Packaging efficiency and product hygiene control, soft packaging products will be more and more roll film. At the same time, in the soft packaging production line, process semi-finished products are also in the form of volume.
However, it is rare to see a special discussion on the issue of rewinding. Here, in combination with the actual encountered some problems, about the issue of the volume.
Winding tension control mode
- Constant tension control mode
The tension remains constant throughout the process. When the tension set value is small, there will be unwinding; When the tension setting value is large, a large contraction force is formed after winding due to the residual tension of each layer of the film, leaving a transverse dent in the film surface, forming a “chrysanthemum petal” type winding end surface.
- Equal torque tension control mode
T = TR
T = T/R
The torque remains constant during the winding process. The tension does not decrease with the diameter of the film coil increasing. This is an improvement on the relatively constant tension control, but it is still not very good.
- Gradient tension control mode
The tension decreases with the increase of the diameter of the film coil.
TX=TS[1- (φX-φmin) / (φmax-φmin)KT];
Where TX is the winding tension when the winding diameter is X;
TS is the automatic tension setting value;
KT is the tension gradient set value (%);
φX is the current winding diameter;
φmin is the minimum winding diameter, that is, the paper core diameter;
φmax is the maximum winding diameter.
The setting of the gradient KT and the automatic tension setting value TS has a great influence on the winding effect. In the case of a certain TS, the setting of the gradient KT is too large, and the tension decreases too fast. On the contrary, if the gradient KT is set too small and the tension decreases too slowly, the residual tension existing in each layer of the film after winding will form a large contraction force, and eventually form a transverse dent in the film surface. The set value of gradient KT still needs to be studied. Some of our devices have gradient tension curves, so in practice, it’s important to figure out how to choose the appropriate gradient tension curve.
The performance of the retracement problem
- It is not easy to control when rewinding, which is manifested as incomplete rewinding and even small rewinding, resulting in the waste of materials, working hours and manpower.
Although this problem is serious but can be found immediately, basically within the scope of the correction, it is generally not a great loss of a class of problems.
- Problems that can only be found after the process.
In general, the pre-process production of automatic packaging cursor spacing within the control range. However, after a certain amount of time under certain conditions, the cursor spacing exception is automatically wrapped.
For example, BOPP/INK/PE structure of products, composite of the machine detection, automatic packaging cursor spacing within the control range; However, after a certain period of maturation, the cursor spacing was found to be seriously out of tolerance during slitting.
In addition, liquid milk automatically packaged PE roll film, cutting found that the surface of the roll and close to the core of the cursor spacing difference, and even the core of the cursor spacing error.
Both of these problems are more serious because by the time they’re discovered, the die is cast and they’re probably all junk.
What’s worse, when the reason cannot be found, it is very likely that many people are considered to be not serious work, by the unexplainable punishment, that is, the uncontrollability of the way in the control of the volume.
From the perspective of operation, we found that the larger the volume diameter, the more significant the difference between the cursor spacing at the outermost and near the core of the volume.
We should pay attention to which products we want to carry out the research on the maximum winding diameter of the corresponding equipment and what kind of winding equipment these products should choose.
Winding tension control mode
- Lack of strong technical support in the production and operation of flexible packaging.
If the operator is not clear about the related material winding tension control factors, it can only explore, which will lead to the winding quality is difficult to have a stable performance.
Due to the lack of theoretical guidance, standardized operation (SOP) documents cannot be formed. As a result, the winding quality of products fails or the stability is poor, and the production efficiency is difficult to breakthrough.
- In terms of soft packaging management, there is a lack of systematic technical support for volume collection. Generally speaking, a product often corresponds to multiple materials and multiple machines.
At present, many manufacturers are trying to process through general equipment, if the flexible packaging production management team does not have the system of winding up technology, that is, do not know the winding-up technology and equipment winding up characteristics, then it will be difficult to make the winding-up controllable, may have to pay a certain “tuition”.
Suggestions on volume collection problem control
- The learning and training of roll theory should be able to follow the introduction of new equipment.
- For the development of some new products, it shall include the study of roll quality control and the formation of corresponding SOP documents.
- Operators should have daily inspection and maintenance of the equipment to minimize the probability of hardware and software abnormalities, at least not to cause waste of semi-finished products, the cost of materials is now recognized to be relatively large.