HP 250C - Manual (Page 116)

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7Ć8 Calibrations and Adjustments C4699Ć90000
Accuracy Calibration
Purpose
The accuracy calibration (XĆaxis calibration) procedure is used to correct the endĆpoint
accuracy of the media axis. The carriage axis does not require calibration and is used to
calibrate the media axis. The accuracy calibration also includes calibration of the optical line
sensor on the carriage.
The accuracy calibration is also used to correct the error of the XĆaxis movement to avoid
banding.
Perform the accuracy calibration whenever the:
D EEROM is erased
D Electronics module is replaced
D Drive roller is removed or replaced
D Media (XĆaxis) motor is removed or replaced
D DriveĆroller gear is removed or replaced
D Cartridge carriage is replaced
D Mark encoder is removed or replaced
D Optical sensor is removed or replaced
What is the EndĆPoint Accuracy Specification ?
The endĆpoint accuracy specifies how accurately a plotter can draw a given length of line.
The endĆpoint accuracy specification for the plotters is ± 0.38 mm (0.015 in) or ± 0.2% of the
specified vector length, whichever is greater, at 23 d C (73 d F), at 50Ć60% relative humidity on
HP special polyester film. Use the following formula to calculate the plotter's accuracy:
Measured length – Desired length
Desired length
x 100 = %Error
What can Affect the EndĆPoint Accuracy ?
Various part tolerances inside the plotter affect the accuracy (in particular the drive roller).
Other outside influences include:
D Media thickness. Thicker media creates longer lines.
D Media expansion. As the media grows, so do the lines.
D The application software may be instructing the plotter to draw an incorrect line length.
D The EEROM has been cleared. The accuracy constants are stored in this nonĆvolatile
memory component.