Rotation Limits - Planmeca Proline XC Technical Manual

Chapter D - ADJUSTMENT & CALIBRATION

4.3 Rotation limits

The rotating movement is controlled by two Hall detectors: one determines the start position
and the other the end position. The latter has no importance for the normal function because
the step motor drives the rotating unit according to the programmed number of steps The end
limit is of great importance in case of abnormal function, because it informs the processor that
the rotating unit has not reached the end position.
The start limit is adjusted so that the movement of the guidance wheel in the drawing groove
is symmetric to the groove. The distance of the boss of the wheel from the end of the groove
should be the same both when the movement starts and when it ends. The symmetricity of
the movement has more importance to the quality of the radiograph than the absolute length
of the movement which varies a little because of production tolerances.
Remove the necessary covers. Slide the ball phantom into the patient positioning mecha-
nism. Check that the y-line on the ball phantom is parallel to the line on the underside of the
alignment ruler according to instructions given in section 3.2 "Patient positioning mechanism
adjustment" on page D-21.
Remove the alignment pin. Select the test mode if you are not already in it.
Touch the ready field to drive the X-ray unit to the exposure position. Place the alignment
ruler in position between the primary and secondary collimator and write down the angle
between the ball phantom "start"-line and the alignment ruler.
Start to take a test exposure by pressing and holding down exposure button on the remote
control. Stop pressing the exposure button after about two seconds so that the rotating unit
stops moving. Place the alignment ruler in position between the primary and secondary colli-
mator and write down the angle between the ball phantom "end"-line and the alignment ruler.
The positions corresponding to end and start positions should not differ more than ± 1 mm.
The position of the start limit (Hall detector) can be changed by unscrewing the screws. This
should be repeated until the tolerance area is reached.
The adjustment of the end position is done after the start position has been adjusted.
No special tools are needed. The end limit should activate about 5 mm before the end of the
movement and it should activate even when the rotating unit is at 5 mm past the end position.
This can be seen in the Signals display.
Figure 55
D-30 Planmeca Proline XC X-ray unit
MECHANICAL ADJUSTMENT OF THE ROTATIONAL PART
Technical Manual