How to Select a Cleanroom Electric Actuator and Compare Manufacturers

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Designers who are designing an automatic machine to operate in a clean room for the first time may have a hard time selecting an electric actuator.　　While they are important components that directly affect the quality of products such as semiconductors and pharmaceuticals,Many manufacturers offer products with a variety of characteristics, and the selection process is not easy.

Although many websites introduce products from various manufacturers, it is difficult to gain a deep understanding of whether the products truly meet your company's required specifications and their technical backgrounds simply by comparing catalog specifications side by side.

Particularly,Currently, there is little information that provides a comprehensive explanation of the specific differences between each company's low-dust technology and the points that really need attention in operation after introduction.It is.

Therefore, this article will start with a correct understanding of the ISO class that indicates the cleanliness of a clean room, and then make a comprehensive comparison of each manufacturer's product, finally selecting a product that meets the required specifications, and noting the precautions to maintain its performance over the long term, from design to operation with awareness.

Basics and Selection of Cleanroom Electric Actuators

In selecting electric actuators for use in cleanrooms, the basic knowledge that must first be understood and the core technologies that determine their performance will be explained.

What is ISO class for cleanliness?

A clean room is a space where airborne particles are controlled below a specified cleanliness level.

The international standard for cleanliness is ISO 14644-1.　　The designer must first accurately determine the cleanliness class required for the environment in which his or her equipment will be installed.m^3), with classes defined by the number of particles of a particular size in the air,The smaller the class number, the higher the cleanliness.

For example, extremely high levels such as ISO Class 3 are required for cutting-edge semiconductor manufacturing processes, while ISO Class 7 or 8 may be the standard for general pharmaceutical or food manufacturing.　　In the past, the U.S. federal standard "FED-STD-209E" was widely used, and designations such as "Class 100" and "Class 1000" were common.　　Although this standard was abolished in 2001, it is still customarily used today, so it is best to refer to the table below to understand the correspondence with the ISO standard.

Table 1: Class correspondence table between ISO 14644-1 and former US Federal Standard FED-STD-209E

How the actuator becomes a dust source

Electric actuators are indispensable for automated equipment, but their structure itself contains factors that generate particles and can be the largest source of contamination in clean rooms.　　Understanding the mechanism of this dust generation is the first step in selecting a product with appropriate countermeasures. The main sources of dust emission are as follows

• Dust emission due to mechanical wear:When the balls and rollers of linear guides and ball screws roll along rails and threaded grooves, metal-to-metal contact generates fine wear particles. This is a phenomenon that is difficult to eliminate completely as long as the machine is in motion.
• Lubricant splatter:Grease and oil used to lubricate guides and ball screws may become tiny particles and scatter around the actuator when the actuator operates at high speeds due to centrifugal force and other factors.
• Friction of cables:Cables connected to motors and sensors are often housed and protected in cable carriers (cable bearers). However, as the cables rub against each other and against the carriers during the reciprocating motion of the actuator, the sheath material wears away, causing plastic particles to be generated.

How to keep particles out of these dust sources determines the performance of clean-room compatible actuators.

Importance of low-dust grease and seal construction

There are three main approaches to technologies for controlling dust emissions from actuators: suppressing the generation, containing what is generated, and aspirating what leaks out.　Among them, low-dust grease and seal construction are important technologies that are fundamental to many clean-spec actuators.

Adoption of low-dust grease

This is the core technology of our approach to suppressing the source of particles themselves.　　Cleanroom grease differs from general industrial grease in that it has low vapor pressure and high viscosity, characteristics that make it difficult to scatter even during high-speed operation.　　In addition, the use of synthetic oils and fluorine-based materials as base oils suppresses the generation of gaseous impurities (outgassing).AFE-CA grease by THK　and ... andNSK's LG2 grease　The following are typical examples.

Containment by sealing structure

The sealing structure is a technology to prevent particles that have been generated inside from leaking to the outside of the actuator.　　In many products, the opening created when the slider moves is covered with a thin stainless steel plate (seal sheet or seal band).　　This sealed structure effectively prevents contaminated air inside from leaking out.　　This can be considered a basic specification for products that are designed for medium or higher cleanliness.

Cleanliness maintenance performed at the suction port

The most aggressive dust control measure used to achieve higher levels of cleanliness is the use of suction ports (vacuums).

