Waterproof Enclosure: Guide for Waterproof Design
Waterproof enclosure is employed in a variety of industries, regardless of whether you’re creating the next big electronics product. We’ll look at the design elements in this post to make sure you never wreck your prototype again.
Since the definition of “waterproof” is ambiguous, we must define it. An electronics waterproof enclosure for monitoring deep-sea drilling equipment, for instance, has different needs than a smartphone waterproof enclosure made to prevent rainwater damage.
Thus, how waterproof is waterproof enough for your application?
The International Protection (IP) Marking System
The International Protection (IP) marking system, also known as the Ingress Protection marking system, provides a universally recognized method for assessing the resilience of electronic waterproof enclosure. It imparts a tangible understanding of the term “waterproof” by employing standardized tests that must be successfully passed to attain varying degrees of waterproofness. The IP system comprises two distinct numbers following the “IP” designation. The first number signifies the level of dustproofing, while the second signifies waterproofing.
If the sole concern is indicating the degree of waterproofing, an “x” can be substituted for the first number. For example, “IPx7” conveys information solely about the waterproof characteristics, without addressing dustproofness.
The higher the IP rating, the more effective the sealing design of waterproof enclosure. For instance, a product bearing an IP67 rating offers substantially greater protection against environmental elements compared to one with an IP14 rating.
For most applications, the lowest rating deemed “water-resistant” is typically IPx4. This classification is applicable to many older watches and implies that the internal components will continue to function after exposure to a splash of water. However, submersion in water beyond this level becomes problematic.
IPx5 represents a notable advancement. In this scenario, the interior components remain operational when the waterproof enclosure is sprayed with water from any angle. Nevertheless, this level of waterproofing is contingent on a light spray or one with a flow just above 4 psi.
IPx6 entails more rigorous testing, requiring the waterproof enclosure to maintain waterproofing against a 100-liter-per-minute jet at 15 psi for several minutes. This level poses a significant challenge for most consumer electronics, and those that succeed often proudly tout their “IP Rated” status.
With an IPx7 rating, the test entails submergence in one meter of water for 30 minutes. Failure in this test can result in irreparable damage to electrical components.
Pro-tip: Achieving success with the static water pressure of a one-meter depth doesn’t guarantee success with the forceful water jet test of IPx6. Therefore, it’s prudent to test for both scenarios if the design necessitates resistance to powerful spray.
At the IPx8 level, we enter the realm of video camera housing. An IPx8 rating signifies that the waterproof enclosure can withstand prolonged submersion at a specified depth. For video cameras, this depth is often 60 meters. At this depth, the waterproof enclosure are guaranteed to remain sealed under a pressure of 87 psi—remarkable resilience.
IPx9 testing focuses on close-range, high-pressure, and high-temperature spray downs. At this level, waterproof enclosure begins to incorporate specialized and esoteric design elements, making it increasingly challenging to maintain the expected sealing mechanisms.
So, now that we understand the various levels of waterproofness, the question remains: How can a seal be designed to withstand these rigorous tests?
The NEMA Rating System
The National Electrical Manufacturer Association (NEMA) has established a rating system designed to assess the level of protection provided by a product against various environmental factors, including exposure to oil, corrosive substances, snow, and more. Unlike the IP (Ingress Protection) rating system, NEMA is primarily employed in industrial applications and encompasses a broader range of considerations beyond safeguarding against water and dust.
To utilize the NEMA rating system, one must first determine whether the product is intended for indoor or outdoor use. Subsequently, the assessment involves identifying the specific environmental elements the product is likely to encounter, as well as whether it will be subjected to activities such as hosing down and exposure to corrosive agents, oil, or coolant.
As per this system, products designated for indoor use are assigned ratings ranging from 1 to 13, with each rating indicating an increasing level of protection against elements typically encountered indoors. Similar to the IP system, the higher the NEMA rating, the more robust the protection it offers.
For outdoor applications, NEMA provides ratings such as NEMA 3, 3R, and 3S. NEMA 4, on the other hand, corresponds to products intended for use in conditions involving high-pressure water exposure, such as washdown operations.
