as it reduces the mass that must be moved by the nanopositioner  35  by not having the actuator  23  supported by the moving part  35   a . This allows more responsive moving of the head  101  by the nanopositioner  35  during testing. 
     Next, electrical connection must be made between the spinstand  1  and the HGA  100 . Referring to  FIG. 9 , the puck  30  has a preamp board  25  for pre-amplifying the data signals from the head  101 . This needs to be connected to the HGA  100 . Behind the test nest  20  is a surface portion of the puck called the FOS support  26 , which is for supporting the FOS  108  when a HGA  100  is held by the test nest  20 . Near the test nest  20  is a pogo pin block  27 , which comprises an array of sprung connector pins. These are positioned so that when a HGA  100  is held by the test nest  20 , the connector pins of the pogo block  27  are underneath the electrical contacts  109  of the HGA  100 . 
     A FOS clamp  40  is mounted to the puck  30  and can be actuated to urge together the sprung connector pins of the pogo block  27  and the electrical contacts  109  of the HGA so that electrical connection is made from the preamp board  25  to the HGA  100  and for flattening the FOS  108  against the FOS support  26 . 
     The FOS clamp  40  comprises a clamping member  41 , which is pivotably mounted to the puck  30  via a pivot  42  that allows up and down movement of the clamping member  41  in the z-direction as well as pivotable movement in the x-y plane. One end of the clamping member  41  is shaped for flattening the FOS  108  and making the electrical contact between the contacts  109  and the pogo block  27 . The other end of the clamping member  41  has a cam  43  which is engaged with a groove  44  provided in a structure  45  removably attached to the puck  30 . An actuator  46 , for example a pneumatic control, is arranged to move the clamping member  41  up and down. When moving up, the clamping member  41  is made to rotate to one side or the other by the cam  43  moving in the groove  44 , due to the angle of the groove  44 . This is to make room for an HGA  100  to be placed on the test nest  20  with the FOS  108  resting on the FOS support  26 . The clamping member  41  is then actuated downwards, while being forced to rotate to its central, clamping position by the cam  43  moving in the groove  44 , thus flattening the FOS  108  to the FOS support portion  26  and making the electrical connection between the pogo pin block  27  and the electrical contacts  109  on the HGA  100  when a HGA  100  is on the test nest  20 . Flattening the FOS  108  prevents it from vibrating due to windage from the disk  5  during testing.  FIG. 11  shows the FOS clamp  40  in the clamping position. For clarity,  FIG. 11  does not show a HGA  100  in situ. 
     During the transfer of a HGA  100  from the load kicker  12  to the test nest  20 , a pre-loader plunger (not shown) attached to the load kicker  12  is actuated so as to press down on the suspension arm  103  of the HGA  100 , bending it so that the head  101  is moved vertically downwards into its preload position. A head loader  28  having a retractable ramp  29  is attached to the puck  30 . With the suspension arm  103  and head  101  in the preload position, the ramp  29  is actuated to move in from the side of the HGA  100  and to engage with the top of the suspension arm  103  so as to maintain the head  101  in the preload position. The pre-loader plunger is then raised and the load kicker  12  disengaged, actuated upwards and can be moved away. 
     The puck  30  is then moved so that the head  100  is over the desired track on the disk  5 , and the head  100  is loaded onto the surface of the disk  5  by retracting the head loader  28  allowing the head  101  to rise to its operating position. Once the head  101  is above the desired part of the disk surface, the ramp  29  disengages, allowing the head  101  to fly on the surface of the disk  5 . The profile of position against time of how the head  101  is loaded to the disk  5  is determined by the profile of a cam (not shown) which rotates to move the head loader  28 . Different position/time profiles, as may be required for different types of HGA  100 , can readily be obtained by using cams with different profiles. Alternatively, a rack and pinion mechanism or indeed any other suitable mechanism can be used to load the head  101  to the disk  5 . 
