How Can I Know If a Given Actuator Is Suitable for Use in a Specific Environment?

All too often, design engineers choose actuators in isolation, without sufficient consideration for where they will have to “live.” Linear actuators have critical moving parts that will only work properly within the environment for which they were designed and manufactured. Using an inappropriate linear actuator can cause issues ranging from improper operation to irreparable damage to the actuator itself.  For “dirty” applications, such as a cutting tool that produces particles or scrap, the actuator will require sealing and shielding to protect it from contaminants.

From the opposite perspective, an actuator without the proper rating can introduce contamination into a clean environment, compromising the application. Normal wear and tear will cause linear stages to produce particulates over time. Cleanroom or in-vacuum environments often require the use of equipment that releases zero particulates, so it is critical that the actuators used in these environments are equipped with seals and shields to stop particulates from entering the environment. Some linear mechanics, such as in semiconductor processing applications, are moving only microns at a time, so even the least amount of contamination can compromise and ruin an application. Seals and shields can protect critical components from exposure to harsh environments, allowing the linear actuator to run as it was designed to perform. For clean environments, the seals and shields are designed to protect the application’s environment from possible contaminants produced by the actuator, not the actuator itself. In addition to seals and shields, custom linear actuators can be designed with positive pressure ports that allow purging unwanted contaminants inside the unit, keeping the performance and life cycle at a maximum.

A variety of environmental factors must be considered when choosing a linear actuator for an application. These include the ambient temperature, the presence of moisture, exposure to gases other than room air or other chemicals, radiation, the level of air pressure (for applications that are performed in vacuum), cleanliness, and other nearby equipment. For example, is there another piece of equipment in the vicinity that could transfer vibrations that would affect the performance of the linear stage? 

A linear stage’s Ingress Protection (IP) rating, which is typically provided in its specifications, indicates whether it has the proper protection from its environment. IP ratings are defined levels of sealing effectiveness of enclosures against intrusion from foreign bodies (dust, dirt, etc.) and moisture. An enclosure rating takes the form of "IP-" followed by two digits. The first digit indicates the degree of personal protection from moving parts and the level of protection from foreign bodies. The second digit identifies the level of protection against exposure to moisture (drips, sprays, submersion, etc.). 

More information on IP ratings can be found in the ANSI/IEC 60529-2004 standard.

Taking the time to check an actuator’s IP rating early in the selection process offer a quick and easy way to eliminate units that are unsuitable for the environment.  For example, an actuator with an IP30 rating can’t offer any protection against moisture, but it does have intrusion protection against finger-sized objects. Where moisture protection is essential, look for an actuator with a higher rating, such as IP54, which offers protection against both dust and water splash. Actuators without intrusion or moisture protection, however, can offer economical alternatives for environments where these issues are not a concern.