Device and method for machining components with indeterminate dimensions, such as cast components, on a machine tool

Abstract

Method for machining cast components (WP) on a program-controlled machine tool (100), wherein the machine tool (100) comprises a work spindle (15) rotatably mounted about a spindle axis with a tool interface and wherein a contact detection means is provided for detecting a contact between a tool (WZ) received in the tool interface and a clamped cast component (WP) wherein the process is a machining manufacturing process for machining with geometrically defined cutting edges, comprising the following steps: - Pre-positioning (S2) of the tool (WZ) at a distance from the clamped cast component (WP); - Automatic approach (S3A) by moving the rotating tool (WZ) to the cast component (WP); - Detection (S5) of a contact point or contact area between the rotating tool (WZ) and the cast component (WP) by detecting at least one detection parameter (EF); - Start (S8) of the machining of the cast component (WP) according to a machining program, wherein the determined contact point or contact area determines at least one machining parameter of the machining program.

Description

[0001] The present invention relates to a method and a control device for use on a numerically controlled machine tool for machining (in the technical field of machining processes for machining with a geometrically defined cutting edge) components with indeterminate dimensions, in particular cast components. In particular, an efficient machining cycle for cast components is proposed, which includes a particularly advantageous start-up cycle.

[0002] For machining cast components (using a tool with a geometrically defined cutting edge), the state of the art typically proposes probing the clamped cast component using a probe to determine, for example, the precise positioning and dimensions of the cast component. Based on the result of this first process step, the actual machining of the cast component can be performed in the subsequent process step.

[0003] Cast components have different machining allowances depending on the quality grade and the forming process. These allowances can lead to excessive cutting dimensions during machining, which can overload the tool and the machine tool. Conversely, excessive chip removal can result in a poorly finished surface and an excessively long machining time. Therefore, when machining cast components using a tool with a geometrically defined cutting edge, the state of the art usually proposes a separate probing process using a probe, as shown, for example, in DE 10 2016 008 284 A1.

[0004] From DE 10 2007 063 200 A1 a honing process for fine machining is known in which the time of contact between tool and component is determined on the basis of a recorded structure-borne sound of the tool.

[0005] From DE 602 10 771 T2 a method is known for determining the amount of material removed from a grinding wheel in order to be able to indicate a state of wear.

[0006] Generic machine tools or CNC machine tools typically have a control device, such as a machine control system, for use on a numerically controlled machine tool. Drives and spindle drives, as well as axis drives of linear, rotary, and swivel drives of the machine tool, can be controlled accordingly via the control device, in particular based on control data or based on control data comprising an NC program. A machine tool and a corresponding control device are known, for example, from DE 10 2019 208 624 A1.

[0007] Based on the above prior art, it is an object of the present invention to provide a device and a method for machining (in particular with a geometrically defined cutting edge) components with undefined dimensions, in particular cast components, on a machine tool, in order to enable an efficient and precise machining process for the cast component. Furthermore, an object can be seen in enabling the precise and efficient machining of a cast component with partially unknown dimensions and, for example, an undefined fixture in the clamping device, without the need for additional probes.

[0008] To solve the aforementioned problems, the features of the independent claims are proposed. Further improvements are found in the dependent claims.

[0009] According to the present invention, a method for machining, with a geometrically defined cutting edge, components with indeterminate dimensions, which are cast components, on a program-controlled machine tool is proposed. The machine tool can comprise a work spindle rotatably mounted about a spindle axis and having a tool interface. A contact detection means can be provided, which is, for example, integrated directly into the machine tool, for detecting contact between a tool received in the tool interface and the clamped component, in particular a cast component. Machining with a geometrically defined cutting edge refers to methods in which the number and geometry of the cutting edges are known.For example, according to DIN 8589 Part 1, machining with geometrically defined cutting edges is a process in which a tool is used whose number of cutting edges, geometry of the cutting wedges and position of the cutting edges relative to the workpiece are precisely determined.

[0010] The method advantageously comprises the following steps, particularly preferably in the following order: Pre-positioning the tool, which is preferably a tool with a defined cutting edge, at a distance from the clamped component, in particular a cast component. It is particularly preferred to position the tool in this first step such that it is arranged in a safety zone of the work environment at a sufficient distance from the work area in which the component can be clamped.

[0011] In a further step, the tool can be automatically approached toward the component. This is preferably achieved by directly moving the tool, which is activated and therefore rotating, toward the component along a predefined approach direction. The approach direction for the automatic approach step can preferably be selected before machining begins, so that the initial contact between the tool and the component occurs in a predeterminable area of ​​the component. In a further step, which is particularly preferably carried out synchronously with the automatic approach step, possible contact points or contact areas between the rotating tool and the component are detected, particularly preferably by detecting at least one detection parameter.

[0012] Once the contact point has been identified, machining of the component can preferably begin immediately. By determining the contact point or contact area and evaluating the spatial position of the contact point or contact area in the machine coordinate system, the position or extent of the component can be integrated into the machining program based on the actual determination, allowing the machining program to be adapted, taking into account the actual position of the clamped component. This approach makes it possible to always provide a customized machining program for machining on a machine tool, even for cast components of the same type that have different dimensions due to the casting process.

[0013] The detected contact point or contact area can therefore determine at least one machining parameter of the program-controlled machine tool's machining program. For example, the detected contact point can automatically determine the cutting size for determining the chip removal during machining of the component. The method according to the invention determines contact directly during the machining process of the component, so that a predetermined machining program can be adapted specifically to the currently clamped component without having to use an external probe. The tool for determining the contact point can thus be used as a machining tool for machining in accordance with the preselected machining program immediately after the contact point has been determined. The determination of the contact point or contact area can also be further improved if the coolant supply is activated at the same time as the tool is automatically moved directly to the component. It is particularly advantageous if the cycle for automatic contact point determination is integrated directly into the NC program of the machine control system in order to enable the workpiece to be detected and machined with the greatest possible time efficiency.

