Product

Symptoms

Symptoms of registration/image shift problems may include one or more of the following:

• Image shifted on plate in either the mainscan or subscan direction
• Image rotated on plate
• Color separations out-of-register on press
• Plate edges damaged

Cause

External (to the Creo CTP system) causes of registration problems

• Plate handling problems:
  • Plates have burrs from being sheared, rough or dented edges from mishandling, or curled edges from being stored vertically or at an improper angle. These  problems can prevent the plate from seating correctly in the leading edge clamps (LECs).
  • Debris from mishandled or improperly stored plates collects in LEC, preventing plates from seating properly.
  • [Trendsetter NEWS devices with NELA PL-T plate preloader only] Plates carelessly stacked in the P-LT’s plate trolley can have bent edges. The two forward guide posts can put a slight bend on the plate edge that lines up nicely with our registration blocks (in the case of a dual stack) and can introduce image skew.
• Plate quality control problems:
  • Plate is not square
• Problems with customer’s manual punch/bender:
  •  Punch/bender is out of adjustment; hole or bend locations wrong or inconsistent
  • Plate is not perfectly square
• Problems on press:
  • Blanket, clamps, etc.

Internal (to the Creo CTP system) causes of registration problems

• Workflow:
  • Improper Print Console setting for Trendsetter NEWS (Device > Edge Detect set to Only when needed instead of Always)
• Output device:
  • Image shift in mainscan direction (around the drum):
    • Debris on registration blocks and/or in the LEC
    • LEC gap has been set improperly.
    • Picker malfunction damages plate edge, preventing it from seating properly in LEC.
      Example: Plate drops from too great a distance, causing dents at points of contact with registration blocks; thus, true leading edge of plate is lower than expected.
  • Image shift in subscan direction (along the drum):
    • Ball nut is not tightly attached to leadscrew
    • Problem with carriage drive system
    • Edge detection problem:
      • Plate edge has burr
      • Pre-punched plate has oddly-shaped leading edge, making it difficult for focus laser to detect true edge
      • Edge detect strip contaminated with debris
      • Focus laser problem
    • [Trendsetter NEWS 200 dual-head only] Subscan image shift on one head:
      • NVS geometric correction parameters mshift, headspacing, or sshift not set up correctly
      • Control cable to the thermal imaging head that has the shift is faulty.
      • Dual head interface board is faulty.
      • Cables from the dual head interface board are faulty.
  • Image skewed on plate:
    • LEC gap has been set improperly.
    • Debris on registration blocks and/or in the LEC
    • NVS loadpos parameter not optimized for the output device.
    • Plate roller problems (bearing damage or too much pressure against drum)
    • Picker setup problems cause plate to be skewed on drum:
      • Vacuum cups or hoses protruding from picker head, interfering with plates
      • Picker plate drop distance not set properly
      • Picker vacuum cups in poor condition
      • Picker NVS parameters set sub-optimally
      • Picker down sensor operating incorrectly (letting go of the plate while still in motion)
    • [NEWS Dual-Bay devices with NELA preloader only] NELA PL-T is not placing plates properly onto the NEWS device’s plate ledge.

Solution

1. Eliminate external (to the Creo CTP system) problems
   Check to see whether the source of the registration problems is external to the Creo plate imaging system.
   1. Inspect the punch/bender to ensure that it is not the cause of the registration problems. If necessary, instruct the customer to clean, repair, or readjust the punch/bender.
   2. Check the plates for squareness. Either check the plates with a square, or put them back to back and butt the short ends against a flat surface and examine the other ends. Any plate overhang at the other end indicates possible out-of-square condition.
   3. Consult with the customer to ensure that the registration problems are not caused by a problem with the press.
   4. Examine how the plates are being stored and handled.

      Ensure that plates being used are clean and do not have burrs or rough edges.
      If plates are removed from their box and stored on their edges, ensure they are stored at an angle—less than 90 degrees, but not less than 75 degrees.