Designing Effective Seals
While there is a multitude of seal types available, three of the most common include face gaskets, static o-ring seals, and dynamic o-ring seals. Each will be briefly discussed here, but for a deeper dive into o-ring design, the *Parker O-ring Handbook* serves as a comprehensive yet, admittedly, somewhat dry resource on the subject.
One noteworthy advantage of o-rings is their well-established technology. Recommendations for their use have remained relatively unchanged for over five decades, ensuring their reliability in keeping your design waterproof.
Static O-ring Seals
Static o-ring applications are ideal when the connection you’re sealing is predominantly round or convex, and the two mating parts will remain together indefinitely (unlike certain celebrity relationships that didn’t stand the test of time, *sigh*), or will at least be joined most of the time.
O-rings are available in various sizes, indicated by the “dash” number. No, o-rings aren’t participating in sprint races – the dash number is an ASTM designation denoting a standard size (see chart here). Typically, a larger last two numbers indicate a greater o-ring inside diameter (ID), while a larger first number signifies a greater cross-sectional diameter.
When incorporating an o-ring into your seal design, you’ll need to create a groove to accommodate the o-ring. The groove design remains relatively consistent, whether you’re sealing two flat surfaces, a threaded connection, or even a square peg in a round hole (alright, maybe not the last one, but the first two certainly apply).
For your design, you need to consider four primary elements:
- The internal diameter (ID) / internal perimeter (IP) – ID for round seals, IP for non-round seal shapes.
- The percentage stretch of the o-ring.
- The cross-sectional diameter (also known as o-ring width).
- The percentage squeeze.
First, examine the ID of the seal or calculate the IP if your shape isn’t circular. For a video camera waterproof enclosure, this entails summing the lengths of the four straight sides plus the chords from the corner radii. Once you’ve determined the ID/IP, look at the ASTM charts to find o-ring options with a similar, but slightly smaller ID to account for the percentage stretch. For a static seal, you’ll typically want the o-ring ID to be around 1-5% smaller than the groove ID. This ensures a snug fit against the sealing surface and minimizes movement under external pressure.
Pro-tip: If you’re designing for internal pressure, you’ll want to consider the outside diameter, as that is the sealing surface.
The groove width depends on the cross-sectional diameter of your o-ring, which, in turn, is based on the expected variation in the surfaces being sealed. If you anticipate a tolerance of +/- 0.010″ on the sealing surfaces, a 0.010″ o-ring may struggle to seal certain gaps. Conversely, if your parts are precision-machined with tight tolerances, using a 1/4″ thick o-ring may be excessive.
Once you’ve determined the o-ring width, you can calculate the groove width using the o-ring volume and the cross-sectional areas of the groove and o-ring. To establish a seal, you’ll need to compress the o-ring, aiming for a 10%-40% compression (also referred to as the squeeze) of the o-ring. Additionally, ensure that the maximum cross-sectional area of the o-ring, accounting for tolerance variations, is smaller than the minimum cross-sectional area of the groove.
Feeling a bit overwhelmed with calculations? The good news is we’re almost done, and you’ll soon be able to seal your waterproof enclosure as securely as the secrets in the X-Files.
Dynamic O-ring Seals
Utilizing a dynamic seal doesn’t imply you can casually open a waterproof enclosure underwater. However, many situations require components to move while exposed to rain or even while submerged. The challenge then becomes how to ensure the waterproof enclosure remains watertight.
Dynamic seals share commonalities with static seals but with reduced compression and a greater need for lubrication. The same rules and percentage principles apply, with one notable difference: for dynamic seals, you typically require a compression rate of 10%-30%.
Delving into gasket design could warrant an article of its own, or perhaps an entire book, or even a modest library. For now, let’s focus on the primary consideration for using gaskets as opposed to o-rings: Gaskets shine in applications requiring intricate face-to-face seals, particularly when multiple cavities are involved.
