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With the continuous emergence of new materials and technologies, multi-layer thick plate blister has been applied to the field of hospital medical equipment shell molding and manufacturing, opening a new chapter in the structured products of hospital medical equipment shell. Therefore, it is necessary to explore the relevant elements of thick plate Blister products of hospital medical equipment shell, and consider the optimization path of thick plate blister technology of medical equipment shell, so as to improve the quality of thick plate products of hospital medical equipment shell.

1. Analysis of factors in the design of hospital medical equipment shell

（1）Geometry and accuracy。 The geometric dimension of the blister shell includes: the dimension of the blister product from the cutting surface to the forming surface, and the dimension from the cutting surface to the cutting surface, which is directly related to the thickness of the plate, material characteristics, and molding process.

（2）Tapering Walls。 The blister mold is composed of concave and convex molds with different demoulding angles. Generally speaking, the demoulding angle of female die is 0.5 ° ~1 °, and that of male die is 2 ° -5 °.

（3）Shell fillet。 The blister shell should be designed with rounded corners as large as possible instead of sharp corners, and chamfering should be carried out to ensure the appropriate stress of the blister shell product.

（4）Aspect ratio。 The width depth ratio of plastic products for medical device shells is an important indicator to measure the difficulty of plastic molding. It indicates the minimum width to depth ratio of products. The greater the value, the easier it is to form Blister products, while the smaller the value, the harder it is to form Blister products.

2. Defect analysis of thick plate blister process for medical equipment shell in hospital

（1）Insufficient partial molding of products。 The main reasons for the insufficient local molding of Blister products are: poor plasticity of the plate itself; Insufficient vacuum between plate and mold; The sheet is stretched too much; Mold temperature is low, etc.

（2）Product surface color defect。 The main reasons for color defects on the surface of products are: insufficient heating; Excessive heating; The mold heating temperature is not high, resulting in large product color difference.

（3）Product flow mark defect。 The main causes of flow mark defects of products include: the temperature of dies and plates is not high; Poor mold temperature control; Forming process deviation, etc.

（4）Product wrinkle defect。 The main reasons for wrinkle defects of products include: the plate is too sagging; The heating time of the plate is too long; Mold forming angle is too large, etc.

（5）Insufficient flatness of product surface。 The main reasons for the uneven surface defects of products are: insufficient cleanliness of plates or molds; Mold vacuum hole is too large; The number of vacuum holes in the mold is insufficient; The die has a sheet-like structure, etc.

3. Optimization of blister process for thick plate of hospital medical equipment shell

3.1 optimization of shell thick plate blister product structure

The shell of hospital medical equipment is large in volume and surface area, and can be designed into a curve shape, which can not only maintain the appearance of the product structure, but also avoid the defects of the blister process. The optimization of its structure mainly includes the following aspects:

（1）Optimize product depth。 There are many products with large barrel depth in hospital medical equipment, which brings great challenges to Blister products. In order to optimize the product forming effect, mold forming and punch assisted pressing can be used to heat the product sheets between the upper and lower molds, suck a small amount of air from the punch and the sheet to make the sheets adsorb on the punch, then gradually press the punch to make the sheets completely adsorb on the concave mold, and finally demould. Through this concave convex die assisted forming method, the draft angle of the equipment shell product can be increased and the width depth ratio of the shell product can be reduced.

（2）Optimize the fillet at the corner。 According to the actual requirements of assembly, the corners can be optimized at the connection of medical equipment shell products.

（3）Assembly and bonding。 For Blister products of hospital medical equipment shells, the way of assembly and bonding can be used to replace the reverse buckle design. In order to enhance the strength of shell products, double-layer blister technology is adopted instead of optimizing the bonding process of single-layer blister plate.

3.2 optimization of plastic forming process parameters of thick plate of medical equipment shell

As the materials of hospital medical equipment shells are mainly ABS and abs/pc, and the assembly materials such as PC, hips, pet, PP are used, the process parameters of these different materials should be analyzed and optimized, including the following:

（1）Sheet drying time。 This is the characteristic parameter of shrinkage rate of blister plate in dry state, which is directly related to and affects the blister forming of thick plate of medical equipment shell. When the drying time of different materials is: HDPE is 8 hours, PE is 6 hours, ABS is 8 hours, PC is 6 hours, abs/pc is 8 hours, it shows that the performance of this blister product used in thick plate of medical equipment shell is relatively stable.

（2）Blister temperature。 This is mainly analyzed and optimized from two aspects: the heating temperature of the plate and the temperature of the plastic suction mold. Among them, the plastic plate is usually heated by double-sided heating, and different forming temperatures are set according to the different shapes of the products to make the products meet the design requirements. The temperature of the blister mold should be kept appropriate and should not be too high or too low. If the mold temperature is too high, the product will adhere to the mold, resulting in demoulding deformation of the product. If the mold temperature is too low, the product will have black spots, wrinkles, cracks and other defects due to insufficient plate forming. Generally speaking, when the temperature of the blister mold of the medical equipment shell is controlled at 50 ℃ for HDPE, 50 ℃ for PE, 50 ℃ for PVC, 70 ℃ ~80 ℃ for ABS, 120 ℃ for PC and 110 ℃ for abs/pc, it indicates that the temperature of the blister mold is appropriate.

3.3 optimization of mold design

（1）Optimize high pressure blister mold。 The high-pressure frame blister mold structure can be used to completely shape the Blister products of the thick plate of the medical equipment shell.

（2）Add upper mold auxiliary molding。 By adding the method of upper mold assisted molding, the cylindrical medical equipment shell with large depth and complex shape can be manufactured, so as to avoid the defects of cross section or fold on the surface of Blister products.

（3）Increase the core pulling structure of the die。 By adding hinges, adhesive blocks and cylinder design methods, Blister products can be better demoulded.

4. Conclusion

To sum up, the production of hospital medical equipment shell cannot be separated from efficient and advanced thick plate blister technology. Vacuum Blister molding technology should be better adopted by optimizing product structure, molding process parameters, mold design and other methods, so as to meet the use requirements of hospital medical equipment shell.