Hologic Affirm - Page 87

Affirm Breast Biopsy Guidance System Service Manual
Appendix C: Hardware Range Calibration
MAN-05754 Revision 002 Page 75
9. Determine the maximum X-axis encoder count by moving the X carriage to the left
mechanical limit (as viewed from the front of the Biopsy Guidance Module). With the
carriage at the mechanical limit, use the Biopsy Control Module function "Set Xlimit
max" to store the encoder count.
Note
To avoid possible damage to the mechanism, the carriage must NOT be driven all the
way to the limit under power. Manually adjust the carriage until the limit is just
reached. This applies to all motorized axis.
10. Determine the minimum X-axis encoder count by moving the X carriage to the right
mechanical limit, the Biopsy Control Module function "Set Xlimit min" to store the
encoder count.
11. Repeat steps 9 and 10 for the Y-axis (Ylimit max is at the chest wall end of travel),
and for the Z-axis (Zlimit max is at the farthest end of travel from the breast tray).
The encoder counts corresponding to the mechanical limits are dependent on the
scale factors as determined in Step 8, and the design travel extents for each axis.
• X-axis: total travel = 81.0 mm
• Y-axis: total travel = 72.8 mm
• Z-axis: total travel = 161.0 mm
Assuming the potentiometer had been aligned at the exact center in Step 1
(corresponding to a count of 16384/2 = 8192) and the default scale factors apply, the
encoder counts at each of the limits are:
• X-axis: Xlimit max = 15984, Xlimit min = 400
• Y-axis: Ylimit max = 15195, Ylimit min = 1188
• Z-axis: Zlimit max = 15710, Zlimit min = 673
Because in practice the Step 1 alignment is not exact, the limit counts are defined by
ranges:
• X-axis: 15584 ≤ Xlimit max < 16383
0 < Xlimit min ≤ 800
• Y-axis: 14007 ≤ Ylimit max < 16383
0 < Ylimit min ≤ 2376
• Z-axis: 15037 ≤ Zlimit max < 16383
0 < Zlimit min ≤ 1346
Note
The limit counts determined should be checked to ensure that they are within these
ranges.