LATHE WITH KINEMATICALLY ACTUATED TURRETS CAN HAVE THREE TOOLS IN CUT

A new design of twin-opposed-spindle bar automatic has been introduced by the German manufacturer, Index, that distinguishes itself by a novel turret guideway system having a cast iron plate sliding over ceramic-coated steel strips. It is several times stiffer than traditional slideways, has better damping characteristics and is also more compact, giving additional space in the working area. X- and Z-axis drives to the upper and lower turrets are via kinematic rods behind the bed. Both turrets also have a conventionally driven Y-axis stroke of 70 mm.

The opposed spindle is not only powerful but also has the unusual option of 150 mm of X-axis movement in addition to 600 mm of longitudinal travel. By adding the extra degree of freedom in X as well as having the usual Z-axis motion, and electronically coupling them with the X / Z movements of a lower, double-sided, 24-tool turret (optionally available in place of the single-sided version), Index provides the ability to have three tools in cut simultaneously.

The machine is available from sole UK agent, Geo Kingsbury, in two sizes designated SpeedLine C42 and C65, the numbers representing the maximum bar capacity in millimetres. A full C-axis and 20 kW / 105 Nm of spindle power are provided at both ends, delivering top speeds of 6,300 rpm and 5,000 rpm for the respective models. Clearance between the 140 / 160 mm diameter chucks for between-centres work is 615 mm. 

The opposed spindle is not only powerful but also has the unusual option of 150 mm of X-axis movement in addition to 600 mm of longitudinal travel. By adding the extra degree of freedom in X as well as having the usual Z-axis motion, and electronically coupling them with the X / Z movements of a lower, double-sided, 24-tool turret (optionally available in place of the single-sided version), Index provides the ability to have three tools in cut simultaneously.

This is achieved by having the upper 12-station turret and the left face of the lower turret machining a component in the left hand spindle while the ‘slave’ right hand spindle follows the latter turret around, enabling a parted-off component to be machined using the right face of the lower turret. In other words, the X- and Z-axis movements of the lower turret resulting from the cutting cycle in the left hand spindle are continually allowed for in the programmed movements for back-working. The only limitation when cutting with three tools is that the Y-axis movement of the lower turret cannot be used for front-end machining, as the opposed spindle would be unable to follow.

Idle times are minimised by fast rapid traverse rates in X, Y and Z of 25, 50 and 12 m/min respectively. A steeply angled bed assists swarf removal from the working area of these 6.5 tonne mill-turning centres, whose 5 kW / 16 Nm / 6,000 rpm driven tool capacity is available at all 12 stations of each turret. Noteworthy too is polygon generation using a head mounted directly on the counter spindle rather than on a turret, ensuring vibration free machining and hence greater accuracy and longer tool life, especially on alloy steels.

Working area of the Index C42/65 showing three tools in cut simultaneously, made possible by endowing the right hand spindle with two linear axes so that it can shadow the lower turret as it assists machining a component in the left hand spindle.