Understanding ISO Standards In Pneumatics

Post By: John Rowse On: 09-05-2024 Read Time: 5 minutes - Guides - Pneumatics

When choosing a pneumatic cylinder, you’ll see that some conform to ISO standards and some don’t. ISO-compliant pneumatic cylinders will always meet certain predetermined parameters, regardless of manufacturer, so brands are interchangeable. This gives you much more flexibility in cylinder brand selection when designing a pneumatic system. Non-ISO variants often feature the same basic standard components but with design variations intended to complement specific actuator systems.

What Are ISO Standards?

ISO standards are a set of universally accepted parameters, set up and endorsed by the International Organisation for Standardisation. The ISO is an independent organisation, made up of global experts who work together to agree on common standards for use in manufacturing and business. With pneumatic cylinders, ISO standards govern the dimensions of basic mounting types and accessories. It’s important to note that the purpose of ISO is only to standardise dimensional specifications, not to govern performance or quality. 

The demand for standardisation of machine and component dimensions was initiated by the automotive industry. They wanted to be able to choose between OEMs, so actuators needed to be dimensionally interchangeable. The standards that were devised for mounting interfaces and spatial envelopes also had to take into account the various styles and technologies used by different manufacturers to create the actuators – such as piston designs, bearings, seals and assembly methods. 

Understanding ISO Standards In Pneumatics

ISO Or Not ISO?

Understanding ISO standards in pneumatics is the key to devising the best pneumatic control equipment. There’s a vast range of cylinder types on the market, all performing the same basic function: to drive a piston using air pressure differential. Standardisation means agreeing on a core product that can be used in many different circumstances, but it also means compromise. 

Standardised products don’t allow for particular performance characteristics, or design features that provide a better end-solution, such as lower mass or a smaller spatial envelope. This is where non-ISO variants for pneumatic cylinders come in. This variety benefits manufacturers, allowing them to offer specific drives that cover the range of applications required by different customers. 

Choosing non-ISO-compliant actuators, however, makes it harder to change OEMs. For instance, if cylinder components wear out or become obsolescent, or end users' specifications change, finding alternatives could affect product costs or maintenance downtimes. ISO standards eliminate this difficulty both for manufacturers and end-users, with all necessary parts adhering to predetermined basic sizes and measurements.

ISO Standards Commonly Applied To Pneumatic Cylinders

ISO 6432 Round-Line Cylinder

ISO 6432 sets out the prescribed dimensions for round-line cylinders. This type of cylinder is lighter, with its mounting interfaces built in, and is suitable for simple applications like lifting, holding and moving. It typically comes in 8-25 mm diameters, although manufacturers frequently offer ranges in diameters from 80-100 mm larger than the defined standard. 

The versatile ISO 6432 cylinder uses long-lasting wear-resistant materials and comes with plenty of mounting options. This makes the ISO 6432 cylinder a leading product in customer satisfaction.

ISO 15552 Profile Cylinder

ISO 15552 outlines the key dimensions of one of the industry’s most popular cylinder types. It stipulates basic cylinder dimensions for bore sizes from 32-320 mm, together with mounting interface dimensions, nominal/recommended stroke lengths and dimensions for attachable accessories. It includes details on possible mounting options, accessories and cushioning methods. 

This type of cylinder features a longer distance between the piston and the nose bearing, which makes a robust design capable of managing side loads. The front end cap also has more space, providing many options for variants in bearing, seal and scraper specs.

ISO 21287 Compact cylinders

ISO 21287 applies to short-stroke or compact cylinders, which feature shorter pistons and front end-caps than 6432 or 15552 types, for the same working stroke. ISO compact cylinders are ideal where space is limited, but they’re not as robust as the standard profile cylinders and don’t cope well with side loads. 

Does Complying With ISO Standards Limit Your Choice Of Cylinder?

In a word – no. That is, they ought not to since manufacturers can offer additional attributes or functionality to products while still adhering to the core features and dimensions stated in the ISO standard. Such additional features might include clamping/braking units, or a range of sealing options to deal with special circumstances like higher or lower operating temperatures. Another example might be a standard ISO cylinder, adapted to absorb large side loads by using larger-diameter piston rod bearings.

Rowse’s official partner, Festo, offers several ranges of ISO-15552 cylinders that comply with the core standard dimensional specs, but its range also provides a choice of additional characteristics geared towards particular applications and industries. For example, the DSBC standard model has lifecycle and performance characteristics suited to most applications, plus two specialist variants. One is the DSBF model cylinder, designed for the food and beverage industry, providing FDA-compliant seals and greases and increased protection against corrosion. The other is the DSBG model cylinder, featuring a tie rod construction often used in automotive applications.

Festo has also expanded the range of its popular DSNU round-line cylinders. This ISO 6432-compliant model offers standard barrel and rod material, but a new non-ISO space-saving variant is now available, the DSNU-S. Both versions offer production volume efficiencies, but the DSNU-S compact variant is designed for relatively small loads carrying out simple, linear movements. It’s up to 35mm shorter, 40% narrower, and lighter than the ISO equivalent, making it a good choice for increasingly space-dependent industries like lighting assemblies and electronics. 

Must You Use Only ISO Standard Products?

You’re not restricted only to specifying and using ISO-standard pneumatic cylinders for your pneumatic systems. While there are many benefits from standardised products, ISO-standard pneumatic cylinders can’t cover every eventuality without help. For instance, the electronics and medical device sectors are continually under pressure to miniaturise. This means that pneumatic actuators become even smaller and more compact – specifications that might be better served by using non-ISO cylinder variants.