A system for exchanging static turning tools quickly and easily in the turret of a fixed-head turning centre has been introduced by German manufacturer EWS Weigele GmbH, whose products are sold in Britain exclusively by GEWEFA UK (www.gewefa.co.uk). The new Varia.VXT quick-change system joins the Varia.VX range introduced a few years ago for the rapid exchange of driven tools in lathes. Existing users of the latter tool holders can utilise a special VXT interchangeable insert to allow fast static tool change to be incorporated cost-effectively into the same turn-mill centres and multi-tasking lathes.
Designed specifically for repeatability, precision and stability during turning operations, the VXT mechanism is particularly compact, enabling machining to take place very close to the turret, allowing extra flexibility when programming cutting cycles. The holder also exhibits extreme rigidity, which is so important when cutting with the component rotating to prevent deflection of the tool tip and to discourage chatter, leading to a superior surface finish on the workpiece.
At the heart of the tool holding innovation is a double-cone flex system with widely spaced support points. Elasticity designed into the second cone in the rear part of the adapter, combined with additional clamping screws in the shank area, gives the system outstanding damping properties, minimising vibration and maximising tool life. The dual face and taper fit of the tool holder in the EWS interface, which is mounted in the turret, ensures not only high torque transmission but also precise orientation of the tool tip.
Repeatability of tool positioning is ± 2 microns and transmissible torque is up to 160 Nm with the VXT3 interface, or 200 Nm with the larger VXT4, although these figures are likely to be revised upwards following current, ongoing tests. Maximum through-tool coolant pressure is 80 bar. VDI and BMT tool holders are available for star turrets.
Quick-change capability, whether of static or driven tools, drastically reduces tool changeover times, raising productivity. The modular nature of the Varia range helps to make this advantage affordable and is especially well suited to factories where a diverse range of workpieces is produced, which is the case in most subcontract machining shops.
