To avoid purchasing a 4-axis machine, engineering company chose a CNC bed mill with universal spindle head to mill, drill, ream and bore many of its smaller fabrications.
Barnsley-based Qualter Hall has installed an MTE Compact Plus bed mill with universal spindle head from Warwick Machine Tools to mill, drill, ream and bore economically many of the smaller fabrications it produces for the nuclear, railway, mining and other industries. Said Production Foreman, Alan Greenwood, 'We were using a 6000 x 1000 x 1700mm travelling column mill to machine some components that would fit on a machine with an X-axis one third the size. Clearly we needed to find a more cost-effective method of manufacture.

'The large machine has a programmable swivelling head which is necessary for producing holes in angled surfaces of some fabrications, as they are too big to rotate.

We therefore needed a universal-head mill but did not want to invest in a full 4-axis CNC machine.

The 3-axis MTE Compact Plus, on which the spindle angle is manually adjusted in one degree increments and whose axis travels are 2000mm x 800mm x 800mm, was the economic answer.' A factor in favour of this Spanish-built machine was the Heidenhain control with digital drives, which is the same as that fitted to the travelling column machine.

Consequently it was an easy matter to transfer programs for machining the smaller components directly to the new mill and start production immediately.

In addition, Warwick Machine Tools offered a good price and prompt delivery.

Several different types of fabrication are currently put on the machine for nuclear and railway projects.

Two particular parts need the spindle head swivelled to the horizontal to complete the cycle, while on one fabrication the head, which has a built-in hydro-mechanical tool clamping system, is angled at seven degrees to the vertical to drill holes perpendicular to an angled surface.

Specification of the machine includes ISO 50 spindle taper suitable for heavy metal removal rates and 4.5 tonnes maximum workpiece weight.

Spindle speed is in the range 40 to 3,000 rev/min delivered by a 22kW AC motor via a two-speed helical gearbox.

Cutting feed is up to 4m/min and rapids of 10m/min ensure short non-machining times, although the latest MTE Compact Plus has an even better specification offering 10m/min and 15m/min maximum feed rate and rapid traverse respectively.

Each servo drive acts through a pre-loaded double-nut ballscrew.

Direct measurement using linear scales that resolve to 0.001mm avoids the inherent inaccuracy of rotary encoders and allows positioning accuracy to better than 10 microns and repeatability to within 7 microns.