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細(xì)度不夠，顏料顆粒太大或者混入顆粒性雜質(zhì)的話，均會(huì)導(dǎo)致刀絲的出現(xiàn)。因此應(yīng)該選擇質(zhì)量較好的油墨，其顏料顆粒應(yīng)該小于10μｍ，應(yīng)該在輸墨系統(tǒng)中加入過濾裝置，并且經(jīng)常對其進(jìn)行檢查，以免油墨中的雜質(zhì)粗顆粒損傷印版和刮墨刀。

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，應(yīng)采用材質(zhì)緊密、軟硬適度的自磨型刮刀。一般來說，硬的刮墨刀比軟的刮墨刀產(chǎn)生的刀絲要多，當(dāng)刮墨刀刀口受到損傷出現(xiàn)缺口時(shí)，會(huì)在承印材料上產(chǎn)生有規(guī)律的左右移動(dòng)的油墨痕跡。細(xì)微的刮墨刀缺口可用細(xì)砂紙打磨光潔平整，如果出現(xiàn)較大的缺口則需要更換。因此在安裝刮墨刀時(shí)需要平整，裝刀前還要仔細(xì)檢查刮墨刀是否有缺口，裝刀后仔細(xì)研磨，如若在印刷過程中有刀絲現(xiàn)象，須停機(jī)進(jìn)行研磨，并且嚴(yán)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.

印版上鍍鉻層的表面光潔度、硬度等都會(huì)對刀絲的產(chǎn)生有重要的影響。塑料凹印所用油墨的顏料一般以顆粒狀態(tài)分散在連接料中，在印刷過程中，油墨布滿網(wǎng)孔后，多余的油墨被刮刀刮去，同時(shí)不斷的摩擦印版表面。如果印版表面鍍鉻層硬度不夠，則很容易被粗顆粒油墨劃傷而產(chǎn)生刀絲。另外，還應(yīng)嚴(yán)格控制好滾筒加工精度與安裝精度，防止偏心超標(biāo)，以免在高速印刷時(shí)對刮墨刀產(chǎn)生沖擊而產(chǎn)生刀絲。

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，印刷車間的溫度、濕度和空氣潔凈度均會(huì)影響到刀絲的出現(xiàn)。如果溫度過高，則溶劑揮發(fā)太快，油墨干燥過快，如果濕度太大，油墨溶解不良，粘度變大，刮墨困難，這兩種情況均會(huì)容易造成刀絲的出現(xiàn)。因此在印刷過程中，溫度應(yīng)控制在18～23℃，濕度控制在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%.