Pitfalls of waterproof design

Hi everyone, I’m Uemura, Manager of the WTI Sales Department.

Recently, more and more products are becoming waterproof, especially in mobile devices.
Cell phones (smartphones) are typical waterproof products, and it seems that the majority of new products currently on the market are becoming waterproof.

We have seen a rapid increase in the number of requests for mechanical designs with waterproof feature from our customers. For example, products that are constantly placed outside, those that do not specify where to be used, such as sensors, and products supposed to be in portable use, such as mobile products and small measuring devices.

As such, waterproofing is becoming a basic feature in various products on the market, and the importance of waterproofing design is likely to increase further.


So, in this blog, we will introduce the concerns of our customers who contact us for waterproofing design-related issues.

For example, we may receive a request like, “Waterproof test was fine in the prototype, but the mass production model (or the late stage prototype) failed the waterproof test. We don’t have enough time. Please examine the cause and countermeasures.”


Actually, we receive more inquiries after these problems occur than requests for waterproof design from the early stages of development. Customers who did waterproof design by themselves often had worries their design, though which seemed well on the way, turned out no good at the last minute. As a result, they were in trouble, without knowing how to solve the problems.

Also there were cases that OEM products, which were claimed to be waterproof, were found not to have such performance after mass production. So I feel that it is important to verify the waterproof performance from a third party’s perspective.

Here are a few of the pitfalls of waterproof design that we see in many customers with these concerns.


<Case Study>

1. Even though a prototype made by cutting passed the waterproof tests, a final product made of mold failed them. The reason was that the contact pressure of the packing was insufficient due to a slight difference in level which came from a split line and an ejector pin of the molding die.

→ Changing the mold split, adjusting the position of the ejector pin, and adjusting the compression rate of the packing will be necessary.

2. In the same situation aforementioned, a final product made of mold parts failed waterproof test due to insufficient contact pressure of the packing. The reason was that the contact pressure of the packing was not secured due to warped case caused from molding conditions in the final product.

→ Measures such as mold changes to compensate the warp, review of molding conditions, etc. are needed.

3. Due to widening the screw pitch to fasten between the cases just a little bit more than the prototype, the pressure on the packing in the center of the product became insufficient, resulting in the water proof test failure.

→ Measures such as the addition of small screws in the center are necessary.


As you can see, many customers experience difficulties in finding the cause of the problem, when the waterproof test for the prototype is OK, but the final product failed the waterproof test.

Since the criteria for waterproof tests are judged by whether or not water having entered the product, in many cases, the level of product’s waterproof performance is not confirmed.

However, I feel that it will be necessary to know whether it is just barely OK or has enough margin in order to miniaturize products or to ensure quality mass production in the future.

WTI has waterproof test equipment covering from IPX3 to IPX6, as well as IPX9K equivalent, allowing us to accurately assess the ability value of waterproof performance.
If you want to know the design margin for miniaturization, or if it is just barely OK with the waterproof performance test and may fail it due to variations in parts and assembly, please feel free to contact us if you want to know the capability of the waterproof performance of such products.


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