Additive Manufacture of Class 165 armrests

(Derby, May 2020) DB ESG are working in collaboration with Angel Trains on projects that incorporate 3D printing solutions (also known as additive manufacturing or AM) to address UK rail industry challenges.

Individual Project Background

The armrests used on Chiltern Railways’ Class 165 units consists of large steel rods over-moulded with polymer trim. The original part had a minimum order quantity of 10 and a lead time of four months. This component was reverse engineered to demonstrate the cost and lead time improvements that could be realised by using AM to produce them.

Work Undertaken

• The current armrest was 3D scanned at the depot.
• The scan was converted into a 3D model, a process which allows components to be modelled accurately and easily.
• The model was modified to allow the incorporation of a CNC steel insert at the armrest’s mounting location.
• The replacement armrest was designed for fused deposition modelling (FDM) and then 3D printed using Stratasys’ ULTEM 9085 black, a fire compliant polymer. The replacement armrest is constructed of a solid block of material, with an interior low-density cylindrical section. This section helps to reduce the weight and cost, whilst also improving the deformation of the part in structural analysis.
• A prototype design was printed and was found to be fit for purpose at first iteration.
• A batch of armrests was produced using AM, the metal inserts were then adhesively bonded into place.
• Once the armrests had been printed, they were sanded and painted to match the originals using a common rail-grade coating system.
• Four armrests have completed a successful in-service trial on Chiltern Railways. These parts will now remain in service on the units.

Whilst the 3D printed part’s unit cost was more expensive, there was a significant improvement in the minimum project costs compared to the conventionally made component, which necessitated a minimum order volume of 10. This digital workflow also reduced lead times. It traditionally would have taken four months to produce these armrests, the new method enabled production and finish in less than three weeks.