FEATURE HYDRAULICS & PNEUMATICS A guide to:
ISO StandardS and prOduct SelectIOn
ISO standards-based actuators are a
Examples of ISO cylinders T
he International Organisation for Standardisation (ISO) is an independent body which creates common standards
agreed by global experts for business use around the world. 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. While standardisation results in good all-
round products suitable for many standard applications, it can compromise specific features or performance characteristics that offer advantages in terms of performance or function. So, how can we decide whether an ISO or non ISO cylinder is our best option?
understAnding iso
ISO standards ensure that pneumatic cylinders and their associated mounting components and accessories adhere to defined basic measurements and sizes, making life easier for both manufacturers and their customers. For example, 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. There are a number of ISO standards specific
to pneumatic cylinders: • ISO 15552:2018 profile cylinders are one of
the most popular cylinder types in industry. The standard provides basic dimensions for the cylinder, along with bore sizes; in this case from 32mm to 320mm. There are given dimensions for the mounting interface and attachable accessories as well as nominal/recommended stroke lengths. The standard also details the types of mounting options, accessories and cushioning method. There are many options for scraper, seal and bearing variants providing options to cope with different demands or running characteristics. • ISO 6432 sets dimensions for round-line
cylinders in diameters of 8mm to 25mm, although manufacturers frequently offer ranges up to 100mm beyond the defined standard. Lighter weight and with built-in
5 DESIGN SOLUTIONS OCTOBER 2021 0 Examples of non-ISO cylinders
mounting interfaces, the ISO 6432 cylinder is a versatile product that is commonly found in simple moving, holding and lifting applications. It uses wear resistant materials, providing a longer service life, and multiple mounting options give it added flexibility. • ISO 21287 applies to so-called compact
cylinders or short stroke cylinders. Using short pistons and front end-caps, they are considerably shorter for the same working stroke than the examples above. ISO compact cylinders are an excellent choice in applications where space is at a premium. However, this comes with a trade-off: they will not be as robust as the standard profile ISO 15552 cylinders and generally should not be exposed to side loadings.
do iso stAndArds limit Product choice?
Although manufacturers must adhere to the dimensions/features provided in the ISO standard, they are able to add further functionality or attributes to the cylinder. So, specifiers and end-users are not restricted to only using ISO standard pneumatic cylinders to solve automation challenges. 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. We have several ranges of ISO 15552 cylinders complying with the standard, but with additional characteristics which support different industries and their applications. The Festo DSBC is the standard workhorse,
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 our 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 with the standard model. However, the non-standard DSNU-S is a space
cornerstone for most manufacturers of pneumatic control
technology and are a popular choice for
machine builders across industry sectors. Here, Steve Sands, head of product management at Festo, guides us
through the standards and examines
whether they limit product choice
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 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.
Product selection
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 complimentary non-ISO variants is therefore essential for smooth product selection.
Festo
www.festo.co.uk/pneumaticdrives
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