WO1999058995A1

WO1999058995A1 - Disk head tester facility with non-repeatable runout reduction

Info

Publication number: WO1999058995A1
Application number: PCT/US1999/009855
Authority: WO
Inventors: Oleg A. Gergel; Mostafa Mahmoudian; Virginia Kwok; Alfred Cheng
Original assignee: Kmy Instruments, Llc
Priority date: 1998-05-11
Filing date: 1999-05-05
Publication date: 1999-11-18
Also published as: AU3883699A

Abstract

In a spinstand (100) for testing disk drive components, non-repeatable runout is reduced by minimizing the mass of air spinning between disks (122) and closely adjacent to the upper and lower surfaces of top (122a) and bottom (122f) disks of a disk pack (120), by placing a removable baffle plate between each of the disks and, optionally, above the topmost disk (122a) and/or below the bottommost disk (122f) of the disk pack. Turbulence causing the non-repeatable runout is reduced as well. The spinstand (100) creates a controlled environment for the disk pack (120) and head stack assembly (126) under test by forming a chamber which entirely encloses these components when in fully engaged position. The top cover (162) of the chamber is removable for access to the disk pack. Removable disk edge baffles (160) are provided which have an inner surface concentric with and closely spaced outside the outer edge of the rotating disks, for at least a portion of arc of the disks.

Description

DISK HEAD TESTER FACILITY WITH NON-REPEATABLE RUNOUT REDUCTION

BACKGROUND OP THE INVENTION

1. Field of the Invention

The invention relates to disk head testing apparatus, and more particularly, to a technique for reducing track misregistration and errors in reading data from a disk pack using heads under test, resulting from non-repeatable runout.

2. Description of Related Art

Advances in compressing the data tracks on magnetic disks in the computer industry have resulted in a concomitant need for increased positioning accuracy in the magnetic heads commonly used in computer disk drives. Positioning must be even more precise in instrumentation equipment intended to test disk drive components, because of the need to isolate the measurements from any performance degradation caused by slight track misalignment. A spinstand which can accomplish extremely fine linear positioning of a disk head over a track of a disk is described in U.S. patent application Serial No.08/657, 039, filed May 28,

1996, entitled "Micropositioning Device for Disk Head

Testing System", by inventor Michael Mager, Attorney

Docket No. KMYI-1000, incorporated by reference herein.

More recent advances in disk drive technology suggest that not only are data tracks on magnetic disks being spaced more closely together, but the disks also must spin at higher and higher rates . As the disks spin faster, for example beyond 5,000 or 10,000 r.p.m. , it has been observed that the disks begin to vibrate horizontally, causing runout. Moreover, such runout is non-repeatable, meaning it has no particular easily identifiable pattern which can be compensated. Even extremely accurate micropositioners such as that described in the above-incorporated patent application will have a difficult time maintaining an accurate position above a track where the track itself is moving relative to the head position due to non-repeatable errors .

Accordingly, there is a need in the disk drive component test industry for a method of reducing the non-repeatable runout experienced at higher disk revolution rates.

SUMMARY OF THE INVENTION Applicants have discovered that a major reason for non-repeatable runout (NRR) is the turbulence of air trapped between the disks of a multi-disk disk pack, or adjacent to the disk surfaces of a single-disk pack. Such turbulence increases as the speed of the spindle motor increases, causing the disks and heads to vibrate. The entire disk pack is impacted by this abnormality.

Because the disk drive heads depend on airflow in order to create the air bearing which lifts them off of the disk surface as the disk spins, a certain amount of airflow is required in the testing apparatus. Air trapped between the disks or adjacent to disk surfaces spins with the disks, thereby creating the airflow required for the air bearings. However, only the laminar portion of the airflow is required for this purpose. Air that is spinning more than ten microinches or so away from the disk surface serves no beneficial purpose and only creates turbulence. The invention therefore involves reducing the mass of air spinning at a distance from the disk drive surfaces which is not required for proper disk head operation.

