As the market gradually recognizes the individualization of product packaging, various box types with corporate symbolism have also become a symbol and culture of the company. In the mass production process of box type, die cutting is an indispensable processing method. For the entire die-cutting process, the control of die-cutting pressure is a core part of product quality control. Excessive die-cutting pressure will cause damage to the die-cutting plate. Too little pressure will cause poor separation of the cassette pieces.
Because the die-cutting pressure of the die-cutting machine is greatly affected by the physical properties of the pressure-bearing material and the performance of different die-cutting plates, the initial adjustment pressure is difficult to determine. There are three main pressure transmission methods for the flat-press horizontal and horizontal die-cutting machine, namely four sets of crank connecting rod mechanism, cam block cam mechanism and worm gear eccentric mechanism. No matter what kind of transmission method is used to provide die cutting pressure, the final pressure must be transmitted and realized by the steel knife and steel wire on the die cutting plate, that is, the die cutting pressure is converted into the linear pressure of the steel knife and steel wire. In the operation of the die cutting machine, the most important thing is to control the die cutting pressure, but for different processing materials and box types, how can the die cutting pressure be set quickly and accurately?
1 Theoretical calculation
After the die-cutting pressure is converted to linear pressure, the pressure value is related to the total length of the steel knife and steel wire, the effective linear pressure and the characteristics of the pressure-bearing material. The current general calculation formula is:
P = K × L × F
P-die cutting pressure (N)
K-correction factor (generally 1.3)
The total length of the steel knife or steel wire on the L-die cutting plate (mm)
F-effective linear pressure of steel knife or steel wire (N / mm)
However, in actual production, due to the difference in material and environment, the physical parameters such as the tightness, thickness, fiber direction, etc. of the material are different, and the die cutting pressure will change. In addition, due to changes in processing conditions, steel knives and wires The wear caused the effective linear pressure of the steel knife and steel wire to change, and in the calculation, the steel knife and the steel wire always work under the state of the best effective linear pressure value, which causes the error of the theoretical calculation value. In addition, due to the incomplete level of the die-cutting plate in the manufacturing process of the die-cutting plate, the difference in the installation height of the steel knife and the steel wire caused by the error in the processing accuracy of the bridge height reduces the actual performance of the formula. Therefore, this formula cannot be used to determine the pressure of all die-cutting plates.
However, the formula still has a very important guiding significance for the processing process of new production tasks, which plays the role of saving printed sheets and protecting die-cut plates. The maximum practical value of the formula lies in the determination of the reasonable range of the initial pressure. Before the new die-cut version is used, the reasonable theoretical pressure value that the die-cut version can withstand for the first time can be calculated according to the parameter values ​​required by the formula, rather than Reasonable actual pressure value of die-cut version. It can be seen from the formula that the calculation of die-cutting pressure and the pressure-bearing body are mainly balanced by the correction factor, but using the same correction factor every time will cause the difference caused by the change of the pressure-bearing material.
2 Trial cutting method
In addition to the calculation method, the trial cutting method is also a convenient method to determine the die cutting pressure. It actually uses an experimental process to determine a box-shaped die cutting pressure. This method is very helpful for determining the pressure of the first processed product. With the operator's experience, the trial cutting method estimates the die cutting pressure of new processed products. After finding a reference, gradually increase the die cutting pressure accordingly until 2/3 of the die cutting line of the die cutting sample is cut off. This process This is called the initial pressure. After the initial pressure value is determined, the pressure can be increased from 3 to 5t according to the characteristics of the pressure-bearing material. After 90% of the steel knife and steel wire are normally die-cut, the pressure is increased from 0.1 to 0.3t until the die is cut The box type can be separated normally. This process is called squeezing.
This method is time-consuming and labor-intensive, and has high requirements on the operator. If the initial pressure is too large, it is easy to cause damage to the die-cutting plate. If the pressure is too low, it needs repeated tests to reach the rated value, thereby reducing production efficiency. . But once a reasonable pressure value is obtained, this value has a very important reference value for future reprocessing, and it should be recorded one by one for future use. However, as the degree of wear of the die-cutting plate is different, the effective linear pressure has changed, resulting in the change of the actual die-cutting pressure value. Usually, the actual die-cutting pressure marked must be constantly revised to meet future applications.
Some people think that the calculation method can't be close to production at all, and it has almost become a "chicken rib" that is a pity for food. At present, the factory also generally adopts trial cutting method to obtain reasonable pressure value of new products. If the two are used together, it will bring certain economic benefits to actual production.
3 Comprehensive method
The calculation method can obtain the theoretical pressure value of the first pressure, and the trial cutting method can obtain the actual pressure value. If the reasonable actual value obtained by the trial cutting method can be used to reverse the correction coefficient in the calculation method, then this type of die-cut version can be obtained The correction factor for this type of material. The correction coefficient is a variable value, which is mainly used to make up for the difference between different materials and the error between the processing accuracy of the die cutting plate. The correction coefficient of the material can be more accurately determined by the actual production data of the same material In this way, you can know how much pressure should be used for the first time when the new product is die-cutting, which can be closer to the reasonable actual pressure value.
The test method is as follows: Assuming the first die-cutting of white cardboard with a grammage of 300g / m2, it is known that the total length of the steel knife on the die-cutting plate is 1600cm, the total length of the steel wire is 1810cm, and the effective line pressure of the steel knife used is 45N / mm, the effective linear pressure of the steel wire is 40N / mm.
How to determine the die-cutting pressure value required for the use of white cardboard die-cut products with a grammage of 300g / m2?
First of all, the theoretical reasonable pressure value of the product is die-cut by calculation method. It is 187.72t, and then the die-cutting method is used to set the initial pressure to 60% of the theoretical value, and the actual pressure value is 174.8t by continuous pressure , The pressure value is brought into the formula again to obtain a K value of 1.2. Therefore, in the die cutting of this kind of material, K = 1.2 can be used to substitute the formula to calculate the corresponding accurate pressure value, which avoids the risk of trial cutting method and saves the production cost. The closest correction factor can be obtained by establishing a test table of different products of the same material to obtain the ideal actual die-cutting pressure for the next new product.
Of course, this method cannot provide the same standard for all equipment, because the correction factor also includes the processing error of the equipment, and the wear of different equipment is different. Therefore, the above tests can only be performed on the same machine, it is best to take the average of multiple sets of actual data to find the correction factor of the material. The establishment of correction factors for different processed materials is of great help in processing new products. It can accurately determine the pressure required for die cutting, saving a lot of materials and time. In addition, due to the wear of the equipment, the correction coefficient will change, and the effective service life of the die-cutting equipment is long, and its wear is relatively slow. Under normal use, the correction factor can be measured again in two-year cycles. If the equipment is used intensively, the measurement cycle can be shortened.
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