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Control of cursor tracking and positioning of compound film for pharmaceutical packaging
Time: 2013-05-08 Source: Frontier of Packaging Read: 14535 times
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Wenzhou Junchuan Machinery Equipment Co., Ltd.
Composite film for pharmaceutical flexible packaging refers to combining various plastics with paper, metal or other materials through lamination extrusion, co-extrusion blow molding and other technologies to combine several substrates with different properties to form a multilayer structure. This structure has The functions of dust-proof, anti-dirt, gas-barrier, scent-retaining, UV-proof, easy to decorate and print, easy to machine or other various sealing methods can basically meet the various requirements for flexible packaging of medicines.
The composite film for pharmaceutical packaging is mainly used for the packaging of powders, granules, Chinese medicine decoction pieces, tablets, capsules, transdermal patches and medical devices, etc. It is a medicinal packaging material that directly contacts the medicine. It leaves the factory in the form of a roll film and requires online automatic packaging in a pharmaceutical factory. At present, medicine packet machines have various styles according to the contents of the package. For example, single-row packaging machines for packaging granules and powders are divided into vertical and horizontal. There are two types of rollers and palms. The bagging form is three-side seal and back seal; a multi-row packaging machine, the bag form is four-side seal and the back seal is easy to tear; etc. Manufacturers use the working principle of the packaging machine, and the control accuracy is very different. Different packaging machines also have different requirements for the error range of printing color mark spacing. Because the error range of the color mark interval printed on the packaging material does not correspond to the correction error range of the packaging machine, the material may not be used normally, and even the entire batch of materials may be scrapped.
First, the design of the electric eye cursor <br /> During the automatic packaging process of the composite film coil, positioning heat sealing and positioning cutting are often required, and an electric eye cursor needs to be set for positioning. The size of the cursor is different for different packaging opportunities. The cursor is generally required to be wider than 2mm and longer than 5mm. The cursor is generally selected as a dark color with a large contrast with the background color. It is best to use black. Generally, red and yellow cannot be used as the cursor, and a color scale with the same color as the photoelectric eye can not be used as the cursor color. For example, the light of the photoelectric eye is green. Light, you cannot use the light green color as the electrical eye cursor color, 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.), the cursor should be designed as a hollow cursor. In addition, the aluminized film and aluminum foil have a strong reflective effect, so when using color ink (with certain transparency) as the printing color of the electric eye cursor, a padding should be designed under the cursor to enhance the detection contrast of the cursor.
Design and control of cursor spacing
1. Cursor typesetting design <br /> Commonly used different plastic films , such as PE, CPP, ordinary BOPP, matte BOPP, BOPET, BOPA, etc., have different heat resistance and thermal stability (part of the film material's longitudinal thermal shrinkage The standard indicators are shown in Table 1). The change rule of the cursor spacing caused by the printing process is also different. Therefore, it is necessary to appropriately adjust the cursor pattern spacing during typesetting for different types of printing composite films and different printing composite processes. Zoom.
Table 1 Technical index of thermal shrinkage in some film standards
Film type Index of longitudinal heat shrinkage,% Test Conditions
Ordinary BOPP (non-heat-sealable) ≤4.5 120 ℃ ± 2 ℃ , 120S
PVDC coated BOPP film (KBOPP) ≤4.0 120 ℃ ± 2 ℃, 2min
PVDC coated PET film (KBOPET) ≤2.0 150 ℃ ± 2 ℃, 30min
BOPA, KBOPA ≤3.0 160 ℃ ± 2 ℃, 5min
BOPET ≤3.0 150 ℃ ± 2 ℃, 30min
Pearlescent BOPP ≤4.5 120 ℃ ± 2 ℃, 2min
2. Tension control during the production process <br /> In the composite film production process, the typical composite film structure for pharmaceutical flexible packaging is PET / AD / AL / AD / PE, PET / AD / VMPET / AD / PE (Note, Here AD stands for adhesive layer or resin with adhesiveness). Here we take PET film as an example to analyze the influence of tension control and process conditions on the change of cursor spacing.
After the polyester film is printed, the cursor pitch tends to decrease, and the degree of reduction depends on the feed tension during printing. This is because in order to ensure a good printing effect, the feeding tension is generally set to be large when printing, and the tension control of the winding tension of the semi-finished product is small. The printed graphics obtained by printing the material under a large tension state are restored to a small tension. After the control state, retraction occurs in the direction of longitudinal force. In general, if the feed tension is controlled properly, the cursor reduction after printing is within 1.5 ‰; if the control is not ideal, the cursor spacing reduction after printing can be up to 3 ‰. In the same way, if the drying tunnel tension of the dry compound is properly controlled, the stretching amount can be controlled within 1 ‰, especially when the compounding time is too large, the excessive drying tunnel tension will lengthen the cursor distance, and the maximum stretching amount can be adjusted. Up to 2 ‰. Compared with extrusion lamination, the temperature of the extruded resin can reach 300 ° C or higher. The effect of the same lamination tension on the distance between cursors is much greater than that of dry lamination. It can reach 6 ‰ and the average stretch is 3 ‰. It can be seen that the magnitude of the compound tension has a greater impact on the extrusion stretch.