     With the head  101  loaded to the disk  5 , testing can take place, i.e. data can then be written to or read from the test track of data on the disk  5 , whilst the nanopositioner  35  is used to make fine positional changes to the head  101  relative to the test track. 
     Now, in hard disk drives both surfaces of each disk are typically used. As a result HGAs  100  are produced in two types, known as up HGAs and down HGAs, which are mirror images of each other and used respectively for the two surfaces of a disk  5 . 
     It is desirable for the spinstand  1  to be able to test both types of HGA  100 . This is accomplished in the present example of a spinstand  1  as follows. Testing is performed on one surface of the disk  5  only and to test the two types of HGA  100 , the disk  5  is spun in a different direction for each. Two pogo pin blocks  27  are provided, respectively in the correct position for the two types of HGA  100 . The clamping member  41  of the FOS clamp  40  extends on each side of the centreline of the test nest in the y-direction, corresponding to the position of the FOS  108  for each type of HGA  100 . The movement of the clamping member  41  to the side can be altered to be suitable for the type of HGA  100  by changing the orientation of the groove  44  in which the cam  43  moves, for example by unfastening the structure  45  in which the groove  44  is formed and substituting another structure  45 . The head loader  28  and ramp  29  are designed so that they can be readily moved onto either side of the test nest, again, for example, by unfastening and refastening on the other side.  FIGS. 9 and 10  show the FOS clamp in the disengaged position for the down and up head configurations.  FIGS. 11 and 12  show the FOS clamp in the engaged position for the down and up head configurations. 
     So, during the testing cycle, having removed a tested HGA  100  from the unload nest  53  and placed a new HGA  100  to be tested on the load nest  52 , the operator signals the spinstand  1 , for example by pressing a button, that testing can begin. The carriage  50  then moves inside the enclosure  3 , and the HGA  100  is picked up from the load nest  52  by the load kicker  12 . The pick  10  is then moved by the linear actuator  11  to a different position on the deck  2  for exchanging the HGA  100  with the test nest  20 . The puck  30  is moved so that the test nest  20  is under the load kicker  12  and the HGA  100  is transferred to the test nest  20 . The various operations described above are then performed to mount the HGA  100  to the test nest  20  and the HGA  100  is tested. 
     When testing is complete the puck  30  is moved so that the tested HGA  100  can be picked up from the test nest  20  by the unload kicker  13 . To remove an HGA  100  from the test nest  20 , the kicker  13  descends until the unload end effector  15  is in contact with the HGA  100 . The pawl  21  is then moved by the actuator  23  to release the HGA  100  and vacuum is applied to the vacuum ports  18  of the unload end effector  15  to hold the HGA  100 . As can be seen from  FIG. 6 , in the present example, in contrast to the load end effector  14 , the unload end effector  15  does not have a depression in its end, i.e. its lower surface  15   a  is generally flat, so as to help the vacuum to pick up and hold the HGA  100 , and ensures that there is no lateral movement as the HGA  100  is transferred from the test nest  20  to the unload kicker  13 . Nonetheless, in other examples of the spinstand, the unload end effector  15  may have similar protrusions as the load end effector  14 . The unload kicker  13  picks up the HGA  100  and transfers it to the unload nest  53  on the carriage  50 . Finally the carriage  50  moves outside the safety enclosure  3  so that the tested HGA  100  may be removed and an untested one placed on the load nest  52 , and the cycle repeats. 
     All the movements of the spinstand  1  are controlled automatically, for example by computer control. 
     Embodiments of the present invention have been described with particular reference to the example illustrated. However, it will be appreciated that variations and modifications may be made to the examples described within the scope of the present invention. For example, the invention is not limited to the specific spindle types or arrangements, or puck  30  positioning devices, or actuators specifically described in the description. In an alternative embodiment the HGAs may be handled by an automation system external to the spinstand which replaces the carriage  50 .