A machine learning apparatus learns a setting value in a machining program of a machine tool configured to machine an impeller. The machine learning apparatus includes a state observation unit configured to acquire the thermal displacement amount during a period of machining a workpiece, as a state variable, and a determination data acquisition unit configured to receive the imbalance amount in the impeller after machining as determination data. The machine learning apparatus includes a learning unit configured to learn the setting value in the machining program on the basis of output from the state observation unit and output from the determination data acquisition unit.
Please help me write a proper abstract based on the patent claims. CLAIM: 1. A machine learning apparatus configured to learn a setting value in a machining program of a machine tool configured to machine an impeller, the machine learning apparatus comprising: a state observation unit configured to acquire a thermal displacement amount during a period of machining a workpiece, as a state variable; a determination data acquisition unit configured to receive an imbalance amount in the impeller after machining as determination data; and a learning unit configured to learn the setting value in the machining program on the basis of output from the state observation unit and output from the determination data acquisition unit. 2. The machine learning apparatus according to claim 1, wherein the setting value in the machining program includes at least one of a position of an origin of a workpiece coordinate system and an intersection offset vector for two rotary axes. 3. The machine learning apparatus according to claim 1, wherein the state observation unit acquires an ambient temperature in a vicinity of the machine tool as the state variable. 4. The machine learning apparatus according to claim 1, wherein: a temperature detector is attached to a predetermined member of the machine tool; and the state observation unit acquires the thermal displacement amount estimated on the basis of output from the temperature detector. 5. The machine learning apparatus according to claim 1, the machine learning apparatus being connected with a plurality of machine tools, wherein: the learning unit is configured to learn the setting value in the machining program for each machine tool and shares information acquired through learning the machining programs of the plurality of machine tools. 6. A machining system comprising: the machine learning apparatus according to claim 1; a machine tool configured to machine a workpiece so as to produce an impeller; and an imbalance measuring machine configured to measure the imbalance amount in the impeller.