Stellantis turns existing sites into the construction site of the future

"New is always better." Fans of the American cult sitcom "How I Met Your Mother" will probably know immediately where this statement comes from. But the motto of the extroverted womaniser Barney Stinson is not always appropriately applicable, at least to the automotive industry. Of course, new plants attract attention. BMW's latest iFactory in Debrecen, Hungary, for example, was built specifically for the Neue Klasse and is regarded as a lighthouse project for the next generation of automotive production. The greater industrial feat, however, is taking place in many places within existing facilities. For years, manufacturers have been trying to convert, renovate and upgrade existing factories so that they are also suitable for future platforms, electrified drivetrains and more flexible production concepts.

BMW, too, has taken this path at its main plant in Munich, where an old, cramped plant located right in the middle of the city was prepared for the production of the latest vehicles. Stellantis is also pursuing a similar philosophy. In its global production network, the group is increasingly focusing on further developing existing plants instead of building new capacities on greenfield sites.

This approach is becoming increasingly important, especially in Europe. The industry is under pressure from structural overcapacity, fluctuating demand and high investment requirements. Stellantis therefore wants to make better use of the existing industrial footprint and adapt plants so that they can respond more flexibly to new products and technologies. Existing buildings, facilities, logistics structures, supplier networks and workforces are thus becoming strategic resources.

One example is the French site in Poissy. The plant is being geared towards new industrial activities, including vehicle conversions, circular economy and parts production. The aim is to continue using the existing industrial substance, improve utilisation and secure employment at the site over the long term.

Flexibility is becoming a core industrial task

Behind such projects lies a changed logic in the production strategy. Today, plants must not only produce efficiently, but also become significantly more adaptable. Electrification is a central driver here, but not the only one. Added to this are increasing model diversity, new platforms, cost pressure and demand that is more difficult to plan regionally and technologically.

For Stellantis, this means that plants must master multiple powertrain types and vehicle configurations. Assembly lines are therefore being converted so that vehicles with internal combustion engines, hybrid drives and battery-electric drives can be produced on the same lines. Range-extender models also play a role in planning. In a market in which demand for individual drive concepts is developing differently, this multi-energy capability is becoming an important industrial buffer.

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At the same time, the pressure is increasing to industrialise new models more quickly. Plants must accelerate ramp-ups, absorb fluctuations in demand and make supply chains more robust. This shifts the focus. What is decisive is no longer only whether a plant can technically be converted for a new product, but how quickly and with as little production interruption as possible this conversion succeeds.

New platforms reach deep into the plants

Another trigger for the conversions is new vehicle architectures. They are intended to reduce complexity, increase modularity and enable greater standardisation. What promises simplification at the product level initially means considerable adjustment requirements for production. New platforms change body structures, assembly processes, test procedures, logistics flows and in some cases also requirements for battery or high-voltage technology.

An example of this is the Stellantis plant in Zaragoza, Spain. Between 2026 and 2028, the multi-brand group is preparing one of the largest product renewal programmes in the history of the site there. Several new vehicles are to be integrated into ongoing operations. At the same time, the manufacturing system is being aligned with future technologies and architectures.

At the centre is the introduction of STLA One, a new global modular architecture from Stellantis. It is intended to support various vehicle segments and drive technologies. For Zaragoza, this means considerable adaptations to existing facilities, processes and manufacturing systems. Whenever possible, Stellantis relies on further developing existing plants instead of building up new capacities. Mulhouse in France also follows this pattern.

The plant is being prepared for the production of three electric and hybrid Peugeot models of the next generation based on the STLA-One platform. Such projects show how strongly the platform strategy is now linked with the further development of existing production sites.

Not every existing site is suitable for every conversion

Despite the focus on existing plants, Brownfield first is not automatic. Whether a site is modernised, expanded or replaced depends on several factors. Stellantis refers here to industrial, financial and strategic criteria. As part of the “FaSTLAne-2030 strategy”, the optimisation of the production network is intended to help improve competitiveness, capacity utilisation and capital discipline. Decisive factors include the product strategy, expected market demand, the cost position of the site and the productivity potential. 

Added to this are the condition of existing facilities, their technical upgradability, the logistics efficiency, the local supplier environment and the capabilities of the workforce. Only from this interplay does it emerge whether a modernisation is economically and industrially sensible.

This also makes it clear that, although existing plants offer many advantages, they also set clear limits to planning. A brownfield project can limit investment and use existing structures. However, it must cope with existing buildings, layouts, equipment and ongoing processes. That is precisely where the complexity lies.

