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FAQ

Frequently Asked Questions

Registry Issues:
Webpath
Line Shaft
Gear Boxes
Infeed Pacing
Waste Wind-up
Drying

Print Quality Issues:
Main Drive Motor
Line Shaft
Gear Boxes
Infeed Pacing Roll
Print Cylinders

Web turnbar troubleshooting

REGISTRY ISSUES


WEBPATH

  1. Make sure all Idler Rolls are clean and rotating properly.
  2. Make sure that the web has not, inadvertently, been routed over a dead bar.
  3. If the press is equipped with a turn bar make sure there is adequate air supplied to the device and the air
    holes are not plugged. (60 PSI at 4 SCFM)
LINESHAFT
  1. Visually inspect the line shaft segments and couplings for obvious issues.
  2. Verify that the couplings are aligned properly. Each coupling should slide easily and completely onto the
    line shaft, if this is not the case loosen the coupling bolts and slide the complete coupling onto the line
    shaft and then retighten the coupling bolts.
  3. Once the coupling is aligned and tight slide the coupling into place, make sure the keys are in place and
    tighten the hub on the line shaft only. Do the same at the other end of the line shaft segment. At this
    point the line shaft should slide easily on the gear box input shafts, once this task is satisfied then center
    the line shaft segment and tighten the set screws. Complete these steps for all line shaft segments.
  4. If adjustments are made to the press level then the line shaft couplings should be rechecked.

GEAR BOXES

  1. Observe the oil level and the cleanliness of the gear box oil.
  2. Make sure the gear box mount cap screws are tight and the locating pins are in place.
  3. Make sure all the cap screws affixing the flanges to the gear boxes are tightened properly. These flanges
    are load bearings that secure the input and output shafts. These cap screws tend to work loose initially
    with the heating and cooling of the gear boxes.

INFEED PACING

  1. Check the disc on the infeed pacing roll tension brake for excessive Runnout. This runnout should not
    exceed 0.002".

WASTE WIND-UP

  1. Make sure the pulley that is driven from the line shaft and drives the waste wind-up is aligned properly.
    On occasion this pulley has migrated toward the gear box. IF this pulley is rubbing against the gear box
    flange bolts it will create press vibrations, registry issues, and print quality issues. This would not be an
    issue on servo driven systems.

DRYING

  1. Most material ran in our presses have a temperature range they can run in. If this temperature is
    exceeded then there may be registration issues as a result. As the material exits the hot air drying
    tunnel or the UV lamp housing, using an infrared thermometer, measure the material temperature. If
    the temperature exceeds 100 degrees F. or 38 degrees C. you may need to consider lowering the drying
    temperature.
  2. If the UV lamps are the main source for drying on a press check to make sure the life of the UV lamp has
    not been exceeded. If their life has been exceeded they will not go out....instead they will produce more
    IR then UV which will over heat the material and not totally cure the ink. If the UV system is set to ramp
    in intensity with the speeds of the press, in most instances, 100% power should not be attained until the
    press is at 60% speed. If the ink is not thoroughly curing the normal tendency would be to increase the
    power, however if the maximum temp range of the material is exceeded there will be registration issues.

PRINT QUALITY ISSUES

MAIN DRIVE MOTOR

  1. Make sure pulleys are aligned and the drive belt is tracking properly.
  2. Make sure the drive belt is tensioned properly.
  3. Pulley Runnout should not exceed 0.002"

LINE SHAFT

  1. Visually inspect the line shaft segments and couplings for obvious issues.
  2. Verify that the couplings are aligned properly. Each coupling should slide easily and completely onto the
    line shaft, if this is not the case loosen the coupling bolts and slide the complete coupling onto the line
    shaft and then retighten the coupling bolts.
  3. Once the coupling is aligned and tight slide the coupling into place, make sure the keys are in place and
    tighten the hub on the line shaft only. Do the same at the other end of the line shaft segment. At this
    point the line shaft should slide easily on the gear box input shafts, once this task is satisfied then center
    the line shaft segment and tighten the set screws. Complete these steps for all line shaft segments.
  4. If adjustments are made to the press level then the line shaft couplings should be rechecked.

GEAR BOXES

  1. Observe the oil level and the cleanliness of the gear box oil.
  2. Make sure the gear box mount cap screws are tight and the locating pins are in place.
  3. Make sure all the cap screws affixing the flanges to the gear boxes are tightened properly. These flanges
    are load bearings that secure the input and output shafts. These cap screws tend to work loose initially
    with the heating and cooling of the gear boxes.

