Cylinder Bore Coating Comes to Prime Time

To date, lightweight motorblocks use cylinder liners, but there is now a practical alternative in twin-wire arc spraying, an extremely cost-effective technology for coating cylinder bores. HELLER Machine Tools, L.P. (Troy, MI) offers an innovative technology for coating cylinder bore surfaces of lightweight automotive aluminum engine crankcases, imparting a durable material, extending engine life, and enhancing performance.

Partnering with Daimler AG and other partners, Gebr. HELLER Maschinenfabrik GmbH (Nürtingen, Germany) has industrialized all the steps of the process and developing the technology into a reliable process known as HELLER CBC (CylinderBoreCoating), a process that has been integrated into volume engine production.

The twin-wire arc spraying process continuously melts iron/carbon wires and sprays them onto the cylinder bore surfaces of the lightweight aluminum crankcase with the help of a nitrogen gas flow.

Compared to other thermal coating processes, the technology is considered extremely cost-effective and technologically superior–a reliable, repeatable, highly controllable economical process that vastly improves the cylinder bore surfaces, reducing wear and promoting long-life. Spray particle velocity 60-80 m/s and spray particle temperature up to 2000 deg C.

Besides the primary coating process, the CBC machining process at HELLER includes fine boring, roughening, finish honing to expose pores, and finish machining — all accomplished in a complete manufacturing system consisting of the innovative coating module, HELLER CBC 200, and the HELLER MC20 machining modules. Total cycle time, including part load/unload, for an 8-cylnder engine is five minutes to six minutes. The engine blocks may be direct-loaded into the machining module  or mounted on a swiveling exchanger.

“Although the technology has only been used for exclusive low-volume series in the past, its application in medium-volume production already provides significant competitive advantages compared to existing cylinder lining technologies,” said Vincent Trampus, the HELLER vice president of sales. “The technology complies with the production rules and criteria of the automotive industry. Now it is only a small step to mass production.”

Heller Machine Tools L.P., 1225 Equity Drive, Troy, MI 48084, 248-288-5000, sales@hus.heller-machines.com, www.heller-us.com.