Let The Spindle Do The Picking

Claiming to be the first machine tool manufacturer to introduce the idea of a "pick-up spindle" CNC production lathe, Emag Maschinenfabrik (Salach, Germany, and Farmington Hills, Michigan) exhibited its first "VSC" machine at Düsseldorf, Germany's METAV machine tool show in 1992.

Since then, Emag has delivered more than 5,000 machines in 20 varieties worldwide, mostly to the automotive industry and its suppliers. Emag also has had to face more than a dozen competitors, mostly from Germany and Japan.

Thanks to linear motor drives, today's production lathes with two or more operating axes—or front-loading CNC chuckers that incorporate fast-acting robotic or gantry-mounted manipulators—can zip between the work area and the parts magazine at speeds up to 200 m/min. Operators of these machines may consider using the spindle as a workhandling device to be inefficient.

If the shop's schedule demands continuous, high volume production, perhaps this is true. A production lathe with a linear-motor-driven gantry is much faster than a machine that incorporates a pick-up spindle. The machine with a linear motor drive also can change tooling, chucks and chuck jaws faster. It can run unattended and make job changeovers under "lights out" conditions.

So why are Europe's automotive industry suppliers buying pick-up spindle machines? Why are DaimlerChrysler, Volkswagen and Skoda equipping their plants with automated cells that contain 20 or more of these machines?

The industry's answer is security and versatility. The security is that workhandling is limited to the pick-up spindle and the conveyor. A robot might be included to link up with parts storage magazines or to unload/load pallets, but the pick-up spindle production turning system is very simple when compared to many gantry-loaded machines. Versatility means that a pick-up spindle can move that workpiece through a variety of machining operations—all the turning functions—and add on machining spindles for drilling, milling and grinding.

Emag began partnering with other manufacturers, such as Reinecker, Karstens and Hardinge. Emag also acquired Pittler-Tornos, a multi-spindle automatic lathe producer. These ventures began producing combined turning and grinding machines, among others.

Emag thought having a multi-pick-up spindle machine was important and introduced its "VSC Trio." A shuttle conveyor simultaneously transfers three blanks to three pick-up stations. After machining, the pick-up spindles simultaneously deposit the three workpieces on an output conveyor. Each spindle is served by its own eight-tool turret.

Then at the AMB show in Stüttgart, Schaudt Mikrosa BWF GmbH unveiled its "Uranos M" flexible multi-functional machining center. Also of pick-up spindle design, the Uranos M demonstrated hard-turning and internal and external grinding of an automotive timing gear. It completed the job in under 60 seconds—including rough turning the bore and fillets, finish-turning faces, finish grinding the bore and grinding corners. The pick-up spindle progresses the gear past three workstations. Hard turning, which must include substantial machine rigidity and precise workholding, is of universal interest among automotive machinists.

In Friedrichshafen, Germany, gearbox manufacturer ZF carried out some hard turning tests among three makes of CNC pick-up spindle machines.

In a typical cell for hard turning of shaft blanks with 58-62 Rockwell hardness, two Pittler PVSL vertical pick-up spindle machines performed best. In this shop, the two Pittlers have replaced four cylindrical grinders, on the basis of shorter cycle times.

In slightly more than 8 years, this idea has developed into a global market. So what's next? The German firm Traub now offers a 50W Nd:YAG laser machining option with its TNC mill-turn center. My guess is that laser machining can also be done on a pick-up spindle machine.