INFEED PACING ROLL

  1. Check the disc on the infeed pacing roll tension brake for excessive Runnout. This runnout should not
    exceed 0.002".

PRINT CYLINDERS

  1. The print cylinders should be checked for Runnout on their bearings. This Runnout should not exceed
    0.0005". The bearing quality is critical for fine process printing when ordering plate cylinders be sure to
    request quality bearings.
  2. The print cylinder gears can either be helical or spur gears and should not be less than a class 10 in
    quality and precision. We would prefer that a class 12 gear be used.
  3. The printing plate durometer and the type of mounting tape used to mount the plates play a critical role
    in fine process printing. The customer should work with their vendors to find the best plate components
    for their products.

WEB TURNBAR TROUBLESHOOTING

Have You Ever Run Into A Tension Issue When Using A Turn Bar?

  • The most common reason for this is the difference of neutral axis or pacing radius shifts of the material
    depending on which side is against the pacing rolls. This is due to the material being constructed of
    materials that have different modulus of elasticity (stiffness) or not being homogeneous (consistent
    throughout its thickness).
  • Example: Pressure sensitive material has a paper side and liner side. If you were to print this material
    with the paper side up and then print the same material with the liner side up, measure the length
    of image, you would see a difference in length since the material paces differently in each of these
    conditions.

One of the most common observations is an application where the web slacks after the turnbar. The first
action is raising the overall tension in the press. What this does is stretch/strain the material more so that the
strain removal on the exit side caused by the lower pacing rate is not enough to reduce the web tension to an
unacceptable level.

The most effective way to analyze the problem is fairly simple and only requires a standard tape measure. This
method will identify the magnitude of the problem so that the appropriate action can be taken whether it is
impression roll stepping or replacement or just running the proper tension.

  • Step 1: With the press in standard configuration without the turnbar utilized, run the subject material
    though press with (side A) facing up and print one station. (The usually the backing side up)
  • Step 2: After 2 press lengths which will allow for tension stabilization, remove 20 repeats or maximum
    number of repeats your tape measure will accommodate. Measure the length from first print image to the
    last. Note: You must measure from the same mark.
  • Step 3: Run the subject material though the press so that you can print on the opposite side (side B) of
    the material. Note: Do not run though turn bar, simply run the roll around on unwind.
  • Step 4: Remove 20 repeats of material and measure the same length as preformed on step 2.
  • Step 5: Calculate the pacing ratio by the equation: Side A � Side B

If the ratio is greater than 1 the web should be slacking after the turnbar and the tension should increase.

To find how much an impression roll may need to change we will look at a typical example where the web is
slacking and our throw measurements show that Side A has a throw length of 240.0625 (96 tooth 12" or 1 ft
repeat, 20 repeats). Side B has a throw length of 240" or theoretical.

Side A � Side B X Impression roll diameter = C

C- Impression roll diameter = D

Example 240.0625" �240" x 3.9390" = 3.940"

3.940" - 3.9390" = .001"

Note: a positive number here indicates you need to add a .001" delta to the downstream or Side B or subtract
this from your upstream rolls. On paper stocks with the modulus of elasticity 1.1 x 10^6 to 1.6 x 10^6 , 10"
wide x .007" thick an increase of 20 to 30#s tension on the infeed side will eliminate the slack. However most
LP and non servo 2200s may not have the potential to create this much additional tension and there may be
slippage if the difference required is above 20#s. These situations require the impression rolls to be resized
to accommodate the application. Combinations of tension increases and roll sizes can be made in an effort to
maintain the performance of the press for normal non turnbar applications. A rule of thumb is that for instances
where the delta is above .001, a dedicated roll set before the turnbar may be needed and these rolls changed or
bypassed for standard non turnbar applications.

There are conditions where the throw measurements are essentially equal and you need to reduce the residual
drag and you should check the items below.

Other elements to consider:

  • Material should be rundown the center-line of press.
  • Any holes that are not covered by material should be plugged to prevent too much pressure loss. As any
    rule of thumb any hole within 1" of the web edge should be plugged.
  • The material must be tightly wrapped around turn bars yet there must be sufficient pressure to allow air
    flow to crate an air bearing to keep material separated from the bar so that it slides freely.
  • Turn bars are not well suited for applications such as those utilizing porous materials, clingy plastics,
    foils, and thick board stocks.

 

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