LEAF SPRING IN A TAPER LAPPING FIXTURE
Original Publication Date: 1999-Oct-01
Included in the Prior Art Database: 2003-Jun-19
The conventional taper lapping tool incorporates a clamping pin that seats the quad carrier against a tuned back plate to lap the taper into the solid row of sliders at the desired angle. With the cover engaged, the compliant pins contact the top of the carrier encouraging direct contact between the leading edge of the row and the lapping plate. The compliant pin force is applied through compressed coil springs. The contact force applied to the carrier is adjustable by means of controlling the compression of the coil springs. The current lapping fixture introduces several variables that affect the taper angle and taper length distribution for the length of the row. The adjustable back plate angle affects the taper angle for the row. With the ability to adjust comes the unreliability of the angle to drift more readily. Also, the design of the compliant pin scheme introduces several areas for irregular friction losses that will contribute to higher standard deviation of lapped taper length. The coil springs experience interference along the walls of the counterbore that contain them. The enlarged ends of the pins also experience frictional losses against these same walls. The length of the pins experiences frictional losses at the orifices through which they pass. Because of the long length, these pins also do not maintain alignment stability. The new eliminated the ability of the back plate to drift through slippage. The newly designed taper fixture contains a back plate rigidly mounted to the base of the fixture with no adjustment. The plate is machined to the desired angle in reference to the hard lapping pads that ride on the lapping plate. Drift of the angle plate from the desired taper angle is carefully monitored through control charts. In the event of drift of the taper angle from the target angle, the pads of the fixture are ground mechanically in reference to the back plate to recover to the target taper angle. To reduce or eliminate any frictional losses to the quad carrier, leaf springs are incorporated into the fixture to apply the desired force to the carrier to obtain the desired taper length. The leaf springs are rigidly mounted to the fixture with the free ends applied to the carrier. The force application is controlled through an adjustable screw offset that is applied to the leaf spring between the rigid fixture mount and carrier contact positions. With this configuration, the only frictional losses introduced are the movement of the leaf spring carrier contacts relative to the carrier. The contact tips are made of a self-lubricating plastic to minimize this effect. With this leaf spring mechanism scheme, the fixture has greater repeatability in applying the taper length and angle. The new design uses fewer parts and performs with a longer interval between adjustments.