Several methods to control the quality of digital prints

For digital printers, it is an important task to find and correct errors in the data files submitted by customers in the shortest possible time, and to meet the individual needs of customers for products. The main methods of digital print quality control are:

1. Network Control

Digital printing adopts digital hybrid screening technology, which draws on the characteristics of AM screening, FM screening and digital control hybrid screening technology. Operability. Compared with traditional screening technology, this screening technology has greatly improved both in output speed and resolution, and its perfect combination with CTP technology can make prepress or printing present perfect dot effect.

2. Color Control

Color is an important measure of how well an image is reproduced. Color control in traditional printing is based on density control. Specific methods include gray balance, color correction, optimal printing density control, dot control and transfer. The digital printing process is an open system, and the input, processing, and output devices may come from different manufacturers, and the color description and expression methods of different devices are also different. With the increase of the number of uses of the same device, the difficulty of color reproduction also increases. The color information of color images must not only be presented on different display devices, but also transmitted between different media. In this regard, the international color organization ICC has developed the ICC Profile profile to describe the color characteristics of the device, through which cross-platform color communication can be realized.

3. Data output and management

With the advancement of the digitalization process, the amount of data is increasing, which requires optimization of the data transmission and management process on the network. To this end, in the field of prepress, the OPI (Open Prepress Interface) specification and the DCS (Desktop Color Separation) specification have been formulated. The OPI specification contains a series of Postscript-compliant comment statements, allowing low-resolution images to be used instead of high-resolution images during imposition, and automatically replaced by high-resolution images by the OPI server during color separation output, reducing the amount of data in network transmission. The DCS specification contains a main EPS file and multiple high-resolution color separation files. It extends the EPS file format and manages the entire color separation process of a desktop publishing system. It can shorten production time, reduce equipment requirements, and ensure data files. Not missing in transit.

4. Printing registration control

In digital printing, a CCD camera is often used to monitor the registration of the printing press, and automatic registration control is carried out through the printing press. The advantage of using a CCD camera for registration is that it adopts image processing technology, and the registration accuracy is high; it allows other content to be printed around the printing detection color mark; it can automatically distinguish the color mark and non-color mark content; improve the utilization rate of the substrate; Can adapt to very small color scale; fast registration.