Imprint empty doubt

Recently, our printing press has a common phenomenon in one production.

After printing a batch of products (the product with a thin paper) and printing another product (this product with a thick paper), found the print imprint empty, after viewing the blanket and found the blanket on the imprint is empty, ie The initial judgment is that the pressure is too light. Take the method of increasing the rubber pad to increase the printing pressure, and then start the printing, and found that the void phenomenon still exists. As a result, the thickness of the blanket liner was increased and printing was restarted. The phenomenon of imprinting emptiness was also found. Then shut down again to find the cause of the phenomenon. Since the inner liner of the blanket has been added to be thick enough, this phenomenon has not improved any better, so it is not an empty phenomenon caused by too little pressure.

Replace blankets and liners with new ones and try printing again after power-on. This disappears. According to the actual situation, after a multi-analysis, the reason for determining the imprinting void phenomenon is that the blanket has high elastic energy during the imprinting process, that is, it can form a compressive deformation under the pressured state, and the blanket can recover quickly after the pressure is removed. To the original state. This kind of circumstantial physical phenomenon is the basic condition for ensuring normal printing, but this performance of the blanket is not immutable. If the excessive elasticity of the blanket, the elasticity of the blanket will also be harmed. This is our usual The blanket (including the blanket of the blanket) was "squeezed".

The phenomenon of "pressure collapse" will first be reflected in the part of the blanket, and irregular expansion and changes will follow. When this happens, there will be the strange and strange phenomenon that is mentioned at the beginning of this article. On the one hand, the blanket receives heavy pressure. On the other hand, the surface of the blanket is very empty. This is because the blanket and its backing material cannot be quickly or regained to their desired elastic height after being “crushed” under excessive pressure, resulting in insufficient pressure or local pressure when the blanket cylinder is in contact with the plate cylinder. Insufficient pressure causes the ink layer on the printing plate not to be completely transferred to the blanket and present a blank impression.

Source: "Printing World" Author: Wang Guangsheng