Manufacturing Waterproof Plastic Product: A Simple Guide
- Gavin Leo
Almost all products around you are in some way waterproof. The key here is to understand waterproofing has been divided into many levels and ratings. So your phone might not have the same level of waterproofing as a diver’s watch but it can still withstand rain.
So, how do designers ensure waterproofness? And how can you choose an IP rating for your plastic product? And how can you offer a plastic enclosure that can make something waterproof, like the many phone and camera cases you see?
In this guide, we’ll share the best waterproof design principles for your plastics, key advice from a dozen product developers, and a detailed example project to help you get started.
What's an IP Rating?
In pure technical terms, IP rating stands for Ingress Protection (IP) rating. This is an international system that defines the level of waterproofness.
It tells us how effective is the seal against an ‘ingress’ or entry of a foreign object usually liquid or water.
What Are The Digits In an IP Rating?
IP ratings follow a two-digit code. In general and always, the higher the digits, the better the protection against water.
The first digit tells you the protection against solid objects. This can include dust, powder, sand, grains, etc and the second digit tells you the protection against water and moisture.
For protection against solid objects like dust and fingers, the rating ranges from 0 – 6. With 6 being the best protection and no ingress of dust.
The second digit goes from a scale of 0 – 9. Most everyday electronics are rated 7 and 9 is the highest IP rating against water ingression. It means your plastic enclosure can resist hot water streams from different angles.
What Are The Waterproof IP Ratings?
On most waterproof plastic products, you will find IP ratings for different levels. IP 67, IP65, IP66, and so on. To protect against water only, you can find waterproof IP ratings like IPX6, IPX7.
Here’s a complete breakdown of the waterproof IP rating levels and what they mean.
IP Rating
Level of effectiveness
Product Example
IP X0
Not effective against water
Computers and printers
IP X1
Effective against vertical water showers or drops
Lights and bulbs
P X2
Effective against vertical water showers or drops up to 15 angles.
Kitchen appliances
IP X3
Effective against water spray up to 60 angles.
Electrical enclosures
IP X4
Effective against water splashes
Solar panels
IP X5
Effective against strong water jet streams from all direction
Cameras and doorbell
IP X6
Effective against powerful water jets
Navigational devices
IP X6K
Effective against powerful water jets while being pressured
Industrial equipment
IP X7
Effective when the object is submerged in water up to 1 m
Apple phones and electronics
IP X8
Effective when the object is submerged in water up to 1 m and water may enter but produce no damage
Action cameras like GoPro
IP X9
Effective against hot water jets from all angles
Car sensors
Waterproof Industrial Design Guide For Plastic Enclosure
When designing plastic electronic enclosures it is important to make it as purposeful as possible.
Once you have an enclosure design that follows all your dimensions and houses all the electronics, we can work on optimizing the design for waterproofness.
Material Selection
Selecting the right plastic for the product is important. You have to make this choice according to the final application of your product. ABS plastic is a popular choice for plastic products that need strength.
Polycarbonate (PC) is another plastic for enclosure boxes and has the advantage of being transparent. However, PC can yellow over time under the sun.
The choice of material depends on the environment and durability of the product’s design.
At the design stage, you can work with any plastic, even PLA to 3D print your parts. At the prototyping stage, you can finalize the material.
Let’s focus on the industrial design of your plastic product.
As an example, we will work with a simple plastic enclosure box.
Optimizing Corner Design
When you have a two-part design that requires assembly, you should avoid sharp corners. From a design perspective:
Fitting seals into sharp corners is difficult
Sharp corners make your plastic product prone to cracking and chipping on impact
For injection molded products, sharp corners cause plastic flow issues.
Effective Assembly Strategies
The plastic enclosure needs joining. In standard metal parts, we have a range of bolts and screws which can hold them together. However, water can seep through the tapped holes and threaded bolts.
In most plastic designs, screws are generally avoided. If your design must use a screw, you can use rubber and silicone washers to add to the waterproofing and distribute stress so the screw head doesn’t damage the plastic.
You can also use a flanged hex head or sealing TORX head screw that comes with a pre-installed silicon washer.
