HP 450c Service Manual - Page 70

Calibrations The only Calibration that the Printer requires is the Accuracy Calibration which must be performed under certain conditions. 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 Printer can draw a given length of line. The endĆpoint accuracy specification for the Printers is ± 0.38 mm (0.015 in) or ± 0.2% of the specified vector length, whichever is greater, at 23dC (73dF), at 50Ć60% relative humidity on HP matte film. Use the following formula to calculate the Printer's accuracy: Measured length - Desired length x 100 = %Error Desired length What can Affect the EndĆPoint Accuracy ? Various part tolerances inside the Printer 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 Printer to draw an incorrect line length. D The EEROM has been cleared. The accuracy constants are stored in this nonĆvolatile memory component. 5-2 HP DesignJet 430, 450C and 455CA Printers Service Calibrations