Color difference, also known as color deviation, is one of the typical quality defects in the printing process. In the production process, the color of printed products does not match the color of proofed samples, or the color mixing fault after pattern and picture overprint often occurs, which will affect the product quality, or seriously scrap the whole batch of products, resulting in color deviation and color mixing fault, which can be summarized as the following reasons:

1. The dot of a certain color of yellow, magenta and cyan caused by non-standard plate making operation is too deep or too shallow.

This mainly refers to that in the process of printing plate drying, the light source intensity and spectrum of printing plate do not match with the photosensitive characteristics of printing plate, or the exposure time is improper, and the pH value of developer and the length of development time are not properly controlled, which may cause the printing plate dot to be too deep or too shallow.

2. Improper ink color allocation or mismatch of three primary color inks. That is, it is not the same brand and model of ink.

3. Unreasonable color sequence arrangement mainly refers to the color sequence arrangement of multi-color offset press.

4 printing paper itself has serious color deviation.

5. Color mixing is caused by serious dirt on the blanks on both sides of the printing plate (common in semi satellite offset press).

6 when changing color, the ink roller cannot be cleaned.

7 abnormal paper feeding.

8. The version change was not timely.

9. The sample signer is not responsible

10 ink imbalance.

For the above reasons, the offset press operator must pay attention to the following aspects:

When correcting the ink color, the printing can be started only when the ink color basically conforms to the sample. The one-sided pursuit of output often starts printing when the ink color is far away from the printed sample, which is bound to cause a large color difference between the front and rear printed products. The correct operation should be: after the printing plate is calibrated, use the master paper to correct the ink color, and the trial printing sample must basically meet the printing sample before normal printing.

2 generally, the sample signer must sign the sample in a short time to reduce the occurrence of color difference.

3 correctly grasp the ink balance, and pay special attention to the pH value of the wetting solution. Under the same ink amount, large water and small water will also affect the color. The principle of water consumption is to use the minimum liquid supply without hanging dirty.

4 determine the frequency of cleaning the blanket according to the paper quality. If the paper quality is poor and the blanket is not cleaned in time, it will also cause color difference.

5. Ensure that the paper feeding is normal. Each paper feeding pause will cause a product to be too deep. Therefore, we should form a good habit, that is, take off 6 ~ 8 pieces of products when printing after paper feeding stops, so as to avoid mixing in the finished products and causing color difference.

6. If the printing plate of long version products is found, it shall be replaced in time. The reduction of the adsorption capacity of the printing plate to the ink will also cause the depth of the product imprint and form a color difference

For the products printed on the front and back, we must pay attention to the depth of the front and back, and often compare with the ink color of the products on the back, so as to prevent the deeper printing or the lighter printing from affecting the quality of the products. As far as possible, the products of cross page puzzle shall be printed on the same machine and in the same shift, otherwise, serious quality accidents will be caused.

Tom (oversea manager) Phone:0086 13303078975 / 17772697357(whatsapp,wechat,line)

Email :cartonmachine.tomwang@aliyun.com

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