Modifying the LFI process makes bigger products possible
Traditionally PWC hulls are produced using Sheet Moulding Compound (SMC), ie, glassfibre-reinforced polyester resin. Camoplast looked at a number of alternative manufacturing methods and materials, finally concluding that the best way of meeting customer specifications was to use a modified LFI process capable of producing a strong, lightweight hull with an excellent surface finish, and of reducing manufacturing costs as well.
In the LFI process, the glassfibres are discharged into the mould simultaneously with the PUR system in a single process. The PUR mixing head, mounted on a robot arm, is equipped with a chopper which cuts fibres to length. The robot moves the mixing head over the open mould during the pour process. The mould is then closed to give the product its final shape. The main challenge in producing the large PWC hull using this process is the PUR’s very short curing time.
Camoplast worked with its technology partners KraussMaffei and Bayer MaterialScience to develop the CLF (Camoplast Long Fiber) process. KraussMaffei’s main contribution was to modify its proven LFI process by boosting glassfibre output rate from 180 to 300 grams a second in order to deliver a high-strength structural part. Concurrently Bayer MaterialScience developed a unique PUR formula that cures in 60 seconds, much longer than the ten seconds taken by conventional formulas. The longer curing time allows the PUR/glassfibre mix to flow readily into narrow interstices. This is necessary to produce parts with integrated ribs for extra strength. Camoplast’s readiness to innovate, KraussMaffei’s ability to modify its process and the new application-specific formula from Bayer MaterialScience all combined to make it possible to produce parts as large as a PWC hull by this method.
Strength paired with light weight
Producing the hulls from PUR instead of conventional SMC has benefits for the manufacturer and for the end customer. PUR’s lower density means that the whole craft is lighter and can accelerate faster. In this application, a hull produced in a CLF weighs 30% less than the same product produced by the conventional method.
The hull is the biggest, but also the most vulnerable component of a PWC – it comes into contact with waves that could smash it.” explains Yves Carbonneau, engineering manager at Camoplast. “To achieve the best possible drive characteristics the hull must have an optimized structural and mechanical characteristic, but it must nonetheless be as light as possible. We use a light material with integrated reinforcing ribs. This is how we achieve the necessary strength to withstand even big waves and to provide the safety that PWC drivers want.
Cost-effective, safe, environmentally compatible
For environmental reasons too, PUR resin is preferable to other materials. Polyester contains styrene and releases volatile organic compounds, posing a risk for the environment and for production workers. PUR and the LFI process mean faster production, a higher level of automation and a production system with a smaller footprint. This all adds up to clear advantages in terms of cost and safety.
KraussMaffei also contributed its expertise in mould design for the LFI process. Camoplast is now using a nickel mould for the PWC hull. This represents a considerable cost-saving compared with the steel mould required for an SMC process. Using in-mould painting, Camoplast can produce coloured parts with a flawless surface finish directly in the mould. There’s no need for a cost-intensive post-mould painting step. “Camoplast’s innovative CLF process is the most effective method of meeting the exacting criteria that the company sets for the material properties and aesthetics of a PWC hull,” says Craig Snyder, Market Channel Representative at Bayer MaterialScience.