In particular, roughly described, the invention involves three features which can preferably, but not necessarily, all be employed together. First, the mass of air spinning between the disks in the disk pack and closely adjacent to the upper and lower surfaces of the top and bottom disks, is minimized by placing a baffle plate between each of the disks and, optionally, above the top-most disk and/or below the bottom-most disk of the disk pack. The baffle plate preferably covers as much of the disk as possible, except for a center hole for the spindle assembly, and a cut-out for lateral removability relative to the spindle assembly. The cut-out may be made large enough further to avoid the range of motion of each type of head stack assembly which the spinstand is to be used for testing. By reducing the mass of air spinning between the disks, the turbulence causing the non-repeatable runout is reduced as well.

Second, the spinstand creates a controlled environment for the disk pack and head stack assembly by forming a chamber or shroud which entirely encloses these components when in the fully engaged position. Third, disk edge baffles are provided which have an inner surface concentric with an closely spaced outside the outer edge of the rotating disks, for at least a portion of arc of the disks, the amount of air entering to and between the disks from the sides is thereby minimized.

Finally, because the spinstand is a test instrument and not a production disk drive, the baffle plates and optionally the disk edge baffles are made in such a way as to be removable relative to the spindle assembly so that disks in the disk pack can be replaced as needed during testing.

BRIEF DESCRIPTION OF THE DRAWINGS The invention will be described with respect to particular embodiments thereof, and reference will be made to the drawings, in which:

Fig. 1 is a symbolic top view of a portion of a spinstand, in the fully engaged position, according to the invention.

Fig. 2 is a cross-sectional view taken at lines 2-2 of the apparatus of Fig. 1.

Fig. 3 is a symbolic top view of the same portion of spinstand of Fig. 1, in a fully disengaged position, according to the invention.

Fig. 4 is a cross-sectional view taken along lines 4-4 of the apparatus of Fig. 3.

Fig. 5 is a close-up view of a portion of the cross-sectional view of Fig. 2. Fig. 6 is a top view of one of the separator members of Figs. 1-5.

Fig. 7 is a cross-sectional view taken at lines 7-7 of the separator member of Fig. 6.

Figs. 8, 9 and 10 are top views illustrating variations on the shape of the separator member of Fig. 6.

DETAILED DESCRIPTION

Fig. 1 is symbolic top view of a portion of a spinstand 100 according to the invention. A cross- sectional view, taken along lines 2-2 of Fig. 1, is shown in Fig. 2. The spinstand 100 comprises a base 110, in which a spindle motor 112 is mounted. The spindle motor 112 has a spindle assembly 114 which includes, in the embodiment described herein, a spindle 116 surrounded by a spindle chuck 118. A disk pack 120 consisting of six parallel rigid disks 122a, ... , 122f (collectively, 122) is shown on the spindle assembly 114. The spindle assembly 114 has a rotational center point 124. Although a multi-disk disk pack is shown in the drawings herein, aspects of the invention can be used also with disk packs containing only a single disk. The spinstand 100 has an actuator assembly 125 including a removable head stack assembly (HSA) 126 under test having 12 head arms 128a, ..., 128_

(collectively 128) and 12 magnetic heads, one for each of the upper and lower surfaces of each of the six disks of the disk pack 120. The HSA is mounted on the shaft 130 of an actuator motor 132, via tooling 134. The actuator motor shaft 130 has a rotational center point 136. The actuator assembly 125 is attached to the fine positioning stage of a micropositioner such as that described in the above-incorporated patent application. For simplicity of illustration, however, only a simplified attachment mechanism is shown in the figures for attaching the actuator assembly to the spinstand base 110. In particular, the actuator assembly 125 is shown attached to a coarse positioning stage 138 by means of two sliders 140 and 142. Under computer control, the stage 138 can be slid horizontally to the left by means of a stepper motor and lead screw (not shown) . When moved to the left to a disengaged or home position of the stage 138, the head arms 128 of the HSA 126 are no longer engaged with the disks 122 of the disk pack 120. In this position, the HSA can be removed and replaced with another HSA whose heads are to be tested by the spinstand 100.

