PU Leather Composition Notebooks A Few Easy To Overlook Problems in PS Plate Drying

PU Leather Composition Notebooks A few easy to overlook problems in PS plate drying

 

The purpose of printing is to reproduce high-quality printed matter, and the color registration and accuracy of printed image are very important index parameters to evaluate image quality. For a long time, people have paid enough attention to the quality of the outlet of the pre-press film, pay attention to the transfer of the outlet in the printing process, and the outlet on the film is transferred to the PS plate. However, they do not pay enough attention to, and even ignore some very important issues. According to the experience of taking students to the factory for internship, the author summarized the following problems that many factories currently ignore some seemingly simple but important printing problems:

 

First, the correct operation of the graphic dot transfer from film to PS version

The most commonly used in China is a positive image type PS plate, which is a plate that is coated with a prepared photosensitive liquid on a surface-treated aluminum plate, heated and dried to form a photosensitive layer, and made of a pre-coated plate for storage. When printing the plate, the photosensitive plate coated with a photosensitive layer is closely exposed to the positive plate, the photosensitive agent in the light part is decomposed, nitrogen is released, causing the cracking of the ring, the molecular structure is rearranged, the indenone compound is generated, and the indenic acid compound is generated when the water is met, the photosensitive layer that has been seen to decompose is removed by development treatment, and the non-photosensitive area, that is, the graphic part of the layout, is preserved and made into a printed plate.

 

We know that the contact between the film and the photosensitive layer of the PS plate is an important factor affecting the quality of the printing plate, the contact state is different, the dot change law is different, and the good contact is a prerequisite for the controlled transfer of dot regulation. The operation should be strictly relative to the film surface, pumping air tight, to ensure a good transfer of graphic dot. However, there is still a situation in the production of the drug film face back, due to the thickness of the substrate will cause the scattering of light, dot transfer is not uniform, its change is uncontrollable, should be strictly avoided. In daily production, there are more problems in this area, as described below.

 

① The printing machine itself has poor vacuum contact, and the glass and rubber of the printing frame are uneven. Good printing machine rubber pad should be raised in the middle, otherwise the suction offset; If it is not smooth, it is necessary to pad a cloth in the middle to pump air and wear it flat.

 

② The pumping capacity of the vacuum pump is too low. A good printing machine adopts segmentation pumping, which is sufficient to ensure that it is tightly combined with vacuum-pumping for good contact.

 

(3) Overlapping L-3 small pieces on the Mosaic film and pasting tape on the edge of the picture, resulting in untrue pumping and local picture edge deficiency. The cutting of the negative is inconsistent, and the distance between the base edge of the film is different, resulting in different deformation of the spelled out text.

 

④ Some of the original film and plate on the dirt, resulting in local pumping is not tight, dot deficiency.

To solve these problems, the author puts forward several suggestions:

 

1. Ensure that the printing equipment is in good working condition to ensure that the pumping can be vacuumed and the film is in good contact.

 

2. Carefully check the film before printing to minimize duplication of the Mosaic picture and excessive adhesive tape.

 

3. Check the printing table glass, PS plate and film, no dirt.

 

4. Add scattering film or diffusion film, use segmented exposure or double exposure to reduce film lines and dirty spots.

 

Second, the registration of the printing plate itself

For a film set, we pay attention to their registration, and when the text is transferred to the plate, its registration is handed over to the next process: printing. In fact, some operations in production often cause the plate itself to fail to register:

1. Film transfer occurs during printing.

 

2. The temperature in the baking plate is unstable or uneven, resulting in different degrees of deformation of the printing plate.

Because the printing plate is not allowed to print, it is necessary to carry out correction operations such as plate drawing, which inevitably causes graphic deformation.

 

In this regard, the author thinks that: in the composition or out of the film, even if you pay attention to the registration of the picture, in the printing plate, you can not take it lightly, thinking that the printing plate must be set, only strict process specifications, in order to print a high-quality qualified printing plate. A good printing machine has a plate punching positioning device, which is compatible with the printing press's plate loading device to ensure the plate registration accuracy. Such as Heidelberg, there is a professional printing plate positioning device, and the automatic loading device of the printing press, so that the operation of the drawing plate in the printing is minimized, almost no use. When the long plate must be baked, it is necessary to make the baking machine work in a stable working state to ensure the consistency of PS plate deformation.

 

As an intermediate of graphic information transfer, the quality of the printing plate directly determines the quality of the printed text, so it must be paid full attention to, can not take for granted, bring trouble to the printing operation, and the text can not be well reproduced.