      

   5. [Trendsetter NEWS devices with NELA PL-T plate preloader only] Ensure that plates in the P-LT’s plate trolley are stacked carefully and do not have bent edges where they make contact with the two forward guide posts. These can put a slight bend on the plate edge that lines up with our registration blocks (in the case of a dual stack) and introduces image skew.
2. Eliminate Print Console/workflow-related problems
   Check the Print Console/workflow settings:
   1. Check to ensure that the Print Console Edge Detect setting is set to Always (not When Required). On NEWS 200 and NEWS 150 devices, this is an option on the Device menu. On other NEWS devices it is set in the registry. See Print Console Sometimes Causing Subscan Shifts on Trendsetter NEWS Devices for more information.
   2. Check all other relevant Print Console settings and ensure they match what the customer expects.
   3. Check the customer’s files and/or templates to ensure that they are not the cause of the image shift problem.
3. Once you have eliminated external and workflow-related causes of registration problems, you can concentrate on the output device.
   • Is the registration problem a shift in mainscan direction (around the drum)? If so, proceed to step 4.
   • Is the registration problem a shift in subscan direction (along the drum)? If so, proceed to step 5.
   • Is the registration problem a skewing (distortion or rotation) of the image on the plate? If so, proceed to step 6.
4. Eliminate CTP device-related problems causing image shift in mainscan direction
   Look for problems that could cause of an image shift in the mainscan direction (around the drum).
   1. Check to verify that the LEC gap has been set properly (see Adjusting the LEC Gap/Actuator Timing on the 3244 Engine).
   2. Verify loadpos (MCE) or lepos (MPE) parameter and ensure that it is optimized for the output device (again, see Adjusting the LEC Gap/Actuator Timing on the 3244 Engine).
   3. Is there debris on registration blocks and/or in the LEC? If so, clean the contaminated parts, and then see if you can find the source of the debris and prevent it from accumulating again.
   4. Inspect all LEC components (clamps, pivot blocks, cylinders, actuator) and check for excessive deflection in the center of each clamp. Replace and adjust as necessary.
   5. Is there a picker malfunction that results in damage to the plate’s leading edge, preventing it from seating properly in LEC?
      For example, does the plate drop from too great a distance, denting the leading edge at the points of contact with registration blocks?
      If so, adjust the picker so that the plate does not drop from too great a height. See Leading edge of plate is dented when released onto the registration pins.
   6. GC parameters:
      • Run a plot 100 on the home side plate, and make any necessary adjustments to the mainscan shift to get the registration mark to the 1 x 1-in. location. For more information (and for information on adjusting the subscan shift and rotation parameters), see step 6a, below.
      • [Trendsetter NEWS 200 dual-head only] If mainscan image shift occurs on one head, check to see if NVS gc mshift parameter is set correctly (see Adjusting Stitching/Geometric Correction Parameters on a TMCE or GMCE Trendsetter NEWS 200 Device).
5. Eliminate CTP device-related problems causing image shift in subscan direction
   Look for problems that could cause an image shift in the subscan direction (along the drum).
   1. Is the ball nut assembly tightly connected to the flex tube on the carriage? If not, use a hex key to back off the setscrew on top of the ball nut assembly until it no longer makes contact with the carriage’s flex tube. Then, tighten the setscrew ¼ turn past the point that it just makes contact with the flex tube. This is approximately 4.6 N·m (40 lbf·in) of torque.

      

   2. Are there burrs or roughness at the edges of the plate? If so, ensure that the customer is handling and storing the plates correctly (see step 1d, above). If the plates themselves are substandard, advise the customer to discuss this issue with the plate vendor.
   3. Is the customer using pre-punched plates that have unusually-shaped leading edges, which make it difficult for focus laser to detect the plate’s true edge? (See example, below.)

