Tool-checking device in a workpiece processing machine

A device for checking a tool to be used in a numerically controlled machine tool, with

• a measuring device, having
• a light emitter designed to emit a measuring beam for contactless scanning of the tool by means of the measuring beam, and
• a light beam receiver designed to receive the measuring beam and to emit a shadow signal representative of a degree of shading of the measuring beam by the tool;
• an evaluation unit programmed and designed to
• receive and process the shadow signal from the light beam receiver;
• receive and process a signal from a controller of the machine tool about the rotation of the tool and movement of the rotating tool relative to the measuring beam;
• initiation of a message to the controller of the machine tool that the tool is reaching a starting position in which the or each cutting edge of the tool dips so far into the measuring beam, and in doing so shades this to such an extent, that a lower and an upper switching threshold of a measurement range of the evaluation unit is reached or undershot;
• initiation of a movement of the tool rotating at a predetermined speed at an at least approximately constant feed rate, starting out from this starting position, out of the measuring beam, or from a starting position above the upper switching threshold into the measuring beam until the shortest cutting edge falls below the lower threshold, and
• registering the shadow signal produced by the or each cutting edge of the tool on shading of the measuring beam in relation to its local and temporal occurrence during the movement of the rotating tool out of the measuring beam;
• determination of the event that, at least for one cutting edge of the tool, the shadow signal does not fall below the lower switching threshold of the measurement range and does not exceed the upper switching threshold of the measurement range, so that a maximum shadow signal produced during the movement of the rotating tool out of the measuring beam is located above the lower and below the upper switching threshold of the measurement range;
• wherein
• the feed rate in proportion to the measurement range of the evaluation unit, which range is dependent on a beam transverse measurement of the measuring beam, is determined such that, during at least one revolution of the rotating tool, at least one of the cutting edges produces at different positions a respective maximum shadow signal located above the lower and below the upper switching threshold of the measurement range;
• with each revolution of the rotating tool the maximum shadow signals ascertained of each cutting edge
• differ by an at least approximately constant offset amount according to the delay and spatial change of the tool, and
• are superimposed to form a resultant representative shadow signal for this cutting edge.