Project Brief

Model railway retailer, Rails of Sheffield, sought to fulfil a demand for niche products in their hobby market that would not normally justify a full production run using injection moulding processes.

Rails of Sheffield are the second-largest retailer of railway modelling items in the UK. They also manufacture specialist, museum-quality, niche products for collectors under their own label. Their ethos is simple: these products must be researched, designed and produced solely in the UK.

The Challenge

Rails of Sheffield were determined to create a viable, niche product that not only satisfied its market in terms of price, but also in terms of longevity and durability. Key to the success of the product would be the ability to include a level of detail that would be impossible to reproduce through injection moulding; and the ability to minimise the number of parts included in the assembly of the product.

The Solution

Rails of Sheffield knew from the start that 3D printing (additive manufacturing) would possibly provide the solution to their needs. However, the common desktop technology used by the hobby market to print wagons and coaches could neither deliver on the detailing required nor on the economies of scale necessary to achieve in order to produce models in sufficient quantity. Furthermore, the resins available were unlikely to be robust enough for producing ready-to-run products.

Having explored a range of 3D printing and additive manufacturing options, Rails were delighted to discover that Carbon® Digital Light Synthesis™ technology was available in the UK. Moreover, it was available ‘just up the road’ from the Rails headquarters.

Rails met with Paragon Rapid Technologies in November 2018 to explore the opportunities for production Carbon’s technology has to offer.

Designing wagons for Carbon®

The first step in the process was to really test what was achievable with the technology. Carbon’s technology is designed to print multiple parts in one build, and the greater the efficiency in use of build space, the more cost-effective the build will be when it comes to producing large numbers of product.

Paragon and Rails started the venture with a design that aimed to print the part in one piece. However, Rails desired a considerable level of detail on the wagon and building it in one piece could not achieve the necessary support on the build platform without compromising aesthetics.

Further collaboration between Paragon and Rails to improve the design for manufacturability ensued. This resulted in three-piece unit comprising roof, body and chassis, all sitting within each other. It was this design that delivered optimum production efficiency.


Carbon’s rigid polyurethane, RPU 70, was chosen as the most suitable material for printing the first batch of wagons.

RPU 70 is very similar in nature and mechanical properties to the injection moulding material, ABS. Of the diverse range of Carbon materials available, RPU 70 gave Rails of Sheffield the cost-effectiveness, combined with the material properties they desired – basically, the robustness required to withstand constant handling and use – to meet their key production criteria.

The outcome

The first batch of Rails of Sheffield wagons was sold out. Such was the success of the model, it generated demand for a second production run and proved that, as a commercial enterprise, it was one worth developing. Future aspirations are that different versions of the wagon will be developed over the coming months.

The success of this first production run has resulted in a plan for an initial two-year schedule of new products. The plans are to print more wagons, carriages and engines with an ongoing cycle of design, sampling and production.