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  Lapping system with mutually stabilized lapping carriersUSPTO Application #: 20060228996Title: Lapping system with mutually stabilized lapping carriers Abstract: A lapping system for eliminating crowning in a surface to be lapped includes a first lapping carrier adapted to carry a first workpiece and a second lapping carrier adapted to carry a second workpiece. A stabilizer assembly interconnects the first and second lapping carriers in a mutually stabilizing arrangement that stabilizes the first and second workpieces against rotation. The stabilizer assembly includes first and second stabilizer arms extending between the first lapping carrier and the second lapping carrier. Each lapping carrier and an associated stabilizer arm collectively defines a fixture having a carrier portion and a stabilizer portion, and which may be generally T-shaped. One end of each stabilizer arm is cantilevered from its associated lapping carrier, while the free end of each stabilizer arm is pivotally mounted to the opposite lapping carrier. Downward lapping forces are applied independently to each lapping carrier. In an alternative embodiment, the stabilizer arm extending from the lapping carrier is mounted to an anchor that is not another lapping carrier. (end of abstract)
Agent: Walter W. Duft - Williamsville, NY, US Inventor: Robert G. Biskeborn USPTO Applicaton #: 20060228996 - Class: 451011000 (USPTO) Related Patent Categories: Abrading, Precision Device Or Process - Or With Condition Responsive Control, With Feeding Of Tool Or Work Holder The Patent Description & Claims data below is from USPTO Patent Application 20060228996. Brief Patent Description - Full Patent Description - Patent Application Claims
BACKGROUND OF THE INVENTION [0001] 1. Field of the Invention [0002] This invention relates to the manufacture of magnetic heads used in magnetic storage devices such as disk drives and tape drives. More particularly, the invention is directed to an improved lapping apparatus that reduces or eliminates rocking motion during the lapping of magnetic head wafers comprising multi-slider row bars. [0003] 2. Description of the Prior Art [0004] By way of background, the conventional fixturing of a magnetic head wafer workpiece for lapping can lead to an undesirable condition known as crowning. Crowning occurs when the row bar surface being lapped is allowed to rock during lapping, thus creating unwanted facets. FIGS. 1-4 (not to scale) are illustrative. These figures show a workpiece 2 secured in a lapping carrier 4 (sometimes referred to as a "magazine") that is in turn slidably mounted in a reference fixture 6 (sometimes referred to as a "nest"). The workpiece 2 is assumed to comprise a matrix of individual slider units arranged in a plurality of row bars. In FIG. 1, the row bars extend in a direction that is perpendicular to the plane of the figure. In FIG. 2, the row bars extend in a horizontal direction. [0005] The reference fixture 6 has a set of support pads 8 on the bottom thereof that rest on the surface of a lapping element 10. This arrangement allows the reference fixture 6 and the lapping carrier 4 to move up and down, and thereby follow the lapping element's surface contour. The reference fixture 6 includes a vertically-walled aperture 12 that slideably receives the lapping carrier 4. In order to properly orient the workpiece 2 relative to the surface of the lapping element 10, a lateral force "LF" is applied to the lapping carrier 4 such that it is urged against positioning pads 14 extending from one of the walls of the aperture 12. The pads 14 serve as vertical reference surfaces for the lapping carrier 4. As shown in FIG. 1, there are three positioning pads 14 extending from the left vertical wall of the aperture 12. The lateral force LF is applied by way of a plunger actuator 15 or other force-imparting element (e.g., a spring). A downward force "DF" is also applied to the lapping carrier 4 to urge the lapping face of the lowermost row bar against the lapping element 10. As shown in FIGS. 2 and 2A, the downward force DF is applied using transducers 16 that engage a loading frame 17 placed over the lapping carrier 4. To ensure that no lateral forces are imparted to the lapping carrier 4, the transducers 16 have spring-loaded ball elements 18 that engage polished surfaces 19 on the loading frame 17. FIG. 2 also shows the use of additional positioning pads 14 on the ends of the lapping carrier 4. [0006] FIG. 1 is representative of ideal conditions wherein the plunger 15 at all times urges the lapping carrier 4 against the pads 14. In this position, the workpiece lapping face 18 maintains a constant angle relative to the lapping element 10. Unfortunately, as shown in FIG. 4, frictional forces imparted by the lapping element 10 to the workpiece 2 can overcome the