For manufacturing, several processes, such as laying up the raw materials in the mold had to be adjusted and rethought. With the huge size of the mold the operators are no longer able to reach out and manually put material in place in the way they can in smaller molds. In addition, as the vertical surfaces get bigger, the glass tends to slide down. These were just some of the production details that evolve into problems as the mold size increases.
It took lots of preparation and continuous dialogue to generate ideas and develop solutions that were the key to overcoming these challenges, says Kristiansen.
Molded Fiber Glass Companies (MFG) has been manufacturing blades, spinners, nose cones and nacelles for wind turbines for more than 25 years. “The units have to get cheaper to install, cheaper to operate and therefore provide more margin for the bottom line customers, the operators and finally the users of electricity,” says Carl LaFrance, senior vice president, quality. That means producing longer blades.
“When you double the length of a blade, you quadruple the amount of composites in it, unless you start narrowing down the design margin,” he says. A tighter design requires less variability in processes and materials. To gain more control over those factors, MFG is constantly looking for better materials, finishing technologies, and measurement and inspection methods.
“We are driving our vendors to change their processes to reduce variation. Variation is the enemy,” LaFrance says. MFG wants to know, for example, exactly how much glass is in a particular volume of laminate. “If you put in more glass than you need, you’re paying too much money. If you put in less than you need, you risk failure.”
It’s essential to ensure that the glass goes in at exactly the right orientation or combination of orientations. “Blades are primarily unidirectional, because you want to tailor the strengths and stiffness in a very specific direction from root to tip,” says LaFrance. “If you are off by a degree in how you lay that material down, it can affect performance.”
MFG has developed some proprietary processes to help improve accuracy and is beginning to use robots for the production of smaller turbine components. (Blades are too large.) “We’re also doing some work using pultruded components for wind turbine blades, but there are technical issues associated with it that have not been resolved,” says LaFrance.