Why isn’t my pad printing ink cup ring doctoring the plate?

Why isn’t my pad printing ink cup ring doctoring the plate?

There are a couple reasons why an ink cup ring would not be doctoring (cleaning) the plate. Here are the most commons causes for this issue:

1: Insufficient ink in the cup

When mixing pad printing ink, it is important to use the right amount of ink for your ink cup. You should always mix enough ink to fill at least 60% of the cup. This would be the minimum amount required for you to properly pad-print. Always use an adequate amount of ink to achieve the desired results.

Reason 2: Scooping: Spots on Prints

There are several causes of scooping. Using magnetic cups can often lead to one of the issues. The magnet will at times pull the plate, causing the cup to scoop ink from certain areas.

The second cause, which is most common, occurs when printing on bold etch—in such a situation, there is not enough support from the ink cup. This results in the ink cup dipping (scooping) into the etch and scooping ink over time. This eventually leads to uneven ink distribution and the formation of bald spots on the prints. To solve this problem, use low-count screen film when developing the plates. About a 150-line screen.

Lastly, using a "pointy" printing pad will cause scooping. Use a flat-sided printing pad.

In conclusion, to address these issues, always ensure that the ink cup is filled with the right amount of ink and that there is enough support in the cup, especially when printing bold logos, to prevent scooping.

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