Old rules UNE under new GPS philosophy: standards in ISO 286-1/2: 2010

During the year 2010, new standards UNE EN ISO 286-1 have been published [3] and UNE EN ISO 286-2 [4], containing the information necessary for the proper use and application of qualities and intervals of dimensional tolerances in elevations of pieces. While these standards are based on what has been doing classically in the industry, in this article we will present more relevant modifications and a new format in which the most important information is collected and greatly facilitates the use of standards.

The ISA was founded in 1945 as 'the instrument society of america' (the society of instrumentalists) and ISA is currently 'the instrumentation, systems and automation Society' (the society for the systems instrumentation and Automation); which gives a global character.

From the beginning it has been a society created to promote the implementation of the instrumentation, computer systems and systems of measurement and Control for manufacturing processes and continuous processes. The society is an educational organization of non-profit status, which provides benefits to approximately 40,000 members around the world. He is recognized worldwide as the leading professional organization of specialists of the instrumentation. It consists of engineers, scientists, technicians, educators, suppliers, managers and students, those who design, use or sell the instrumentation and Control systems.

The society carries out a wide range of activities, offering its members the opportunity to frequent interaction with other specialists of the instrumentation in their communities. Through participation in the different ISA divisions, members share ideas and experiences with colleagues around the world. These divisions are thematically classified as Sciences and industries representing the different areas of work, within the instrumentation and industrial control technology (see divisions of ISA).

Picking up the experience of the industry, ISA published tables showing intervals of tolerances used in the industry, as reflected in the ' Manual than machines. Calculation of workshop ' of a. l. boxes [1], and which served as reference for many years.

Such a system, is contemplated 16 intervals of quality for a nominal size between 1 and 500 mm, and with a few values that comply with the possibilities in the manufacturing and control at the time.

Combining this information with the position of each range of tolerance, at the Universidad Pontificia de Comillas, came to work with a more practical format and is which is attached (Figure 3).

For more than 10 years, this table has served as a study material to the students of Industrial Engineering, being a significant and effective support. Experience accumulated by the teachers of the Dimensional Metrology area mainly, it was decided to update the documentation to the new ISO rules, while maintaining the previous format, which had been amply proved their worth teaching.

The University, through the authors of this article, participates and represents Spain in the Standardization Committee ISO/TC 213 'geometrical product specification and verification' develops the normalization concerning dimensional tolerances, geometric and microgeométricas among others.

All of them are based on the GPS, Geometrical Product Specification, concept whose philosophy is based on the following pillars, as reflected in [2]:

• Cover various types of standards; some of them are concerned with basic rules for specifications (core GPS standards), others of principles and global definitions (global GPS standards), and others directly concerned the geometric characteristics (standards GPS General and complementary) (see figura4).
• Cover various types of geometrical characteristics, such as dimension or size, distance, angle, shape, situation, orientation, roughness, etc. (see the chains of GPS guidelines, numbered 1 to 17 in Figure 4).
• Study the characteristics of the parts (systems of tolerances) as a result of different manufacturing process, and of the characteristics of products (components) specific (see chains of complementary GPS standards numbered from A1 to A7 and from B1 to B3 in Figure 4).
• Intervene at various stages of product development: design, manufacturing, metrology, assurance of quality, etc.
• The four different types of GPS standards form called matrix GPS.

This matrix allows a fast classification of the rule and an access to the very interesting information.

In this line, have entered new concepts like the one of operator (distinct to the of operario), operation, model of leather, etc., that although, many already came handling in the Industry, the rule had not done echo of these tendencies up to now, of here the interest to follow very closely this new Normalisation.

The new classified norms and edited under this philosophy are complete documents, autosuficientes and homogéneos, that although optimizables, constitute a very adapted approximation to a problematic that until the moment had tackled very shyly.

