Provided is a numerical controller that is capable of determining a proper timing of swarf discharge and allows an operator to change a swarf discharge method and examine appropriateness of the timing of the swarf discharge on an as needed basis, the numerical controller including a simulation unit that executes a simulation in which a workpiece is machined based on a machining program, a rendered workpiece volume calculation unit that calculates the volume of a rendered workpiece representing the shape of the workpiece rendered by the simulation, and a swarf accumulation amount prediction unit that predicts, based on the volume of the initial rendered workpiece when execution of the simulation is started and the volume of the rendered workpiece when execution of each block included in the machining program is completed, a swarf accumulation amount when the execution of the block is completed.
Please help me write a proper abstract based on the patent claims. CLAIM: 1. A numerical controller comprising a simulation unit that executes a simulation in which a workpiece is machined based on a machining program, the numerical controller comprising: a rendered workpiece volume calculation unit that calculates a volume of a rendered workpiece representing a shape of the workpiece that is rendered by the simulation; and a swarf accumulation amount prediction unit that predicts, based on the volume of an initial rendered workpiece when execution of the simulation is started and the volume of the rendered workpiece when execution of each block included in the machining program is completed that are calculated by the rendered workpiece volume calculation unit, a swarf accumulation amount when the execution of the block is completed. 2. The numerical controller according to claim 1, further comprising: a swarf discharge timing calculation unit that calculates a timing at which swarf is discharged based on the swarf accumulation amount when the execution of each block included in the machining program is completed that is predicted by the swarf accumulation amount prediction unit. 3. The numerical controller according to claim 1, further comprising: a coefficient database that stores a coefficient that is used when the swarf accumulation amount is calculated from a difference between the volume of the initial rendered workpiece when the execution of the simulation is started and the volume of the rendered workpiece when the execution of the block included in the machining program is completed, wherein the swarf accumulation amount prediction unit predicts the swarf accumulation amount by multiplying, by the coefficient, the difference between the volume of the initial rendered workpiece when the execution of the simulation is started and the volume of the rendered workpiece when the execution of the block included in the machining program is completed. 4. The numerical controller according to claim 3, wherein at least one of a workpiece material coefficient associated with a material of the workpiece and a tool type coefficient associated with a type of a tool used in the machining is stored in the coefficient database. 5. The numerical controller according to claim 1, further comprising: a display unit that displays the timing at which the swarf is discharged that is calculated by the swarf discharge timing calculation unit. 6. The numerical controller according to claim 1, wherein a display unit displays, in association with each block of the machining program, the swarf accumulation amount when execution of the block is completed. 7. The numerical controller according to claim 1, further comprising: a swarf discharge command insertion unit that inserts a command code for swarf discharge into the machining program based on the timing at which the swarf is discharged that is calculated by the swarf discharge timing calculation unit.