In 2000, the company began changing OOA methods with a resistive heating process where electricity would go through the fiber and heat the resin as well. Then RocTool evolved to its Cage System® with inductors around the mold to heat the entire surface. “It was an interesting process, but we were limited in the materials we could use,” says Mathieu Boulanger, business development director for RocTool.
Four years ago the company released 3iTech® with induction coils integrated in channels that can heat the tool very quickly. In June, RocTool introduced a light induction tooling (LIT) molding system. It features a metallic female mold and a male silicone mold. Unidirectional or woven fiber reinforcements are placed in the female mold, the male mold is closed, and then pressurized air is injected into the mold up to 420 psi. The LIT system heats up to 280 C in 45 to 90 seconds depending on the material and part. Water then cools the mold and part in one to two minutes. “The LIT system requires no preheating, provides a resin-rich surface, requires no resin injection, allows for thin walls and offers good temperature control,” says Boulanger.
With each of these developments, Boulanger points out that RocTool never considered autoclave or oven systems. “We are focused on reducing steps, and OOA is the best option,” Boulanger says. RocTool continues to improve its processes and demonstrate a variety of temperatures (useful to produce various parts) and an increase in manufacturing speed. “If a cycle time is more than 30 minutes, we wouldn’t look at it,” says Boulanger. “Most of our cycle times are between two and eight minutes. And one of the best things is that whereas in past years we were considered exotic, today people are comfortable working with us.”
Meanwhile, Quickstep Composites utilizes integral heating/cooling for curing composite materials, primarily used in aerospace. With the company’s heat transfer fluid (HTF) process, the laminate is placed between a rigid or semi-rigid mold that floats in an HTF. A flexible membrane separates the mold and laminate from the circulating fluid, which can be quickly heated and then cooled to cure the laminate.
While conventional autoclave processing cures at 100 psi and requires long cycle times, Quickstep’s heat transfer fluid (HTF) process enables precise control of process temperature throughout the curing process, says Luedtke. The process utilizes existing autoclave-qualified prepregs so as to limit recertification costs. On one prepreg system, the process has demonstrated the ability to cut cycle times from 20 hours to four hours. “Because it can accurately control the mold temperature and its increased ramp rates, it saves on process time, energy costs, investment and overall component manufacturing costs,” says Luedtke.