A machining time prediction system divides a machining program to be executed by a machine tool into a plurality of sections, transfers the divided machining programs to arithmetic unit to calculate machining times and integrates the calculated machining times. Thus, when hardware resources of an arithmetic processing apparatus for calculating a machining time are lacking, it is possible to perform necessary calculations in cooperation with the other management apparatus or machine tool or the like, and thereby shorten a processing time.

A machining time prediction system divides a machining program to be executed by a machine tool into a plurality of sections, transfers the divided machining programs to arithmetic unit to calculate machining times and integrates the calculated machining times. Thus, when hardware resources of an arithmetic processing apparatus for calculating a machining time are lacking, it is possible to perform necessary calculations in cooperation with the other management apparatus or machine tool or the like, and thereby shorten a processing time.

A numerical controller includes a numerical control unit, a DNC operation management unit, and first and second communication units. The first and second communication units receive the same NC program from a host through corresponding communication paths. The DNC operation management unit acquires the NC program from a reception data buffer included in one of the communication units to transfer the NC program to the numerical control unit, and when a failure occurs in the communication path used by the communication unit, an acquisition destination of the NC program is switched to a reception data buffer of the other communication unit.

When a numerical controller enters a DNC operation mode, a host apparatus transmits NC data to the numerical controller. When the received NC data includes a sub program call, a repeat instruction or a branch instruction, the numerical controller stores search information that is required for executing these instructions. When the numerical controller includes search information, the host apparatus transmits, to the numerical controller, NC data corresponding to the search information. The numerical controller analyzes the received NC data and executes operation.