[0014] In summary, the present invention therefore proposes an optimized method and an optimized device for machining components with an indeterminate or not precisely defined geometry, such as cast components, which allows a probe-free machining of the cast component and at the same time allows a high accuracy and efficiency of the machining.

[0015] According to the invention, the proposed method and the proposed device can be used particularly preferably for components which, due to a forming process, have a geometry and surface with reduced accuracy and are therefore to be regarded as a workpiece that is not geometrically precisely defined. The surface tolerances and / or linear dimensional tolerances can therefore, for example, be in a range of 1.5 mm or worse (i.e. reduced accuracy). Particularly preferably, the tolerances of the casting can be in a range of casting tolerance grade CT 7 (linear dimension casting tolerance according to EN ISO 8062-3 [2008-09]) or worse. For a raw casting with a nominal size of over 40 mm up to and including 63 mm, the linear dimensional casting tolerance, with a casting tolerance grade of CT 7, is 1 mm.

[0016] In particular, a cast component within the meaning of the present disclosure can be a cast blank (and, in a particular embodiment, an unmachined cast blank). Typically, a cast blank is produced using a primary forming process—for example, the gravity die casting process. Due to the manufacturing process, a cast blank produced in this way initially exhibits comparatively coarse dimensional and surface tolerances. The cast blank can be brought into its final shape through subsequent separating or machining, such as punching, milling, or drilling.

[0017] Cast components within the meaning of the present disclosure can preferably also be components which were produced by a rapid prototyping process and have a geometry and surface with a reduced accuracy.

[0018] The method can preferably determine detection parameters simultaneously as the rotating tool moves toward the cast component, using the contact detection means of the machine tool. Particularly preferably, the detection parameters are determined continuously as the rotating tool approaches the cast component. Contact detection means can, in particular, be integrated sensors of the machine tool, such as structure-borne sound sensors, as well as detection means for the motor currents, the linear axes, and / or the spindle of the machine tool.

[0019] The method can also include the configuration that determines contact with the cast component by evaluating the detection parameter and / or the temporal progression of the detection parameter. Preferably, the detection parameter is a parameter that can be determined in any case on the machine tool, such as a motor current of the linear axes or the spindle current of the work spindle. By comparing the recorded detection parameter in the specific machining operation with a predefined limit value, which depends on the machining type of the machine tool, the component material, and the tool, it can be determined that contact with the cast component has been achieved.An even more precise detection can be determined via the temporal course of the continuously recorded detection parameter during the automatic approach of the rotating tool to the cast component, since the achievement of predetermined, previously statistically determined deviation values ​​over time allows conclusions to be drawn about a possibly imminent or currently occurring contact of the tool with the cast component.

[0020] The method can comprise a detection parameter that includes at least one of the following variables: the spindle current of the work spindle, the motor current of the linear axes of the machine tool, the travel or force of the work spindle detected via corresponding sensors, or a detected structure-borne sound, in particular of the work spindle and / or the clamped tool. The detection parameter can therefore be a scalar or, particularly preferably, a vector and include one or more of the aforementioned variables. Particularly advantageously, the detection parameter includes at least two of the aforementioned variables, thereby allowing the contact point and / or contact area to be determined even more precisely and even faster.

[0021] In the step of detecting a contact point or contact area, the tool can be switched off as soon as the contact point or contact area has been detected in order to minimize the penetration depth of the tool during contact point or contact area determination. This direct switch-off makes it possible, since the detection is preferably integrated directly into the machine control, to effect a very rapid switch-off so that the penetration depth of the tool is ≤ 0.05 mm or 0.1 mm. In a particularly advantageous development, instead of switching off the tool, the contour of the cast component to be machined takes place directly, so that the machining can be carried out according to the machining contour on the cast component.

[0022] Preferably, the method can comprise a machining program for machining the cast component. The machining program can initially comprise a preliminary machining contour of the workpiece, wherein the machining contour corresponds to the desired final shape of the finished, machined cast component. Since the cast component has different oversizes due to the manufacturing process in the casting process, the desired machining contour is defined in the coordinate system of the machine tool based on the determined contact point or contact area, so that an adapted machining contour can be provided that enables optimal machining of the cast component.In other words, a predefined machining contour used to control the machine tool is adjusted according to the actually determined contact points of the cast component, enabling precise machining of the cast component and allowing the actual position of the cast component in the machine coordinate system to be precisely determined and used as the basis for precise machining. Accordingly, the actual dimensions of the cast component to be machined can also be determined via one or more contact points, eliminating the need for a separate probe.The machining program can therefore include a preliminary machining contour of the cast component according to the desired final shape and the spatial position and / or the course of the preliminary machining contour can be corrected by the determined contact point or determined contact area to an adapted machining contour, which is used as the basis for the actual machining in order to achieve high-precision machining results.

[0023] Contact between the rotating tool and the cast component can be detected if the absolute and / or relative value of the detection parameter continuously exceeds a predetermined threshold, preferably for longer than a specified period of time. Since it is particularly important to avoid false detections, it has been found that determining the absolute or relative value of the detection parameter within a specified period of time using a predetermined threshold can be extremely effective for reliable contact detection.

[0024] The detection parameter can be detected at predetermined times during the movement of the rotating tool toward the cast component, and contact between the tool and the cast component can be detected by the absolute value and / or the temporal change of the detection parameter. To reduce the required storage and computing power, it is advantageous to define predetermined times at which the detection parameter is detected during the movement of the rotating tool toward the cast component. At these predetermined times, the absolute value or the temporal change of the detection parameter is determined to determine contact.

