TEST METHOD: FLEXO PRINTING
AMSTERDAM - Multi-purpose printability
To test dry properties of flexo inks a standard print on a substrate is necessary. Such a print must be made under standard printing conditions with a printing device following the flexo principle.
In flexo three types of ink are used: water based, solvent based and UV-drying inks. The water based and solvent based inks have a very low viscosity and dry very quickly. For these inks it is impossible to use an offset system like Global Standard Tester with inking unit. The UV-drying inks have a viscosity like a paste and dry only by exposure to UV-light. In principle this type of ink can be used with a system of Global Standard Tester with inking unit but there can be reasons (printing quality) to use a flexo system.
To print the flexo inks there is an accessory which can be used with the Global Standard Tester 2. The system can be used for all types of flexo inks. The principle of the system is a flexo printing system comparable to practice. The prints, made with this system can be used to test the dry properties like colour, adhesion, light fastness, chemical resistance, and so on.
METHOD OF OPERATION
- It is recommended to execute the test in the standard atmosphere; to most standards it is 23.0 ± 1.0 °C (73.4 ± 1.8 °F) and 50 ± 2% rh.
- For the operation of the Global Standard Tester follow the instructions of the manuals, IGT information leaflet W100 and the displays accurately.
- Handle the samples carefully.
- Condition the substrate, the ink and the equipment during >6 hours in the standard atmosphere.
- Cut the substrate strips (preferable 50 x 200 mm, 3 strips per sample) and mark them with top and/or bottom side, machine and/or cross direction and a code for the type of substrate.
- Select the menu “Flexo” in the display.
- If not present on the Global Standard Tester, mount the round sector. See W100.
- If not present on the sector, mount the photopolymer on it with the double sided foam tape. See W100.
- Clean the anilox roller with velvet with ethanol.
- Place the anilox roller on the top printing disc shaft of the tester.
- Place the impression cylinder on the bottom printing disc shaft.
- For continuous working with water based and solvent based inks:
9. 1 Shake the bottle with flexo ink (water based or solvent based) well.
9.2 Fill the cartridge with ink and mount it on the Global Standard Tester. See W100.
- For some tests only with water and solvent based inks: shake the bottle with flexo ink (water based and solvent based) well and fill a (disposable) pipette.
- For working with UV-inks: fill a (disposable) pipette.
- Degrease the doctor blade with rags with ethanol. Mount the doctor blade in the doctor blade holder. See W100.
- Slide the doctor blade holder with the blade downward and pointing to the right on the two pins of the mounting plate.
- Check the functioning of the flexo system following the instructions in the chapter “Execution”.
- If desired, set the printing speed, anilox force, printing force and the number of revolutions on the desired values. See note 1.
- Attach a test strip on the impression cylinder with a piece of tape at the beginning and at the end of the test strip.
- Select “Make print” in the display.
- Press the side buttons to move the sector into the starting position, the doctor blade holder downward and the printing disc into starting position.
- For continuous working with water or solvent based ink: press one of the buttons 1 – 4 to apply a few drops of ink on the printing disc.
- For some prints only with waterbased ink, solvent based ink or UV drying ink: apply some drops of ink on the printing disc with a (disposable) pipette.
- Press the side buttons to distribute the ink on the engraved anilox disc, to ink the photopolymer and to make a print.
- Press “Enter” to lift the doctor blade from the anilox roller.
- For water based inks only: Directly take off the anilox disc from the shaft and clean it with water and a soft brush or velvet or put it directly into a tray with water and clean it later on.
- For solvent based inks only: Take off the anilox disc from the shaft and clean it with velvet with the solvent of the ink.
- For UV-drying inks only:
11.1 Take off the print directly from the impression cylinder, tape it on a flat strip (e.g. board) and dry it with the UV-dryer.
11.2 Take off the anilox disc from the shaft and clean it with velvet with the cleaning solvent of the ink.
- Clean the photopolymer with rags and ethanol.
- Clean the doctor blade with rags and ethanol.
- For water and solvent based ink only: remove the test strip from the impression cylinder and let it dry according to the type of ink.
- Measure the test result as described in the chapter “Assessment”.
- Repeat the points 1 through 16 for every strip. It is recommended to execute the test at least three times per combination of ink and substrate.
- After having finished the tests clean and store all parts as described in the manual.
- Make an accurate record of the conditions and the results of the test.
MATERIALS / TESTING CONDITIONS
Randstad 22 - 02
1316 BX Almere, The Netherlands
1302 CA Almere, The Netherlands