Maximizing with multispindles: Drilling Performance

Before CNC lathes, most high-volume turned parts were made on multispindle, cam-driven screw machines. Setup times were long, and great skill was needed to design the cams and grind the cutting tools. However, by being able to perform a dozen or more operations simultaneously, they could produce hundreds—often thousands—of parts per hour.

Whatever happened to those old mechanical monsters? According to Giovanni Principe, they’re alive and well.

Robotic part handling increases spindle capacity and reduces floor space requirements. Image courtesy INDEX.

The multispindle national product manager for the Gildemeister line at DMG Mori USA, Hoffman Estates, Ill., Principe said he’s seen renewed interest in multispindles over the past few years, especially CNC models. These machines offer fast setup times and simplified operation, and are far more flexible than their predecessors.

“Tough metals like 4140 and 52100 steel are becoming more common, while part volumes are shrinking, tolerances are getting tighter and workpieces are growing increasingly complex,” Principe said. “All of these things lend themselves well to CNC multispindles.”

Gildemeister still makes cam-driven multispindles, and, according to Principe, demand remains high. But where the rule of thumb for justifying a cam machine is an order of a million parts or more, CNC multispindles are often employed to cost-effectively produce a few hundred or fewer pieces.

“The longest part of setup on any multispindle machine is bar changeover, an activity that might take a few hours,” he said. “If you can avoid this by standardizing on bar size or grouping jobs with like materials, setup time on a CNC machine is often a matter of changing a few tools and calling up a new program. I know a shop in Chicago that routinely does changeovers in 20 minutes or so, and most shops can do them in a couple hours or less.”

All multispindles operate on a share-the-workload principle. Each spindle typically has two (or more) slides: one for end-working operations, such as drilling and boring, and the other for turning, grooving and cutoff. On a 6-spindle machine, for example, the first spindle/slide station might turn and drill, the second station might counterbore and groove and so on until the part is completed. The part cycle time is determined by the longest of the six operations, which is why it’s important to level the machining load across all stations.