The Retrofit That Changed Everything
Your factory has 15-year-old packaging machines. They work fine, but they're not connected to your factory management system, and their controls are purely mechanical. To integrate them with your production line and add digital monitoring, you hire a specialist to retrofit the control systems, replace the mechanical interlocks with software-driven safety functions, and connect them to your network.
The retrofit works perfectly. Your line is now fully automated and networked. Three weeks later, the compliance officer asks: have we assessed this retrofit under Machinery Regulation 2023/1230?
This question matters because the retrofit you just performed has legal consequences. Depending on what changed and how, you may now be legally classified as the manufacturer of that machine — not the operator. And manufacturers, not operators, bear the compliance responsibilities under the new Regulation. That distinction applies from 20 January 2027.
What "Substantial Modification" Means
Regulation 2023/1230 introduces a defined concept: substantial modification. It appears in Article 3(16) and carries legal weight.
Substantial modification is defined in Article 3(16) as a physical or digital alteration to machinery that:
- Has already been placed on the market or put into service, AND
- Was not originally provided for or envisaged by the original manufacturer, AND
- Affects the safety of that machinery by creating a new hazard or increasing an existing risk, which requires either:
- (a) the addition of guards or protective devices whose modification necessitates altering the existing safety control system, OR
- (b) the adoption of additional protective measures to ensure stability or mechanical strength
The key word is not envisaged by the original manufacturer. If the manufacturer published a retrofit kit, upgrade path, or integration module in their technical documentation, then performing that upgrade is not a substantial modification — it was contemplated and designed for. But if you make a significant change that the original design did not accommodate, and that change affects safety, you have crossed the threshold.
Let's illustrate with examples:
- Replacing a mechanical brake with a software-controlled brake system — substantial. The original machine was designed with mechanical fail-safes; the new system replaces them entirely, introducing new control logic and digital dependencies that the original design did not account for.
- Adding network connectivity where none existed — substantial, if the connection alters safety functions or allows remote control of hazardous operations. The original machine was isolated; the network exposes new attack surfaces and control paths.
- Changing the material of a guard from steel to plastic — probably not substantial, unless the plastic guard materially reduces impact protection below what the risk assessment requires.
- Integrating a new sensor for monitoring (without changing safety interlocks) — probably not substantial, if it only adds data collection and does not alter the machine's ability to stop or protect the operator.
The critical factor is whether the modification introduces a new hazard or increases existing risks, and whether it requires the measures specified in Article 3(16)(a) or (b).
When You Become the Manufacturer
This is the legal consequence: if your modification is substantial, you are classified as the manufacturer for the purposes of Regulation 2023/1230.
This classification is established in Article 18, first paragraph, which states that a person who carries out a substantial modification to machinery is considered a manufacturer for that machinery or related product (or, if the modification affects only part of an assembly, for that affected machinery or related product as demonstrated in the risk assessment).
According to Article 18, second paragraph, you must then apply the relevant conformity assessment procedure specified in Article 25(2), (3), or (4), depending on the risk category and Annex I classification.
Article 10 of the Regulation sets out the core obligations that fall on a manufacturer:
- Conduct a risk assessment (EN ISO 12100)
- Prepare or update technical documentation (Annex IV Part A — 14 structured points)
- Apply relevant harmonised standards or common specifications
- Perform conformity assessment using the appropriate module (Module A, B+C, G, or H — depending on risk category and Annex I classification)
- Issue a Declaration of Conformity (Annex V Part A — 10 mandatory points)
- Affix CE marking to the modified machinery (Article 24)
- Retain all documentation for 10 years (Art. 10(3))
- Ensure availability of instructions for use (Art. 10(7))
- Ensure availability of the Declaration of Conformity (Art. 10(8))
- Monitor market feedback and manage any post-market issues
These obligations apply to the entity that performed the substantial modification, not to the original manufacturer. Your responsibility for the modified machine begins; however, the original manufacturer remains responsible for the compliance of the unmodified design. The scope of your responsibility is limited to the machinery or related product affected by the substantial modification, as demonstrated in your risk assessment.
This does not mean the original manufacturer is off the hook for their design. But the integration, retrofit, or upgrade — that becomes your responsibility to certify and document.
The Grandfathering Exception — and Why Substantial Modification Breaks It
Regulation 2023/1230 applies from 20 January 2027. But it includes a grandfathering provision (Article 52(1)): machinery that was lawfully placed on the market in compliance with the old Machinery Directive 2006/42/EC before 20 January 2027 may continue to be made available on the market even after that date, without needing to comply with the new Regulation.
