Head stack assembly gramload process capability improvement
View Patent ↗A method for measuring a gramload corresponding to a read/write head, where the head is an inner head of a plurality of heads in a head stack assembly (HSA), involves a measurement instrument having a plurality of cam-rods for systematically placing each of various heads in a preloaded state in order to measure the respective gramload of the heads. While an inner head's gramload is being measured, an adjacent inner head is configured in a supported state, and the cam-rod corresponding to the supported head transmits some additional force to the head whose gramload is being measured, e.g., via a common support arm for the adjacent inner heads. Therefore, this additional applied force is compensated for in order to provide more accurate gramload values.
1. A method for measuring a gramload corresponding to a read/write head, the method comprising:
using a measurement instrument comprising a cam-rod for placing said read/write head in a preloaded state, wherein said read/write head is a first inner head of a plurality of read/write heads in a head stack assembly and is coupled to a same arm as an adjacent second inner head;
placing said first inner head in said preloaded state using a first cam-rod;
placing said second inner head in a supported state using a second cam-rod, wherein said second cam-rod applies an additional force to said first inner head via said arm;
measuring, using said instrument, a measured gramload corresponding to said first inner head; and
computing an actual gramload corresponding to said first inner head by compensating for said additional force applied by said second cam-rod.
2. The method recited in claim 1 , further comprising:
computing, based on said actual gramload, a process capability index associated with a plurality of gramloads that correspond to respective read/write heads.
3. The method recited in claim 1 , further comprising:
determining said additional force applied by said second cam-rod.
4. The method recited in claim 3 , wherein said head stack assembly is a first head stack assembly, and wherein determining said additional force comprises:
using a second head stack assembly manufactured and assembled similarly to said first head stack assembly, wherein said second head stack assembly comprises a third inner head and a fourth inner head,
placing said third inner head in a preloaded state using said first cam-rod;
placing said fourth inner head in a supported state using said second cam-rod, wherein said second cam-rod applies an additional force to said third inner head via a arm to which both said third and fourth inner heads are coupled;
measuring, using said instrument, a first measured gramload corresponding to said third inner head;
removing said fourth inner head from said second head stack assembly;
measuring, using said instrument, a second measured gramload corresponding to said third inner head; and
computing said additional force based on the difference between said first measured gramload corresponding to said third inner head and said second measured gramload corresponding to said third inner head.
5. The method recited in claim 3 , further comprising:
inputting to a machine-executable routine a value characterizing said additional force.
6. The method recited in claim 1 , wherein compensating for said additional force applied by said second cam-rod comprises computing the difference between said measured gramload corresponding to said first inner head and said additional force applied by said second cam-rod.
7. A computer-readable medium storing one or more sequences of instructions, said instructions which, when executed by one or more processors, cause performance of:
computing a gramload corresponding to a read/write head, wherein said read/write head is a first inner head of a plurality of read/write heads in a head stack assembly and is coupled to a same arm as an adjacent second inner read/write head, wherein a measurement instrument comprising a cam-rod for placing said read/write head in a preloaded state outputs a measured gramload corresponding to said first inner head;
computing an actual gramload corresponding to said first inner head by computing the difference between said measured gramload corresponding to said first inner head and a force applied by a second cam-rod, of said instrument, which places said second inner head in a supported state while a first cam-rod, of said instrument, places said first inner head in a preloaded state; and
outputting said actual gramload corresponding to said first inner head.
8. The computer-readable medium recited in claim 7 , wherein said instructions further cause performance of:
receiving a value characterizing said force applied by said second cam-rod.