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The phenomenon of twisted net refers to the irregular deformation of the rotary net during operation, which affects the alignment accuracy of the rotary net at light level, and causes twisting of the net in severe cases, making the rotary net scrapped.
1. The circular mesh and the guide belt are not synchronized
When the rotary screen printing machine is working, the linear speed of the guide belt is required to be 2%o-4%o faster than that of the rotary screen, that is to say, the guide belt should drag the rotary screen to run. Conversely, if the rotary screen is faster than the guide belt, the conductive belt will produce reverse friction on the rotary screen to hinder the rotary screen from running. Since the rotary screen is made of very thin metal material with low strength, when the resistance of the conduction band exceeds the strength of the rotary screen, the rotary screen will be deformed and twisted. Generally, a rotary screen is used to print on the guide belt, and then the size of the pattern printed on the guide belt is measured to determine whether the rotary screen and the guide belt are synchronized. The pattern of the 640mm circular screen printed on the guide belt is generally controlled between 642.5 mm and 643 mm.
The following are the reasons and solutions for the asynchronous rotary screen and the guide belt of the rotary screen collective transmission printing machine and the rotary screen independent transmission printing machine:
(1) For the printing machine driven by the rotary screen collectively, the main reasons for the asynchrony between the rotary screen and the guide belt are that the diameter of the main drive roller of the guide belt is too small, and the neutral layer of the printing guide belt is not correct. The linear speed of the surface of the guide belt depends on the diameter of the main drive roller of the guide belt and the position of the neutral layer of the guide belt. The effective radius R of the guide belt drive roller, R is the radius of the guide belt drive roller + the thickness of the neutral layer of the guide belt. In the long-term operation of the printing machine, the diameter of the main drive roller will become smaller due to corrosion, and the change of the neutral layer of the guide belt due to the aging of the rubber and the change of the flexibility of the guide belt will affect the change of the neutral layer. In addition, the neutral layer of the printing guide belt of different manufacturers is also different. , which causes the linear velocity of the surface of the conduction band to be different. Generally, it is used to replace the main drive roller of the guide belt or replace the printing guide belt of different manufacturers.
(2) The rotary screen independent drive printing machine has no special requirements for the diameter of the printing belt drive roller and the neutral layer of the printing belt because the rotation speed of the rotary screen can be corrected by electronic gears (also called synchronization coefficient or friction coefficient). The asynchrony between the rotary screen and the guide belt is mainly caused by the improper setting of the electronic gear. Generally, the problem that the rotary screen and the guide belt are out of synchronization can be solved by resetting the electronic gear.
(3) For different fabrics, due to the different degree of smoothness of the surface, the friction coefficient is also different, and the phenomenon that the circular mesh and the guide belt are not synchronized will also occur. For the rotary screen independent transmission printing machine, it can be solved by fine-tuning the electronic gear (synchronization coefficient or friction coefficient), but for the rotary screen collective transmission printing machine, it can only be solved by reducing the blade pressure.
2. The passive side bearing of the rotary mesh head seat is not flexible
At present, the existing rotary screen printing machines all use rotary screen unilateral transmission. Since the rotary screen is made of very thin metal materials and has low strength, when the passive side bearing of the rotary screen head seat is inflexible, there will be torsion. network phenomenon. You can check whether the rotary screen bearing is flexible, replace the damaged bearing in time and strengthen the maintenance and refueling of the rotary screen bearing.
3. The gap between the circular mesh and the guide belt is too small
When the gap between the rotary screen and the printing guide belt is too small, especially the gap on the passive side is too small, the bulkhead of the rotary screen on the passive side will be close to the guide belt, and the printing guide belt will run with the rotary screen. The linear velocity between the guide belts is not a completely synchronous relationship, which causes the velocity of the two ends of the cylinder to be different, resulting in a twisted mesh. Normally, the gap between the rotary screen and the guide belt is generally 0.3mm, but due to the improper adjustment of the gap between the rotary screen and the guide belt during debugging and maintenance, the gap between the rotary screen and the guide belt is too small or there is no gap.
