Abstract:
An object of the present invention is to provide a lapping machine in which abrasive grains can be efficiently and completely removed from a lapping plate. In the lapping machine of the present invention, a lapping plate has a lapping face and rotates about a rotary shaft. A moving member has a wiping face extended in a longitudinal and moves, in a plane parallel to the lapping face of the lapping plate, in the direction perpendicular to the wiping face. A driving mechanism moves the moving member. With this structure, the moving member securely catches and removes foreign substances from the lapping plate. The foreign substances left can be completely removed in a short time and the working efficiency of the lapping steps can be highly improved.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to a lapping machine, more precisely relates to a lapping machine in which a work piece is lapped, in a plurality of lapping steps, with a plurality of kinds of abrasive grains. 
     In manufacturing steps of an MR head of a magnetic disk drive unit, a work piece is lapped so as to have a prescribed electric resistance. Conventionally, the work piece is lapped with one kind of abrasive grains. These days, compact and high density MR heads are required, and high lapping accuracy, e.g., 20-30 nm, is required. Thus, a plurality of lapping steps, i.e., a first (rough) lapping step to a.final (finish) lapping step, are executed. 
     In the manufacturing steps of the MR head, the work piece is lapped in three lapping steps: the first lapping step, an intermediate lapping steps and the final lapping step. A problem of the lapping steps is abrasive grains left on a lapping plate. A grain size of the abrasive grains in each lapping step is different. Namely, the grain size is changed from large grains to fine grains in order. If the abrasive grains of a former lapping step are left on the lapping plate, the work piece will be scratched or damaged in the next lapping step. As described above, the high lapping accuracy is required, so the problem of the abrasive grains left on the lapping plate cannot be ignored. Therefore, the abrasive grains of the former lapping step must be completely removed from the lapping plate. 
     Conventionally, the abrasive grains are washed off, from the lapping plate, with a large amount of water. The abrasive grains left on the lapping plate can be washed off, but it takes a long time to completely wash the lapping plate. Working efficiency is important for manufacturing the MR heads. The working efficiency of the conventional lapping machine cannot be higher. Further, it is difficult to perfectly remove the abrasive grains by water. 
     Note that, in some cases, a correction ring is attached to a lapping face of the lapping plate. The correction ring makes the lapping face flat. The correction ring removes the abrasive grains but cannot remove them completely. 
     SUMMARY OF THE INVENTION 
     An object of the present invention is to provide a lapping machine in which abrasive grains can be efficiently and perfectly removed from a lapping plate. 
     To achieve the object, the lapping machine of the present invention comprises: a lapping plate having a lapping face, the lapping plate rotating about a rotary shaft; a moving member having a wiping face extended in a longitudinal direction, the moving member moving, in a plane parallel to the lapping face of the lapping plate, in the direction perpendicular to the wiping face; and a driving mechanism for moving the moving member. 
     In the lapping machine of the present invention, the moving member securely catches and removes foreign substances, including abrasive grains, left on the lapping plate. In comparison with the manner of washing the lapping face with water, the foreign substances, including the abrasive grains, left can be perfectly removed in a short time and the working efficiency of the lapping steps can be highly improved. By improving the working efficiency, manufacturing cost can be reduced. 
     In the lapping machine, the moving member may be connected to a supporting shaft and capable of turning about the supporting shaft. With this structure, the moving member is capable of moving on the lapping plate with a circular track. 
     In the lapping machine, the supporting shaft may be located outside of an outer edge of the lapping plate. With this structure, the whole lapping face can be wiped and the foreign substances including the abrasive grains can be perfectly removed therefrom. 
     The lapping machine may further comprise a control mechanism for adjusting a pressing force which presses the moving member onto the lapping plate. With this structure, foreign substances including the abrasive grains can be securely removed. 
     The lapping machine may further comprise an adjusting mechanism for adjusting an angle between the moving member and the lapping face of the lapping plate. With this structure, foreign substances including the abrasive grains can be securely removed. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Embodiments of the present invention will now be described by way of examples and with reference to the accompanying drawings, in which: 
     FIG. 1 is an explanation view of a lapping machine of an embodiment of the present invention; 
     FIG. 2 is an explanation view of an inner structure of the lapping machine of the embodiment; and 
     FIGS. 3A and 3B are plan views of a lapping plate of another embodiment of the lapping machine of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings. 
