Discussion on the design of polystyrene foam cushi

2022-07-25
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Discussion on the design of polystyrene foam cushioning packaging for dishwasher II

2. determination of buffer pad size

2.1 because the outer box size of dishwasher has been determined, that is, the thickness of foam cushion can only be 30 mm. In order to ensure the effectiveness of the cushion, low-density, medium density and high-density foamed plastics are used successively in the design process. After practical tests, it is found that due to the strength problem of the product itself, the cushioning effect of high-density foamed plastics is ideal. This is due to the large deformation of medium and low density foams and the easy deformation of products, so the deformation of products cannot be effectively protected. The high-density foam has good strength and can better protect the product from deformation

it is reasonable to use polystyrene foam with density of 0.025 as cushion according to relevant standards when using curve to design cushion. When the buffer coefficient curve of this material =8.8, the corresponding minimum buffer coefficient c=3.4. According to h=46 cm and g=40 (check the standard and estimated value), the calculated buffer pad size is: =3.4 × 46/40=3.91cm

2.2 as the dishwasher is of heavy weight, the plastic film with thickness of t=0.3mm is selected as the design material of the single air cushion. The transverse tensile ratio, longitudinal tensile ratio, longitudinal heat sealing strength and transverse heat sealing strength of the material are respectively 344.8%, 296.4%, 28.4 (n) and 27.6 (n). It can be seen that the selected plastic film with a thickness of t=0.3mm has ideal tensile ratio and good heat sealing strength. It is the best choice as a monomer buffer material

3. test and comparison of foam plastic and air cushion packaging

3.1 vibration test and comparison of foam plastic and air cushion packaging

vibration is one of the main factors for commodity damage in the circulation environment with the concept of green energy conservation becoming more and more popular. The natural frequency of the commodity can be found through the sinusoidal vibration test, in order to avoid resonance under the natural frequency of the commodity as much as possible in the packaging design. The test block diagram is shown in Figure 4:

after the two buffer designs are made, they are packed according to the requirements. Using ya/zf type 100kg mechanical shaking table, acceleration sensor, YE5850 charge amplifier and data acquisition and analysis system (all products of Northwest Machinery Factory), the package is fixed on the shaking table to experience 3~50 sweep frequency vibration, Record the acceleration at the corresponding frequency every 5 increments. The precautions for the parameter detection are as follows: ① measure from the thinnest point visually; ② It is assumed that the insulation test piece includes the indentation value of the imprinted mark, so as to determine the natural frequency and resonance frequency of the package

the vibration test results are shown in Figure 5:

it can be seen from the above figure that when the bare metal machine vibrates, the dishwasher resonates at 35; The first-order resonance frequency of the package when the foam plastic is packaged appears at 30, which is limited lower than the natural frequency of the product, and there is no resonance at 35, so it can be used in the actual circulation; When air cushion packaging is used for vibration, low-frequency resonance occurs at 25 and 35. It can be concluded that the protection function of the foam packaging is better than that of the air cushion at low frequency, and the protection function is not as good as that of the air cushion facing the pressure of the international market at high frequency

when the air cushion is packed, resonance occurs at 25, so the excitation frequency at the natural frequency of 35 will not damage the product. Although the package still resonates at 35, the peak acceleration here is significantly less than that of the foam plastic. The package can be resonated for 15 minutes under the resonance state. If the product is not damaged, it can be considered as qualified. In addition, if the structure of the monomer or the amount of gas in the monomer is changed, the buffer effect can be improved. (to be continued)

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