According to the above, according to the different widths, thicknesses, and roll diameters of the materials, under the premise of ensuring that the normal production process of the film can be completely flattened, the use of low tension control to control the cursor spacing is of great significance. The composite process is adjusted accordingly in the plate making process. If the extrusion compound process is used for a single compound, it is generally recommended that the plate roller is reduced by 3 ‰ from the reference size given by the customer. The control range of cursor spacing is generally: for common dry structure products, the change in cursor spacing can be controlled within ± 1 ‰; for common extrusion structure products, the change in cursor spacing can be controlled within ± 1.5 ‰.
Influence of material friction coefficient
The friction during packaging is often both drag and resistance, so its size should be controlled within an appropriate range. Rolls for automatic packaging generally require a small inner friction coefficient and a suitable outer friction coefficient. Too much outer friction coefficient will cause excessive resistance during the packaging process and cause tensile deformation of the material. If it is too small, it may It will also cause the drag mechanism to slip, resulting in inaccurate tracking and cutting positioning of the electric eye. However, the inner layer friction coefficient should not be too small. Some packaging machines have too low inner layer friction coefficient, which will cause the stacking material to be unstable during bag making and produce wrong edges. For the composite film for strip packaging, the inner layer friction coefficient is too small. It may also cause the feeding of tablets or capsules to slip, resulting in inaccurate positioning of feeding (usually seen on soft double aluminum packaging composite equipment). The inner layer friction coefficient of the compound film for pharmaceutical packaging mainly depends on the content of the opening agent and slip agent of the inner layer material, the stiffness and smoothness of the film, whether the corona treatment is over the surface during the production process, curing temperature and time, etc. It also affects the friction coefficient of the product.
When studying the coefficient of friction, special attention should be paid to the effect of temperature on the coefficient of friction. Therefore, not only the friction coefficient of the packaging material at room temperature should be measured, but also the coefficient of friction at the actual temperature of the environment should be examined. Table 2 shows that the friction coefficient of the test specimen 4 is sticky when the test specimen is above 36 degrees, and the test cannot be continued. Therefore, in the actual production process, we must pay more attention to the rationality of the friction coefficient control under the actual production and application temperature conditions.
Table 2 Friction coefficient between inner film and steel plate tested at different temperatures
Specimen name 26 ℃ 36 ℃ 46 ℃ 56 ℃ 66 ℃
Quiet move Quiet move Quiet move Quiet move Quiet move
1# 0.198 0.127 0.177 0.152 0.138 0.141 0.163 0.167 0.162 0.159
2# 0.228 0.213 0.159 0.147 0.224 0.222 0.231 0.219 0.229 0.203
3 # 0.176 0.159 0.142 0.144 0.176 0.177 0.187 0.169 0.172 0.167
4 # 0.247 0.245 / / / / / / / /
Remarks: Lab temperature: 23.0 ℃; Lab humidity: 50.0% RH; Testing equipment: Languang FPT-F1 friction coefficient / peel tester; Test conditions: friction between material and steel plate No. 4 test specimen is sticky at 36 ° and above.
Control of the automatic packaging process
1. Photoelectric eye adjustment method and working state selection Identification of color markers. Taking a KT-RG22 photoelectric eye as an example, the method of adjusting the photoelectric eye is briefly introduced here:
Fix the photoelectric switch so that the detection distance meets the requirements (KT-RG22 detection distance: 12mm). According to the packaging film used, refer to the light source selection guide table in Table 3, determine whether to switch the light source (taking green as an example), and then decide whether the output mode is bright or dark according to the needs of the packaging machine . Finally, adjust the sensitivity according to the following three steps (the output is activated in the following way, the packaging logo is light, and the back is dark).
① Move the packaging film so that the light spot falls on the back area behind the mark, rotate the sensitivity in the opposite direction, and then slowly rotate it clockwise until the indicator light just turns on. Remember the position of the potentiometer at this time (point A).
② Move the packaging film so that the light spot falls in the center of the mark. At this time, the indicator light is on, and then slowly turn the adjustment knob counterclockwise until the indicator light just goes out. Remember the position of the twist at this time (point B).
③ After completing the above two steps correctly, twist the potentiometer to the middle C position between A and B, and the adjustment is completed. The larger the distance between the two points A and B, the larger the color difference is, and the more stable the detection is. However, there must be at least one grid distance between points A and B, otherwise the detection will be unstable.
Table 3 Selection Guide of Electric Eye Source
↑ back
view
Red LED ↑ back
view
Green LED
black - X X X black - X X X
silver - X X X X X silver - X X X
red X - X X X X red - X X X X X X
Orange X X - X X X