Also attached to the spinstand base 110 via a second pair of sliders 144 and 146, is a baseplate baffle holder 148 of a baffle assembly 150. Like the coarse positioning stage 138, the baffle assembly 150 is shown in Figs . 1 and 2 in an engaged or closed position. The baffle assembly 150 includes a baffle wall 152 extending vertically off the baffle holder plate 148. The baffle wall 152, the structure of which is described in more detail hereinafter, has an arcuate inner surface 154 which for at least a portion of arc of the disks 122, is concentric with and located just beyond the edges of the disks 122. Protruding radially inwardly (relative to the spindle assembly 114) from the baffle wall 152 are seven baffle plates 160a,...160g (collectively, 160). The baffle plates 160 extend between each adjacent pair of the disks 122 of the disk pack 120, as well as above the top disk 122a and below the bottom disk 122f . The structure of the baffle plates 160 is described in more detail hereinafter.

Attached to the top of baffle wall 152 is a cover plate 162 which, when both the coarse positioning stage 138 and the baffle assembly 150 are in their respective engaged positions, makes an hermetic seal with another wall 164 that is attached to and extends vertically from the coarse positioning stage 138. The apparatus also has left and right sidewalls (not shown) such that, when both coarse positioning stage 138 and the baffle assembly 150 are in their respective engaged positions, a fully sealed chamber is formed around the HSA and disk pack to limit the amount of air circulating and penetrating from outside the test region. The walls and top and bottom of the test chamber are furthermore made of electrically conductive metal material, to thereby provide EMI protection as well. As shown in Fig. 2, disk 122a is mounted "above" the other disks of the disk pack 120. As used herein, the term "above" means farther away from the spinstand base 110. For example, if the spinstand 100 were to be turned upside down, such that the disk pack 120 is lower relative to the earth than the base 110, the disk 122a would still be considered to be disposed "above" the other disks in the disk pack 120 because disk 122a is farther away from the spinstand base 110 than are the other disks. Fig. 3 is a top view of the spinstand apparatus 100 with both the coarse positioning stage 138 and the baffle assembly 150 in their open or disengaged positions. Fig. 4 is a cross-sectional view of the apparatus taken at lines 4-4 of Fig. 3. When both the stage 138 and the baffle assembly 150 are disengaged, the disk pack 120 can be freely lifted off the spindle assembly 114 and replaced. The baffle plates 160 no longer extend into and over the disks 122. Unlike a production hard disk drive, disk drive head and disk testing apparatus must provide such a position because wear and tear on the disks 122, as well as a higher frequency of head crashes, require that the disks 122 be replaced periodically. In the embodiment described herein, the baffle assembly 150 is moved manually on the sliders 144 and 146 between the engaged and disengaged positions, although in another embodiment, such movement can be automated.

Fig. 5 is an enlarged view of a portion of the cross-sectional view of Fig. 2 of the spinstand with the baffle assembly 150 in its engaged position relative to the spindle assembly 114. It can be seen that the baffle wall 152 is actually built up with a number of separator members 510a, 510b, and so on (collectively, 510) . Each separator member has a baffle plate 160 extending parallel to the disks 122 as previously described, as well as a disk edge portion 512 which is thicker than the baffle plate 160. In fact, the disk edge portions 512 are thick enough to join adjacent pairs of the baffle plates 160. Each separator member 510 rests on top of the disk edge portion 512 of the separator member below it. This construction allows disk packs with any number of disks to be used in the tests, merely by stacking the desired number of separator members on top of each other.

Because of the cross-section taken in Figs. 2, 4 and 5, only part of each of the separator members 510 is actually visible in these figures. Fig. 6 is a top view of one of the separator members 512, and Fig. 7 is a cross-sectional view taken at lines 7-7 of Fig. 6. The cross-hatched region 710 of Fig. 7 represents the cut-through portion of the separator member 510, and is the only portion visible in Figs. 2, 4 and 5. Fig. 7 also shows the view looking back from the line 7-7 (i.e., looking upward in the drawing of Fig. 6), and therefore also shows a portion 712 of the baffle plate 160 and a portion 714 of the disk edge portion 512.

