MAG completes third generation series with NBH 1000 5-axis machining centre

The design of all MAG NBH models is based on the jig boring machine principle. This means that the workpiece moves in Z-axis direction. The NBH third generation machines are built on a heavily ribbed, one-piece cast iron machine bed for the high damping properties. All linear axes are equipped with generously spaced guideways. These preloaded, backlash-free linear units, equipped with cylindrical rollers, ensure high rigidity and load capacity. They provide dynamic travelling speeds and stick/slip-free position movements with high positioning and circular accuracy. A distance-coded, direct distance measurement system is integrated into the rail guide. However, absolute glass scales are available as an option for all NBH models. Special emphasis has been placed on fast and reliable chip removal. Four robust spiral conveyors on the NBH 800/NBH 1000 enable large machining volumes to be easily processed and chips can be removed towards either the front or the rear of the machine. The machines are equipped with maintenance-free, brushless, digitally controlled three-phase servo-motors of a completely closed design. Subordinate support and diagnostic functions are transferred from the CNC to the axis drives for total position control. In general, power is transmitted directly onto the precision ballscrew spindles with special plastic star couplers for better damping and reduced noise. A special option package and corresponding ballscrew drive construction can provide accelerations of up to 10 m/sec2. Direct torque driven rotary tables provide high acceleration and dynamics while an absolute encoder ensures precise positioning and repeatability at the start of production or after an emergency stop, avoiding time-consuming referencing. Unlike conventional worm or bevel gear drives, backlash- thus wear-free drives require no oil lubrication. The use of identical parts throughout the entire series also reduces spare parts inventory. Two index bolts on the table pre-position the pallet after changing. Four conical clamping cones ensure precise positioning and high repeatability. The clamping cones are blown out and rinsed after the pallet has been lifted. Fast 180° swivel pallet changers are generally used for pallets up to 1,000 by 1,000 mm. This significantly reduces pallet change times even on the larger machines. For example, a direct comparison of a NBH 290 from the predecessor series with a linear pallet changer and the NBH 800 shows that the pallet change time has almost been halved, from around 39 to 20 seconds. The pallet set-up station can be rotated smoothly through 360°. This also makes elaborate clamping devices fully accessible. A pneumatic station lock every 90° also facilitates the set-up process. The station and the table can be equipped with a two-way or six-way hydraulic clamping system for automatically actuating the clamping devices. The feed lines can be laid either pneumatically or hydraulically, as required. Thanks to a comprehensive range of engine and gear spindles with production-optimised speed variants and a wide torque range, any NBH can be optimally adapted to the specific machining task. Directly driven spindles with the cartridge design and tube version gear spindles offer quick and easy service for maintenance work. Directly driven spindles, with their short run-up and stop times and speeds up to 16,000 rpm, have proven to be most effective for machining light metals. For heavy-duty cutting, gear spindles with two-level control gears are used. As well as providing economic machining of steel and cast iron, the 10,000 rpm gear model is capable of tackling aluminium materials as well. The spindles feature four-way (tandem) double-O main bearings. These extremely rigid working spindles with a bearing diameter of 100 mm (optionally 130 mm) ensure high running accuracy. A labyrinth seal, supplied with an additional air purge, prevents the intrusion of coolant and other contaminants. The very slender, optionally extensible, spindle tube design allows for optimal 'immersion' into complex workpiece geometries and fixtures. A swivel head is available from NBH 630 size machine upwards for the machining of complex workpieces in one setting, multi-sided machining, drilling or surface machining in different angles as well as free-form surfaces in tool and mould making. The swivel axis – from the range of 0° (= horizontal spindle position) to 225° (180° = vertical spindle position) – and the NC rotary table can be driven without backlash by a powerful geared motor. This design provides maximum torque for positioning and simultaneous operation. Thermal control of servo-motors, ball assemblies and gears as well as coolant temperature control support 5-axis precision. In addition to the swivel head, the NBH 800 series offers an alternative tilting/rotary table. The gantry drive in the Z-axis completes this powerful concept. The tilting/rotary table model is available with the powerful HSK-A 100 directly driven and geared spindles. Tool magazines can be tailored to production process requirements. Solutions range from simple and inexpensive pick-up disc magazines with 40 tool places, through disc, chain and linear magazines to the legendary Hüller Hille NBH cassette magazine with up to 400 tool places. If the tool is not changed directly into the disc magazine with the pick-up process, this is achieved via fast uptime parallel tool feed with a linear tool handling device with NC drive. The actual change process is handled by a fast 180° electro-mechanical toolchanger with mechanical locking of the tools when swivelling. The front cassette tool of the cassette-type magazine can be exchanged by lift truck. When starting a different workpiece series, the prepared tool cassette with the complete set of corresponding tools can be changed in a few minutes. With a suitably long tool operation run time, this can even be achieved while machining. Individual tools can be introduced or removed from the magazine during machining via a tool loading station. A retractable tool drawer is available as an option for the tool loading station. Tools up to 600 mm long (optionally 800 mm for the large machines) and up to 40 kg can be accommodated.