METHOD FOR OPERATING A MACHINE TOOL, AND MACHINE TOOL

Abstract

In a method for operating a machine tool, a machine-specific flow resistance and a respective tool-specific flow resistance are ascertained for various tools. Tool-specific regulator parameters for regulating a pump of a coolant lubricant device are computed on the basis of the machine-specific flow resistance and the tool-specific flow resistance of the tool chucked in a tool spindle. Subsequently, the machine tool is operated using the tool-specific regulator parameters. In this way, a rapid and exact feed of coolant lubricant to the machining point of the respective chucked tool is enabled in a simple and flexible manner.

Claims

1. A method for operating a machine tool, the method comprising the following steps: providing a machine tool, comprising at least one tool spindle, and a coolant lubricant device having a pump for supplying the at least one tool spindle, with a coolant lubricant; chucking a tool in the at least one tool spindle; computing tool-specific regulator parameters for regulating the pump based on a machine-specific flow resistance for the coolant lubricant and a tool-specific flow resistance for the coolant lubricant; and operating the machine tool using the tool-specific regulator parameters.

2. The method as claimed in claim 1, wherein the machine-specific flow resistance is ascertained by operating the machine tool without the tool.

3. The method as claimed in claim 1, wherein the machine-specific flow resistance is ascertained from a pump speed, a pump characteristic curve, and a coolant lubricant pressure.

4. The method as claimed in claim 1, wherein the machine-specific flow resistance is stored in a control device.

5. The method as claimed in claim 1, wherein the tool-specific flow resistance is ascertained by operating the machine tool using the tool chucked in the at least one tool spindle.

6. The method as claimed in claim 1, wherein the tool-specific flow resistance is ascertained from an overall flow resistance and the machine-specific flow resistance.

7. The method as claimed in claim 1, wherein the tool-specific flow resistance is ascertained from a pump speed, a pump characteristic curve, a coolant lubricant pressure, and the machine-specific flow resistance.

8. The method as claimed in claim 1, wherein the tool-specific flow resistance is stored in conjunction with an identification in a control device.

9. The method as claimed in claim 1, wherein at least one of the machine-specific flow resistance and the tool-specific flow resistance is ascertained in dependence on a number of active tool spindles.

10. The method as claimed in claim 1, wherein the tool-specific flow resistance is ascertained using basic regulator parameters for regulating the pump.

11. The method as claimed in claim 1, wherein a coolant lubricant pressure is measured.

12. The method as claimed in claim 1, wherein computation of tool-specific regulator parameters is repeated after a tool change.

13. The method as claimed in claim 1, wherein during operation of the machine tool, a coolant lubricant pressure is regulated by the pump.

14. The method as claimed in claim 1, that wherein during operation of the machine tool, the pump is regulated and after reaching a target range, the pump is controlled.

15. A machine tool, comprising: at least one tool spindle; a coolant lubricant device having a pump for supplying the at least one tool spindle with a coolant lubricant; and a control device configured such that tool-specific regulator parameters for regulating the pump can be computed based on a machine-specific flow resistance) for the coolant lubricant and a tool-specific flow resistance for the coolant lubricant.

16. A manufacturing facility comprising: multiple machine tools and a central control device, each of the machine tools comprising at least one tool spindle, a coolant lubricant device and a control device, the coolant lubricant device having a pump for supplying the at least one tool spindle with a coolant lubricant, the control device being configured such that tool-specific regulator parameters for regulating the pump can be computed based on a machine-specific flow resistance for the coolant lubricant and a tool-specific flow resistant for the coolant lubricant.

17. The method as claimed in claim 8, wherein the tool-specific flow resistance is stored in conjunction with at least one of a tool identification and a tool type identification in the control device.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In the drawings:

[0024] FIG. 1 is a schematic view of a manufacturing facility having multiple machine tools and a central control device;

[0025] FIG. 2 is a schematic view of a coolant lubricant device of one of the machine tools shown in FIG. 1 for supplying two tool spindles with a coolant lubricant;

[0026] FIG. 3 is a schematic view of an adaptive pressure regulation for supplying the tool spindles in FIG. 2 with the coolant lubricant;

[0027] FIG. 4 is a view of a flow chart for ascertaining a machine-specific flow resistance for the design of the pressure regulation in FIG. 3;

