Printing precision process and method for influencing pharmaceutical aluminum foil color registration

First, the aluminum foil overprint error correction steps and methods

When printing, the operator constantly observes the accuracy of the alignment. For example, when the overprint is started, the color mark is not in the specified position. The actual printed color mark deviates from the center of the two lines of the blank color mark size, but is defined as a positive error by the square of the initial color mark. If the actual printout, The deviation of the color mark from the center of the two lines of the space mark away from the start color mark is defined as a negative error. This type of overprint error can be adjusted in different directions. When the overprinting positive error occurs, the correction method is as follows: the path of the substrate aluminum foil can be shortened, or the printing plate roller can be rotated by a certain angle against the running direction, so that the color mark printing point retreats, so that the centerline of the space is relatively On the "advanced", the color standard is overprinted on the centerline. The correction method when overprinting negative error occurs: take the stroke of the aluminum foil or rotate the printing plate along the running direction by a certain angle, so that the printed point of the color mark advances, and the centerline of the blank space relatively “retreats” "" And make the color mark printed on the center line of the location of death - the multi-color printing operation of the foil on the substrate should be preceded by the actual adjustment of overprinting computer photoelectric scanning head, the photoelectric scanning head is aligned with the reflector, adjust the distance, make The light spot on the reflection plate is the smallest, and the detection distance at this time is approximately equal to the focal length of the photoelectric scanning head, and the photoelectric scanning head is moved left and right so that the light spot hits the center of the color mark. When the brightness of the color patch is higher than the brightness of the background color, the bright-pass and dark-switch boards of the photoelectric scanning head are darkened. Then align the light spot to the color mark, adjust the multi-turn potentiometer until the status light on the computer is bright, then turn the light spot to the background color, turn the multi-turn potentiometer to the dark direction, and record the number of turns. Until the status indicator on the computer lights up. Reverse the multi-turn potentiometer back to half the number of grids, to this photoelectric head debugging completed. In the running phase of overprinting aluminum foil, manual overprinting should be carried out at the lowest possible printing line speed so that each overprinting color mark is entered into its own corresponding overprinting space. The maximum allowable overprinting error detection range is ±8 mm, which can be closer to the center of the overprinting space. it is good. After manual overprinting, increase the printing line speed to about 30 meters/minute, wait until the "line speed" and "overprinting error" displays on the control panel of the computer, you can switch to "automatic" control. When the automatic overprint is normal, the printing speed of the printing press can be gradually increased until the expected working line speed.

Second, the key factors affect the precision of overprinting aluminum foil overlay

1. Impact of tension changes during the overprinting process: In the foil overprinting process, adjustments and changes in equipment tension directly affect the accuracy of overprinting and printing. As long as the tension control is stable and the change in running tension is small, the accuracy of foil overprinting and the scrap rate can be easily controlled. To ensure the accuracy of the overprinting of aluminum foil, firstly, a complete tension control system is equipped in the printing press. However, the factors influencing the tension fluctuation and the change in the aluminum foil printing are also various, and operators need to constantly summarize and strive to grasp and properly control and adjust. . The following points should be noted: First, since the diameter of the printing machine's roll is continuously changing during the winding and unwinding process, the change in diameter will inevitably cause changes in the tension of the aluminum foil when the unwinding is unchanged at the braking torque. In the case where the diameter decreases, the tension will increase, and the winding will be the opposite. If the winding torque is constant, the tension will decrease as the winding diameter increases. This is the main factor that causes the overprinting tension of aluminum foil to change. Second, due to the non-uniformity of the aluminum foil used, it also affects the change in tension during printing. If the elastic modulus of the material fluctuates, the thickness of the material varies along the width and the length, and the quality of the roll may not be the same. The fluctuation of the tension of the printing press during the operation brings about large or small influence. Thirdly, when the printing press is in the process of operation, the material is broken, and the occurrence of splice will cause the original stable tension to suddenly occur in the disturbance change. The higher the printing speed of the equipment is, the greater the interference will be. At this time, the tension control system should It can automatically and randomly adjust according to the size of the disturbance of the tension of the coil, and restore the tension to the original stable state in time.

2. The influence of the manufacturing precision of the printing plate roller: the pitch of the roller of the printing roller and the coaxiality, the accuracy of the taper size of the roller inside and the taper hole. The roller beating of the roller affects the accuracy of the overprinting of the aluminum foil. If the error of the roller of the roller is large, the tension of the overprinting of the aluminum foil will change irregularly, and the length of the entire printing path will be changed in different degrees, resulting in overprinting. Not allowed.

3. The installation accuracy of the plate roller affects: Before the platen roller is overprinted, it is necessary to ensure that the taper holes at the two ends of the printing plate roller and the fixed platen cone head are clean, and ink or other impurities cannot be adhered, otherwise the assembly accuracy will be affected. Plate cylinder assembly standards to achieve the first plate on both sides of the plug and plate axis assembly concentricity, to install a good positioning, assembly should be tightened, after assembly is completed, the plate radial runout should be controlled within 0.1mm. Use a graduated table or a radial runout to check whether there is a radial runout of the plate. The second printing plate shall control the color sequence of the overprint given in the printing platen in turn into the printing machine shaft seat. The printing plate rotation direction shall be consistent with the direction of the ruled line arrow in the color code, the color of the first color printing plate roller. The mark should be conveyed in front of the other printing plate roll marks, and it cannot be installed in the wrong direction.

4. The influence of the precision of the guide roller of the printing machine: The aluminum foil printing press adopts more guide rollers and conveying rollers to locate and convey the aluminum foil, ensuring the normal operation of the aluminum foil. If the precision of the guide roller is poor, it may cause irregular changes in the tension of the aluminum foil. Therefore, overprinting is not allowed. This is mainly the operation of the machine for a long time, coupled with the guide roller in the heating oven, resulting in the loosening of the guide roller, the lack of oil in the deformation bearing and the increase of the running resistance, thereby changing the change of the printing path length or the tension between the guide rollers. , and affect the accuracy of overprinting.

5. Impact of printing ink properties: The color of the printing ink affects the sensitivity of the scanning spot in the automatic register tracking system. The color of the overlay mark is different, and the intensity of the light reflected by the photoelectric scanner is different, and the corresponding pulse degree is also different. The darkness of the ink is the peak of the pulse, and the lightness of the ink is the small peak of the pulse. In addition the ink also need to ensure a certain concentration, can not be too thin, so as not to easily form a "tail" phenomenon, and the installation angle of the squeegee should be correct, the squeegee pressure should be moderate, to ensure the printing of wireless products, the appropriate ink viscosity, The printed color mark should be correct, clear and full of color.

6. The effect of aluminum foil material change: due to the uneven thickness of the material often encountered in the printing, this will cause the tension to change unpredictably, which will affect the accuracy of the registration to a certain extent. At this time, the printing press should be required to operate as smoothly as possible, and cannot be fast or slow. Aluminum foil should be given moderate tension during the printing operation. If the tension is too small, the substrate at the printing and measuring position will be prone to jitter. At this time, the tension in the aluminum foil operation should be constant to ensure the instantaneous linear speed is constant.