Digital Operator Q&A: Correcting Inconsistent UV Coating and Web Breaks
Question From An MGX Customer & HP Indigo Roll Press Operator:
Our company has experimented with cheaper digital stocks from other suppliers. While attempting to print on some of these products, we are experiencing inconsistent UV coating and frequent web breaks. We’ve also noticed a shorter blanket lifespan: we are finding that we need to replace the blanket more often then we used to. All of these issues are causing downtime on our press and the UV coating inconsistencies are resulting in rejected labels, reprints and waste. Why are we experiencing these problems with non-MGX stock?
Answer:
It is likely the stock that you are describing hasn’t been treated with a contiguous coating. Every MGX digital material is optimized with the best contiguous coating process in the industry, which will give you the best possible print quality, consistent UV coating, and long blanket life. Other materials on the market are not coated; rather a digital solution is mixed in the pulp at the time of manufacture. This method of treatment is usually less expensive but can cause a multitude of digital press issues including brittleness, web breaks, inconsistent UV coatings, and shortened PIP and blanket life. Here’s a little more detail on the issues raised in the query above:
Coated vs. Non-Coated Materials 
Substrates can be digitally treated when the paper is manufactured by mixing digital coating with the paper fibers. This creates a substrate with digital coating “peppered” throughout the entire substrate. Digital inks will adhere to this coating during printing; however, this coating method leaves many areas of the substrate untreated for digital printing. As you can see in the diagram on the right, the black orbs in the diagram illustrate the digital-receptive coating. As the picture shows, many microscopic areas of the material’s surface will be left without digital treatment. Because of this, digital inks will only adhere to the portions of the material that contain the digital coating, leaving many uncoated “holes” within the material. Therefore, digital inks can lift off of the non-coated portions of the substrate which can cause picking and ink lift-off. Ink lift-off from the substrate can also stick to the digital press blanket, leading to more frequent blanket replacement and press downtime.
UV Coating Inconsistencies
The entire surface grain of these other materials is not consistently coated, which can lead to inconsistent UV coating. One MGX customer experienced these problems when using a cheaper, non-coated product – a glossy UV coating appeared matte and splotchy on the finished printed product and was subsequently rejected by the client. Another downside to this coating method is that the digital treatment is embedded throughout the substrate and not just on the surface of the material. This can cause the substrate to be brittle, causing web breaks, downtime, and potential problems on your press. One MGX customer using a non-coated material experienced three web breaks and over an hour of downtime on their machine due to the brittleness of the non-coated stock.
Digital materials coated with a contiguous coating method are evenly coated throughout the surface of the substrate. You can see the difference in the graphic (right), with the digital coating pictured in black. As the diagram illustrates, contiguous coating leaves no breaks or “holes” in the coating so the ink is always in contact with the digital treatment. Substrates with contiguous coating feature heavier ink coverage so colors have the potential to be as rich and vibrant as possible. Items digitally printed on contiguous-coated substrates are also more robust and durable with little to no ink lift-off in tape tests and less web breaks during production.
Extended Blanket Life
Contiguous-coated materials also extend the life of your blanket as there is less residual ink that adheres to the blanket. Digital ink that flakes off the non-coated portions of the substrate will stick to the blanket, leading to more frequent blanket replacement and less downtime. Extended blanket life saves you time, money and maintenance hassles.