[0025] Preferably, the method can be configured such that the tool plunges into the cast component outside or inside the preliminary machining contour to reach the contact point or contact area. After reaching the contact point or contact area, the tool directly approaches the adjusted machining contour, which is determined based on the contact point or area just determined. Machining according to the adjusted machining contour can thus be started directly without any further intermediate steps. Particularly preferably, the aforementioned method steps are carried out automatically to enable particularly effective machining of the cast component.

[0026] The process can be an automatic approach cycle (AA cycle), which enables probe-independent machining of the cast component by determining the contact point or contact area. Such an automatic approach cycle, which does not require a probe, is particularly efficient while still ensuring high accuracy of the machined workpiece.

[0027] The tool's infeed depth for machining the cast component can be determined based on the determined contact point or contact area. This particularly advantageous approach allows the optimal tool infeed depth to be selected for the particular cast component being clamped, thus avoiding excessive or insufficient chip removal. This enables efficient and precise machining of the cast component.

[0028] Based on at least one determined contact point, preferably three determined contact points and / or contact areas, the machining allowance of the cast component can be determined, and the machining parameters of the machining program can be defined based on the allowance. This design allows the machining program to be adjusted directly during the probing phase of the already initiated machining cycle in order to achieve optimal machining of the cast component.

[0029] Preferably, the method can be designed such that the cast component is held in an indefinite manner in a clamping device for machining by the machine tool. An indefinite hold in the clamping device is, for example, a clamping with a tolerance ≥ 1 mm. The clamping device can therefore be designed, for example, without stop means, in order to easily enable, in particular, multi-sided machining of the cast component. Such a stop-free clamping device can hold the cast component to be machined in an indefinite manner and make it available for machining by the machine tool. This can achieve time- and cost-saving as well as stable clamping of the cast component. The determined contact point or contact area can determine at least one machining parameter of the machining program during machining according to a machining contour, specifically during machining of the indefinitely clamped cast component.The present invention avoids the need for a measuring probe despite using a clamping device with an undefined clamped cast component, since the contact point can be determined directly with the clamped tool. Particularly preferably, the tool used to determine the contact point is the same tool used for the subsequent machining. By adapting the machining contour, a desired machining contour can be achieved on the cast component, despite the undefined clamping of the workpiece.

[0030] Advantageously, after the contact has been detected, a contact point or contact area can determine the positioning of the clamped cast component.

[0031] Another advantage is that the same tool can be used in the step of detecting the contact point or contact area as in the step of machining the workpiece according to the adapted machining program. Therefore, the tool does not need to be changed.

[0032] Advantageously, a machine tool for machining cast components, with a geometrically defined cutting edge, is proposed here. The machine tool can have a controller configured to perform machining of the clamped cast component according to a machining program and a machining contour defined therein. The detection means can comprise a sensor for detecting the motor current of the work spindle and detect at least the motor current of the work spindle as a detection parameter. The detection means can additionally or alternatively comprise a force measuring device for detecting machining forces and / or moments between the workpiece and the cast component. Alternatively or additionally, the detection means can comprise a sensor for detecting the current consumption of the drives of the linear axes and / or the work spindle.

[0033] The machine tool can advantageously have strain gauges, in particular semiconductor strain gauges, for force detection on the spindle and / or on the carriage of the machine tool.

[0034] Further advantageously, the tool can be a turning tool or milling tool and / or after contact detection, the control can be configured such that a direct shutdown of the tool is effected, so that the penetration depth is less than 0.1 mm, preferably less than 0.05 mm.

[0035] The structure-borne sound sensor can preferably be arranged on an outer side of the spindle device. In particular, the structure-borne sound sensor is arranged such that none of the spindle bearings are arranged in a structure-borne sound wave propagation direction in the spindle device from the tool receiving section towards the structure-borne sound sensor. Particularly preferably, a second structure-borne sound sensor is proposed, which detects the structure-borne sound waves in addition to the first structure-borne sound sensor of the spindle device, wherein the signals from the sensors can be compared to further increase accuracy. In a particularly advantageous embodiment, the present machine tool comprises a spindle device according to WO 2016 / 124609 A1, which is hereby incorporated by reference.

[0036] According to further aspects of the present invention, a computer program product is preferably proposed, comprising instructions which, when the program is executed by a computer connected to a numerically controlled machine tool or a control device of the numerically controlled machine tool, in particular according to one of the above aspects or embodiments, cause the computer or device to carry out the method according to the above aspects.

[0037] In a particularly advantageous embodiment of the present invention, the method for machining cast components comprises, in the step of automatically approaching the cast component by moving the rotating tool to the cast component, simultaneously activating the coolant supply, so that a coolant supply is ensured as soon as the first contact point is reached, and at the same time, the effect of the coolant supply on the cast component is taken into account when determining the contact point. This allows the accuracy of the contact point determination to be further improved.

[0038] Particularly preferably, after pre-positioning the tool, the automatic movement of the tool directly to the cast component begins in parallel, as does the start of detection or recording of the detection parameters for detecting the contact point. Advantageously, a tool stop and deactivation of the coolant supply can occur after the contact point detection.

[0039] Further advantageously, the detection of the contact point or contact area can include the detection of the coordinates of the contact point or contact area in the machine coordinate system, wherein these coordinates are determined by an estimated penetration depth, which is determined, for example, as a function of the tool rotation speed and the feed, in particular the probing feed, in order to determine the position of the contact point even more precisely. In other words, not only is the contact point determined via the course of the detection parameter, but rather, for an even more precise determination of the position and / or dimensions of the cast component, a back calculation is also performed to determine the actual position and dimensions of the cast component, taking into account the penetration depth resulting from the contact point determination.

