METHOD AND DEVICE FOR DETERMINING AN ENERGY-EFFICIENT OPERATING POINT

Abstract

A method of determining an energy-efficient operating point of a machine tool of a machine tool system with which identical workpieces for processing can be supplied to the machine tool sequentially in time. The machine tool has an operating point dependent machine cycle time and an operating point dependent power demand. The machine tool system has at least two machine tools and has a system cycle time, and the machine cycle time is shorter than the system cycle time. The method includes determining the energy-efficient operating point in accordance with a machine cycle time dependent characteristic energy demand function of the machine tool. The characteristic energy demand function represents a machine cycle time dependent energy demand of the machine tool over the system cycle time. A corresponding device and a machine tool system are also described.

Claims

1-15. (canceled)

16. A method of determining an energy-efficient operating point (31, 44, 45, 46) of a machine tool (2, 3, 4) of a machine tool system (1) in which identical workpieces (5) for processing are supplied to the machine tool (2, 3, 4) sequentially in time, the machine tool (2, 3, 4) having an operating point dependent machine cycle time and an operating point dependent power demand, the machine tool system having at least two machine tools (2, 3, 4) and having a system cycle time (t.sub.1), and the machine cycle time is shorter than the system cycle time (t.sub.1), the method comprising: determining the energy-efficient operating point (31, 44, 45, 46) in accordance with a machine cycle time dependent characteristic energy demand function of the machine tool (2, 3, 4), and the characteristic energy demand function representing a machine cycle time dependent energy demand of the machine tool (2, 3, 4) over the system cycle time (t.sub.1).

17. The method according to claim 16, further comprising determining the characteristic energy demand function using a machine cycle time dependent power demand characteristic (30).

18. The method according to claim 17, further comprising defining the characteristic energy demand function (30) as a parabola (40), and the parabola (40) being determined by an equation:)
(t.sub.MTZ)=m.Math.t.sub.MTZ+b).Math.t.sub.MTZP.sub.Wartent.sub.Warten wherein (t.sub.MTZ) is a machine cycle time dependent energy demand of the machine tool (2, 3, 4) over the system cycle time (t.sub.1), factor (m.Math.t.sub.MTZ+b) is the machine cycle time dependent power demand characteristic (30), factor t.sub.MTZ is the machine cycle time, factor t.sub.Warten is a waiting time of the machine tool (2, 3, 4) after an end of the machine cycle time until an end of the system cycle time (t1), and factor P.sub.Warten is a power demand of the machine tool (2, 3, 4) during the waiting time.

19. The method according to claim 18, further comprising determining a point of intersection (42) of the parabola (40) with the system cycle time (t.sub.1), and drawing an imaginary horizontal line (48) through the intersection point (42).

20. The method according to claim 19, further comprising moving the operating point (31, 44, 45, 46) of the machine tool (2, 3, 4) to the intersection point (42) if the machine cycle time dependent energy demand of the machine tool (2, 3, 4) is above the horizontal line (48).

21. The method according to claim 16, further comprising determining a most energy-efficient operating point (31, 44, 45, 46) while retaining the system cycle time (t.sub.1).

22. The method according to claim 16, further comprising determining a most energy-efficient operating point (31, 44, 45, 46) with regard to an electrical energy demand of the machine tool (2, 3, 4).

23. The method according to claim 16, further comprising repeating the method for every machine tool (2, 3, 4) having a machine cycle time shorter than the system cycle time (t.sub.1).

24. The method according to claim 16, further comprising designing the machine tool system (1) to process the workpieces (5) by at least one of grinding, milling and turning.

25. The method according to claim 24, further comprising designing the machine tool system (1) to at least one of grind and mill gearwheel teeth.

26. The method according to claim 24, further comprising determining the operating point (31, 44, 45, 46) by a rough-machining time and a rough-machining power.

