How to Troubleshoot Offset Ink Piling
A good pressman makes running an offset printing press look easy; it is not. A wide range of factors must be maintained within very tight tolerances or a variety of printing problems arise. Piling is when ink builds up on the blanket, a rubber cylinder covering used to transfer ink to paper in offset printing. The ink then begins picking fibers off of the paper being run through the press, thereby ruining part of the image being printed. These paper fibers build up on the blanket along with the ink.
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Instructions
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Check your ink and water balance and adjust your dampener settings if necessary. Running too little water can lead to ink drying on the rollers and becoming too tacky. Also, running too much water can cause the ink to become waterlogged. Either of these imbalances can cause piling.
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Check your fountain solution mixture proportions. Incorrect amounts of etch in the fountain solution can make ink more prone to dry up on the rollers, especially when running a thin film of ink.
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Check your ink levels. Ink levels that are too low can lead to ink drying on the rollers, which can cause piling. Wash the blanket and perform a test running more ink to see if this eliminates the piling. Request a new plate with the curves adjusted to enable you to run more ink if this is the cause of the piling.
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Back off the squeeze between the blanket and impression cylinder. Having the squeeze too tight can cause piling, as well as too much dot gain.
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Wash the blanket and check it for tackiness with your hand. A blanket that is too tacky is often the cause of piling. You must change to a harder blanket if blanket tackiness is the problem. Changing to a blanket wash that isn't as hot sometimes eliminates this problem without having to change blankets.
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Check the blanket height over bearer with a blanket gauge. Blanket height being too low can cause piling. Changing and repacking the blanket is a good idea. This eliminates two potential problems: incorrect packing and a defective blanket, either of which can cause piling.
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Check the roller settings of the press, paying special attention to the dampener roller, as well as the form roller to plate cylinder setting. Incorrectly set rollers can cause an uneven ink film, leading to piling. This is especially true in the case of the form roller to plate setting as this the roller that ultimately inks the plate itself. Setting the rollers correctly eliminates this problem.
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Wash up the press and perform a test using a softer ink. Ink that is too tacky is a common cause of piling. You must change to a softer ink or use additives to lessen the tack to eliminate the piling, if this is the cause.
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Perform a test with a different paper stock. If the problem doesn't lie with the press settings, the blanket, the fountain solution or the ink, it will usually be the paper itself. You must request a change of paper stock to eliminate the piling if this is the case.
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References
Resources
- Photo Credit printing house image by Izaokas Sapiro from Fotolia.com
