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ISO standards in pneumatics – what you need to know

ISO standards in pneumatics – what you need to know

Steve Sands, head of product management at Festo, offers some pointers on the significance of ISO standards in pneumatic actuator development and their role in machine design.

ISO standards-based actuators are a cornerstone for most manufacturers of pneumatic control technology and are a popular choice for machine builders across industry sectors. The initial demand for standardised dimensions was driven by the car industry seeking dimensionally interchangeable actuators from alternative suppliers. The space envelopes and mounting interfaces agreed within the standards had to allow for the many different manufacturers’ technologies and assembly methods.

Inevitably this approach involves compromises to specific features or performance characteristics but creates a good all-round product suitable for many standard applications. However, certain industries and applications may have a greater need for a specific functionality or feature, like a reduced size envelope or lower mass: features which provide them with advantages in terms of performance or function, for a better end-solution. These types of applications can benefit from the use of non-ISO pneumatic cylinder variants.

In the world of pneumatic cylinders, the ISO standards refer to basic mounting and accessories dimensions, which enable the interchangeability of pneumatic cylinders regardless of manufacturer. They lay down a framework for the development of standardised products. There are numerous manufacturers and suppliers of pneumatic cylinders globally, and each creates their own styles of cylinders, with individual space envelopes and mounting interfaces.

This provides a huge variety of cylinder types in the market, all fundamentally doing the same thing – a piston with an output connection is forced up and down a tube by a pressure differential. This variety is beneficial for manufacturers because it enables them to produce differentiated product which may be smaller, faster, stronger – providing customers with drives that suit their particular application.

Standardisation reduces time during the machine design process, a significant benefit when you consider that pneumatic cylinders are a very common component within many machinery designs. Selecting non-ISO compliant actuators, on the other hand, can mean it is harder to switch between suppliers – for instance to meet different end-users’ specification or in cases of obsolescence or breakdown.

But do ISO standards limit product choice? The short answer is no – or at least: no, they shouldn’t. Though manufacturers must adhere to the dimensions/features provided in the ISO standard, they are able to add further functionality or attributes to the cylinder. Examples of this could be different sealing options to accommodate particularly lower or high temperatures, or clamping/braking units. Another example might be a non-ISO stopper cylinder, based on a standard cylinder but with over-sized piston rod diameter and bearings to absorb large side loadings.

Yet while standardised products bring many benefits, there are also applications that are not optimally served using ISO standard pneumatic cylinders alone. For example, the continuing pressure to miniaturise within the electronics sector demands ever smaller and more compact pneumatic cylinders. A non-ISO cylinder variant could be much more suited for this type of application.

ISO versus non-ISO products

So how do ISO and non-ISO products compare? It is critical to remember that ISO is about dimensional standardisation and not an indicator of quality or performance.

Let’s use the Festo product range to illustrate the point. Festo has several ranges of ISO 15552 cylinders (DSBC, DSBG and DSBF) complying with the standard, but with additional characteristics which support different industries and their applications. DSBC is the standard workhorse, first out of the bag and with performance and long-life running characteristics for most standard applications.

The DSBF, is a specialist variant for the food industry that features increased corrosion protection and FDA-compliant greases and seals. DSBG uses a tie rod construction specified in some automotive projects.

DSNU is Festo’s ever-popular ISO 6432 round-line cylinder. This year it has been supplemented with a non-ISO variant the DSNU-S. For production volume efficiencies, it shares barrel and rod material – but the new DSNU-S is a space optimised variant, created for simple, linear movements with relatively small loads. It is up to 40% narrower, lighter and up to 35mm shorter than its DSNU ISO equivalent, making it easy to install in tight spaces.

Its compact nature makes the DSNU-S a good choice for industries like electronics and light assembly, where the space footprint reduces year on year. Savings on materials and the latest fully automated production also enable manufacturing cost reductions to be passed on to the user.

ISO standards play an important role in making pneumatic cylinders interchangeable and giving design engineers and machine builders the freedom to choose.  Understanding ISO standards and the benefits of complementary non-ISO variants is essential for smooth product selection.


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