Based overlay registration accuracy screen printing machine

Overprint with multiple colors of ink based on the same reference point print overlapping color pattern printing technology, printing in the printing process through multiple ink to reproduce the original color, which requires each coloring are accurately aligned. If several colors are not aligned, printed printed materials will be completely different, namely the emergence of overlay errors.
During the printing process, is detected by marking a particular location on printed materials to achieve detection overprint error, this tag known as the Mark line (colored printed tag line), in the case of not confusing, also referred to as color mark.
Inefficient traditional visual inspection and easy to introduce human error, and as social production efficiency, visual inspection of the disadvantages are also increasingly obvious, and machine vision based intelligent detection technology has gradually into practical use. Using machine vision to do online testing not only has high accuracy, high efficiency, but also to overcome the many shortcomings of traditional visual detection. Second, an overview of machine vision
Machine vision is to use machines instead of human eyes do measure and judge, which uses computers to simulate human visual function, extracting information from the image of objective things, make the process and to understand, and ultimately for the actual testing, measurement and control. The greatest feature of machine vision technology is fast, informative, multi-function. Machine vision system is the goal to be ingested converted into an image signal by machine vision products (ie, the image pickup device, two kinds of sub-CMOS and CCD), sent to a dedicated image processing system, according to the pixel distribution and brightness, color and other information, change into a digital signal; image systems for various operations on these signals to extract target features, and then based on the results of determination to control the scene equipment movement.
Machine vision system consists of industrial-grade cameras, lenses, lighting, image analysis and processing software of four parts, which are self-contained four parts itself Field, performance and specifications quite a lot of things to be considered and applications much match . However, each part alone can not decide whether to apply to a particular application, simply put, machine vision involves various parts of the composition because of their professional different, and reached for the application of an integral, coupled with its other application itself A expertise, which makes the difficulty of producing a machine vision system is increased.
 the advantages of machine vision systems are:
① non-contact measurement, the observer and the observed person will not produce any damage, thereby improving the reliability of the system.
② has a wide spectral response range, for example, the human eye can not see infrared measurements, extends the human visual range.
③ long time stability, long time for humans to observe the same object, and machine vision can be a long time for measurement, analysis and recognition tasks.
With machine vision products and technology continues in the industrial application of technology, the concept of machine vision is no longer so strange as in previous years, people have gradually begun to accept machine vision inspection technology, and has been widely used.
Third, the factors affecting the screen printing overlay accuracy of
According to the actual printing, a lot of factors that affect print quality, such as: pre-press graphic information design process, the impact of the plate making, the impact of print registration, the sheet quality impact and ink color effects, and so on. This paper discusses the impact of print registration accuracy of the print quality.
Since the ink level to distinguish chromatograph squeegee for color when printing in general should be light-colored and India after dark, the first major Indian secondary India, the color sequence in the production of printing plates should be arranged.
From the printed overlay aspects to consider factors that affect the quality of screen printing, mainly summarized the following four points: ① operator influence; influence ② substrates and inks; ③ squeegee effect; ④ affect printing machine.
 According to the structure and movement pattern screen printing machine, the machine affect overlay accuracy is very significant. Especially the composition and movement of the machine. The printing machine is based on machine vision technology to complete.
Fourth, the working principle and the main work process
 according to the working characteristics of the screen printing machine, which uses machine vision technology to complete the take the image, a series of actions signal conversion table movement, etc., to achieve accurate overprint.
1. Works
The motion matrix to achieve a position of the image to move to another location. When the image deviation occurs, be the first to complete its rotation motion, and then realize its translation. As follows:
 pq assumed that the image moves to the end position by the p1q1 starting position, and it is known from the start position to the end position of the rigid body turned up θ angle. Since starting position set point turned around P1 θ angle, reach p1q ′ position, and then by p1q ′ position shifted to the end position pq.
. 2 main work process is based on machine vision technology
The main work on machine vision technology to detect multi-color screen printing overlay accuracy and control as follows:
① completion of the first color printing, at this step is not necessary register accuracy of detection and control.
② Image Acquisition in accordance with pre-set procedures and delays were issued for a start pulse to the camera and lighting systems.
③ signal under the control of a computer, to complete the image of the scan.
④ image information will be collected by the A /D digitizes either directly receiving digital video data digitized video camera, and the image acquisition part of the digital image stored in a processor or computer memory.
⑤ processor for image processing, analysis, identification, measurement results or logic control values.
⑥ results table motion control, image and achieve registration to correct errors and other sports.
Compared with traditional methods, not only has high accuracy, high speed, high degree of automation, visual inspection can overcome the traditional shortcomings easy to introduce human error, and improve the flexibility and automation of production.
Based on the above analysis, if the overlay error occurs in the printing process on the performance of CMYK four-color components are not precisely coincide, and in the 24 true color image captured by the CCD RGB three-component pattern is not precisely coincide. Therefore, based on our intelligent detection machine vision is the image and standard template image to be testing products are divided into R, G, B three sub-application template matching method to detect R, G, B three on the image to be detected coordinate template subgraph, if coordinate error R, G, B sub-graph between three templates is less than a certain threshold, we can see no overlay errors, otherwise it is considered that the overlay errors. Once the processing unit determines that there is the overlay error, then issue the corresponding control command execution device will correct it, so to achieve accurate overprint.
Overall, machine vision is a more complex system. However, due to the superiority of machine vision technology, more and more people use the technology. Not only can save manpower, but also can improve the accuracy, to meet the people's needs. Therefore, the application of machine vision systems more widely, not only in industry, agriculture, defense, transportation, medical, financial or sports, entertainment and so on have been widely used, but also screen-printing technology has also been very good applications, and can better control the printing process, thus improving the quality of printed products.