Designing Enclosures with Different IP Ratings in Product Development

Designing enclosures is given special attention in the new product development process, as it directly impacts the sales of future devices. This is primarily because enclosures have the power to transform devices into visually captivating ones while also providing a protective shield against the potential harm inflicted by water, dust, and different wastes. By way of evidence, when choosing a smartphone, all other things being equal, the user will prefer a dust- and moisture-proof device. It may cost a hundred dollars more, which has the potential to create an unpleasant experience, but the protective enclosure will save the device from water damage or dust intrusion. But why is there a price difference between a protected phone and an unprotected one if they look almost identical? In this article, we will try to explain this from the viewpoint of a product development firm.

Why is IP protection expensive?

Recently, a customer approached us with a request to develop an enclosure for their printed circuit board. The device was intended for outdoor use, exposed to harsh weather conditions. Taking all the factors into account, we assessed the labor costs and presented the customer with a commercial proposal. They were shocked by the cost and the list of required tasks. The startup believed that designing a simple rectangular box with four screws on the edges, 3D printing it, and placing the board inside would be sufficient for further design for manufacturing and assembly (DFMA). They were not concerned about weather conditions or protecting the internal components of the device. Many product design companies frequently face the situation when they have to show customers why rejecting certain types of work can actually result in losses rather than gains. Our team took on this task, demonstrating to the customer what would happen to their 3D-printed "box" in heavy rain or when exposed to dust and sand. After that, the customer agreed to develop an enclosure compliant with the IP standard.

The IP protection class indicates the level of defense against solid particles such as dust, dirt, sand, and resistance to liquid exposure. The IP dust protection rating system is standardized and consists of two digits: the first one indicates the level of protection against solid particles, and the second one indicates the level of liquid protection. The description of each possible digit is shown in the figure below.

So why is IP protection expensive? With each higher protection level, additional requirements and design limitations are imposed on the enclosure. For example, there is a printed circuit board inside the enclosure that generates significant heat during operation. If the enclosure has no IP restrictions, we can simply install a radiator with a fan in the hottest spots, create openings in the enclosure, and let the fan exhaust all the hot air outside the device. This is the simplest way to solve overheating issues. But what if the enclosure needs to be sealed? In a sealed enclosure with a high IP rating, we cannot simply exhaust the hot air outside. We have to incorporate a system of radiators with thermal pads in the enclosure and conduct a series of computer simulations to achieve acceptable temperatures inside the enclosure.

The enclosure design itself becomes more complex as the level of protection increases. Starting from IP55, which provides protection against dust and moisture, we need to use seals at the very least. Let's take a closer look at the methods of enclosure protection.

Use of Seals

Sealing tapes or rings are added in areas where dust or moisture may enter. They can have a circular or rectangular cross-section. Special grooves are provided in the enclosure to accommodate these seals. Under load, the rubber seal fills the space and prevents the ingress of moisture or dust into the enclosure. This sealing method is suitable for the production of small-batch products.

Pros of the method:

• low cost;
• simple implementation;

Its cons:

• seals wear out and require replacement;
• assembly of the enclosure becomes more complex.

Multi-component Molding

If hundreds of thousands of enclosures are planned to be produced, the best solution is to use multi-component molding. This technology allows pouring the sealant onto the surfaces of the enclosure that require sealing using a special thermoplastic molding machine. First, the enclosure is molded, then the mold is flipped, and rubber-like thermoplastics are poured into the still-hot enclosure. This technology eliminates the need for sealant gaskets and allows it to be molded automatically. This approach reduces assembly costs and improves the quality of the finished products. However, it increases the costs required for the design of the enclosure and the mold, as their construction becomes significantly more complex.

Pros of the method:

• low cost of the enclosure in mass production;
• no additional costs for assembly and sealing.

Cons of the method:

• economically inefficient for low production volumes;
• expensive equipment and tooling.

Welding and Bonding

If the enclosure is not intended to be disassembled in the future, we can use welding and bonding techniques to protect the device from dust and moisture. There are various methods of welding thermoplastics. In our opinion, the most commonly used and popular methods are:

1. Hot Plate Welding. A hot plate heats the mating surfaces of thermoplastic parts, and then the parts are pressed together to form a strong bond. The high temperature and pressure ensure a sealed and waterproof connection, protecting against dust and moisture.
2. Hot Gas Welding. A stream of heated gas, usually hot air or nitrogen, heats the plastic surfaces to soften them, and then they are pressed together to create a reliable welded seam. Hot gas welding is typically used for large or irregularly shaped parts. This method provides reliable protection against dust and moisture.
3. Laser Welding. Laser welding utilizes a focused laser beam to melt and fuse thermoplastic components. The laser energy is precisely directed to the joining area, generating localized heat that allows the plastic to melt and bond. Laser welding offers high precision and control, resulting in strong, clean welds that effectively protect against dust and moisture.
4. Ultrasonic Welding. High-frequency vibrations selectively heat thermoplastic components. The joined parts are held together under pressure, and an ultrasonic horn applies vibrations to the joining area, causing localized melting. When the vibrations stop, the melted plastic solidifies and creates a strong bond.
5. Solvent Welding. A solvent or adhesive is used to dissolve the thermoplastic material and fuse it together. The solvent is applied to the joint area, and the plastic parts are held together until the solvent evaporates, resulting in a strong bond. Solvent welding can be effective for certain thermoplastics but may not be suitable for all materials. It is important to choose a compatible solvent that interacts well with the specific thermoplastic being used.