This refers to a system in which a factory exhaust system is connected to the suction joint on the actuator body to forcibly suction the inside of the actuator.　　By keeping the inside of the actuator under negative pressure at all times, particles are prevented from leaking out through gaps in the seal structure, and even minute amounts of particles generated inside the actuator are discharged through the exhaust line.

As a precaution, many manufacturers specify in their specifications that "suction through the suction port is mandatory" as a condition for achieving high cleanliness levels such as ISO Class 3 or 4.　This is not only the performance of the actuator itself,It means that the performance according to the catalog specifications can be achieved only in conjunction with the equipment in the factory where it will be installed.The designers must therefore check the specifications of the actuator as well as whether it can provide the suction flow required by their facility infrastructure.　　Therefore, designers need to check the specifications of the actuator as well as whether it can provide the suction flow rate required by their facility infrastructure.

Cleanroom Electric Actuators by Major Manufacturers

This section describes specific product series and their respective features of cleanroom-compatible electric actuators offered by major Japanese manufacturers.　　Understanding the strengths and target markets of each company will help you improve the accuracy of your product selection.

Table 2: Summary of Cleanroom Compatible Electric Actuators by Major Japanese Manufacturers

IAI Products and Supported Classes

IAI Corporation has a high market share in the field of small industrial robots and is an industry leader in cleanroom-compatible products.

We have a very wide lineup of products, mainly slider types but also rod and rotary types, including the clean room version of our main product, the "Elecylinder," the "RCP6CR Series" with a pulse motor, the "RCS4CR Series" with an AC servo motor, and so on.The most significant feature of IAI products is that some models achieve an extremely high level of cleanliness, ISO Class 2.5, the highest level in the industry.

To achieve this, multiple technologies are employed in an integrated manner, including a sealed structure with stainless steel sheets, internal air suction, a roller structure to reduce sliding resistance, and special low-dust grease.　　It is an excellent choice for environments that require extremely high cleanliness, such as cutting-edge semiconductor processes.

Features of THK's Clean Series

THK Corporation, a pioneer in linear motion guides, leverages its fundamental technology to provide high-performance cleanroom actuators.

The products are deployed as the "Clean Series" and generally correspond to ISO Class 4.　　Importantly, it is clearly stated that suction from a suction fitting is mandatory to guarantee this performance.　　Technical,Features a full-cover structure with a unique seal sheet and in-house developed low-dust grease "AFE-CAThe two series are the CSKR/CGL series with higher performance "low dust emission structure" and the CKSF/CKRF series with standard "simple clean structure.　　In addition, to allow selection according to required specifications, they are classified into the CSKR/CGL series with higher performance "low dust emission structure" and the CKSF/CKRF series with standard "simple clean structure," allowing selection based on a balance between cost and performance.

SMC's clean specification actuator

SMC Corporation, a leading manufacturer of pneumatic equipment, also has an extensive product line in the field of electric actuators, offering the "Clean Series" for clean rooms.

The slider type "LEFS Series" and the "LEJS Series" featuring low profile and high rigidity are compatible with clean specifications and can achieve ISO Class 4.　　These products are equipped with a seal band as standard to prevent grease splashing and foreign matter from entering from outside, and a suction port is provided to achieve a high level of cleanliness.For users who make extensive use of SMC products in pneumatic equipment, there may be an advantage in the high affinity of control systems and accessories.

Oriental Motor's EZS Series

Oriental Motor Co., Ltd. with its strength in motor and control technology, has added a clean room compatible model to its EZS series of motor-integrated actuators.

This series achieves a high degree of cleanliness, ISO Class 3.It should be noted that the conditions for achieving this performance are specifically numerical.　　For example, the EZSM3 model specifies that "an internal suction volume of approximately 20 L/min or more" is required,Provides very clear technical information for designersThe company has been working on this project for the past several years.　　Such a quantitative approach offers significant advantages in reducing uncertainties during the design phase and increasing overall system reliability.

NSK's monocarriers and proprietary technologies

(NSK), a globally acclaimed manufacturer of bearings and ball screws, has applied its elemental component technology to develop unique products.　　The main product is the "Monocarrier," a single-axis actuator integrating a ball screw and linear guide, for clean applications, which meets the former FED Class 10 standard (equivalent to ISO Class 4).

