Precision Machining

One of BCT GmbH’s contributions to industry advancements focuses on precision machining for composite repair and manufacturing. BCT uses a six-axis, precision measuring system in applying its adaptive machining and system integration expertise to automation of composite repair.

“Our core challenge was to significantly increase the speed and precision of the scarfing process for composite components in need of repair,” says Jan Bremer, project engineer, composites. “Adaptive machining allows fully-automated machining processes on components which have individual deviations while maintaining high precision.”

For one project on a large helicopter fuselage, BCT scanned the component with a laser line scanner. It then digitized the information and adapted its usual three-axis machining path program into a five-axis program to allow for the component’s curvature. (The five-axis program can be “translated” into programs for all types of numeric control machines, Bremer says.) This process ensured that the machining tool followed the fuselage’s exact shape. “When scarfing, it is extremely important to machine to tight tolerances to avoid unwanted damage to underlying areas or components,” Bremer says.

The biggest advantages of this automated process are its increased speed, precision and traceability, he adds. Using a precise machine tool minimizes human error, while digitizing the before and after scarf allows storage of information for later documentation. The same technology can also be applied to machining of parts to ensure better fit during manufacturing.

“I see major advantages in more efficient and precise machining operations, especially when considering the possibility of running machining operations on smaller and more flexible machines that can even work in parallel on large components,” Bremer says. “This could do away with the need for extremely large machinery in many applications, greatly increasing the efficiency of today’s manufacturing processes.”

Larger-scale Production

Teijin Limited of Japan introduced its Sereebo carbon fiber reinforced thermoplastic (CFRTP) about five years ago and since that time has worked with GM and other partners on exploring its potential. What sets Sereebo apart from other CFRTPs, according to Teijin, is the longer length of its carbon fibers.

“We are able to control the distribution and the orientation of those fibers very well,” says Eric Haiss, vice president at Teijin Advanced Composites America. “So we get isotropic properties in the base material, and we can maintain those properties in the final molded parts.” With its strength and 60-second takt time (which synchronizes rate of production with rate of demand), Sereebo provides the performance required for mass production of structural parts in automobiles, adds Haiss.