This Door Seal Design Guide from Elasto Proxy provides engineers with an overview of six factors to consider when designing door gaskets for any industry. Whether you need seals for mobile equipment, ovens, tablet coating presses, gensets, or electronic enclosures, youll find what you need to get started.
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As you consider these six factors, we invite you to contact us to discuss your specific application.
Most door seals are made of medium-density sponge rubber. The compound, or type of rubber, must be able to withstand the environment to ensure reliable, long-term sealing. At Elasto Proxy, we use an acronym called MTAP to describe the four factors you need to consider:
For mobile equipment doors, EPDM and TPE are commonly used compounds. Both are weather-resistant, but EPDM costs less while TPE is recyclable and supports tighter tolerances. Oven doors use silicone seals while the door gaskets on tableting presses uses fluorosilicone instead. These are just a few examples.
Because most door seal design specifies a medium-density rubber, the durometer isnt as hard as a hockey puck or as soft as a pencil eraser. Instead, the durometer is somewhere in-between to support compression without compression set, the failure of a seal to bounce back when the door is opened.
The sponge rubber in a door gasket has a cellular structure with open cells that allow the passage of air and water, or closed cells that do not. Gaskets with flame resistance or EMI shielding are sometimes required, too. As we will see, the shape and dimensions of a door gasket also affect performance.
Before we move on, here are some questions for you to ask and answer:
Door gaskets need a bulb thats large enough to fill the gap between the door and the frame. This bulb must then compress enough for the door to close and seal. The gap size can vary between a doors four corners or edges, so youll need to take a few measurements and complete this calculation.
Average Gap Size + Compression Percentage = Bulb Size
First, calculate the average gap size. An easy way to do this is to place some modeling clay in each corner and then close the door. Next, insert calipers into the clay and record the measurement for each of the four corners. Add these numbers together and divide by four get the average.
Next, apply a compression percentage between 25% and 50%. This is the amount you want the door seal to compress. Do not apply more than 50% because over-compressing the bulb wont create a better seal and may cause compression set. If you need a more compressible rubber, use a softer material instead.
In summary, here are some key questions to ask and answer.
The position and design of the hinges also affects door seal design. Gaskets compress more on the hinge side because theres greater pressure. For best results, design the hinge plates so that they are more forgiving and wont place excessive pressure on the seal. This may require a hinge plate redesign.
Symptoms of improperly designed hinge plates include a flattening of the door gasket on the hinge side and a gap on the latch side. The solution may require moving the door panel outward on the hinge side to support proper compression. The goal is to achieve uniform compression along the entire frame.
The design and position of the locking system and the suspension of the door itself are also potential sources of seal failure. Locks and hinges that are misaligned, manufacturing defects, or assembly errors can all create zones with inadequate sealing force that may result in leaking.
For hinges, here are some questions to ask and answer:
Door seal designers also need to consider the type of corners (if any) that are needed. Some seals have corners with a 90° splice or joint. These gaskets are visually appealing but require four individual splices, which adds costs. Thats why some engineers specify an endless gasket with a single butt-splice instead.
Rounded or radiused gaskets require fewer splices but raise additional concerns. As a rule, a smaller bend radius requires a smaller seal. If you use a small radius with a large seal, kinking may happen and cause the seal to leak. When the radius on a door gasket is too tight, the seals corners tend to pop out.
Link to I-ECO
A more flexible gasket material can support a smaller bend radius, but youll need to balance this against all of the other factors in material selection. If youre unsure which bend radius you need, determine the minimum distance from the center point to the edge where the seal must bend.
Finally, remember that bulb trim seals a common choice in door seal design need rounded corners. Molding is the only bonding technique that can create these corners and is also recommended for gaskets with square corners that will be stretched or pulled. For square corners, you can also use these methods:
When it comes to corners, here are some questions to ask and answer:
There are several ways to fasten or attach door gaskets. The use of an adhesive backing is popular because it supports peel-and-stick installation. Clean surfaces are required, however. At Elasto Proxy, we use a high bond adhesive tape system (HATS) or can apply a pressure-sensitive adhesive (PSA) tape.
Fastening can also be achieved by pushing the seal over a flange that holds the gasket in place. Channel sets can be used in place of clip-on seals. The gasket is like a Christmas tree that, once pushed into the channel, has inverted branches that are self-gripping and hold the gasket in place.
Gaskets with raised contact points make it harder for water to pass between the gasket and the doors surface. For example, a D-shaped gasket with two small ears has a total of three contact points for enhanced sealing. Door gasket design can also support higher contact force if incoming pressure increases.
Here are some questions to ask and answer about fastening:
Finally, engineers need to consider the relationship between door gasket design and installation. If an installer starts in one corner and pulls the rubber toward another corner, you might hear complaints that the gasket is too big. But thats not the case. Rubber is elastic and can be stretched too far.
The right way to install a door gasket is to use two corners and meet in the middle. With large surfaces, install each end of a gasket in the corners and then at a center point. Then finish the job by installing the gasket from the corners to the center point.
If you need to reposition a HATS-taped gasket, you might be able to do it once (or twice if youre lucky) because the bonds are so strong. For best results, install these gaskets in a climate-controlled building instead of out in the field, where temperature and humidity may affect curing.
Sometimes during gasket installation, workers use the wrong tools (such as screwdrivers or wooden mallets) that can damage the rubber. With taped gaskets, a plastic roller can safely apply pressure across the seals face. PSA curing is instant, but HATS curing takes 24 hours under the right conditions.
Here are some questions to ask and answer about installation:
Buying finished gaskets from an experienced fabricator like Elasto Proxy can save you time and money in the end. Our solutions providers can help you with material selection, gap size calculations, and with design considerations that include everything from hinges and corners to fastening and installation.
Pre-fabricated gaskets can also help you to stop wasted movement and promote physical distancing during COVID-19. You can also combine highly-efficient custom fabrication with value-added services like kitting and assembly packaging.
Are you ready to learn more? Contact Elasto Proxy.
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