Plastic color printing trademark bending analysis

The printing industry in the modern printing industry develops from monochrome to six-color and eight-color. The efficiency has evolved from multi-process to one-step molding, integrating printing, cutting, embossing, bronzing, and laser. In the process of mechatronics, a series of new problems will inevitably arise in production. Trademark bending is a quality problem often encountered in the production of one-shot molding. Trademark bending not only affects the appearance of the trademark, but also directly impairs the user's applicability to the computer, causing users to discontinue their use of the trademark. How to effectively solve and control the occurrence of trademark bending in production is of great significance to improving product quality and satisfying users' needs.

Why does the film bend in the printing process?

From the test, it is known that under a certain pressure and temperature conditions, the greater the tensile force, the higher the temperature, the greater the deformation of the film.

In the process of one-step molding of a gravure multi-color machine, the film is subjected to 20 to 35 daN tension, 25 to 40 daN pressure, and a drying temperature of 60 to 100°C. After many times of printing, drying, stretching and recovery, the film is deformed to varying degrees. Moreover, in printing, due to the application of ink, it will cause local and lateral double-sided stretching, deformation, and recovery of the film on the lateral width of the film, resulting in trademark bending phenomenon in the finished product, especially poor quality of the tension. The film will be severely bent.

For the bending phenomenon in the production of trademarks, the following measures can be taken:

(a) film control

In order to reduce the bending of the trademark, in selecting the brand of printing film, it is necessary to reasonably select the famous brand with high technical content, which can ensure the reliability of the PP resin, the reliable control of the thickness and thinness of the film, and the uniform slitting and rewinding tension. Ensure that the surface condition and tension of the film are balanced, which is beneficial to printing and avoiding bending.

(b) Control of inks and solvents

In the printing process, since the ink is applied to one side of the film, the ink, resin, trademark pattern, and solvent are volatilized, which has different degrees of influence on the bending of the trademark. Under the premise of guaranteeing the pattern and color to meet the needs of users, the ink's origin, applied thickness, and choice of solvent should be compared. The ink must be selected for its strong solubility, good performance, and low susceptibility to sizing. The thickness is in the platemaking process according to product requirements. Net depth is generally not more than 35μm; the use of solvents must maintain a balanced mixture of solvents, that is not too volatile, but also at a certain temperature (usually does not exceed 80 °C), so that the product does not stick.

(III) Coordination of speed and pulling force

Under the condition that the pulling force is certain during the printing process, the higher the printing speed, the greater the degree of bending of the trademark; conversely, the printing speed is constant, the greater the pulling force, the greater the bending of the trademark. In the production of equipment to play the efficiency, can not reduce the speed to solve the problem of trademark bending, which must be a reasonable choice of tension parameters to solve quality problems. For example, in the running speed of 130m/min, tension before tension of 20daN, rear tension of 35daN is an ideal parameter, as for the choice of actual parameters, can be adjusted according to the printing effect.

(4) Influence of drying temperature and air volume

The higher the temperature inside the drying oven, there are certain benefits to the printing process, but the temperature is too high, the trademark bending phenomenon will occur, therefore, for the level of printing generally stable temperature at 55 ~ 90 °C. Dryer inlet pressure and exhaust pressure must be balanced. If the air volume is too large, the shrinkage of the film is large and the trademark is severely curved.

(5) The effect of ink, printing patterns, and solvents on the bending of the trademark (as listed in the following table)

Bending degree Varnish Printing area Solvent large Domestic Full version Volatile fast-moving Domestic famous brand Strip Volatile medium and small Import Irregular Slow evaporation