Product

Magnus VLF MCU and CL

Machines affected

Magnus VLF devices with an edge detect camera.

Symptoms

The camera finds the plate edge in the wrong place.

Cause

When the plate edge overlaps slightly over a vacuum groove, reflection from the far side vacuum groove eliminates the plate edge shadow. There is then insufficient contrast between the plate and the drum and the camera finds the edge in the wrong place.

The next photo shows the same plate but at a different drum position. Because the plate is skewed relative to the drum, the plate edge is a small distance away from the vacuum groove. A small shadow is visible on the shoulder of the drum before the drop off into the vacuum groove. The camera finds the correct edge.

Solution

To resolve this problem, do one of the following:

• Use the marker (part number 690-01270 in kit 518-02545A) to blacken the vacuum grooves where the camera edge detect occurs (both sides and the bottom of the vacuum groove must be blackened):
  1. Load a plate (in the same way that the customer loads this plate size).
  2. Open the rear hood.
  3. Blacken the two vacuum grooves closest to the plate edge for the full plate length.
  4. Unload the plate.
  5. Blacken the two vacuum grooves that were previously hidden by the plate edge.
• Change the plate loading position to avoid the vacuum groove - change the the set mhauto FetcherEngineCenterPos parameter. This will reduce the occurence of this problem, but not eliminate it due to variation in where the fetcher drops plates off on the load table.

See also

Drum Vacuum Groove Blackening section in Edge Detect Camera Installation and Calibration

Technical contact(s)

Allan Warnes

Submitted by

Allan Warnes

Date submitted

12 Oct 2006