The power of one

As a result of running its parts on a Hardinge Twin Turn 65 CNC turning center, Kronenberger Manufacturing got a two-year ROI — plus faster cycle times, better JIT response, and simplified operations and scheduling.

Kronenberger Manufacturing uses a special tooling arrangement on its Conquest Twin Turn 65 and completes parts in one setup. Hardinge's Dead-Length collet provides longitudinal part accuracy and holds parts for heavy face-machining loads.

Kronenberger's most complex part requires six operations on both ends. What once took two or more conventional machines with at least three setups each and a lot of manual handling is now done in one setup on a single Hardinge Conquest Twin Turn 65 CNC turning center.

Ten-station upper and lower quick-change VDI turrets on the Conquest Twin Turn 65 can work at either or both spindles simultaneously. The main spindle (left) delivers 25 hp and the secondary (right) 15 hp.

Gunter Kronenberger is a fan of the single setup. The president of Kronenberger Manufacturing in East Rochester, N.Y., says his goal is to "grab parts once and finish them complete." However, this simple goal is made complex by the parts being machined — small diameter, precision components for optical instruments, which require four to six operations and two or three separate setups on conventional equipment. Realizing this was hurting the company's competitive edge, Kronenberger took the plunge and invested in a big ticket, multitasking turning center.

"With a typical $100,000 to $150,000 investment, we could have gotten a one year ROI, but no strategic or competitive advantage," says Kronenberger. The machine he did purchase finishes parts in a single setup to cut lead times by one-third, lower machining costs by 40 to 60%, reduce part handling, and easily run more complex parts. Geared specifically for multi-operation parts, the Conquest Twin Turn 65 from Hardinge Inc., Elmira, N.Y., sports eight axes, twin spindles, and twin turrets. What makes this CNC turning center effective is that both turrets can work on either or both spindles simultaneously, while most turning machines have turrets dedicated to a specific spindle. In addition, these two 10 or 12-station VDI turrets provide bi-directional indexing and accommodate a larger number of tools, requiring fewer setups. All stations have live tooling capability for cross and endmilling/drilling operations. And standard C-axis contouring on both spindles is ideal for milling, drilling, and tapping work.

Along with these features, the Twin Turn's B65 Dead-Length collet chuck system improves longitudinal accuracy by rigidly holding Kronenberger's parts during heavy face-machining loads. Its cast iron base is reinforced at key points with a polymer composite for optimum stiffness and vibration damping. To further damp vibration, the machine controls turret movements with separate linear guides and rails for the upper and lower turrets.

So far, Kronenberger Manufacturing has run about 10 different parts on the Twin Turn, getting its feet wet on a family of five parts involving X, Y, and Z-axis work only. Workpiece materials range from 303 stainless steel to aluminum and brass. Diameters run from 1 ⁵ /8 to 2 ¹ /2 in.

Parts with a total of six operations on both ends previously required three setups on two machines. Now, both ends are machined simultaneously in a single setup. An automatic barfeeder moves stock through the Dead-Length collet of the main spindle. Then, the upper turret performs the operations on the right end of the part. After those are complete, there comes a hand-off. The secondary spindle advances, gripping the part, while the upper turret does the cutoff. Then the right spindle retracts and completes the part. Four to six operations, both ends, are done in one setup.

Previously, Kronenberger had a lot of manual handling, in-process part storage, and cumbersome part scheduling and programming — all adding up to long cycle times. Hardinge turning centers, according to Kronenberger, easily handle the company's jobs that can range from 10 to 10,000 parts, with typical tolerances on dimension of 0.0002 in. and 8 µin. on finish. Job-to-job changeovers average three a week per machine. Each job typically requires six operations on both ends, including turning, threading, centerline drilling, boring, and cutoff.

With an extra day of training on C and E-axis machining, Kronenberger also runs more complex parts in a variety of modes using all eight axes. One of these multi-axis parts was produced on two machines, a lathe and a mill. With the Twin Turn machine, the shop mills the part as a live-tool operation with both turrets working on either spindle or both spindles simultaneously.

For another complex job, each turret machines two different parts simultaneously on the main and secondary spindles, or the two turrets work together on the same part in either the left or right-side spindle. The machine's Y-axis lets operators perform precise live off-center milling and drilling. "It all saves labor because only one operator is necessary," says Kronenberger. Reduced handling frees operators to check and inspect delicate parts, while providing delivery at least twice as fast, he adds.

In an effort to streamline its production even further, the company is also installing a new Hardinge Conquest GT27 Autoload gang-tool turning cell dedicated to 10 different high-volume production parts requiring faster turnaround times. An inspection area will be located between the machines so that the same operator can tend the cell while gaging parts.