[0028] FIG. 5 is a view of a flow chart for ascertaining a tool-specific resistance of the respective tool for the design of the pressure regulation in FIG. 3;

[0029] FIG. 6 is a view of a flow chart for computing tool-specific regulator parameters for the pressure regulation in FIG. 3; and

[0030] FIG. 7 is a view of a time diagram for the pressure regulation in FIG. 3.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0031] A manufacturing facility 1 comprises multiple machine tools 2, 3, 4, which are connected to a central control device 5 via a data transmission network 6. The machine tools 2, 3, 4 each have a local control device 7, 8, 9. The local control devices 7, 8, 9 have a signal connection to the central control device 5 via the data transmission network 6. The manufacturing facility 1 is illustrated in FIG. 1.

[0032] The machine tool 2 comprises two tool spindles 10, 11, which are connected to a coolant lubricant device 13 for the supply with a coolant lubricant 12. The coolant lubricant device 13 comprises a container 14 for accommodating the coolant lubricant 12 and a pump 15 for conveying the coolant lubricant 12 from the container 14 via a feed line 16 to a distributor point 17. The pump 15 is speed-controllable by means of an electric drive motor 18. A coolant lubricant pressure p in the feed line 16 is measurable by means of a pressure measurement sensor 19.

[0033] At the distributor point 17, the feed line 16 divides into a feed line 20, which leads to the first tool spindle 10, and a feed line 21, which leads to the second tool spindle 11. A first valve 22 is arranged in the feed line 20 for switching on the coolant lubricant 12. Accordingly, a second valve 23 is arranged in the feed line 21. In parallel to the first tool spindle 10, the coolant lubricant device 13 forms a first bypass 24, which branches off after the first valve 22 from the feed line 20 at a first branching point 25. A first check valve 26 is arranged between the first branching point 25 and the first valve 22 to prevent the line section between the first valve 22 and the first check valve 26 from running empty via the first tool spindle 10 or the first bypass 24. In a corresponding manner, a second bypass 27 is arranged in parallel to the first tool spindle 11 proceeding from a second branching point 28. Moreover, a second check valve 29 is arranged in a corresponding manner between the second branching point 28 and the second valve 23.

[0034] The measured coolant lubricant pressure p is provided via a signal line to the control device 7. The drive motor 18 comprises, for example, a speed measurement sensor 30 for measuring a pump speed n, which is provided via a signal line to the control device 7. However, the pump speed n can also be ascertained without a sensor via an inverter and provided to the control device 7. In addition, the control device 7 has a signal connection to the drive motor 18, the valves 22, 23, the tool spindles 10, 11, and the bypasses 24, 27.

[0035] The machine tool 2 is additionally constructed in a routine manner. To provide various tools W.sub.1 to W.sub.4, the machine tool 2 has a tool magazine 31, in which the tools W.sub.1 to W.sub.4 are kept ready with an associated identification I.sub.1 to I.sub.4. The tools W.sub.1 to W.sub.4 are fastened, for example, in associated tool holders, by means of which the tools W.sub.1 to W.sub.4 can be chucked in tool receptacles of the tool spindles 10, 11 in a typical manner. In addition, empty tool holders H.sub.0 having the identification I.sub.0 are kept ready in the tool magazine 31. The tool holders H.sub.0 have, for example, a minimum diameter of 30 mm.

[0036] The machine tools 3, 4 are structurally equivalent to and/or different from the machine tool 2. The machine tools 3, 4 comprise coolant lubricant devices corresponding to the coolant lubricant device 13. The coolant lubricant devices are used, depending on the construction of the machine tools 3, 4, to supply one tool spindle and/or to supply two tool spindles.

[0037] An adaptive pressure regulation 32 of the machine tool 2 is described hereafter. An adaptive pressure regulator 33 is implemented in the control device 7, which has as input variables a target pressure p.sub.S, the measured coolant lubricant pressure p, a number N of the active tool spindles 10, 11, a machine-specific flow resistance R.sub.M(N), and a tool-specific flow resistance R.sub.W(W). The machine-specific flow resistance R.sub.M(N) and the tool-specific flow resistance R.sub.W(W) are initially unknown. In addition, the pressure regulator 33 has as an input variable a pump characteristic curve K, which is known. The pump characteristic curve K is provided, for example, by a pump producer.

