Traub TNL32 unshackles sliding-headstock lathe concept

Bar is clamped in the spindle collet when the collet that feeds the bar through the Traub TNL32 guide bush is released. The material can then be moved 127 mm into and out of the cutting zone using the Z-axis motion of the headstock, which travels at up to 20 m/min. This flexibility provides a set-up that Geo Kingsbury describes as ideal for shorter components and for applications where a guide bush is impractical, such as when producing plastic workpieces and those machined from profiled stock. Without the need to bridge the gap between a collet and the guide bush, bar remnants are much shorter, resulting in savings in material. In addition, bar changeover is faster and eliminating the guide bush removes the need to use expensive ground stock, Geo Kingsbury points out. Another feature of the Traub TNL32 design is the absence of gang tooling and the inclusion of two turrets that are rotated as full CNC axes, instead of being indexed and clamped. A 10-station turret is mounted above the spindle centreline, below which is a nine-station turret. Both move in three orthogonal axes with 20 m/min rapids in each axis. Used conventionally, bar up to 305 mm can be fed through the lathe's guide bush with cutting tools always close to the point where the material is supported, thus providing the advantages of Swiss-type turning, including maximum rigidity and accuracy when machining long, slender components. A patented dual drive with two separate drive trains has been integrated into each turret to reduce cycle times. While one tool is in cut, the next tool can be accelerated and is immediately available at full speed after the turret has indexed. Jerky acceleration and delay that were previously unavoidable when trying to minimise idle times are avoided. Chip-to-chip time is under 0.3 sec for adjacent turret stations, thanks in part to the dual drive and also because CNC turret rotation eliminates the need for mechanical locking, maintaining similar low levels of non-cutting time. All turret stations can carry either a static turning tool or a live cutter. The ability to position the turrets at any angle through 360º means that multiple toolholders can be used, increasing the number of cutters in the working area. The large circumference of the TNL32's turret presents many more tools to a workpiece than is possible with a much shorter gang tool arrangement, reducing the number of set-ups and increasing productivity. The 8,000 rpm counter spindle moves in the X, Y and Z axes, as it is mounted on the same compound slide as the lower turret. The spindle head swivels independently around the same axis as the turret to present a parted-off component to a robust rear endworking tool carrier for completion of complex reverse-end operations. The counter spindle has a 0.001º C-axis to allow prismatic operations using three, 10,000 rpm live stations in the backworking carrier, with a choice of either high speed or high torque settings. Four stations are provided with individually controlled internal coolant supply. While work is in progress on the reverse of a component, front-end machining with one or two tools can be carried out simultaneously in the 8,000 rpm main spindle. This is of thermo-symmetrical design and incorporates liquid cooling to prevent spindle growth. It also has 0.001º indexing for use in conjunction with driven turret tooling to achieve prismatic features. Simultaneous machining with three tools ensures high productivity. All tools can be programmed with individual feedrates to optimise cutting conditions.