[0040] The recorded coordinates of the cast component can be provided directly to the machine control system, allowing an optimal infeed depth to be determined for the selected machining cycle. This determination is particularly preferably performed parallel to the start of machining of the cast component by the tool according to the preselected machining program. This parallel approach has proven particularly efficient, allowing a powerful machine control system to optimize the machining program of the cast component during machining. In addition, automatic processing of the first contact point, the determined contact point, in the NC program can be achieved.

[0041] Advantageously, the shutdown reaction, which is required, for example, for the tool stop, can be determined automatically, depending on the material of the cast component to be machined as well as the machine dynamics of the machine tool and the tool used.

[0042] Particularly advantageously, two contact points are determined in different approach directions, with a separate cut-off being defined for each approach direction after reaching a predetermined penetration depth. Advantageously, the tool is a rotary tool, with a cut-off occurring after 0.05 mm in the Y direction and after 0.01 mm in the Z direction. Particularly preferably, this cut-off is determined dynamically, depending on the set or current tool speed and the set or current feed rate.

[0043] Particularly good results were achieved for cast components which are approached by automatic approach using a rotating tool in such a way that the contact point is on an unmachined surface of the cast component.

[0044] The above-mentioned and further advantageous aspects of the present invention are described below with reference to the accompanying figures. Fig. 1 shows a machine tool with a clamped cast component in a schematic representation; Fig. 2 shows an exemplary representation of a work spindle of the program-controlled machine tool; Fig. 3 shows a flow chart of the method for machining cast components on the program-controlled machine tool; Fig. Figure 4 shows another flowchart for the detection of contact points. Fig. 5 shows the call of the cycle in the sequence of program steps.

[0045] Fig. 1 shows a schematic exemplary representation of a numerically controlled machine tool 100, exemplified as a milling machine. However, the present invention is not limited to milling machines, but can also be applied to other machine tool types, e.g., cutting machine tools designed for machining workpieces, e.g., by drilling, milling, or turning cast components, such as milling machines, universal milling machines, lathes, turning centers, automatic lathes, milling / turning machines, machining centers, gear cutting machines, etc. A cast component is understood to mean a component that was produced using a casting process.

[0046] The machine tool 100 comprises, for example, a machine frame with a machine bed 101 and a machine stand 102. For example, a movable machine slide 105 is arranged on the machine bed 101 and is mounted, for example, for horizontal movement in a Z direction on the machine bed 101 (Z axis). A cast component WP is clamped on the machine slide 105, which can comprise a workpiece table, for example. For this purpose, clamping devices can also be provided on the machine slide 105 or tool table. In addition, in further exemplary embodiments, the machine slide 105 can comprise a rotary table that can be rotated or pivoted about a vertical and / or further horizontal axis (optional rotary or circular and / or pivoting axis). Furthermore (or alternatively), the machine slide 105 can be moved by means of a Y axis in a horizontal Y direction (potentially perpendicular to the plane of the drawing).

[0047] The machine stand 102 supports, for example, a spindle carriage 103 which is movable vertically in an X-direction on the machine stand 102 and on which a work spindle 104, for example carrying a tool, is held. The work spindle 104 is configured to drive the tool WZ (e.g., a drilling and / or milling tool) mounted on the work spindle 104 in rotation about the spindle axis SA. For example, the spindle carriage 103 is movable vertically in the X-direction by means of an X-axis. Furthermore (or alternatively), the spindle carriage 103 can be moved by means of a Y-axis in a horizontal Y-direction (potentially perpendicular to the plane of the drawing). In addition, in further exemplary embodiments, the spindle carriage 103 can comprise a rotary and / or pivot axis in order to rotate or pivot the spindle 104 (optional rotary or rotary and / or pivot axis).The machine tool 100 further comprises, for example, a control device 200, which, for example, comprises a screen 210 and an input unit 220 for operating the machine tool 100. The input unit 220 can, for example, comprise means for user input or for receiving user commands or command actions of the operator.

[0048] The control device 200 can be used to control the operation of the machine tool or machine processes on the machine tool and also to monitor an operating state of the machine tool 100 or the machining process during machining.

[0049] The machine tool 100 comprises, for example, a plurality of actuators (e.g. spindle drive, axis drives, etc.) of the machine tool 100 that can be controlled by the control device 200 and optionally a plurality of sensors for outputting sensor signals relating to a machine state of the machine tool 100 to the control device 200.

[0050] The actuators can include, for example, drives of controllable linear and rotary axes (swivel and / or rotary axes) for a controlled relative movement between tool and workpiece, and also drives of tool-carrying work spindles (e.g. on milling machines) or workpiece-carrying work spindles (e.g. on lathes).

[0051] Furthermore, the actuators can include electronically, hydraulically, and / or pneumatically controlled valves, pumps, or other supply devices for internal or external coolant or compressed air supplies. Conveyors, pallet changers, workpiece changers, tool magazines, and other machine tool accessories can also be controlled via drives or circuits or corresponding actuators.

[0052] The optional sensors can be sensors that can be assigned to the respective assemblies or components of the machine tool, e.g., the axes, the drives, axle bearings, the spindles, spindle bearings, a tool magazine, a tool changer, a pallet or workpiece changer, an internal or external coolant supply device, a chip conveyor, and / or a hydraulic and / or pneumatic control system. A variety of different sensors can be provided for the individual assemblies, such as position sensors, current and / or voltage sensors, temperature sensors, force sensors, acceleration sensors, vibration sensors, bearing diagnostic sensors, or displacement sensors.

