TL;DR
Since 2026, ISO GPS has been an integral part of numerous PAL examinations across the board. Trainers, examiners and trainees must therefore be able to fully understand and apply key principles such as ISO 8015, reference systems, general tolerances, dimensions and modifiers. A structured, practical approach to the reorganisation of the training programme is crucial.
Who is affected by the issue of ISO GPS in training?
ISO GPS, as an international standardisation system for the unambiguous geometric description of components, their manufacture and measurement, plays a role in many technical apprenticeships. The IHK Centre for the Development of Examination Papers and Teaching Materials (PAL) has decided to incorporate the content of these standards into intermediate and final examinations from 2026 onwards.
This knowledge is relevant to these apprenticeship programmes and others besides: Metal Technology Technician, Machining Mechanic, Production Mechanic, Industrial Mechanic, Machinery and Plant Operator, Toolmaker and Technical Product Designer. PAL published the detailed list in its implementation recommendations from spring 2026.
Trainers and teachers in these professions face the challenge of being familiar with the content of the standards and being able to convey it.
Apprentices must therefore be able to acquire and apply ISO-GPS knowledge. If the basics are taught from the outset, this, combined with the use of CAD systems, will lower the barrier to applying this knowledge.
Examiners are often also the trainers within the companies, and so have a dual role to fulfil.
What are the key changes to the training programme?
The interplay between standards is set out in a hierarchy. One of the key overarching standards that everyone needs to be familiar with is ISO 8015, which sets out 13 principles dating from 2011. These principles influence the interpretation of the markings on the drawing without the standard having to be specifically cited.
GPS tolerancing focuses on function to ensure that the component fulfils its intended purpose and that this is communicated throughout the product development process. Until now, tolerancing has been very heavily production-oriented, which can result in components that do not fulfil their intended function, even when manufactured to specification.
The basic principle is that components must be mentally broken down into individual geometric elements in order to achieve unambiguous and complete tolerancing of the entire component. As a general rule, tolerances initially apply to the individual geometric elements or to their relationship with one or more others.
Here is a component that is, as it were, broken down into individual geometric elements:
Constraints are references used to relate geometric elements to one another, such as the parallelism of a plane to a second plane. When converting to ISO GPS, it is important that a reference system is established from individual constraints, which is used to constrain the degrees of freedom of the component and to define a coordinate system for it. A defined sequence of constraints ensures a function-oriented and comparable basis.
To minimise the amount of text on the drawing, so-called ‘defaults’ apply. These are specifications that apply without being explicitly stated. The relevant GPS standards set out which defaults apply.
The new general tolerances set out in ISO 22081 are one reason for the change in testing procedures. In 2022, ISO 2768 was replaced so that general specifications could also be recorded in accordance with the latest rules.
Understanding the difference between dimensional measurements and distance measurements is key to establishing unambiguous tolerances. Until now, no distinction has been made between lengths when setting tolerances. However, plus-minus tolerances for distance measurements lead to ambiguities because they do not take shape deviations into account.
Modifiers are additional symbols that are entered to override default settings. One important modifier is the ‘E’ inside a circle, which indicates the envelope condition; this has been in use for many years, but did not have to be entered explicitly until 2011.
A new standard has also been in place for the past few years regarding the limitation of surface roughness. An expanded symbol and amended rules mean that staff will need to retrain in this area as well.
How can the transition be successful?
In our experience, applying the ISO-GPS rules correctly – and the associated changes to the previous training content – requires a structured approach.
Firstly, the trainer must familiarise themselves with the basics. Depending on the trade being taught, the focus must be on either tolerancing or interpretation. Both tolerancing and the measurement of the new dimensions on the finished part should be practised using training components.
We’d be happy to help you with that.
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