Abstract:
A suspension baseplate is stamped at its distal end to which the load beam is mounted. The stamping operation smoothes out roughness in the edge of the baseplate and lowers its height slightly so that, along the line on the baseplate which last contacts the load beam as the load beam is leaving the baseplate, that line on the baseplate is smooth and free of burrs and similar defects. By eliminating burrs on the surface to which the load beam is mounted, variations in the pitch and twist of the load beam are reduced.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority from U.S. Provisional Patent Application No. 62/152,930 filed Apr. 26, 2015, the disclosure of which is incorporated by reference as if set forth fully herein. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to the field of suspensions for disk drives. More particularly, this invention relates to the field of a disk drive suspension whose baseplate has a stamped distal tip. 
     2. Description of Related Art 
     Magnetic hard disk drives and other types of spinning media drives such as optical disk drives are well known. Hard disk drives generally include a spinning magnetic disk containing a pattern of magnetic ones and zeroes on it that constitutes the data stored on the disk drive, as well as a disk drive suspension to which a magnetic head slider is mounted proximate a distal end of the load beam.  FIG. 1  shows a generalized dual stage actuated (DSA) hard disk drive suspension  10  including a baseplate or mount plate  20 , one or two PZT microactuators  14 , a load beam  30  including a spring or hinge portion  32  and a beam portion  34 , and a flexure gimbal assembly  36  to which a head slider (not shown) carrying a read/write transducer head is attached at the distal end of the beam portion. The read/write head writes data to, and reads data from, the data medium which is a spinning magnetic disk drive, or possibly optical medium in an optical disk drive. Baseplate  20  includes both a mounting portion  21  which is mounted to an actuator arm (not shown) via swage hub  28 , and a distal tip  22  to which the hinge  32  is typically spot welded at weld points  38 . Typically hinge  32  is formed integrally with beam portion  34 , so typically load beam  30  is understood to include spring  32 . However, spring  32  and beam portion  34  can be formed separately and then welded together. A number of structural variations from the generalized construction shown in  FIG. 1  are possible. 
       FIG. 2  is an oblique view of a the baseplate  20  of  FIG. 1 . Baseplate  20  is typically die cut or otherwise cut in a metal cutting operation from a relatively thick stainless steel plate. In contrast, hinge  32 , beam portion  34 , and the stainless steel portion of flexure gimbal assembly  36  are usually etched from thin sheets of stainless steel. 
     In standard suspension terminology and as used herein, the term “proximal” means closest or closer to the end of the suspension which is mounted to the actuator arm; in contrast, the term “distal” means closest or closer to the cantilevered end of the suspension, i.e., the end of the suspension that is opposite the actuator arm. 
     SUMMARY OF THE INVENTION 
     Die cutting and other metal cutting technologies inevitably produce certain types of defects and irregularities at cut edges, such as burrs, dents, rounding, and other irregularly shaped features. Such irregularities in cut edges will be collectively referred to herein and in the appended claims as “burrs” for simplicity of discussion.  FIG. 3  is a closeup of the area of baseplate  20  indicated in  FIG. 2  at the distal end of baseplate  20 , with the burrs  25  that result from the metal cutting operation shown in exaggerated form. These burrs  25  can cause the load beam  30  to twist or adopt an initial angle that is out of specification or renders the completed suspension unable to meet its final twist or angle specification without an additional adjusting step. The distal tip  22  of baseplate  20  is thus an important part of the suspension assembly, because it affects the starting twist angle of load beam  30 . 
     These defects that are artifacts of the metal cutting operation can be largely eliminated, or their effects on the suspension eliminated or at least ameliorated, by stamping or coining the distal tip  22  of the baseplate tip before mounting load beam  30  to the tip  22 , such that the last portion of the baseplate tip  22  that load beam  30  touches before it leaves the baseplate  20  is a relatively clean, smooth, and burr-free stamped line. Coining is a process that causes the baseplate material, which is stainless steel in most cases, to be compressed and to flow slightly. The stamped shelf is significantly smoother, flatter, and more free of the burrs that are artifacts of the metal cutting process by which the baseplate was formed, than are other edges which have not been stamped. Stamping or coining the distal tip of the baseplate thus helps to eliminate or at least greatly reduce burrs, and thus helps to eliminate one source of variability in the final load beam twist or initial angle, thus making the manufacturing process more precise, repeatable, and reliable. If burrs occur at the cut edge, the coining separates that cut edge from contact with the load beam. Any burrs on that cut edge do not touch the load beam, and thus do not affect the assembly of the suspension and its final shape. The line of departure of the load beam from the mount plate is defined by the coining, not by the cut edge. This increases the accuracy of the suspension and decreases the need for after-assembly adjusting such as by mechanical or laser adjusting of the pitch static attitude (PSA) of the suspension. 
     In one aspect, therefore, the invention is of a suspension for a disk drive in which the load beam is stamped or coined at its distal tip thus forming a stamped or coined shelf in the distal tip baseplate. The stamped shelf includes an edge thereof which defines a line of departure where the load beam leave the baseplate. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a top plan view of a generalized dual stage actuated (DSA) hard disk drive suspension according to the prior art. 
         FIG. 2  is an oblique view of a the baseplate of  FIG. 1 . 
         FIG. 3  is a closeup of the baseplate area indicated in  FIG. 2  at the distal end of the baseplate, with the burrs that result from the metal cutting operation shown in exaggerated form. 
         FIG. 4  is an oblique view of a baseplate after the distal edge has been stamped according to an embodiment of the invention. 
