Cutting noncut time: General Industry Coverage

Most horizontal machining centers have a rotary B-axis in addition to the X, Y and Z axes. Traditionally, B-axis tables are indexing or NC rotary-type ones. On the a51nx and a61nx horizontal machining centers from Makino Inc., the B-axis rotation is accomplished by a direct-drive (DD) table, explained Dave Ward, horizontal product manager for the machine tool builder. “A key technology on our DD tables is Inertia Active Control (IAC), which can optimize the rotational acceleration to reduce noncut time,” he said, noting that the DD rotary table uses an integral motor and provides 0.0001° resolution—3.6 million positions.

Ward explained that because machine tool builders have no idea how much weight a customer is going to put on a pallet, they set the B-axis acceleration/deceleration default speed at the worst-case, maximum-weight, maximum-inertia scenario to ensure accuracy. That’s effective, for instance, when a tombstone-mounted pallet has workpieces at the outer edges, creating a high-inertia condition. In that case, the motor has to work hard to rotate the pallet. However, if that weight is concentrated near the center, IAC automatically increases the acceleration/deceleration speed accordingly because there is less inertia during rotation.

Courtesy of Makino

With a typical four-sided tombstone, Inertia Active Control can reduce noncut time during B-axis indexing 14 to 18 percent compared to the B-axis acceleration/deceleration default speed, according to Makino.

In addition to cemented carbide, suitable workpieces include hardened steel, glass and silicon carbide.