introduction
In fact, post-press processing has no effect on print quality, but it affects print quality. Printing quality is determined by pre-press and printing process, equipment, materials and technology, and also related to operator and factory management. One of the purposes of establishing JDF standard and developing digital workflow system is to reduce human factors to the final result as much as possible. The effect of forming a stable and continuous production process. Printing quality is controlled by many factors, and the relationship is quite complicated. Judging the quality of printing is not an easy task, because the print is first a visual product, subjective quality judgment is inevitable. However, subjective quality judgment also brings randomness or individuality of results, and the judgment results vary from person to person.
The printed matter should be a complete industrial product. In addition to providing graphic content, it should also have a function that meets the needs of consumers. Sometimes it must protect the printed content and may also beautify it. The use function or other additional attributes of the printed matter cannot be provided by the pre-press and printing process, which is mainly guaranteed by the post-press processing process.
Since the post-press processing technology is basically unrelated to the print quality, the post-press processing quality inspection and evaluation method is also different from the print quality inspection and judgment, and should have its own unique inspection method and evaluation standard. However, it must be pointed out that the formulation of the JDF standard does not solve the problem of quality inspection and evaluation of post-press processing, because the JDF standard is neither a printing quality standard nor a printing quality standard. In fact, the JDF standard is used to guide system integration, digital workflow software development, and equipment production. It considers the standardization of production from a system perspective and strengthens the connection between production resources and elements.
Post-press processing JDF process
JDF regulates production behavior and guides equipment manufacturing and system software development by defining key printing processes or processes. In summary, in addition to the 10 general processes involved in business activities and enterprise management, there are 28 pre-press processes defined by the JDF standard, such as layout control, color control, pre-flying inspection, ink zone generation, color separation and layout Etc .; two printing processes, namely traditional printing and digital printing. The integrated digital printing of the earlier version was cancelled due to the addition of a combined process node in the new version of the JDF standard. Although the number is small, the control content is too much, so it is not simple . Post-press processing faces a large number of production processes and equipment, so the post-press processing defined by JDF is also the most, with a total of more than 40 kinds.
In general, post-press processing is divided into two types: books and periodicals and packaging, but some processes are applicable to both, such as cutting paper, punching, strapping, and carton packaging. In principle, each post-printing process corresponds to a piece of equipment, and slightly more complicated equipment may be decomposed into two processes, such as equipment that provides both die-cutting and indentation functions into two post-printing processes: die-cutting and indentation However, the multi-functional characteristics of post-press processing equipment are not as typical as digital presses. At present, digital presses facing the commercial market are often the integration of pre-press (called digital front-end system), printing and post-press processing.
The post-press processing related to books and periodicals includes book shell preparation, book cover making, book cover placement, soft cover application, folding, folding, page matching, matching, insert, spine preparation, gluing, spine backing, Binding, metal clip binding, plastic comb binding, spiral binding, ring binding, saddle stitching, lock thread flat binding, plastic wire ironing, metal wire comb binding, adding caulking cloth, adding protective seal and cutting, etc. . It can be seen that JDF has defined the post-printing process of books and periodicals quite well, which may be related to the equipment manufacturing companies participating in the formulation of standards.
The post-printing process mainly used for packaging includes number printing, laminating, indentation and die-cutting. It can be seen that JDF has not defined the post-printing process of packaging enough. It may be that the new version of the JDF standard needs to be added.
There are many processes that are difficult to define whether it should be post-press processing or packaging printing processing, such as paper cutting, labeling, punching, stacking, tightening and bundling, carton packaging, bundling, winding packaging and web slitting Wait.
The main purpose of listing these processes is to introduce the overall concept of the JDF standard, understand the relationship between the JDF standard and pre-press, printing, and post-press processing, and clarify those functions that can be achieved through the JDF standard, or allow you to master the entry point to solve the problem.