[0053] Fig. 2 shows an exemplary schematic perspective exploded view of a work spindle for a program-controlled machine tool according to an embodiment of the present invention;

[0054] On such work spindles, tools with tool interfaces, such as tool tapers, especially Morse tapers, steep tapers, or hollow shank tapers, can typically be mounted on the work spindle's holding fixtures or tool holders, and then driven by the work spindle. These can be a wide variety of drilling or milling tools or other tools, each of which is clamped or fixed to the typically standardized tool interface or tool taper.

[0055] The machining unit / spindle device according to Fig. 2 comprises, for example, a spindle housing 1, which can be attached to or assembled with another component of the machine tool, in particular, for example, with a spindle head carrier or a swivel head of the machine tool, if necessary with the aid of an annular flange 2, which has, for example, a plurality of axial bores 3 for attachment to or assembly with other components of the machine tool. The work spindle 15 is rotatably mounted inside the housing 1. On the front of the annular flange 2, a frustoconical housing part 4 of the machining unit / spindle device is attached, for example, in the peripheral wall of which one (or more) outwardly open longitudinal grooves 5 are machined. The longitudinal groove 5 continues, for example, in a receiving groove 6, which is formed, for example, in the annular flange 2. The longitudinal groove 5 and its continuation, ie, for examplethe receiving groove 6, form, for example, a receiving channel for a (not shown) energy and / or measurement data cable, which can be laid in this receiving channel 5, 6 and then covered by a shaped sheet 7 detachably fastened to the housing part 4.

[0056] In Fig. 2, a first ring element 10 is shown in front of the front end of the housing part 4, which can be releasably fastened to the front side of the housing part 4, for example, by a plurality of fastening elements 11 (e.g. screw bolts). The first ring element 10 has, for example, a profiled cross-section and is supported, for example, with its Fig. 2 right end face (ie in particular with the side facing the spindle) on the left annular end face of the housing part 4 or is attached or detachably fastened thereto.

[0057] At the front end of the work spindle, a second ring element 16 is detachably fastened to the first ring element 10 by a plurality of fastening means (e.g. stud bolts), wherein the second ring element 16 rotates together with the work spindle and can therefore represent a rotor.

[0058] The second ring element 16 has, for example, a cylindrical inner circumferential surface and, for example, a stepped cross-section. The second ring element 16 is covered, for example, by an annular cover element 17, which is releasably attached to the, for example, flat end surface of the spindle by means of fastening means (e.g., stud bolts 18) and closes off the front of the work spindle, leaving the tool holder free for clamping a tool shank.

[0059] For example, receiver and / or transmission means can be accommodated in the first ring element 10, which can serve for the contactless transmission of measurement data, sensor signals and / or energy signals. Furthermore, a cable duct section 12 for the electrical connection to the sensor system (e.g. connection of the energy and / or measurement cable to the receiver or transmission means) is provided on the first ring element 10, which cable duct section 12 lies opposite the cable duct of the longitudinal groove 5 and can protrude into this cable duct when assembled. One or more sensors can be accommodated in the second ring element 10. This can include sensors, e.g. vibration sensors, with which operational deformations of the spindle or spindle head in the axial and also circumferential directions can be detected.Various sensor types, such as pressure-, voltage- or force-sensitive sensors, are suitable as measuring sensors to detect, for example, spindle alignment errors and / or shape changes.

[0060] The sensor system may include an evaluation unit electronically linked to the various sensors, which evaluates and stores the recorded data and can be microprocessor-controlled. This sensor system can also be used to record and store wear values ​​of the cutting tools and any damage to machine components caused by impact collisions, and then incorporate these values ​​into the machine control system. Furthermore, vibration sensors can be used to perform imbalance measurements or detect bearing damage in the work spindle based on an evaluation of the measurement signals.

[0061] A cable (measurement and / or power cable) is routed through the cable duct 5 of the housing part 4 into the stationary outer ring (first ring element 10), which is firmly connected to the spindle housing part 4. This outer ring (first ring element 10) may contain connections for the power and measurement data cable. This power or measurement cable may also be connected to a transmission element arranged in the stationary outer ring (first ring element 10), the counter element (receiver element) of which may be located in the rotor ring (second ring element 16) rotating with the spindle. According to the exemplary embodiment of the invention, the spindle device is designed to enable milling.

[0062] For machining a workpiece with a milling tool inserted or exchanged on the spindle device, the sensor system of the spindle device is designed such that the sensors or the sensor system of the spindle device comprise at least one structure-borne sound sensor which is designed to detect sound or structure-borne sound which is generated or caused during the grinding of the workpiece and which is transmitted to the elements or components of the spindle device via the tool and the tool interface.

[0063] For background purposes, it should be noted that the term “structure-borne sound” describes the propagation of structure-borne sound waves or vibrations within a solid body. This can include the propagation of longitudinal waves or vibrations (in particular waves or vibrations in the internal structure of the solid body) and / or the propagation of transverse waves or vibrations (in particular waves or vibrations on the surface of the solid body) within the solid body, usually at different propagation speeds (structure-borne sound speed). Structure-borne sound vibrations, for example, typically occur at frequencies in the ultrasonic range, and in particular at around 20 kHz to 2 MHz, and are therefore typically outside the frequency range of human hearing. In steel, for example, the propagation speed for longitudinal waves or vibrations is around 5000 m / s and for transverse waves or vibrations around 3100 m / s.

[0064] Typical measuring ranges for structure-borne sound sensors are, for example, in the range 50 to 900 kHz, or preferably in the range 100 to 400 kHz, particularly to reduce resonance effects. During the machining process, the workpiece in contact with the tool generates structure-borne sound that propagates through the workpiece and tool. Such vibrations can be detected using structure-borne sound sensors and can thus provide information about the machining process during the machining process. The structure-borne sound measurement, using diagnostic and data monitoring units of the evaluation units or the machine control system, enables instantaneous monitoring or process monitoring of the machining process and the process parameters during machining.

