Fixing a plastic spoiler onto the tail door of a vehicle might seem a simple enough task, but when the spoiler must consistently protrude by no more than 1mm above the roof line, the requirement becomes a lot more precise. Indeed, in practice the tail spoiler had to be readjusted several times in order to ensure its correct alignment – a chore that required the spoiler to be fitted, the door closed, the alignment checked and then the door reopened, an adjustment made and then the door closed for checking again. In fact, previous models of the vehicle had to be taken off the track just to align the spoilers.
The vehicle in question is a luxury sports 4x4 and the quality of the build must reflect the vehicles overall excellence.
In the automotive industry, more than most, time is money and such an arduous process for what is a relatively simple assembly was unacceptable. The vehicle manufacturer's design team consulted the automotive fastening specialists at Böllhoff, who had devised innovative fastening solutions for the company in the past.
Böllhoff's long and close relationship with many of the leading car makers places it in good stead to understand the specific needs of the companies it partners. Hence, when tasked with addressing the spoiler alignment problem, Böllhoff worked with not only the automotive companies' own design and manufacturing teams, but also with that of the third tier spoiler moulding company.
The outcome is a design that creates a semi self-aligning system that simplifies assembly on the shop floor and saves a lot of costly time.
One of the initial problems that had to be addressed in the design was the fact that however precise the mouldings, the practical tolerances on holes, bolts and threads allows for misalignment. Hence, whatever fastening solution was derived, it had to be capable of taking up differences in the tolerances of the bolted fixings.
The primary challenge is that, for aesthetic reasons, the car makers wish to have a completely uniform alignment of the spoiler in relation to the vehicle roof.
The recommended product was an adapted Böllhoff FLEXITOL® all plastics fastener which has inherent tolerance compensation. The fastening system has adjustment and fastening elements.
Initial designs suggested that four FLEXITOL® would be required for the application, but in practice it was discovered that just two of the fasteners, in conjunction with four conventional screw in fixings, was sufficient. The use of an all plastics fastener raised understandable concerns from the vehicle's engineering teams regarding the "pull out" strength of the assembly. The prerequisite figure was a significant 900N, but tests at Böllhoff's research facilities demonstrated that the FLEXITOL® fasteners in the spoiler application greatly exceeded that requirement.
The FLEXITOL® plastic fasteners consist of a plastic adjustment element and a plastic fastening element and is supplied as a pre-assembled assembly.
This assembly is screwed into the mounting hole in the plastic receiving part. A bayonet variant offers another way to attach the basic element. The FLEXITOL® plastic is then inserted into a keyhole-shaped receiving opening and locked with a quarter turn. A metric screw is used as fastening screw.
In the case of the spoiler assembly, the moulding manufacturer supplies the spoilers to the vehicle manufacturer with the FLEXITOL® components in place.
The spoiler assembly is just one of countless similar projects Böllhoff has undertaken in the automotive sector and many other industries. The company's range of specialised fixings aid the joining of disparate materials, provide tolerance compensation, give vibration damping, enable automatic alignment and many more. In many cases such development removes costs from the manufacturing process, improve quality, or benefit end users.