[0038] For the parameterization of the adaptive pressure regulation 32, firstly the machine-specific flow resistance R.sub.M(N) is ascertained. This is illustrated in FIG. 4. For this purpose, a program sequence for ascertaining the machine-specific flow resistance R.sub.M(N) is selected by means of the control device 7. In a first step S.sub.11, the empty tool holders H.sub.0 are chucked in the tool spindles 10, 11 from the tool magazine 31. For the number of active tool spindles 10, 11, initially N=1 applies, which means that, for example, only the tool spindle 10 or only the tool spindle 11 is active. For this purpose, one of the valves 22, 23 is open and the corresponding other valve 22, 23 is closed.

[0039] Subsequently, the pressure regulator 33 is parameterized in step S.sub.12 using basic regulator parameters P.sub.0, which ensure a stable pressure regulation. A target pressure p.sub.S is predetermined for the pressure regulator 33, which is converted by the pressure regulator 33 into a target speed n.sub.S for the pump 15 or the drive motor 18, respectively. In subsequent operation of the machine tool 2, the speed n and the coolant lubricant pressure p are measured and acquired in the control device 7. The drive motor 18 comprises a subordinate speed control loop (not shown in greater detail in FIG. 3) for regulating the target pressure p.sub.S. During the ascertainment of the machine-specific flow resistance R.sub.M, the pump 15 is operated, for example, at maximum speed.

[0040] In a subsequent step S.sub.13, the control device 7 computes the machine-specific flow resistance R.sub.M(N) for the number N=1 from the measured coolant lubricant pressure p, the measured pump speed n, and the pump characteristic curve K. The pump characteristic curve K characterizes, for example, a volume flow and/or a generated pump pressure in dependence on the pump speed n.

[0041] The ascertained machine-specific flow resistance R.sub.M(N) is subsequently stored in a step S.sub.14 in the machine data of the control device 7 and is available in further operation of the machine tool 2.

[0042] Steps S.sub.11 to S.sub.14 are subsequently repeatedif necessaryhaving the open valves 22, 23 for the number N=2. Therefore, the machine-specific flow resistance R.sub.M(N) is ascertained for two active tool spindles 10, 11 and stored in the control device 7.

[0043] The machine-specific flow resistance R.sub.M(N) exclusively characterizes the flow resistance of the machine installation in dependence on the number N of the active tool spindles 10, 11. The machine-specific flow resistance R.sub.M(N) is independent of a tool chucked in the respective tool spindle 10, 11.

[0044] The ascertainment of the tool-specific flow resistance R.sub.R(W.sub.1) is described hereafter on the basis of FIG. 5. For this purpose, a program implemented in the control device 7 is started, which carries out a tool change in a step S.sub.21, so that the tool W.sub.1 having the identification I.sub.1 is chucked in the first tool spindle 10. The tool-specific flow resistance R.sub.R(W.sub.1) is ascertained automatically during the processing sequence if a tool-specific flow resistance R.sub.W(W.sub.1) is not stored for the tool W.sub.1. A special measurement program is not required or started. The first valve 22 is opened, while in contrast the second valve 23 is closed, so that the machine tool 2 is operated using the active tool spindle 10. Alternatively or additionally, a tool W.sub.1 can be chucked in the second tool spindle 11 and the machine tool 2 can be operated using one active tool spindle 11 or using two active tool spindles 10, 11. The number N is predetermined for the control device 7.

[0045] Subsequently, in a step S.sub.22, it is checked on the basis of the identification I.sub.1 in the control device 7 whether a tool-specific flow resistance R.sub.W(W.sub.1) is already stored for the tool W.sub.1. If a tool-specific flow resistance R.sub.W(W.sub.1) is already stored, it is read out in a step S.sub.23 and used for the following computations.

[0046] If a tool-specific flow resistance R.sub.W(W.sub.1) is not stored, thus, in a following step S.sub.24, the pressure regulator 33 is parameterized using basic regulator parameters P.sub.0. A target pressure p.sub.S and the number N of active tool spindles 10, 11 is specified to the pressure regulator 33. During the subsequent operation in a test of the machine tool 2, the coolant lubricant pressure p is measured and the target pressure p.sub.S is adjusted by means of the pressure regulator 33. For this purpose the pressure regulator 33 specifies the pump speed n.sub.S, which is regulated by means of the electric drive motor 18. The pump speed n is measured and fed to a subordinate speed control loop.

