Asquith Butler introduces a mill-turn centre capable of meeting nuclear industry tolerances

Capable of achieving micron tolerances, Starturn machines are based on Asquith Butler's established Starcut range of 5-axis prismatic machining centres with the addition of a 3, 4 or 5 m turning table. (This addition can be retrofitted to Asquith Butler machining centres already in the field.) Specific installations of 9 by 4 by 1.25 m Starcuts have achieved flatness and straightness accuracies of 12 microns over 9 m and ball-bar circularity of under 15 microns in the main working plane, reports Asquith Butler. Linear axis travels range from 3 to 30 m in X, 3 to 6 m in Y, and 1 to 3 m in Z. Cutting feedrate is up to the rapid traverse of 20 m/min to maximise metal removal and minimise idle times. Rotary axes are 360º C-axis on the ram and 220º on the A-axis a head, both indexable in 1º increments or servo operated, enabling everything from 5-sided machining to fully interpolative 5-axis profiling. Automatic exchange of multiple milling heads, 50 kW of spindle power and speeds from 3,000 to 12,000 rpm allow rough, semi-finish and finish milling, according to the type of head chosen. In turning mode, the 100 kW of power available allows good all-round turning performance with high precision finishing, states the company. The rotating ram allows up to eight Capto C6 or C8 turning toolholders to be mounted on a turret-type attachment to suit the machining application, avoiding manual intervention for tool change. Positioning and clamping is achieved using a Hirth coupling and four pull studs, allowing high metal removal rates. If more turning tools are needed to complete a cutting cycle, the requirement is met by automatic exchange of the turning head or individual tools. Turning tool attachments to accommodate long bars for internal boring are also available. The chain-type magazine for automatic exchange of prismatic machining cutters and turning tools has 60, 80, 100 or 120 pocket options. Coolant delivery to the cutting area is by external flood as well as advanced, high pressure, internal through-the-spindle systems. Positional feedback to the Fanuc, Siemens or Heidenhain control is via linear scales and high resolution rotary encoders to ensure utmost precision. Asquith Butler has been working closely with a number of manufacturers involved in the manufacture of large high integrity pumps, valves and pressure vessel components. Volumetric and thermal error mapping and compensation of Asquith Butler machines is available using a system developed by the company in association with the University of Huddersfield's Centre for Precision Technology (CPT).