Referring to Fig. 6, the position of one of the disks 122 when the baffle assembly is engaged is shown as dotted region 610. It can be seen that the inner surface 154 of the disk edge portion 512 of the separator member 510 is concentric with the disk position and spaced closely beyond the edge of the disk position 610. The concentric nature of the surface 154 extends for a portion of arc of the disk position 610, specifically approximately 180° of arc. The purpose of the disk edge portion 512 is to minimize airflow into and out from the region between disks, so the wall 154 is made as close as possible to the edge of disk position 610, allowing for disk manufacturing tolerances and lateral vibrations of the disks while spinning on the spinstand. A typical disk edge spacing might be on the order of 5 mils . Because the purpose is to block lateral airflow, it would be desirable to extend the disk edge portion 510 through all 360° of arc of the disk position 610. This is not possible in a test instrument such as that described herein, however, because of the need for the separator members 510 to be removable relative to the spindle. Thus, the actual shape of the disk edge portion 510 as shown in Fig. 6 is that of a U. While the inner surface 154 of the disk edge portion 512 in Fig. 6 is concentric with and spaced from the outer edge of the disk position 610 through approximately 180° of arc of the disk position 610, it will be appreciated that some benefit will be obtained even if it is concentric with and spaced from the outer edge of the disk position 610 through a smaller portion of arc of the disk position 610.

The baffle plates 160 are desirably made as thick as possible without touching the lower surface of the disk position above the baffle plate 160 or the upper surface of the disk position below the baffle plate 160. Since only the laminar airflow adjacent to the disk surfaces and for the first approximately 10 microinches away from the disk surfaces is beneficial, it would be desirable to provide baffle plates 160 which are spaced from the disk position surface by only 10 microinches. Such close spacing is not practical, however, since accommodations must be made for disk thickness and flatness manufacturing tolerances as well as disk wobble during operation. Such tight spacing also tends to significantly increase the air friction between the baffle plate surface and the adjacent disk surface, thereby necessitating greater spindle drive power and undesirable heating of the air. Therefore, in the embodiment described herein, the baffle plates are designed to be spaced from the surfaces of adjacent disk positions by approximately 3-10 mils.

The baffle plates above the top disk of a disk pack and below the bottom disk of a disk pack are not as important as those positioned between disks of the disk pack, and therefore might be omitted in some embodiments. Nevertheless, they do provide some benefit and therefore are included in the embodiment described herein. In addition, these baffle plates might be of a different thickness than those disposed between disk platters, because their thickness is not restricted by the spacing between platters. Again, however, in the embodiment described herein, all of the separator members 512 are identical due to considerations of uniformity in fabrication. In order to reduce the mass of spinning air adjacent to the disks as much as possible, it would be desirable for the baffle plates 160 to cover the entire surface of the disk position 610, excluding a center hole for the spindle assembly 114. However, in order to accommodate the requirement that the baffle plates 160 be removable relative to the spindle assembly 114, it is advantageous that the baffle plate 160 have a cut-out region which is at least as wide as the diameter of the spindle assembly, and extends from the center hole all the way to an edge of the baffle plate 160. In one embodiment, such cut-out region is bounded on both sides by parallel straight lines and symmetrically straddles a centerline drawn between the rotational centerpoint 124 of the spindle assembly 114 and the rotational centerpoint 136 of the actuator assembly 125.

Fig. 8 is a top view of a separator member 810 having such a cut-out region 812. The centerline is indicated as 814, and the two lines 816 and 818 bounding the cut-out region 812 are straight and parallel and extend from the center hole 820 in the baffle plate 822 all the way to the edge of the baffle plate 822. It is desirable that the baffle plate cover at least a 180° sector of the disk 610 position, and one way that the baffle plate 122 can be made removable from the spindle assembly 114 is to choose a shape for the baffle plate 822 which does not cover more of the disk position 610 than that covered by the baffle plate 822 in Fig. 8.

While the cut-out region 812 in the baffle plate 822 might be sufficient to accommodate a head stack assembly whose range of motion is entirely radial with respect to the disk position 610, it might not be sufficient to accommodate a rotary actuator such as those used commonly on modern disk drives .

Fig. 9 is a top view of a separator member 910 having a baffle plate 912 which covers the entire disk position 610 except for a center hole 914 and a cut-out region 916 which is large enough to accommodate not only the spindle assembly as the separator member is removed laterally therefrom, but to accommodate also the arcuate range of motion 918 of the HSA 126. The cut-out 916 extends from the center hole 914 all the way to the edge of the baffle plate 912, and is bounded on one side by a line 920 which is straight and parallel to the centerline 814 and separated from the centerline 814 by a little more than one-half the diameter of the spindle assembly 114. The cut-out region 916 is bounded on the other side by a line 922 which extends from the center hole 914 to the disk edge portion 512, at an angle which is far enough away from the line 920 to avoid the range of motion 918 of the HSA 126.

