Substantial modification: when a modification makes you the machine manufacturer

Why the topic matters now

Machines are modified in almost every production plant. A new controller, an additional robot, a faster cycle. Until now it was often unclear at what point such a modification has legal consequences. The Machinery Directive 2006/42/EC contained no definition; practice relied on guidance documents and interpretations.

That is changing. From 20 January 2027, the Machinery Regulation (EU) 2023/1230 applies directly in all EU member states, including Austria. It defines the term substantial modification itself. And it states clearly what follows: whoever substantially modifies a machine is considered the manufacturer of that machine.

The definition in plain words

Article 3(16) of the regulation describes the substantial modification. Broken down, all of these points must apply:

• The modification is physical or digital. A software update counts too.
• It takes place after the machine has been placed on the market or put into service, in other words on a machine that is already in use.
• The manufacturer neither foresaw nor planned it. What the instructions describe as a conversion is not covered.
• It affects safety: a new hazard arises or an existing risk increases.
• As a result, new protective measures are required. Either guards or protective devices whose integration requires a change to the existing safety control system. Or additional measures for the stability or mechanical strength of the machine.

The last point is decisive. Not every new hazard makes a modification substantial. The threshold is only reached when the answer is a new protective device that requires a change to the safety control system. The same applies to reinforcing the construction. A new hazard that can be controlled with the existing protective measures is not enough.

Four questions for your modification

These four questions let you classify a planned modification in advance:

1. Did the manufacturer foresee the change? If it is described in the instructions, for example as a format change or approved accessory, it is not a substantial modification.
2. Does a new hazard arise or does a risk increase? Think of higher speed, more force, new movements, new access points or changed software for safety functions.
3. Are the existing protective measures sufficient? If the existing guard door or light curtain covers the new situation, nothing new is needed.
4. Are new protective devices that require a change to the safety control system, or measures for stability and strength, needed? Only if the answer to this question is yes is the modification a substantial modification.

Involve everyone who knows the machine: maintenance, operators and, if possible, the original manufacturer. Record the answers in writing. The assessment is part of a risk assessment to EN ISO 12100 and later shows in a traceable way why you decided as you did.

Typical cases for orientation

The following examples show how the test questions work. They do not replace an assessment of the individual case:

Controller replacement with the same functions

An old S7-300 is replaced by an S7-1500, sequences and safety functions stay the same. No new hazard arises, so as a rule this is not a substantial modification.

Increase in performance

After the modification a conveyor runs considerably faster. The risk at the in-running nips increases and the overrun becomes longer. If this calls for an additional, monitored guard door connected to the safety controller, the threshold is reached.

Integrating a robot or cobot into an existing line

New movements and new hazards arise. Usually new protective devices such as laser scanners connected to the safety controller are needed. This is a typical case of a substantial modification.

Software update to safety functions

The regulation explicitly mentions digital modifications. If an update changes the behaviour of a safety function, it needs to be scrutinised.

What applies if it is a substantial modification

Article 18 of the regulation is clear. Whoever carries out the substantial modification is considered the manufacturer and has the obligations under Article 10. If the machine is part of an assembly of machines and the modification only affects it, the obligations apply to that machine.

In concrete terms this means:

• carrying out a risk assessment for the modified machine
• meeting the safety requirements of Annex III of the regulation, for example with validated safety functions to EN ISO 13849-1
• compiling the technical documentation and carrying out the conformity assessment under Article 25
• issuing the EU declaration of conformity, affixing the CE marking and updating the instructions

This applies to operators just as much as to machine builders. A production company that modifies its own line also becomes the manufacturer.

And if it is not a substantial modification?

Then the machine legally remains what it was. The original declaration of conformity remains valid. For operation in Austria, however, the Employee Protection Act (ASchG) and the Work Equipment Ordinance (AM-VO) continue to apply, including to the modified part. And the assessment itself should be documented – it is your evidence if anyone asks later.

Sources

• Regulation (EU) 2023/1230 on machinery, EUR-Lex – Art. 3(16), Art. 10, Art. 18, Art. 25, Annex III
• Corrigendum to the regulation, OJ L 169 of 4.7.2023 – date of application 20 January 2027 (Art. 54)

This article provides an overview and is not legal advice. Standards and the regulation text are paraphrased; the original text is authoritative.