Error Message:

HEAD: incorrect light level at start of edge detection - check if plate size entered too small

Applies to:

• Green

Service Information:

At the beginning of an edge search, the exposure head measures the amount of light reflected onto the edge detector. Since the edge spot should be shining on the reflective strip (i.e. off the plate), the amount of light reflected should be high. The head measures the reflected light in three different places, each successively farther away from the assumed plate edge. If the reflected light is still not high enough after the third try, this error message is reported.

First measure the plate size and ensure that it matches the plate size specified on the workstation (or in the bay by typing "set state bay <bay #>"). If the plate sizes are different by more than a couple of millimeters (or 1/8"), correct the discrepancy and try the edge search again.

Next ensure that the edge search parameters are all at default settings: "set carriage esearch" "set carriage eatt" "set carriage espot" (Green heads only) "set carriage wsearch"

Ensure that a slip sheet was not stuck to the plate. Clean the reflective strip and try the edge search again.

For GREEN heads:

In the diagnostic monitor, type "plot edge cal" and the green edge finding spot should be positioned very close to the edge of the plate (note that the drum's reflective strip is NOT held in position under the spot). A strong laser spot should be visible if there is no problem with the head, i.e. the shutter is not opening, the laser is failing, etc. If the laser spot is not within 2 millimeters of the plate edge, the "carriage cph" parameter must be adjusted by the distance between them. It should be increased if the spot is too far off the plate, decreased if it is on the plate. Check the new setting of cph by typing "plot edge cal" again and then save it.

Once satisfied with the cph value, move the drum's reflective strip into position with "drum edge". The green spot should be in the middle of the lower half of the strip. If not, the "drum epos" parameter should be adjusted by 10 counts down if the spot is too low, and 10 counts up if the spot is too high. Check the new setting of epos by typing "drum edge" again and then save it.

If the edge search is still unsuccessful, the exposure head may be faulty.

Operator Action:

Double check that the actual plate size matches the plate size stored on the workstation. For Platesetters, this information is retrieved by clicking on a cassette bay button. If they match, record error message and contact Creo service.

Cause:

• Actual plate size different than plate size specified in bay or on workstation
• Edge search distance parameters too small
• Slip sheet stuck to plate
• Edge strip dirty
• Plate not loaded correctly on drum
• "set carriage cph" parameter needs adjusting
• Exposure head faulty

See Also:

• NVS: carriage esearch
• NVS: carriage eatt
• NVS: carriage espot
• NVS: carriage wsearch
• NVS: carriage cph
• NVS: drum epos
• Command: plot edge