Causes and practical treatment methods of ghosting

The causes and practical treatment methods of print ghosting

Print ghosting is one of the common faults that affect quality and efficiency. Correctly analyzing and accurately judging the causes of ghosting, and taking effective solutions in time, is a problem worthy of the attention of operators and managers. Below, I will talk about some understandings based on my practical work experience

I. equipment factors

1 In modern commercial printing with magazines as the main body, tissue printing has gradually become the mainstream, and is developing towards 65g/m2, 70g/m2, 80g/m2 light coated paper or 80g/m2 coated paper. As the thin paper has high requirements on the pressure and uniformity of the teeth on the imprinting cylinder, once the pressure of the teeth on the imprinting cylinder of a certain color unit is not appropriate, it will cause the color imprint to not overlap with other color imprints and cause ghosting failure

fault characteristics: (1) good and bad overprint occur alternately for every two consecutive prints (the three times diameter impression cylinder occurs alternately for every three). (2) It is mainly easy to happen when printing on thin paper. The judgment method is to take out about 10 prints, rush on the sample table and shake it open, and observe whether there is such a rule with a magnifying glass

treatment methods: (1) cut off the first group of ink rollers and printing pressure, and close the second, third and fourth groups of ink rollers and printing pressure. If the ghosting disappears, it means that the problem is in group 1. On the contrary, continue to judge. (2) Open the tooth row of the unit in question, clean the dirt in the tooth pattern, and replace the worn tooth. (3) Use 105g/m2 coated paper to adjust the pressure of each row of dental discs until the pressure is uniform and appropriate

2. The tooth ball on the imprint cylinder is damaged

fault characteristics: (1) whether the paper is thick or thin, it will appear; (2) Due to the non rotation of the teething ball, there is a serious circumferential dislocation during printing, and one of the two consecutive prints will have a serious ghosting. (3) The occurrence time should be that the maintenance of the teeth is not long or there are other factors that can rule out the teeth

treatment method: replace the damaged open tooth ball, and ensure that the butter in the open tooth ball is replenished in place during normal maintenance

II. Paper factor

1 The orientation of paper strands affects the printability

due to the characteristics of the orientation of paper strands and their susceptibility to moisture and expansion, some paper directions do not have printability. When the paper is affected by factors such as moisture and pressure in the printing process, a deformation from rectangle to trapezoid may occur, so that each color impression is different

fault characteristics: (1) each print has different degrees of ghosting. (2) The same printing plate, the same thickness or different thickness of printing sheets will not appear ghosting. Also make the sample slip in the process of the experiment

treatment methods: (1) re select the color sequence, and put the black ink in the last group. (2) Change the printing direction of the paper (such as large folio to large quarto printing)

2. Uneven moisture absorption of paper

insufficient humidity in the workshop environment causes tight edges and serious deformation of paper, which is easy to cause ghosting in the printing process

fault characteristics: (1) the deformation of the paper can be clearly observed. (2) The paper with a ration of about 128g/m2 is the most obvious

treatment methods: (1) quickly heat up, put some boiled water under the paper table, and then cover the paper with a plastic cover, so that the paper can quickly absorb water in the water vapor. (2) Hang the paper again or spray water around the paper

III. accidental factors

1 The printing plate or blanket is loose

the printing plate or blanket is loose, and each time the printing plate is transferred to the blanket, the impression will be different, resulting in ghosting failure

fault characteristics: (1) the printing machine is accompanied by a large abnormal sound. (2) Thick paper and thin paper will happen. (3) Each print has a double image

treatment method: tension the printing plate blanket

2. Unreasonable selection of mouthpiece and trailing tip

1. Main use: the selection of mouthpiece and trailing tip is unreasonable. If the layout on the side with less graphics and text and light ink is used as the mouthpiece, double shadows will be produced on both sides of the trailing tip due to local large amount of ink and paper deformation

treatment method: swap the mouth and drag slightly, and the ghosting will be eliminated

although the causes of ghosting in the printing process are complex, according to the characteristics of ghosting caused by different reasons such as equipment, paper, environment and technology, we can quickly find out the main causes and then eliminate them pertinently

source - printing technology