Most waterproof products are only waterproof for the upper and lower shells, buttons, batteries, and sensor leads. Commonly used waterproofing methods include glue, ultrasound, inserts, and O-ring installation.

 

The main reasons for poor waterproofing are: the plastic is deformed, the waterproof surface is not in one line, and the O-ring preload is too loose or too tight.The structural rigidity is not enough, the screws are unevenly distributed, the threads are sliding, etc.

 

1 The disadvantages of plastic deformation are obvious, and there are many waterproofing methods, such as improving the plastic mouth, changing water transportation, making reinforced bones, etc. For some products, the main cause of deformation is due to the limitation of the shape, resulting in the separation of the upper and lower curved surfaces, or the internal space is too small, causing the wall thickness of the plastic parts to change too much.

 

The product shown in Figure 1 is prone to deformation due to the influence of residual stress in the plastic. If this type of product is to be waterproof, in order to reduce deformation, in addition to adding reinforced bones, increasing the demoulding slope, and adding ejection positions at relevant positions, it is necessary to position the fixture after the product has just been formed, and allow natural cooling in warm water to reduce residual stress.Of course, if the product shown in the picture is to be waterproof, it does not necessarily have to be made of an upper and lower cover like the one on the right side of Figure 1. Hirays Co., Ltd. is just giving a similar example here.

As shown in Figure 2, the product has a shell outside the transparent mirror. If waterproofing is not required, the structure in the left picture may be slightly deformed, but it can still be used. If the transparent mirror and the back shell need to be waterproofed through an O-ring, Hirays engineers suggest that it is best to use the hook in the right picture.Use a 0.15 metal cover to cover the LCD and PCB, and drive screws to fix the lens. The plastic will deform less.

2. The waterproofing is not on one surface. For the structure as shown in the picture, the surface where the O-ring is placed is an irregular surface. When the upper and lower covers are fully covered, the waterproofing line is not easy to be connected. Most of the fireproofing effects are not very good. The ultrasonic treatment effect of similar shapes is not ideal. Try to avoid it to ensure that the waterproofing line is coherent. Try to make the waterproofing line have a single shape and intersect on one side.

In the section A-A in Figure 3, whether it is placing an O-ring or performing ultrasonic treatment, Hirays Automation Co., Ltd. calls the upper and lower contact parts the waterproof line.

Uneven distribution of the screws or slippage of the screws will cause the O-ring to be pre-pressed too tight or too loose. Loose O-rings will of course lead to poor waterproofing, but it does not mean that the tighter the pressure, the better. Pressing too tight will exceed the yield strength of the O-ring, and the product will lose its elasticity after going through high and low temperatures.

After the self-tapping screws slip, the connection force will be insufficient and the waterproofing will be poor. How to remove the structure is recommended.