1.During the folding and shaping process of paper boxes and cartons, cracks or even fractures occur at the indentation lines; or uneven glue penetration on the surface of the paperboard affects the appearance and strength.
答：
Paper breakage usually occurs due to insufficient moisture content in the paper (caused by dry environment which makes the paperboard brittle), or excessive pressure in the embossing mold and too deep embossing lines. Gluing failure is mostly caused by low glue viscosity, excessive coating amount, or excessive water absorption of the paperboard surface. These problems are particularly common during the dry winter season.
Solution: Control the humidity in the workshop (recommend maintaining at 50% - 60% RH); Calibrate the pressure and depth of the embossing mold according to the paper weight and type; Select the appropriate viscosity of glue and control the coating amount; If necessary, add a barrier coating on the surface of the paperboard.
2.The heat sealing strength of the packaging is generally qualified on a daily basis. However, during actual use, some packages exhibit "false adhesion" at the sealing area, and they will break if slightly pressed.
答：
The problem lies in the fact that there are trace amounts of contamination in the sealing area that are invisible to the naked eye, such as lubricating oil mist from the production environment, dust, and the sweat of the operators. These contaminants prevent the fusion of the sealing layer molecules at the microscopic level, resulting in a sealing strength far below the normal value. For example, in a certain case, the strength of the contaminated seal was only 6.0 N/15mm, which was less than one-sixth of the strength of the un-contaminated area (37.5 N/15mm).
Solution: Keep the filling equipment clean, avoid the splashing of lubricating oil and cleaning agents; standardize the clothing of operators (gloves, masks); increase the inspection of the cleanliness of the surface of the sealing area; regularly use surface energy testing (determination pen) to check whether the sealing layer is contaminated.
3.After the composite film is used to make the bag, the bag body may curl up or the two sides may bulge towards the center when opened, which affects the normal material feeding and sealing effect of the filling production line.
答：
The main reason is that the thermal contraction rates of the materials in each layer of the composite film do not match. The high temperatures during the printing, compounding, and curing processes cause each layer to contract to varying degrees, resulting in an imbalance of internal stress. If the difference in contraction rates between the two layers of the BOPP/CPP composite structure exceeds 0.5%, the finished bag is highly prone to warping. Additionally, the tension changes brought about by ink and solvents during the intaglio printing process may also exacerbate this issue.
Solution: When selecting materials, match the thermal shrinkage rates of each layer of the base materials (it is recommended that the difference be controlled within 0.5%); optimize the tension and drying temperature during printing and compounding to reduce cumulative internal stress; perform heat setting treatment or hanging-style curing on the finished product to release the stress. The thermal shrinkage test can be conducted by the shrink tester LTRSY-03 (https://www.linktesting.org/2334.html/thermal-shrinkage-tester-ltrsy-03/)
4.The packaging was designed with an easy-tear opening. However, when opening it, the tear opening deviated from the pre-cut line, resulting in difficulties in tearing or even the packaging tearing. The user experience was extremely poor.
答：
The easy-tear effect not only depends on the tear opening design, but also highly relies on the anisotropy of the material. If the tear strength of the film in the transverse (TD) and longitudinal (MD) directions varies greatly, the tear force will spontaneously shift towards the direction with lower strength. For example, if the MD/TD tear strength ratio of a unidirectionally stretched film reaches 5:1, it leads to a severely skewed tear path.
Solution: When selecting materials, pay attention to the tear strength ratio of the material and try to choose materials with similar tear strengths in the transverse and longitudinal directions; optimize the shape design of the easy-tear opening (such as an arc-shaped opening is better than a V-shaped one); when using laser tear lines, the laser power and line type density can be adjusted to guide the tear direction. The rectangular tearing can be conducted by the Elmendorf Tearing Tester LTLD-1000Z (https://www.linktesting.org/835.html/elmendorf-tearing-tester-ltld-1000z/)
5.The aluminum-plastic blister packaging of the medicine has tiny invisible pinholes on the aluminum foil layer, allowing oxygen and water vapor to seep in, causing the pills (such as vitamin C, aspirin) to change color, get damp, and lose their efficacy.
答：
During the rolling process of aluminum foil, pinholes may occur due to micro-irregularities of the rolling rolls, dust contamination, etc. The detection standard (such as YBB00152002) stipulates that the diameter of pinholes in aluminum foil should be ≤ 0.3mm, and there should be no more than one per square meter. However, in actual production, if the temperature and pressure during the heat sealing and bonding process of aluminum foil and PVC are out of control, it may also cause damage to the protective layer (OP/AL) of the aluminum foil, resulting in the formation of new micro-pores.
Solution: Conduct pinhole detection on the incoming aluminum foil (using a pinhole tester or light transmission method); optimize the heat sealing process parameters to avoid damage to the aluminum foil due to excessively high temperature or pressure; conduct a dye penetration test on the finished product packaging to check if there are any leakage channels in the aluminum foil layer. The test can be conducted by the pinhole tester LTZK-02 (https://www.linktesting.org/993.html/aluminum-foil-pinhole-tester-ltzk-02/)