27. A device (9, 24) for determining an energy-efficient operating point (31, 44, 45, 46) of a machine tool (2, 3, 4) of a machine tool system (1) with which identical workpieces (5) are supplied to the machine tool (2, 3, 4) sequentially in time for processing, the machine tool system (1) having at least two machine tools (2, 3, 4) and having a system cycle time (t.sub.1), the device (9, 24) comprising: a time determination means (12, 14, 16) for determining an operating point dependent machine cycle time, and a power determination means (13, 15, 17) for determining an operating point dependent power demand of the machine tool (2, 3, 4), and the machine cycle time being shorter than the system cycle time (t.sub.1), energy determination means (18, 21, 22, 23) for determining the energy-efficient operating point (31, 44, 45, 46) in accordance with a machine cycle time dependent characteristic energy demand function (40) of the machine tool (2, 3, 4), and the characteristic energy demand function (40) represents a machine cycle time dependent energy demand of the machine tool (2, 3, 4) over the system cycle time (t.sub.1).

28. The device (9, 24) according to claim 27, wherein the device (9, 24) is structurally and functionally integrated in the machine tool system (1).

29. The device (9, 24) according to claim 27, wherein the device is designed to carry out a method for determining the energy-efficient operating point (31, 44, 45, 46) of the machine tool (2, 3, 4) of the machine tool system (1) including determining the energy-efficient operating point (31, 44, 45, 46) in accordance with the machine cycle time dependent characteristic energy demand function of the machine tool (2, 3, 4), and the characteristic energy demand function representing the machine cycle time dependent energy demand of the machine tool (2, 3, 4) over the system cycle time (t.sub.1).

30. A machine tool system (1) comprising a device (9, 24) for determining an energy-efficient operating point (31, 44, 45, 46) of a machine tool (2, 3, 4) of a machine tool system (1) with which identical workpieces (5) can be supplied to the machine tool (2, 3, 4) sequentially in time for processing, the machine tool system (1) having at least two machine tools (2, 3, 4) and having a system cycle time (t.sub.1), the device (9, 24) comprising a time determination means (12, 14, 16) for determining an operating point dependent machine cycle time, and a power determination means (13, 15, 17) for determining an operating point dependent power demand of the machine tool (2, 3, 4), and the machine cycle time being shorter than the system cycle time (t.sub.1), and the device (9, 24) having energy determination means (18, 21, 22, 23) for determining the energy-efficient operating point (31, 44, 45, 46) in accordance with a machine cycle time dependent characteristic energy demand function (40) of the machine tool (2, 3, 4), and the characteristic energy demand function (40) represents a machine cycle time dependent energy demand of the machine tool (2, 3, 4) over the system cycle time (t.sub.1).

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Below, examples of the invention are explained with reference to the embodiments illustrated in the figures, which show:

[0048] FIG. 1: Schematic representation of a possible form of a machine tool system according to the invention, as an example,

[0049] FIG. 2: Schematic representation of another possible form of a machine tool system according to the invention, as an example,

[0050] FIG. 3: An example of a machine cycle time dependent power demand characteristic,

[0051] FIG. 4: An example of a machine cycle time dependent characteristic energy demand function,

[0052] FIG. 5: An example showing the energy demand of a machine tool over a system cycle time, and

[0053] FIG. 6: An example embodiment of a method according to the invention, in the form of a flow chart.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0054] In all the figures the same objects, functional units and comparable components are denoted by the same indexes. In relation to their technical features these objects, functional units and comparable components are of identical design unless otherwise indicated explicitly or implicitly in the description.