NSK's strength lies in its lubrication technology, and in addition to the low-dust grease "LG2" and "LGU" developed in-house, the company has proprietary technologies such as the "NSK K1" lubrication unit, which uses lubricant-impregnated resin to achieve long-term maintenance-free operation.　　In recent years, we have developed a "low dust emission/decontamination actuator" that can also be used for decontamination with hydrogen peroxide for new markets such as regenerative medicine and aseptic manufacturing.

CKD's actuators for low-dust environments

CKD Corporation is a manufacturer of a wide range of automation components, from pneumatic and fluid control devices to electric actuators.　　A variation for "low-dust environment" is available in the "EJSG Series" slider type of electric actuators, and some products are ISO Class 3 compliant.

The full-cover structure and suction port are the basic features,Another feature is the flexible design that allows installation of motors from a wide variety of manufacturers.　　The P5/P7 series is also known as the company's clean-ready equipment.

Yamaha Motor's Clean Room Robot

Yamaha Motor Co., Ltd. has a long track record in industrial robots and provides the robot system itself as a high-performance actuator.

Cleanroom-compatible models are available in the single-axis robot, Cartesian Coordinate Robot, and SCARA robot categories.In recent years, the SCARA Robot "YK-XEC" series has expanded its product lineup with the addition of a clean type.The actuator is designed to be clean.　　Yamaha Motor products are designed for clean performance of the entire system rather than the actuator alone, and feature a design concept that prevents dust generation through a "highly sealed structure" and at the same time improves air intake efficiency.

Cable Bear Selection and Maintenance Considerations

Even if a high-performance clean actuator is selected, its performance will not be fully realized if the peripheral equipment is not managed and maintained properly.　　This section describes the selection of cable bearers, which are often overlooked, and their maintenance to maintain performance over the long term.

Often overlooked dust source: cable bearers

As mentioned above, particles are generated when cables and cable carriers (cable bearers) rub against each other as the actuator operates.

Failure to take this countermeasure may compromise the clean performance of the entire system. As a countermeasure, it is essential to select dedicated cable bearers of low-dust type.　　These products use materials with excellent abrasion resistance and a structure that suppresses sliding, and some are available for ultra-high clean environments such as ISO Class 1 and 2.　　It is also important to use partition plates (separators) to prevent cables from wearing each other inside the carrier and to arrange them in an orderly manner.

Maintenance to maintain performance

The performance of cleanroom-compatible actuators is maintained through proper maintenance.

Lubrication management, in particular, is the most important process in maintaining its performance.　　The biggest caveat is that standard industrial grease should never be used during maintenance.　　If general-purpose grease is applied, the actuator's inherent low-dust performance is immediately and irreversibly lost.　　As a result, the actuator becomes a source of contamination, which can lead to serious product failure.

When performing maintenance, always use cleanroom grease specified by the manufacturer.　　Before starting work, shut off the power to the equipment, carefully wipe off the old grease with a clean wipe, and apply a thin, uniform coat of new grease.　　It is then recommended to manually run the slider back and forth several times to blend the grease.　　The frequency of greasing depends on the conditions of use, though,The general rule of thumb is every 100 km of mileage or 3-6 months.

Choose the best cleanroom electric actuator!

In this article, we have described the knowledge required to select and operate electric actuators for use in cleanrooms. Finally, we summarize some important points.

• Cleanliness of clean rooms is defined by the international standard "ISO 14644-1
• Understanding the required ISO class is the first step in the selection process.
• Actuators are a source of dust due to mechanical wear and splashing lubricant
• Friction between cables and cable bearers is also a non-negligible source of dust generation
• The basic technology for low dust emission is "low dust emission grease" and "seal structure.
• Low-dust grease inhibits particle generation itself
• Sealing structure does not leak generated particles to the outside
• Forced exhaust by "suction port" is essential for higher cleanliness
• Suction port performance is achieved in conjunction with the plant's exhaust system
• IAI offers a wide range of products of the highest standard, including ISO Class 2.5 compliant
• THK and SMC have a balanced product offering in the ISO Class 4 market.
• Oriental Motor's strength is in providing quantitative information, such as specifying suction volume.
• NSK's proprietary lubrication technology, NSK K1, provides superior ease of maintenance
• CKD and Yamaha Motor also offer clean-response products that leverage the strengths of each company.
• Selection of low-dust type cable bearers as peripheral equipment is important.
• Always use clean grease specified by the manufacturer for maintenance
• Use of commodity greases risks irreversible loss of low dust generation performance

That's it.