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The packaging machine is divided into vertical type and horizontal type, and vertical type is divided into continuous type (also called roller type) and intermittent type (also called palm type). The bag has three-side seal, four-side seal, back seal, and one out Multi-column packaging equipment. There are many types of packaging equipment, and the differences between the equipment are also very large. In the actual use of composite film rolls, you will encounter various problems. This article analyzes the causes of six common problems in detail for reference.
First, the cursor problem
In the automatic packaging process of the composite film roll material, positioning heat sealing and positioning cutting are often required, and an electric eye cursor needs to be set for positioning. There are certain differences in the size of the cursor and different packaging opportunities. Generally, the width of the cursor is greater than 2mm and the length is greater than 5mm. The cursor is generally selected to have a dark color with a large contrast to the background color, preferably black, and generally cannot use red and yellow as the cursor, nor can it use the color code of the same color as the photoelectric eye as the cursor color, such as the photoelectric eye glows green Light, you cannot use the light green color as the cursor color of the electric eye, because the green photoelectric eye cannot recognize the green color. If the background color is a darker color (such as black, dark blue, dark purple, etc.), then the cursor should be designed as a hollow light-colored cursor.
The electric eye system of a general automatic packaging machine is a simple identification system and cannot have the function of intelligent fixed length like a bag making machine. Therefore, in the longitudinal range of the electric eye cursor, the roll film is not allowed to have any interfering characters and patterns, otherwise it will cause Identify the error. Of course, for some electric eyes with higher sensitivity, the black and white balance can be adjusted precisely. Some light interference signals can be removed by adjustment, but pattern interference signals with colors similar to the cursor or darker colors cannot be removed.
The spacing between the cursors is used to set the length, so the error between the actual spacing and the design value should not be too large, generally only 0.5mm error is allowed. For many automatic packaging equipment, the tracking effect of negative deviation is better than positive deviation, so it is recommended to design for negative deviation.
Aluminized or pure aluminum has a strong specular reflection, which will affect the identification of the electric eye. It is recommended that its composite film cursor be printed on a white background. For the transparent composite film, it is also recommended that the cursor be printed on a white background due to the color of the items in contact with it, thereby reducing interference.
Second, the friction coefficient
The frictional force in the packaging process is often both the drag force and the resistance, so its size should be controlled within an appropriate range. The coil material for automatic packaging generally requires a smaller inner friction coefficient and a suitable outer friction coefficient. If the outer friction coefficient is too large, it will cause excessive resistance during the packaging process, causing tensile deformation of the material. If it is too small, it may be It will also cause the drag mechanism to slip, resulting in inaccurate tracking and positioning of the electric eye. However, the inner friction coefficient of the inner layer can not be too small, and some packaging machines with too low inner friction coefficient will cause unstable stacking and wrong edges during bag forming; for the composite film for strip packaging, the inner friction coefficient Too small may also cause the tablet or capsule of the blank to slip, resulting in inaccurate positioning of the blank. The friction coefficient of the inner layer of the composite film mainly depends on the content of the opening agent and the slip agent of the inner layer material and the stiffness and smoothness of the film. The corona treatment surface, curing temperature and time in the production process will also affect the product Coefficient of friction. When studying the coefficient of friction, special attention should be paid to the fact that temperature has a great influence on the coefficient of friction. Therefore, not only the friction coefficient of the packaging material at normal temperature should be measured, but also the coefficient of friction at the actual use environment temperature should be investigated.
3. Heat sealing problem
The low temperature heat sealability is mainly determined by the performance of the heat seal layer resin, and it is also related to the pressure. Generally, the extrusion temperature is higher when extruding and compounding. If the corona treatment is too strong or the film is left for a long time, the low temperature heat of the material will be reduced.å° æ€§ã€‚ Sealing performance. Thermal viscosity is used to describe the strength of the heat-sealed layer's molten surface to resist external force peeling when it is not sufficiently cooled and solidified after heat sealing: this external force often occurs in automatic filling and packaging machines. Therefore, for composite film rolls for automatic packaging, heat sealing materials with good thermal viscosity should be selected. Anti-pollution heat-sealability, also known as heat-sealability of inclusions, refers to the performance of heat-sealing when the contents or other contaminants adhere to the hot cover. The composite film selects different heat-sealing resins according to different objects to be packaged, regardless of the packaging machinery and different packaging conditions (temperature, speed, etc.), and it is not possible to adopt a uniform heat-sealing layer. For packages with poor heat resistance, low temperature heat sealing materials should be used. For heavy-duty packaging, heat-seal materials with high heat seal strength, high mechanical strength, and good impact performance should be selected. For high-speed packaging machines, low-temperature heat seals and heat-sealing materials with high thermal adhesion strength should be selected. For powders, liquids and other highly polluting products, good anti-pollution heat seal materials should be used.
