In the process of plastic gravure printing, knife wire phenomenon often appears. The causes are very complex, involving plate making, ink, scraping knife and environment. So, how to solve this phenomenon? Today, let's take a look at it.

1、油墨方面。

1. Ink.

塑料凹印所用的油墨如果细度不够，颜料颗粒太大或者混入颗粒性杂质的话，均会导致刀丝的出现。因此应该选择质量较好的油墨，其颜料颗粒应该小于10μｍ，应该在输墨系统中加入过滤装置，并且经常对其进行检查，以免油墨中的杂质粗颗粒损伤印版和刮墨刀。

If the ink used in plastic gravure printing is not fine enough, the pigment particles are too large or mixed with particulate impurities, it will lead to the appearance of knife wire. Therefore, we should choose a better quality ink, the pigment particles should be less than 10 μ m, should be added in the ink system filter device, and often check it, so as to avoid the ink impurities coarse particles damage the printing plate and scraper.

2、刮墨刀方面。

2. Doctor blade.

刮墨刀是塑料凹印中的重要部件，应采用材质紧密、软硬适度的自磨型刮刀。一般来说，硬的刮墨刀比软的刮墨刀产生的刀丝要多，当刮墨刀刀口受到损伤出现缺口时，会在承印材料上产生有规律的左右移动的油墨痕迹。细微的刮墨刀缺口可用细砂纸打磨光洁平整，如果出现较大的缺口则需要更换。因此在安装刮墨刀时需要平整，装刀前还要仔细检查刮墨刀是否有缺口，装刀后仔细研磨，如若在印刷过程中有刀丝现象，须停机进行研磨，并且严禁磨刀油混入到油墨中。

The scraper is an important part of plastic gravure printing. It should be self grinding scraper with compact material and moderate hardness. Generally speaking, a hard blade produces more thread than a soft blade. When the blade of the blade is damaged and there is a gap, it will produce regular left and right ink marks on the substrate. The small gap of the doctor blade can be polished with fine sandpaper until it is smooth. If there is a large gap, it needs to be replaced. Therefore, it is necessary to level the blade when installing it. Before installing the blade, it is also necessary to carefully check whether there is a gap in the blade. After installing the blade, it is necessary to grind it carefully. If there is knife thread phenomenon in the printing process, it is necessary to stop the machine for grinding, and it is strictly forbidden to mix the knife oil into the ink.

3、印版方面。

3. Printing plate.

印版上镀铬层的表面光洁度、硬度等都会对刀丝的产生有重要的影响。塑料凹印所用油墨的颜料一般以颗粒状态分散在连接料中，在印刷过程中，油墨布满网孔后，多余的油墨被刮刀刮去，同时不断的摩擦印版表面。如果印版表面镀铬层硬度不够，则很容易被粗颗粒油墨划伤而产生刀丝。另外，还应严格控制好滚筒加工精度与安装精度，防止偏心超标，以免在高速印刷时对刮墨刀产生冲击而产生刀丝。

The surface finish and hardness of the chromium plating layer on the printing plate will have an important impact on the generation of the cutter wire. The pigment of plastic gravure printing ink is generally dispersed in the binder in the form of particles. In the printing process, when the ink is full of mesh, the excess ink is scraped off by the scraper, and the printing plate surface is constantly rubbed. If the hardness of the chromium plating layer on the printing plate surface is not enough, it is easy to be scratched by coarse-grained ink and produce knife wire. In addition, the machining accuracy and installation accuracy of the drum should be strictly controlled to prevent the eccentricity from exceeding the standard, so as to avoid the impact on the doctor blade and the generation of cutter wire in high-speed printing.

此外，印刷车间的温度、湿度和空气洁净度均会影响到刀丝的出现。如果温度过高，则溶剂挥发太快，油墨干燥过快，如果湿度太大，油墨溶解不良，粘度变大，刮墨困难，这两种情况均会容易造成刀丝的出现。因此在印刷过程中，温度应控制在18～23℃，湿度控制在50%～60%。

In addition, the temperature, humidity and air cleanliness of the printing workshop will affect the appearance of cutter wire. If the temperature is too high, the solvent volatilization is too fast, the ink drying is too fast, if the humidity is too high, the ink dissolves poorly, the viscosity becomes larger, and the ink scraping is difficult, both of these two situations will easily cause the appearance of knife wire. Therefore, in the printing process, the temperature should be controlled at 18 ~ 23 ℃, and the humidity should be controlled at 50% ~ 60%.