Product

• Kodak^® Lotem^® 400 FH family
• Kodak Magnus^™ 400 LDA family
• Kodak Magnus 400 II LDA family

Background

The objective of the elevation test is to find the correct elevation angle for the optical head.

• Correct elevation: All laser diodes along the V-groove are in focus.
• Incorrect elevation: The laser diodes on one side of the V-groove have a different optimal focus value than the laser diodes on the other side of the V-groove. Incorrect elevation can cause an image shift of about 1 mm around the drum and banding, as well as uneven density within the laser diode swath.

Correct elevation is factory-configured and rarely needs to be adjusted. Plate flyoff or other physical damage to the optic tube might disrupt the elevation angle, requiring it to be readjusted.
Note: The elevation test results do not depend on plate type, size or thickness; perform the test on any plate that the customer uses.

Prerequisites

Focus value obtained in the Focus calibration test

Tools

• Densitometer
• Microscope
• Plates
• Jigs (see table)

Jig Name	Part Number	Image
Elevation jig assy	291B6A743
Elevation jig type II	690-00892A

Procedure

To correct elevation, expose two focus tests on the same plate. The first focus test uses the first five diodes only, while the second test uses the last five diodes only. If the elevation angle is correct, the optimal focus value will be the same for both tests (± 10 microns).

This procedure includes the following sections:

• Before you begin
• Testing elevation
• Adjusting elevation

Before you begin

• Find the best intensity for performing the focus tests. See Focus calibration test.
  Note: For best results:
  • On negative (green) plates, use a lower intensity.
  • On positive (blue) platess, use a higher intensity.

Testing elevation
Note: This test is rarely done. Perform this test only to correct specific instances of banding where the problem was not solved by other calibrations.

First focus test (first five diodes only)

1. In the Magnus 400 Controller software, in the Hardware tree, select Expose System > Laser System, and right-click Laser Group.
2. In the Properties: Laser Group dialog box, locate the Last Laser Active parameter, write down the current value, and then change that value to 4.
   Attention: Do not change the Last Laser parameter.
   Note: For Lotem 400 FH family platesetters, in the Properties: Laser Group dialog box, locate the Last_Expose_Laser_Active parameter, write down the current value, and then change that value to 4.
3. Perform the first focus test series at res 100, but do not unload the plate.
4. Return the Last Laser Active parameter to its original value (that you wrote down in step 2).

Second focus test (last five diodes only)

1. In the Properties: Laser Group dialog box, locate the First Laser Active parameter, and change the parameter value according to the number of diodes on your platesetter:

   On Magnus 400 LDA:

   • For a 31-laser diode platesetter, change the value to 27
   • For a 41-laser diode platesetter, change the value to 37

   On Lotem 400 FH:

   • For a 12-laser diode platesetter, change the value to 7
   • For a 24-laser diode platesetter, change the value to 19
     
     

   Attention: Do not change the First Laser parameter.
   Note: For Lotem 400 FH family platesetters, in the Properties: Laser Group dialog box, locate the First_Expose_Laser_Active parameter, and change the value according to the number of laser diodes on your platesetter.

2. Offset the image around the drum by 250 mm.
3. Using the same range and increments as the first focus series, perform the second focus test series at res 100.
4. Process the plate, and examine the results:
   • If the two best focus values are equal or less than 10 microns apart, the elevation angle is correct.
   • If the two best focus values are more than 10 microns apart, adjust the elevation. See Adjusting elevation.
5. Re-enable all laser diodes on the platesetter.

Adjusting elevation

To adjust the elevation so that optimal focus results are returned, first perform the coarse adjustment, and then if required, perform the fine adjustment.

Using groups of five diodes, perform the elevation test. See Testing elevation.

If adjustment is required, using the best focus values that were returned in the focus test series, calculate the adjustment (C) according to the following formula: (B–A)/2=C

Use the following example for reference purposes only:

If A is greater than B, lower the back of the telescope tube by (C) microns.

If A is less than B, raise the back of the telescope tube by (C) microns.

Coarse adjustment

1. Loosen the three telescope screws (front and rear screws). Make sure to loosen the rear silver screws, and not the small black set screws.
   
      
   
   
2. If you are using the old elevation jig, perform the following steps:
   
   1. On the carriage, remove the focus limit block, and set it aside.
      
      
      
      
   2. On the left side of the carriage (from where you just removed the focus limit block) under the telescope tube, insert the elevation jig. Make sure the telescope and the surface of the jig are evenly aligned and fit snugly together.
      
      
      
      
   3. Tighten the three telescope screws.
      Note: The two screws in the jig limit how far the jig can go under the telescope.
   4. Remove the jig, and reinstall the focus limit block.
   5. Move the focus motor to home position (HP).
   6. Check the lens and drum clearance, and verify that the clearance between the drum and the lens protector is 11.5 mm for Lotem 400 FH family platesetters, and 20 mm for Magnus 400 LDA– and Magnus 400 II LDA family platesetters.
      Note: See Anti-collision procedure.
3. If you are using the new elevation jig II, perform the following steps:
   1. Remove the carriage chain bracket.
      
      
      
      
   2. Insert the elevation jig II under the telescope tube, and verify that the elevation is properly adjusted.
      
      
      
      
4. Perform another elevation test series. If you are not satisfied with the elevation results, perform the fine adjustment procedure.

Fine adjustment

1. Install the elevation jig assembly on the back of the telescope tube.
   
   
   
   
2. Set the dial indicator to a known zero position.
   Note: Do not loosen the front screw again during the procedure. Loosening the front screw a second time might cause the front of the telescope to drop down and upset the adjustment. See step 1 in Coarse adjustment.
3. Adjust the telescope tube position according to the adjustment formula described in Adjusting elevation. After adjusting the elevation, tighten the two rear screws, and remove the elevation jig.
4. Perform another elevation test series to confirm the result.
5. When you are satisfied with the elevation result, re-enable all laser diodes.

Technical contact

Content owner: Mario Amir
See the Escalation page for escalation contacts.

Date submitted

11 Jun 2008