Manufacturers of construction plant, large engines and prismatic components can produce ever more complex parts to higher machined tolerances on two CNC table-type, horizontal-spindle borers.
Manufacturers of construction plant, large engines and prismatic components for the petrochemical industry are not immune from the need to produce ever more complex parts to higher machined tolerances. Companies involved in these sectors may therefore be interested in two new, table-type, horizontal-spindle borers launched by the Japanese manufacturer, Kuraki, said to be the most accurate and robustly built machines in their class. The smaller KBT-11WA machine is capable of supporting 6,500kg on the table and is available ex-stock from UK agent Mills Manufacturing Technology, Leamington Spa.

The larger KBT-13A will machine components to 12,000kg.

There are four linear CNC axes with scale feedback for top precision - X for the longitudinal table travel, Y for the vertical motion of the spindle, Z for the cross traverse of the column and W for the boring spindle stroke in the same direction.

An optional rotary table (B-axis) indexes in 0.001 degree increments to provide 5-axis machining.

Working envelopes for the two models are 2000 (2500) x 1500 (1800) x 1450mm and 3000 (4000) x 2000 (2300) x 1300mm respectively, the traverses in brackets denoting optional specifications.

W-axis movements are 500mm and 700mm.

Installed weight of around 30 tonnes gives an idea of the rigidity of these machines.

Various details in the design contribute further to high precision metalcutting, such as the cast slideways for the W-axis which, unlike on many competitive borers, allow heavy duty drilling using boring spindle feed motion.

Many existing Kuraki installations make use of CNC facing heads for complex contouring of bore features.

A long-nose spindle head allows close access to the workpiece with minimum quill extension for heavy duty cutting by powerful spindle motors - 18.5kW (cont) / 25kW (30min) for the KBT-11WA and 22kW (cont) / 30kW (30min) for the KBT-13A.

Standard tool magazine capacity is 40, although 60, 90 or 120 may be specified.

50-taper tools up to 400mm long and of 25kg maximum weight are exchanged automatically.

Despite their large size, the machines are capable of fast movements and short cycle times.

The KBT-11WA offers cutting feeds to 6m/min and rapid traverse of 12m/min in X,Y,Z, 6m/min in W.

Figures are either the same or only slightly lower for the larger machine.

Large diameter, pre-tensioned ballscrews are directly connected to the axis servo motors to minimise backlash, while all slideways are hardened and ground and mating surfaces are coated with wear-resistant synthetic resin for longevity.

The pendant-mounted control panel houses a Fanuc 16M CNC system to support 5-axis interpolative machining, and also provides manual control capabilities.