Error Message:

CARRIAGE: unexpectedly arrived at HOME position

Applies to:

• All

Service Information:

The carriage HOME switch was tripped unexpectedly. The HOME switch is used as the reference point for all carriage movement except when imaging (the plate edge is used then). Carriage movement is made "open loop" by counting motor rotations, there is no direct positional feedback. Therefore if the carriage stalls, positional accuracy is lost and the carriage may run unexpectedly into its limits of travel, the HOME or AWAY switch. Note that if the carriage stalls while imaging, only the current plate will be ruined. The lack of positional accuracy will be corrected when the edge of the next plate is searched, since the carriage will be re-initialized if searching is unsuccessful after the first two attempts.

The firmware is designed to recover automatically from this error. However, the cause of this error must be investigated because it may indicate a mechanical problem.

If this error occured when the carriage was moving home at the end of an image, it is likely that the carriage stalled while imaging. The imaged plate should be inspected for artifacts. Look for dark bands where the carriage stalled, or places where the image is "compressed". Another image can be attempted, preferably one with many asynchronous retraces, and the leadscrew watched. Watch particularily where the carriage starts and stops while it waits for the RIP. If any stalling is detected, check the leadscrew for binding and the leadscrew hanger for alignment. Also check the following NVS parameters for correct settings: "set carriage pgain" "set carriage mgain" "set carriage again"

These can be temporarily increased from their factory settings if it helps the problem. However this may lead to over-heating the carriage motor so the real cause of the problem should be found. If there is no problem detected with the leadscrew or NVS parameters, the motor or ALE may be at fault. However, check the carriage drive voltages (all carriage drives currently use 80VDC) before swapping these.

If this error occured while the carriage was moving in the "away" direction (like when imaging, etc) or the carriage stopped along way from HOME, suspect that a false HOME signal caused the error. This is likely due to either a foreign object tripping the HOME switch, a faulty HOME/AWAY board, or a faulty or loose HA-BP cable. Check for any slip sheets, loose head wires, cable ties, etc in the vicinity of the HOME/AWAY board. If none are detected, move the carriage back and forth ("carriage away" or "x" and then "carriage home" or "w") to see if the error can be replicated by flexing the cable track.

If the error occured at the beginning of an image (while searching for an edge, positioning, etc), the error may be due to a bug in earlier versions of firmware that allowed incorrect NVS settings of "carriage cph" to cause this error. Check that this parameter is set correctly.

Operator Action:

Click on CANCEL (if it's available) or RESUME, since the Platesetter should recover automatically from this error. Check the plate(s) imaged around the time of this error carefully for artifacts. In any case, record the error message and call Creo Service for help as the machine probably needs servicing.

Cause:

• carriage stalled while moving in the "away" direction (possibly when imaging)
• faulty HOME/AWAY board or cable causing false signals
• foriegn object (such as a cable or slipsheet) tripping HOME switch
• incorrectly set NVS parameters not properly handled by earlier versions of firmware

See Also: