Laser film is becoming more and more the material of choice for cigarette packets, medicine packets and food packaging due to its beautiful appearance and high grade. New technologies developed and new equipment developed due to it are emerging one after another. These new technologies have brought a technological revolution to the entire laser film industry. E.g:

1. Wet composite-peel-gravure-indentation die-cutting (or cut large sheets) of the line;
2. Unwinding laser film plate seam positioning stitching technology to ensure the continuous production of gravure printing machine;
3. On-line detection and automatic control technology of on-line distance;
4. No plate seam molding machine, eliminating plate seam will completely change.

This article will analyze the reasons for the large fluctuations in the laser film layout on the market and propose solutions. Other new technologies on laser films will be discussed later.

1. Current status of laser film:

What is the fluctuation range of the conventional laser molding machine? Through the on-line detection system for plate distance, we found that the laser film produced by a regular press has a fluctuation between each adjacent plate distance of ± 0.3mm, and most will reach ± ​​0.5mm, with a fluctuation range of 1mm; adjacent The fluctuations of the two layouts will show discontinuous changes, and the amplitude will also reach ± ​​0.5mm. Within a roll, due to changes in speed, etc., the change in layout distance will reach 1mm, 2mm.

For inline printing, ± 0.5mm is too large. In such a large fluctuation of plate distance, the plate length stretching unit of the wet composite unit cannot reliably adjust the plate length after transfer to meet the requirements of gravure printing, so The gravure unit will add a lot of printing waste. The issue of stable version distance has been around for eight years since Shenzhen Jinjia Group raised the issue of stable version distance. Each laser film production enterprise has invested a lot of manpower and material resources to improve the accuracy of layout control. From the perspective of the current effect of each manufacturer, it has improved, but there is still a certain gap from the ideal state.

2. What are the factors that affect the stability of plate spacing?

◆ Determined by the production process. During the production of the laser molding machine, the PET material is pressed at a temperature of 170 ° Celsius. The PET is deformed by heating at high temperature and stretched. It is immediately cooled and set at 20 ° Celsius. The PET is rapidly cooled and contracted violently. Acting on the material, this is how the layout distance changes.

â—† The stability of tension. If the front traction tension is larger, the plate distance will be shortened, and if the rear traction tension is larger, the plate distance will be longer. The fluctuation of tension will directly affect the fluctuation of plate distance.

◆ Speed ​​stability of drive system. When the speed is unstable, it will directly cause the fluctuation of the tension, which will affect the fluctuation of the plate distance.

◆ The uniformity of thickness of PET material is ± 2%. The uniformity of thickness and thickness of different materials are different.

â—† The stability of plate roller temperature and the consistency of left and right temperature.

â—† The stability of the cooling roller and the consistency of the left and right temperatures.

â—† Manufacturing accuracy of the whole equipment.

â—† Whether the equipment structure is suitable for the production of laser film with stable plate distance. [next]

Third, the solution:

1. Speed ​​control:

The servo drive control system is used in the drive: we use professional optimization software to make the position and speed of the drive more compatible, so that the servo drive achieves better dynamic response and anti-interference characteristics. Make the machine speed more stable.

2. Tension control:

In programming: After optimizing the hardware scheme, the most critical technology is the control arithmetic algorithm. The differential division method and the differential superposition method are used in the control algorithm, so that the control accuracy of the system in the work is reliably guaranteed.

3. According to the mechanical transmission characteristics, various compensation algorithms to overcome mechanical resistance should be added.

4. Equipment structure design: Taking the stability of plate distance as the first point of design, redesigning the equipment: the common form of laser molding machine and the plate molding machine are essentially different in mechanical structure. The mold press of the form distance automatic control has six levels of tension control, and the ordinary mold press has four levels of tension.

5. Manufacturing accuracy and assembly accuracy: The machining center processes the main components, and improving the manufacturing accuracy and assembly accuracy of the machine itself is the main means to solve the large fluctuations in plate spacing. For example: the best gravure printing machine abroad has a printing speed of 800m / min. Our country is still climbing the peak of printing speed of 300m / min. The domestic equipment is fast, the frame shakes, the lateral color deviation is large, and the ink is flying. , Serious mechanical wear and tear, bearing fragility, etc., these are caused by insufficient manufacturing accuracy and assembly accuracy, and the automatic electrical control system to achieve 600m / min is no problem. The manufacturing accuracy and assembly accuracy of mechanical equipment are the most basic basic technologies. The higher the manufacturing accuracy of the equipment, the better the stability and the better the stability of the electrical control.

6. Adopt double electric eye type absolute distance detection, reliable and accurate, and can automatically eliminate interference signals to ensure the accuracy of detection. The detection system is like the eyes of the operator. You can see the size of the plate distance at any time, understand the molding status, from manual detection after the original production to online automatic detection during production, which reduces the scrap rate and improves production efficiency.

7. Plate distance closed-loop automatic control: online real-time detection of plate distance status, and real-time feedback control to achieve automatic plate distance control. Numerous factors can cause fluctuations in plate distance, and the real-time plate distance closed-loop control system minimizes the rejection rate of products. Plate distance closed-loop control technology is a technology that can be applied only when the plate distance detection technology is mature. It is a relatively complicated control technology, that is, a three-stage closed-loop control system of speed closed-loop control, tension closed-loop control and pitch closed-loop control. They are mutually independent and interrelated. The interaction and mutual influence must be stable and stable The control system needs excellent electronic control technology to guarantee.

8. The application of electronic shaft transmission technology will greatly improve the transmission accuracy and control accuracy, and is expected to improve the control accuracy of the plate distance to within ± 0.1mm. Electronic shaft transmission technology first originated in Europe in the 1990s. In the packaging and printing industry, in 1994, the world's first shaftless transmission technology was applied to newspaper and printing presses. With the rapid development and maturity of modern electronic technology, optical fiber communication technology and transmission control technology, this technology has begun to be applied in the Chinese market for high-end mechanical equipment.

Electronic shaft transmission is also called "shaftless transmission". It is controlled by the motion controller through bus communication to control the rotation speed, position and torque of the servo motor. A large number of transmission shafts and gears are omitted in mechanical equipment; it is applied to equipment driven by multiple motors and multiple stations, and uses the virtual main shaft to transmit power. The motors at each station follow the same phase angle or the same speed or The transmission technology of the motion specified by the process in a special synchronous way.

The application of electronic shaft drive technology will bring revolutionary progress to the entire production process and quality of laser film. Similarly, the application of electronic shaft transmission technology has begun to create extraordinary value for the packaging and printing industry, and this technology will be applied in a wider range of fields in a very long time in the future.

Conclusion: Through the above work, we are gratified to see that the precision of the layout control has been greatly improved, and the overall layout stability trend is within ± 0.15mm. In the production process, when the fluctuation of the plate gap is caused by various factors, the automatic plate gap control system will adjust in real time and quickly control the plate gap within the specified range.

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