[0055] FIG. 1 schematically shows, as an example, a possible embodiment of a machine tool system 1 according to the invention. The machine tool system 1 shown as an example comprises three machine tools 2, 3 and 4. For its part, the machine tool 2 has a control unit 7. In turn, in this example the control unit 7 comprises time determination means 12, power determination means 13 and an electronic computer unit 21. The machine tool 3 has a control unit 8 which, for its part, comprises time determination means 14, power determination means 15 and an electronic computer unit 22. Finally, the machine tool 4 has a control unit 9. For its part, the control unit 9 comprises time determination means 16, power determination means 17 and an electronic computer unit 23. In this example a device 24 according to the invention for determining an energy-efficient operating point of a machine tool of a machine tool system is structurally and functionally integrated in the control unit 9. In this case the control unit 9 and the device 24 are identical. Correspondingly, the electronic computer unit 23 serves not only to control and regulate the machine tool 4, but in addition serves as a determination means 23 of the device 24. Furthermore, storage means on the data level (not shown) are linked to the electronic computer unit 23. Likewise, the time determination means 16 and the power determination means 17 of the control unit 9 serve as the time determination means 16 and the power determination means 17 of the device 24. By way of data connections 10 the control unit 24 or the device 24 is connected to the control unit 8 and the control unit 7. By way of the data connections 10, the control unit 9 can read out the time determination means 14 and the power determination means 15 of the control unit 8 and the time determination means 12 and power determination means 13 of the control unit 7. The machine tool system 1 shown as an example also comprises a conveyor belt 6 on which workpieces 5 are arranged. The workpieces 5 are the same, i.e. identical workpieces 5, which in this example are in the form of metallic cylinders. In time the workpieces 5 are supplied sequentially to the machine tool 2, the machine tool 3 and the machine tool 4. The machine tool 2 has a machine cycle time of, for example, 20 s. This means that the machine tool 2 needs 20 s to process a workpiece 5. For example, the machine tool 2 performs a milling operation on the workpiece 5 and is operated at maximum power. This means that it is operated at the highest possible operating point 31, 44, 45 and 46. Once the machine tool 2 has finished machining the workpiece 5, the workpiece 5 is conveyed by the conveyor belt 6 to the machine tool 3. The machine tool 3 has for example a machine cycle time of 16 s, which means that the time taken by the machine tool 3 to process a workpiece is 16 s. The machine tool 3 too is operated at maximum power, which corresponds to the highest possible operating point 31, 45, 46. For example, the machine tool 3 is a grinding machine which performs a rough-grinding and a finish-grinding operation on the workpieces 5. The machine tool 4 has for example a machine cycle time of 18 s, meaning that it needs 18 s to process a workpiece 5. In this example the machine tool 4 tool is operated at maximum power, i.e. at the highest possible operating point 44. As an example, the machine tool 4 is a furnace which heat treats the workpieces 5. Since the system cycle time t.sub.1, i.e. the total processing duration for a workpiece 5 by the machine tool system 1, is characterized by the longest machine cycle time or corresponds to it, the system cycle time t.sub.1 in this example amounts to 20 s. Since the control unit 9 comprises the time determination means 16, the power determination means 17 and the determination means 18, as already described it corresponds to the device 24 according to the invention. In this example it also carries out the method according to the invention. During the course of carrying out the method according to the invention, the control unit 9 or the device 24 first varies the operating point 31, 44, 45, 46 of the machine tool 3. Owing to the change of its operating point 31, 44, 45, 46 the power demand of the machine tool 3 and its machine cycle time also change. The operating point 31, 44, 45, 46 is in each case defined by the power demand of the machine tool 3 for a given machine cycle time of the machine tool 3. Thus, the device 24 detects the various operating points 31, 44, 45, 46 of the machine tool 3 and by computation fits a straight line 30 through the various operating points 31, 44, 45, 46, This line 30 represents a machine cycle time dependent power demand characteristic 30. By virtue of the power demand characteristic 30 determined in that way, the device 24 now determines a machine cycle time dependent characteristic energy demand function 40, which is in the form of a parabola. The machine cycle time dependent characteristic energy demand function 40 represents the energy demand of the machine tool 3 as a function of the machine cycle time of the machine tool 3. Furthermore, the device 9 determines a point of intersection 42 on the parabola 40 with the system cycle time t.sub.1. A comparison of the position of the highest possible operating point 31, 45, 46 of the machine tool 3 selected as standard, which is on the parabola 40, with the position of the horizontal line 48, shows for example that the operating point 31, 45, 46 of the machine tool 3 is above the horizontal 48. Accordingly the device 9 adapts the operating point 31, 45, 46 of the machine tool 3 in such manner that it now coincides with the point of intersection 42. Correspondingly, the machine cycle time of the machine tool 3 changes to 20 s. This leads to an energy saving in the machine tool 3. Furthermore, the control unit 9 or device 24 carries out the method according to the invention in an identical manner once more for the machine tool 4. In this case it emerges that a maximum operating point 44 of the machine tool 4 selected as standard is below the horizontal 48 on the parabola. This means that an energy saving in the machine tool 4 is not possible by changing the machine cycle time or changing the operating point 44 of the machine tool 4 without extending the system cycle time t.sub.1. Accordingly, the machine cycle time and the operating point 44 of the machine tool 4 are retained. There is no need to carry out the method according to the invention yet again for the machine tool 2, since the system cycle time t.sub.1 is determined by the machine cycle time of the machine tool 2 or is equal to it. A reduction of the operating point 31, 44, 45, 46 of the machine tool 2 would result in increasing the machine cycle time of the machine tool 2 and would thus also increase the system cycle time t.sub.1. However, since in this example the system cycle time t.sub.1 is kept the same in order not to slow down the production or processing of the workpieces 5, no change is made to the operating point 31, 44, 45, 46, as described. Thus, the machine tools 2, 3 and 4 each operate at an energy-efficient operating point 31, 44, 45, 46 while maintaining the system cycle time t.sub.1 of 20 s, Consequently, the machine tool system 1 also operates at an energy-efficient operating point.