Four, heat sealing extrusion PE problem
In the heat sealing process of the composite film, PE is often extruded and adhered to the heat sealing film, and the more the accumulation, the more it affects the normal production. At the same time, the extruded PE oxidizes and emits smoke on the heat sealing die, which gives off an odor. Heat-sealed extruded PE can generally be solved to some extent by reducing the heat-sealing temperature and pressure, adjusting the formula of the heat-sealing layer, and modifying the heat-sealing film to reduce the pressure at the edge of the heat-sealing film. But practice has proved that the best solution is to use extrusion compounding technology to produce composite film, or to increase the speed of the packaging machine, so that PE is too late to be extruded onto the heat-sealing film.
Five, heat seal press-through, press-off problem
Press-through means that the packaging material is squeezed by external force to form a penetrating hole or crack. The causes are generally:
â‘ The heat sealing pressure is too high. During the heat-sealing process, if the heat-sealing pressure is too high or the heat-sealing molds are not parallel, resulting in excessive local pressure, it will often press through some fragile packaging materials.
â‘¡The heat sealing mold is rough, with edges or foreign objects. Newly-manufactured heat-sealed molds often crush packaging materials. Some heat-sealed molds produce sharp edges and corners after being damaged, and are also very easy to penetrate through the packaging material.
â‘¢The thickness of the packaging material is not correct. Some packaging machines have requirements on the thickness of packaging materials. If the thickness is too large, some positions of the packaging bag may be pressed through. Such as pillow-type packaging machine, the thickness of the packaging material should generally not be greater than 60um, if the packaging material is too thick, it is easy to crush at the middle sealing part of the pillow-type packaging.
â‘£The structure of the packaging material is not correct. Some packaging materials have poor resistance to puncture and can not be used to package some hard and angular things.
⑤ Improper design of packaging mold. In the design process, if the die hole of the heat-sealing mold does not match the shape and size of the package, and the mechanical strength of the packaging material is not high, it is also easy to puncture or crack the packaging material during the packaging process.
Sixth, the problem of heat sealing leakage
Leak seal is due to the existence of certain factors, so that the part that should be melted by heating is not sealed. There are several reasons for leaking:
â‘ The heat sealing temperature is not enough. The same packaging material requires different heat sealing temperatures at different heat sealing parts, different packaging speeds require different heat sealing temperatures, and different packaging environment temperatures require different heat sealing temperatures. The vertical sealing and horizontal sealing of packaging equipment require different heat sealing temperatures. The temperature of different parts of the same heat sealing mold may be different. These are all issues that must be considered in packaging. For heat sealing equipment, there is also a problem of temperature control accuracy. At present, domestic packaging equipment has poor temperature control accuracy, generally with a deviation of 10 ~ C, that is, if the temperature we control is 140%, In fact, its temperature is between 130-150 ~ C during the packaging process. Many companies use random sampling to check the airtightness of finished products. In fact, this is not a good method. The most reliable method is to sample at the lowest temperature point within the temperature change range, and continuous sampling should be performed so that the sample can cover all parts of the mold in the vertical and horizontal directions.
â‘¡The sealing part is contaminated. During the filling of the packaging, the sealing position of the packaging material is often contaminated by the packaging, and the pollution is generally divided into liquid pollution and dust pollution. Solving the problem of contamination of the sealing part can be solved by improving the packaging equipment and using anti-pollution and anti-static heat sealing materials.
â‘¢ Problems with equipment and operation. If the heat seal mold contains foreign objects, the heat seal pressure is not enough, and the heat seal molds are not parallel.
â‘£ Problems with packaging materials. Such as corona over the surface, too much slip agent in the heat seal layer and cause poor heat seal.
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