Sealing The Plastic Enclosure
Screwing your plastic product shut ensures waterproofness. However, water jets from the side or other angles can leak into the container. You must use advanced seals to achieve higher IP ratings like IPX6K and IPX7.
O-rings
O-rings are round rubber seals with a circular cross-section. They are designed to stretch over a cylinder or fit into an aperture to make the product dust-tight and protect against water ingress.
Static O-rings
Static O-rings are used when the water seal is around a component that produces no motion.
Dynamic O-rings
Dynamic seals occur when two components move, turn, or rotate relative to each other
O-rings have a slight tension and can be damaged or cut during enclosure opening and closing. They are great for small plastic products and small—to medium-scale production.
Gaskets
Gaskets work great for two-part designs and mating objects. Custom gaskets are placed between the spaces where the parts meet, making waterproof assembly simpler.
Gaskets are larger than washers and O-rings which ensures better and more rugged watertight seals.
Overmolding As a Reinforcement for Gasket Control
A gasket can make your product IPX6K, IPX7, and IPX8 rated. In manufacturing, over-molding a gasket is the standard.
The gasket is directly incorporated around the rigid plastic base and this eliminates the need to manually install the gasket into the assembly.
Overmolding offers additional benefits
- No visible seams
- No water penetration
- Cost-effective for high-volume production runs
- No adhesives and glues like O-rings
Overmolding for Gasket
- High tooling cost
- Design changes and additional complexity
- Shrinkage can result in gaps
Distribution of Fasteners for Higher IP Ratings
Fixing distribution means the spread and distance between your fixings like screws or rivets.
Small equipment: For small plastic products, you can use a spacing of around 4-10 cm.
Medium-large equipment: On average medium-sized products like security cameras and junction boxes use 12 cm spacing and large plastic products can have spacing between 15 cm to 20 cm.
The general recommendation to protect against weather elements is always to use smaller spacing.
Button Design
The easiest way to use a button in your waterproof design is to cover it with a membrane. This waterproof membrane allows the button to be actuated but prevents water ingress.
Usually, buttons are made from a softer material. If you plan to use the same or harder materials as the surrounding plastic, you can add an O-ring to your assembly to prevent liquid from entering it.
You can use capacitive buttons which remove any physical button movement, removing any sealing needs.
Waterproof Prototyping Recommendations
When designing any waterproof enclosure or housing you can quickly 3D print your product to test the screw hols, mating fit, and gasket placement. You don’t need to prototype using high-quality ABS material types or go to tooling design. You can use a standard PLA or Nylon print.
Testing Your Prototype
The next page in our prototyping guide is testing. You should not use any soft plastic housing for waterproof testing. To test your prototype make sure you are using ABS, PVC, or PTFE plastics.
You can run a dummy test with the empty enclosure and place color-changing tape inside to detect water ingress. After this successful test, you can house your electronics and test your prototype again.
Tips For Manufacturing Waterproof Products
Manufacturing considerations prevent production issues at the manufacturing stage. Here are a few tips to help you avoid many beginner mistakes.
Use a good machined surface finish: This is important if your housing uses pressurized seals. Seals work by forming a tight barrier between mating surfaces. If your surface quality is rough, you will have fitting issues.
Use simple geometry in your designs: Unless extremely necessary, always simplify your design to make use of standard O-rings and readily available gaskets.
Use proper gasket glands: Gasket glands are grooves in which a gasket typically sits. Groove dimensions need to match gasket dimensions so the gasket leaves no gaps.
The grooves should extend to provide lateral support.
In high-pressure seals or when the compression force is large a gasket can flow out. To avoid this, use narrow groove openings.
Use heat sealing: You can heat seal thermoplastic material. This involves using weights or pressure and a heat gun or heat sealer to apply heat to the mating surface in a controlled manner.
Applying pressure to both pieces and leaving the product to cool results in an airtight and water-tight seal. This is a permanent joining method.
Conclusion
Waterproofing has many marine and military applications. Often the highest IPXX ratings used for technical military gear prevent all liquids from entering. Waterproof enclosures, housing, and electronic boxes are commercial applications of the same concept.