Forging readily accommodates a wide variety of shapes while simultaneously imparting exceptional strength. But when it came to a highly unusual rotor arm fashioned in a three-spoke configuration, no one was sure whether it could be done.

Deca Industries Ltd., Saskatoon, Saskatechewan, Canada, is a 40-person industrial job shop that repairs heavy mining equipment. Founded in 1977, Deca specializes in serving the potash and the uranium mining industries.

This unique application arose when Deca's customer, International Mining Corp. (IMC), wanted to fix a disabled rotor arm integral to the operation of a continuous boring mining machine. As the machine cuts through potash, the rotor arm holds the tools that actually make the cuts.

Deca engineers determined that the part couldn't be repaired; rather, it had to be replaced. This was no small decision since the rotor arm is 90 in. in diameter, 4 ft thick, with three telescoping arms and a total weight of 7,000 lb. Deca began exploring fabrication options for the replacement part. Since the existing component had been a casting, Deca looked again at that method as well as machining and open die forging alternatives.

"Acknowledging all the forging advantages, a question still remained," said Francis Nagy, Deca's president. "Could this part actually be manufactured as an open die forging? As far as we knew, the rotor arm's unusual shape wouldn't normally lend itself to forging." Yet Deca was intrigued. To investigate further, Deca turned to Scot Forge, its Spring Grove, IL, supplier of forged spindles and rings.

Several steps were needed to produce the rotor arm. Nagy took the part's original blueprints and casting drawings down to Scot Forge where manufacturing details were worked out jointly. The new part started as a pancake-shaped piece of 4140 alloy base stock that was then formed into a seamless rolled ring via the open die forging process. Three torch-cut sectors were then drawn out and forged into journals.

Once the forged part was finished, it was sent to Deca for secondary processing.

"This was an enormous undertaking," Nagy said, "from the sheer standpoints of size and shape. We were amazed with the results."

When IMC received the part, it passed the quality inspection. The new rotor arm has been in the field for two years now and has performed to everyone's expectations.