The separator member 910 is useful if the only head stack assemblies that are to be tested are so- called "normal" HSA's, for which the disks spin in a counter-clockwise direction. Some HSA's, however, are manufactured to be "reverse-mounted", in which case the disks spin in a clockwise direction. A reverse-mounted head stack assembly would be mounted on the spinstand 100 such that the head arms 128 point in the counterclockwise direction of the disk instead of the clockwise direction as shown in Fig. 9. In order to accommodate reverse head stack assemblies, a different separator member such as 1010 shown in Fig. 10 would be used. The separator member 1010 is a mirror image of the separator member 910 of Fig. 9. Instead of providing two different types of separator members 910 and 1010, the separator member 510 of Fig. 6 accommodates both types of head stack assemblies. The separator member 510 is slightly less effective than separator member 910 or 1010 at reducing non-repeatable runout, but avoids the need for two different kinds of separator members for a test instrument intended to be able to test both normal- mounted and reverse-mounted head stack assemblies. It can be seen that the line 612 bounding the cut-out region 614 of the separator member 510 is the same as the line 922 bounding the cut-out region 916 of separator member 910 (Fig. 9) , and the line 616 bounding the cut-out region 614 of separator member 510 (Fig. 6) is the same as the line 1012 bounding the cutout region 1014 of the separator member 1010 (Fig. 10) . It can be seen further that the cut-out region 614 (Fig. 6) is symmetrical about the centerline 814. The baffle plate 160 of the separator member 510 covers more than a 180° sector of the disk position 610, but less than a 270° sector, in both cases excluding the center hole. Stated yet another way, the cut-out region 614 is larger than a 90° sector of the disk position 610 which symmetrically straddles the centerline 814.

Several features of the spinstand 100 described herein serve to help reduce the amount of turbulent airflow adjacent to the disks in a disk pack, and ultimately reduce the NRR to an acceptable level. While each feature provides a benefit when used alone, the greatest benefit is achieved when all of the features are employed together.

First, by providing a disk edge portion on the separator members which has an inner surface concentric with an closely spaced outside the outer edge of the rotating disks, for at least a portion of arc of the disks, the amount of air entering to and between the disks from the sides is minimized.

Second, the spinstand creates a controlled environment for the disk pack by forming a chamber or shroud which entirely encloses the disk pack when in the fully engaged position.

Third, the mass of air spinning between the disks in the disk pack and closely adjacent to the upper and lower surfaces of the top and bottom disks, is minimized by placing a baffle plate between each of the disks and, optionally, above the top-most disk and below the bottom-most disk of the disk pack. Each baffle plate preferably covers as much of the disk position as possible, except for a cut-out for the center hole and for lateral removability relative to the spindle assembly, and for avoiding the range of motion of each type of head stack assembly which the spinstand is to be used for testing. By reducing the mass of air spinning between the disks, the turbulence causing the non-repeatable runout is reduced as well.

Finally, because the spinstand 100 is a test instrument for testing disk drive components, and not a production disk drive, the separator members are made in such a way as to be removable relative to the spindle assembly so that disks in the disk pack can be replaced as needed during testing.

The foregoing description of the preferred embodiments of the present invention has been provided for the purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise forms disclosed. Many modifications and variations will be apparent to practitioners skilled in this art.

For example, whereas the baffle plates illustrated in the drawings are solid except for the cut-outs, it will be appreciated that baffle plates in other embodiments might contain holes, slots or other features. As another example, whereas the baffle plates shown in the drawings are stationary relative to the spinstand base 110, this is not absolutely necessary. The baffle plates would provide some improvement even if they were to rotate about the spindle assembly, as long as their rotational speed is less than that of the disks themselves . A method would be devised to prevent the baffle plates from interfering with the head arms of the head stack assembly under test . As yet another example, whereas the baffle plates shown in the drawings are unitary with the disk edge portions of the separator members, it will be appreciated that in other embodiments they can be separate. In addition, the disk edge portions of the individual separator members could be replaced by a unitary wall having an inside surface which is similar to that of the baffle wall 152 (Fig. 2) . Moreover, if the number of required baffle plates is fixed, all of the baffle plates and disk edge portions can be made as a single unitary structure.

