On the cause analysis and troubleshooting of die c

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Brief discussion on Cause Analysis and troubleshooting of bursting of die-cutting dark line

in the post press processing of paper packaging, die-cutting and indentation are an important process. It is to cut the substrate into a certain shape, press out trace or groove mark for bending on the die-cutting machine through the die-cutting plate lined up with steel knife and steel wire. The groove mark for bending is commonly known as dark line. The quality requirements for the dark line are appropriate width, clear and full, non burst, and good molding. Burst is a common quality problem, and its causes are various, some are intuitive, some are hidden. This paper tries to analyze it from the following aspects

improper pressure

1. There are foreign matters in the dark line of the bottom plate, which leads to a sharp increase in the pressure of the dark line is the common cause of burst, and it is also the most destructive cause. It often breaks the dark line as a whole, resulting in product scrap, but it is also intuitive, easy to judge and solve. As long as the foreign matters are cleaned up in time, the fault can be eliminated. In this regard, during the die-cutting process, it is necessary to ensure the cleanness of the base plate, avoid foreign matters from entering the die-cutting machine, and ensure that the pressing part works smoothly

2. Run the version, that is, the die-cutting version or the base plate moves. The steel wire is often pressed on the edge of the dark wire slot, causing a large area of dark wire burst, and mainly concentrated on the dark wire in the same direction. When this situation is found, it should be immediately re published, and the die-cutting version and the base plate should be locked

3. According to the requirements of the die-cutting process, different steel wires should be selected for different papers, as well as different thickness of the base plate and different width of the dark line slot. If they do not match, it is also easy to cause the dark line to burst. The following is a common calculation method for your reference

(1) die cutting paper jam

if a: bottom paper thickness, B: dark wire slot width, C: paper jam thickness, D: steel wire thickness, there should be:

d C

A C;

b= (C 1.5) +d

(2) die cut corrugated board

set a: the thickness of the bottom paper, B: the width of the dark groove, C: the thickness of the corrugated board (card mounting tile), D: the thickness of the steel wire, e: the thickness of the corrugated board after flattening, then there should be:

d E

A E;

b= (E 2) +d

generally speaking, under the condition of ensuring that the dark line does not burst, the dark line slot should be as narrow as possible, so that the dark line is full and easy to bend, and the product is well formed. Especially for pet paper, the dark line slot should be narrower than ordinary products if oil leakage is found, but the dark line slot is too narrow, which is easy to cause the dark line burst

improper surface treatment of printed products

1. The effect of embossing

embossing process is a new surface finishing process in recent years. It squeezes the paper through a patterned steel roller and a hard wool roller, and extrudes the required texture on the paper surface. Embossing technology was initially limited to greeting cards, desk calendars and the title page of books, and then gradually was widely used in paper packaging products. The use of embossing technology enhances the decorative effect of the product appearance, but it also brings certain negative effects to the post packaging processing. First, the large pressure (usually 3 ~ 8Mpa) during embossing is easy to cause certain deformation of the paper, resulting in concave convex pressing or inaccurate die cutting position; Second, it is easy to cause the dark line to burst. Due to the strong extrusion of the paper by the patterned steel roller and wool roller, the surface will be damaged to varying degrees, especially when the patterned roller has sharp lines, it will stab the paper surface. If the dark line is just pressed at the stabbing position during die cutting, it will burst when bending. To avoid such problems, first of all, when designing the pattern, we should avoid using very small points and thin lines, because they are very sharp on the pattern steel roller, which is easy to damage the paper surface and form bursting; Secondly, when embossing, the pressure should be moderate. If it is a sheet fed product, you can grind a wool roller more, so that the pattern can be completely copied on the wool roller, and the ideal effect can be achieved with less pressure; If it is a card mounting product, you can mount paper first and then emboss, because after mounting, the paper thickens and softens, the plasticity is improved, and it is easy to press out clear lines

2. Influence of oil polishing

after oil polishing of the paper surface, the varnish solidifies into a mirror on the paper surface, with minimal extensibility, and the indentation bending is easy to cause cracking. In this regard, you can make the paper softened by moisture or directly use the glue machine to water the back of the paper

improper selection of process and materials

1. influence of paper grain

in the papermaking process, the paper fibers will be arranged in a unified direction due to the oscillation of the equipment, which forms the directionality of the paper. This characteristic of the paper has a great impact on printing and post-processing. Practice has proved that during die cutting, if the indentation steel wire is perpendicular to the direction of the paper fiber, and the paper fiber is damaged radially, the dark line is easy to bend, the molding is good, and the angle is small; If the indentation steel wire replacement material will be used for heating and inkjet to allow the normal droplet creation to be parallel to the fiber direction of the paper, and the paper is not damaged laterally, the dark line is not easy to bend, formed into rounded corners, with a large angle, and it is easy to crack for the outer layer of the paper. This directionality of paper has little effect on the die cutting of sheet fed products. It is just that the forming is not good, but it is not easy to burst, but it has a great impact on the card mounting products. If it is not handled well, it is not only bad, but also easy to burst, mainly because the dark lines parallel to the paper grain burst at different positions, while the other direction does not burst. In order to avoid the occurrence of such problems, it is necessary to stipulate that the paper lines of the face paper and the lining should be mounted vertically and not in parallel when formulating the process. If they have occurred, they can only be made up by humidifying the paper and widening the dark line or increasing the arc of the steel knife

2. Problems in die-cutting plate making

die-cutting plate making is the basis of die-cutting work. If some crease positions are not handled properly, it will also lead to wire burst

for example, in the post-processing and finishing process of packaging, film covering is a relatively common process. The main material is biaxially oriented polypropylene film (BOPP), which has a very good tensile strength. The tensile strength in the vertical and horizontal directions is more than 130Mpa. Generally, it is not easy to burst, but if there is a small gap, it will easily burst from the gap. Therefore, when making die-cutting plates, if the die-cutting knife is damaged, Or there were burrs when the indentation line was cut in the first November of this year, that is, the BOPP film was damaged at the interface of the dark line or knife line. When the dark line was bent, the BOPP film could not be stressed, which would lead to bursting

in a word, the die cutting knife and die cutting line at the dark line should avoid knife edges and interfaces, and try to make an arc angle or a steel knife into one-time molding

3. material quality problems

material quality problems are also easy to cause dark line burst. For example, if the water content of the paper is too low and the paper becomes brittle, it is easy to cause dark line burst

to avoid bursting caused by material quality problems, paper with low surface strength, recycled paper and sandwich paper should be used selectively; For BOPP film, it is necessary to prevent sunlight exposure and long-term storage to avoid the decrease of tensile strength

the above only lists the common causes of paper dark line burst. In fact, there are other reasons, which require careful observation and careful thinking in actual operation, so as to eliminate the dark line burst fault well

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