A tool load displaying method includes displaying tools specified by a machining program and selectively displaying at least one of machining processes which are specified by the machining program and each of which is performed by using each of the tools. Load information and values of machining parameters in a selected machining process selected among the at least one of machining processes displayed are displayed. A selected tool is selected among the tools. A first selection window showing at least one replacement tool replaceable with the selected tool is displayed so as to select a selected replacement tool among the at least one replacement tool. A second selection window showing at least one machining process performed by using the selected tool is displayed so as to select among the at least one machining process, at least one selected replacement-tool machining process to be performed by using the selected replacement tool.

A tool abnormality detection system corrects a monitoring range for a load on a tool in an M.sup.th cycle by using load data of at least one of 1.sup.st to (M1).sup.th cycles (where M is an integer of 2 or more), wherein processing work on a single workpiece corresponds to a single cycle, and the load data is data about the load on the tool in the cycle.

A round hole machining method and a round-hole machining device in which machining can be accurately performed regardless of the wear of an edge tool. A non-round hole machining device includes: a machining load data acquisition section for obtaining machining load data corresponding to a machining load acting on the cutting edge of a cutting tool when boring a bore in a cylinder block; a machined shape prediction section for predicting a machined shape of the workpiece by utilizing the obtained machining load data and elastic deformation amounts at respective positions on the workpiece; and a motor control section for machining the workpiece so as to form an inverted shape, that is, a shape formed by inverting the predicted machined shape with respect to a target shape.

A robot controller, by which an operator can visually or intuitively understand the direction and/or magnitude of an actual force applied to an arbitrary portion of a workpiece. The controller controls a motion of a robot so that one of a work tool and a workpiece is moved relative to the other, and carries out a predetermined operation. The controller has a force detecting part which detects a force acting between the work tool and the workpiece; and a displaying part which displays a simulated image or video of the robot. The displaying part displays a trajectory of working points on the workpiece, and the force detecting part detects the force applied to each working point when the work tool passes through the working point. The displaying part displays the detected force as a line segment, etc., extending from the working point or a point near the working point.