Die-cutting waste discharge is not only the basic technology in the processing process of self-adhesive labels, but also a link with frequent problems, of which waste discharge fracture is a common phenomenon. Once the drain breaks occur, operators have to stop and rearrange the drain, resulting in lower production efficiency and higher raw material consumption. So what are the causes of waste discharge fracture in die-cutting of self-adhesive materials, and how to deal with it?
The tensile strength of raw materials is low
Some materials, such as light powder paper (also known as mirror coated paper), paper fiber is short, relatively fragile, in the process of die cutting waste, waste edge tensile strength is lower than the waste tension of the equipment, so it is easy to fracture. In such cases, the drain tension of the equipment needs to be minimized. If the discharge tension of the equipment has been adjusted to the minimum and still cannot solve the problem, then it is necessary to design the discharge edge wider in the early stage of the process design to ensure that the discharge edge will not frequently break in the die cuttingprocess.
Unreasonable process design or excessive waste edge
At present, many labels used for variable information printing on the market have easy tearing virtual knife line, some self-adhesive label processing enterprises are limited by the equipment, have to put the dotted knife and the border knife in the same die cutting station; In addition, due to cost and price factors, the waste edge design is very thin, usually only 1mm wide. This die cutting process has very high requirements for label materials, and a slight carelessness will lead to waste edge fracture, thus affecting production efficiency.
The author suggests that self-adhesive label processing enterprises, under the condition that conditions permit, try to separate the easy-to-tear virtual knife line from the label frame for die-cutting, which can not only reduce the frequency of waste edge fracture, but also greatly improve the die-cutting speed. Enterprises without conditions can solve this problem in the following ways. (1) Adjust the proportion of dotted knife. Generally speaking, the more dense the virtual cutting line is, the more likely it is to break the waste edge. Therefore, we can adjust the proportion of dotted knife, such as 2∶1 (cutting 2mm every 1mm), so that the probability of waste edge fracture will be greatly reduced. (2) Remove the part of virtual knife line beyond the label border. There are many die cutting version of the dotted line knife will be arranged longer, beyond the label frame, if the waste edge and narrow, then the dotted line knife will be very narrow waste edge and cut off part of the waste edge, resulting in waste edge easily broken. In this case, you can use a shaping file to file off the dotted knife that highlights the outer border of the label, which can greatly improve the strength of the waste edge, so that the waste edge is not easy to break.
Raw material tear
The tear of self-adhesive material is also easy to lead to the fracture of waste discharge edge, which is relatively easy to find and will not be described in this paper. It should be noted that the edge of some adhesive materials is small and not easy to find, which needs careful observation. In case of such problems, the bad material can be removed and then die cutting.
The amount of adhesive coating in adhesive material has a great influence on the die cutting performance of adhesive material. In general, on the die-cutting equipment, the die-cutting of self-adhesive materials is not immediately discharged, but to continue to transmit a distance forward, to the waste disposal station before starting to discharge. If the adhesive coating is too thick, in the transmission process from the die cutting station to the waste discharge station, the adhesive will backflow, resulting in the adhesive surface material that has been cut and stick together, resulting in the waste discharge edge when pulling up due to adhesion and fracture.
Generally speaking, the coating amount of water-soluble acrylic adhesive should be between 18 ~ 22g/m2, and the coating amount of hot melt adhesive should be between 15 ~ 18g/m2, more than this range of self-adhesive materials, the probability of waste edge fracture will greatly increase. Some adhesives even if the coating amount is not large, but because of its own strong liquidity, it is easy to lead to waste adhesion. In case of such problems, you can first observe whether there is a serious drawing phenomenon between the waste edge and the label. If the wire drawing phenomenon is serious, it is said that the gelatine adhesive coating amount is large or the fluidity is strong. It can be solved by coating some silicon oil additives on the die cutting knife, or by heating the electric heating rod. Silicone additives can effectively slow down the backflow rate of adhesive, and heating the adhesive material can make adhesive quickly become soft, so as to reduce the degree of wire drawing.
Die cutting tool defects
Die cutting knife defects are also easy to lead to waste edge fracture, for example, a small gap at the edge of the knife will lead to the adhesive surface material can not be completely cut off, the uncut part is relatively concentrated compared with other parts, it is easy to fracture. This phenomenon is relatively easy to judge because the location of the fracture is fixed. Encounter this kind of situation need to repair the damaged knife die first, and then used for die cutting.
Other questions and methods
In addition to replacing raw materials, there are many ways to solve the problem by changing the process Angle, such as oblique discharge, pre-stripping, direct row, heating, vacuum suction waste, dislocation method, etc. 1. Oblique waste discharge in die cutting special-shaped labels, die cutting modulus is too much, because the waste collection tension is not consistent, it is easy to take one side of the phenomenon of failure or fracture, then can adjust the Angle of waste guide roll to solve the problem of waste discharge fracture. 2. Pre-stripping In die-cutting of special-shaped labels and large paper labels, pre-stripping treatment can be done before die-cutting to reduce the stripping force of materials during waste discharge. After the pre-peeling treatment of the material, the peeling force can be reduced by 30%~50%, the specific peeling force reduction value depends on the material. It is worth noting that the effect of online pre-stripping is better. 3. Straight row method For waste discharge fracture caused by high weight and large die cutting modulus, the straight row method can be used to minimize the contact with the paper feeding guide roller before waste discharge, to prevent the label from sticking to the waste edge due to the overflow of glue due to tension extrusion. 4. When vacuum suction waste die cutting, part of the label is very large, and the suction nozzle can be used to suck out the waste edge for waste discharge, but attention should be paid to the stability of the suction, the size of the suction should be combined with the thickness of the material, the size of the waste edge, and the speed of the machine. This method can achieve non-stop waste discharge. 5. Dislocation paper material die cutting module is more, the width of the transverse diameter is small, the transverse diameter is easy to break or row when discharging waste, do the knife column and column staggered, can buffer the tension when the transverse diameter waste, but also can improve the service cycle of the knife die.
Post time: Mar-22-2022
