Assembly of Machinery

Last edit: 01/08/2023

THE DOUBT: Shall a group of machinery be CE Marked? When can I say a certain group of machinery constitute an Assembly of Machinery and therefore, it must be CE marked?

CONSIDERATIONS: Let’s start with their definition:

[2006/42/EC] Article 2 – Definitions

  1. ‘machinery’ means:


Assemblies of machinery referred to in the first, second and third indents or partly completed machinery referred to in point (g) which, in order to achieve the same end, are arranged and controlled so that they function as an integral whole.

An assembly of machinery consists of two or more machines or partly completed machines assembled together for a specific application. Assemblies of machinery may be constituted by two units such as, for example, a packaging machine and a labelling machine, or by several units assembled together, for example, in a production line. The definition of assemblies of machinery indicates that assemblies are arranged and controlled so that they function as an integral whole in order to achieve the same end.

Let’s see the conditions to have in order to define a group of machinery a single entity.

[Guide to the Machinery Directive: 2019] §38 Assemblies of machinery


For a group of units of machinery or partly completed machinery to be considered as an assembly of machinery, all of these criteria must be fulfilled:

  • the constituent units are assembled together in order to carry out a common  function, for example, the production of a given product;
  •  the constituent units are functionally linked in such a way that the operation of each unit directly affects the operation of other units or of the assembly as a whole, so that a risk assessment is necessary for the whole assembly;
  • the constituent units have a common control system – see §184: comments on section 1.2.1, and §203: comments on section of Annex I.


A group of machines that are connected to each other but where each machine functions independently of the others is not considered as an assembly of machinery in the above sense. In a factory a series of 10 Lathe machines is not an assembly of Machinery. Therefore, the definition of assemblies of machinery does not extend to a complete industrial plant consisting of a number of production lines each made up of a number of machines, assemblies of machinery and other equipment, even if they are controlled together by a single production control system.

Only if the plant (which may be any combination of machinery, partly completed machinery and other equipment resulting in machinery subject to the Machinery Directive) forms a single integrated line is it subject to the Machinery Directive as an assembly. Such an assembly must be CE Marked as a whole, even if each single machine is already CE Marked. The question is if each single machine of the assembly has to bear the CE Mark. It depends if each machine can operate independently. Here what the Guide states:

[Guide to the Machinery Directive: 2019] §38 Assemblies of machinery


If the units concerned are placed on the market as complete machinery that could also operate independently, they must bear the CE marking and be accompanied by an EC

Declaration of Conformity. If they are placed on the market as partly completed machinery, they must not bear the CE-marking, but note that if other legislation providing for CE marking also apply (e.g. ATEX Directive, Radio Equipment Directive, etc.), a CE marking will have been applied, in which case the Declaration of Conformity should state it only covers that legislation. In all cases the partly completed machine must be accompanied by a Declaration of Incorporation under the Machinery Directive together with assembly instructions.

Therefore, for the purpose of applying the Machinery Directive, most industrial plants can be divided into different sections, each of which may be a distinct assembly (of machinery) or even an independent machine (e.g. a mixing  vessel). Even a single production line may be divided into separate assemblies and/or machines if there is no safety related connection between constituent assemblies or machinery.

Assemblies of machinery are subject to the Machinery Directive because their safety depends not just on the safe design and construction of their constituent units but also on the suitability of the units linked together and the safety of the interfaces between them. At the interface, modifications of or additional, guarding/protection devices may need to be designed and fitted so that the assembly as a whole is compliant. The risk assessment to be carried out by the manufacturer of an assembly of machinery must therefore cover both the suitability of the constituent units for the safety of the assembly as a whole and the hazards resulting from the interfaces between the constituent units.

It must also cover any hazards resulting from the assembly that are not covered by the EC Declaration of Conformity (for machinery) or the Declaration of Incorporation and the assembly instructions (for partly completed machinery) supplied by the manufacturers of the constituent units.


CONCLUSIONS: Every time a group of Machinery work together to produce a specific product or by product, we may be in a situation of having an Assembly of Machinery. In this case it is not enough that each machinery is CE market, the whole assembly need to be CE marked.

But how to be sure? If they are under the control and/or safety of one system, that is an Assembly of Machinery. However, if they are controlled by different control and safety systems, in principle the assembly cannot be considered an Assembly and therefore it cannot be CE marked as a whole, even in case there are risks in the interface between machinery.

In our opinion, that is a too strict interpretation. Even if the machines have each one its own control system, if there are signals interchanged between the machines that are needed to guarantee the production of a specific product, that can be considered as an Assembly of Machinery and therefore be CE marked. During that process, a risk assessment has to be performed, focusing on the interfaces between machinery.

Please bear in mind that there is another definition, very similar to Assembly of Machinery, that is an “Integrated machinery system”. It is defined in ISO 11161 as

[ISO 11161: 2023] 3.1 Terms and definitions

3.1.1 integrated machinery system. Two or more machines, capable of operating independently of each other, which are interconnected by controls and act together in a coordinated manner for the purpose of fabrication, production, treatment, processing or packaging of discrete parts or assemblies as part of an enterprise's supply chain
Note 1 to entry:  An integrated machinery system can be linked by a material-handling system.
Note 2 to entry: The control means of the integrated machinery system can also interconnect to other processes and/or resources.

An Assembly of Machinery is always an Integrated Machinery System, but the other way round is not always true.

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