The old Directive is repealed effective 20 January 2027 (Article 51(2)). However, EC type-examination certificates and approval decisions issued under Article 12 of Directive 2006/42/EC remain valid until they expire (Article 52(2)), which matters if your machine's certification is still running.
This grandfathering is important. Owners of machinery already in use do not need to retrofit or recertify. A 10-year-old lathe that is CE marked under the Directive can stay in production after January 2027.
However, a substantial modification breaks this protection.
If you perform a substantial modification on a machine that was grandfathered under the old Directive, that modification itself becomes subject to the new Regulation. The machinery, as modified, must now be assessed, documented, and certified under Regulation 2023/1230. You cannot simply rely on the old Directive's CE marking for the unmodified machine; the modification creates a new legal baseline.
In practical terms: you own a machine with old-Directive CE marking. It is legally "grandfathered" and does not need updating. But the moment you substantially modify it, you have created a new version of that machine — and the new version must comply with the 2023/1230 Regulation. The original CE mark is no longer sufficient for the modified state.
This is why retrofits, integrations, and upgrades are dangerous under the new Regulation. They can inadvertently trigger compliance obligations that did not exist before.
The Non-Professional User Exception
There is one exception defined in Article 18, third paragraph: a non-professional user (a natural person) who substantially modifies a machine for their own use (not commercial use) is not classified as a manufacturer and is not subject to the obligations in Article 10.
This exception is narrow. It applies to:
- An individual who owns a machine and modifies it for personal hobby or domestic use, OR
- A farmer who modifies farm equipment they own for their own agricultural operations (not for resale or hire)
It does not apply to:
- A company that performs retrofits or integrations (even if small)
- Any entity acting in a professional or commercial capacity
- An operator modifying machinery for use in a commercial production line
If you are a business entity (sole proprietor or larger), the exception does not protect you. You are subject to the full manufacturing obligations.
Common Modifications That Qualify as Substantial
To help you assess your own situation, here are modifications that typically cross the substantial threshold:
Physical Modifications
- Changing the structural design (e.g., extending the frame, altering the mounting points, changing the load path) — especially if this affects safety distances or structural integrity
- Replacing core mechanical systems (e.g., swapping a hydraulic system for electric, replacing a belt drive with a direct drive) — if the new system introduces new failure modes or control dependencies
- Removing or replacing guards — if the new configuration reduces protection or introduces new access points to hazards
- Altering speed, force, or operational envelope — increasing cycle speed, load capacity, or pressure beyond the original design parameters
Digital Modifications
- Adding software-driven control where there was manual or simple mechanical control
- Introducing network connectivity to a previously isolated machine, especially if it enables remote operation or changes safety interlocks
- Adding or modifying sensors that directly affect safety-critical functions (e.g., new emergency stop logic, force-limiting algorithms)
- Changing the architecture of the safety controller (e.g., replacing a hardwired safety relay with a programmable logic controller) — if this changes how safety is enforced
Integration Modifications
- Integrating the machine into a larger automated line where it now receives inputs or commands from upstream/downstream equipment — if this introduces new hazards (e.g., pinch points between machines, dependency on external control signals)
- Connecting to a factory network or MES such that production commands or monitoring data flow through external systems, introducing cybersecurity or control dependencies
What to Do Before You Modify
If you are considering a retrofit, upgrade, or integration:
Define the scope of the modification in writing. What is changing? What is not changing? What will the machine do differently after the modification?
Compare against the original technical file. Did the original manufacturer document or provide for this modification? If yes, follow their documented procedure. If no, it may be substantial.
Conduct a preliminary hazard review. Will this modification introduce a new hazard? Will it increase an existing hazard (e.g., new control paths, new failure modes, new dependencies)? If yes, it is likely substantial.
Engage a compliance advisor or notified body early. Do not wait until after the modification is done. Get a preliminary opinion on whether the modification is substantial and, if so, what the compliance pathway is.
Document the decision. If you conclude the modification is not substantial, document your reasoning. If you conclude it is substantial, plan for the compliance work now.
Verify the application date. The Regulation applies from 20 January 2027. Modifications performed before that date are subject to the old Directive. Modifications performed on or after that date are subject to the new Regulation. If your modification straddles the transition (some work before, completion after), the compliance date is the date the modification is complete.