[0065] In this case, the machine control of the machine tool can, if necessary, have an automatic program cycle that the operator can easily start, for example by automatically approaching with larger distance steps in a first automatic cycle step until the first contact is detected on the basis of the structure-borne sound signal at the machine control, in order to then automatically carry out the actual machining process in a second automatic cycle step.

[0066] The workpiece and the tool can expediently be fed relative to one another without visual control by the operator, whereby in a first (optional) automatic cycle step in rapid traverse, ie at high travel speeds, one or more linear or rotary axes of the machine tool are automatically moved to a safety position (e.g. preset safety distance), in order to then be fed in a second automatic cycle step of the feed process by means of an automatic approach until the first contact is detected on the basis of the structure-borne sound signal at the machine control, whereupon the actual program-controlled machining process is started, e.g. either automatically or by manual start command by the operator.

[0067] Fig. Figure 3 shows an exemplary flowchart of the method for machining cast components (machining manufacturing method for machining cast components with a geometrically defined cutting edge) according to the present invention. The illustrated process is advantageously used as an automatic probing cycle, which particularly preferably leads directly to the machining of the cast component.

[0068] Particularly when machining cast components, which have comparatively high tolerance values ​​due to the manufacturing process, it is necessary to perform appropriate probing processes with probes for the machining process. In the prior art, this is usually done using specially designed probes. However, according to the present invention, this probing process is automated and a probe-free cycle is proposed. Based on the determined data, such as the coordinates of the determined contact points, the optimal cutting size for machining the cast component can be selected in the machining program for the machining process.

[0069] In a first step S1, the machining cycle can be started. One possibility is to initiate this process through manual input from the machine tool operator. Alternatively, the automatic cycle can be integrated into a series production cycle, so that it is automatically started by the machine tool control system as soon as the cast component is mounted in the machine tool's clamping fixture.

[0070] In step S2, the tool can be pre-positioned. This optional step, in particular, enables the tool to be located in a precisely defined starting position and optimally positioned for the subsequent probing and machining steps. Particularly preferably, the positioning of the tool in the pre-positioning step S2 is designed such that, after appropriate positioning, the tool is located in a workpiece-free area and, particularly preferably, outside the actual work area for machining the workpiece.

[0071] In addition to pre-positioning the tool, a step can be provided that defines an approach direction of the tool to the clamped cast component. Particularly preferably, an approach sequence can also be defined in correspondingly different approach directions. Based on the selected approach direction, an area in which the first contact with the cast component is to be expected can be determined via the tool's position detection. The machine tool is therefore controlled, preferably automatically, in such a way that the pre-positioned tool can be moved in a specific approach direction into the expected area of ​​the contact point to the cast component for the subsequent detection of the contact point. The approach direction can be automatically selected in such a way that a possibly already present machined surface of the cast component is not controlled as a contact point and / or contact area.This design prevents damage to previously machined surfaces during contact point determination, as the cast component can be clamped indefinitely in the fixture. This type of clamping allows for very fast and impact-free clamping of the cast component.

[0072] After step S2 of pre-positioning the tool, the automatic process S3A and the detection S3B preferably start in parallel. In a preferred further development, the coolant supply S3C is also automatically activated in parallel.

[0073] In the step of automatically moving the tool to the cast component S3A, the clamped tool, in particular a turning or milling tool, moves along a predetermined probing direction directly to the clamped cast component to reach a first contact point. The clamped tool is in an activated state and therefore rotates at a predetermined speed. The feed rate for this step also corresponds to a predetermined feed rate. The speed and feed rate for the probing process are preferably determined automatically based on the provided input data, such as component dimensions, component material, clamped tool, and machine tool type. Synchronously with the movement of the tool directly to the cast component, the coolant supply can be activated according to step S3C, so that coolant is applied directly to the tool.At the time of first contact with the cast component, a supply of cooling lubricant is thus advantageously ensured, which at the same time allows better detection of the contact point relevant for machining and protects the tool from wear.

[0074] In parallel to steps S3A and S3C, the detection of the acquisition parameter EF is started in step S3B. By starting the detection, the variables of the acquisition parameter to be determined, such as in particular the spindle current of the machine tool's work spindle, the motor current of the machine tool's linear axes, the path and / or force detection of the work spindle, the structure-borne noise of the work spindle and / or the tool, are continuously recorded. The acquisition parameter EF can comprise one or more of the variables and can be configured, for example, as a vector. During the automatic movement of the tool directly to the cast component S3A, the variables of the acquisition parameter EF lie within a predetermined range, which results, for example, from the rotational speed, the feed rate, and the machine dynamics.The predetermined bandwidth can be determined in advance, particularly for an air cut, so that the machine control system can automatically access factory-prepared parameter tables to determine whether one or more of the variables of the detection parameter EF are within the predetermined bandwidth range for the air cut. An air cut is understood to mean, in particular, the state in which the rotating tool is moved with feed towards the cast component, but no contact has yet occurred. The variables of the detection parameter are particularly preferably detected via integrated contact detection means of the machine tool, such as a detection means for determining the spindle current of the work spindle and the motor current of the linear axes of the machine tool and / or path / force detection means of the work spindle. Strain gauges can also advantageously be provided on the spindle head for determining the detection parameter.

[0075] As soon as the rotating tool comes into contact with the clamped cast component, the values ​​of the detection parameters change. For example, when the rotating tool comes into contact with the cast component, a sharp increase in cutting forces can be detected, which can be measured, for example, via the spindle current of the work spindle or the motor current of the linear axes. This increase causes the measured values ​​to leave the predetermined band range and preferably reach a predetermined limit, allowing the machine control system to detect that contact with the cast component has occurred.