[0047] In a following step S.sub.25, the tool-specific flow resistance R.sub.W(W.sub.1) is computed for the tool W.sub.1. For this purpose, firstly an overall flow resistance R.sub.G is computed from the measured coolant lubricant pressure p, the measured pump speed n, and the pump characteristic curve K. Subsequently, the tool-specific flow resistance R.sub.W(W.sub.1) is computed from the computed overall flow resistance R.sub.G, by the machine-specific flow resistance R.sub.M(N) being subtracted from the overall flow resistance R.sub.G. Depending on the number N of active tool spindles 10, 11, the ascertained machine-specific flow resistance R.sub.M(N) for one active tool spindle or the ascertained machine-specific flow resistance R.sub.M(N) for two active tool spindles 10, 11 is subtracted from the overall flow resistance R.sub.G.

[0048] Subsequently, in a step S.sub.26, the computed tool-specific flow resistance R.sub.W(W.sub.1) for the tool W.sub.1 is stored together with the identification I.sub.1 in the tool data of the control device 7.

[0049] Steps S.sub.21 to S.sub.26 are repeated for the further tools W.sub.2 to W.sub.4 and the associated identifications I.sub.2 to I.sub.4. Alternatively, after the ascertainment of the tool-specific flow resistance R.sub.W(W.sub.1), it is possible to begin with the machining of a workpiece by means of the tool W.sub.1 and to wait for the ascertainment of the respective tool-specific flow resistance R.sub.W(W.sub.2) to R.sub.W(W.sub.4) until a machining is provided using the respective tool W.sub.2 to W.sub.4.

[0050] The identifications I.sub.1 to I.sub.4 are, for example, a tool identification of the special tool W.sub.1 to W.sub.4 and/or a tool type identification of tools W.sub.1 to W.sub.4, which are associated with the same tool type and therefore have corresponding tool-specific flow resistances R.sub.W(W).

[0051] After the ascertainment of the machine-specific flow resistance R.sub.M(N) and the tool-specific flow resistance R.sub.W(W.sub.1), the machine tool 2 is operated using the tool W.sub.1 and an adaptive pressure regulation 32. This is illustrated in FIG. 6. Firstly, in a step S.sub.31, the machining program or the NC program is loaded into the control device 7 for this purpose. The machining program contains switching on and off points in time of the coolant lubricant device 13 and the target pressure p.sub.S.

[0052] On the basis of the identification I.sub.1, the stored tool-specific flow resistance R.sub.W(W.sub.1) of the tool W.sub.1 is read out from the control device 7 in a step S.sub.32.

[0053] In a subsequent step S.sub.33, the target speed n.sub.S of the pump 15 is computed from the target pressure p.sub.S and the pump characteristic curve K, which is specified to the subordinate speed control loop as a pilot control value or starting speed. The starting speed is computed in dependence on the number N, the associated machine-specific flow resistance R.sub.M(N), the tool-specific flow resistance R.sub.W(W.sub.1) of the tool W.sub.1, and the target pressure p.sub.S.

[0054] In a subsequent step S.sub.34, tool-specific regulator parameters P.sub.W are computed, using which the pressure regulator 33 is parameterized. The pressure regulator 33 is, for example, a PI regulator or PID regulator. The regulator parameters P.sub.W are dependent on the selected machine installation or the number N of active tool spindles 10, 11 and the respective utilized tool W.sub.1 to W.sub.4. Accordingly, the pressure regulator 33 is parameterized specifically to the machine and tool, so that the pressure regulation 32 is adaptive.

[0055] The tool-specific regulator parameters P.sub.W can be stored for the respective selected special machine and tool constellation, so that they are available for a subsequent operation of the machine tool 2 using the same machine and tool constellation. Alternatively, steps S.sub.31 to S.sub.34 can be repeated after each tool change and/or after each change of the number N of active tool spindles 10, 11, so that a storage is not required.

[0056] In a subsequent step S.sub.35, the pump 15 is started by means of the drive motor 18. The target speed n.sub.S is specified in the form of a jump function as a pilot control value. The machine tool 2 is operated using the tool-specific regulator parameters P.sub.W and the tool W.sub.1.