FAQ
Q: We maintain and repair our machines in-house. Is routine maintenance a substantial modification?
No. Routine maintenance, repair, and replacement of worn-out parts using original manufacturer spare parts is not a substantial modification. Wear and tear is contemplated by the original design, and repair restores the machine to its original state.
However, if you upgrade a component (e.g., replacing a standard motor with a higher-power motor, or a mechanical brake with a software-controlled one), that may cross into modification territory.
Q: The original manufacturer went out of business. Can we still modify the machine?
Yes, but with care. The manufacturer's dissolution does not exempt you from the Regulation. If you substantially modify a machine, you take on the manufacturer role, regardless of the status of the original maker. The fact that the original documentation is unavailable does not reduce your compliance obligation — it may make it harder to comply, but it does not eliminate the requirement.
You should reconstruct the original design (as much as possible) from the physical machine, available documents, industry standards, and expert inspection. That reconstruction becomes your baseline for assessing what the modification changes.
Q: We buy second-hand machines from other EU countries and install them in our factory. Is installation a substantial modification?
Not if you install them as-is. Simply placing a used machine into operation is not a modification. The original CE mark applies, and grandfathering rules protect you (provided the machine was lawfully placed on the market before 20 January 2027).
However, if you alter, upgrade, or integrate the machine into your production line (e.g., adding sensors, changing controls, connecting to your network), that alteration may be substantial.
Q: What if we only add sensors or monitoring, without changing how the machine operates?
It depends. If the sensors feed only into data collection systems and do not affect safety interlocks or control logic, it is probably not substantial. But if the sensors alter when the machine stops, how it responds to overload, or what an operator can do, then it is likely substantial.
The test is: does this change introduce a new hazard or increase an existing one at the level of risk management? Passive monitoring usually does not. Active control changes usually do.
Q: When exactly must we comply — before or after 20 January 2027?
The date of the modification matters:
- Modifications completed before 20 January 2027 — subject to Machinery Directive 2006/42/EC (the old rules)
- Modifications completed on or after 20 January 2027 — subject to Regulation 2023/1230 (the new rules)
If your modification spans the transition date (work starts before, finishes after), the compliance standard is the one in effect when the modification is complete.
Your Modification Checklist
Before committing to a retrofit, upgrade, or integration:
- Scope: Have you defined in writing what is changing and what is not?
- Original design: Have you reviewed the manufacturer's technical file or original documentation?
- New hazards: Will this modification introduce a new hazard (e.g., network attack surface, new control dependency, new structural load)?
- Risk increase: Does this modification increase an existing hazard significantly enough to require new protective measures?
- Advice: Have you consulted a compliance advisor or notified body for a preliminary assessment?
- Substantial decision: Have you made and documented a decision on whether the modification is substantial?
- Compliance plan: If substantial, have you planned the risk assessment, technical documentation, and Declaration of Conformity?
- Timing: If modifying near 20 January 2027, have you confirmed which regulatory standard applies (old Directive or new Regulation)?
What Comes Next
If you determine that your modification is substantial, the next steps mirror those required for a new machinery manufacturer:
- Conduct a comprehensive risk assessment (use EN ISO 12100 as your foundation)
- Design control measures to address identified hazards
- Document your technical file according to Annex IV Part A (14 points: design rationale, hazard analysis, protective measures, test results, cybersecurity assessment, etc.)
- Apply harmonised standards where relevant (and document which ones you applied and which alternatives you used)
- Perform conformity assessment (Module A, B+C, G, or H depending on risk)
- Issue a Declaration of Conformity following Annex V Part A (10 mandatory points)
- Affix CE marking to the modified machinery
- Prepare instructions for use (in the language of the end-user's country)
This checklist is for the operator or retrofit company performing the modification. The original manufacturer's compliance file does not transfer to you; you start fresh with the modified design as your baseline.
Takeaway
Modifying an existing machine is often the right business decision — it extends asset life, improves productivity, and avoids the cost of replacement. But under Regulation 2023/1230, it carries legal responsibility. A substantial modification makes you the manufacturer of that modified machine, with all the compliance obligations that status entails.
Start your assessment before you design the retrofit. Talk to a compliance advisor. Document your reasoning. And if the modification is substantial, budget for the compliance work — risk assessment, documentation, certification. It is not optional; it is part of the cost of the project.
The Regulation applies from 20 January 2027. If you are planning modifications, now is the time to clarify the legal landscape.