As yet another example, whereas the baffle plates are shown in the figures as being anchored at their outer edge (due to their unitary construction with the disk edge portions) , the baffle plates could instead be anchored at the spindle or at another one of the edges of the baffle plate.

As yet a further example, whereas the baffle plates are made removable in the above-described embodiments by making them movable relative to the spinstand base 110, in another embodiment the baffle plates could be made removable instead by making the spindle assembly movable relative to the spinstand base 110. What is significant is that the baffle plates be removable relative to the spindle assembly, not that one or the other of the baffle plates and spindle assembly be movable relative to the spinstand base 110.

As yet another example, whereas the embodiments described herein involve magnetic disks and magnetic disk heads, aspects of the invention would apply also to other types of spinning disk test systems, such as optical disk drive component testers.

The embodiments described above were chosen and described in order to best explain the principles of the invention and its practical application, thereby enabling others skilled in the art to understand the invention for various embodiments and with various modifications as are suited to the particular use contemplated. It is intended that the scope of the invention be defined by the following claims and their equivalents .

Claims

CLAIMS 1. Spinstand apparatus, comprising: an actuator shaft for mounting a disk head actuator assembly having a disk head; a spindle assembly for rotatably securing a disk; and removable means for reducing non-repeatable runout of said disk head relative to said disk while said disk spins on said spindle assembly.

2. Spinstand apparatus, comprising: a spindle assembly for rotatably securing a disk having a disk surface; and removable means for reducing the mass of air that is subject to turbulence adjacent to said disk surface while said disk spins on said spindle assembly.

3. Apparatus according to claim 2 , wherein said removable means comprises : a baffle plate; and mounting means for removably mounting said baffle plate parallel to and slightly spaced from said disk surface.

4. Apparatus according to claim 3 , wherein said disk has an outer edge, and wherein said removable means further comprises removable blocking means for blocking lateral air flow between a region adjacent to said disk surface and a region radially beyond the outer edge of said disk.

5. Apparatus according to claim 2 , wherein said disk has an outer edge, and wherein said removable means comprises : blocking means for blocking lateral air flow between a region adjacent to said disk surface and a region radially beyond the outer edge of said disk; and mounting means for removably mounting said blocking means concentrically with and spaced slightly from the outer edge of said disk through at least a portion cf arc of said outer edge of said disk.

6. Spinstand apparatus for use in testing disk drive components, including a rotating disk pack having at least a first rigid disk, comprising: a spinstand base; a spindle assembly for securing said first disk in a first disk position above said base and rotatably with respect to said base; and a first baffle member extending parallel to said first disk position and spaced above said first disk position by a distance which is large enough to allow laminar air flow across said first disk but not large enough to allow substantial turbulent air flow adjacent to said first disk, said first baffle member being removable relative to said first disk position to allow replacement of said first disk.

7. Apparatus according to claim 6, further comprising said disk pack.

8. Apparatus according to claim 6, wherein said first baffle member is spaced above said first disk position by approximately 3-10 mils.

9. Apparatus according to claim 6 , further comprising a second baffle member extending parallel to said first disk position and spaced below said first disk position by a distance which is large enough to allow laminar air flow across said first disk but not large enough to allow substantial turbulent air flow adjacent to said first disk.

10. Apparatus according to claim 9, wherein said first disk position has an outer edge, further comprising a disk edge portion having an inner surface which is concentric with and spaced from said outer edge through at least a portion of arc of said first disk position.

11. Apparatus according to claim 6, wherein said first baffle member comprises a rigid plate.

12. Apparatus according to claim 6, for use with a head arm assembly which, when engaged, has a predetermined range of motion across said first disk, wherein said first baffle member is shaped to avoid said predetermined range of motion.