lateral force LF and cause the lapping carrier 4 to pivot away from its home position against the pads 14. This produces the crowning effect referred to above. [0007] In the fixture of FIGS. 1-4, crowning can be corrected by increasing the lateral force LF imparted to the lapping carrier 4 by the plunger 15. The problem with this standard technique for controlling crowning is that friction is increased between the lapping carrier 4 and the pads 14. This increased friction opposes the downward force DF applied to the lapping carrier 4 by the transducers 16, and can cause the lapping carrier to rotate about an axis that is perpendicular to the plane of FIG. 2, as shown by the arrows "R." This will result in non-uniform lapping across the row bar being lapped. [0008] It is to improvements in the lapping of magnetic head wafer modules that the present invention is directed. In particular, what is needed is a lapping system design that effectively controls crowning without increasing the downward forces required to produce a required lapping force or introducing non-uniform lapping effects. SUMMARY OF THE INVENTION [0009] The foregoing problems are solved and an advance in the art is obtained by a novel lapping system which in a first exemplary embodiment includes a first lapping carrier adapted to carry a first workpiece and a second lapping carrier adapted to carry a second workpiece. A stabilizer assembly interconnects the first and second lapping carriers in a mutually stabilizing arrangement that stabilizes the first and second workpieces against rotation. The stabilizer assembly includes first and second stabilizer arms extending between the first lapping carrier and the second lapping carrier. Each lapping carrier and an associated stabilizer arm may be thought of as collectively defining a fixture having a carrier portion and a stabilizer portion. Each fixture may have a generally T-shaped configuration or other geometry. One end of each stabilizer arm is cantilevered from its associated lapping carrier. The free end of each stabilizer arm is pivotally mounted to the opposite lapping carrier, which functions as an anchor for the fixture whose stabilizing arm it supports. This pivotal mounting can be provided by way of protrusions on the free ends of the stabilizer arms engaging corresponding depressions formed in the lapping carriers. Retainers are used to maintain the protrusions in engagement with the depressions. The depressions are situated in recesses formed in the lapping carriers. Each depression is situated above and in line with the workpiece held by its associated carrier. [0010] Lapping forces can be applied independently to each lapping carrier and the lapping force on one lapping carrier will not increase the lapping force on the other lapping carrier. The interconnecting stabilizer arms will substantially prevent rotation of the lapping carriers that would otherwise cause unwanted rocking of the workpieces. [0011] In a further exemplary embodiment of the invention a lapping fixture is provided by a lapping carrier and a stabilizing arm. The free end of the stabilizer arm is mounted to an anchor that is not a lapping carrier. Instead, the anchor is provided by any suitable structure having a pad for resting on the lapping surface that laps the workpiece held by the lapping fixture. Insofar as the anchor is not a lapping carrier, the pad is not a workpiece. [0012] In a further exemplary embodiment of the invention a reference fixture or "nest" is provided for maneuvering lapping fixtures according to the invention over the surface of a lapping element. BRIEF DESCRIPTION OF THE DRAWINGS [0013] The foregoing and other features and advantages of the invention will be apparent from the following more particular description of exemplary embodiments of the invention, as illustrated in the accompanying Drawings, in which: [0014] FIG. 1 is a side elevation view of a prior art lapping system in which a portion thereof is broken away to illustrate the fixturing of a workpiece for lapping; [0015] FIG. 2 is a cross-sectional view taken along line 2-2 in FIG. 1; [0016] FIG. 2A is an enlarged detail view showing a portion of the structure of FIG. 2 that is used for loading a workpiece against a lapping surface; [0017] FIG. 3 is a plan view of the prior art lapping system of FIG. 1; [0018] FIG. 4 is a side elevation view of the prior art lapping system of FIG. 1 showing how crowning can occur during lapping of the workpiece; [0019] FIG. 5 is a side elevation view of a lapping system according to an exemplary embodiment of the invention; [0020] FIG. 6 is a top plan view of the lapping system of FIG. 5; [0021] FIG. 7 is an enlarged cross-sectional view taken along line 7-7 in FIG. 6, with an intermediate section removed to reduce figure size; Continue reading... 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