Almac Engineering has seen its investment in a Harrison Alpha 550 PlusS two-axis CNC/manual lathe pay off in terms of its accuracy, flexibility and productivity.

Alan Cox, Managing Director of Almac Engineering, Peterborough, has seen his investment in a Harrison Alpha 550 PlusS two-axis CNC/manual lathe from Derek Robinson Machine Tools, Leicester, pay off in terms of its accuracy, flexibility and productivity, particularly on a demanding contract to manufacture precision components for a machining centre. The contract, to machine a rotary hydraulic manifold for the 'C' axis milling/boring head on a very large machining centre, placed demands on Almac which would have made the contract extremely difficult and uneconomical without the Alpha. The rotary manifold, part of a set of three rotor/stator sets completed by Almac, was manufactured in EN9 alloy steel with dimensions of 705mm long x 474mm (largest diameter) and weighing in at approximately 200kg.

The sheer size of the component brought some problems, with it having to be secured in the lathe using a Pratt Burnerd International four-jaw chuck, tool steady and specially made adapter.

The internal detail was also extremely complex, incorporating a series of internal grooves of various widths, designed to accept electrical cables and seals, and the passage of fluids.

These fluid transfer grooves incorporate radial drillings at their base, which interconnect with axial drillings in the casing for the passage of hydraulic oil and coolant.

The grooves were particularly demanding to machine, with surface finish levels of 0.8mm and filleted corners of 1,3mm radius.

Access to some of the internal faces was extremely restricted, however Almac found a way round the difficulties: 'Modified 'throwaway' carbide tooling was used and attached to a special holder and locally made boring bar.

This was easier than using special form tooling, as two or three form tools would have had to be manufactured for each groove,' says Alan Cox Machining the groove radii was made easier by calling-up tools from the Alpha software tool library.

Once the tooling is registered in the library, the software (for future reference) records tool characteristics and offsets.

When the tools are then subsequently called-up during lathe programming, tip and corner radii are automatically compensated for.

The rotary manifold work was programmed and executed using the lathe's AlphaLink CAD/CAM system and AlphaSystem semi-automatic, autocycling and electronic handwheel (manual) modes of operation.

These systems are accessed through a twin keypad configuration, providing the operator with the choice of ISO CNC operation from the right-hand keypad and AlphaLink and AlphaSystem interactive operation from the left-hand keypad.

The right-hand ISO keypad has full CNC facilities, utilising canned cycles G70 to G76, tool nose radius and wear offsets, tool path graphics, inch/metric conversion and background editing.

Programs can be entered and/or edited directly at the machine.

The left-hand keypad generates on-screen programmed sequential operations in simple question/answer page format for parallel turning, chamfer, radius, taper and multi-start threads.

Another powerful 'user-friendly' feature of the Alpha 550 is that graphical representation and CNC control is through the super compact GE Fanuc 21i-T controller, featuring a grey-scale TFT (thin film transistor) flat screen.

The 21i-T has a powerful memory, providing instantaneous response to program commands through ultra high-speed serial communications (single optic fibre).

Troubleshooting and data input/output are accommodated with a PCMCIA modem slot.

The Alpha 550, selected at MACH 2000, has brought considerable production flexibility to Almac Engineering, a BS EN ISO 9002 company that has gained an enviable reputation for manufacturing close tolerance components.

The Alpha's abilities are not lost on Alan Cox: 'The Alpha has far exceeded my expectations with regard to the accuracy achievable, particularly when you are stretching the machine's capacity as we are.