The norms JOINS IN ISO 286-1/2 ‘geometrical Specification of products (GPS) – System ISO for the dimensional tolerances' [3] and [4], published during the 2010, are developed under this philosophy, in addition to including new intervals of tolerance and contemplate upper dimensions to the 500 mm. In the matrix GPS of the figure 4, these norms affect to the link 1 of the chains of general norms on dimension or size, distance and radio.

To extend the range of dimensions which apply it refers dimensions from 0 to 3,150 mm, and grades from 00 up to 18. This is response to new methods and a much broader dimensions margin.

Also changed the values of the ranges of tolerance that previously had been using, since existing methods are more accurate and versatile.

After years of experience, has been completed in the area of Metrology Dimensional of the University, that the format of Figure 3 is not only pedagogically useful, but that has proven to be part of the material from pockets of engineers in their daily work. Therefore it was decided to adapt new information published in a format similar. Obviously this new table is not intended to replace regulations, but that is a tool that facilitates working with standards. It is not the same handle two rules with a total of 50 + 57 pages, that a table summary in A3 format. The developed table is shown below.

While the management of the table is almost immediately to all those who are accustomed to the use of dimensional tolerances, has taken the liberty of including an example that shows how to use the table and is compared with the result obtained if they continue with the ISA system.

Describes how to use through the calculation of tolerance associated with the bound 15 D9 of a hole.

1. ISO table. Calculation of tolerance 15 D9

From here on a reduced image of Figure 6 will be used to simplify.

Steps to perform:

Search of the tolerance interval associated with the 9 quality to a dimension of 15 mm, in the area of the table shown in Figure 7.

For an IT9 and a dimension between 14 and up including 18 millimetres, it is an IT of 43 micrometers.

2 Determine the position of the zone of tolerance (d)

The table shows only the graph for positions in axles for simplify, given that is symmetric with respect to the horizontal axis. In the standard, clearly reflected the two cases, but it should not be forgotten that this is a format that seeks the simplicity and ease of management.

Thus resorted to the chart table, Figure 9 and using that information or its symmetric (Figure 10), would be obtained that the position is that recuadra in the last figure.

Of this figure, we conclude that in the above table will be provided the Di or Ei of the bound that are interested in.

3. Search the Di at the top of the table (see Figure 11 and 12).

Resulting Di = 50 μm.

4 Express the value of the bound with your tolerance.

From now on will be used a reduced image of Figure 3 to simplify.

Steps to perform:

1. Search for the tolerance interval associated with the 9 quality to a dimension of 15 mm, in the area of the table shown in Figure 14.

For an IT9 and a dimension between 14 and up including 18 millimetres, it is an IT of 43 micrometers.

2 Determine the position of the zone of tolerance D.

Thus resorted to the chart table, Figure 16 and using such information, would be obtained that the position is that recuadra in the last figure.

From this figure, can be concluded that the table will be provided the Di or Ei of the bound that are interested in.

3. Search the Di at the top of the table (see Figure 17 and 18).

4 Express the value of the bound with your tolerance.

The use of the ISA or ISO system, is perfectly valid if properly specified is used, so that it does not give rise to confusion, and in some cases the result is the same as the previous example shows.

We recommend the use of standardized because tolerance intervals, it will take a:

• a reduction in costs, up to now caused by the manufacture of inadequate pieces, as a result of an incomplete specification;
• the optimal economic balance between the specification, fabrication and verification;
• a competitive advantage in the international market.

If you also use the format of the table above A2 or A3 you will get:

• a more rapid and effective rules management.
• access to relevant information.
• a facility in the programming of the obtaining of the tolerances.

References

1. Manual than machines. Calculation of a. l. squares workshop
2. ISO/TR 14638: 1995, Geometrical Product Specifications (GPS) - Masterplan
3. UNE EN ISO 286-1: 2010 geometric product specification (GPS) - ISO system for the dimensional tolerances - part 1: Base of tolerances, deviations and fits
4. UNE EN ISO 286-2: 2010 geometric product specification (GPS) - ISO system for the dimensional tolerances - part 2: tables of standard tolerance classes and deviations for holes and shafts limit.