The recent installation by Ward CNC of a Toshulin Powerturn 1600 C-M 2APC vertical boring, turning and milling centre at a blue chip aerospace manufacturer heralded a number of firsts for both the machine user, the machine manufacturer and for Ward CNC, Toshulin's exclusive UK agent. Valued at over £1/2 million, the installation is the first of its kind in Britain in terms of the breadth of technological features and optional extras specified for the contract. And it represents the highest specification Powerturn ever produced by Toshulin - a company that to date has supplied more than 13,000 machines from its Czech Republic site to customers in over 50 countries.

Not only does this application incorporate Powerturn's revolutionary new automatic 'flip' tool exchange system and full C axis capability for milling and boring, but for future use the novel addition of a grinding adapter head with auto profile wheel dressing.

The machine also has a 96-tool magazine, twin-pallet auto change and features the latest CNC control (Siemens 840D) with digital drive technology.

In addition, high pressure coolant supply is a feature - to satisfy the demands of the aerospace steels being processed - along with auto tool setting and part probing.

The result is a machine that while maintaining its reputation as being inherently highly accurate, is also playing the lead role in the world-class production cell that has been established on a greenfield site.

The Powerturn is completing a series of ten critical turning operations that once complemented by milling and welding, result in individual workpieces valued at between £70,000 and £80,000! Ward CNC acted as turnkey supplier for the contract - co-ordinating the third party suppliers of tooling and coolant services, for example - which took 12 months from order placement to installation, final commissioning and pass-off, including operator training and ongoing maintenance.

Having already supplied a number of machines to the same customer, Ward CNC's tender document had to satisfy a series of stringent machining requirements, as Ward CNC managing director, Simon Whitworth, comments: 'It was clear that high-accuracy turning was crucial, so as well as machining accuracy this meant that pallet positioning repeatability, for example, was an important consideration.

'In conjunction with Toshulin, we therefore developed a specification that not only embraced all the latest control and drive technologies but also incorporated a new design of pallet clamping.

'Set-up is everything on this job, and this is performed at the front, set-up station while the second pallet is located either in the machining zone or in the park area/manipulator.' The pallet arrangement features a new design of location that is based on four pistons that clamp the pallet onto a central spigot location with a radial key.

An air blast under the pallet clears any debris as positioning occurs.

'The result,' adds Simon Whitworth, 'is that the pallet consistently locates to +/- two microns - when a tolerance of eight microns was specified!' With a table diameter of 1,600 mm and capable of accommodating workpieces up to 2,000 mm diameter and weighing 12,000 kgs, the Powerturn's key characteristics of rigidity and stability for accurate machining are based on a series of high-quality construction features.

The machine frame is a one-piece, heavy-duty, internally-ribbed cast column mounted on the main table base (the main table drive is centrally located relative to the column).

The table base houses the main spindle gearbox, C axis drive mechanism and features pre-loaded precision SKF cross roller table bearing.

Thermal stabilisation is ensured by standard air-cooled or refrigerated recirculating oil-cooling system.

The main table can be configured as either: * Faceplate type chuck with four separately-mounted and manually-adjusted clamping jaw units; * Integral base jaw manual chuck with four separate manually-adjusted flush mounted jaw clamping units; * Three- or four-jaw hydraulic chuck with flush mounted jaw clamping units incorporating fine manual adjustment.

The main spindle drive is rated at 60 kW as standard (option for 80 kW).

A two-speed planetary gearbox is mounted vertically on the machine base.

A precision hardened and ground helical drive pinion and table rim gear finally drives the main spindle.

The result is infinitely variable spindle speed up to 3,000 revs/min with automatic gear changes giving constant power and constant torque.

Clockwise and counter-clockwise table rotation is available.

A multi V-belt drive is utilised between the main spindle motor and main gearbox.

The machine's C axis drive is based on a hydraulic table clamping mechanism that provides partial braking during table positioning and full clamping during drilling operations.

Table positional feedback is by Heidenhain encoder mounted in table centre for high positional accuracy.

