waster washable pad printing plate
Water washable photopolymer pad printing plate
(No need etching chemical)
complete plate sheet size 500*600mm
Step 1 Exposure
Remove the raw plate from its packaging, cut it to the required size with guillotine shears, place it on the vacuum plate of an exposure unit with the sensitised side upward and remove the protective foil.Depending on the printing (direct or indirect), place the non-reversed or reversed image positive film, matt face down, onto the plate, roll the vacuum foil over film and plate and activate the vacuum. If necessary, use a soft anti-static cloth or a foam squeegee to ease out any trapped air. After quickly checking the vacuum and closing the lid, start the exposure with the set time.
Step 2 Washout
After exposure, the exposed parts on the plate are visible by the change in colour.Depending on the equipment used for washout, the exposed plates are then mounted in the washer or in a flowline washer, attached to the flowline carrier (adhesive or magnetic plate) and washed out for the specified time.
Step 3 Drying
In the case of nyloprint flowline washers (water) with an integrated dryer (DWT), the plate is already dried and
postexposed when it leaves the unit. The cliché is ready for immediate use.When using a washer from the CW combination or a unit with a similar design, once the plate has been exposed,it must first be rinsed to remove any remaining washout solution (alcohol/water mix or water). The plate is then placed in the dryer and dried for the specified time at the specified temperature.It is important, for water-washable plates, that no residual water remains on the plates, as this could damage the relief layer and the relief adhesion when the plates are heated in the dryer.
Step 4 Post exposure on pad printing plate
Once drying is complete, the plate is postexposed, so that all the elements that received little light during
exposure are adequately polymerised.Two minutes is sufficient time for post exposure
Testing the processing times
- Test negative for nyloprint pad printing plates
- Testing the exposure time for nyloprint printing plates
- Evaluating the test exposure
- Testing the optimum washout time
- Drying and postexposure times
To ensure optimum nyloprint® cliché production, it is absolutely essential to know the production parameters
of the particular plate type. This means that the specified exposure time, washout time and temperature, and drying time and temperature must be designed to make the optimum cliché(pad printing plate).
- Test negative
To determine the optimum exposure time, Printing Plates provides a test negative made up of
various critical elements, to be used to establish the exposure times.The test elements shown are combined in a negative film with 8 copies. A step exposure is performed with these 8 copies.
- Washout test
The washout time must be established and checked before determining the exposure time.To do this, a plate exposed with a test negative is washed in a friction washer, such as a CW unit, until the polymer layer has been completely washed away from all the unexposed parts and all that remains is the base metal sheet or base foil with the adhesive layer or coating. The time required for this is recorded. It is important to keep to the washout temperature that Flint recommends.
In the case of a flowline washer, the plates are washed out individually at gradually reduced speeds until they have been washed down to the base metal sheet or base foil. The flow rate required for this is recorded.
Note: Please make sure that the relief is not overwashed by too long a washout time. This shows mainly by underwashing at the fine, isolated relief elements
- Exposure test
During the exposure test, a plate is cut to the size of the test negative and is placed on the vacuum plate of the exposure unit. The protective foil is removed and the test negative placed on top. Then the vacuum is
activated and the vacuum foil is rolled over the film and the plate.Once the plate has been exposed for 1 minute, a small cover plate is placed onto the first copy. The vacuum foil stays on the film and plate. The vacuum is not deactivated.
The upper exposure limit is reached when
- the 400 μm negative dot has a depth of 70 μm
- the relief shoulder angle far exceeds 60°
A further 30-second exposure then follows.The second copy is covered followed by another 30 second exposure and this continues until the last copy has been exposed. The exposure times and intervals between them vary according to the plate type used.The plate is now washed out using the tested washout time and dried. The test elements can now be used to assess the cliché and establish the exposure times and the upper and lower exposure limit.The following rules are applied to determine the limits for exposure:The lower exposure limit – the minimum exposure time -is reached when
- the line grid is neat and straight
- the 200 μm dot is well-based
- the 2 % screen field is perfectly displayed
The Pad Printing Plates data must be followed for drying. When using a flowline washer with a dryer, the time is determined by the flow rate. Only the drying temperature can be adjusted here. This should be 80°C for plates with a steel or aluminium base and 60°C for plates with a foil base.In the case of foil plates, using a higher drying temperature will cause damage due to the shrinkage behaviour of the polyester base.
2 minutes is sufficient time for postexposure.
- Sealed ink cup pad printing system
Dstar sealed ink cup systems employ a sealed container which acts as the ink supply, flood bar and doctor blade all at the same time. A ceramic ring or tungsten ring with a highly polished working edge provides the seal against the printing plate.