Main tasks of post-press processing equipment development
As long as the equipment manufacturer hopes that the equipment it produces is compatible with the JDF workflow and requires integration into the digital workflow system, the equipment must be designed and manufactured according to the JDF standard. Like computer network interconnection, physical integration is always at the bottom, providing the foundation and guarantee for process integration and management element integration, and interconnecting devices through relevant hardware. The existing equipment of the printing plant cannot be integrated into the digital workflow unconditionally. If the newly manufactured equipment is not organized according to the JDF standard, it cannot be integrated with other equipment unconditionally.
Therefore, the problem becomes obvious, and the post-processing equipment compatible with the JDF process must provide basic material conditions that can realize the interconnection of equipment. The industry term is called JDF interface.
This term very accurately describes the way and nature of the interconnection of equipment. It is similar to the interface cards widely used in the computer industry, such as display cards and network cards. It is required to be able to actively and passively exchange information with the outside world, that is, accept from process control. The instructions of the center, and can feedback the current status of equipment execution instructions and production tasks to the control center.
The JDF interface has its own peculiarities compared with the versatile interface cards such as display cards and network cards. First of all, the JDF interface is very professional. The parameters required by the JDF standard must be accepted to enable the post-press processing equipment to accurately determine whether the input resources meet the equipment and process requirements, and generate output resource information for subsequent process use. . Only in this way can the interconnection of equipment in a true sense be realized, and JDF post-press processing equipment should be given full play. Secondly, the JDF interface should conform to the communication specifications defined by the JMF format (JDF's sister format), and is divided into two forms of information communication within the system and outside the system. Therefore, not only the conventional communication functions of the interface card but also professional content must be considered. The job document format must be defined in accordance with the standard, and the JDF interface of other devices must be readable.
However, it must be noted that the JDF standard is not a standard for equipment manufacturing. It is at a macro level and only plays a role in regulating printing processes, equipment manufacturing, and system development. So far there is no macro level standard related to the details of equipment manufacturing and system development. For example, the ICC standard defines four color gamut mapping methods, but only some principles. The actual implementation needs to be further refined by the developer of the color management system, such as designing the conversion algorithm from color data RGB to CMYK color space. It can be seen that the formulation of the JDF standard does not solve the specific technical details of equipment manufacturing, nor can it solve the specific technical details of the JDF interface of post-press processing equipment, but only provides technical principles and frameworks.
In summary, the development of post-press processing equipment has nothing to do with printing quality, which makes the problem relatively simple. In addition, if you do not consider the compatibility with the JDF process, there is no problem at all, just consider the general functional elements of the device. However, if you want to produce post-press processing equipment that is compatible with the JDF process, you must also develop the JDF interface. It is worth noting that the development of this interface is not arbitrary, and should meet the basic requirements of the JDF standard in order to interconnect and communicate information with other devices that comply with the JDF standard.
Basic development principles
Before discussing this issue, we must first understand the difference between digital and analog devices.
The so-called digital equipment refers to digitally controlled equipment or hardware, and its important reference index is whether it can connect with the computer and exchange information. Analog devices also need to be controlled, except that the control method is different from digital devices. Most analog devices control device actions through switch boxes, remote controls, or similar means.
As mentioned earlier, the main feature of digital equipment is that it can be controlled by a computer, but the essence or control path of computer control lies in software. Anyone who has purchased and used a scanner knows that it is certainly not enough to make a physical connection between the scanner and the computer with a cable. You must also install the scan driver software to direct the scanner to work.
Back to the JDF interface problem. Assuming that the equipment produced by the post-press processing equipment manufacturer has a JDF interface, and this interface can be controlled by software after being connected to a computer, this equipment must be a digital device and must be compatible with the JDF workflow. It seems that the problem has become more and more complicated, but in fact it is not the case. After all, digital control reflects the essential properties of the JDF interface. Of course, whether it can be controlled by a computer is only a form, and the essential question is how to control the post-press processing equipment or by which way, because the implementation can be varied. If you consider from the perspective of actual needs, the JDF interface does not need to be done like a scanner to provide a fully functional driver software. Considering that post-press processing equipment often only needs to provide simple functions, it is not necessary to use hardware and software separation methods like scanners, and can be integrated together, for example, digital control functions are solidified into electronic circuits.
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