RPS introduce

Oxford Brookes Racing

to SLS materials.

Written by James Ganderton | OBR19

RPS introduced Oxford Brookes Racing to ALM’s PA 603-CF material at the beginning of the design period for OBR19

This material and the laser sintering process has allowed OBR to produce lightweight components with complex geometries and high dimensional accuracy, whilst maintaining high stiffness and strength.

The components using this material are found mostly in the front wing, where there is lots of curvature and complex interactions between elements. For example, where the flags meet the main plane, it is very important that the bond surface matches the adjacent surface on the main plane. Achieving this geometry, accurately, with a wholly composite structure can be difficult to achieve and result in an interaction with low stiffness and low location accuracy.

The solution is to simplify the closed-moulded, composite component to provide a good bonding surface to a printed component.  The composite component can then be bonded within the printed part with a joggled socket, which maintains the desired aerodynamic surface.  The thickness of the printed component is minimised in order to keep the mass low, as well as the stiffness of the composite component high.

A similar solution is introduced at the adjustable front wing flap, where joggled sockets are positioned at the ends of the flaps. The requirement for geometric accuracy here is not that a bonding surface is required, given the flaps’ adjustable angle of attack, but that the adjustment axis, and fasteners must be in the correct locations. This would, again, be difficult to achieve reliably with a wholly composite component.

The components are also used in conjunction with threaded inserts to provide ease of use when adjusting the flaps and requiring only one tool. The specific inserts used are brass Tappex Multiserts. These are pressed in place and bonded also to ensure they do not rotate and the fixture lasts through the vibrations of racing. Headed inserts are used in order to prevent pull-out.

The printed part is suitable for this as the hole positions are correct between the two inserts, meaning that, when assembling the wing, the surfaces of the flap will match that of the adjacent end plate, as designed. The strength of the material also poses a low likelihood of failure between the flap and the fixture.

Just above the adjustable flap of the first element is the extension of the second, terminating that element. The printed component is used here for its geometric accuracy as the component is finished with sharp edges and is relatively small. This would be difficult to achieve with a moulded component and the resources required to produce the core and moulds is much greater. This component is hollowed, and holes are positioned over the hidden bonded face in order to remove the internal powder. This helps to keep the mass to a minimum.

The front wing foot plates are the largest use of the ALM 603-CF. Each foot plate is made of two components, the forward and rearward parts, which are bonded together. This is due to the foot plates measuring 580mm 1n length, which exceeds the maximum build size for the desired part orientation. There is a stepped join between the two parts with a consistent bond gap between the two. The parts have raised location features with no gap to ensure correct positioning.

From the side view, the two parts are also located using a longitudinal face with no gap. The parts were bonded together on a surface table to further ensure alignment between the two.

The maJor benefit of using this manufacturing method for the foot plates is the ability to interface properly with the main plane, end plate elements and the outboard turning vane. The location of these parts relative to each other is very important in order to maintain the correct slot gap between the elements -vital for proper performance. Also, as the joggle interface, similar to other components, provides a large bonding area with a consistent gap.

The foot plates also integrate tube routing for 4 surface pressure toppings in each of the footplates. These use bends designed into the part to prevent tube pinching around tight bends. Similarly to the flap extensions mentioned previously, the foot plate components are hollowed out. To ensure sufficient powder removal, panels were added to the lower face, along with many holes where the outer surface would not be affected. The surface is then smoothed by filling the voids with silicone, followed by sanding smooth and painting.

In total, 16 car components are produced using this manufacturing method. Those highlighted in blue in the image below are all ALM PA 603-CF components.