      

      If so, and the output device is a Trendsetter NEWS 200 (with thermal 2 heads), adjust the edge sr parameter so that the focus laser can detect the true plate edge. See Calculating the Edge Surface Reflectivity for more information. If the NEWS device uses a thermal 1.x head,

   4. Is the edge detect strip contaminated with debris? If so, clean or replace it.
   5. Is there a problem with the focus laser? See:
      TH1.7x: Setting Focus Parameters in the field (TH1.X)
      TH2: Troubleshooting focus errors
   6. GC parameters:
      • Run a plot 100 on the home side plate, and make any necessary adjustments to the subscan shift to get the registration mark to the 1 x 1-in. location. For more information (and for information on adjusting the mainscan shift and rotation parameters), see step 6a, below.
      • [Trendsetter NEWS 200 dual-head only] If the image shift occurs on one head, check to see if any of the following components are faulty:
        • NVS gc mshift, headspacing, or sshift parameters incorrect (to correct, see Adjusting Stitching/Geometric Correction Parameters on a TMCE or GMCE Trendsetter NEWS 200 Device).
        • Control cable to the thermal imaging head that has the shift
        • Dual head interface board
        • Cables from the dual head interface board
6. Eliminate CTP device-related problems causing image skew
   Look for problems that could cause the image to be skewed (distorted or rotated) on the plate:
   1. GC parameters:
      • Run a plot 100 on the home-side plate, and make any necessary adjustments to the mainscan and subscan shifts to get the registration mark to the 1 x 1-inch location.
      • Check for rotation and correct if necessary.
      • Using the above adjustments as the reference, image a plot 100 on the home-side plate, then reload it on the away side and image a plot 114.
      • Make the necessary adjustments to align the mainscan, subscan and rotation parameters to match the home side.
      • If there are multiple machines, use this first machine as a reference, and align subsequent machine home and away plate positions gc to match.

      For more information on setting geometric correction parameters, see:

      • Geometric Correction: Aligning Multiple MPE Machines in the Field
      • MCE Trendsetter Geometric Correction Parameters
   2. Check to verify that the LEC gap has been set properly (see Adjusting the LEC Gap/Actuator Timing on the 3244 Engine).
   3. Verify loadpos (MCE) or lepos (MPE) parameter and ensure that it is optimized for the output device (again, see Adjusting the LEC Gap/Actuator Timing on the 3244 Engine).
   4. Is there debris on registration blocks and/or in the LEC? If so, clean the contaminated parts, and then see if you can find the source of the debris and prevent it from accumulating again.
   5. Inspect all LEC components (clamps, pivot blocks, cylinders, actuator) and check for excessive deflection in the center of each clamp. Replace and adjust as necessary.
   6. Check the plate roller for damaged bearings or too much pressure against the drum. It must spin freely.
   7. Picker setup:
      • Ensure that vacuum cups or hoses are not protruding from picker head, interfering with plates.
      • Ensure that picker plate drop distance is set properly (see Leading edge of plate is dented when released onto the registration pins).
      • Check picker vacuum cups to verify that they are in good condition
      • Check speed of picker actuators to ensure that they are adjusted correctly (see Measuring engine, picker, and table actuator times and adjusting actuators, Adjusting the Picker 3 Up/Down Actuator Regulators , and Adjusting the Picker 3 In/Out Actuator Regulators). In particular, check picker down speed to see whether it is excessively slow, causing the sensor timing to drop the plate while it is still in motion.
      • Check mhauto pickerdroppause (MCE) or pdp (MPE) parameter, and increase by 0.250 seconds if necessary.
   8. [NEWS Dual-Bay devices with NELA preloader only] Check that the NELA PL-T is placing plates properly onto the NEWS device’s plate ledge. The PL-T plate drop height must be set properly (5 mm to 10 mm is good) and the NEWS device’s separator arms must not be sticking out too far. If the plate drop height is too high, the plate can get badly skewed in the bay, and then fail to drop squarely into the LECs. Also, preloader machines that return an unused plate back into the plate stack in the trolley can damage the lead edge and introduce image skew.

      For more information on the Trendsetter NEWS Dual-Bay option, see Dual Bay option information.

See also

• Edge detect, subscan shift (1.7x heads)
• Troubleshooting thermal 2 focus errors
• Image shift away from the LEC
• Image corruption at the beginning of a plot, horizontal image shift, or a missing image
• Leading edge of plate is dented when released onto the registration pins (V3 Picker)

Technical contact

Jack Miro

Submitted by

Date submitted

01 Jun 2005