Additive manufacturing – a key factor in the maintenance of Italian trolleybuses

In Naples, the public transport company Azienda Napoletana Mobilità S.p.A (ANM) has been using additive manufacturing to repair certain spare parts for its trolleybuses, in particular the carriage heads. By 3D printing these parts, the company says that it has reduced the downtime of its electric vehicles by 95%. Already in service for a number of years in the Italian city, their components are no longer manufactured, and replacing them using traditional methods would take too long.

Additive manufacturing now enables us to rethink our supply chains while favoring local, faster production. Through reverse engineering, manufacturers are able to produce obsolete parts more quickly by digitizing the original part in 3D. A 3D model is then created, enabling the physical design to be produced in just a few days. This workflow is of particular interest in the transport sector to avoid excessive vehicle downtime and the subsequent drain on resources.

The new carriage head in action (photo credits: Stratasys)

Two additive manufacturing processes to design the carriage head

ANM therefore decided to turn to additive manufacturing to design certain components for its trolleybuses, in this case the carriage heads. It called on the Italian 3D printing service 3DnA, which has an FFF 3D printer, namely the Stratasys F900 and the SLM 500 by SLM Solutions. The selected thermoplastic is the ULTEM 9085, renowned for its high resistance and electrical insulation properties, with the chosen metal being an aluminum alloy, the AlSi10Mg.

Alessandro Manzo, CEO of 3DnA, explains : “The part must not conduct electricity, so this material is essential. The ULTEM 9085 resin also meets three key criteria for end applications in the field of transport: excellent heat resistance with a distortion temperature of 153°C, it is a fire-retardant thermoplastic providing a very high weight-to-resistance ratio.”

The ULTEM 9085 3D printed envelope (photo credits: Stratasys)

Reduced trolleybus downtime

Manufacturing these parts in the traditional way would have taken 12 months according to ANM – a period that has been significantly shortened thanks to additive manufacturing. In fact, it estimates that downtime has been reduced by no less than 95%. Now the part in question is composed of a central metal structure and an external housing, both 3D printed, with the housing used to connect the carriage head to the suspended cables. This new design offers interesting possibilities for the future: if the part is damaged, only the structure or the housing will have to be 3D printed, not the whole part. 

Alessandro Manzo continues :  “Thanks to our F900, we have been able to manufacture and deliver about 20 of the carriage head’s most critical parts in just 2 weeks, enabling ANM to eliminate all additional risk of downtime for its fleet and to guarantee reliable transport to 3 million Neapolitans. All in all, having this level of flexible production is extremely important for ANM, as it can now order parts in line with its actual needs instead of maintaining large stocks of costly parts.”

Fabrication additive
The metal structures printed on an SLM Solutions machine

The Italian 3D printing service is aiming to use 3D technologies for other applications in the transport sector in order to demonstrate the full scope of their potential.