Absolute accuracy

The ‘Mother Machine’ term is widely used in Japan to describe an ‘ultra-high accuracy’ machine tool with the capability to produce critical features on further machine tools that have high accuracy potential.

Available through 2D CNC Machinery, the Mitsui Seiki PJ812 vertical spindle precision profiling centre has been developed to accommodate higher precision machining demands such as those required in machine tool and quality equipment, aerospace and defence, medical, optical and specific mould and die applications.

Here, the combined advantage of high static rigidity, said to be six times greater than a conventional vertical machining centre, has been built into the 3-axis machine frame with the absolute benefit of thermal growth and deflection control that is greater by some 30% over previous ‘incorporated’ production machine technologies.

MAMS is a multi-sensor based thermal growth monitoring system able to minimise the influence of temperature changes on workpiece accuracy and cut temperature generated displacement by up to 60%. This system is also able to control the thermal growth and deflection in the Z-axis by around 30% compared with previous generation technologies employed.

Further contributing to higher accuracy ‘Mother Machine’ capability is a planer-style symmetric construction with hardened and ground steel slideways and special contact elements to enhance acceleration. Mitsui Seiki’s latest development of a ‘sliding mechanism’ that is able to reduce ‘stick-slip’ helps achieve an accuracy of 0.1µm for axis feed. The PJ812 also has a centralised coolant system for its ballscrews to stabilise the precision of axis feeds, slideway lubrication and other critical surfaces. As a result, heat deformation is reduced and the distance between the Z-axis drive and the spindle is minimised.

Axis travels of the Mitsui Seiki PJ812 are 1,200 mm in X, 800 mm in Y and 500 in Z. The 1,200mm by 800mm table is able to accommodate loads up to 1.5 tonnes. Direct drive spindle choices include 30kW, 50 taper, 10.000rpm and 40 taper, 18kW, 30,000rpm versions. Rapid traverse rates are 24m/minute. A 40-tool magazine is standard and control is via Fanuc 31iM-B.

2D CNC Machinery www.2DCNC.co.uk