A counter intuitive project
The Technology Strategy Board funded the SAVING project to look at ways in which Additive Manufacturing techniques could be used to reduce carbon emissions. The Direct Metal Laser Sintering process is inherently energy intensive, but can be used to create parts that are much lighter than their conventional counterparts. The environmental benefits of the process are, therefore, derived from the use of DMLS products, not from their production.
This was the principle that inspired Crucible Design, one of the SAVING project partners, to look at the design of a new seat buckle for commercial passenger jets, as small savings on the individual parts would be multiplied many hundreds of times on a large plane.
Design and manufacture
The project began with an analysis of the conventional seat buckle, and a decision to maintain a conventional structure, so that the results could be compared on a ‘like for like’ basis.
Crucible’s initial design work focussed on developing a buckle that could withstand considerable shock loads whilst minimising material volume.
Once a design had been produced that passed FEA testing, attention turned to optimising the buckle for DMLS production.
One of Crucible’s main objectives for the project was to show that parts could be made with little or no support structure, if the parts were oriented correctly and designed to work with the process.
The main issue that Crucible had to consider was minimising the number of downward facing horizontal surfaces, as these always require supports. This can be achieved by a combination of part orientation and component design. The result was a set of parts that could be ‘grown’ from the DMLS platform with almost no support structures.
DMLS parts are removed from the platform by wire erosion. The path used by the process can also be used to create some of the finer points of the part geometry.
A unique feature of AM processes is the ability to build an assembly of parts. Crucible fully exploited this ability by building the sliding clamp that locks the belt in place as part of the main body, increasing strength and eliminating assembly time.
The finished DMLS buckle, produced in titanium, weighed 70 grams. A conventional steel buckle weighs 155 grams, creating a saving of 85 grams per buckle.
An Airbus A380 configured for all economy seating has 853 seat buckles, which would result in a possible weight saving of 72.5 kg.
Research by Helms and Lambrecht* has shown that a saving of 1 kg can save 45,000 litres of fuel over the life of a large passenger plane. The titanium buckle could, therefore, save up to 3.3million litres of fuel.
This could equate to a saving of over £2m on fuel, whilst the cost of equipping an ‘all economy’ A380 with titanium buckles would be approximately £165,000.
This project has demonstrated that it is possible to design complex DMLS parts that can be made with minimum waste, and that the long term use of lightweight DMLS parts can make a significant impact on CO2 emissions.