WEB PRINTING
This section applies to the installation of the
Careful consideration should be given to selecting an appropriate area in the production line for installation of the coder. Since the coders are friction driven by the moving web of material, a primary factor is to select an area where the position of the web material is accurately controlled and preferably supported by an idler or guide roller on the underneath side as shown in Figure 32.
The only real consideration with respect to the attitude of the coder frame is that the 4 oz. res- ervoir ink cartridge (when installed) should be kept as near to a vertical position as possible with the plastic ball pointing down. This will en- sure proper ink feed from the 4 oz. cartridge to the ink roll. When disposable Type MT Ink Rolls are used on the coder, 4 oz. Reservoir Ink Car- tridges are not used and therefore the coder can be mounted in any convenient attitude. When installing the coder, the print drum axle of the coder should be in parallel alignment with the idler roll and the print drum should contact the web at the point where the web is tangent to the idler roll and solidly supported. It is also impor- tant that the distance “C” between idler roller “A” and idler roller “B” should be adequate so that at the maximum web speed, the ink will dry before the printed marks contact idler roller “B”. If dis- tance “C” is not adequate for the drying time of the ink used, a ghost image transfer of the marks may be overprinted on the web by idler roller “B”.
4 OZ RESERVOIR |
INK CARTRIDGE |
MOUNTING |
COLUMN |
PRINT DRUM |
15o |
IDLER ROLL B |
C |
IDLER ROLL A |
FIGURE 32
To eliminate this problem, if idler roller positions are not adjustable, a slight undercut in the face of idler roller “B” where the printed marks pass under the roll, will prevent the wet marks from touching the face of the idler. Generally the undercut in the idler roller needs to be only .020"
UNDERCUT |
.020” |
IDLER ROLL |
WET IMPRINT |
FIGURE 33
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