The problem of inaccurate overprinting of jigsaw hot stamping patterns
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The so-called hot stamping alignment is the process of overprinting the pattern on the surface of the paper after printing the pattern on the surface of the paper. During the implementation of the process, there is often a problem that the printed pattern and the hot stamping position are inaccurate. Analyze from the following aspects.
1. Paper stretch control
Paper stretching is the most frequent and difficult to control factor in the printing process. In the printing process, it is impossible to completely eliminate the paper stretching, but it is possible to control the expansion value in a relatively stable range. How to control the expansion and contraction of paper is the basis for implementing the stamping process of hot stamping. The stability of the newly imported paper is generally quite poor, for the following reasons.
(1) The inside of the paper is still in a fairly unstable state (such as the amount of water content) and must be left for a period of time before reaching a steady state.
(2) Changes in ambient temperature and humidity during transportation can also cause changes in the dimensional stability of the paper.
Therefore, for the newly-introduced paper, it should be stored in the printing workshop for 2-3 weeks after the material is opened, so that it can be stretched and deformed in a stable state under the production environment, and then bundled with a shrink film, and then opened again when used.
2. Control of hot stamping process
Pattern positioning hot stamping is the key to this technology. It is necessary to use scientific process schemes and statistical principles to perfect this process and try to eliminate the problems in the bud. The following schemes can be used for hot stamping.
(1) Film positioning method. In the hot stamping process, the film is used for hot stamping, that is, the position of the hot stamping pattern is checked by using a film to ensure that the position of the pattern in the paper is accurate. In the process of adopting this method, it is necessary to press the gauge line at the central edge of the paper to facilitate the stability check and post-processing inspection of the hot stamping line.
(2) Contour positioning method. The outline of the pattern to be stamped (the size of which can be slightly improved) is printed with a light outline first by the printing device, and then stamped against the printed outline. This method is beneficial for the machine personnel to detect the accuracy of the hot stamping position in time.
(3) It is necessary to pay special attention to the fact that in the hot stamping process, the consistency of the two stamps (pre-rules and side gauges) must be absolutely guaranteed, otherwise the consequences will be disastrous.
3. Control of the printing process
If the above two aspects are controlled, then the printing process can be done according to the "rules". If problems occur during the control process, the following measures can be taken to remedy the problem.
(1) For products that are not in paper processing, you can use the humidity control method to record the paper conditioning time and environmental status in the form of a table, record the process in detail, and record the humidity control process after the small batch test is successful. And product analysis. Then develop a standardized humidity control process plan, implement the process plan, and finally complete the printing process.
(2) If the two rules are unstable during the hot stamping process, the method of drawing can be used for the division printing (if the hot stamping rules are too messy, the batch of products will be scrapped).
It can be seen from the above analysis that if the problem is left in the printing process and then solved, it will be in a passive state, so it should be prevented and solved as soon as possible. At present, although the hot stamping process is very mature, there are still some unexpected problems in many new application fields. These problems require the printing process researchers to carefully summarize the problems and work tirelessly to make the hot stamping more perfect.