In this context, we’re specifically addressing waterproof gaskets, so there’s no need to delve into the complexities of internal combustion engines or extreme high-pressure seals (apologies to the gearheads).
Similar to o-rings, when working with gaskets, you must consider the compression required for your specific application, as well as the gasket thickness, typically based on the tolerances of the two mating surfaces. The beauty of gasket design is that gaskets are typically custom-made, eliminating the need for iterative calculations based on standard sizes. Custom designs offer the flexibility to meet specific requirements.
However, custom options come with a responsibility. When bolting together two parts, the surfaces can warp between the bolts. Therefore, it’s essential to strategize how to space the mounting hardware to minimize warping adequately while maintaining a seal with the thickness of the specified gasket. In simpler terms, if you bolt two parts together at the corners, the central area may have a greater gap than the corners. If this gap exceeds the gasket’s thickness, your waterproof enclosure could develop leaks. Additionally, if the gasket material is excessively rigid and doesn’t account for the surface roughness of the two mating parts, you might encounter leakage issues. Thus, it’s crucial to choose a gasket material that is sufficiently soft to accommodate machining marks unless a smooth surface is explicitly specified.
A Note on Compression Set
A recurring challenge with rubber seals is creep, a characteristic of elastomers that causes them to conform to the shapes of surrounding surfaces and lose their original form. Effective management of creep primarily revolves around careful material selection. Many materials resembling rubber have been developed over time with a focus on minimizing creep.
Pro-tip: Extensive material research is recommended before selection, leveraging resources like MatWeb and the Parker website to guide your material choices.
In a multitude of applications, both consumer and industrial, electronic devices feature interfaces that allow human interaction. Buttons are among the most common interface components. In low-pressure scenarios, it’s common to employ molded rubber buttons that create a seal with the waterproof enclosure. They are cost-effective and straightforward. Further details on button design can be explored in a dedicated article on the topic.
Alternatively, you can opt for buttons crafted from hard materials, such as stainless steel, which pass through the waterproof enclosure using a dynamic o-ring seal. These buttons are typically used in heavy-duty applications, such as undersea waterproof enclosure, where high pressure could inadvertently activate soft rubber buttons. Hard buttons also find utility in environments where harsh chemical compounds might lead to the failure of rubberized buttons.
Similarly, virtually any type of switch, from slide switches to knobs, can be integrated into the waterproof enclosure using calculations appropriate for a dynamic o-ring seal. It’s essential to bear in mind that incorporating more seals into your design increases the potential points of failure, so exercise caution when doing so.
Recommendations for Waterproof Prototyping
When embarking on the design of a waterproof enclosure, it’s often wise to begin with lower-resolution materials to fine-tune the fit, functionality, and aesthetics before evaluating the design’s waterproof capabilities. Using materials like 3D printed PLA can be a great initial step to visualize the appearance of waterproof enclosure, while materials such as 3D printed ABS and Nylon can serve well for assessing part interfaces. If you intend to incorporate custom gaskets into your design, you can evaluate the fit by creating a first prototype using a printed rubber-like material.
However, it’s important to note that waterproof enclosure with lower-resolution materials may not be suitable for housing electronics and submerging them in a swimming pool. To achieve an effective seal against o-rings or gaskets, you’ll need higher-resolution materials such as VeroWhite, VeroBlack, ABS, or VisiClear. These materials enable precise printing, ensuring a high-quality seal.
For applications demanding very high-pressure seals, taking an additional step by opting for a CNC machined prototype becomes essential. This choice allows you to maintain control over surface quality, ensuring a robust design before subjecting it to rigorous underwater testing. Our CNC manufacturing capabilities are well-equipped to strike a balance between cost-efficiency and the high quality necessary for these types of tests.
You know what to do for your next design project, whether it involves the extremes of a Mars expedition or is just to keep electronics safe from a cup of coffee to a light rain:
Make an interface plan.
Verify a few numbers to find out how big your o-rings are.
Select the appropriate button designs for your application.
You may then relax knowing that your waterproof enclosure is completely watertight.
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