Discussion on the indentation molding technology o

2022-08-22
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Discussion on the indentation molding process of cigarette hard box packaging II

v. the relationship between paper and trace line

processing and production of highly accurate foldable and flexible cigarette boxes, in addition to equipment and technology, there are also factors of paperboard raw materials. Because paperboard is a non unitary material, it has its own internal differences, especially those with different internal structures. Therefore, we must distinguish and adjust them in the process of mold design and production

1. Influence of different papers on indentation effect

at present, the paper we use is basically divided into two categories, one is 230g white cardboard made of chemical pulp represented by internationalpa per and Westvaco, and the other is 215g white cardboard (sandwich paper) made of chemical pulp and mechanical pulp represented by Finnish forestry. Although these two kinds of white cardboard are more suitable for cigarette packaging, there are great differences in the physical properties of their internal fibers. American white cardboard is all chemical pulp (the physical properties of paper fibers are changed by high-temperature cooking, which makes the fibers soft). Therefore, in order to achieve stiffness, by increasing the weight of paper, the weight of paper with the same thickness in the United States, even in the automotive interior, is larger than that of Finnish paper. Finnish paper has a three-layer fiber structure. The upper and lower layers are chemical pulp, and the middle layer is mechanical pulp (that is, what we call sandwich paper). Because the mechanical pulp fibers are hard, there is a gap between each layer of fibers, and the cross-sectional fiber structure of the paper is like corrugated paper. Therefore, when pressing the indentation line, if the same pressure is applied, although the indentation line of American paper is full in shape, the rebound coefficient is large. In order to obtain good molding effect, the depth (or height) of the indentation line must be deepened. Finnish paper is easy to be pressed because of its high stiffness and weight due to the gap in the middle. The plumpness of the indentation line is inferior, and the depth of the indentation line is shallow (or low in height), but its rebound force is small. In his opinion, the front of the small box is smoother and has a better molding effect

2. The influence of the arrangement direction of paper fibers on the indentation effect

paper is usually made of plant fibers soaked in water on a thin sheet. In the process of papermaking, a large number of fibers will form the same arrangement as the running direction of the machine. When the indentation direction is parallel to the direction of the paper fiber, we call it along strand (MD), and when the indentation direction is perpendicular to the paper fiber, we call it straight strand (CD). Therefore, the force required for indentation in the direction of CD is greater than that in the direction of MD during indentation, and CD is greater than MD when designing the width of indentation groove. The rebound coefficient of CD direction trace is 20% higher than that of MD direction trace under the condition of constant groove width and pressure. Therefore, when designing the indentation line, the arrangement direction of paper fibers must be considered to determine the indentation pressure

from the above discussion, it can be seen that indentation is the key to the formation of hard box cigarette packaging. In order to obtain an ideal indentation line that is easy to pack, and ensure that the common interbody fusion devices in China are mainly titanium fusion devices and peek fusion devices, the appearance quality standards of cigarette packaging must exclude many factors such as molds and paper that affect the quality of the indentation line in mold design, manufacturing and pressure adjustment, so that the pressed indentation line is neither broken nor easy to fold, and is suitable for the production of high-speed packaging

effect of controlling the deformation or fracture of indentation

the mechanics of indentation is that when the die-cutting die presses the paperboard into the groove, the paperboard receives two kinds of forces, namely, internal fracture and the increase of surface tension. All we have to do is how to control these two forces

according to the feedback on the packaging quality of the flip hard box cigarette label produced by our previous bobst820 unit (flat pressing and die cutting), there are quality defects such as small box irregularity and "double eyelid". Mold configuration: German Marbach sandwich upper mold, steel wire specifications: 23.80mm (height) × 0.71mm (top thickness) and 23.85mm × 0.71, the lower mold adopts the steel female mold, and the width of the trace slot is 1.2mm or 1.4mm respectively. The same slot width is used in the CD direction and MD direction, and the paper thickness is

0.3mm. At this time, the distance of a is 0.585mm

calculation formula: a= (H-E) ÷ 2

(a-slot width b-copper wire e-thickness)

when indentation is performed, the top of the steel wire is on the same plane as the female die steel plate, and the pressure to form the trace line mainly comes from the thickness of the paper. Sometimes, in order to achieve better molding effect, 23.85 copper is even used as the glass fiber supplier wire. Although the top of the steel wire is 0.05mm deep into the slot, because the paper fiber is not damaged, the average rebound force of the indentation line reaches more than 85 grams, and some even reach more than 95 grams, which makes it unable to meet the quality requirements of cigarette packaging

according to experience and a large number of tests, it is considered that in MD direction, because the indentation line is parallel to the paper fiber paper, the paper stiffness is relatively low, the pressure required for indentation is small, and the groove width (b) 1mm ~ 1.1mm is more appropriate. The indentation line in the CD direction is perpendicular to the paper fiber direction, and the paper stiffness is high. In order to basically keep consistent with the rebound force in the MD direction, the indentation needs more pressure, and the groove width (b) should be increased to 1.1mm ~ 1.2mm. When the distance a reaches 0.2mm ~ 0.28mm, the internal fibers of the paper are destroyed and broken, and the rebound force of the indentation line drops below 75g, which fully meets the requirements of cigarette packaging

design of cutting indentation

in order to obtain excellent marking lines, the following factors must be considered: ① paper type; ② Paper thickness; ③ Steel wire height; ④ Bottom groove width; ⑤ Thickness of steel wire top; ⑥ Paper thread to design mold

it can be seen that only excellent and scratched indentation lines can ensure the best molding of cigarette packaging. Through the research on the marking line, the adverse factors affecting the quality of the marking line are continuously eliminated, and cigarette labels that meet the requirements of high-speed cigarette packaging machines and adapt to the image of China's first-class cigarette products are produced

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