[0076] Advantageously, in order to improve the detection precision, the detection parameter is preferably detected continuously, whereby contact with the cast component is detected as soon as the temporal course of the detection parameter lies continuously outside the predetermined band range for a certain period of time.

[0077] The structure-borne noise of the work spindle and / or the tool can also be used as the detection parameter EF. When the tool comes into contact with the clamped cast component, a significant change in the structure-borne noise of the work spindle and / or the tool can be detected, allowing the machine control system to conclude that contact with the cast component has occurred. As described in Fig. As shown in Figure 3, during the detection of the detection parameter EF, a multiple determination of whether a contact point has been detected is performed according to step S5. As long as no contact point has been detected, steps S3A, S3B, S3C, and S4 are performed in parallel and continuously.

[0078] As soon as a contact point is detected (in step S5), a tool stop can be initiated immediately. The tool stop can, in particular, be a stop in the rotation of the tool and a stop in the feed, whereby a stop in the coolant supply can also be included. By positioning the tool at the moment the contact point is detected, the coordinates of the contact point can be determined in the machine coordinate system. In particular, the machine control system detects the current position of the clamped tool (or the cutting edge of the tool), so that when a contact point is detected, the coordinates of the contact point on the component can be determined. The coordinates are preferably available in the machine coordinate system.

[0079] The detection accuracy can be significantly increased if the detection parameter EF includes several of the aforementioned variables. For example, diametrically opposed structure-borne sound sensors of the work spindle and / or tool can determine the direction of the structure-borne sound, allowing both the coordinates of the contact point and a direction, particularly a direction perpendicular to the surface of the cast component, to be determined. Since the two structure-borne sound sensors detect differently arranged body vibrations due to their diametrically opposed arrangement, a contact surface or contact area with the cast component can be determined using a corresponding simulation model of the tool and / or machine tool.Similarly, the motor current of the linear axes, when measured across different linear axes, can be used to draw conclusions not only about the contact point but also about the surface configuration of the cast component in the area of ​​the contact point. The recording of the contact point coordinates in the NC program is described in . Fig. 3 in step S8.

[0080] The acquired coordinates can be used in a subsequent (automatic) step S7B to determine the optimal infeed depth for workpiece machining. Furthermore, the coordinates can advantageously also be provided to the machine control system, so that, in particular, NC control parameters for the selected machining cycle can be optimally selected in step S7A, since the actual position of the cast component is known from the coordinates of the contact point.

[0081] Particularly advantageously, the contact point or the coordinates of the contact point are not only determined by the current position of the tool or the tool tip that comes into contact with the cast component, but also by indirectly determining the original component dimensions of the cast component by taking into account the section of the cast component removed to establish the first contact with the tool. Such indirect determination of the (original) cast component surface enables even more precise machining. For the indirect determination, the removed material on the cast component is determined based on the rotational speed, the material of the cast component, and the feed rate. A contact area can also be calculated by taking into account the penetration depth and the contact area.

[0082] As a final step of the method according to the present invention, the direct machining of the cast component can be carried out based on the adapted machining program or the optimized machining contour according to the detected or calculated contact point.

[0083] In Fig. Figure 4 shows a further illustration of the method according to the invention for machining cast components. In step C1, the start-up cycle is started, for example, manually or automatically integrated into a cycle sequence, for example, in series production.

[0084] In step C2, start parameters are recorded, particularly the machine tool start parameters. These parameters are advantageously recorded individually for each machining operation. The machine tool can have a variety of different sensors that can be used to record the machine tool's start parameters.

[0085] After the machine tool start parameters have been recorded, the probing feed can then be determined in step C3. The probing feed corresponds to the feed at which the tool is moved toward the cast component during the probing process. Depending on the recorded machine tool start parameters, the material of the clamped cast component, the machine dynamics, etc., an optimal probing feed for the approach cycle can preferably be determined automatically. Subsequently, in step C4, the preferred spindle speed for the probing cycle can be determined. Data from a database DB1 can be used to determine the probing feed and spindle speed according to steps C3 and C4 in order to select the most optimal values ​​for the probing cycle.After determining the optimal probing feed and the optimal spindle speed for the probing cycle, the linear axes and the tool rotation are activated so that the tool can move along the predetermined probing device toward the clamped cast component. In step C5, the linear axes and the tool rotation are activated based on the optimal starting parameters determined in the previous steps. Once the contact points have been detected in step C6, the shutdown reaction C7 can be executed. At the same time, the coordinates of the contact points, if multiple contact points are detected, can be transmitted to a database DB2. The database DB2 feeds the machine control system directly to calculate the optimized machining program or optimized machining contour.The database DB1 and the database DB2 are preferably designed independently of each other, wherein the database DB2 is preferably used for the processing of a specific cast component in order to be subsequently emptied again after the cast component has been completely processed, so that efficient control and calculation is enabled.

[0086] Particularly advantageously, the present invention, in a particular embodiment, enables sensorless contact point detection to be provided by utilizing the data or information available at the machine control system (e.g. drive data and / or positioning data), or at least some sensors can be dispensed with.

[0087] In Fig.Figure 5 shows the call of the automatic approach cycle in the sequence of program steps in the NC program in step 4. The spindle shown can be moved along the X, Y, and Z directions in the machine coordinate system. In the program sequence, steps 1 to 3 represent the movement, e.g., a rapid approach movement toward the workpiece, "GO" of the spindle.