Each welding method has its limitations, advantages, and disadvantages. With hot plate welding, the welded seam needs additional protection, and the method is only suitable for flat surfaces.

Using adhesives and solvents also has its challenges. Their use requires surface preparation and waiting for curing, and the method has lower strength compared to welding methods.

To test the degree of enclosure protection, tests are required, which, in turn, requires specialized equipment and labor costs. Only through testing can the design be verified and can you ensure that the device meets the requirements of the IP rating. The testing process involves simulating harsh environmental conditions, such as simulating heavy rain at different angles, immersion in pressurized water at various temperatures, and exposure to dust and sand. The testing process involves simulating harsh environmental conditions, such as simulating heavy rain at different angles, immersion in pressurized water at various temperatures, and exposure to dust and sand. Typically, creating prototypes of enclosures with an IP rating above 55, intended for testing, will be significantly more expensive than prototyping enclosures without IP rating. They can be 3D printed, but for enclosures with IP55 and above, 3D printing is not suitable as water can penetrate between the print layers or the dimensional tolerances of the seals may not be met due to shrinkage. Prototyping IP-rated enclosures can be done either through injection molding, which involves purchasing tooling, or by using silicone molds.

Development of IP Enclosures at EnCata

Enclosure for Electronics of a Car-Sharing service

A car-sharing startup approached EnCata with a developed printed circuit board (PCB) and the need for designing an IP66-rated enclosure for it. In addition to a high level of IP protection, the enclosure had to withstand vibrations and temperature changes ranging from -40 to +85 degrees Celsius. The device was intended to be installed inside the vehicle's engine compartment.

We offered the customer several options for the industrial design of the enclosure. The customer chose a futuristic enclosure design that provided easy access to the battery compartment for quick battery replacement.

The challenge was that the enclosure needed to accommodate connectors such as a 48 Pin FCI Automotive Waterproof ECU, mini-USB, and a U.FL/IPX to RP-SMA interface. Incorporating connectors and wired interfaces into a waterproof structure is a complex task from a Design for Manufacturing (DFM) perspective and achieving the required specifications during the Production Validation Testing (PVT) stage. We selected connectors with ratings no lower than IP66 and additionally provided sealing for the connectors using two intersecting contours of the seal. We designed and manufactured custom rubber seals for the enclosure and placed them in special channels.

In this project, we created a reliable enclosure that met the IP66 standard. To finalize the industrial design of the enclosure, we utilized 3D printing and silicone molding. After approving the final design, we developed and manufactured the molds. The project took 7 months, starting from the EVT (engineering validation testing) stage, through DVT (Design Validation Testing), and concluding with the PVT stage. As a result, the customer received a complete set of engineering documentation and a batch of enclosures.

Enclosure for the Marineo telecommunication system

Marineo is a unified information and telecommunications system that automatically analyzes vessel movement data and the surrounding hydro-meteorological conditions. This system allows for fuel consumption reduction while simultaneously enhancing maritime safety.

The system is used on the open sea, on the ship's deck. The deck is not the most protected part of the vessel and is exposed to seawater, ultraviolet radiation, vibrations, and sudden impacts. The enclosure must withstand all types of marine loads and protect the electronics inside. At the same time, the system is modular, so installation should be fast and require minimal additional tools.

In modular systems, it is not necessary to protect each element from external influences; only the external part of a specific module can be shielded.

The product should be considered as a combination of modules. In this case, it is possible to eliminate undesirable losses, such as additional loops, complex enclosure parts, and excessive mechanical processing. This approach also helps reduce assembly time for the modular system and ensure the required level of safety. In this project, we did not use expensive rugged connectors and cables to connect the modules together. We designed the system in a way that waterproofing is achieved by placing the modules in close proximity to each other and using inexpensive silicone gaskets. Silicone gaskets were chosen for their properties. Silicone is not affected by external negative factors, including UV radiation, radiation, and electrical discharges/fields. Another undeniable advantage of silicone sealing gaskets is their service life, which should be at least 35 years.

We created a unique fastening mechanism that securely connects the modules to each other. Additionally, modules are installed similarly to how a sandwich is assembled, through press connections. We sealed the modules together using silicone gaskets, thus providing the necessary IP-67 level of protection for the connection. We used an external antenna since the module enclosures are made of metal. The antenna was installed using a single external connector that meets the IP-67 standard for protection.

All modules underwent dust and waterproof testing and were delivered to the customer. The customer received 4 fully assembled modules ready for testing, configuration, and installation on the vessel. Furthermore, we provided a user manual for module usage and interconnection, as well as CAD files.

In closing

Developing an enclosure with an IP protection class requires any developer, be it a product design company or an independent engineer, to possess high engineering skills, understanding, and anticipation of nuances in the application field of the future device. The developer also needs equipment for prototyping and testing the manufactured devices. Considering the peculiarities and intricacies of designing dust and waterproof devices, their development is significantly more expensive than their unprotected analogues. However, investments in developing a device with a high level of IP protection can pay off in the long run. The customer will receive a device that will not fail in adverse environmental conditions or due to user negligence. This will help establish your company's reputation as a provider of high-quality and reliable devices.