It is well known that the technicians and experts of Catas, the most important European laboratory in the wood-furniture sector, are members of many commissions inside different international standardization bodies. But it is surely less known that some of the necessary equipment supporting the measuring instruments, defined by the standards, have been realized by the Engineering Division of Catas.
The story begins in February 2017, when Iso (the International Organization for Standardization) publishes the standard “Iso 24496 – Office furniture – Office chairs – Methods for the determination of dimensions”, which is also the basis of the draft European standard (revision of EN 1335-1) on the test method for determining the dimensions of office work chairs, published after a long work by a large team of ergonomists and technicians coming from industries and international laboratories. This standard, a document of 72 pages, completely changes the way of measuring the dimensions of office chairs, introducing a totally innovative equipment, the “Chair Measuring Device” or simply Cmd. The Cmd is a sort of mannequin thanks to which it is possible to apply the correct weight in the right positions, simulating the encumbrance and the pressure profile of the seated person. At the same time, it allows to detect precious information, thanks to the measuring instruments integrated in the same dummy.
Once the way of measuring was found, the correct positioning of the “Cmd” on the chair under test remained an open question to be improved. This problem was solved by Catas technicians, who designed and built a special equipment that, in fact, became an integral part of the same standard for the correct execution of the tests.
We are talking about a standard that has a recognized worldwide value being, consequently, a reference tool for a population of users with very different physical characteristics. An extremely delicate subject, which adds to the old question of the “measurement uncertainty”. This means that all the many possible variables, that interfere with the data collected, must be taken into due consideration if the validity of a data is to be established.
A topic that Catas has decided to face several years ago, defining and creating a round robin test – the first and so far, unique in this sector – to collect all the “uncertainty data” derived by different measurements carried out on the same product in different laboratories and by different operators. Five office chairs have been sent to fifteen laboratories around the world, a journey of 13 thousand kilometers to try to measure the imponderable, the differences between the measures we have just described. It took three long years to collect all the data into a study that was then accepted by ISO, the global standardization body, to improve the current measurement standards at the international level.
An experience that has proved to be really precious for drafting the Iso 24496 standard: Cen has in fact asked Catas to organize at its headquarters in San Giovanni al Natisone the meeting of different technicians coming from nine international laboratories that carried out “double measurements” on the same samples represented by three different models of office chairs. The results obtained were compared with a similar study carried out in North America – as punctually analyzed and explained in the “paragraph 6” of the standard – obtaining a “table of measurement uncertainties” of which it is easy to understand the scope and implications.
The “dummy” and this data now allow anyone who wants or needs to carry out dimensional tests on office chairs to have access to important information about the quality of the results obtained.