     FIG. 1 shows a summarized structure of the lapping machine of the present embodiment. 
     The lapping machine has a base  10 . A lapping plate  12  is attached to the base  10 . A work piece  14  is set on the lapping plate  12 . The work piece  14  is pressed onto the lapping plate  12 . Slurry including abrasive grains is supplied onto the lapping plate  12  from a slurry supplier  16  so as to lap the work piece  14 . 
     In the lapping machine for manufacturing MR heads, minute electric current is passed through the work piece  14  when the work piece  14  is lapped. Amount of lapping the work piece  14  is controlled with detecting electric resistance of the work piece  14 . To precisely control the amount of lapping the work piece  14 , the abrasive grains whose grain size is 2μm are used in the first lapping step; the abrasive grains whose grain size is 1μm are used in the intermediate lapping step; the abrasive grains whose grain size is 0.18-0.2 μm are used in the final lapping step. 
     When the lapping step is changed, the slurry and the abrasive grains left on the lapping plate  12  are removed by a removing mechanism  20 . 
     In the lapping machine of the present embodiment, firstly the slurry and the abrasive grains left on the lapping plate  12  are washed off by water when the lapping step is changed. By employing the removing mechanism  20 , the slurry, the abrasive grains and grain carrier included in the slurry, e.g., amine, glycerin, can be compulsorily removed from a lapping face (an upper face) of the lapping plate  12 . The removing mechanism  20  is a feature of the lapping machine of the present embodiment. 
     The removing mechanism  20  comprises: a wiper  22 , which is an example of the moving member and which is located above the lapping plate  12 ; a driving mechanism  26  for moving the wiper  22  on the lapping face of the lapping plate  12  with a circular track; and an angle adjusting mechanism for always holding the wiper  22  in a plain parallel to the lapping face of the lapping plate  12 . 
     The wiper  22  includes a wiper arm  23 , which is extended to a position above the lapping plate  12 , and a wiping member  24 , which is fixed to the wiper arm  23 . The wiper  22  is moved on the lapping face of the lapping plate  12  rotating with the circular track so as to compulsorily remove foreign substances, e.g., the abrasive grains therefrom. Sizes of the wiper arm  23  and the wiping member  24  are designed to wipe the whole lapping face rotating. 
     A bottom face of the wiping member  24  contacts the lapping face of the lapping plate  12  so as to brush the lapping face and compulsorily remove the abrasive grains, etc. therefrom. Side faces of the wiping member  24  are wiping faces for pushing the foreign substances to remove. The wiping member  24  is made of many materials, e.g., cotton, sponge, rubber, plastics, and may be formed like a brush. 
     A detailed structure of the lapping machine of the present embodiment is shown in FIG.  2 . 
     The lapping plate  12  is rotatably supported by the base  10  with a bearing  30 . A motor  32  rotates the lapping plate  12 . The motor  32  is fixed to the base  10  and transmits its power to the lapping plate  12  via a belt and pulleys. 
     The driving mechanism  26 , which moves the wiper  22 , is inclinably held at a side portion of the base  10 . The driving mechanism  26  of the present embodiment is a robot cylinder unit. A rod  27  is extended from and retracted into the robot cylinder unit  26 . Further, the rod  27  is rotated about its own axis. One end of the wiper arm  23  is fixed to the rod  27 . With this structure, the wiper arm  23  can be moved close to and away from the lapping face of the lapping plate  12  and can be turned there above. 
     As described above, the robot cylinder unit  26  is held at the side porting of the base  10  by supporting arms  34   a  and  34   b . The supporting arm  34   a  is pivotably attached to an upper part of the base  10  to support an upper part of the robot cylinder unit  26 ; the supporting arm  34   b  is pivotably attached to a lower part of the base  10  with an actuator  36  to support a lower part the robot cylinder unit  26 . The actuator  36  moves the supporting arm  34   b  close to and away from a side face of the base  10 . Because the robot cylinder unit  26  is pivotably attached to the base  10  by the supporting arm  34   a , the supporting arm  34   a  is turned about a shaft  35  and the robot cylinder unit  26  is inclined when the actuator  36  moves the supporting arm  34   b.    