[0088] Contact with the workpiece is preferably detected in conjunction with the automatic approach cycle (AA cycle). The automatic approach cycle receives, as input data, a pre-positioning position, a pre-positioning speed, the approach direction to the component, and the approach speed. As an output of the cycle, upon detection of contact with the workpiece, the surface position can advantageously be reported back to the PLC (programmable logic controller) or stored. Alternatively or additionally, the zero point for machining the workpiece can be set at the detected location. The actual workpiece machining can begin directly in step 5, "G1." The machine tool is controlled accordingly via the controller (NC / PLC).

[0089] Examples and embodiments of the present invention, as well as their advantages, have been described in detail above with reference to the accompanying figures. It should be emphasized, however, that the present invention is in no way limited or restricted to the above-described embodiments and their implementation, but rather further encompasses modifications of the embodiments, in particular those encompassed by modifications of the features of the described examples, e.g., by combining one or more of the features of the described examples within the scope of the independent claims.

Claims

[1] Method for machining cast components (WP) on a program-controlled machine tool (100), wherein the machine tool (100) comprises a work spindle (15) rotatably mounted about a spindle axis with a tool interface, and wherein a contact detection means is provided for detecting a contact between a tool (WZ) received in the tool interface and a clamped cast component (WP) wherein the method is a machining manufacturing method for machining with a geometrically defined cutting edge, comprising the following steps: - Pre-positioning (S2) of the tool (WZ) at a distance from the clamped cast component (WP); - Automatic approach (S3A) by moving the rotating tool (WZ) to the cast component (WP); - detecting (S5) a contact point or contact area between the rotating tool (WZ) and the cast component (WP) by detecting at least one detection parameter (EF); - Start (S8) of the machining of the cast component (WP) according to a machining program, wherein the determined contact point or contact area determines at least one machining parameter of the machining program. [2] Method according to claim 1, wherein when the rotating tool (WZ) is moved towards the cast component (WP), the detection parameter (EF) is simultaneously detected, particularly preferably continuously, by means of contact detection means. [3] Method according to at least one of the preceding claims, wherein the contact with the cast component (WP) is determined by evaluating the detection parameter (EF) and / or the temporal course of the detection parameter (EF). [4] Method according to at least one of the preceding claims, wherein the detection parameter (EF) comprises at least one of the following variables: spindle current of the work spindle (15), motor current of the linear axes of the machine tool (100), path and / or force detection of the work spindle (15), detected structure-borne sound, in particular of the work spindle (15), the workpiece holder and / or the tool (WZ). [5] Method according to at least one of the preceding claims, wherein in the step of detecting (S5) a contact point or contact area, the tool (WZ) is switched off as soon as the contact point or contact area has been detected. [6] Method according to at least one of the preceding claims, wherein the machining program comprises a preliminary machining contour of the cast component (WP) and the spatial position and / or the course of the preliminary machining contour is corrected by the determined contact point or contact area to an actual machining contour. [7] Method according to claim 6, wherein the tool (WZ) is immersed in the cast component (WP) outside or inside the preliminary machining contour to reach the contact point or contact area, and wherein the tool (WZ) moves directly to the actual machining contour after reaching the contact point or contact area, preferably in an automated manner. [8] Method according to at least one of the preceding claims, wherein the contact between the rotating tool (WZ) and the cast component (WP) is detected when the absolute value and / or relative value of the detection parameter (EF) exceeds a predetermined limit value, preferably for longer than a specified period of time. [9] Method according to at least one of the preceding claims, wherein the detection parameter (EF) is detected at predetermined times during the movement of the rotating tool (WZ) to the cast component (WP) and the contact between the tool (WZ) and the cast component (WP) is detected by the absolute value and / or the temporal change of the detection parameter (EF). [10] Method according to at least one of the preceding claims, wherein the method is an automatic start-up cycle which enables a probe-independent machining of the cast component (WP) by determining the contact point or contact area, so that preferably an additional measurement of the cast component (WP) before the machining is omitted. [11] Method according to at least one of the preceding claims, wherein the infeed depth of the tool (WZ) for machining the cast component (WP) is determined depending on the determined contact point or contact area. [12] Method according to at least one of the preceding claims, wherein the allowance of the cast component (WP) is determined starting from at least one determined contact point or contact area and based on the allowance the machining parameters of the machining program are defined, preferably automatically and directly in the machine control. [13] Method according to at least one of the preceding claims, wherein the cast component (WP) is held in an indeterminate manner in a clamping device for machining by the machine tool (100) and the determined contact point or contact area determines at least one machining parameter of the machining program during the machining according to a machining contour. [14] Method according to at least one of the preceding claims, wherein in the step of detecting (S5) a contact point or contact area the same tool (WZ) is used as in the step of machining the cast component (WP) according to the machining program. [15] Machine tool (100) for machining, with geometrically certain cutting edge, of cast components (WP), wherein the machine tool (100) has a controller (200) configured to carry out the method according to claim 1, and wherein the detection means comprises a sensor for detecting the motor current of the work spindle (15) and at least the motor current of the work spindle (15) is detected as a detection parameter (EF) and / or wherein the detection means comprises a force measuring device for detecting machining forces or moments between the cast component (WP) and the tool (WZ) on machine tools (100) and / or wherein the detection means comprises a sensor for detecting the current consumption of the drives of the linear axes of the work spindle (15). [16] Machine tool (100) according to claim 15, wherein strain gauges (DMS), in particular semiconductor strain gauges, are provided for force detection on the work spindle (15) and / or on the slide (103, 105) of the machine tool (100). [17] Machine tool (100) according to claim 15 or 16, wherein the tool (WZ) is a turning tool or milling tool and / or after contact detection, the controller (200) is configured to cause a direct shutdown of the tool (WZ) so that the penetration depth is less than 0.1 mm, preferably less than 0.05 mm.

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