[0056] According to a further example embodiment of a device 24 according to the invention depicted schematically in FIG. 2, the device 24 is structurally independent of the machine tools 2, 3 and 4, In this case the device 24 is connected by means of suitable data connections 10 to the control units 7, 8 and 9 of the machine tools 2, 3 and 4. Although in this example the device 24 is structurally independent of the machine tools 2, 3 and 4, it is partially functionally integrated with them inasmuch as it has access to the time determination means 12, 14 and 16 in the machine tools 2, 3 and 4, respectively, and to the power determination means 13, 15 and 17 in the machine tools 2, 3 and 4, for the purpose of implementing the method according to the invention.

[0057] FIG. 3 shows as an example, and schematically, a machine cycle time dependent power demand characteristic 30 in the form of a straight line 30. The power demand characteristic 30 has been determined in that previously, different operating point 31 of a machine tool 2, 3 or 4 were determined. The power demand characteristic 30 is now plotted on a co-ordinate system having the machine cycle time along its x-axis and the power demand along its y-axis. The power demand characteristic 30 has been determined by adapting, i.e. fitting the line 30 through the various operating points 31. As can be seen, the line 30 slopes downward with increasing machine cycle time, which means that as the machine cycle time increases the power demand during the machine cycle time decreases. Since the line 30 slopes downward with increasing machine cycle time, the gradient of the associated line equation has a negative sign. From the power demand characteristic 30 determined in this way by fitting to the various operating points 31, the known line equation of the form y=b can now be determined by computation. In this example the computed determination of the line equation gives a value of 5 for the gradient m of the power demand characteristic 30, and a value of 8 for the axis intercept b of the power demand characteristic 30. The line equation so defined can now be used to determine the machine cycle time dependent characteristic energy demand function 40.

[0058] FIG. 4 shows as an example a machine cycle time dependent characteristic energy demand function 40 of a machine tool 2, 3 or 4. The characteristic energy demand function 40 describes the energy demand of the machine tool 2, 3 or 4 over the system cycle time t.sub.1, and in this example is in the form of a parabola 40 open downward. This form of the characteristic energy demand function 40 is derived from the basic equation:

(t.sub.MTZ)=(m.Math.t.sub.MTZ+b).Math.t.sub.MTZ+P.sub.Warten.Math.t.sub.Warten,

which is a polynomial of the second order. Owing to the negative gradient of the power demand characteristic 30, the factor m has a negative sign whose result is that the parabola 40 is open downward. The characteristic energy demand function 40 shows clearly that the energy demand of the machine tool 2, 3 or 4 is highest when the power demand and the machine cycle time have medium values, while in contrast, when the power demand is lower and the machine cycle time correspondingly longer, and conversely when the power demand is high and the machine cycle time is correspondingly shorter, energy can be saved. The characteristic energy demand function 40 shown as an example is plotted in a co-ordinate system whose x-axis shows the machine cycle time and whose y-axis shows the energy demand of the machine tool 2, 3 or 4 during the system cycle time t.sub.1. The time-point t.sub.1 is the system cycle time t.sub.1. Starting from t.sub.1, a vertical dot-dash line 41 is drawn upward. The dot-dash line 41 intersects the parabola 40 at an intersection point 42. Starting from the intersection point 42, an imaginary horizontal line 48 is now drawn. The course of the parabola 40 describes for example various operating points 44, 45, 46 of an associated machine tool 2, 3 or 4. In the case of the operating point 44 the machine cycle time is comparatively short. However, since the operating point 44 is below the horizontal line 48, no energy saving is made possible by changing the operating point 44. In the case of the operating point 45, however, an energy saving is made possible by changing the operating point 45 since the operating point 45 is above the horizontal line 48. Thus for example, the operating point 45 is lowered until it coincides with the intersection point 42. This increases the machine cycle time so that it corresponds to the system cycle time t.sub.1 and at the same time leads to a saving of energy. Likewise, it would also be possible to increase the operating point 45 so that it moves to an area of the parabola 40 under a further intersection point 49. That would also result in an energy saving in the machine tool 2, 3 or 4 without influencing the system cycle time t.sub.1 or producing other effects on the machine tool system 1. However, this is only possible when the machine tool 2, 3 or 4, which is working at operating point 45, possesses corresponding power reserves, which is not the case in this example. Likewise, in the case of the operating point 46 an energy saving is possible since the operating point 46 too is above the horizontal line 48. In that the operating point 46 is displaced to the intersection point 42, in this case as well the machine cycle time is increased so that it corresponds to the system cycle time t.sub.1. This too results in a saving of energy, Alternatively, to achieve an energy saving the operating point 46 is also moved to the area of the parabola 40 under the further intersection point 49. In this case, however, in the example considered the power reserves of the machine tools 2, 3 or 4 are not sufficient for such an increase of the operating point 46.

[0059] FIG. 5 shows as an example an energy demand 50 of a machine tool 2, 3 or 4 during a system cycle time t.sub.1. As can be seen, the energy demand consists of the powers 52, 55, 58, 61 required in the various operating modes of a machine tool 2, 3 or 4 and the times 53, 56, 59, 62 spent in the various operating modes. In this example the total energy 50 consists of a partial energy 51 in the processing mode, the partial energy 51 consisting of a power 52 required in the processing mode and the machine cycle time 53. In addition the total energy 50 comprises a partial energy 54 which the machine tool 2, 3 or 4 requires in the secondary mode. The partial energy 54 consists of a power 55 required in the secondary mode and a time 56 spent in the secondary mode. Furthermore the total energy 50 comprises a partial energy 57, which the machine 2, 3 or 4 requires in the idling mode. This partial energy, in turn, consists of the power 58 required in the idling mode and the time 59 spent by the machine tool in the idling mode. Finally, the total energy 50 also comprises the partial energy 60 required by the machine tool 2, 3 or 4 in the standby mode. The partial energy 60 in turn consists of the power 61 required in the standby mode and the time 62 spent by the machine tool in the standby mode.