13. Apparatus according to claim 6, for use with a head arm assembly which, when engaged, has a predetermined range of motion across said first disk, said predetermined range of motion being arcuate about a rotational centerpoint, said spindle assembly also having a rotational centerpoint and further having an outer edge, further comprising a mount on said base for mounting said head arm assembly rotatably about the rotational centerpoint of said head arm assembly, and wherein said first baffle member comprises a plate that covers more than half of said first disk position, said plate having a cut-out region that covers at least a working region bounded circumferentially on one side by a first line extending from the edge of said spindle assembly and parallel to a centerline extending from the rotational centerpoint of said spindle assembly to the rotational centerpoint of said head arm assembly, and on the other side by a second line extending from the edge of said spindle assembly and at an angle large enough from said centerline to avoid the range of motion of said head arm assembly.

14. Apparatus according to claim 6, for use with head arm assemblies of first and second types each having a head arm and further having, when engaged, a respective predetermined range of motion across said first disk, the predetermined range of motion of both of said first and second types being arcuate about the rotational centerpoint of said head arm assembly, further comprising a mount on said base for mounting said head arm assembly rotatably about said rotational centerpoint of said head arm assembly, said spindle assembly also having a rotational centerpoint and further having an outer edge, the range of motion of head arm assemblies of said first type maintaining the head arm on a first side of a centerline extending from the rotational centerpoint of said spindle assembly to the rotational centerpoint of said head arm assembly, and the range of motion of head arm assemblies of said second type maintaining the head arm on a second side of said centerline opposite said first side of said centerline, and wherein said first baffle member comprises a plate that covers more than half of said first disk position, said plate having a cut-out region that covers a least a working region straddling said centerline, said working region bounded on said first side of said centerline by a first line extending from the outer edge of said spindle assembly at an angle large enough from said centerline to avoid the range of motion of head arm assemblies of said first type, and bounded on said second side of said centerline by a second line extending from the outer edge of said spindle assembly at an angle large enough from said centerline to avoid the range of motion of head arm assemblies of said second type.

15. Apparatus according to claim 6 , wherein said first baffle member comprises a plate having a cut-out that covers at least 90 degrees of arc and further has a center hole large enough to accommodate said spindle assembly.

16. Apparatus according to claim 15 , wherein said plate covers at least 180 degrees of arc, with the exception of said center hole.

17. Apparatus according to claim 6, wherein said rotating disk pack further has a second rigid disk, said spindle assembly securing said second disk in a second disk position above and parallel to said first disk, wherein said first baffle member extends between said first and second disk positions.

18. Apparatus according to claim 17, wherein said second disk has a lower surface and wherein said first baffle member is spaced below said lower surface by a distance which is large enough to allow laminar air flow across said lower surface but not large enough to allow substantial turbulent air flow adjacent to said lower surface.

19. Apparatus according to claim 18, wherein said second disk further has an upper surface, further comprising a second baffle member extending parallel to said second disk position and spaced above said second disk position by a distance which is large enough to allow laminar air flow across said upper surface of said second disk but not large enough to allow substantial turbulent air flow adjacent to said upper surface of said second disk, said second baffle member being removable relative to said second disk position to allow replacement of said second disk.

20. Apparatus according to claim 19, wherein said first disk has a lower surface, further comprising a third baffle member extending parallel to said first disk position and spaced below the lower surface of said first disk position by a distance which is large enough to allow laminar air flow across the lower surface of said first disk but not large enough to allow substantial turbulent air flow adjacent to the lower surface of said first disk.

21. Apparatus according to claim 6, further comprising a baffle holder to which said first baffle member is affixed, said baffle holder being removable relative to said first disk position to allow replacement of said first disk.

22. Apparatus according to claim 21, wherein said baffle holder is mounted on said base slidably relative to said first disk position in a plane parallel to said first disk position.

23. Spinstand apparatus for use in testing disk drive components, including a rotating disk pack having at least a first rigid disk having upper and lower surfaces, comprising: a spinstand base; a spindle assembly for securing said first disk above said base and rotatably with respect to said base; and a baffle assembly including first and second plate- like baffles, said baffle assembly having an engaged position relative to said spindle assembly and being removable relative to said engaged position, wherein said first plate-like baffle is, when said first disk is secured to said spindle assembly and said baffle assembly is in said engaged position, parallel to and spaced above the upper surface of said first disk by a distance which is large enough to allow laminar air flow across the upper surface of said first disk but not large enough to allow substantial turbulent air flow adjacent to the upper surface of said first disk, and wherein said second plate- like baffle is, when said first disk is secured to said spindle assembly and said baffle assembly is in said engaged position, parallel to and spaced below the lower surface of said first disk by a distance which is large enough to allow laminar air flow across the lower surface of said first disk but not large enough to allow substantial turbulent air flow adjacent to the lower surface of said first disk.