         FIG. 5  is a closeup of the baseplate area indicated in  FIG. 4  at the stamped distal end of the baseplate, with the burrs that result from the metal cutting operation shown in exaggerated form. 
         FIG. 6  illustrates the area of the baseplate shown in  FIG. 5 , but also including a load beam mounted on the baseplate, with the load beam shown in phantom. 
         FIG. 7  is a side elevation view of the baseplate and load beam of  FIG. 6 . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       FIG. 4  is an oblique view of a baseplate  120  according to an embodiment of the invention after the distal tip or end  122  at the distal edge of has been stamped. The distal tip  122  is distal of mounting portion  121  which is mounted to the disk drive assembly&#39;s actuator arm via the swage hub. The stamping produces a flat stamped or coined region  140  that defines a smooth and relatively burr-free stamped shelf  128  formed in tip  122 . Preferably stamped shelf  140  extends all the way from one lateral end  127  of tip  122  to the opposite lateral end  129 . The coined region  140  defines an edge  142  on which the load beam will be mounted. Preferably an entire lateral width of load beam at spring region  32  extends at last partially over the stamped portion  140  of the baseplate along a line at which load beam  30  last makes contact with baseplate  20 . 
       FIG. 5  is a closeup of the area of baseplate  120  indicated in  FIG. 4  at the stamped distal tip  122  of the baseplate  120 , with the burrs  25  that result from the metal cutting operation performed on cut edges  26  shown in exaggerated form. Lip  144  begins at edge  142  of the coined region  140 . A stamped edge  146  at a distal end of the stamped shelf  128  defines a coined distal edge of baseplate  120 . Top edge  142  of lip  144  defines a line of departure where spring region  32  last touches baseplate  120  as it extends distally therefrom and over the coined region  140 . The stamping operation has rendered top edge  142  substantially free of burrs  25 , or at least substantially smoother and flatter than corresponding bottom edge  148  which lies directly below edge  146  and which still has burrs  25  due to the metal cutting operation. Similarly, edges  142  and  146  are substantially smoother and flatter than other cut edges such as edge  26  that have not been stamped. 
     As utilized herein, terms such as “about,” “substantially,” and “approximately” are intended to allow some leeway in mathematical exactness to account for tolerances that are acceptable in the trade, or that would otherwise encompass a functionally equivalent variation. Accordingly, any deviations upward or downward from any value modified by such terms should be considered to be explicitly within the scope of the stated value. 
       FIG. 6  illustrates the area of the baseplate  120  shown in  FIG. 5 , but also including a spring region  32  of load beam  30  mounted on the baseplate, with spring region  32  shown in phantom. Spring region  32  is laser spot welded to baseplate at weld points  38 . Top edge  142  defines a line of departure where spring region  32  leaves distal tip  122  of baseplate  120 . The load beam extends at least partially over the coined region  140  of the baseplate. 
       FIG. 7  is a side elevation view of the baseplate and load beam of  FIG. 6 . 
     In a preferred embodiment the stamping is performed to a depth of 5-35% of the thickness of the baseplate  112 , such that the stamped region will have a thickness of 65-95% a nominal thickness of the baseplate, such as measured at an unstamped region adjacent the stamped region or at the mounting region  121  of the baseplate. For a typical baseplate of 0.150 mm thickness, the stamping would typically be performed to a depth of 0.010 mm to 0.050 mm. The position of stamped line  142  can be located just as accurately as cut edge  26 . Since stamped line  142  will be free of burrs, the stamping operation has allowed the twist and initial angle of the load beam  30  to be more accurately controlled, thus reducing the need for PSA adjust before the suspension is ready to be mounted to the actuator arm. 
     In another embodiment the load beam may be mounted on stamped shelf  128  rather than on top surface  29  of the baseplate, and the stamping is of a uniform depth such that the lateral halves, i.e., both the right and left halves, of spring  32  are at equal heights. That is, a first lateral half of the load beam is mounted on a first lateral half of the stamped shelf, and a second lateral half of the load beam opposite the first half thereof is mounted on a second lateral half of the stamped shelf, and first and second lateral halves of the stamped shelf being stamped to substantially equal depths such that the first and second lateral halves of the load beam lie at substantially equal heights. In another embodiment, only one half, for example, the right half, of a baseplate could be stamped so as to intentionally introduce a vertical offset in one load beam spring relative to the other, for reasons of reducing track misregistration as disclosed in U.S. Pat. No. 7,280,316 to McCaslin et al. and assigned to the assignee of the present application. In another embodiment, both the right and left halves of the baseplate are stamped, but to different depths, also in order to intentionally introduce a vertical offset. 
     The foregoing figures illustrate the invention as applied to a baseplate  120  in which PZT microactuators are mounted. The invention is also applicable to suspensions in which the baseplates do not have PZT microactuators mounted to them for moving a distal end of the baseplate, such as is the case for suspensions which are not DSA suspensions, or suspensions in which the PZT microactuator(s) used to effect fine movements of the head slider are mounted somewhere other than on the baseplate, such as on the load beam or at the gimbal. 
     More generally, the invention is applicable to any part of a suspension in which it is desirable and advantageous to make smoother a rough edge, such as for example but not necessarily a die cut metal edge. Such a rough edge can be made smoother be stamping a portion of the part that includes the rough edge, such as by stamping a small shelf or ledge into the part, or stamping a slightly rounded or angled portion into the part. The smoothing created by the stamping helps to not only eliminate small mechanical variations in alignment when one part is mounted to the now-stamped part, but also helps to reduce the possibility of small metal particles being fretted or dislodged during operation where a formerly rough (before stamping) portion of a part contacts another part, especially one that moves slightly during operation.