A new type of machining center is designed for realizing higher productivity. The specification of the machining center to be designed is determined by a cycle time analysis. The simulator used for this cycle time analysis is programmed by the authors and implemented on a microcomputer. The simulator analyses an NC program for machining a machine part, and calculates the time required for each machining operation, such as positioning, cutting, and tool changing, then sums up each operation time to output the cycle time for machining the part. The result of the simulation indicates that the cycle time can be decreased by increasing the cutting speed, therefore by increasing the rotational speed and output power of the main spindle. Higher feed rate and acceleration of the feed drives are effective for improving the productivity only when the cutting speed is increased. Based on the result of simulation, the specification of the machining center for higher productivity is determined as follows; the maximum speed of the main spindle is 30000 rpm, the maximum motor output power is 54 kW, and the maximum feed rate and acceleration of the feed drives are 60 m/min and 10m/s2, respectively. According to the specification, a machining center for higher productivity is made, and the cycle time for machining a machine part is measured. The cycle time measurement indicates that the productivity of this improved machining center is much higher than that of a conventional machining center.
