Kingsbury highlights a successful 3D printing project carried out by one of its principals, German wire arc additive manufacturing (WAAM) equipment builder Gefertec, and has produced a video of it.
The Intercity Express of the German state railway Deutsche Bahn (DB) is a continental European system of high-speed trains renowned for their comfort and reliability. Occasionally things go wrong, however, as happened last year when two rail carriages needed repair. Both required a new secondary roll stop, a heavy steel component bolted to the underside of each passenger car that limits lateral play on tight curves to ensure safe cornering.
Self-evidently it is a safety-critical part whose method of manufacture rail engineers are reluctant to change. Nevertheless DB was forced to do just that, as the secondary roll stop is not a regular service item but an accident repair part and therefore not normally held in stock. Two were needed quickly but the problem was that the usual supplier was quoting 10 months to deliver the castings, after which they still had to be machined by the usual subtractive process. Moreover the quote was for a minimum order quantity of four castings.
Florens Lichte, DB’s Head of Additive Manufacturing explained, “Apart from the extended lead-time for delivery, we would also have had to pay serious money for the initial tooling.
“None of this was an option for us. We needed to reduce the downtime of the railcars drastically to get them back into service quickly and economically. So we decided to 3D-print the components using the WAAM process.
“A cooperation was set up with Gefertec, which manufactured the parts at its headquarters near Berlin. We were able to reduce the lead-time by five months, added to which the overall cost was 30 percent lower.”
Tobias Kruemberg, CEO of Gefertec commented, “Our company produces WAAM 3- and 5-axis CNC metal 3D printing systems and we also offer a subcontract manufacturing service. The benefit of our technology is that many kilograms of metal can be deposited in a relatively short time.
“When DB came to us, we saw the additive manufacture of their secondary roll stops as ideal for our technology. It is perfect for the rapid production of high value metal parts in small quantities at reduced cost, so this application amounted to a sound business case.”
The two components were duly produced on an arc405 5-axis WAAM machine in a cycle time of 36 hours each. The raw material is standard welding coil that does not require the safety precautions associated with powder-bed layer-by-layer fusion technology. In this case, 1.2 mm diameter SW 100S NiMoCr wire was used to produce two high tensile, fine grain structures each measuring 250 x 216 x 312 mm and weighing 36.3 kg.
It is at this point that detail on the finalisation of the original project is lacking. So Richard Kingsbury, Managing Director of Gosport-based machine tool solutions specialist, Kingsbury, decided to produce a video recreating the manufacturing process in its entirety, including interviews with the decision-makers involved.
