CRYOGENIC FTR AUTODRILL

Cryogenic FTR AutoDrill for Extended-Reach Machining

MAG's 6-axis FTR AutoDrill combines a rigid boring mill chassis and its extended-reach ram with a nimble, powerful gimbal head for ultra-precise milling and drilling on massive composite and sandwich structures. The first FTR AutoDrill, equipped with MAG's multi-patented MQC (Minimum Quantity Cryogenic) tool cooling technology, will be used by Boeing at its South Carolina site, beginning in Q2 2013. The machine will be used to process high-value 787 fuselage barrels. The machine's capabilities include drilling assembly holes and milling section edges, windows and door cut-outs, said a MAG spokesperson.

This machine will be equipped with MQC liquid-nitrogen tool cooling. MQC is intended to produce smoother cuts, increased process speeds, longer tool life and reduced frictional heat and material adhesion. MQC is also eco-friendly, producing dry chips without releasing airborne mists or greenhouse gases. MQC delivers liquid nitrogen at -321° F (-196° C) through the spindle, directly to the tool tip and cutting zone.

According to Michael Judge, MAG Vice President of Cryogenic Business Development, the key to MQC's effectiveness is plumbing liquid nitrogen through the insert to allow a heat-sink effect rather than traditional chip zone cooling. "Cryogenic machining has never been done this efficiently before, with liquid nitrogen passed through the spindle and through the insert," he said. "Through-tool cooling provides the most efficient heat transfer model and consumes the least amount of liquid nitrogen, with flow rates of less than 0.1 liter per minute per cutting edge."

The FTR AutoDrill is a hybrid floor-type horizontal boring mill equipped with a 2-axis spindle carrier. It incorporates a precise machining head designed for extreme countersink accuracy, utilizing a Fischer 15 kW (20 HP) 24,000 RPM spindle equipped with HSK-50A tool interface and power drawbar. The head uses a pressure foot to sense part location, while laser sensors in the head measure the distance to the work surface and the normality of the approach angle. This real-time mold line sensing system helps ensure drilling is perpendicular to the skin.

The boring mill chassis, with its heavily ribbed, cast iron column and stiff guideway system, help provide rigidity and vibration damping for stability while machining at high speeds. The traveling-column design has an XYZ work range of 12 x 3 x 1.4 m (472" x 118" x 55"), with XY repeatability of 0.0076 mm (0.0003") and Z-axis repeatability of 0.020 mm (0.0008"). A feed rate of 20,000 mm/min (787 IPM) for X and Y axes helps provide rapid machining of large components. An electrically preloaded rack and pinion system drives the X-axis while the Y-axis is driven with twin ballscrews. Precision roller packs on X, Y and Z axes help provide stability, low friction, durability and maintainability.

The cast-steel ram carrying the machining head utilizes hydraulic tension-rod displacement compensation to maintain tool point accuracy over its full 1.4 m (55") extension. The gimbal machining head is integrated with the ram and provides ±200° of C-axis rotation and ±90° of A-axis tilt. Torque motors on the A and C axes allow positioning rates up to 60 degrees/sec (10 RPM). A W-axis drilling quill provides 100 mm (3.98") feed stroke perpendicular to the Z-axis for precision drilling.

A column-mounted double-arm tool changer and 30-pocket drum-type tool magazine travel with the column to help maximize in-cut time. Additional efficiency enhancements include Renishaw TS27R toolsetting probe and RMP 600 strain-gage spindle probe. The operator's platform that travels with the column includes a 482 mm (19") flat panel monitor for visual observation of the work zone.

The modular FTR AutoDrill is available in a variety of sizes and can accommodate many tool types and sizes, both fixed and rotating. In addition to cryogenic tool cooling, the AutoDrill can be configured for dry machining or with standard liquid coolant or MQL (minimum quantity lubrication). The machines can be arranged for single or multi-station production and can be incorporated into flexible manufacturing cells.