In an unusual move by Japanese machine tool builder, Brother, which specialises in producing high-speed, 30-taper-spindle machining centres, a high torque, 10,000 rpm spindle option has been introduced for two of the models in its range. One is the TC-S2D while the other is the recently launched TC-R2B, the first of which has just been installed in the UK at the Sheffield factory of Ancon Building Products. Both machines have the suffix ‘N’ if the high torque motor is fitted.
Tim Whitehouse, managing director of UK sales and service agent, Whitehouse Machine Tools, commented, “Normally one would expect high-torque spindle motors on 40- and 50-taper machines, but Brother has broken the mould by bringing heavy machining capability within reach of manufacturers using these lighter duty machines.
“At the low end of the speed range, for example, it is now possible to drill a 32 mm diameter hole and tap to M27 in 150 HB carbon steel, up from 25 mm and M16 for the standard 10,000 rpm spindle motor. In aluminium, similar increases take the figures to 40 mm and M39.
“At higher speeds, a 16 mm diameter end mill can take a 15 mm wide by 8 mm deep side cut in carbon steel, while a 125 mm diameter face mill will remove 1,700 cc/min from an aluminium billet.”
Higher torque is provided by the brushless interior magnet motor at the mid to high speed range as well as at the low end, where it is 2.7 times higher at 92 Nm between zero to 2,200 rpm. Maximum power output is also raised from 18.4 to 26.2 kW.
Owing to the increased torque at higher speeds, an extra advantage is that the spindle can be decelerated faster from top speed to zero, ie in 0.15 instead of 0.2 of a second, and accelerated similarly quickly. The servomotor-driven turret’s ATC (automatic tool change) time is therefore shortened from 1.6 to 1.5 seconds. Just over six per cent reduction may not sound much, but it can make a considerable difference when producing batches of thousands of components whose cutting cycles involve frequent tool changes.
Brother has used regenerative power technology on the high torque motor to utilize braking power and improve energy efficiency. Power consumption has been reduced by between 20 and 30 per cent, says the manufacturer. There is the option of face-and-taper contact tooling for all spindles, including the standard 10,000 rpm type and the high-speed, 16,000 rpm version.