The C axis drive mechanism is a separate system to the main spindle, and incorporates a hydraulically operated anti-backlash double split helical drive pinion and separate axis drive motor to ensure a high degree of positioning accuracy.

The live milling spindle accommodates boring, milling, drilling, tapping and leadscrew threading.

It boasts infinitely variable speed in two or three gear ranges at constant power and constant torque offering up to 3,000 revs/min and 28 kW power.

Clockwise and counter-clockwise spindle rotation is available with spindle orientation (M 19).

The cross-rail assembly elevates to position the ram head to optimise cutting conditions on workpieces of varying size (up to 1,900 mm).

Vertical adjustment of the cross-rail height is by trapezoidal screw through a worm and wormwheel gearbox, powered by synchronous AC motor.

Cross-rail positioning is to defined heights in fully programmable increments of 100 mm with a repeatability of 0.02 mm.

Combined guiding is on hardened and ground guideways incorporated in the main column.

Front guideways are heavy-duty sliding type with sideway guiding incorporating pre-loaded rolling elements.

Pitching of the cross-rail is provided by hardened toothed strips with hydraulically actuated positioning units.

Cross-rail clamping is by means of clamping jaws in conjunction with hydraulic clamping cylinders.

Telescopic steel slideway covers protect the elevating guideways.

The cross-rail position is achieved by manual operation via the operator's pendant, by MDI or programmable through the NC program.

The saddle assembly incorporates 16 sets of pre-loaded recirculating linear roller bearing packs fully supporting the ram from all sides and a further 14 sets, pre-loaded with active hydraulics that support the saddle on the crossrail assembly - for exceptional accuracy and long-term performance of the main machine moving elements.

Offering exceptional levels of accuracy and rigidity, the main ram assembly is of hardened and ground forged steel having a 240 mm by 240 mm cross section.

Powerturn features the latest development of heavy-duty internal clamping of adapter heads to a unique Toshulin patented design incorporating services for hydraulic tool clamping, milling drive, air purge and three separate coolant delivery systems.

Individual feed drives for axes X and Z are by means of AC servo motors operating under closed loop control.

Axes are driven through precision pre-loaded ballscrews.

Toshulin's revolutionary design of toolchanger allows the automatic changing of turning or milling adapter heads, which then allows the automatic changing of 50 ISO turning and milling tooling directly into the ram adapter for either axial or radial turning or milling.

Processing Nimonics and Inconels, Ward CNC worked closely with the suppliers of both coolant system and tooling to avoid any problems likely to result from the 'stringy swarf' that is a characteristic of these aerospace materials.

The Powerturn delivers coolant at 64 bar and 120 l/min into the toolholder then onto/through the tool tip.

High-pressure coolant systems of up to 350 bar can be offered.

Carbide tooling was specified throughout; 75 per cent of it being special-purpose.

While the Siemens 840D CNC features a second, smaller screen for tool wear and collision monitoring, Renishaw auto tool setting and part probing are also accommodated by the control system.

Mounted on the main column within the machine's work zone, the automatic toolsetting unit is based on a hydraulically operated probe head carrier that telescopically extends from behind a protective guard.

The workpiece probe carrier is mounted in the tool magazine and performs in-process gauging via CNC sub-programs using canned cycles, with additional possibilities for: * Orientated spindle stop for gauging broken contours; * Gauging of round deviations via multi-orientated spindle stop; and * Auto updates of tool offsets.

The automatic profile grinding and wheel dressing equipment are also held in the machine's ATC and are automatically changed into the ram for straight or profile grinding.

Wheels of up to 350 mm can be accommodated for straight or profile grinding.

Using the machine's X and Z axes, wheel dressing is by diamond-impregnated wheel.

Interestingly, grinding trials produced finishes of 0.4 Ra and polishing to 0.3 Ra! As expected, the Powerturn commissioning process involved a series of rigorous ISO machine accuracy and capability tests.

And the machine passed with flying colours.

For example, for parallelism of the vertical guiding surfaces on the column in relation to the table axis - measured in two planes and in three positions of the crossrail stroke - the allowance was 40 microns, and the machine recorded 20 microns.