Product Spotlight

What You Need to Know When Selecting a Micro-Miniature O-Ring


For many industries today, technology and designs have become smaller and more precise. This can pose a variety of challenges for design engineers, especially the tight tolerances required for microminiature sealing applications. To meet the increasing demands for effective seals in precise, miniature applications, Apple Rubber developed the MicrOring.

A MicrOring seal constitutes as any o-ring measuring less than 1 mm in inside diameter or cross section. While MicrOrings were designed for a variety of applications, including precision instruments, medical devices, aerospace and fiber optics, there are still important factors to keep in mind when designing a micro-miniature o-ring. Here’s what you need to know before selecting your MicrOring seal:

Pay attention to pressure.

Microminiature designs leave little room for inaccuracies. This means designs must be as precise and tight as possible. Paying attention to outside factors, like pressure, is crucial when selecting a seal for any application.

Sealing environments vary from low to high pressure depending on the application. In low-pressure sealing applications, the system pressure is often too low to activate the seal to fill potential leak paths. This means that the design must rely solely on the resilience of the elastomer to retain the needed sealing force. Conversely, in high-pressure sealing applications, the system pressure does activate the seal. However, material hardness and hardware clearances need to be monitored to prevent potential seal extrusion. Paying attention to sealing pressure before selecting an o-ring is important to ensure the right material and design are chosen to handle your application.

Understand tolerance stack-up.

Tolerance stack-up combines the tolerance of the seal, piston and bore. MicrOring sealing requires all components to have higher precision and hold very stringent tolerances. This is especially important because tolerances account for a large percentage of the nominal o-ring size. If the total stack-up approaches the nominal o-ring size, the seal could fail from too much or too little squeeze.

When considering tolerance stack-up in a seal design, the general guideline is to maintain a range of percent compression (10-40% for static sealing and no more than 30% for dynamic seal applications). The minimum groove width volume should exceed the maximum o-ring volume by at least 10% to account for temperature and volume swell. Since there’s little room for error, it’s extremely important to pay attention to detail in microminiature sealing applications.

Material selection is critical.

As in any sealing application, material selection is a key factor in the design process that determines the strength and efficiency of your seal. MicrOrings are no exception to this, especially because of the increase in demand for new and more advanced applications. At Apple Rubber, research is constantly in the works to find new materials and durometers to keep pace with the rapidly changing needs in today’s microminiature designs.

MicrOrings can be produced in a variety of different materials, including nitrile, ethylene-propylene, silicone, neoprene®, fluorocarbon® and fluorosilicone. Each material offers different benefits that make them the right choice for specific applications, from oil resistance to high and low-temperature stability. Since materials differ in the environments they can handle, choosing the correct material for your sealing application is critical to prevent seal failure.

Apple Rubber offers the widest range of o-ring sizes in the industry, with MicrOring sizes available as small as .008” inside diameter. Apple can custom engineer any sized o-ring seals for prototypes or full production runs.


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