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Paint shop and body shop remain particularly demanding

Particularly challenging are areas in which new technologies intervene deeply in existing processes. These include paint shops in particular. They are energy-intensive, are subject to high environmental requirements and have a direct influence on product quality. Changes therefore affect not only individual installations, but often also energy supply, emissions, drying technologies, layouts and quality assurance.

Stellantis is modernising paint shops in the global network and is relying in part on the Four-Wet Compact Painting Process, electrified ovens and advanced automation. The group cites Sochaux as an example. There, the paint shop was comprehensively modernised and equipped with electrified processes, AI-based quality control and optimised layouts.

Body shop is also among the demanding areas. There, the degree of automation is high, robotics is deeply integrated into the processes. New vehicle architectures must therefore be integrated into existing systems and control systems. This can require new joining processes, different geometries or changed process sequences, while cycle times and quality requirements must remain stable.

In final assembly, the challenge lies less in individual systems than in the growing variety of variants. When combustion-engine vehicles, hybrids and electric vehicles are produced on shared lines, logistics, ergonomics, testing processes and qualification of employees must keep pace. Also battery-related activities and high-voltage testing change the requirements for the line.

Conversions must fit into ongoing operations

The greatest practical difficulty of many brownfield projects lies in introducing new products, systems or processes without disrupting ongoing production more than necessary. Stellantis therefore plans such changes over the long term and implements them in phases. Larger interventions are scheduled, where possible, during planned downtimes, such as the summer shutdown.

This requires close coordination between production, engineering, logistics, maintenance, supply chain and suppliers. Installation, commissioning and ramp-up must be scheduled in such a way that delivery commitments can be met and quality risks can be limited. In individual cases, inventories can be built up before critical conversion phases in order to safeguard customer supply during the work.

The reuse of existing equipment and infrastructure certainly limits capital requirements. But at the same time it also increases planning complexity. New systems must fit into existing structures, and the transitions between old and new production must be controlled. Brownfield is therefore less a one-off conversion than a precisely sequenced intervention in an ongoing industrial system.

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Digital tools should make risks visible earlier

Simulation, digital twins and virtual validation are gaining in importance in such projects. They make it possible to check layouts, material flows, automation concepts and process changes before implementation. Particularly in the case of conversions in existing facilities, digital models can help to identify bottlenecks early and play through various scenarios.

According to the company, Stellantis is increasingly integrating digital twins, simulation and predictive analytics into production planning and industrialisation. The aim is to reduce risks, improve decisions and solve problems virtually before equipment is installed on the shop floor. The group also intends to use this to link collaboration between engineering teams and plants earlier and more closely.

This approach was recently reinforced by an initiative to expand AI-supported digital twins in the production network. It is intended to accelerate industrialisation, improve operational performance and enable more data-based decisions.

Transformation also remains a question of people

As much as technical aspects are also in focus during transformation - its success does not depend solely on equipment, robots or software. New processes, new equipment and new safety requirements must be understood and mastered by employees. Stellantis therefore involves production employees, maintenance, occupational safety, engineering and plant management in the projects at an early stage.

The group refers to this as a workplace integration approach. According to this, engineering functions and plant teams are already working together in early project phases so that practical experience from the plant can feed into process design and industrialisation decisions. Particularly in the case of conversions in existing facilities, this feedback can be decisive because not every practical constraint is visible in central planning models.

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Training, workshops and pilot activities are intended to prepare employees for new equipment and processes before the full rollout. Maintenance teams are involved at an early stage in order to build up technical knowledge and secure long-term equipment availability. Where similar technologies are already running at other sites, experienced teams can help with the transfer of knowledge.

At the same time, digitisation and automation are changing the competence profiles. Data literacy, digital tools and knowledge of modern manufacturing technologies are becoming more important. This means that the plant transformation is not only an investment programme, but also a qualification process.

Conflicting objectives are pre-programmed

The Stellantis examples alone show how strongly the industrial transformation in the automotive industry is shifting into the existing estate. For Stellantis, brownfield is not only a reaction to cost and capacity pressure. The approach is intended to use the existing industrial substance and at the same time prepare plants for new products, platforms and powertrains. But the conflicting objectives emerging from this cannot be dismissed.

Existing plants do indeed offer experienced workforces, existing logistics structures, established supplier relationships and lower capital requirements. At the same time, they limit planning freedom and make conversions during ongoing operations challenging.