[0060] FIG. 6 shows as an example an embodiment of a method according to the invention, in the form of a flow chart. In process step 101, identical workpieces 5 are first supplied in a time sequence to a machine tool 2, 3 or 4 of a machine tool system 1 for processing. The machine tool 2, 3 or 4 has an operating point dependent machine cycle time and an operating point dependent power demand. In the next process step 102 the operating point 31, 44, 45 or 46 of the machine tool 2, 3 or 4 is varied, so that in process step 103 the respective machine cycle time and the power demand of the machine tool 2, 3 or 4 at the various operating points 31, 44, 45, 46 can be determined. In the next process step 104 a straight line 30 is now fitted through the various operating points 31 44, 45, 46 determined. This line 30 represents the power demand characteristic. In step 105 the power demand characteristic 30 is used to determine the characteristic energy demand function 40 of the machine tool 2, 3 or 4. In this example the characteristic energy demand function 40 is a parabola 40. In the now following step 106 a point of intersection 42 of the parabola 40 with the system cycle time t.sub.1 is determined. In step 107 an imaginary horizontal line 48 is drawn through the intersection point 42. With reference to the current machine cycle time the actual operating point 31, 44, 45 or 46 of the machine tool 2, 3 or 4 on the parabola 40 is determined in step 108. If the actual operating point 31, 44, 45 or 46 of the machine tool 2, 3 or 4 is below the horizontal 48, in step 109 no savings of energy is possible. The machine tool 2, 3 or 4 is already at an energy-efficient operating point 31, 44, 45 or 46 while the current system cycle time t.sub.1 is maintained. But if the current operating point 31, 44, 45 or 46 is above the horizontal 48 on the parabola 40, then in process step 110 a savings of energy is possible by moving the operating point 31, 44, 45 or 46 to the intersection point 42. This results on the one hand in an increase of the machine cycle time so that it corresponds to the system cycle time t.sub.1, and on the other hand to a savings of energy. The machine tool 2, 3 or 4 is thereby at an energy-efficient operating point 31, 44, 45 or 46.

Indexes

[0061] 1 Machine tool system

[0062] 2 Machine tool

[0063] 3 Machine tool

[0064] 4 Machine tool

[0065] 5 Workpiece

[0066] 6 Conveyor belt

[0067] 7 Control unit of machine tool 2

[0068] 8 Control unit of machine tool 3

[0069] 9 Control unit of machine tool 4

[0070] 10 Data connection

[0071] 11 Data connection

[0072] 12 Time determination means of the control unit 7

[0073] 13 Power determination means of the control unit 7

[0074] 14 Time determination means of the control unit 8

[0075] 15 Power determination means of the control unit 8

[0076] 16 Time determination means of the control unit 9

[0077] 17 Power determination means of the control unit 9

[0078] 18 Determination means

[0079] 21 Electronic computer unit

[0080] 22 Electronic computer unit

[0081] 23 Electronic computer unit

[0082] 24 Device

[0083] 30 Power demand characteristic

[0084] 31 Operating point

[0085] 40 Characteristic energy demand function

[0086] 41 Line representing the system cycle time

[0087] 42 Intersection point

[0088] 44 Operating point

[0089] 45 Operating point

[0090] 46 Operating point

[0091] 48 Horizontal line

[0092] 49 Further intersection point

[0093] 50 Total energy demand over the system cycle time

[0094] 51 Partial energy demand over the machine cycle time

[0095] 52 Power demand over the machine cycle time

[0096] 53 Machine cycle time

[0097] 54 Partial energy demand during the secondary mode time

[0098] 55 Power demand during the secondary mode time

[0099] 56 Secondary mode time

[0100] 57 Partial energy demand during the idling mode time

[0101] 58 Power demand during the idling mode time

[0102] 59 idling mode time

[0103] 60 Partial energy demand during the standby mode time

[0104] 61 Power demand during the standby mode time

[0105] 62 Standby mode time

[0106] 101 Workpieces supplied

[0107] 102 Operating point changed

[0108] 103 Determination of the machine cycle time and the power demand

[0109] 104 Fitting of the power demand characteristic

[0110] 105 Determination of the characteristic energy demand function

[0111] 106 Determination of the first point

[0112] 107 Drawing of a horizontal line through the first point

[0113] 108 Determination of the actual operating point

[0114] 109 Energy saving not possible

[0115] 110 Operating point changed

[0116] t.sub.1 System cycle time