[0057] Subsequently, in a step S.sub.36, the pump speed n and the coolant lubricant pressure p are elevated by means of the adaptive pressure regulation 32 until, for example, the pump speed n and/or the coolant lubricant pressure p reach(es) a target range . The specified target pressure p.sub.S is regulated by means of the adaptive pressure regulator 33 and a subordinate speed control loop.

[0058] In a step S.sub.37, it is regularly queried whether the target range is reached. If the target range is not yet reached, the pressure regulation 32 is thus still active. In contrast, if the target range is reached, the pressure regulation 32 is thus switched off in a step S.sub.38 and the achieved speed n of the pump 15 is frozen. The pump 15 is thus operated further in a controlled manner.

[0059] The function of the adaptive pressure regulation 32 is illustrated in FIG. 7. At the point in time t.sub.1, the target pressure p.sub.S and the target speed n.sub.S are specified as a jump function. The target speed n.sub.S is specified as a pilot control value or computed starting speed. Subsequently, the drive motor 18 and/or the pump 15 accelerates at maximum torque to the target speed n.sub.S. At the point in time t.sub.2, the measured pump speed n reaches the target speed n.sub.S. The pressure regulator 33 corrects the pump speed n until it is in the target range . This is the case at the point in time t.sub.3. The pump speed n is subsequently frozen. The pump 15 is thus merely still controlled. In this way, negative influences on the pressure regulation 32 as a result of dynamic pressure during the workpiece machining are avoided.

[0060] The tool-specific flow resistances R.sub.W ascertained by the machine tools 2, 3, 4 are transmitted at regular time intervals to the central control device 5 and stored therein as a tool catalog. The tool-specific flow resistances R.sub.W stored in the central control device 5 are in turn transmitted to the local control devices 7, 8, 9, so that the local control devices 7, 8, 9 synchronize with one another. In this manner, each tool-specific flow resistance R.sub.W only has to be ascertained once in the manufacturing facility 1.

[0061] The adaptive coolant lubricant pressure regulation 32 enables, in a simple and flexible manner, a rapid and exact feed of coolant lubricant 12 to the machining points of changing tools W.sub.1 to W.sub.4. The control loops having the drive motor 18, the pump 15, the machine installation, and the tool spindle 10 and/or 11 and also a respective tool W.sub.1 to W.sub.4 chucked therein are automatically measured. Basic regulator parameters P.sub.0 are used for this purpose. Associated tool-specific flow resistances R.sub.W can be computed from the resulting coolant lubricant pressures p and pump speeds n for the respective tool W.sub.1 to W.sub.4 and tool-specific regulator parameters P.sub.W for the respective tool W.sub.1 to W.sub.4 can be computed together with a machine-specific flow resistance R.sub.M. The tool-specific flow resistances R.sub.W for the respective tool W.sub.1 to W.sub.4 are stored in the region of the tool data of the local control device 7, 8, 9 of the respective machine tool 2, 3, 4. The adaptive pressure regulation 32 enables a rapid and stable provision of the coolant lubricant 12 in this way. The regulator result is substantially independent in this case of the utilized tool W.sub.1 to W.sub.4. The machine-specific flow resistance R.sub.M is ascertained in dependence on the number N of active tool spindles 10, 11, so that the tool-specific regulator parameters P.sub.W are computed in dependence on a one-spindle or two-spindle machining, respectively. The adaptive pressure regulation 32 thus adjusts itself to the fluid-dynamic properties of the respective machine tool 2, 3, 4 and the respective utilized tool W.sub.1 to W.sub.4. The measurement of the flow resistances R.sub.M and R.sub.W takes place automatically. In this way, shorter startup times can be implemented. Tools used for the first time can be integrated without problems into the manufacturing facility 1. A rapid provision of the coolant lubricant 12 without or without a noticeable overshoot in the pressure regulation is enabled by the adaptive pressure regulation 32. This protects the drive motor 18 and/or the pump 15. The flow resistances R.sub.M and/or R.sub.W are computed via the delivery quantity of the pump 15, i.e., the pump speed n and the pump characteristic curve K and the pressure loss up to the pressure measurement sensor 19. Basic regulator parameters P.sub.0 for ascertaining the respective tool-specific flow resistance R.sub.W can be computed from the ascertained specific flow resistance R.sub.M.

[0062] While specific embodiments of the invention have been shown and described in detail to illustrate the application of the principles of the invention, it will be understood that the invention may be embodied otherwise without departing from such principles.