Product

• Kodak^® ThermoFlex^® Mid
• ThermoFlex Narrow

Background

The objective of the Focus calibration test is to find the focus stepper motor value that enables the focus of the beams to coincide with the plate surface. The procedure includes first finding the coarse focus, and then the fine focus.

Requirements

• Densitometer
• Microscope
• Flexo plate(s)
• Offset plate(s) if the configuration includes offset option
• Focus jig
• Micron indicator
• Verify the preload and perform mechanical focus assembly adjustment
• Regular media thicknesses—Preload and mechanical focus adjustment
• Wide media thicknesses—Wide Focus Motor Replacement

Procedure

Before performing the focus test:

1. Check the focus stopper location. There should be the minimum amount of space between the optic tube and the optic tube bracket, as shown following.
   
   To move the focus stopper to the proper location:
   1. Move the carriage to any location along the drum.
   2. Move the focus motor to the maximum location.
      • For wide focus range, move the focus motor to 5000.
      • For earlier versions, move the focus motor to 2800.
   3. On the optic tube stopper, loosen the two hex screws and then move the stopper until the optic tube bracket touches the optic tube.
   4. Lock the stopper in place by tightening the two hex screws.
2. Important: Move the nozzle as far away from the drum as possible.
   Failure to move the nozzle as far away from the drum as possible before setting the forcus for each media thickness may cause irrepairable damage to the platesetter.

Note: The focus stepper motor value is dependent on the plate type, so repeat this test for each plate type and thickness that the customer uses.

1. Load a plate.
2. In TIFF FE, from the Launch Pad, select Utilities > Calibrate.
   
   
3. In the Calibration Type box, select Focus.
   
   
4. In the Current Plate list, select the Plate that you are using.
   
5. Select the appropriate Resolution.
   
   
6. Select the relevant test file according to the type of plate:
   • Flexo—select machineCalibTest.lw
   • Offset—select CalibTest100AM.K.TIF
   • Offset Staccato—select CalibTest100FM.K.TIF

7. Define the Image offset values:
   • Horizontal offset—The value around the drum in mm
   • Vertical offset—The value along the drum in mm
   If you use the same plate for several tests, define different offset values for each test.
   Note: The (0,0) offset coordinate is located at the upper-left corner of the plate.

Note: The parameters in steps 8-11 are different for the coarse test and the fine test. Perform the first test using the coarse parameter values, and the second test using the best results from the coarse test, and the fine parameter values listed in steps 8-11.

8. Select the Intensity for Test parameter value according to the following table.

Diode strength and plate type	660 mV diode/ flexo plate	1 W diode/ flexo plate	1 W diode/ offset plate
Intensity Narrow	coarse: 600 mV fine: 300 mV	coarse: 900 mV fine: 500 mV	coarse: 140 mV fine: 120 mV
Intensity Mid	coarse: 600 mV fine: 300 mV	coarse: 900 mV fine: 500 mV	coarse: 170 mV fine: 120 mV

9. Set the Test Focus Values [Steps] From and To range:
• Coarse test: Find the target focus from the following table and enter a range of ±100.

Plate thickness (mm)	Target focus value in microns for media thickness range
	0.1 to 2.54 mm	0.76 to 3.2 mm	1.14 to 3.94 mm	Wide range
0.17	2540	not supported	not supported	4950
0.7	1940	2640	not supported	4420
1.14	1500	2200	2940	3980
1.7	940	1640	2380	3420
2.54	100	800	1540	2580
3.2	not supported	140	880	1920
3.94	not supported	not supported	140	1180
5	not relevant	not relevant	not relevant	120

Note: The focus values in the table are in microns.
Focus value should be within a 30-micron deviation from the table value.

If the plate thickness you need does not appear in the table:

Non-wide range: Click focus value calculation table to automatically calculate the focus value for any plate thickness.
Wide range: Find the target focus for one of the listed thickness and calculate the target focus for other thicknesses according to the following formula:
Unknown focus value = known focus value - [(unknown plate thickness - known plate thickness) x 1000]

For example: Using a 0.17 mm thick plate's required focus of 4950, find the focus value for a 0.3 mm plate thickness:
X = 4950 - [(0.3-0.17) x 1000]
X = 4950 - [0.13 x 1000]
X = 4950 - 130
X = 4820

• Fine test: For the fine-tuning test, the range is the best step that you find in the coarse test ±50).
  

10. Set the Number of Steps: Coarse = 5, Fine = 11.
11. In the database, select the Drum Speed according to the following table.
    

    Diode strength and plate type	660 mV diode/ flexo plate	1 W diode/ flexo plate	1 W diode/ offset plate
    Narrow	170 rpm	220 rpm	500 rpm
    Mid	120 rpm	170 rpm	500 rpm

    
    
12. Move the carriage so that the lens is in front of the loaded plate.
13. Move the focus motor to the maximum motor step at which you plan to expose and check that the nozzle does not collide with the loaded plate.
14. Before exposing the plate, measure the plate thickness and update the media definition.
    Important: Alert the customer to always measure the media thickness before exposing, and to update the thickness in the media definition dialog box, if required.
15. Close any open doors and verify that the platesetter is in Ready mode.
16. Click Test to initiate the focus test. The application performs several exposures.
    Note: After you perform the coarse test, you may need to calibrate resolution and delay before performing the fine test.

Select the best focus value:

1. Remove the black layer in the corners of the measured plate so that you can see the clean plate.
   • Regular plates—use masking tape to remove the black layer
   • BASF Nyloprint plates—use water to remove the black layer
   • PCI Film—use a blade to scrape the mask off
2. Calibrate the densitometer so that the density reading of the clean corner (without the masking tape) is 0.
3. Measure the density in the solid area.
4. Select the clearest strip with the lowest density and use its value as your focus value.
5. If the target focus value is very different than expected, proceed as follows:
   1. Move the carriage to middle position.
   2. Move the focus motor to the optimal focus value that you found for that plate.
   3. Record the position of the large and small hands on the dial.
   4. Move the focus motor to the required position according to the table.
   5. Remove the stopper bracket.
   6. Loosen the two screws that secure the optic tube.
   7. Manually move the optic tube to the position that you recorded on the dial.
   8. Reinstall the stopper bracket and adjust its position.
   9. Tighten the two screws that secure the optic tube.
   10. Expose the plate and check the results.
6. In ThermoFlex Controller, in Media definition, type the focus value. This value is the optimal focus for the tested plate thickness.
7. If required, repeat the test for other plate types and thicknesses.
   Note: The thickness of individual plates can be different between batches according to vendor specification. You must use the correct focus value for each plate definition. The device does not compensate by calculating the correct value for other plate thicknesses.
8. Adjust the nozzle position.

Technical contact(s)

Content owner: Viki Arviv
See the Escalation page for escalation contacts.

Date submitted

22 Jun 2004