     While the lapping plate  12  is rotated to lap the work piece  14 , temperature of the lapping plate  12  rises due to friction, so that the lapping face is slightly deformed and location of the lapping face is slightly displaced. The actuator  36  adjusts a position or posture of the wiper  22  according to the displacement of the lapping face caused by the thermal deformation. The relationship between rising temperature of the lapping plate  12  and the displacement of the lapping face is previously known by experiment. The actuator  36  inclines the robot cylinder unit  26  according to the temperature of the lapping plate  12 , so that the wiper  22 , which contacts the lapping face of the lapping plate  12 , can be maintained parallel to the lapping face of the lapping plate  12 . 
     In the present embodiment, a thermos-sensor  38  is provided in the vicinity of the bearing  30 , which supports the lapping plate  12 , so as to detect the temperature of the lapping plate  12 . The temperature raises most in the vicinity of the bearing  30 . The actuator  36  is driven on the basis of data sent from the thermos-sensor  38 . Note that, a bimetal may be employed as the thermos-sensor  38 , and a piezo element may be employed as the actuator  36 . In this case, the piezo element may be driven, so as to control the posture of the wiper  22 , by a bimetal amplifier. The actual deformation of the lapping plate  12 , which is caused by the frictional heat, is minute, so the piezo actuator can sufficiently control the posture of the wiper  22 . 
     In the present embodiment, the angle adjusting mechanism  28  for adjusting the angle of posture of the wiper  22  includes: the mechanism for inclinably attaching the robot cylinder unit  26  to the base  10 ; the actuator  36  for inclining the robot cylinder unit  26 ; and the thermos-sensor  38  for controlling the actuator  36 . 
     When the lapping step is changed, the removing mechanism  20  is driven to compulsorily remove the foreign substances, e.g., the slurry, the abrasive grains, from the lapping face of the lapping plate  12 . 
     In the present embodiment, the foreign substances on the lapping plate  12  are washed off by water and removed by the on removing mechanism  20 . Especially, by employing the removing mechanism  20 , the wiper  22  can efficiently compulsorily remove the foreign substances from the lapping face of the lapping plate  12 . 
     Even if the lapping face is displaced by rising temperature of the lapping plate  12 , the angle adjusting mechanism  28  maintains the wiper  22  parallel to the lapping face and the wiper  22  securely contacts the lapping face, so that the wiping member  24  securely wipes the lapping face and perfectly removes the foreign substances therefrom. 
     The driving mechanism  26  turns the wiper  22  about the rod  27  so as to move the wiping member  24 , in a fan-shaped area, on the lapping plate  12  rotating. By the movement of the wiping member  24 , the foreign substances can be removed from the lapping plate  12 . 
     The rotational axis of the wiper  22  is located outside of the lapping plate  12 . With this structure, the whole lapping face can be wiped. If the rotational axis of the wiper  22  is located in the lapping plate  12 , the foreign substances near the rotational axis is moved round the axis and cannot be removed. 
     The driving mechanism  26  adjusts the position or a wiping area of the wiper  22  and adjusts a pressing force, which presses the wiper  22  onto the lapping face of the lapping plate  12 , by adjusting a projected length of the rod  27 . The pressing force can be adjusted according to, for example, a material of the wiping member  24 . 
     The foreign substances are washed off by water and compulsorily removed by the removing mechanism  20 , the foreign substances can be efficiently and perfectly removed from the lapping plate  12 . Therefore, the lapping steps can be easily and efficiently changed. 
     The mechanism of removing the foreign substances is not limited to the wiper  22 , which is turned about the rotational axis. Another embodiment is shown in FIGS. 3A and 3B. The wiper  22  may be moved linearly as shown in FIGS. 3A and 3B. In FIG. 3A, a linear-shaped wiping member  24  is reciprocally moved in the direction A—A′. In FIG. 3B, a curved wiping member  24  is linearly reciprocally moved in the direction B—B′. 
     In the present embodiments, the lapping machine has the mechanism for correcting the thermal deformation of the lapping plate  12 , so the work piece  14  can be highly precisely lapped with very fine abrasive grains. The lapping machine automatically laps the work piece  14  with detecting amount of lapping, and the thermal deformation of the lapping plate  12  can be automatically corrected. With these functions, the lapping machine capable of automatically changing the lapping steps can be realized. 
     In the above described embodiments, the lapping machine laps the work piece of the MR head. But the work piece is not limited to the MR head. The present invention may be applied to many types of lapping machines, in which a plurality of the lapping steps are executed. 
     The invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.