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Talking about the design points of the hard blister box for
Release: Hexiang Packaging  Time:2021-09-14

The packaging of sterile medical device products is a very important special process. To ensure the safety and effectiveness of medical device products, the packaging process must be strictly controlled. Although the ISO11607 international standard is coordinated with the European Union EN 868-1 standard to provide general requirements for packaging materials. In the process of hard blister packaging of medical devices, blister packaging design and mold making of products are particularly important, which can directly affect the intended use, failure, transportation and storage of medical devices.



General principles that should be considered in the blister design of medical devices:


1) Give full play to the characteristics of the plastic itself, such as physical properties, and try to avoid or compensate for its shortcomings. The main considerations are strength, rigidity, toughness, elasticity, water absorption and sensitivity to stress; plastic molding processability, such as fluidity; shrinkage after molding and its anisotropy.


For example, when designing PETG materials, fully consider the characteristics of the material itself. Although PETG has excellent punching and cutting performance, its punching force is 60% higher than that of PVC. On the other hand, the cutting time is quite short. The cutting length of the heated die can be increased accordingly, by 11% at 100°C, 25% at 130°C, 40% at 160°C and so on.


2) The shape of the blister product, under the premise of ensuring the use requirements, make the shape and structure of the blister product simple; the wall thickness is uniform, and it is easy to form and demold; it is conducive to exhaust, feeding and cooling; try to avoid acute angles ( Especially the inner corners) to avoid anisotropy of the parts.


3) Plastic parts should consider the overall structure of the mold, and fully consider the shape of the subsequent mold and its manufacturing process, which has better economic efficiency.


The process design of medical device blister packaging mainly includes the product's geometric shape, dimensional accuracy, stretch ratio, surface roughness, wall thickness, slope, hole, fillet, mold slope and ribs, etc. But how to design more professional blister packaging for medical devices? The following are some tips from the professional R&D and design team of Suzhou Fangwei aseptic packaging, and I would like to encourage you:


(1) Product geometry and accuracy. Since thermoforming is a secondary process, especially differential pressure molding, there is a certain gap and shrinkage between the blister coil and the mold, especially the convex part, the wall becomes thinner, and the strength is affected, so the dimensional accuracy is required Can't be too demanding. (In addition, the product is thin, and its shape and size are very unstable due to changes in temperature and environment, so it cannot be regarded as precision molding like injection molding).


(2) Stretch ratio. The ratio of the height (or depth) to the width (or diameter) of the part becomes the stretching ratio. Or called the extension ratio. The stretch ratio reflects the difficulty of plastic molding to a large extent. The larger the stretch ratio, the more difficult it is to mold. The stretch ratio generally used is 0.5 to 1.


(3) Fillet. The corners of the plastic parts are not allowed to have sharp corners, and the rounded corners of the corners should be as large as possible. Generally, the radius of the fillet is not less than 4~5 times or greater than the thickness of the processed sheet, otherwise the corners are particularly prone to thickness reduction and stress concentration.


(4) Slope. Refers to the inclination of the draft, the inclination range is 1°~4°. The lower limit can be taken for the female mold forming. Because the shrinkage of plastic parts provides clearance for accessories.


(5) Reinforcing ribs. Usually in order to ensure the rigidity of the plastic part, and because the material of the blister product cannot be too thick, and it is also restricted by the stretch ratio, the bottom corner part will be thinner. Therefore, the reinforcement ribs are designed in the appropriate parts of the product to improve the manufacturing. The rigidity and strength of the piece.


(6) Shrinkage of blister products. The blister product has a large shrinkage in the later stage, and about 50% of the shrinkage is produced when it is cooled in the mold. Due to the high mold temperature, the blister product is cooled to room temperature after demolding, with about 25% shrinkage, and the remaining 25% is cooled after 24 hours. Therefore, molds must be made according to different product characteristics during design. 

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