Product

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

Background

The objective of the drum speed calibration test is to find the optimal drum speed for the required intensity.

During the drum speed test, intensity is a fixed value, while the drum speed varies. In contrast, during the intensity test, drum speed is a fixed value, while the intensity value varies.
Note: Test results depend on the plate type (but not plate size or thickness); you must perform the test on each plate type that the customer uses.

Requirements

Tools:

• Densitometer
• Loupe
• Plates

Prerequisites:

• Focus value obtained in the Focus calibration test
• Elevation value obtained in the Elevation adjustment procedure
• Laser uniformity value obtained in the Laser uniformity calibration test
• Resolution value obtained in the Resolution calibration test
• Delay value obtained in the Delay calibration test
• Intensity value obtained in the Intensity calibration test

Procedure

This procedure includes the following sections:

• Calibrating drum speed
• Selecting the optimal drum speed

Calibrating drum speed

1. Load a plate.
2. From the Kodak Xpo^™ palette, select Tools > Calibration. The Plate Sensitivity parameters of the loaded plate are automatically transferred from the Lotem/Magnus 400 Controller software.
   
   
   
   
3. In the Calibrate dialog box, perform the following steps:
   1. In the Calibration Type list, select DrumSpeed.
   2. In the Intensity field, the last-saved intensity test value appears. Type a new intensity value according to the plate that you are using for the test—for example, 280 for positive (blue) plates, and a value between 160 to 170 for negative (green) plates.
      
   3. In the Drum Speed field, the last-saved drum speed test value appears. Do not change this value until the optimal drum speed has been determined.
      Note: Accelerated drum speeds require higher intensities than reduced/low drum speeds.
   4. Clear the Calculate All Points When Saving check box. This ensures that the working conditions are updated only for the resolution that is currently defined.
      
   5. In the Test Drum Speed Values [rpm] area, in the From and To fields, type the test range for the drum speed motor values. For best results, enter a range that is ±50 motor steps of the currently displayed motor value—for example, between 900 to 1300.
   6. In the Number of Steps list, select the number of exposures to perform for the selected test focus value range. For best results, enter a minimum of 10 or 11 steps.
      When you type a step value, the Lotem/Magnus 400 Controller software automatically calculates and displays the size of each step interval in the Size field, using the following formula:
      Step size = (To–From)/(Number of steps –1)
      Note: The interval value provides a quick reference for the platesetter operator, and cannot be changed.
   7. In the Resoluton list, select the resolution used by the customer.
   8. In the Test File list, select the TIF file that you want to use for the drum speed test.
      Note: Test files are predefined; the ones that appear in the list are according to the selected resolution and plate type.
   9. In the Current Plate list, select the plate that you are using for the test.
   10. In the Image Offset fields, type a value in millimeters for the horizontal offset (around the drum), and the vertical offset (along the drum).
       Note: The (0,0) offset coordinate is located at the upper-left corner of the plate.
       If you use the same plate for multiple tests, enter the appropriate offset values for each test.
   11. In the Plate Policy section, select or clear the Load and Unload check boxes that apply to focus test:
       • Load: Automatically loads a new plate before the test begins. To perform multiple calibration tests on the same plate, before you start the next test, clear this check box to reuse the plate.
       • Unload: Automatically unloads the plate after the test. To perform multiple calibration tests on the same plate, before you start the next test, clear this check box.
4. Click Test to start the drum speed test.
   Lotem/Magnus 400 Controller performs a series of exposures on the plate, after which you need to process the plate and examine the results.

Selecting the optimal drum speed

1. Visually examine the results, and select the target strip for which the 50% dot area measures 50%.
   
   
   
   

   Measure the density in the solid area. A good density reading should be 0.07 dmin or less.

2. In the Drum Speed field, type the optimal drum speed value returned, and click Save.
3. Verify that the new value was saved in the database.
   1. In the Lotem/Magnus 400 Controller software, go to DataBase, and double-click Res Int.
      
      
      
      
   2. In the Resolution/Intensity Tables dialog box, locate the row with the resolution and laser intensity that was used for the test and, in the Drum Speed column, the newly-saved value should appear.
   3. Click Close.
4. If required, repeat the test for other resolutions used by the customer.

Technical contact

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

Date submitted

11 Jun 2008