24. Apparatus according to claim 23, wherein said first disk has an outer edge, wherein said baffle assembly further includes a disk edge portion having an inner surface which, when said first disk is secured to said spindle assembly and said baffle assembly is in said engaged position, is concentric with and spaced from the outer edge of said first disk through at least a portion of arc of said first disk.

25. Apparatus according to claim 24, wherein said disk edge portion vertically joins said first and second plate-like baffles.

26. Apparatus according to claim 23, further comprising a slider mounted on said base, said baffle assembly being mounted to slide on said slider in a plane parallel to said plate-like baffles.

27. Apparatus according to claim 26, wherein said slider has a first position in which said baffle assembly is in said engaged position, and a second position in which said plate-like baffles are sufficiently distant from said spindle assembly such that disks of said disk pack can be moved vertically freely on said spindle assembly.

28. A baffle assembly for use in testing disk drive components, including a rotating disk pack having at least a first rigid disk having upper and lower surfaces, comprising: a plurality of spaced parallel plate-like baffles; a respective disk edge portion between and vertically joining each adjacent pair of said plate- like baffles, said disk edge portions each having a circularly shaped inner surface extending through less than a full circle.

29. A baffle assembly according to claim 28, wherein at least a first one of said plate-like baffles has a center hole and further has a cut-out region extending from said center hole to an edge of said first baffle.

30. A baffle assembly according to claim 29, further comprising a slider oriented to allow said baffle assembly to slide in a first dimension, wherein said cut-out region at least covers a working region bounded by a centerline extending radially in said first dimension from said center hole and by a first bounding line extending from an edge of said center hole and at a first acute angle to said centerline.

31. A baffle assembly according to claim 30, wherein said cut-out region is bounded by said first bounding line and a second bounding line extending from an edge of said center hole at a second acute angle to said centerline, said first and second angles being symmetrical about said centerline.

32. Spinstand apparatus for use in testing disk drive components, including a rotating disk pack having at least first and second rigid disks, comprising: a spindle assembly for securing said first and second disks rotatably in respective first and second parallel disk positions; and a first baffle member extending parallel to and between said first and second disk positions, said first baffle member being removable relative to said spindle assembly to allow replacement of at least one of said first and second disks.

33. Apparatus according to claim 32, wherein said first disk has a first disk surface and said second disk has a second disk surface facing said first disk surface when secured by said spindle assembly, and wherein said first baffle member is, when said first and second disks are secured by said spindle assembly, spaced from each of said first and second disk surfaces by a respective distance which is large enough to allow laminar air flow across said first and second disk surfaces but not large enough to allow substantial turbulent air flow adjacent to said first and second disk surfaces.

34. Apparatus according to claim 32, further comprising said first and second disks.

35. Apparatus according to claim 32, wherein said first baffle member is spaced from each of said first and second disk positions by respective distances being between about 3 mils and about 10 mils.

36. Apparatus according to claim 32, further comprising a second baffle member extending parallel to said first disk position on the opposite side of said first disk position from said first baffle member.

37. Apparatus according to claim 36, further comprising a third baffle member extending parallel to said second disk position on the opposite side of said second disk position from said first baffle member.

38. Apparatus according to claim 36, wherein said disk pack further has a third rigid disk, said spindle assembly securing said third disk in a third disk position parallel to said first disk position on the opposite side of said second baffle member from said first disk position.

39. Apparatus according to claim 32, further comprising a baffle holder to which said first baffle member is affixed, said baffle holder being slidable relative to said first disk position in a plane parallel to said first disk position.

40. Apparatus according to claim 32, wherein said first disk position has an outer edge, further comprising a disk edge portion having an inner surface which is concentric with and spaced from said outer edge through at least a portion of arc of said first disk position.