Precise Simultaneous Five-Axis Machining

StarragHeckert AG (www.starragheckert.com) has designed its STC Series of five-axis, simultaneous machining centers to tackle complex structural parts that often involve extremely thin walls and removing 90 percent of the raw material. The company says the machines can be used effectively to shorten cycle times and increase productivity in machining complex structural parts for aircraft and turbine constructions, as well as tool and mold manufacturing.

The series includes the STC 1000, STC 1250 and STC 1600 that differ in clamping surfaces and working areas. Because re-clamping a workpiece can affect precision, the machines are designed to allow shops to cut workpieces on five sides from any angle to produce inclined, curved and free-form surfaces with a single-clamping setup.

For low-vibration material removal under extreme cutting conditions, machine transverse and longitudinal beds are positioned in a T shape, and CNC rotary ables run on the longitudinal beds on large, rigid linear guide rails with roller guidance systems. The rotary axis clamps hydraulically.

Machine columns move on the transverse beds, also with large rigid linear guiderails and roller guidance systems, while single-axis swivel heads with working spindle units move vertically. Spindle units swivel around horizontal A axes. The machines execute these movements simultaneously with all their linear feeds driven through pre-stressed backlash-free ballscrews and high-dynamic maintenance-free three-phase current servomotors that include digital control and automatic feedback.

Standard machine versions are made with geared, 8,000-rpm spindles on their single-axis swivel heads. Two-step gearboxes deliver 940 Nm of torque, and shops can select 15,000 or 24,000-rpm 70-kW spindles with 100 percent duty cycles. Oil/air lubrication systems keep spindle bearings running smooth, while optical strain sensors monitor oil supplies for each bearing point.

Siemens Sinumerik 840D CNCs together with Simodrive drives provide a complete and totally digital system for the STC machines. Shops also can choose a Fanuc 30 series CNC. High processor output of the NC kernel and functions such as look-ahead, dynamic pre-control and jolt limitation also are available.

Linear optical absolute position sensors constantly deliver up-to-date axis-position information to the CNCs. This eliminates shops having to approach reference points.

Machine controls communicate with actuators and sensors via ASI-buses, and a graphically supported diagnosis system, or service assistant module, localizes any faults that may occur within the shortest possible time and supports their elimination with diagnosis information. StarragHeckert's provides online support specialists for machine operators.

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