Rotary-Screen Printing Machine
Rotary-screen printing machine used for both carpet printing and textile printing but the main difference of the rotary screen printing machine depend on between the carpet and other textile printing according to the type of squeegee used. All carpet squeegees are considerably larger and wider opening end rings are used. The standard print width is usually 4 m, so considerable storages space is needed for many screens and design used by a typical carpet factory. The screens are made by Galvono Nickel of a fairly heavy gauge (0.3-0.5 mm thick) with a much coarser mesh(20-30).Lacquer screens are not used for carpet printing. Standerd rotary screens give a repeat pattern of 1 m but a larger screen can give repeat sizes up to 3 m printing of oriental carpet designs. Read about Offset Printing Machine
Advantage of the Rotary- Screen Printing Machine:
- More productive than older flat screen machine.
- Print speed is 15-20 m/min.
- The machine occupies much less space.
- Labor costs are lower.
- With actuating mechanism it is possible to print repeat pattern 2-3 m for bordered oriental square designs.
Disadvantages of the Rotary- Screen Printing Machine:
- Uses higher cost of galvano nickel screens.
- Screen changing time longer.
- There is also a tendency for carpet to spoil during stoppages(Cause: the paste tends to flow fairly easily through the coarser mesh screen when it is stationary)
- The use of thickeners with short flow properties can help prevent leakage from the screens when stopped.
Minimizing dye paste use in rotary screen printers
A water-saving system on the washing machine for the barrels or screens not only reduces water consumption, but also results in a more concentrated waste load. In case the washing process takes place in three stages, in the first stage residual water from the second and third stages is used that was temporarily stored in a recirculation reservoir. The strongly contaminated wastewater resulting from the first stage is discharged to the water treatment system and then to the sewer. In the second stage of the washing process, both the water intake and the water outlet are connected to the recirculation reservoir. Finally, in the third stage of the wash cycle, the barrels or screens are washed with clean water. The residual water resulting from this last stage is then fed into the recirculation reservoir, which is thus replenished. In the recirculation reservoir and on the intake side of the water pumps, filters make sure that pollutants of all sizes are removed from the water, thus preventing blockage of the spraying system.
By implementing a water-saving system, the water consumption of a specific machine can be reduced by 80%.
A water-saving system is applicable for the cleaning of screens, squeegees and barrels.
A water-saving system can be installed on existing machines or a new system can be purchased with an integrated water-saving device. The additional costs compared to washing machines without water-saving is approximately EUR 10 000 for screen washers and EUR 3 000 for barrel washers.
In rotary screen printing, for every colour there is a screen, a supply system for the colour and a paint kitchen inventory. After every printed batch the system has to be cleaned thoroughly. As a result, considerable amounts of dye paste end up in the wastewater, because the volume of the machines is significant and a substantial quantity of dye paste stays behind in the system. Minimisation of the system volume on rotary screen printing machines has become a reality with the introduction of a new pump and squeegee system.
Usually, the system volume of rotary screen printing machines varies from a few kilograms to maximum 10 kilograms, with an average of 5 kilograms. With the new pump- and squeegee system it has become possible to reduce the system volume per recipe by approximately 60% in comparison with a conventional squeegee system. This means a significant reduction of the use of dye paste. Furthermore the system allows to return a large part of the excess paste into the system. This way 1,5 kilograms of dye paste per pattern can be recycled.
A second option to reduce the excess paste and pollution from the rinse water is the use of a rubber ball in the squeegee. After printing, the ball (25 – 30 mm diameter) scrapes the squeegee clean and the excess paste is transported back to the dye kitchen.
Reduction of dye paste emissions and water consumption. The quantity of washed out sludge can be reduced by 5 – 35 % at the overall corporate level.
This measure is applicable as a replacement investment for rotary screen printers.
The additional costs are around EUR 50 000 (INR 2 500 000) Savings can be achieved on raw materials and auxiliary materials as well as wastewater charges. Because of the additional costs this measure is especially feasible when the rotary screen printers are being renewed. End of Rotary-Screen Printing Machine article